DEVELOPMENT OF LOCALLY AVAILABLE SANDWICH COMPOSITE FOR SUSTAINABLE LIGHTWEIGHT STRUCTURES By Areej Thabit Al m alkawi A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of 20 20 ABSTRACT DEVELOPMENT OF LOCALLY AVAILABLE SANDWICH COMPOSITE F OR SUSTAINABLE LIGHTWEIGHT STRUCTURES By Areej Thabit Al m alkawi Aerated slurry - infiltrated chicken mesh was evaluated as a lightweight and structurally resilient material for building construction. Aerated slurry with relatively low structural qualities was shown to perform favorably when used as a matrix with chicken mesh reinforcement in structural application s. The high specific surface area of chicken mesh and the close spacing of its wires (when used at 2 - 4% volume fraction) effectively enhance the mechanical performance and dimensional stability of the aerated slurry. The chicken mesh structural behavior al so benefits significantly from embedment in the aerated slurry , which mitigates the reorientation tendency of the chicken mesh wires under tension. This effect enables mobilization of the tensile load - carrying capacity of the wires in chicken mesh at struc turally viable deformations. A comprehensive experimental program was undertaken at materials and structures levels in order to develop aerated slurry - infiltrated chicken mesh materials and structural systems with a desired balan ce of strength, ductility and hysteretic energy dissipation capacity. The bulk density of the aerated slurry and the chicken mesh volume fraction were some key variables in the design of the new (composite) building material. With proper selection of these variables, the synergistic actions of the aerated slurry and the chicken mesh in the context of the composite material were confirmed. Empirical models were developed for the mechanical performance of this composite material . In the future, the structural performance of this composite material may be verified by constructing a full - scale building system and conducting shaking table tests . iv To my father Dr. Thabit Malkawi to whom I promised to dedicate my doctorate journey before he left this world v ACKNOWLEDGEMENTS Venture this PhD has been a truly life - changing milestone for me and it would not have been possible to go through without the support and guidance that I received from many people. I would like to express sincere gratitude for Dr. Katy Colbry, I appreciate all her contributions of time, support , and funding to make my Ph.D. experience positive and productive. I gratefully acknowledge the members of my Ph.D. committee Dr. Thomas Voice, Dr. Neeraj Buch, Dr. Thomas Wolff, for their time and valuable feedback on this dissertation. I greatly appreciate the support received from Office for International Students and Scholars (OISS). I am especially grateful for Brooke Stokdyk , Ismail Adawe for all support in numerous ways during various stages of my PhD. I would also like to say a heartfelt for my daughter Sophia , her existence in my life made me stronger, better and more fulfilled than I could have ever expected . vi TABLE OF CONTENTS LIST OF TABLES ................................ ................................ ................................ ...................... x LIST OF FIGURES ................................ ................................ ................................ ................... xii CHAPTER 1: INTRODUCTION ................................ ................................ ................................ .. 1 1.1 General ................................ ................................ ................................ .......................... 1 1.2 Summary of Research ................................ ................................ ................................ ... 2 1.2.1 Physio - Microstructural Properties of A erated Cement Slurry for Lightweight Structures ................................ ................................ ................................ ................... 2 1.2.2 Mechanical Properties of Aerated Slurry - Infiltrated Chicken Mesh ................ 3 1.2.3 Behavior of a Lightweight Frame Made with Aerated Slurry - Infiltrated Chicken Mesh Under Cyclic Lateral Loading ................................ .............................. 3 1.2.4 Evaluation of the Energy - Efficiency of an Aerated Slurry - Infiltrated Mesh Building System with Biomass - Based Insulation ................................ ....................... 4 1.2.5 Aerated Cement Slurry and Controlling Fungal Growth of Low - Cost Biomass - Based Insulation Materials ................................ ................................ ......................... 5 1.2.6 One - Part Alkali Activated Cement Based Volcanic Pumice .............................. 6 1.2.7 Potential of Using Industrial Wastes For Production Of Geopolymer Binder As Green Construc tion Materials ................................ ................................ ................... 6 CHAPTER 2: PHYSIO - MICROSTRUCTURAL PROPERTIES OF AERATED CEMENT SLURRY FOR LIGHTWEIGHT STRUCTURES ................................ ................................ ................................ ... 8 2.1 Introduction ................................ ................................ ................................ .................. 8 2.2 Materials and Methods ................................ ................................ ............................... 10 2.3 Experimental Results and Discussion ................................ ................................ .......... 18 2.3.1 Compressive strength ................................ ................................ ..................... 18 2.3.2 Sorptivity ................................ ................................ ................................ ......... 18 2.3.3 Optic Microscope ................................ ................................ ............................ 21 2.3.4 SEM Observations ................................ ................................ ........................... 23 2.3.5 Ultrasound Pulse Velocity ................................ ................................ ............... 25 2.3.6 Thermal Conductivity ................................ ................................ ...................... 26 2.4 Conclusions ................................ ................................ ................................ ................. 27 2.5 Acknowledgment s ................................ ................................ ................................ ....... 28 REFERENCES ................................ ................................ ................................ ........................ 29 CHAPTER 3: MECHANICAL PROPERTIES OF AERATED SLURRY - INFILTRATED CHICKEN MESH .. 34 3.1 Introduction ................................ ................................ ................................ ................ 34 3.2 Experimental Program ................................ ................................ ................................ 36 3.2.1 Materials ................................ ................................ ................................ ......... 36 3.2.1.1 Aerated Slurry ................................ ................................ ..................... 36 vii 3.2.1.2 Chicken Mesh ................................ ................................ ...................... 37 3.3 Experimental Methods ................................ ................................ ............................... 38 3.3. 1 Tests performed on aerated slurry - infiltrated chicken mesh ......................... 40 3.3. 1 .1 Compression ................................ ................................ ....................... 40 3.3. 1 .2 Tension ................................ ................................ ................................ 41 3.3. 1 .3 Flexure ................................ ................................ ................................ . 41 3.4 Test Results and Discussion ................................ ................................ ........................ 42 3.4.1 Compressive strength and bulk density of aerated slurry .............................. 42 3.4.2 Compressive behavior of the aerated slurry - infiltrated chicken mesh .......... 43 3.4.3 Tensile behavior of aerated slurry - infiltrated chicken mesh .......................... 44 3.4.4 Flexural performance ................................ ................................ ...................... 48 3.4.5 Analysis of aerated slurry - infiltrated chicken mesh ................................ ....... 49 3.5 Conclusions ................................ ................................ ................................ ................. 52 3.6 Acknowledgements ................................ ................................ ................................ ..... 53 REFERENCES ................................ ................................ ................................ ........................ 54 CHAPTER 4: BEHAVIOR OF A LIGHTWEIGHT FRAME MADE WITH AERATED SLURRY - INFILTRATED CHICKEN MESH UNDER CYCLIC LATERAL LOADING ................................ ........... 57 4.1 Introduction ................................ ................................ ................................ ................ 57 4.2 Materials and Methods ................................ ................................ ............................... 59 4.2.1 Aerated Slurry ................................ ................................ ................................ . 59 4.2.2 Chicken Mesh ................................ ................................ ................................ .. 60 4.2.3 Aerated Slurry - Infiltrated Chicken Mesh ................................ ........................ 61 4.2.4 Aerated Slurry Infiltrated Chicken Mesh Frame ................................ ............. 62 4.2.5 Cyclic Testing ................................ ................................ ................................ ... 65 4.3 Test Results and Discussion ................................ ................................ ........................ 68 4.3.1 Plastic - Hinge approach ................................ ................................ ..................... 68 4.3.2 Hysteretic load - deflection curve ................................ ................................ ...... 68 4.3.3 Equivalent Energy Elastic Plastic (EEEP) curve ................................ ................. 70 4.3.4 Elastic Stiffness ................................ ................................ ................................ . 71 4.3.5 Failure load ................................ ................................ ................................ ....... 73 4.3.6 Yield load and yield displacement ................................ ................................ .... 74 4.3.7 Ductility ................................ ................................ ................................ ............ 75 4.4 Conclusions ................................ ................................ ................................ ................. 76 REFERENCES ................................ ................................ ................................ ........................ 78 CHAPTER 5: EVALUATION OF THE ENERGY - EFFICIENCY OF AN AERATED SLURRY - INFILTRATED MESH BUILDING SYSTEM WITH BIOMASS - BASED INSULATION ................................ ............. 82 5.1 Introduction ................................ ................................ ................................ ................ 82 5.2 Experimental Evaluation of Insulation Qualities ................................ ......................... 84 5.2.1 Materials ................................ ................................ ................................ ........... 84 5.2.1.1 Aerated Slurry ................................ ................................ ..................... 84 5.2.2 Biomass - Based Insulation Materials ................................ ................................ 85 5.2.2.1 Ground Wood Insulation ................................ ................................ .... 85 viii 5.2.2.2 Shredded Straw Insulation ................................ ................................ 87 5.2.2.3 Commercially Available Cellulose ................................ ..................... 88 5.2.3 Thermal Conductivity Test Method ................................ ................................ .. 89 5.2.4 Thermal Conductivity Test Results ................................ ................................ ... 90 5.3 Thermal Simulation and Design of the Building System ................................ ........... 94 5.3.1 Thermal Simulation of the Building System ................................ .................... 95 5.4 Results and Discussion ................................ ................................ .............................. 97 5.4.1 Energy Consumption ................................ ................................ ........................ 97 5.4.2 Optimization of the Wall Insulation Condition ................................ ................ 99 5.4.3 Comparis on with a Conventional Wood Building ................................ .......... 100 5.5 Conclusions ................................ ................................ ................................ .............. 103 REFERENCES ................................ ................................ ................................ ...................... 105 CHAPTER 6: AERATED CEMENT SLURRY AND CONTROLLING FUNGAL GROWTH OF LOW - COST BIOMASS - BAS ED INSULATION MATERIALS ................................ ................................ ......... 109 6.1 Introduction ................................ ................................ ................................ ............. 109 6.2 Materials ................................ ................................ ................................ .................. 112 6.2.1 Wood Particles ................................ ................................ .............................. 112 6.2.2 Wood Chips ................................ ................................ ................................ ... 113 6.2.3 Shredded Straw ................................ ................................ ............................. 114 6.2.4 Treatment of Biomass with Aerated Slurry ................................ .................. 114 6.3 Methods ................................ ................................ ................................ .................. 116 6.3.1 Water - Holding Capacity ................................ ................................ ................ 116 6.3.2 Equilibrium Moisture Content ................................ ................................ ...... 116 6.3.3 Artificial Inoculation ................................ ................................ ...................... 117 6.4 Results and Discussion ................................ ................................ ............................ 120 6.4.1 Water uptake ................................ ................................ ................................ 120 6.4.2 Visual and Microscopic Observations ................................ ........................... 121 6.4.3 Optical microscope ................................ ................................ ....................... 122 6.4.4 Natural Inoculation ................................ ................................ ....................... 123 6.5 Conclusions ................................ ................................ ................................ .............. 124 REFERENCES ................................ ................................ ................................ ...................... 126 CHAPTER 7: ONE - PART ALKALI ACTIVATED CEMENT BASED VOLCANIC PUMICE .................. 131 7.1 Introduction ................................ ................................ ................................ ............. 131 7.2 Experimental Program ................................ ................................ ............................. 133 7.2.1 Materials ................................ ................................ ................................ ....... 133 7.2.2 Formulations of Raw Materials and Their Processing into Hydraulic cements ................................ ................................ ................................ ................................ 134 7.2. 3 Characterization Methods ................................ ................................ ........... 135 7.3 Test Results and Discussion ................................ ................................ ..................... 137 7.3.1 Particle Size Distribution ................................ ................................ ............... 137 7.3.2 Chemical Composition ................................ ................................ .................. 138 7.3.3 Compressive Strength of Mortar ................................ ................................ .. 138 ix 7.3.4 Mineralogy ................................ ................................ ................................ .... 139 7.3.5 Chemical Environment ................................ ................................ .................. 140 7.3.6 Microstructural Characteristics ................................ ................................ .... 142 7.3.7 Thermogravimetric Analysis ................................ ................................ ......... 144 7.3.8 Isothermal conduction calorimetry measurement ................................ ....... 146 7. 4 Conclusion ................................ ................................ ................................ .............. 149 REFERENCES ................................ ................................ ................................ ...................... 151 CHAPTER 8: POTENTIAL OF USING INDUSTRIAL WASTES FOR PRODUCTION OF GEOPOLYMER BINDER AS GREEN CONSTRUCTION MATERIALS ................................ ................................ . 158 8.1 Introduction ................................ ................................ ................................ ........... 158 8.2 Material and Methods ................................ ................................ ........................... 162 8.2.1 Materials ................................ ................................ ................................ ....... 162 8.2.2 Particle Size Distribution ................................ ................................ ............... 162 8.2.3 Chemical Composition ................................ ................................ .................. 163 8.3 Methods ................................ ................................ ................................ ................. 164 8.3.1 Processing of Raw Materials ................................ ................................ ......... 164 8.3.2 Characterization Methods ................................ ................................ ............ 165 8.4 Test Results and Discussion ................................ ................................ ................... 166 8.4.1 Chemical Bond Environment ................................ ................................ ........ 166 8.4.2 SEM Observations ................................ ................................ ......................... 167 8.4.3 Mineralogy ................................ ................................ ................................ .... 168 8.4.4 Compressive Strength ................................ ................................ ................... 169 8.4.4.1 Effect of Alkali Source ................................ ................................ ....... 169 8. 4.5 Effects of the Relative Quantities of Rice Husk Ash and Municipal Solid Waste Ash on the Resulting Hydraulic Geopolymer Binder Performance ....................... 171 8.4. 6 Toxicity tests ................................ ................................ ................................ . 174 8. 5 Conclusions ................................ ................................ ................................ ............ 176 8. 6 Acknowledgements ................................ ................................ ................................ 177 REFERENCES ................................ ................................ ................................ ...................... 178 CHAPTER 9 : CONCLUDING DISCUSSION ................................ ................................ .............. 185 x LIST OF TABLES Table 1. The aerated slurry mixes proportions considered in this investigation. ........................ 14 Table 2. Mix designs and performance characteristics of the aerated slurry. ............................. 18 Table 3. Sorption r ates and densities of slurries prepared with different dosages of the foaming agent. ................................ ................................ ................................ ................................ ... 20 Table 4. The aerated slurry mix proportions ................................ ................................ ................ 39 Table 5. A summary presentation of the tensile strength test results for slurry - infiltrated chicken mesh sheets with different slurry densities and number of chicken mesh layers. 47 Table 6. Aerated slurry - infiltrated chicken mesh sheet and beam dimensions, reinforcement and loading conditions, and test results versus predicted values. ................................ ...... 52 Table 7. Test protocol for evaluation of the frame performance under cyclic lateral loads ....... 67 Table 8. Failure load and displacement at failure of aerated slurry - infiltrated chicken mesh frame versus alternative lateral load - carrying systems of comparable geometric attributes ................................ ................................ ................................ ................................ .............. 74 Table 9. The parameters required for calculation of the yield load (and the calculated value of yield load) ................................ ................................ ................................ ............................. 74 Table 10. The design factors used in simulation of the building system ................................ ...... 96 Table 11. Thermal properties of aerated slurry, biomass insulation, and plywood. .................... 97 Table 12. Thermal conductivities of fine wood particles and wood chips. ................................ 116 Table 13. Results of the visual examination of fungal growth on untreated and treated biomass insulation materials over time in different moisture conditions (ASTM C1338): ambient moisture (A mb), simulated rain (Rain), and water wetted to water holding capacity ..... 122 Table 14. Some properties of the pumice used as raw material (aluminosilicate precursor) in synthesis of one - part hydraulic cement. ................................ ................................ ........... 134 Table 15. Mechanochemical processing (milling) conditions of the heat - treated blends of raw materials (three sizes of steel balls were used in equal weights). ................................ .... 135 Table 16. The formulations of raw materials considered for synthesis hydraulic cements. ...... 136 xi Table 17. Chemical composition of the pumice used in the experimental work ....................... 138 Table 18. Chemical composition of coal fly ash, wt.%. ................................ ............................... 163 Table 19. The formulations (by weight) of raw materials considered for synthesis of hydraulic binders with different sources of alkalis ................................ ................................ ............ 164 Table 20. The formulations of hydraulic binders considered for evaluation of the effects of the relative proportions of rice husk a sh and the municipal solid waste ash on the compressive ................................ ................................ ................................ ................................ ............ 164 xii LIST OF FIGURES Figure 1. Saponin molecule extracted from sisal waste . ................................ ............................ 11 Figure 2. Interaction between air bubbles and cement particles . ................................ ............. 12 Fi gure 3. Foam generation in water via high - speed mixing. ................................ ....................... 13 Figure 4. Aerated slurry specimens. ................................ ................................ ............................ 14 Figure 5. Sorptivity test setup. ................................ ................................ ................................ ..... 15 Figure 6. Ultrasound pulse velocity test setup. ................................ ................................ .......... 16 Figure 7. Thermal conductivity testing diagram and test setup. ................................ ................. 17 Figure 8. Capillary sorption of ae rated slurries versus the square root of time. ........................ 20 Figure 9. Sorptivity of non - aerated versus aerated slurries. ................................ ....................... 21 Figure 10. Sorption paths into non - aerated and aerated slurries ................................ ............... 21 Figure 11. Optical microscope images of sections of aera ted slurries with different dosages of the foaming agent (saponin). ................................ ................................ ............................... 22 Figure 12. Optical microscope images of sections of aerated slurries with different dosages of the foaming agent (saponin) ................................ ................................ ................................ 22 Figure 13. SEM images of the fractured surfaces of foam cements made from slurries with a density of 0.75 (left) and 1.3 g/cm3 (right). ................................ ................................ ........ 24 Figure 14. UPV time - history for aerated slurries of different densities. ................................ ..... 25 Figure 15. Reproducibility check on three UPV tests for the same mix design (Mix 13) ............ 26 Figure 16. Thermal conductivity of aerated slurries v ersus their density. ................................ .. 26 Figure 17. Preparation of foamed water by stirring the mixing water incorporating the foaming agent. ................................ ................................ ................................ ................................ ... 37 Figure 18. The chicken mesh used in the experimental program. ................................ .............. 38 Fig ure 19. Aerated slurry - infiltrated chicken mesh compression test specimen ........................ 40 xiii Figure 20. Tension test setup. ................................ ................................ ................................ ...... 41 Figure 21. Flexure test setup. ................................ ................................ ................................ ...... 42 Figure 22. Compressive strength and bulk density test results for different aerated slurries . .. 43 Figure 23. A typical compressive stress - deflection behavior of aerated slurry - infiltrated chicken mesh. ................................ ................................ ................................ ................................ .... 44 Figure 24. A typical compressive stress - deflection behavior of aerated slurry - infiltrated chicken mesh. ................................ ................................ ................................ ................................ .... 46 Figure 25. Tensile stress - deflection curves for non - aerated and aerated slurry - infiltrated chicken mesh. ................................ ................................ ................................ ................................ .... 46 Figure 26. Typical appearance of a failed tension test specimen of aerated slurry - infiltrated chicken mesh at relatively large tensile deformations. ................................ ....................... 47 Figure 27. Flexure stress - deflection curves for non - aerated and aerated slurry - infiltrated chicken mesh sheets. ................................ ................................ ................................ ........... 48 Figure 28. Flexural failure modes of non - aerated and aerated slurry - infiltrated chicken mesh sheets. ................................ ................................ ................................ ................................ .. 49 Figure 29. Cross - section and flexural strain distribution of an aerated slurry infiltrated chicken mesh rectangular section. ................................ ................................ ................................ ... 51 Figure 30. Preparation of foamed water ................................ ................................ ...................... 59 Figure 31. The chicken mesh used in this experimental program ................................ ................ 61 Figure 32. Chicken mesh orientations: longitudinal (left), and transverse (right). ...................... 61 Figure 33. Cr oss - section and flexural strain distribution of aerated slurry infiltrated chicken mesh. ................................ ................................ ................................ ................................ .... 63 Figure 34. Construction of the aerated slurry - infiltrated chicken mesh frame ........................... 65 Figure 35. The test setup used for performance of cyclic tests on the aerated slurry - infiltrated chicken mesh frame ................................ ................................ ................................ ............. 67 Figure 36. Plastic hinge formation in beam near the beam - column joint under reversed cycling testing with growing displacement amplitudes. ................................ ................................ . 68 xiv Figure 37. The hysteretic response, and the initial and stabilized envelopes of the frame subjected to cyclic loading per SPD (ASTM E2126) test method. ................................ ....... 69 Figure 38. Averaged initial and stabilized envelope curves of the aerated slurry - infiltrated chicken mesh frame. ................................ ................................ ................................ ............ 69 Figure 39. Averaged initial envelope curves of the aerated slurry - infiltrated chicken mesh frame versus those of lateral load - carrying systems based on OSB and hardwood. .................... 70 Figure 40. Definition of EEEP curve (ASTM E2126) ................................ ................................ ...... 71 Figure 41. The initial and stabilized envelope curves of the aerated slurry - infiltrated chicken mesh frame, and the EEEP curve corresponding to the initial envelope. ........................... 72 Figure 42. Elastic stiffness of different sheathing materials ................................ ....................... 73 Figure 43. Preparation of the aerated slurry. ................................ ................................ .............. 84 Figure 44. Examples of the aerated slurry thermal conductivity test specimens. ...................... 85 Figure 45. The hammer mill used for grinding of wood. ................................ ............................. 86 Figure 46. Ground wood insulation. ................................ ................................ ............................ 86 Figure 47. Particle size distri bution of the ground wood insulation. ................................ .......... 86 Figure 48. The hammer mill used for shredding of straw ................................ ........................... 87 Figure 49. Shredded straw insulation. ................................ ................................ ......................... 87 Figure 50. Length distribution of the shredded straw ................................ ................................ . 88 - ... 88 Fig ure 52. Thermal conductivity test setup ................................ ................................ ................. 89 Figure 53. The polypropylene ring used to prepare biomass insulation materials. .................... 90 Figure 54. Insulation specimens for thermal conductivity test ................................ ................... 90 Figure 55. The relationship between the the rmal conductivity and the bulk density of the three biomass - based loose insulation materials ................................ ................................ ........... 91 Figure 56. Effect of the cellulose insulation bulk density on its thermal conductivity. .............. 92 xv Figure 57. Thermal conductivity versus temperature for the loose biomass - based insulation materials. ................................ ................................ ................................ ............................. 93 Figure 58. Thermal conductivity test results for aerated slurries of different bulk densities. .... 93 Figur e 59. The building system. ................................ ................................ ................................ ... 94 Figure 60. Building plans with business and residential occupancy patterns (1 ft = 0.305 m). .. 95 Figure 61. The building orientation. ................................ ................................ ............................ 96 Figure 62. Effects of the wall insulation on the cooling and heating loads of the building (RSI (K.m2/W) = R - value (US) (ft2.oF.hr/Btu) /5.68). ................................ ................................ .. 98 Figure 63. Effects of the roof insulation on the cooling and heating loads of the building (RSI (K.m2/W) = R - value (US) (ft2.oF.hr/Btu) /5.68). ................................ ................................ .. 98 Figure 64. Effects of the floor insulation on the cooling and heating loads of the building (RSI (K.m2/W) = R - value (US) (ft2.oF.hr/Btu) /5.68). ................................ ................................ .. 99 Figure 65. The heating/cooling, insulation and total costs versus the wall insulation condition. ................................ ................................ ................................ ................................ ............ 100 Figure 66. Schematics of a layered wall structure. ................................ ................................ .... 102 Figure 67. Cooling energy demand of the two building systems. ................................ ............. 102 Figure 68. Heating energy demands of the two building systems. ................................ ........... 102 Figure 69. Fine wood particles. ................................ ................................ ................................ .. 112 Figure 70. Particle size distribution of the ground wood ................................ .......................... 113 Figure 71. Wood chips ................................ ................................ ................................ ............... 113 Figure 72. Particle size distribution of the wood chips insulation. ................................ ............ 113 Figure 73. Shredded straw. ................................ ................................ ................................ ........ 114 Figure 74. Length distribution of the shredded straw. ................................ .............................. 114 Figure 75. Wood chips treated with aerated cement slurry. ................................ .................... 115 xvi Figure 76. Fungi (Aspergillus) inoculated in a nutrient medium. ................................ ............. 118 Figure 77. The growth curve of A spergillus niger cultivated as batch cultures in nutrient medium (each data paint is the mean value of two measurements ................................ . 119 Figure 78.Classification scale for fungal growth ................................ ................................ ........ 119 Figure 79. Equilibrium moisture contents of selected insulation materials. ............................ 120 Figure 80. Water holding capacity test results for untreated wood chips and fine wood particles over a submersion period of 65 days. ................................ ................................ . 121 Figure 81. An example of visually notable fungus growth on untreated shredded straw that was submerged in water for 48 hours and then exposed to 21 days of fungal. ...................... 121 Figure 82. Optical microscope images of treated and untreated wood chips and shredded straw after 4 weeks of exposure to fungi in ambient moisture ................................ .................. 123 Figure 83. Fungal coverage of untreated and treated wood chips subjected to high humidity or direct water exposure prior to incubation ................................ ................................ ........ 124 Figure 84. The visual appearance and the particle size distribution of the pumice used in this investigation. ................................ ................................ ................................ ...................... 137 Figure 85. Compressive strength test results. ................................ ................................ ........... 139 Figure 86. XRD patterns of the raw pumice, and alkali activated cements formulated with pumice. M (Manitobaite); A (Alite); Me (Melanterite); Q (quartz) ................................ ... 140 Figure 87. FTIR spectra for raw pumice (a) and the hydration products of the cement formulation (and processed) using pumice (Mix 9). ................................ .......................... 142 Figure 88. SEM observation for microstructure of raw pumice (a,b), and hydration products of alkali activated cement based on pumice (c,d) ................................ ................................ . 144 Figure 89. Thermogravimetry and differential thermal analysis data for the raw pumice used as aluminosilicate precursor. ................................ ................................ ................................ . 145 Figure 90. Thermogravimetric curve of alkali activated cement based on pumice after thermal activation. ................................ ................................ ................................ .......................... 146 xvii Figure 91. Effect of chemical reagents on heat released during geopolymerization reaction for24 hour at 27° ................................ ................................ ................................ ................ 147 Figure 92. Effect of the activation methods of volcanic tuff on heat released. ........................ 148 Figure 93. Particle size distribution of the milled municipal solid waste (MSW) incineration ash. ................................ ................................ ................................ ................................ ............ 162 Figure 94. FTIR spectra of: (a) raw ash materials; and (b) the mechanochemically processed hydrated binder ................................ ................................ ................................ ................. 167 Figure 95. SEM micrographs of the ground municipal solid waste (MSW) ash, coal fly ash, and ground rice husk used in this investigation. ................................ ................................ ...... 168 Figure 96. XRD patterns of the three ashes used in this investigation (C=calcite, Q=quartz, Mu=mullite, and patterns of the mechanochemically processed hydrated binder ; (Q: Quartz, M:Muscovi te , P : Portlandite, C : Calcite ................................ ............................. 169 Figure 97. Seven - day compressive strengths obtained with different sources of alkalis. ........ 171 Figure 98. Microstructures of hardened geopolymer binder pastes with either sodium carbonate or potassium hydroxide used as the sources of alkalis ................................ .... 171 Figure 99. Compressive strength development attributes of hydraulic binders formulated with different RHA and MSW ash contents ................................ ................................ ............... 17 3 Figure 100. Representative SEM micrographs of the hydration products of hydraulic binders formulated with different rice husk ash (RHA) and municipal solid waste (MSW) ash contents ................................ ................................ ................................ ............................. 174 Figure 101. Toxicity characteristic leaching procedure (TCLP) analysis of hydraulic binder prior to and after m echanochemical processing and subsequent hydration of binder ............ 175 1 CHAPTER 1 : INTRODUCTION 1.1 General The goal of this research is to develop building structural materials and systems that can make effective use of locally available materials and construction resources. Aerated concrete with bulk densities less than 1 g/cm 3 is generally viewed as a non - structural material that offers thermal insulation q ualities. The research described here found that a reinforcement system with high specific surface area, close spacing , and desired mechanical bonding with matrix would enable use of aerated concrete in structural applications. Chicken mesh (poultry nettin g) was used in this investigation as a commonly available reinforcement that meets the requirements for transforming aerated concrete into a structural material. Viable volume (and area) fractions of chicken mesh for structural applications produce a high degree of congestion with the formwork. Therefore, an aerated slurry of high flowability was used to thoroughly infiltrate the congested reinforcement system , facilitating thorough consolidation and desired interfacial interactions. The mesh behaves as a h omogeneous reinforcement to produce lightweight cementitious composites with a desired balance of strength - to - weight ratio, ductility and toughness (Wafa and Fukuzawa 2010). Ferrocement, a cementitious mortar with wire mesh reinforcement, provided the insp iration for development of aerated slurry - infiltrated chicken mesh (Naaman 2000). 2 1.2 Summary of Research This thesis is divided into nine chapters, with Chapters 2 through 8 each containing a stand - alone paper previously published in peer - reviewed , reputable , high - impact - factor journal s . Chapter 9 summarizes highlights of this work and briefly discusses potential applications . For convenience, the references have been consolidated at the end of each chapter. The abstracts for each of these papers are included below to summarize the work described in each chapter. 1.2.1 Physio - Microstructural Properties of Aerated Cement Slurry for Lightweight Structures Cementitious composites, including ferrocement and continuous fiber reinforced cement, are increasingly considered for building construction and repair. One alternative in processing of these composites is to infiltrate the reinforcement (continuous fibers or chicken mesh) with a flowable cementitious slurry. The relativel y high density of cementitious binders, when compared with polymeric binders, are a setback in efforts to introduce cementitious composites as lower - cost, fire - resistant, and durable alternatives to polymer composites. Aeration of the slurry is an effectiv e means of reducing the density of cementitious composites. This approach, however, compromises the mechanical properties of cementitious binders. An experimental program was undertaken in order to assess the potential for production of aerated slurry with a desired balance of density, mechanical performance, and barrier qualities. The potential for nondestructive monitoring of strength development in aerated cementitious slurry was also investigated. This research produced aerated slurries with densities a s low as 0.9 g/cm 3 with viable mechanical and barrier qualities for production of composites. The microstructure of these composites was also investigated Almalkawi, Salem et al. (2 018) . 3 1.2.2 Mechanical Properties of Aerated Slurry - Infiltrated Chicken Mesh Aerated slurry - infiltrated chicken mesh was evaluated as a ductile and lightweight material for building construction. The compressive strength of the aerated slurry, and the tensile, compressive and flexural behavior of the aerated slurry - infiltrated chicken mesh were evaluated. Aerated slurry provided a relatively low compressive strength, which did not suit load - bearing applications. Aerated slurry infiltrated chicken me sh, on the other hand, provided desired mechanical properties, including significantly improved compressive strength, for load - bearing applications. The system exhibited a ductile failure mode which can be attributed to the high specific surface area and t he desired mechanical interlocking of the chicken mesh reinforcement. The effects of aeration on the system behavior were evaluated. A theoretical model was developed for evaluating the mechanical behavior of aerated slurry infiltrated chicken mesh. Aerate d slurry - infiltrated chicken mesh offers a desired combination of light weight and mechanical characteristics for use as a building construction material (Almalkawi, Hong et al. 2018) . 1.2.3 Behavior of a Lightweight Frame Made with Aerated Slurry - Infiltr ated Chicken Mesh Under Cyclic Lateral Loading Aerated slurry - infiltrated chicken mesh is a ductile and light - weight material for seismic - resistant building construction. An aerated slurry - infiltrated chicken mesh frame was subjected to cyclic lateral loa ding in order to assess its load - bearing capacity, ductility and hysteretic energy dissipation capacity. The frame exhibited a ductile failure mode compatible with its strong column - weak beam design. It also exhibited a desirable hysteretic energy dissipat ion capacity. Comparisons were made between the performance characteristics of this frame versus those of 4 structural systems of similar geometric attributes made primarily of wood - based sheets. Semi - empirical models were developed for prediction of the str uctural behavior of aerated slurry - infiltrated chicken mesh. The structural performance of the frame made with aerated slurry - infiltrated chicken mesh under cyclic lateral loads was compared against those of lateral load - resisting systems of comparable geo metric attributes comprising primarily of OSB and hardwood sheets (Almalkawi, Hong et al. 2018) . 1.2.4 Evaluation of the Energy - Efficiency of an Aerated Slurry - Infiltrated Mesh Building System with Biomass - Based Insulation Experimental investigations and numerical analyses were cond ucted on the thermal attributes of a building system made with locally available structural and insulation materials. The structural material, which also offers some insulation qualities, is referred to as aerated slurry - infiltrated mesh. The insulation ma terials used in this building are based on biomass; the alternatives considered here include ground wood, shredded straw, and cellulose. Thermal conductivity tests were performed on aerated slurries of different bulk densities, and on the biomass - based ins ulation materials, some of which were prepared with different bulk densities. The competitive merits of the biomass - based indigenous insulation materials were assessed. The correlations between bulk density and thermal conductivity were evaluated and ratio nalized based on the prevalent mechanisms of heat transfer in different materials. The effects of temperature on the thermal conductivity of different biomass - based indigenous insulation materials were investigated. For wall insulation, a cost analysis was conducted in order to select the optimum insulation level. The thermal mass of the aerated slurry - infiltrated mesh building 5 system was found to favor its energy - efficiency when compared with a similar wood building (Almalkawi, Soroushian et al. 2019) . 1.2.5 Aerated Cement Slurry and Controlling Fungal Growth of Low - Cost Biomass - Based Insulation Materials Biomass ash - based insulation in the form of wood chips or ground wood offers desired thermal insulation qualities complemented with low cost, ready availability, and favorable ecological features. There are, however, concerns with the resistance to fire, moisture and fungus growth of such insulation. The work reported herein focuses on improvement of the resistance to fungus growth of low - cost biomass - based insulation comprising largely of wood chips or ground wood which offer desired thermal insulation qualities. When exposed to a humid environment, how ever, fungal growth on wood and straw is an important consideration. An experimental investigation was conducted in order to evaluate the effectiveness of a simple treatment in mitigating fungal growth on wood - and straw - based insulation. This treatment in volved blending of wood chips or particles, or shredded straw , with an aerated slurry that offers the potential to mitigate fungal growth on biomass by a combination of physical and chemical effects without imposing a weight penalty. Experimental results v erified the effectiveness of this treatment in controlling fungal growth on wood and straw subjected to different moisture Almalkawi, Soroushian , 2019) . 6 1.2. 6 One - Part Alkali Activated Cement Based Volcanic Pumice A hydraulic cement was developed using abundant natural materials and simple processing methods that relied upon a combination of heating at moderately eleva ted temperatures and milling. The resulting cement produced viable qualities for use in structural applications. Pumice, a volcanic tuff, was used as aluminosilicate precursor in production of one - part alkali activated cement. Depending on their cooling r ate and aging processes, volcanic tuffs exhibit different degrees of reactivity. The pumice used in this project was subjected to heat treatment followed by mechanochemical processing, together with different naturally occurring sources of alkali or alkali ne earth metal cations, into hydraulic (one - part alkali activated) cements. The resultant hydraulic cements were evaluated based on their strength development characteristics via hydration reactions. The particle size distribution and heat of hydration of cement particles, and the chemical composition, mineralogy, bond structure, thermal attributes and morphology of cement particles and hydrated cement paste were also investigated. The results indicated that some of the simple formulations and processing co nditions developed in the project produce hydraulic cements with viable structures and strength development qualities (Almalkawi, Hamadna et al. 2017 ) . 1.2.7 Potential of Using Industrial Wastes For Production Of Geopolymer Binder As Green Construction Materials Rice husk ash, Municipal Solid Incineration Ash and coal fly ash was served as aluminosilicate precursor in synthesis of one - part alkali activated geopolymer binder. These by - products industrial wastes were subjected to physio - chemical processing of materials (mechanochemical synthesis) together with different naturally originated sources of alkaline 7 earth metal cations into one - part alkali activated (geopolymer) binder binders. The binder of hydraulic binders was assessed based on their strength development attributes and morphology with respect to silica content, diffusion of Calcium ions and compositions of Alkali activator. The pa rticle size distribution, the chemical composition, mineralogy, bond environment, of binder particles and effective immobilization of heavy metals of hydrated binder pastes were also inspected. The results highlighted that the ternary blend of combustion a shes to produce hydraulic binders with strength development qualities and safe disposal as material for building construction (Almalkawi, Balchandra et al. 2019) . 8 CHAPTER 2 : PHYSIO - MICROSTRUCTURAL PROPERTIES OF AERATED CEMENT SLURRY FOR LIGHTWEIGHT STRUCTURES - Microstructural Properties of Aerated C ement by Areej T. Almalkawi, Talal Salem, Sameer Hamadna, Darsanasiri, Parviz Soroushian, Anagi Balchandra and Ghassan Al - Chaar in Materials 2018, 11, 597. 2.1 Introduction Continuous fiber reinforced cement composites and ferrocement are examples of composites used in building construction and repair applications (Prota, Nanni et al. 2004, Bianchi, Arboleda et al. 2013, Nelson, Fam et al. 2014, Donnini, y Basalo et al. 2017) . When compared with polymer composites, cementitious composites offer improved fire and moisture resistance, and economics. The density of cementitious matrices, however, is higher than that of polymeric matrices. One approach to production of cementitious composites involves infiltration of the reinforcement system with a cementitious slurry. Aerat ion of the slurry offers the opportunity to reduce the density of cementitious matrices. While aeration tends to compromise the strength of cementitious materials, the aerated matrices may still be able to meet the demands on their mechanical performance i n the context of composites with relatively high - volume fractions of continuous reinforcement with high specific surface area. These demands are different from those placed on concrete in conventional reinforced concrete structures. The combination of aera tion and reinforcement of high specific surface area and close spacing could also provide 9 desired workability attributes (e.g., ease of screw application and cutting) that would make some wood construction techniques applicable to the material. Efforts to reduce the density of slurry need to address (besides mechanical performance and interactions with different reinforcement systems such as wire mesh reinforcement) two aspects of the slurry behavior that are of practical significance in this application: ( i) sorptivity for protecting the insulation and the interior of the building against moisture transport; and (ii) thermal conductivity for adding value towards enhancing the energy - efficiency of the building. The synergy between fibers and organic polymer s has been key to the emergence of composites as widely used structural materials. In this synergistic action, fibers account for the distinctly high strength and modulus of composites. Organic polymers, on the other hand, provide for stress transfer to fi bers, and stress redistribution among fibers upon early rupture of some statistically weaker ones (Mallick 2007) . These contributions o f the polymer matrix rely heavily upon their strain capacity and desired adhesion to fibers. Given the brittle nature of polymer matrices such as epoxy; it is their relatively low elastic modulus that is responsible for their elongation capacity. The polym er matrix also contributes barrier qualities to composites. The generally open molecular structures of both organic polymers and fibers are responsible for Weight saving has been a vital consideration in transition from metals to composites in aerospace and other applications (Mallick 2007) . The work reported herein focuses on development of an inorganic matrix with reduced density and elastic modulus that suits utilization as matrix in continuous fiber reinforced composites that have similarities to ferrocement products. The matrix developed here is an 10 aerated slurry that offers desired rheological attributes for infiltrating fabric and mesh reinforcement systems. Aerated cementitious materials (e.g., aerated concrete) have been developed mostly to provide thermal insulation qualities (Al - Jabri, Hago et al. 2005, Ng and Low 2010, Alengaram, Al Muhit et al. 2013) . This work focused on development of aerated slurries with a relatively low density and modulus and viable strength for use as matrix in structural composites as investigated in our previous studies (Almalkawi, Hamadna et al. 2017, Almalkawi, Hong et al. 2018, Almalkawi, Hong et al. 2018) . This aerated slurry - infiltrated mesh is developed as a construction material that offers qualities intermediate between wood and concrete. It is intended to provide a desired balance of relatively low density, ductility, toughness, strength, workability, moisture and fire resistance, and durability under weathering exposure. 2. 2 Materials and Methods The aerated slurry was prepared by mixing the foaming agent (saponin). Saponi ns are natural surfactants found abundantly in various plant species. More specifically, they are amphipathic glycosides comprising one or more hydrophilic glycoside moieties combined with a lipophilic triterpene derivative (Hostettmann and Marston 199 5) . Figure 1 . shows a saponin molecule obtained from the residues of sisal defibering. It has been used in formulation of detergents (Ribeiro, Barreto et al. 2013) . 11 Aeration of cementitious materials can be accomplished via stabilization of entrapped air using surfactants (Nambiar and Ramamurthy 2007, Ramamurthy, Nambiar et al. 2009, Zhang, Provis et al. 2014) , or by the addition of fine powder that generates gas by undergoing chemical reactions with cementitious materials. Aerated concrete has been produced with a wide range of densities (300 to 1800 kg/m 3 ). The focus of this work is on achieving densities below 1,000 kg/m 3 that are generally viewed as insulating materials. McCarthy 2005) Saponin (a hydrolyzed protein extracted from plants) (Fenwick and Oakenfull 1983, Osbourn 1996, Shimoyamada, Ikedo et al. 1998) was used in this work as a surfactant for production of ae rated slurry. Saponin was mixed with the mixing water of slurry, and agitated to form foam, which was then mixed with Portland cement type 1 to produce the aerated slurry. As a surfactant, saponin lowers the surface tension of water. Surfactants are mo lecules with polar and nonpolar ends that attach to water and air, respectively . The orientation of surfactant molecules in bulk solution is random. Those occurring at the air/liquid interfaces or adsorbed on cement particles, however, have preferred orien tations that tend to minimize the unfavorable interactions between the liquid phase and different molecular sections of the surfactant. shows the alignment of a monolayer of surfactant molecules at the interface between air and surrounding liquid phase. Th e hydrophobic tails of surfactant molecules stick out of the solution to reduce the distortion of water molecules, and 12 thus lower the overall free energy of the system (Du and Folliard 2005, Murray 2007) . The mutual repulsio n between the hydrophilic heads of surfactant molecules reduces the attraction of the bulk liquid phase, producing a lower surface tension. Because of the electrostatic component of the repulsion force of ionic surfactants, their effectiveness to reduce su rface tension is more significant than that provided by nonionic surfactants (Rosen and Kunjappu 2012) . The nature and concentration of surfactants determine the physical and chemical properties of the air bubble/liquid interfaces, including surface tension (equals to free surface energy) and stability. The electrostatic and steric repulsions between surfactants help stab ilize the air bubbles formed within the liquid (Binks 2002, Maldonado - Valderrama, Martín - Molina et al. 2007) . The hydrophilic ends of the surfactant molecules are also electrostatically attracted to cement particles, that is also a factor in stabilizing the air bubbles within cement paste ( Figure 2 . ). 13 . Sa ponin and water were mixed at 1200 rpm rotational speed, using a craftsman® mixing blade attached to a drill ( . ), to produce foamed water. The foamed mixing water was then added to cement at water/cement ratio of 0.45 to 0.6. Mixing was accomplished in a mortar mixer for 2 minutes. The water/cement rat io of different aerated slurries was adjusted in order to produce a desired fresh mix rheology for infiltrating multiple layers of chicken mesh. The required fresh mix rheology could be defined by a viscosity of about 1900 cP and a yield strength of about 70. The resulting aerated slurry was placed in 50 mm cube molds and kept in sealed condition at room temperature for 24 hours. The cube specimens were then demolded and cured at 95±5% relative humidity and room temperature for 7 days. The aerated slurry mi xes proportions considered in this experimental program are introduced in Table 1 . For the non - aerated slurry (with 0% saponin content), water/cement ratio was between (0.45 - 0.55) 14 Mix Saponin dosage (by weight of cement) Water/Cement Ratio 1 0.005% 0.45 2 0.01% 3 0.02% 4 0.005% 0.50 5 0.01% 6 0.02% 7 0.005% 0.55 8 0.01% 9 0.015% 10 0.02% 11 0.025% 12 0.03% 13 0.02% 0.6 14 0.025% Figure 4 . shows examples of the aerated slurry cube specimens, that were tested in compression for measurement of the compressive strength of aerated slurry (at 7 days of age). The density of aerated slurry was measured by dividing the air - dried weight to the volum e of these specimens. 15 (a) Schematics ( b) Picture of multiple specimens during the test The aerated slurry would be the primary protection of the building interior and also the indigenous insulation to be used within the structural panels against weathering effects. Moisture would be transported through the aerated slurry skins (with chicken mesh reinforcement) via capillary sorption. An experimental study was thus undertaken in order to measure the effects of aeration on the capillary sorptivity of the slurry. Sorptivity tests were performed per ASTM C1585; the specimens used for this purpose were cylinders of 100 mm diameter and 50 mm thickness. A schematic of the test setup is shown in Figure 5 a . , and a picture of multiple specimens during sorptivity testing is shown in Figure 5 b . The specimens were demolded after 24 hours of storage in sealed condition and were cured at room temperature until the test age. This test method involves exposure of one flat surface of spe cimen to water, which the remaining surfaces sealed against moisture loss. Mass gain over time is recorded as a measure of moisture sorption. Sorptivity is expressed in terms of the sorption rate of moisture into the aerated slurry. This test was continued for 2 days in order to gain further insight into schematic time - history of capillary sorption (Hall and Yau 1987, Dias 1993) .The ultrasound pulse velocity (UPV) of aerated slurry was measured nondestruc tively using a portable equipment (manufactured by PUNDIT). The UPV test setup is shown in F igure 6 . In this test, an ultrasonic 16 pulse is generated and transmitted to the surface of concrete through the transmitter transducer. The time taken by the pulse to travel through the aerated slurry, t us , is measured by the receiver transducer on the opposite side. The 54 kHz transducers were positioned at the cen ter of each opposing face. The propagation time of the ultrasonic waves transmitted through the 150 mm long cylindrical specimens was measured with accuracy up to 0.1 s. A thin couplant (solid blue Vaseline) was used at the interface between transducers an d the aerated slurry specimen surfaces to ensure good contact. The pulse travel time (t) from the front side to the rear side was automatically recorded. The ultrasound pulse velocity was measured approximately 50 hours after mixing of the aerated slurry (Liu, Zhang et al. 2011, Zhang, Zhang et al. 2012, Wei, Yunsheng et al. 2014) . The specimens used for performance of the ultrasound pulse velocity were prepared from aerated slurry mixes of similar proportions as those used for other expe riments; the mixes used for preparation of the ultrasound pulse velocity specimens, however, were not the same as those used for preparation of the specimens used in other tests. All specimens were cured at room temperature and 95±5% relative humidity . The thermal conductivity of aerated slurry test was measured at 7 days of age in accordance to ASTM C177. Aerated slurry cement specimens were oven dried for 24 h at a 17 temperature of 105±5 o C. Figure 7 . shows the thermal conductivity testing configuration and test to simulate outdoor and indoor tempe ratures. Temperatures on the hot and the cold plates as well as the heat flow were recorded versus time over 24 hours. The results, after the process reached equilibrium, were used to calculate the thermal conductivity of aerated slurry. Furthermore, an aerated slurry samples were subjected to SEM observation to evaluate microstructural features. SEM observations were carried out on JCM - accelerating voltage of 10 - 15 kV using a secondary electron (SE) detector. The inve stigations were conducted on fracture surfaces of the paste of the samples after 28 days. Samples were sputtered with gold before the SEM measurements. 18 2.3 Experimental Results and Discussion 2.3.1 Compressive strength Table 2 . presents the measured values of 7 - day compressive strength and density for the aerated slurry mix designs introduced earlier in Table 1 . Lower values of density tend to correspond with lower values of compressive strength. This is both because of the rise in air content and also the increase in water/cement ratio for achieving viable fresh mix rheology. Mix 13 with density of 0.9 g/cm 3 and 5.4 MPa compressive strength at 7 days provides a viable balance of density and strength for the targeted ferro - cement application. This paper strongly emphasize the density of aerated slurry in order to enhance the efficiency of seismic design (Guo, Juan et al. 2011, Ohsaki, Miyamura et al. 2016) and also enable manual installation of the building structure. Mix 7 - Day compressive strength, MPa Density, g/cm 3 1 10.7 1.9 2 8.2 1.5 3 6.3 1.4 4 14.1 1.2 5 10.5 1.81 6 9.2 1.3 7 13.3 1.6 8 11.1 1.7 9 9.4 1.3 10 6.4 1.17 11 2.4 0.65 12 1.2 0.8 13 5.4 0.9 14 7.1 1.12 2.3.2 Sorptivity The s orptivity test results are presented in Figure 9 . as the capillary rise of moisture versus time for aerated slurries prepared with different dosages of the foaming agent (saponin), with water/cement ratio of 0.55. The two higher dosages of foaming agent (0.015% and 0.02%) are 19 observed to produce lower sorption rates and capacities. This is a positive trend, indicating that lowering the density of the slurry via aeration would actually improve its barrier qualities for protecting the building interior as well as the natural insulation against weathering effects. The initial sorption rate (S i ) is the slope of the sorption curve shown in Figure 8 . up to 6 hours; the secondary sorption rate is the slope of the curve after 1 day. Both these calculations are made using a linear regression analysis (ASTM C1585): The resulting values of initial and secondary sorption rate are presented in Table 3 . together with the corresponding values of the aerated slurry density. These results confirm that lowering the density of aerated slurry from 1.7 to 1.17 - 1.3 g/cm 3 leads to a significant drop in the initial and secondary sorption rates of the slurry. This can be explained by the fact that aeration introduces isolated air bubbles into the slurry, which disrupt the continuity of capillary pores through which sorption occurs (Prim and Wittmann 1983, Tada and Nakano 1983, Goual, De Barquin et al. 2000, Giannakou and Jones 2002, Madjoudj, Quenendec et al. 2002, Nambiar and Ramamurthy 2007) . An overall sorptivity value is also presented in Table 3 . which is the slope of a regression line fit into the whole data points (using the above equation). The overall sorptivity values further confirms the drop in sorptio n rate with reduction of the density of aerated slurry. 20 In order to confirm the finding that aeration actually reduces the sorption rate and extent of slurry (i.e., enhances its barrier qualities), tests were also performed on a slurry without any aeration. The sorption test data presented in Figure 9 . Sorptivity of non - aerated versus aerated slurries . confirm that aeration reduces the rate and extent of moisture sorption into the slurry. As schematically depic ted in Figure 10 . introduction of isolated air bubble forces tortuous sorption paths through capillary pores, which reduce the sorption rate of the slurry. The experience with entrained air bubbles indicates that individual air bubbles remain largely empty of water even under long - term exposure to moist conditions. This phenomenon as well as the reduction in the rate of moisture sorption explain the d rop in the extent of moisture sorption with introduction of individual air bubbles via aeration of slurry. Dosage of foaming agent % 0.01% 0.015% 0.02% Initial sorption rate, mm/ s 0.0242 0.0188 0.0132 Secondary sorption rate, mm/ s 0.0044 0.0013 0.0019 R 2 (Regression value) 0.951 0.950 0.958 Density, g/cm 3 1.7 1.3 1.17 Sorptivity, mm/min 0.5 0.75 0.5 0.34 21 (a) Non - aerated (b) Aerated 2.3.3 Optic Microscop e Optic microscope images were obtained from sections of aerated slurries prepared with different dosages of the foaming agent in order to understand the m orphology of air bubbles and explain their effects on compressive strength. Figures 1 1 a . and 1 1 b . show microscopic images of slurries prepared with 0.005% and 0.02% concentrations of the foaming agent, respectively. A rise in the foaming agent dosage is observed to increase the size (as well as the volume fraction) of air bubble. It should be noted th at smaller and regularly formed air bubbles produce higher compressive strengths than coarser and irregularly formed air bubbles (Just and Middendorf 2009) . Mechanical properties are strongly influenced by the dis tribution of pores within the hardened aerated slurry (Olorunsogo and Wainwright 1998, Kearsley and Wainwright 2002) . The 22 spherical and distributed nature of foams in Figure 11 b . with higher air content led to a viable level of compressive strength which was not lowe r than that provided by the aerated slurry shown in Figure 11 b . with lower content of irregularly shaped air bubbles. This observation confirms that microstructural properties are primary factors influencing the material properties of aerated slurry (Dhir and Henderson 1999) . An example optic microscope image of an exterior surface of an aerated slurry of higher compressive strength is shown in Figure 12 . , where finer and more uniformly dispersed air bubbles can be observed. (a) 0.005% foaming agent (b) 0.02% foaming agent 23 2.3.4 SEM O bservations The spherical geometry of air voids is an important factor influencing the structural and functional properties of aerated binders (Valore 1954, Prim and Wittmann 1983) . In addition, the voids should be distributed evenly in the mass to produce homogenous binders of improved performance. Larger voids (macro - pores) would lower the density of aerated slurry but could compromise its mechanical performance. Depending on the type and dosage of the foaming agent, aerated cement slurries may incorporate both micro - and macro - pores (Sugama, Brothers et al. 2005) . Macro - pores could be formed as a result of the merger of micro - pores. This is because expansion of the matrix upon micro - pore formation generates pressure at the interfaces between micro - pores (Alex anderson 1979) . Figure 13 a . shows an SEM image of an aerated slurry after hydration. Aside from the gel pores (<10 nm) and capillary pores (10 nm to 1 0 µm), hollow shell pores have been proposed as a third category of intrinsic pores in bulk of hydration products (Sugama, Brothers et al. 2005) . Hollow shells have range in size from 1 to around 20 µm, about the size of smaller cement grains, embedded in cement gel and channeled to the outside through capillary and gel pores. An ideal microstructure of aerated cement minimizes the extent of water transport by uniformly distributing the discrete micro - size pores generated by the foaming agent within the cement slurry. The coalescence of many irregular - shaped pores, however, may create a disturbed microstructure, triggering a high degree of water mo bility. In order to verify this, two fractured samples of aerated slurries with 0.75 and 1.3 g/cm 3 bulk densities were examined using a scanning electron microscope ( Figure 13 b . and Figure 1 3 c . , respectively). The image on the right, 24 for the slurry with 1.3 g/cm 3 bulk density, shows a microstructure of uniformly distributed disjunctive pores. In contrast, a differen t microstructure was observed for the aerated slurry with 0.75 g/cm 3 bulk density (left) where an anomalous coalescence developed, yielding a channeled pore structure. This structure allows water to pervade easily through the aerated slurry. A possible exp lanation for the formation of such an anomalous pore structure is the inclusion of tremendous numbers of air bubble cells using an excess amount of foaming agent, which promotes the coalescence of air bubbles as a result of the collapse of the slurry walls separating these bubbles. 25 2.3.5 Ultrasound P ulse V elocity Ultrasound pulse velocity (UPV) is a simple nondestructive means of evaluating concrete, which co uld be used to assess the aerated slurry quality and its development over time. Figure 14 . shows the evolution of ultrasound pulse velocity over time (up to 50 hours) after mixing for three aerates slurries with different densities. UPV is observed to be higher for aerated slurries of higher density. At earlier ages, lower - density aerated slurr ies exhibit a minor rise in UPV for more than 10 hours while the higher - density slurry exhibits a clear trend towards UPV rise as soon as 1 hour after mixing. In order to assess the variability of UPV measurements, three replicated aerated slurry specimens were prepared with the same mix design (Mix 13) and density (0.9 g/cm 3 ). The evolution of UPV with time is presented in Figure 15 . for the three replicated specimens. The variations in UPV for these three test specimens are less than 6%, pointing at the potential value of UPV as a reliable method of monitoring the quality of aerated slurry (and its evolution with time of curing). 26 2.3.6 Thermal C onductivity The lightweight aerated slurry is expected to make some contributions towards thermal insulation of the building. The measured values of thermal conductivity are shown in Figure 16 . versus the density of aerated slurries. As expected, slurries of lower density offer lower values of thermal conductivity Sengul, Azizi et al. 2011) . Air bubbles act as barriers against thermal conduction; the isolated air bubbles do not make any significant contributions to heat transfer via convection (Alengaram, Al Muhit et al. 2013) . 1900 1950 2000 2050 2100 2150 2200 2250 2300 2350 2400 0 10 20 30 40 50 60 UPV (m/s) Time (hr) 0.521 0 0.588 0 0.5012 0.538 0.5293 0.49 0.5 0.51 0.52 0.53 0.54 0.55 0.56 0.57 0.58 0.59 0.6 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Thermal conductivty (w/mk) Density (g/cm 3 ) 27 2.4 Conclusions Aerated slurry is developed as a lightweight matrix for production of cementitious composites embodying reinforcement of high specific surface area for structural applications. A highly flowable slurry is needed for thorough infiltration of th e structural volume that is congested with fine reinforcement systems. This work developed and characterized an aerated slurry comprising a cementitious material of relatively high water/cement ratio that incorporated a foaming agent (saponin). 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Effect of freeze Thaw cycl es on the physicomechanical properties of a pozzolanic mortar. Construction and Building Materials 134 (2017): 32 - 38. Sugama, T., L. Brothers, and T. Van de Putte, Air - foamed calcium aluminate phosphate cement for geothermal wells. Cement and Concrete Composites, 2005. 27(7): p. 758 - 768. 33 Tada, S. and S. Nakano, Microstructural approach to properties of moist cellular concrete. Proceedings Autoclaved Aerated Concrete, Moisture and Properties. Amsterdam: Elsevier, 1983: p. 71 - 89. Uysal, H., et al ., The effects of different cement dosages, slumps, and pumice aggregate ratios on the thermal conductivity and density of concrete. Cement and concrete research, 2004. 34(5): p. 845 - 848. Valore, R.C. Cellular concretes Part 1 composition and methods of pr eparation. I n Journal Proceedings. 1954. Wei, S., Z. Yunsheng, and M. Jones, Using the ultrasonic wave transmission method to study the setting behavior of foamed concrete. Construction and Building Materials, 2014. 51: p. 62 - 74. Zhang, Y., et al., Ultraso und monitoring of setting and hardening process of ultra - high performance cementitious materials. NDT & E International, 2012. 47: p. 177 - 184. Zhang, Z., et al., Geopolymer foam concrete: an emerging material for sustainable construction. Construction and Building Materials, 2014. 56: p. 113 - 127. 34 CHAPTER 3 : MECHANICAL PROPERTIES OF AERATED SLURRY - INFILTRATED CHICKEN MESH Mechanical Properties of Aerated Slurry - Infiltrated Chicken Mesh Almalkawi, Areej T., Weisheng Hong, Sameer Hamadna, Parviz Soroushian, A. G. N. D. Darsanasiri, Anagi Balchandra, and Ghassan Al - Chaar. Construction and Building Materials 166 (2018): 966 - 973. 3.1 Introduction Aerated concrete is traditionally viewed as a n insulating (non - structural) building material. This investigation evaluated the potential to improve the mechanical performance of aerate concrete through the use of a chicken mesh as a continuous reinforcement system with high specific surface area. The re is a growing interest in the use of wire mesh reinforcement in concrete panels (Joseph, Prabakar et al. 2017, Liu, Wu et al. 2017) . Within certain limits, the mesh behaves as homogeneous reinforcement, and produces concrete composites with desired tensile str ength - to - weight ratio, cracking behavior and impact resistance (Wafa and Fukuzawa 2010) . Ferrocement, a cementitious mortar with wire mesh reinforcement, benefits from these advantages associated with the use of nearly isotropic reinforcement systems of high specific surface area and desired mechanical bonding (Naaman 2000) . This work is part of ongoing research that aspire smart utilization of lightweight material in congestion with chicken mesh for structural applications (Almalkawi, Hong et al. 2018) . 35 The main thrust of the work reported herein was to develop a construction material that combines the advantages of wood (ductility, low bulk density, convenient use of fasteners such as screws , etc.) with those of reinforced concrete (moisture, weathering and decay resistance, load - bearing capacity, etc.). Achievement of these goals required use of relatively high reinforcement ratios, which necessitated the use of slurry infiltration in lieu of, say, troweling of mortar that is used in the case of ferrocem ent. Slurry infiltration enables through embedment of the chicken mesh wire in the cementitious matrix in spite of the congestion of volume with the required chicken mesh volume ratio. Aeration of the slurry was required to reduce the bulk density of the m aterial. Chicken mesh (poultry netting) was used in this development as a readily available reinforcement system of high specific surface area with desired mechanical bonding potential in aerated slurry. Streamlined methods were devised for producing aerat ed slurry - infiltrated chicken mesh as a structural material. An experimental program was conducted in order to gain insight into the mechanical performance of this material. The effects of chicken mesh reinforcement on the compressive strength of aerated s lurry was investigated. The effect of aeration of slurry on the system performance was also evaluated. A semi - empirical theoretical basis was developed for the mechanical behavior of aerated slurry - infiltrated chicken mesh. 36 3.2 Experimental Program 3.2.1 Materials 3.2.1.1 Aerated Slurry The slurry mix was prepared in this investigation with Type I Portland cement and tap water. In one of the mixtures, in order to achieve a viable fresh mix workability, a polycarboxylate - based superplasticizer was u sed. The aerated slurry was prepared by adding a foaming agent to the mixing water of slurry. Aeration introduces a homogenous system of fine air bubbles into the cement paste. This is accomplished using foaming agents that stabilize the air voids generate d by agitating the mixing water of slurry to which the foaming agent has been added (Nambiar and Ramamurthy 2007, Ramamurthy, Nambiar et al. 2009, Zhang, Provis et al. 2014) . P reparation of the aerated slurry started with production of foamed water. For this purpose , a foaming agent extracted from plants (saponin) was blended with the mixing water at 1200 rpm rotational speed using a mixing blade attached to a drill Figure 17 . The resulting foamed water was then added to cement and mixed in a mortar mixer for 6 minutes. Current investigations are carried out to produce aerated alkali activated cement based volcanic tuff and limestone (Almalkawi, Hamadna et al. 2017) 37 (a) Prior to stirring (b) Foaming after stirring 3.2.1.2 Chicken Mesh This work chose chicken mesh (hexagonal 20 - gauge galvanized poultry netting) as a steel reinforcement system of high specific surface area. This selection was made due to the broad worldwide availability of chicken mesh. The common mesh used in this investigation was made of steel wires of 1 mm diameter (0.785 mm 2 cross se ctional area). Chicken meshes are available with different wire diameters and spacings. The spacing of hexagonally configured wires generally increase with increasing wire diameter in order to provide comparable wire cross - sectional areas per unit width. G iven the relatively large layers of chicken mesh that need to be infiltrated with aerated slurry, the preference in this investigation was for chicken meshes with larger wire diameter and spacing. The chicken mesh used in this investigation was non - isotrop ic. The stronger direction (vertical in Figure 18 . ) is referred to as longitudinal in this work. 38 3. 3 Experimental Methods An experimental program was con ducted in order to evaluate the effects of some key variables on the mechanical properties of aerated slurry - infiltrated chicken mesh under compressive, flexural and tensile loading. The interactions of chicken mesh with aerated slurry can be characterized as more complex than those between concrete and conventional reinforcing bars. More attention should be paid to the contributions of the aerated (slurry) matrix towards timely mobilization of the load - bearing capacity of the multiple chicken mesh layers t ightly incorporated into the aerated slurry. Test results would be critical to understanding these complex interactions. Aerated slurry - infiltrated chicken mesh can, due to the high specific surface area of steel reinforcement, provide distinctly high leve ls of ductility and energy dissipation capacity. In addition, the high specific surface area and close spacing of chicken mesh wires could benefit various aspects of the aerated slurry performance, including its compressive strength, dimensional stability and resistance to shrinkage cracking. The experimental methods used for evaluating the mechanical behavior of aerated slurry - infiltrated chicken mesh are presented in the following results. The experimental were used to develop semi - empirical models for 39 pr edicting the mechanical performance of aerated slurry - infiltrated chicken mesh. 3. 3. 1 . Tests performed on slurry without chicken mesh reinforcement The experimental work reported here used one non - aerated slurry as control, and different aerated slurry mixt ures. The non - aerated slurry comprised cement: water: superplasticizer at 1: 0.36: 0.004 weight ratios. For the purpose of preparing the aerated slurry mixtures, the foaming agent was added to water and subjected to stirring at relatively high speed in ord er to product foamed mixing water, which was then added to cement and mixed using normal mixing procedures. The water/cement ratio of aerated slurry mixtures ranged from 0.40 to 0.55. The aerated slurry mix proportions are introduced in Table 4 . The resulting aerated slurry was placed in 50 mm cube molds for compression strength test and bulk density measurement. The specimens kept in sealed condition at room temperature for 24 hour a nd cured at 95% relative humidity and room temperature for 7 days. Mix Foaming Agent Dosage, % by wt. Water/cement ratio 0 0 0.35 with 0.004 superplasticizer 1 0.005% 0.45 2 0.01% 3 0.02% 4 0.005% 0.50 5 0.01% 6 0.02% 7 0.005% 0.55 8 0.01% 9 0.015% 10 0.02% 11 0.025% 40 3. 3. 1 Tests performed on aerated slurry - infiltrated chicken mesh 3. 3. 1 .1 Compression The prismatic compression test specimens had planar dimensions of 102 mm by 102 mm, with a height of 229 mm. The chicken mesh configuration used in compression testing of aerat ed slurry - infiltrated chicken mesh specimens is presented in Figure 19 . There were two groups of chicken mesh in these specimens: (i) 30 interior layers placed in folded form; and (ii) four exterior layers wrapped around the interior layers to mitigate the potent ial for split cracking upon screw application to the surface. Along the height, where the chicken mesh layers are oriented in their strong direction, the total number of chicken mesh layers is thus 38 . The aerated slurry mixture comprised cement: water: sa ponin at 1: 0.6: 0.00045 weight ratios. 12 0.03% 13 0.02% 0.6 14 0.025% 41 3 . 3. 1 . 2 Tension Aerated slurry infiltrated chicken mesh sheets with 20 mm thickness and 150 mm width were subjected to tension testing. The number of chicken mesh layers in different tension test specimens varied from 12 to 24. The chicken mesh layers were oriented to tha t the tensile force was resisted in their strong direction. The tension test setup is shown in Figure 20 . The free length of the tension test specimen be tween the two grips was 310 mm (with a total specimen length of 500 mm). Tension tests were performed at a constant displacement rate of 0.05 mm/s. The values of load and deflection were recorded during the tension tests using a data acquisition system. 3. 3. 1 .3 Flexure The aerated slurry - infiltrated chicken mesh sheets tested in flexural had the same dimensions as the tension test specimens. They were subjected to four - point flexure loading over a span of 450 mm Figure 21 . , Load was applied quasi - statically (with a constant displacement rate of 0.033 mm/s), and load - deflection data were collected during the flexure test up to failure. 42 3. 4 Test Results and Discussion 3. 4.1 Compressive strength and bulk density of aerated slurry The aerated slurry mix designs, defined by the foaming agent dosage (expressed as wt.% of cement) and water/cement ratio, and the corresponding measured values of 7 - day compressive strength and bulk density are presented and Figure 22 . Lower values of bulk density tend to correspond with lower compressive strength values. This is both because of the rise in air content and also the increase in water/cement ratio at higher dosages of foaming agent for achieving viable fresh mix rheology. Mix #13 with density of 0.9 g/cm 3 and compressive strength of 5.4 MPa at 7 days provides a viable balance of bulk density and strength for the targeted applicati on. When compared with non - aerated slurry, it can be noted that aeration of slurry (Mix #13) produced 61% drop in bulk density and 90% drop in compressive strength. It should also be noted that increasing water/cement ratio does no necessarily reduces the compressive strength of the aerated slurry. Up to a certain limit, higher water/cement ratios can improve the homogeneity of foam distribution within the aerated slurry, and thus benefit its compressive strength. This work emphasized reduction of density i n order to limit seismic forces (Guo, Juan et al. 2011, Ohsaki, Miyamura et al. 2016) and also allow for manual installation of the building 43 structural components. It was hypothesized that the presence of closely spaced chicken mesh wires with h igh specific surface area would benefit the compressive strength of aerated slurry - infiltrated chicken mesh. 3. 4.2 Compressive behavio r of the aerated slurry - infiltrated chicken mesh A typical compressive stress - deflection curve for an aerated slurry - infiltrated chicken mesh prepared with the aerated slurry Mix #13 is presented in Figure 23 . The presence of chicken mesh significantly improved the compressive strength and ductility of the aerated slurry. The aerated slurry alone provided a compressive strength of 5.4 MPa. In the p resence of chicken mesh, a strain - hardening behavior was observed after this strength levels was reached. The ultimate strength was more than 15 MPa, noting that the specimen was unloaded after the maximum deflection limit of the test system was reached at about 70 mm. One can attribute the observed strain - hardening behavior (and the corresponding rise in compressive strength) of the 10.7 8.2 6.3 14.1 10.5 9.2 13.3 11.1 9.4 6.4 2.4 1.2 5.4 7.1 1.9 1.5 1.4 1.2 1.81 1.3 1.6 1.7 1.3 1.17 0.65 0.8 0.9 1.12 0 2 4 6 8 10 12 14 16 7-Day Compressive Strength, MPa Bulk Density g/cm3 44 aerated slurry - infiltrated chicken mesh partly to the confining effect rendered by the wire mesh with closely spaced wires of high specific surface area. 3. 4.3 Tensile behavior of aerated slurry - infiltrated chicken mesh The three slurries considered in this experimental program provided bulk densities (after hardening and air - drying) of: (1) 2.2 g/cm 3 ; (2) 1.3 g/cm 3 ; and (3) 0.8 g/cm 3 . The highest density of 2.2 g/cm 3 was obtained without aeration of slurry. The tensile load - deflection curv es obtained with 18 layers of chicken infiltrated with aerated (or non - aerated) slurry (producing a sheet of 25 mm thickness) are presented in Figure 24 . together with the load - deflection curve for 18 layers of chicken mesh obtained without slurry - infiltration. The misaligned configuration of chicken mesh wires make it significantly compromises its stiffness and thus its merits as a tensile load - bearing sy stem. The tendency towards realignment of chicken mesh wires at small deflections seriously undermine its structural stiffness. Infiltration with slurry (including aerated slurry), on the other hand, resists this tendency towards realignment of wires, and thus enables mobilization 0 2 4 6 8 10 12 14 16 0 10 20 30 40 50 60 70 80 Stress, MPa Deflection, mm 45 of the tensile load - carrying capacity of the chicken mesh wires at relatively small displacements. Aeration of the slurry to reduce its bulk density does not significantly undermine its ability to mobilize the chicken mesh wires a t small displacements to resist tensile forces. In short, chicken mesh and aerated slurry exhibit synergistic effects in the context of aerated slurry - infiltrated chicken mesh. The confining effects of chicken mesh increases the compressive strength of aer ated slurry by more than 200%. Infiltration of chicken mesh with slurry also enables effects use of the tensile load - carrying capacity of the chicken mesh wires at structurally viable deformation levels. Reduction of the slurry density via aeration from 2. 2 to 0.8 g/cm 3 (by 63%) lowered the tensile strength of aerated slurry infiltrated chicken mesh from 5.4 to 4.2 MPa (by only 22%), as shown in Figure 25 . This finding point at the potential of the aerated slurry - infiltrated chicken mesh to provide a desired balance of low bulk density and relatively high tensile strength. The tensile stiffness of slurry - infiltrated chicken mesh was not reduced significantl y upon aeration for lowering its bulk density. Figure 26 . shows a tensile specimen of aerated slurry - infiltrated chicken mesh after failure in tension. A distributed damage zone was observed where the tendency towards realignment of chicken mesh wires, that was resisted by the aerated slurry surrounding the wires, led to crushing of the aerated slurry at large deformations. 46 0 5 10 15 20 25 0 5 10 15 20 25 30 Tensile Load, kN Deflection, mm Non-aerated slurry infiltrated chicken mesh 1.3 g/cm3 density aerated slurry infiltrated chicken mesh 0.8 g/cm3 density aerated slurry infiltrated chicken mesh Mesh Only 0 1 2 3 4 5 6 0 5 10 15 20 25 30 Stress, MPa Deflection, mm Non aerated slurry infiltrated chicken mesh 1.3 g/cm3 density aerated slurry infiltrated chicken mesh 0.8 g/cm3 density aerated slurry infiltrated chicken mesh 47 The tensile strengths obtained for the slurry - infiltrated chicken mesh sheets pres ented above are summarized in Table 5 . While the slurry density and the number of chicken mesh layers influence the tensile strength of aerated slurry - infiltrated chicken mesh sheets (with high concentration of chicken mesh), all these tensile strengths (except when 6 or 9 layers of chicken mesh are used) occur within a relatively narrow 3.64 4.40 MPa range. Significant reduction of bulk density could be obtained via aeration of the slurry without significant loss of the slurry - i nfiltrated chicken mesh tensile strength. These observations point at the potential of aerated slurry - infiltrated chicken mesh to provide a desired balance of tensile strength and bulk density. Slurry Chicken Mesh Layers Saponin/Cement (weight ratio) Water/Cement (weight ratio) Bulk Density (g/cm 3 ) Non - Aerated 18/24 - 0.36 (0.004) superplasticizer) 2.2 Aerated 16/18 0.0002 0.5 1.3 Aerated 6/9/12/18 0.0005 0.6 0.8 48 3. 4.4 Flexural performance The three slurries considered in this experimental program provided bulk densities (after hardening and air - drying) of: (1) 2.2 g/cm 3 ; (2) 1.3 g/cm 3 ; and (3) 0.8 g/cm 3 . The highest density of 2.2 g/cm 3 was obtained without aeration of slurry. Typical flexural stress - deflection curves for sheets of 25 mm thickness made with non - aerated and aerat ed slurries using 18 layers of chicken mesh are presented in Figure 27 . The flexural behavior is observed to be ductile. Aeration of slurry lowered the f lexural strength but not the ductility of the aerated slurry - infiltrated chicken mesh. Increasing the dosage of foaming agent to reduce the bulk density of the aerated slurry from 1.3 to 0.8 g/cm 3 had relatively small effects on the flexural performance of the resultant sheets. The peak flexural stress obtained with aerated slurry of 0.8 g/cm 3 bulk density was 6.9 MPa. Reduction of the aerated slurry density from 1.3 to 0.8 (by 38%) led to a reduction of the flexural stress from 7.8 MPa to 6.9 MPa (by 11%). The flexure test specimens prepared with non - aerated slurry exhibited multiple cracking and a distributed flexural failure mode ( Figure 28 a . ); flexural failure of the aerated specimens was less distributed ( Figure 28 b . ). 0 5 10 15 20 25 0 10 20 30 40 50 Stress, MPa Deflection, mm Nonaerated slurry infiltrated chicken mesh 1.3 density aerated slurry infiltrated chicken mesh 0.8 density aerated slurry infiltrated chicken mesh 49 . (a) Non - aerated slurry (b) Aerated slurry 3.4.5 Analysis of aerated slurry - infiltrated chicken mesh The aerated slurry makes significant indirect contributions toward tensile strength by restraining the chicken mesh wires (which are p artly oriented at an angle with respect to the tensile stress) from reorientation under tensile stress. The tensile strength of aerated slurry - infiltrated chicken mesh was expressed as follows: T = tensile strength of the aerated slur chicken mesh wires, f y efficiency factor which reflects the degree of restraint offered by the aerated slurry against reorientation of the chicken mesh layers as well as the orientations of wires with respect to the tensile stress direction. An average value of = 0.26 allows for prediction of the experimental values of tensile strength using the above equation. In compression, one s hould account for the direct contribution of the chicken mesh wires (embedded in the aerated slurry matrix), and also their indirect confining effect which raises the effective compressive strength of the slurry. Considering these contributions of chicken mesh, 50 the composite compressive strength of aerated slurry - infiltrated chicken mesh may be expressed as follows: c = compressive strength of the aerated slurry - efficiency factor for the chicken me sh reinforcement in compression (it was assumed to be similar efficiency factor of the aerated s lurry in compression, which benefits from the confining effect o f compression test results performed on aerated slurry - infiltrated chicken mesh. In other words, the aerated slurry that benefits from the beneficial effects of chic ken mesh provides 4.6 times the compressive strength of plain aerated slurry. These relatively large beneficial effects can be that produce relatively larg e strains in compression which, are restrained by the chicken mesh reinforcement of high elastic modulus and specific surface area with closely spaced wires, resulting in confining effects which raise the aerated slurry compressive strength; (ii) chicken m esh with high specific surface area and close wire spacing effectively reinforces the aerated slurry against the microcrack formation under restrained shrinkage, and the growth of these microcracks under load. The rise in compressive strength of aerated sl urry with chicken mesh reinforcement is a significant factor enabling the otherwise non - structural (insulating) aerated slurry to make contributions to the aerated slurry - infiltrated chicken mesh structural performance. 51 Using concepts similar to those used with reinforced concrete, the nominal flexural strength (M n ) of an aerated slurry - infiltrated chicken mesh cross - section ( Figure 29 . ) can be expressed as follows: and h are, respectively, the width and height of a rectangular cross - section. Similar to the approach to reinforced concrete flexural analysis, a constant compressive stress is assumed up neutral axi and compressive forces generated at the section under bending moment: As a first step, the expression derived above for the nominal flexural strength of aerated slurry - infiltrated chicken mesh was verified using the experimental d ata generated for a beam and two sheets made with aerated slurry - infiltrated chicken mesh. These structural test specimens were made with a slurry proportioned at saponin: water: cement weight ratios of 0.00045: 0.6: 1 (which yielded a bulk specific gravit y of 0.8 after hardening and air - drying). 52 Table 6 . presents the aerated slurry - infiltrated chicken mesh sheet dimensions, reinforcement conditions, test results, and the experimental and theoretical values of flexural strength. The theoretical values of flexural strength obtained with the expression presented above are observed to be less than experimental values by only 3 to 5%. The approach outlined abo ve for calculation of the nominal flexural strength of aerated slurry - infiltrated chicken mesh sheets and beams thus yielded favorable accuracy based on the limited test data generated in this investigation. Specim en # of Chicken Mesh Layers Span, mm Width, mm Thickness , mm Reinf. Area Ratio Densit y, g/cm 3 Peak Load, N 3 or 4 Point Loading Flexural Strength, N.m Test Theor y Sheet 12 450 150 20 0.04 0.8 1300 4 97.5 92.67 Sheet 18 450 150 25 0.03 0.8 2500 4 180.5 170.41 Beam 30 800 102 254 0.02 0.8 25000 3 5000 4910.24 8 3.5 Conclusions 1. 2. 53 3. 4. 5. 3.6 Acknowledgements The work reported herein was funded by the U.S. Army Corps of Engineers Grant No. 9132T - 16 - C - 0003 U.S. Army United States. 54 REFERENCES 55 REFERENCES Aboul - Anen, B., A. El - Shafey, and M. 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Zhang, Z., et al., Geopolyme r foam concrete: an emerging material for sustainable construction. Construction and Building Materials, 2014. 56: p. 113 - 127. 57 CHAPTER 4 : BEHAVIOR OF A LIGHTWEIGHT FRAME MADE WITH AERATED SLURRY - INFILTRATED CHICKEN MESH UNDER CYCLIC LATERAL LOADING Behavior of a lightweight frame made with aerated slurry - infiltrated chicken mesh under cyclic lateral loading ." by Almalkawi, Areej T., Weisheng Hong, Sameer Hamadna, Parviz Soroushian, and Ghassan Al - Chaar. Construct ion and Building Materials 160 (2018): 679 - 686. 4.1 Introduction Aerated concrete is traditionally viewed as an insulating (non - structural) building material. A primary premise of the work reported herein is that a reinforcement system with high specific surface area would enable use of aerated concrete in structural ap plications. The high specific surface area and the confining role of such reinforcement is hypothesized to benefit the structural performance of aerated concrete. Construction with reinforcement systems of high specific surface area would be challenged by the congestion of reinforcement which is not favorable to convenient placement and consolidation of aerated concrete. An aerated slurry of high flowability was used in this work to thoroughly penetrate the congested reinforcement system, facilitating thoro ugh consolidation and desired interfacial interactions with the reinforcement. This work chose chicken mesh ( hexagonal 20 - gauge galvanized poultry n etting) as a steel reinforcement system of high specific surface area due to its broad availability across t he world. Concrete structures generally rely on frames as the primary lateral load - resisting structural systems (Arroyo and Gutiérrez 2016, Abd - Elhamed and Mahmoud 2017, Ruiz - García 58 and Aguilar 2017) . Reinforced concrete frames can be desig ned to provide high levels of ductility and (hysteretic) energy dissipation capacity for efficient resistance of seismic forces (He, Lam et al. 1998, Rose 1998, Kwon, Seo et al. 2017, Yun, Kim et al. 20 17) . Aerated slurry - infiltrated chicken mesh can, due to the high specific surface area of steel reinforcement, provide distinctly high levels of ductility and energy dissipation capacity. The work reported herein evaluated the structura l performance of an aerated slurry - infiltrated chicken mesh from under cyclic lateral loads. The data generated on the ductility, hysteretic energy absorption capacity and the lateral load - bearing capacity of the frame, accompanied with structural analyses of the frame, provide insight into the merits of aerated slurry - infiltrated chicken mesh as a robust building materials for construction of seismic - resistant building systems. There has been growing interest in the use of lightweight aerated concrete as b uilding envelope material. The desired balance of thermal and sound insulation qualities, fire resistance, strength, durability, cost, and ease of installation and maintenance of this material favor its broader use in building construction. Memon et al. (Memon, Sumadi et al. 2007, Ng, Low et al. 2012) and Ng et al. (Ng, Low et al. 2012) have reported data on the mechanical performance of autoclaved aerated panels. Low et al. (Low, Ng et al. 2014) and Wakili et al. (Wakili, Hugi et al. 2015) investigated the thermal performance of these panels. Tanner et al. (Tanner, Varela et al. 2005) and Costa et al. (Costa, Penna et al. 2011) investigated the failure modes and seismic behavior of autoclaved aerated concrete walls. The use of these walls in conjunction with steel frames has also been investigated under cyclic loading (Zhenggang, Peng et al. 2017) . The use of fiber reinforced polymer composites towards seismic rehabilitation of autoclaved aerated concrete column s subjected to cyclic loading has also been investigated (Cho, Kim et al. 2012) . 59 The innovative aspect of the work reported herein relates to transformation of an insulating lightweight (aerated) concrete into a structural material through reinforcement with a wire (chicken) mesh reinforcement of high specific surface area. A highly flowab le aerated slurry is used to facilitate infiltration of the chicken mesh reinforcement with the lightweight cementitious matrix. 4.2 Materials and Methods 4.2.1 Aerated Slurry Aeration introduces a homogenous system of fine air bubbles into the cement past e. This is accomplished using foaming agents that stabilize the air voids generated via agitation of the mixing water of slurry that incorporates the foaming agent (Nambiar and Ramamurthy 2007, Ramamurthy, Nambiar et al. 2009, Zhang, Provis et al. 2014, Huang, Zhang et al. 2015) . Preparation of the aerated slurry started with production of foamed water. For this purpose, a foaming agent extracted from plants (saponin) blended with the mixing water at 1200 rpm rotational speed, using a mixing blade attached to a drill ( Figure 30 . ). The foamed mixing water was then added to c ement at water/cement ratio of 0.5. Mixing was accomplished in a mortar mixer for 2 minutes. 60 The aerated slurry used to infiltrate the chicken mesh comprised cement: water: saponin at 1: 0.5: 0.0006 weight ratios, with a bulk density in hardened state of 0.9 g/cm3. Based on trial and adjustment studies, it was found that an aerated slurry with vis cosity of 1900.8 cp and yield stress of 68.2 is capable of infiltrating multiple layers of chicken mesh with the opening size considered in this investigation. Cube specimens of plain aerated slurry with 50 mm dimensions were also prepared for performance of compression tests. The molded specimens were stored in sealed condition (>95% relative humidity) at room temperature) for 7 days, and then subjected to compression testing. The average compressive strength was measured at 5.01 MPa. 4 .2.2 Chicken Mesh The chicken mesh considered in this experimental program ( Figure 31 . ) comprised wire gauge No. 20 (with 0.88 mm diameter, 0.608 mm 2 cross sectional areas) configured he xagonally with wire spacing of 25 mm. Chicken meshes are available with different wire diameter and spacing. Commonly available chicken meshes are made with wires of different diameters; the spacing of hexagonally configured wires are generally increased w ith increasing wire diameter in order to provide comparable wire cross - sectional areas per unit width. Given the relatively large layers of chicken mesh that need to be infiltrated with aerated slurry, the preference in this investigation was for chicken m eshes with larger wire diameter and spacing. Figure 32 . depicts the anisotropic structure of chicken mesh, which provides higher strength in the longitudinal direction a nd lower strength in the transverse direction. 61 . 4.2.3 Aerated Slurry - Infiltrated Chicken Mesh Given the fine diameter of the chicken mesh wires, a relatively low volume fraction (e.g., 1%) of chicken mesh produces a relatively congested reinforcement system. As a result, cementitious materials with nor mal fresh mix rheology cannot be used in this application. The need to infiltrate multiple layers of chicken mesh led to the selection of a flowable slurry as the binder for use with chicken mesh reinforcement. Aerated slurry was used in this application t o lower the density of structural materials for ease of installation and reduction of seismic forces. Aerated concrete is usually used as insulation and not in structural applications. It was hypothesized that the high specific surface area and the confini ng action of chicken mesh would enhance the mechanical performance of the resultant aerated slurry infiltrated chicken mesh to suit structural applications. In chicken mesh, wires are oriented in different directions. Chicken mesh thus offers a high level of flexibility when subjected to tension, which is due to a tendency towards alignment of wires along the direction of tensile force. Their low stiffness excludes chicken mesh from 62 structural applications. When placed within a matrix (aerated slurry in thi s case), however, the wires in chicken mesh are restrained against realignment by the matrix. Depending on the extent of this restraint, the tensile force - resisting capacity of wires would be mobilized from the beginning. This raises the stiffness of chick en mesh, which could translate aerated slurry infiltrated chicken mesh into a structural building material. Semi - empirical equations were developed to express the tensile and compressive strengths of aerated slurry infiltrated chicken mesh, as described be low. 4.2.4 Aerated Slurry Infiltrated Chicken Mesh Frame The models presented earlier for predicting the flexural strength of aerated slurry infiltrated chicken mesh were verified using experimental results (Balaguru, Shah et al. 1977, Pankaj, Arif et al. 2002, Bedoya - Ruiz, Ortiz et al. 2014, Eskandari and Madadi 2015, Saleem and Ahmed 2015, Subramani and Anbuchezian 2017) The tensile strength of aerated slurry infiltrated chicken mesh ( T ) was expressed as follows: fraction of the chicken mesh wires (irrespective of their orientation) at a cross - section that is perpendicular to the tensile stress direction ; f y = yield stress of the chicken mesh degree of restraint provided by the aerated slurry against realignment of wires (0.56 based on experimental results). In compression, the composite behavior of aerated slurry infiltrated chicken mesh produces a compressive strength that can be expressed as follows: 63 c = efficiency factor of chicken mesh reinforcement in compressive (it was assumed to be similar to the efficiency factor of chicken mesh in tension, efficiency factor of aerated sully in c ompression, which was surprisingly found (in compression tests performed on an aerated slurry infiltrated chicken mesh) to be quite large (close to 5). Using concepts similar to those used with reinforced concrete, the nominal flexural strength (M n ) of an aerated slurry - infiltrated chicken mesh cross - section ( Figure 33 . ) can be expressed as follows: 3 was assumed to be equal to the depth of neutral axis c , considering the highly ductile behavior of aerated slurry infiltrated chicken mesh. A constant compressive stress was assumed up to a stress distribution. The value of section subjected to bending moment: 4 64 An aerated slurry infiltrated chicken mesh frame wi th 1.75 m height and 1.4 m width was designed to withstand a concentrated in - plane load of 8 KN applied at its top. The maximum bending moment under this loading condition is: M= F t .h /2 = 7,000 N.m. The cross - section designed to resist this bending moment had 10 cm width and 25 cm height, reinforced with 30 layers of chicken mesh (with the chicken mesh layers oriented longitudinally along the element axis). The area fraction of longitudinally oriented chicken mesh layers at cross - sections is 1.6%. The resu ltant tensile and compressive strengths of the aerated slurry - infiltrated chicken mesh would be: = 0.56x0.016x310 + 5x2.5 = 27.604 MPa Figure 33 . ) required for calculating the nominal flexural strength: 27.604 xa = 2.75x (250 - a) a = 22.65 mm The flexural strength of the aerated slurry infiltrated chicken mesh can now be calculated as: = 0.56x0.016x310x100x(250 - 22.65)x (250/2) = 7893.59 N.m The nominal bending moment flexural strength of 7893.59 N.m exceeds the required flexural strength of 7,000 N.m by 8%. 65 Figure 34 a . shows the formwork with chicken mesh reinforcement placed in it. The slurry was simply poured onto the chicken mesh ( Figure 34 . ) to infiltrate the prep laced chicken mesh layers. After pouring of slurry, the frame was covered with plastic sheet to mitigate moisture loss. This allowed for curing at >95% relative humidity, that was achieved using the vapor released from the slurry during curing. The frame w as cured at ambient temperature for 14 days. ( a) Formwork with preplaced chicken mesh (b) Infiltration of chicken mesh with aerated slurry 4.2.5 Cyclic Testing The frame behavior was evaluated under quasi - static cyclic lateral loading. The test procedure involved application of reversed load cycles of progressively increasing lateral displacements until the first major event (FME), defined he re as yielding, occurred. Three reversed cycles of progressively increasing displacement amplitude were applied before the FME was reached. Subsequent loading followed the Sequential Phase Displacement (SPD) procedure which involves application of degrada tion and stabilization cycles at a constant displacement amplitude before progressing to the next phase with a greater displacement. The first cycle in a phase is applied with a larger displacement and is proceeded by three degradation cycles; subsequent a pplication of three stabilization cycles completes the phase. Stabilized response is achieved when the decrease in resistance between two successive stabilization cycles is less than 66 5% (Soudki, West et al. 1996) . If the decrease in resistance is more than 5%, additional stabilization cycles should be conducted. The frame tested in this study stabilized in five cycles. The procedure then moves on to th e next phase (Salenikovich, Dolan et al. 1999, Gatto and Uang 2003, Ibarra, Medina et al. 2005) . Cyclic testing of the frame was performed in accordance with ASTM E2126 Method A, that closely follows the SPD procedure developed by TCCMAR (Porter 1987) with few modifications . The SPD procedure is based solely on the First Major Event ( FME ) , where FME is defined as the displacement at which the structure starts to deform inelastically (anticipated yield displacement) (Krawinkler 2009) . ASTM E2126 , on the other hand, takes into account both FME and ductility ratio whe n determining the initial amplitude of each phase in the test protocol. In general, t he SPD protocol is displacement - controlled , and involves triangular reversed cycles at increasing displacement levels. The displacement increase in ASTM E2126 is based on FME and ductility ratio . The SPD procedure begins with at least three incremental levels of three cycles each, within the elastic displacement region up to the First Major Event (FME). The SPD method recommends 200% of the FME as the displacement increment for each phase in the case of ductile systems (Sale nikovich, Dolan et al. 1999, Gatto and Uang 2003) . The test protocol devised here, based on ASTM E2126 requirement comprised 15 steps of displacement increase, with trailing cycles after each peak cycle as shown Table 7 . 67 Load step Drift Peak Displacement, cm Trailing Cycle Displ. # of trailing cycles 1 0.050% 0.048 0.048 5 2 0.075% 0.072 0.054 6 3 0.100% 0.096 0.072 6 4 0.20% 0.192 0.144 3 5 0.3% 0.288 0.216 3 6 0.4% 0.384 0.288 3 7 0.7% 0.672 0.504 2 8 1.00% 0.960 0.720 2 9 1.50% 1.440 1.080 2 10 2.00% 1.920 1.440 2 11 2.50% 2.400 1.800 2 12 3.00% 2.880 2.160 2 13 4.00% 3.840 2.880 2 14 4.50% 4.320 3.240 2 15 5.00% 4.800 3.600 2 The column bases were fixed in an aerated slurry - infiltrated chicken mesh footing and installed on a reaction frame ( Figure 35 . ) for in - plane lateral cyclic loading per ASTM E564. A load cell and a displacement transducer were used to collect the load and displacement data, using a data acquisition system, under cyclic lateral loads. 68 4.3 Test Results and Discussion 4.3.1 Plastic - Hinge approach The frame failed by plastic hinge formation in the beam, as expected from the strong column - weak beam approach adopted for seismic design of the frame. Figure 36 . shows the plastic hinge formation in beam near the beam - column joint under repeated load cycles. The top part of the plastic hinge exhibited multiple cracking, while one crack formed at the bottom, which widened and connected to top cracks under cyclic deformations of growing amplitudes. 4.3.2 Hysteretic load - deflection curve The cyc lic load - deflection curve produced for the frame is presented in Figure 37 . together with the initial envelope (connecting the initial peak loads at the initial load achieved for each displacement) as well as the stabilized envelope (connecting the stabilized peak loads after repeated cycles at each deformation) (Dolan and Heine 1997) . The displacement cycles were unsymmetrical; this was forced by the s ize constraints of the reaction frame used in this test. The space available on one side of the frame was too small to allow for application of 69 symmetric cyclic deformations. Figure 38 a . and Figure 38 b . shows the average initial and stabilized envelopes, respectively, obtained by averaging the corresponding envelope curves produced in opposite displacement directions (Dolan and Johnson 1996, Dolan and Heine 1997) . Figure 37 . and Figure 38 . are indicative of a ductile behavior with desired hysteretic energy absorption capacity. These observations support the effectiveness of chicken mesh as a distributed reinforcement of high specific surface area in enhancing the toughness and energy dissip ation capacity of the cementitious matrix. 0 2 4 6 8 0 10 20 30 40 (a) 0 2 4 6 8 0 10 20 30 70 A comparative study was made of the behavior of the aerated slurry - infiltrated chicken mesh frame versus lateral load - carrying system of similar geometric attributes comprising either oriented strandboard (OSB) or hardwood subjected to comparable cyclic la teral loads (Toothman 2003) . Figure 39 . shows the average initial envelopes of these systems. The aerated slurry - infiltrated chicken mesh frame is observed to provide ductility levels comparable to those of lateral load - carrying systems based on OSB and h ardwood. The peak load - carrying capacity of the frame is more than those of systems based on OSB and hardwood; such comparisons, however, should also account for the weight of different systems. Figure 39 . Averaged initial envelope curves of the aerated slurry - infiltrated chicken mesh frame versus those of lateral load - carrying systems based on OSB and hardwood. 4.3. 3 Equivalent Energy Elastic Plastic ( EEEP) curve The envelope curves introduced above can be used, following the ASTM E2126 procedures, to derive the Equivalent Energy Elastic Plastic ( EEEP) curve that represents an elasto - plastic interpretation of the aerated slurry - infiltrated chicken mesh behavior. Th e EEEP curve encompasses the same order of magnitude area as the actual load - displacement curve (form the origin to the ultimate displacement). This area is a measure of the toughness of the system. 71 Toughness is defined here as the energy required to fail the structural system. The EEP curve shown in Figure 40 . incorporates a yield force(P yield yield ), u ), the area under the load - displacement curve, and the elastic stiff ness of the structural system. 4.3.4 Elastic Stiffness Figure 41 . shows the averaged initial and stabilized envelope curves of the slurry - infiltrated chicken mesh frame, and also the EEEP curve corresponding to the initial envelope curve. Elastic stiffness, k e , can be determined as the slope of the secant passing through the origin and the point on the load - displacement curve (or envelope curve) that is equal to 40% of the peak load, F peak . The slope of this line is used to locate the elastic portion of the EEEP curve. In addition, it is used to find other parameters such as the yield load, yield displacement, and the ductility ratio. (Kesner, Bill ington et al. 2003) 72 Elastic stiffness is a good indicator of the stiffness that a frame would exh ibit when subjected to low to moderate displacement s (Salenikovich 2000) . The elastic stiffness obtained using the initial envelo pe curve for the aerated slurry - infiltrated chicken mesh following the above p rocedure is shown in Figure 42 . and compared with later load resisting systems of comparable geometry made with OSB or hardwood sheeting. The elastic stiffness of the ae rated slurry - infiltrated chicken mesh is observed to be higher than those provided by alternative lateral load resisting systems 73 4.3.5 Failure load Following the ASTM E2126 procedures, failure load was calculated as 80% of the peak load. D isplacement at failure is another key parameter in assessing the seismic resistance of a lateral load - carrying system. The ability of a structure to dissipate energy arises partly from its ability to deform without failing (Park 1989, Salonikios, Kappos et al. 2000) . Table 8 . compares the failure load and the displ acement at failure of the aerated slurry - infiltrated chicken mesh frame versus alternative lateral load - resisting systems with comparable geometry which are made with oriented strandboard (OSB) and hardwood sheathing. The aerated slurry - infiltrated chicken mesh frame is observed to provide a relatively high failure load but lower displacement at failure when compared with the alternative systems. A review of the initial envelopes of these systems (see Figure 41 . , however, indicates that the overall ductility of the three systems is comparable, and the relatively low displacement at failure of the aerated slurry - infiltrated chicken mesh frame is a result of the approach ta ken by ASMT E2126 to define this displacement. 74 Lateral Load - Carrying System Failure Load, kN Displacement at Failure, mm Aerated slurry w/chicken mesh 5.54 32.26 OSB 3.11 83 .0 Hardboard 3.29 76 .0 4.3.6 Yield load and yield displacement Yield load is determined based on an approximation of the first major event, which is the theoretical load and displacement at which the structure starts to deform inelastically. F or the area under the load - displacement curve and the EEEP curve to be equal, the value of F yield is found where the area of the load - displacement curve equ als the area of the EEEP curve . T he area under the load - displacement curve (A) can be computed by integrating the initial envelope curve between x=0 to x=32.6 mm ( the failure disp lacement as presented in Table 9 . 6 where F yield = Yield Load (Kip, KN), A = the area (kip.in, KN.mm) under the load - displacement curve failure ), and k e = elastic Stiffness (kip/in, kN/mm). Once F yield is determined, the yield displacement can be calculated using the following relationship: Yi eld Displacement ( yield ) = 7 Parameter Numerical value A , mm 2 255.2 Ke , K N/mm 0.659 failure , mm 8.26 F yield , KN 5.445 75 4.3.7 Ductility Ductility is an important characteristic of a structural system, which reflects its ability to yield and deform in elastically without failure. The ability of structural member to bend but not fail is important exposure to sudden and powerful cycles of an i ntense earthquake . Different measures have been used to express the ductility of a structure . The most commonly accepted definition is that of displacement to the yield displace ment. The ductility ratio , derived from test results, is defined as the displacement at failure load divided by the displacement at yield load (Salenikovich, Dolan et al. 1999, Thomsen IV and Wallace 2004) 8 This value represents the relative displacement that a structure can undergo from yielding until failure . It reflects the ability of ductile structural systems to undergo further displace ments peak . When the structural component has reached its capacity, it transfers additional load onto other components. The ductility factor introduced above is the ratio of two displacements. If a structure undergoes large deformations before failure but has a large yield displacement, the structure is not necessarily a ductile system. The reverse is also true, so ductility should always be considered together with other performance indicators. Although ductility is an important characteristic, it should be noted that it is not a material property and caution should be used when comparing different structural systems. Given the variation s that exists when calculating the elastic stiffness and yield load, a large margin for error and inconsistent results may be encountered . 76 The ductility factor of structural systems comprising sheathing materials varies from 4 to 10 for both OSB and hardboard (Toothman 2003) , compared to a ductility factor of 10.9 calculated for the aerated slurry infiltrated chicken mesh frame using Equation (8). The higher elastic stiffness of the frame tends t o reduce its yield displacement, which raises the calculated value of ductility. These results point at the ductile behavior of the aerated slurry - infiltrated chicken mesh frame, and its ability to yield and undergo inelastic deformation to dissipate the i nput energy of severe earthquake ground motions. 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Advances in Structural Engineering, 2017. 20(4): p. 629 - 640. 82 CHAPTER 5 : EVA LUATION OF THE ENERGY - EFFICIENCY OF AN AERATED SLURRY - INFILTRATED MESH BUILDING SYSTEM WITH BIOMASS - BASED INSULATION This chapter was first published as " Evaluation of the Energy - Efficiency of an Aerated Slurry - Infiltrated Mesh Building System with Biomass - Based Insulation." Almalkawi, Areej T., Parviz Soroushian, and Som S. Shrestha. Renewable energy 133 (2019): 797 - 806. 5.1 Introduction Beneficial use of thermal mass is an important consideration in design of climate - adapting sustainable buildings ( Park 2015, Karol 2017, Ramakrishnan, Wang et al. 2017) . The growing need for energy - efficient buildings with optimum thermal comfort has increased the reliance on thermal mass to meet these requirements (Perino and Serra 2015, Stazi, Bonfigli et al. 2015) . Construction of buildings with heavier materials, including concrete and masonry, used within the insulation system, leads to reduced temperature swing in the indoor temperature (Zhu, Hurt et al. 2009) . The high thermal inertia of such buildings allows for effective radiant heating in winter, and reduces the chance of indoor overheating in summer (Navarro, de Gracia et al. 2016, Johra and Heiselberg 2017, Lydon , Hofer et al. 2017) . Building systems with high thermal mass, on the other hand, require more time to cool down or heat up. This f eature could translate into thermal discomfort; more energy could also be used for heating and cooling to compensate for this effect (Hoes, Trcka et al. 2011) . There are thus conditions where buildings constructed with lighter materials (e.g., wood) can offer improved thermal performance when compared with heavier buildings (Hoes and Hensen 2016, Johra and Heiselberg 2017) . Opting for an effec tive amount of thermal mass is always critical, and depends on a number of factors, including climatic 83 conditions, occupancy patterns, internal heat gains, building orientation, and types of mechanical devices (Gelegenis and Axaopoulos 2017, Rehman 2017) . These factors should be considered integrally with the thermal mass and insulation requirements to minimize the overall energy demand and maximize the thermal comfort of the building inter ior (Hoes, Trcka et al. 2010, Hoes and Hensen 2016) . The availability of new building materials offer more options to address this challenging issue. Examples include hollow block walls, ventilated slabs (Ren and Wright 1998) , phase change materials (PCM) (Zhou, Zhao et al. 2012) , dynamic insulation systems (Imbabi, Elsarrag et al. 2012) , and ultra - light - weight concrete (ULWC) (Roberz, Loonen et al. 2017) . The investigation reported herein covers the thermal aspects of developing a new building material, referred to as aerated slurry - infiltrated mesh, which is focused on maximum use of locally available materials (including insulation materials) towards development of sustainable, structurally safe and energy - efficient buildings. T his building system offers an intermediate thermal mass, which occurs between those of wood and concrete building systems. The thermal mass provided is selected primarily based on structural requirements, and should be supplemented with proper indigenous i nsulation levels for realizing desired energy - efficiency and thermal comfort (Devi and Palaniappan 2014) . The selection of thermal insulation must satisfy many criteria, including energy performance , economics, environmental impacts, and compatibility with structural design. This work covers measurement of the insulation qualities of aerated slurry - infiltrated mesh and biomass - based insulation materials. The results are used, together with the struc turally governed mass of the building, to identify the insulation conditions which yield desired thermal performance. 84 5.2 Experimental Evaluation of Insulation Qualities 5.2.1 Materials 5.2. 1.1 Aerated Slurry The aerated slurry had a water/cement ratio of 0.6; a foaming agent was used at different dosages to produce hardened material bulk densities ranging from 0.65 to 1.15 g/cm 3 (in oven - dried condition). The aerated slurry was prepared by first mixing a foaming agent (saponin) with the mixing water for 6 minutes, using a drill with a blade attached to it and operated at a rotational speed of 1200 rpm ( Figure 43 a . ) . The resulting foamed mixing water was then added to cement and mixed for 12 minutes in a planetary mortar mixer ( Figure 43 b . ) to produce a homogeneous aerated slurry. (a) Mixing of the foaming agent with water (b) Mixing of foamed water with c ement The thermal conductivity test specimens ( Figure 44 . ) were in the form of thin circular plates. They were molded and consolidated under external vibration, demolded after 24 hours of storage in sealed condition, and then cured at >95% relative humidity) and room temperature to reach 7 days of age. The specime ns were then oven - dried for 24 hours at 105±5 o C, weighed for evaluating their bulk density, and subjected to the thermal conductivity experiment. 85 5.2. 2 Biomass - Based Insulation Materials Three categories of biomass - based insulation were used in this investigation: (i) ground wood; (ii) shredded straw; and (iii) a commercially available blow - in cellulose insulation. These three insulation materials are described in the following. The thermal conductivity test specimens of different biomass - based insulation materials had the same geometric attributes as the aerated slurry thermal conductivity test specimens. 5.2. 2 .1 Ground Wood Insulation Wo od branches collected locally (in air - dried condition) were ground using a hammer mill ( Figure 45 ). The ground wood was passed through a sieve with 2.36 mm opening. Figure 46 . shows the appearance of the resulting ground wood insulation. While the ground wood insulation was used without any treatment, mitigation of microbial degradatio n ay require their treatment. Figure 47 . shows the particle size distribution of the ground wood insulation. The median particle size was about 0.8 mm, with particles ranging in size from 0.3 to 0.5 mm. The loosely packed ground wood had a bulk density of 0.291 g/cm 3 . 86 87 5.2. 2 .2 Shredded Straw Insulation Wheat straw was shredded in the hammer mill shown in Figure 48 . This mill is Type MUR manufactured by the American Pulverizer Co.; it has a 10 mm diameter sieve installe d on it. The visual appearance of the resulting shredded straw insulation is presented in Figure 49 . The length distribution of shredded straw is presented in Figure 50 . Most straw fibrils are noted to be less than 1.5 mm in length. The loosely packed shredded straw insulation provided a bulk density of 0.069 g/cm 3 . Figure 48 . The hammer mill used for shredding of straw . 88 5.2. 2 . 3 Commercially Available Cellulose The commercially available cellulose (Green Fiber) insulation used in this investigation Figure 51 . - According to the manufacturer, this insulation would provide a thermal conductivity of 0.042 W m - 1 K - 1 at 25 o C when packed loosely with a bulk density of 0.056 g/cm 3 . The cellulose insulation was used in this investigation at the d bulk density of 0.056 g/cm 3 , and in loosely and densely packed conditions with bulk densities of 0.068 and 0.034 g/cm 3 , respectively. 89 5.2. 3 Thermal Conductivity Test Method Thermal conductivity measurements were made using a test setup Figure 52 . manufactured by Holometrix GHP that meets the ASTM C177 requirements. In this test, two similar specimens are placed between a middle hot plate and two outside cold plates. The hot and cold p lates were typically kept at constant 30 o C and 20 o C temperatures, respectively, to represent the outdoor and indoor temperatures. The effects of temperature on the thermal conductivity of different insulation materials was also investigated. Temperatures o n the hot and cold plates as well as the heat flow were monitored over a 24 - hour time period. The results, after the processed reached equilibrium, were used to calculate the thermal conductivity of test specimens. (a) Picture ( b) Schematic The thermal conductivity test specimens used in this experimental work were circular plates of 195 mm diameter and 25.4 mm thickness. They were produced by containing the loose 90 insulation materials within a ring fabricated using a flexible polypropylene sh eet of 1 mm thickness ( Figure 53 . ) The ground wood, shredded straw and commercially available cellulose insulation test specimens are shown in Figure 54 . (a) Ground wood ( b) Shredded straw (c) Cellulose 5.2.4 Thermal Conductivity Test Results The measured values of thermal conductivity for the ground wood, shredded wheat straw and cellulose (0.056 g/cm 3 bulk density) insulation materials were 0.0516, 0.0379 and 0.0389 W/m.K, respectively Figure 55 . The indigenous insulation materials (ground wood and shredded straw) thus provide insulation qualities that are of the same order of magnitude of that provided by the commercially available cellulose insulation. The bulk density and thermal conductivity o f 91 shredded straw and cellulose were comparable. Ground wood with a higher bulk density provided a higher level of thermal conductivity. 92 The effects of temperature on the thermal conductivity of the biomass - based loose insulation materials were also investigated Figure 57 . In this series of tests, the temperature difference of hot and cold plates was kept constant at 10 o C; the effects of the mean temperature ( of hot and cold plates) on thermal conductivity were investigated. Thermal conductivity is observed to increase with increasing temperature; this effect is less pronounced in the case of the ground wood insulation. Conductive, convective and radiative heat transfer are influenced differently by temperature (and temperature gradient). The trends in temperature effects on thermal conductivity depend, among other factors, on the pore size of insulation materials (Shrestha, Desjarlais et al. 2014) . The observed rise in thermal conductivity with increasing temperature is not unusual for insulation materials with multi - faceted heat transport mechanisms. 93 The thermal conductivity test results for aerated slurries of different bulk densities are presented in Figure 58 . The pore system in aerated slurry comprises isolated individual pores. Convective heat transfer can thus occur only within pores (and not between them). Given this condition, and since the ce mentitious binder is thermally more conductive than air, replacement of air with the cementitious matrix in aerated slurries of higher densities would produce higher thermal conductivities. 94 5.3 Thermal Simulation and Design of the Building System A simple aerated slurry - infiltrated chicken mesh building designed to meet structural requirements was subjected to thermal analysis in order to evaluate its insulation requirements. The building planar dimensions are 4.9 m x 9.8 m, and its height is 2.4 m. The building structure ( Figure 59 . ) comprises nine aerated slurry - infiltrated chicken mesh frames of 0.75 g/cm 3 bulk density to which external wall, internal wall all, roof and ceiling aerated slurry - infiltrated chicken mesh sheets are screwed. The floor also comprises aerated slurry - infiltrated chick en mesh sheets, which span the frame footings and are supported on compacted sand. All (roof, ceiling, wall and floor) sheets have a bulk density of 0.75 g/cm 3 . The interior and exterior sheets are 19 and 25.4 mm thick, respectively. 95 5.3.1 Thermal Simulation of the Building System 96 Design Factor Value Location Amman - Jordan Latitude (degree) 31.87 Longitude (degree) 35.22 Time zone (h) 2 Elevation (m) 757 People per zone floor (Based on 1.4 m 2 per person = 34 persons per 48 m 2 ) Occupancy schedule Office schedule Lighting Lighting schedule Office light Lighting power density (w/m 2 ) 8.6 Electric equipment Electric equipment power density (w/m 2 ) 10.8 Outdoor Air per person ((m 3 /min)/person)) 0.142 Outdoor air per area ((m 3 /min)/m 2 )) 0.060 Infiltration rate (ACH) 0.8 Based on the test data introduced earlier, the thermal properties of the aerated slurry and the biomass insulation used in thermal analysis of the building are presented in T able 11 . This table also presents typical thermal properties of plywood which is used as the control material used in construction of the conventional alternative to the building system considered here. 97 Material (bulk density, g/cm 3 ) Thermal Conductivity, (W/mK) Specific Heat, Cp (J/(kg.K)) Aerated Slurry (0.75) 0.31 870 Biomass Insulation (0.056) 0.039 840 Plywood - CDX (0.54) 0.12 1215 The thermal analysis investigate the effects of the thermal insulation levels of walls, roof and floor on the energy use of the building. Comparative analyses were also performed on the new building system versus a conventional wooden alternative to this s ystem. 5.4 Results and Discussion 5.4.1 Energy Consumption The building system comprises interior and exterior aerated slurry - infiltrated mesh walls, with biomass insulation placed in between the two sheets. Figure 62 . shows the effects of the wall insulation (with roof and floor insulation kept constant) on the annual heating and cooling loads of the building. Beyond an R - value (US) of 20 wall insulation, increasing the insulation level does not reduce the heating and cooling loads of the building. Below this level of insulation, gains in the energy - efficiency of the building can be realized by adding to the wall insulation. The thickness of the biomass insulation with 0 .039 W/mk thermal conductivity required to provide this level of wall insulation is 0.137 m (13.7 cm). Structural design requirements provide more than adequate spacing between exterior and interior wall sheets to place this level of biomass insulation. 98 Figure 62 . Effects of the wall insulation on the cooling and heating loads of the building (RSI (K.m2/W) = R - value (US) (ft2.oF.hr/Btu) /5.68). The effects of roof insulation level on the annual heating and cooling loads of the building are presented in Figure 63 . The heating and cooling loads are observed to d ecrease with increasing roof insulation up to an R - value (US) of 10, beyond which the benefits of further increasing the roof insulation level are minimal. A biomass insulation thickness of 6.85 cm would provide this required level of insulation. The cavit y between the roof and ceiling sheets, decided based on structural requirements, is more than adequate for providing this level of insulation. The floor of the building system comprises an aerated slurry - infiltrated chicken mesh supported on 20.3 cm of compacted sand which provides a thermal conductivity of about 0.3 99 W/mK. The effects of the floor insulation levels on the annual heating and cooling loads presented in Figure 64 . indicated that the heating and cooling energy consumption of the building decrease with increasing floor insulation up to about an R - value (US) of 4, beyond which the effects of further increasing the floor insulation level on the building energy use is minimal. Considering the insulation level provided by the aerated s lurry - infiltrated chicken mesh sheet, 21 cm of compacted sand would be required under the floor sheets. Consideration of the insulation value of the aerated slurry - infiltrated chicken mesh floor sheets would reduce the required thickness of the compacted s and acting as insulation to 19 cm. The available compacted sand thickness of 20.3 cm is thus adequate for providing the required level of floor insulation. 5.4.2 Optimization of the Wall Insulation Condition Heat loss from the building that is subject of this investigation occurs largely via trans fer of heat through exterior walls in winter, noting that these walls constitute the largest surface area of the building envelope (Friess and Rakhshan 2017, Siddiqui, Kumar et al. 2017) . An investigation was conducted to assess the optimum wall insulation condition, f ocusing on heat loss through walls (Al - Sanea, Zedan et al. 2005, Kaynakli 2011) which minimizes the cost of 100 meeting the energy demand of the building (Aditya, Mahlia et al. 2017) . Figure 65 . shows the effects of the wall insulation level on the energy use cost, the insulation cost, and the total cost. The total cost is observed to be minimized at wall in sulation levels ranging from R - value (US) of 5 to 8, which correspond to biomass insulation thicknesses occurring within the 3.4 to 5.5 cm range. 5.4.3 Comparison with a Conventional Wood Building While the aerated slurry - infiltrated mesh building structure is developed to be lightweight, it still weighs more than a conventional building system with wood structure. The thermal mass of the aerated slurry - infiltrated mesh building would thus be larger than that of a wood building. A larger thermal mass generally reduces the energy demand of a building, and favorably influences thermal comfort (Kosny, Petrie et al. 2001) . Thermal time constant (TTC) is a thermal attribute of building envelopes that incorporates thermal mass. TTC is defined as the heat stor ed in the whole envelope (including internal air) per unit of heat transmitted to or from the outside through the elements surrounding the enclosure and by ventilation (Naji, Çelik et al. 2014, Wang 2015) . It is the product of heat cap acity (Q) and thermal resistance (R). TTC provides 101 an indication for the effective thermal capacity of a building. A shorter value of TTC indicates that a smaller heat flux would be required to achieve a unit change in temperature. A longer TTC value, on t he other hand, suggests that the high thermal inertial of the building suppresses indoor temperature fluctuations. The value of heat capacity per unit area (Q A , J/m 2 .K) can be calculated as follows (Athienitis and Santamouris 2013) : where, is the material density (kg/m 3 ), d is the thickness of the material (m), and c p is the specific heat of the material (J/kg.K). In calculating TTC A (TTC per unit area, seconds) of a composite wall, the Q A .R value of each layer, including the outside and inside air layers, is calculated in sequence: where, , and n is the number of layers. The value of TTC for each surface is the product of TTC A and the surface area. Surfaces of higher TTC value reflect further benefits that can be realized from thermal mass (Liping and Hien 2007, Al - Sanea, Zedan et al. 2012) . For the walls ( Figure 66 . ) of the building system designed with aerate slurry - infiltrated mesh, the value of TTC A was 13% larger than that designed with plywood (CDX). The total cooling and heating energy demands of the two building systems over a 12 - month period are presented in Figure 67 . and Figure 68 . respectively. The aerated slurry - infiltrated mesh building is observed to be more energy - efficient than the wood building, which can be largely attributed to its larger thermal mass. 102 103 5.5 Conclusions Experimental and numerical investigations were conducted towards development of a building system that can be constructed using locally available structural and insulation materials. The structural material used here is referred to as aerated slurry - infiltrated mesh. The insulation materials are biomass - based, and include ground wood, shredded straw, and cellulose. The following conclusions were derived based on the experimental and numerical data generated in this work 1. 2. 3. 104 4. 5. 6. 105 REFERENCES 106 REFERENCES Aditya, L., et al., A review on insulation materials for energy conservation in buildings. Renewable and Sustainable Energy Reviews, 2017. 73: p. 1352 - 1365. Al - Sanea, S.A., M. Zedan, and S. 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Stazi, F., et al., The effect of high thermal insulation on high thermal mass: Is the dynamic behaviour of traditional envelopes in Mediterranean climates still possible? Energy and B uildings, 2015. 88: p. 367 - 383. 108 Wang, Y., Optimization for Building Control Systems of a School Building in Passive House Standard. 2015, Universität München. Yezioro, A., B. Dong, and F. Leite, An applied artificial intelligence approach towards assessing building performance simulation tools. Energy and Buildings, 2008. 40(4): p. 612 - 620. Zhou, D., C. - Y. Zhao, and Y. Tian, Review on thermal energy storage with phase change materials (PCMs) in building applications. Applied energy, 2012. 92: p. 593 - 605. 109 CHAPTER 6 : AERATED CEMENT SLURRY AND CONTROLLING FUNGAL GROWTH OF LOW - COST BIOMASS - BASED INSULATION MATERIALS This chapter was first published as Almalkawi, A. T., & Soroushian, P. (2019). Aerated cement Slurry and controlling fungal Growth of Low - cost Biomass - Based insulation Materials. Scientific Reports, 9(1), 1 - 10 . 6.1 Introduction Biomass ash - based insulation in the form of wood chips or groun d wood offers desired thermal insulation qualities complemented with low cost, ready availability, and favorable ecological features. There are, however, concerns with the resistance to fire, moisture and fungus growth of such insulation. The work reporte d herein focuses on improvement of the resistance to fungus growth of low - cost biomass - based insulation comprising largely of wood chips or ground wood. Fungal proliferation inside buildings can have adverse effects on the health of building residents (Nevalainen and Seuri 2005, Portnoy, Kwak et al. 2005, Lee, Grinshpun et al. 2006) ; it can also cause discoloration and degradation of construction (Ezeonu, Price et al. 1994, Murtoniemi, Hirvonen et al. 2003, Klamer, Morsing et al. 2004) . Mold growth on conventional insulation materials is habitually related to moisture occurred fro m flooding, water condensation or plumping leaks . (Nielsen, Holm et al. 2004) . Many research investigations have addressed the impact of dampness level o n the tendency of construction materials to mold growth (RAUTIALA, KASANEN et al. 2000) . At relatively low levels of humidity, fungi do not tend to inoculate on the surfaces of building materials (Yang and Clausen 2007) . Relative humidity levels of 70% to 90% 110 are sufficient to trig ger fungal augmentation on construction materials (Haas, Habib et al. 2007, Viitanen, Vinha et al. 2010) . Besides the relat ive humidity of the environment, the water holding capacity (WHC) and/or the equilibrium moisture content (EMC) of a particular building material are also important indicators of the potential for fungal growth on a material exposed to humid conditions Building materials that are popular for indoor (and other) applications. Green indoor products are often promoted for low - emission, low - toxicity and recyclability attributes (Spiegel and Meadows 2010, Huang and Wang 2014, Kibert 2016) . These qualities contrast those of the highly popular reconstituted wood products (e.g., or iented strandboard OSB) used in interior building applications that are fabricated with such adhesives as urea formaldehyde that release harmful emissions and are prone to fungal growth. Reconstituted wood products have realized their current prominence because they can make value - added use of wood strands/fibers/particles that are abundantly available at low cost. The work reported herein concerns the use of low - cost and abundantly available wood flakes or ground wood as insulation materials in building construction. These low - cost and abundant products would be viable as insulation materials as far as they complement viable insulation qualities with desired resistance to fungal growth as well as moisture and fire. The work reported herein concerns the i nsulation attributes and the resistance to fungal growth on wood flakes and ground wood. Low - cost treatment methods are also developed for achieving improved resistance to fungal growth. 111 Bio - based materials have been used in construction for centuries 46 . T hey can exhibit desired durability and may deteriorate under the action of microorganisms such as fungi and bacteria. The activity of such microorganisms depends mainly on environment factors (relative humidity and temperature), and also on the building ma terial (substrate) characteristics such as hygroscopicity (Schmidt 2006, Yang and Li 2007) . Bio - based materials may hold a potential source of nutrients for fungal and bacterial activity. Under similar environmental conditions, different bio - based materials may be affected differently by mold growth (Palumbo, Navarro et al. 2015, Palumbo, Lacasta et al. 2017) . Their resistance against mold growth decides their suitability for construction application. This property is usually assessed in the critical moisture content that is amenable to fungal growth (Sedlbauer 2001, Brischke and Thelandersson 2014) . Resistance of materials to mold growth can be enhanced by the addition of biocides. Boric acid and deri ved salts (borates) are widely used as biocide along with commercial insulation materials such as blowing cellulose (Palumbo Fernández 2015, Palumbo, Lacasta et al. 2017) . Such substances have the dual - action as a biocide and as a fire retardant; they are viewed as a greener alternative to metal - based fungicides (Hernandez - Torres, Chen et al. 2017) , commonly considered in wood preservation; their toxicity is, however, scrutinized nowadays (Fernández - . Another approach is the use nonbiocidal techniques for protection against fungi (Morrell 2017, Palumbo, Lacasta et al. 2017, Winandy and Morrell 2017) . Bio - based insulation materials can be impregnated with water repellents, such as waxes (Frenkel 2017) , or pretreated to reduce their hygroscopicity (Essoua, Beauregard et al. 2017, Li, Ye et al. 2017) . This work evaluated the 112 effectiveness of impregnating bio - based thermal insulation materials with aerated cement slurry in order to improve t heir resistance to fungal growth in different humidity conditions. 6.2 Materials 6.2.1 Wood Particles Wood branches collected locally (in air - dried condition) were ground using a hammer mill. The resulting wood particles were passed through a sieve with 2.36 mm opening . Figure 69 . shows the appearance of the fine wood particles which were evaluated as insulation material. While these fine wood particles could be used for thermal insulation without any treatment, mitigation of microbial degradation would be a concern. Figure 70 . shows the particle size distribution of the fine wood particles using sieve analysis method. The median particle size was about 0.8 mm, with particles ranging in size from 0.3 to 2.36 mm. The loosely packed fine wood particles had a bulk density of 0.291 g/cm 3 . 113 6.2.2 Wood Chips Wood chips with less than 25 mm particle size ( Figure 71 . ) were also considered as sustainable insulation materials. The particle size distribution of these wood chips is presented in Figure 72 . The bulk density of these wood chips was 0.205 g/cm 3 . 114 6.2.3 Shredded Straw Shredded wheat straw ( Figure 73 . ) with the length distribution shown in Figure 74 . was also used in this investigation. The bulk density of shredded straw was 0.610 g/cm 3 . 6.2.4 Treatment of Biomass with Aerated Slurry An aerated cement slurry was used for pretreatment of fine wood particles, wood chi ps and shredded straw in order to improve the resistance of biomass to fungal growth without imposing major weight penalties. The aerated slurry was prepared at a water/cement ratio of 0.6, with saponin used as the foaming agent. Saponin was first added to the mixing water and stirred at a rotational speed of 1,200 rpm to produce a stable foam. The foamed water was then mixed with cement in a planetary mixer over 12 minutes to produce a homogenous aerated slurry; the dosage of the foaming agent (saponin) wa s adjusted to produce (after curing and oven - 115 drying of slurry) a bulk density of 0.75 g/cm 3 . Physical and mechanical properties of aerated slurry cement were studied in our previous works (Almalkawi, Hamadna et al. 2017, Almalkawi, Sa lem et al. 2018, Almalkawi, Hong et al. 2018, Almalkawi, Hong et al. 2018, Almalkawi, Soroushian et al. 2019) . The aerated slurry was added to fine wood particles, wood chips or shredded straw at an aerated slurry - to - biomass weight ratio of 0.2 in a drum mixer. Figure 75 . shows wood chips after treatment with aerated slurry. This treatment raised the bulk density of wood chips, finer wood particles and shredded straw from 0.291 to 0.295, from 0.205 to 0.214, and from 0.610 to 0.627, respectively. The thermal conductivities of find wood particles and wood chips measured, prior to an after treatment with aerated cement slurry, are summarized in Table 12 . When compared with the thermal conductivities of commercially available thermal insulation materials such as expanded polystyrene (Styrofoam), that is 0.033 W/m.K, fine wood particles and wood ch ips are observed to provide reasonable low thermal conductivities for use as thermal insulation in building construction. The thermal conductivity of shredded straw was more than three times those of fine wood particles and wood chips, which could be due t o convective heat transfer of loose straw. Treatment of wood straw with aerated slurry slightly reduced its thermal conductivity, which could be due to a slight reduction in the convective heat transfer. This trend 116 was opposite of that observed with fine w ood particles and wood chips, which experienced a slight rise in thermal conductivity after treatment with aerated slurry. Specimen Thermal conductivity, W/m.K Fine wood particles 0.0516 Fine wood particles (treated) 0.0535 Wood chips 0.0638 Wood chips (treated) 0.0587 Shredded straw 0.196 Shredded straw (treated) 0.189 6.3 Methods 6.3.1 Water - Holding Capacity The water - holding capacity of the insulation materials was measured by keeping triplicate samples (container sized 4 cm cube) in water as submerged condition t ill the saturation for flooding simulation purposes. The maximum water - holding capacity (WHC, %) of the samples was expressed as the mass ratio of water to dry materials in Equation. where, M initial is the initial weight of air - dr ied sample (g), and M final is the weight of fully saturated sam ple (g). T he mean and standard deviation values were computed for a ll triplicated samples . 6.3.2 Equilibrium Moisture Content The equilibrium moisture content of the insulation samples was measured according per ASTM C1498 - 04a (2004) and ASTM D2216 - 05 (2005). Samples of insulation materials (5 cm cube) were dried initially at 10 5 °C to reach a constant mass. Triplicate d insulation materials kept in 117 sealed condition in 48 L stainless - steel chambers with relative humidity (70%) and temperature ran ge of (22 - 25 o C). A constant air exchange rate of 1 h - 1 was maintained and passed through the chamber at relative humidity of 70%. The weight of each specimen was monitored over regular intervals for constant mass observation, the equilibrium moisture cont ent was determined per the equation : where, EMC is the equilibrium moisture content (%); where, M initial is the initial weight of air - dr ied sample (g) and M final is the weight of sample at equilibrium condition with the water vapor in air inside the chamber (g). the values averaged for a ll triplicated measurements . 6.3.3 Artificial Inoculation The aim of this investigation was to testify the vulnerability of insulation materials to augmentation by a model fungal species subjected to different nutrient sources at favorable temperature and humidity ranges . Aspergillus niger was chosen as the ideal fungus type for this indoor environment condition (Rao, Burge et al. 1996, Bartlett, Kennedy et al. 2004, Lee, Grinshpun et al. 2006) . The A. niger strain was obtained from the American Type Culture Collection (Rockville, MD, USA) with designed number (ATCC 9642). Development of spore (conidia) inocula was conformed per the ASTM G21 - 96 . A spore suspension was stimulated by augmenting the fungi for two weeks on V8 agar culture . 5 ml of a based wetting - agent solution (0.2% NaNO 3 , 0.05% KCl , 0.03% K 2 HPO 4 , 0.05% MgSO 4 , 0.02% KH 2 PO 4 , 0.01% Tween 80 , 0.001% FeSO 4 ,) was poured in Petri dish, and the culture were kindly moved to a sterile bottle. The insulation materials were artificially inoculated by spraying 0. 4 ml of suspension solution onto 118 the specimens . The confined Petri dis hes ( Figure 76 . ) holding the wetted and inoculated materials were kept in a sterile bench at incubat ion conditions 2 5 o C for 28 days. To evaluate the potential of fungal growth, the insulation materials were moisturized to three levels: ambient level , simulated rain, and the water holding capacity (WHC) l evel. The ambient moisture condition reached by subjecting the materials to 2 2 C and 3 4 - 40% relative humidity for 24 hours. Simulated rain was produced by showering the specimens for 5 minutes with approximately 530 ml water followed by drying for 24 hour and 35 - 40% relative humidity. This process produced a moisture condition that in - between ambient and WHC and simulated at the same time an accidental wetting throughout construction building . The WHC condition was achieved by storing the samples in water for two days . The weight gain of Fungi A. niger was monitored over the inoculation period. They exhibited rapid weight from 4 to 8 days in nutrient medium, after which they reached the stationary phase of incubation Figure 77 . ) 119 Fungal growth on different insulation materials was visually detected on a weekly basis following the ASTM C1336 (96) procedures. Microscopic inspections were made when fungus growth was noted; the amount of growth was classified in categories using the following scale (Figure 77.) : No growth noticed microscopically 0 Microscopical cultivation existence 1 Microscopical cultivation coating all surface 2 Macroscopical (visible to naked eye) cultivation existence 3 Macroscopical cultivation covering 75% of the surface 4 An image processing tool (image J software) developed by the U.S. National Institutes of Health (NIH) was used to determine the surface area of the entire sample (A s ) an d that of the area contaminated with fungal growth (A c ) (Abràmoff, Magalhães et al. 2004, Wijekoon , Goodwin et al. 2008, Schindelin, Arganda - Carreras et al. 2012) . The percentage of the surface covered by fungal growth (P c ) was calculated as (Ac/As x100) and was plotted versus the incubation time for 120 each insulation material. The fungal growth rating was confirmed by microscopic observation (20x) and with the aid of a digital image (taken by a 16 MP Samsung camera). 6.4 Results and Discussion 6.4.1 Water uptake The equilibrium moisture content (EMC) test results at 85 - 92% relative humidity and 20°C temperature were presented in Figure 79 . EMC reflects a dynamic equilibrium, and changes with the relative humidity and temperature by the surrounding air. The EMC of the wood - and straw - based insulation materials ranged from 5 to 6%. Treatment of wood chips with aerated slurry reduced their e quilibrium moisture content by about 50%. Moisture contents exceeding 18% would encourage growth of fungi which were present in wood and straw as spores and may below 18%, fungi become dormant. If the moisture content exceed ed a certain level, fungi may grow exponentially . 121 6.4.2 Visual and Microscopic Observations Vis ual inspections were made to evaluate the susceptibility of bio - based insulation materials to fungal growth. An example of visually notable fungal growth on the biomass insulation materials was presented in . (a) Untreated wood straw prior to (left), and 21 days after introduction of fungi (right) 122 The test data summarized in . Average value of growth visible on surface of insulation m aterials 1 Week 2 Week 3 Week 4 Week Amb Rain WHC Amb Rain WHC Amb Rain WHC Amb Rain WHC Untreated Wood Chips 0 0 0 0.5 1 1 0 1.5 2 2 3 2 Untreated Shredded Straw 0 0 0 0.5 1 1 0 1.5 2 2 3 2 6.4.3 Optical microscope Optic al microscope examination of treated wood chips ( Figure 82 a . ) and treated shredded straw ( Figure 82 b . ) after 4 weeks of exposure in ambient condition confirmed that treatment with aerated slurry was effective in mitigating fungal growth on these biomass insulation materials. For untreated wood chips and untreated shredded straw ( Figure 82 d . ), on 123 the other hand, fungal colonization on surfaces was obvious under similar exposure conditions. Similar trends have been reported for cement - bonded wood particleboards made with eucalypt and ryber wood particles (Okino, De Souza et al. 2004) . 6.4.4 Natural Inoculation Figure 83 . show ed the percent of surface area covered by fungal growth versus incubation time following natural inoculation with A. niger fungi. When un treated wood chips were subjected to high humidity prior to incubation, fungal growth was observed within the first week of incubation. When exposed directly to water, fungal growth on untreated wood chips occurred after a lag period of 25 days. This lag p eriod can be explained by: (i) the need for moisture content 124 to drop below a threshold level required to support fungal growth; and (ii) washing away of some naturally inoculated fungi during the submersion period. Fungal growth did not occur on treated wo od chips irrespective of the pre - exposure to high humidity or directly to water. (a) High humidity exposure (b) Direct water exposure The effectiveness of aerated slurry treatment as an effective means of mitigating fungal growth on the biomass ash - based insulation c ould be attributed to: (i) coating of biomass and filling of its pores with aerated slurry, which produces a physical barrier against access of fungi to biomass; (ii) the relatively high pH of aerated cement slurry (pH= 11) ; and (iii) the amenability of the pa rtially cured aerated slurry to further curing upon exposure to moist conditions. 6.5 Conclusions Wood chips and particles as well as shredded straw are low - cost and abundantly available materials with desired thermal insulation qualities. Fungal growth on wood and straw in humid environments, however, is a concern. An experimental investigation was conducted in order to assess the merits of a simple and low - cost method of treating wood chips/particles and straw for control of fungal growth without while re taining their desired thermal insulation quality without 125 imposing a weight penalty. The following conclusions were derived based on the test data generated in this investigation. 1. 2. 3. 126 REFERENCES 127 REFERENCES Abràmoff, M. D., Magalhães, P. J. & Ram, S. J. Image processing with ImageJ. Biophotonics international 11, 36 - 42 (2004) Almalkawi, A. et al. Physio - Microstructural Properties of Aerated Cement Slurry for Lightweight Structures. Materials 11, 597 (2018). Almalkawi, A. T. et al. Mechanical properties of aerated cement slurry - infiltrated chicken mesh. Construction and Building Materials 166, 966 - 9 73 (2018). Almalkawi, A. T., Hamadna, S. & Soroushian, P. One - part alkali activated cement based volcanic pumice. 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Almalkawi, Areej T., Sameer Hamadna, and Parviz Soroushian Construction and Building Materials 152 (2017): 367 - 374. 7.1 Introduction - alkali activated binders are synthesized via alkali - activation of solid aluminosilicate feedstocks (e.g., metakaolin, coal fly ash and ground granulated blast furnace slag) with highly alkaline solutions (e.g., sodium silicate and sodium hydroxide) (Alonso and Palomo 2001, Lee and Van Deventer 2002, Lecomte, Liégeois et al. 2003, Duxson, Fernández - Jiménez et al. 2007, Kong, Sanjayan et al. 2007, Andini, Cioffi et al. 2008, Bernal, Rodríguez et al. 2012, Heah, Kamarudin et al. 2012, Lizcano, Gonzalez et al. 2012, Deb, Nath et al. 2014) . These two - part alkali activated binders, comprising largely of alkali aluminosilicate hydrates, offer important advantages over alternative cementitious binders in terms of sustainability, thermos - m echanical performance and chemical stability. The two - part nature of alkali activated binders, however, challenges their transition to mainstream construction applications. The need to handle highly caustic solutions, and the requirement to mix these caust ic solutions (in lieu of water) with solids constitute setbacks in their large - scale implementation. - formulations which, upon addition of water, undergo hydration reactions which yield the desired alkali aluminosilicate hydrate structure of conventional alkali activated binders (Hajimohammadi, 132 Provis et al. 2008, Hajimohammadi, Provis et al. 2010) . These efforts can be categories into two groups: (i) heat treatment of th e blend of raw materials (aluminosilicate precursor and alkalis in solid form) to yield a compounded and activated hydraulic cement; and (ii) simple blending of the raw materials in dry form. The second category, however, may not be a viable option because - affinity of alkalis for the humidity in air. The first gro up, which seems to be more viable, requires input of relatively high thermal energy to bring about compounding and activation effects; this energy consumption, however, compromises the sustainability of the resultant hydraulic cements. The long - term durabi - (Muntingh 2006, Provis and Van Deventer 2009, Van Deventer, Provis et al. 2012) . The primary focus of the work reported herein was on development of one - part alkali activated cements formulated with natural volcanic tuff as aluminisilicate precursor (Areej Almalkawi 2017) . This work emphasized the sustainability of the resultant hydraulic cement by employing a combination of calcin ation of volcanic tuff at moderate temperature followed by mechanochemical processing of the blend of volcanic tuff with other raw materials to produce the hydraulic cement. Volcanic tuffs offer a wide range of reactivity depending upon their degree of cry stallinity and mineralogy (Nesbitt and Young 1984) . Reactive volcanic tuffs have been used for production of historic concrete. Early stone buildings have made use of more reactive volcanic tuffs together with lime to produce relatively strong and durable mortars, some of which have survived few centuries of exposure to weathering and seismic effects (Shi and Day 1993, Goldsworthy and ZHU 133 2009, Allen 2015) . Aluminosilicate precursors such as reactive volcanic tuff (or ash) can undergo dissolution and precipitation processes in lime solution (Jha and Singh 2011, Mason 2012, Al - Zboon, Al - smadi et al. 2016, Djobo, Elimbi et al. 2016, Tekin 2016) , which yield calcium aluminosilicate hydrate (C - A - S - H) structures with de sired binding attributes (Walkley, San Nicolas et al. , Nath and Sarker 2015) . Considering the variability in the reactivity of different volcanic tuffs, this investigation resorted to thermal activation of the tuff at mode rate temperatures in order to achieve viable levels of reactivity prior to processing of the tuff and other raw materials into a hydraulic cement. 7.2 Experimental Program 7.2.1 Materials Natural pumice was obtained from HESS Pumice ® mining, Idaho (United States). Some properties of this pumice, reported by the manufacturer, are presented in Table 14 . The other raw materials used for production of the pumice - based hydraul ic cement included lime, Sodium sulfate and Soda Ash (Na 2 CO 3 ) as chemical reagents , and gypsum as additive. Soda ash as well as sodium sulfate have been shown in past investigations to accelerate the hydration process of lime - aluminosilicate binders (Allahverdi and Ghorbani 2006) . While conventional alkali activated binder s are obtained via alkali activation of aluminosilicate precursors without a focus on the addition of lime, the lime con stituent of this hydraulic cement produces a hybrid structure of (Ca, Na) aluminosilicate hydrates and probably calcium silicate hydrate which is amenable to room - temperature curing. This hybrid chemistry, when used in the context of a one - part hydraulic c ement, also seems to yield hydration products with improved moisture resistance. 134 7 .2.2 Formulations of Raw Materials and Their Processing into Hydraulic cements The formulations of raw materials considered in this investigation for synthesis of hydraulic cements are introduced in These formulations were partly based on those developed in the literature on two - part alkali activated binders which employ volcanic tuff in powder form : lime weight ratios in the 0.6 - 0.75: 0.3 - 0.23 range (Cultrone, Sebastian et al. 2005, Chatterji, Brenneis et al. 2016) . Each formulation was blended and heat - treated at 700 o C for four hours (wit h a heating rate of 10°C/min) in order to improve its reactivity. This temperature was selected after trial studies involving heat treatment at different temperatures. After heat - treatment, the product was allowed to cool down to room temperature over seve ral hours (with the furnace turned off). After cooling, the heat - treated blends were ball - milled for the purpose of size reduction and mechanochemical processing. The ball - milling parameters are presented in Table 15 . A ceramic jar (5.6 L) ball mill was used in this investigation operated at an optimum rotational speed as a function of the internal diameter of the jar and diameter of the steel balls (Watanabe 1999) . This proces s yielded the hydraulic cements formulated with pumice for construction applications. Transformation of raw materials into hydraulic cement, and the change in crystalline structure caused by ball - milling support the mechanochemical effects rendered by this milling process. Hardness (Mohs) pH R radioactivity Crystalline Si0 2 Softening Point GE Brightness Specific Gravity 6 7.2 0 None Detected 900 C 84 2.35 135 Steel Ball Diameter (mm) Steel Ball - to - Material Weight Ratio Milling duration (hr) Large Medium Small 10 3 76.2 25.4 12.7 7.2. 3 Characterization Methods 136 Mix Precursor (pumice) Wt% Chemical Reagent(s) Water/binder ratio Sand 1 60 40 (Sodium Sulfate) 0.6 3 2 65 0.35 (Soda Ash) 0.6 3 3 60 0.2 (lime)+ 0.20 (Soda Ash) 0.6 3 4 75 0.25 (lime) 0.6 3 5 75 0.25(Sodium Sulfate) 0.6 3 6 60 0.2 (Sodium Sulfate) + 0.2 (Gypsum) 0.6 3 7 75 0.20 (lime) + 0.05 (Gypsum) 0.6 3 8 75 0.20 (lime) + 0.05 (soda ash) 0.71 3 9 65 0.35(lime) 0.71 3 10 20 0.2(lime)+0.6 (gypsum) 0.74 3 11 85 0.15 (Sodium Sulfate) 0.6 3 12 50 0.5 (lime) 0.6 3 13 60 0.3(Sodium sulfate) + 0.1 (lime) 0.6 3 The chemical composition of raw pumice was determined using X - ray fluorescence (XRF) spectroscopy. Phase compositions of the samples were examined by X - ray diffraction (XRD) spectroscopy. FTIR spectroscopy was conducted in the 4000 400 cm 1 range to investigate the chemical environment (bond structure) of the as - received pumice and the synthesized alkali activated cement based on pumice. The raw (untreated) pumice and the end products of alkali activation were subjected to SEM observation for evaluating their microstructural features. SEM observations were carried out on a JCM - - 15 kV using a secondary electron ( SE) detector. SEM observations were made on the pumice external surface and on the fractured 137 surfaces of hydrated paste at 28 days of age. Samples were sputtered with gold prior to SEM observations. Thermogravimetric analysis (TGA) was performed by heatin g the samples at a rate of 10 C min - 1 in a dry air flow between 50 C and 950 C. The exothermic heat of hydration of the hydraulic cement was measured using a calorimeter (TAM Air Isothermal Calorimeter). In this test, about 25g of freshly mixed paste was weighed into a flask, which was then capped and placed in the calorimeter. Heat generation caused by exothermic hydration reactions was monitored over 18 hours. 7. 3 Test Results and Discussion 7.3.1 Particle Size Distribution The visual appearance and particle size distribution (produced via laser granulometry) of the pumice used in this investigation are presented in Figure 84 . The median pa rticle size of the pumice was 9.8 m, and its specific surface area was 300 m 2 /kg . 138 7.3.2 Chemical Composition Table 17 . presents the chemical composition, obtained via XRF spectroscopy, and loss on ignition of the pumice used in this investigation. The results indicate that the pumice used here is rich in SiO 2 and K 2 O; its Al 2 O 3 content is near the lower range expected for pumice. As an aluminosilicate material , pumice (alone or in combination with other minerals) can be transformed into inorganic (cementitious) binders via dissolution and precipitation steps u sing different alkali hardeners or reactive ingredients . Table 17 . Chemical composition of the pumice used in the experimental work . Chemical compound Fe 2 O 3 SiO 2 Al 2 O 3 CaO K 2 O MgO LOI % 1.1 76.2 13.5 0.8 1.8 0.05 5 7.3.3 Compressive Strength of Mortar The 7 - day compressive strength test results summarized in Figure 85 a . indicate that, with heat treatment of raw materials at a relat ively low temperature of 700 o C, satisfactory compressive strengths (up to 22 MPa) can be achieved at 28 days of age. Mix 9 (Pumice activated with lime) was observed at age 7 and 28 days in dry and wet conditions) as shown in Figure 85 b . . Results indicated that Mix9 achieved average 7 - days compressive strength is 5 MPa and its compressive strength increases with time to reach around 22 MPa after 28 days with moisture stability with average wet compressive strength about 20 MPa. 139 ( a) 28 - day compressive strength test results ( b) Effects of age and moisture condition on Mix 9 7.3.4 Mineralogy The mineralogical compositions of the pumice and the feed sample before and af ter mechanochemical processing, obtained via x - rat diffractometry, are presented in Figure 86 . The XRD pattern of as - received pumice exhibits a major amorphous hump, centered at 2 = 25 . X - ray d iffraction patterns of the feed sample (un - milled) and the milled sample have general simi larities but some differences . T he milled alkali activated cement exhibits both amorphous and crystalline phases , which is characteristic of the glassy phase in volcanic materials (Djobo, Elimbi et al. 2016, Djobo, Elimbi et al. 2016) . This pattern points at the presence of an amorphous phase, which gives a broad band at 2 - 28 , together with minerals , Manitobaite and Melanterite ident ified by sharp diffraction peaks . The appearance of Quartz after milling could be attributed to the breakdown of covalent bonds of the silicate network of the volcanic tuff ( Si O ¯ , Ca O ¯ and Al O¯). The presence of moisture in atmosphere enables transforma tion of Si O ¯ to silanol groups (Si OH) which can form Quarts through polycondensation / crystallization (Kalinkina, Kalinkin et al. 2001, Djobo, Elimbi et al. 2016) . 140 In addition, a sharpening of the XRD peaks of AAC after milling is note d around 35° . Prior to milling, one can observe the These nuclei grew into well - identified crystals (Melantrite) upon milling. In other words, thermal treatment of the blend of raw materials (prior to milling) led to nucleation of Melantrite, and mechanochemical treatment (milling) led to growth of this crystalline structure (Wang, Xue et al. 2000, Hua and Li 2007, Charoonsuk and Vittayakorn 2017, Senna 2017) . 7.3.5 Chemical Environment Figure 87 . presents the FTIR spectra of the raw pumice and the hydration products of the cement formulated (and processed) with this pumice. For raw pumice, the characteristic peak observed at 1032 cm 1 may be attributed to the asymmetric vibration of Si - O - Si that generally occurs in the 1000 1044 cm 1 region (Gök, Göde et al. 2006, Li, Yang et al. 2009) . 141 The prevalence of asymmetric vibration of Si - O - Si over its stretching vibration points at the relatively low de gree of polymerization of silica tetrahedra in this pumice (Chindaprasirt, Jaturapitakku l et al. 2009) . The presence of silica as a chemical constituent of pumice is in line with the detection of the asymmetric vibration of Si - O - Si detected in the FTIR spectrum of pumice. The relatively weak peaks of raw pumice between 1200 - 1400 cm - 1 can b e attributed to the asymmetric stretching vibrations of Al O/Si O bonds (Kani and Allahverdi 2009, Li, Yang et al. 2009) . The peaks at 1600, 2366 and 2978 cm - 1 in the pumice spectrum correspond to stretching vibration of O - H and bending vibration of H O H groups in the water molecules contained in pumice (Chabiron, Pironon et al. 2004) . The broadened peak in the 641 - 1400 cm 1 region of the FTIR spectrum of the hydrated paste may be due to the merging of IR peaks corresponding to the other metal oxides present in pumice (AC130) . The Si O Si/Si O Al bending band can be observed at 641 cm - 1 in the FTIR spectrum cement hydrates (Li, Yang et al. 2009) . These bands are common in aluminosilicate precursors and provide an indication o f the degree of amorphization of the material, since its intensity is lower at a higher degree of crystallinity (Fomina, Strokova et al. 2013) . In the spectrum generated for cement hydrates, the peak at 2366 cm - 1 could correspond to the formation of carbonates in both of raw pumice and the hydrated paste. 142 7.3.6 Microstructural Characteristics Scanning electron microscope images depicting the micro morpholog ical features of the original pumice, the non - hydrated cement, and the resultant hydration products (at 28 days of age) are presented in Figure 88 . Pumice ( Figure 88 a . ) seems to comprise larger particles that are covered with finer particles ranging in size from few micrometers down to sub - micrometer dimensions. Measurements made on the particle size distribution of pumice (presented later) confirmed this observation. An SEM image of the hydration products of the hydraulic cement is presented in Figure 88 c . (taken from a fractured surface of the hydrated binder). Based on the observations made on the raw pumice ( Figure 88 b . ), some non - hydrated cement particles could be identified among hydration products (marked by an arrow in Figure 88 c . ). This observation that some non - reactive phases were inherited from the parent material by the hydration products has also been made 143 by other investigators (He, Zhang et al. 2012, He, Jie et al. 2013) . An SEM ima ge (at lower magnification) taken of the exterior surface of hydration products is presented in Figure 88 d . ). The microstructure is observed to be porous, exhibiting so me shrinkage microcracks. While these microcracks may be caused by the excess drying of specimens for the purpose of scanning electron microscopy, one should be aware of the fact that some alkali activated binders exhibit larger shrinkage than binders base d on ordinary Portland cement (Van Jaarsveld, Van Deventer et al. 1997, Wallah 2009) . The porosity and pore size of the alkali activated binder observed here seem to be l arger than those found in ordinary Portland cement paste. This finding point at the need to reduce the water/binder ratio, which could be accomplished using water - reducers. Special processing techniques employing vacuum or applying pressure to remove exces s water and air have been used to produce a less porous polymeric microstructure 2013) . 144 Figure 88 . SEM observation for microstructure of raw pumice (a,b), and hydration products of alkali acti vated cement based on pumice (c,d) . 7.3.7 Thermogravimetric Analysis The thermogravimetric and differential thermal analysis data produced for raw pumice are presented in Figure 89 . The measured value of weight loss for pumice at 900 o C is 7 wt.%. Most of the weight loss occurs below 550 o C, which presumably results mostly from the water content of pumice. As a hydrophilic material, p umice absorbs water (AC130) . The main weigh t loss before 550 C from raw pu mice was a result of water loss due to both evaporations of free water and condensation/polymerization of T OH groups (T = Si, Al). The pr esence of water can 145 be confi rmed using the FTIR spectrum of Figure 8 6 . that exhibits O H vibration bands at 2366 and 2978 cm 1 . Moreover, the DTA curve for raw pumice in Figure 90 . exhibits endothermic peaks due to removal of adsorbed moisture and OH spe cies attributed to metal oxides as well as volatile organic impurities existing at small concentrations (Mourhly, Khachani et al. 2015) . The thermogravimetry and differential analysis data produced for the alkali activated binder are presented in Figure 90 . A minor weight loss of 0.5% is observed in the 400 - 430 o C temperature range which is typically indicative of the reactivity of volcanic tuff (Tchakouté, Kong et al. 2015) . The second major weight loss occurs in the 450 - 680 °C temperature range , that can be assigned to the loss of the chemically bond water present in the alkali activated cement structure (Djobo, Tchakouté et al. 2016) . A DTA thermogram of paste resulting from hydration of the cement formulated with pumice exhibits an endothermic reaction in the range of 400 - 450°C, this peak is correlated to the loss of physically adsorbed water from the surface and 146 matching with weight loss in TGA curve. The gai n in weight beyond 750 o C may point possible oxidation phenomena that might include allotropic phase transformation of iron oxides (Wen, Li et al. 2004, Leonelli, Kamseu et al. 2007) , which could occur due to leakage of oxygen into the test chamber. Re - adsorption of some CO 2 released from the specimen at elevated temperatur e could be another factor causing the observed weight gain. 7.3.8 Isothermal conduction calorimetry measurement The calorimetry measurement was used herein to evaluate the heat released during alkali ne activation of volcanic pumice with three different activators (sodium sulphate, lime and sodium carbonate) at 27°C. The results, depicted in Figure 91 . , show initial exothermic peaks occurring in less than 2 hours. These initial peaks correspond to the dissolution - precipitation of the reactive phases at 27°C (Djobo, Elimbi et al. 2016, Djobo, Elimbi et al. 2016) , including 147 aluminate and silicate species (Yip, Lukey et al. 2004, Buchwald, Hilbig et al. 2007, Li and Liu 2007, Kumar, Kumar et al. 2010) . The rapid deceleration after the first peak indicates that the wetting process and the ini tial dissolution and reaction phenomena slow down. This is followed by the appearance of a second peak for the paste activated with sodium sulphate (after about 40 minutes) and with lime ( after about 5 hours ). When lime is used as the chemical reagent, a weak s houlder appears at about 2 hours, that could be due to hydration of metal oxides in pumice only, or reactions attributed to the instant sorption of lime and formation of nucleation sites on pumice particles (Langan, Weng et al. 2002, Kumar, Kumar et al. 2010) .There is a very late (at about 10 hours) trend towards rising of the rate of heat release, but no peak prior to that, when sodium carbonate is used as the chemical reagent. The later stages of dissolution occur simultaneously with polymerization reactions , both of which contribute to heat generation. As seen in these curves in Figure 92 . , an exothermic peak appears immediately when water is mixed with raw pumice which can be attributed to the instant sorption of activation 148 solution on the surface of raw material particles and the ensuing dissolution of the solid aluminosilicate and aluminate precursors (Kani, Allahverdi et al. 2 017) . An additional exothermic peak (after 2 hours) for the blend of raw materials (before heating or milling), which may be linked to the formation of a transient hydrate product. Appearance of second peak after 5 hours for alkali activated cement subj ected to milling (mechanochemical synthesis) can be attributed to partial replacement of SiO 4 tetrahedra of the silicate network of the volcanic tuff with AlO 4 tetrahedra, which decreases the length of silicate chain and leads to the formation of Al - substi tuted phase (Djobo, Elimbi et al. 2016, Djobo, Elimbi et al. 2016) ; this is consistent with the XRD pattern for AAC after milling. After a period of time (7 hou rs) for all mixtures, the process reached an apparent thermally steady state, during which the freshly formed small gel units are probably continuously transform into larger - scale networks by local reorganization (White, Provis et al. 2013) 0.0 20.0 40.0 60.0 80.0 100.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 Rate of heat of hydration (mW/g) Time of hydration (hours) Thermal activated Mechanochemically activated Raw blends 149 7. 4 Conclusion These geopolymer precursors polymerize upon the addition of water, forming geopolymer precursors polymerize upon the addition of water, forming geopolymers with A volcanic tuff (pumice) was used together with naturally occurring sources of alkali and alkalin e earth metals for production of a hydraulic cement. The volcanic tuff was activated at moderately elevated temperatures, and was transformed, together with other raw materials, into a hydraulic cement via a simple milling action. Different raw materials f ormulations with various sources of alkali and alkaline earth metals were evaluated. The resultant hydraulic cements were characterized through assessment of their physical, chemical and mineralogical characteristics, and strength development attributes up on hydration. The following conclusions were derived based on this experimental investigation. 1. 2. 3. 4. 150 5. The work reported herein was funded by the U.S. Army Grant No. W9132T - 16 - C - 0003 . Authors are thankful to D r. Ghassan Alchaar, the Project Manager, for his guidance and encouragement. 151 REFERENCES 152 REFERENCES AC130, I., Acceptance Criteria for Prefabricated Wood Shear Panels. ICC Evaluation Service, Inc., Whittier, CA, 2004. Allahverdi, A. and J. Ghorbani, Chemical activation and set acceleration of lime - natural pozzolan cement. Ceramics Silikaty, 2006. 50 (4): p. 193. Allen, G., Hydraulic lime mortar for stone, brick and block Masonry: a best practice guide. 2015: Routledge. 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Construction and Building Materials 220 (2019): 516 - 524. 8.1 Introduction Large - volume use of industrial wastes for production of construction materials can divert large quantities of industrial byproducts from landfills for valu e - added use towards improving the sustainability and economics of infrastructure systems [1 - 3]. This practice can also mitigate the release of toxic leachates to the environment by stabilizing the hazardous constituents of some in dustrial byproducts. The slate of fuels burned by power plants to generate electricity has been expanded beyond coal, to include biomass and municipal solid waste (among others). Combustion of these fuels generates solid residues (ash). Examples of these s olid residues are coal fly ash, bottom ash resulting from combustion of municipal solid wastes, and biomass (e.g., rice husk) ash [4 - 6]. These ashes largely comprise the mineral constituents of each fuel. The combustion process al so concentrates any heavy metal constituents of the fuel in ash, which should be addressed in development of applications for the ash. The work reported herein develops an alternative binder chemistry using a blend of coal, biomass and municipal solid wast e combustion ashes. The binder chemistry used here yields hydration products with desirable capabilities for stabilization of heavy metals. Brief 159 introductions to coal fly ash, rice husk ash, and municipal solid waste combustion ash are presented below fol lowed by a concise introduction to the hydraulic binder chemistry considered here. A sustainable mechanochemical approach was adopted for production of hydraulic binder, which is also briefly introduced in the following. Coal fly ash is the ash separated f rom the flue gas of power plants burning pulverized coal [7, 8]. It comprises fine spherical particles that precipitate from the stack gases. Coal fly ash is largely amorphous with desired reactivity; its chemical composition comprises largely of silicon, aluminum and calcium. Rice husks (RHs) is a byproduct of paddy rice processing. It is a renewable fuel for generation of energy and weighs approximately 20% of the harvested paddy. Rice husk ash (RHA) is the solid residue resulting from combustion of rice husk for power generation [9, 10]. Its chemistry is dominated by silica (90 - 95 wt.%), which is largely amorphous [11] with residual carbon as the main i mpurity and other traces metal cations such as K and Ca. Rice husk ash assumes a porous microstructure which raises its reactivity by producing large specific surface areas. Silica can be crystalline or amorphous depending on the temperature of calcination and exposure time [12, 13]. Amorphous rice husk ash is a high - performance pozzolan was used as a supplementary binderitious material (SCM) that can partially replace ordinary Portland binder in the concr ete mix proportions [9, 14]. Geopolymers have also been prepared with RHA as a source of amorphous silica; investigations in this area have addressed the effects of such factors as alkalinity, curing time and particle size distrib ution [15 - 17]. Energy - from - Waste (EFW) facilities recover energy from municipal solid waste in specially designed boilers to ensure complete combustion for efficient recovery of energy [18, 19] . The 160 EFW process produces an ash byproduct that comprises the bottom ash that remains after the combustion process and the residue that remains from emission control systems. A main aim for using beneficiary of incineration residues is in production of construction materials. Bottom ashes have been investigated as road subbase material, and as an alternative to sand and gravel [20]. Replacing primary resources by secondary raw materials compacts material cycles and lower natural resource de pletion, therefore contributing to the recognition of a circular economy. Moreover, the embodied energy relevant to first manufacturing of recycled materials is usually less than that of primary materials. In addition to the consumption of sourced material s, the consequences of resource mining must be taken into consideration [21]. Utilizing of residual ashes and municipal solid waste (MSW) ash in building materials can be viewed as a practicable alternative to landfilling, conside ring the past success in recycling of different waste sources (e.g. , blast - furnace slag ,coal fly ash, bauxite fines, phospho - gypsum) [22,70 - 71]. Geopolymerization process is based on the natural stoichiometry reaction that arise s between amorphous silica - and alumina - rich solids in high alkaline activator solutions at nearly elevated temperatures. This reaction yields a geopolymer material with high - order in terms of stability , its microstructure consist of an amorphous polymeri c network with interconnected Si O Al O Si bonds [23 - 28, 68 - 70] . The advantage of RHA as a source of reactive silica for geopolymerizaiton relate to its highly amorphous nature and also its high specific surface area. Adequate sources of alumina should be used together with RHA in order to achieve viable Si/Al ratios [30 - 32]. Mechanochemistry concerns chemical and physio - chemical changes of materials at all states of aggregation via input of mechanical energy. The intensity of mechanical energy required 161 to render Mechanochemical effects can be realized in various mills, incl uding the ball mills that are currently used in binder production facilities [44]. Mechanochemistry is often viewed as a temperatures, and attempts to induce favorab le physio - chemical phenomena using non - hydrostatic mechanical stresses that are generally applied at high rates [33 - 37]. At the atomic scale, the mechanical deformation of crystalline structural arrangements under stress can be co nsidered as a distortion or modification of the coordination shells of individual atoms. In turn, atomistic processes can be generically described as local structural excitations [33 - 37]. These excitations pull the system away fro m thermodynamic equilibrium, which usually promotes a significant enhanbinder of chemical reactivity [38, 39]. A technical feasibility of incorporation industrial waste materials employed in the current work as a supplementary bin der itious material in concrete mix design has been reported in [61 - 63]. A ternary blend of Portland binder , industrial residual ashes and limestone powder were formulated to improve the properties of self - compacted concrete [64], and the use of a mixture o f these ashes in addition to limestone and wood fibers led to improve the properties of lightweight concrete blocks [64 - 67 ] The main sight of this investigation was on development of a new sustainable class of hydraulic binder that relies upon the robust n ature of alkali aluminosilicate binder chemistry to make value - added and large - volume use of rice husk ash, MSW ash and coal fly ash as primary raw materials. In an effort to produce a hydraulic binder that requires only the addition of water (in lieu of a lkaline solutions in traditional geopolymerization), the blend of raw materials was forced to undergo Mechanochemical processing. 162 8.2 Material and Methods 8.2.1 Materials Class C coal fly ash was supplied as dry powder by the Lansing Board of Water & Light (LBWL) in Lansing, Michigan. RHA with more than 90% amorphous SiO 2 content was obtained by controlled calcination of rice husk at 600°C for two hours, followed by ball milling for 30 minutes, available potassium hydroxide flakes (caustic potash), sodium carbonate were used as alkaline materials. (ASTM C778) graded standard silica sand was selected as fine aggregate to prepare mortar mixes. 8.2.2 Particle Size Distribution The particle - size di stribution (PSD) (generated through laser granulometry) of the milled municipal solid water (MSW) incineration ash used in this work is presented in Figure 93 . . The 2 /cm 3 ) 163 8.2.3 Chemical Composition Table 18 . introduced the chemical compositions of the ashes considered in this investigation, that were obtained via XRF spectroscopy. The MSW ash is observed to be rich in calcium and incorporate chloride and sulfur. Its loss - on - ignition is also relatively high. The mere presence of chloride and sulfur in MSW ash does not means that they would be necessarily available for deleterious reactions. They will not adversely influe nce the qualities offered by the resultant hydraulic binder if they get chemically bound in insoluble compounds. One should also evaluate the reason for the high LOI of MSW ash, considering that carbonates with no deleterious effects could also raise the L OI value. The high LOI values of MSW fly ash [41] and MSWI bottom ash [42] have been reported in the literature. The alkali content of MSW ash was more than those of other ashes considered in this investi gation. The coal fly ash had relatively high silicon and aluminum oxide constitute that mainly comprised about 65% of the total mass, and the weight ratio of silicon to aluminum oxide was about 2. The relatively high (14.5%) CaO content of this coal fly as h qualifies it as Class C ( high calcium ) per ASTM C618. Rice husk ash comprises largely of silica; its LOI value was moderate at 5.1%. The amorphous nature of rice husk ash makes it a valuable source of silica for synthesis of alkali aluminosilicate hydrau lic binders. Table 18 . Chemical composition of coal fly ash, wt.%. Material SiO 2 CaO Al 2 O 3 K 2 O Na 2 O TiO 2 Cl SO 3 LOI Rice husk 90.0 0.60 0.01 2.30 -- --- -- -- 5.10 Coal fly ash 43.05 14.30 23.33 1.72 0.90 0.03 -- -- 1.82 MSW Ash 3.48 48.16 1.00 4.8 0.90 0.72 21.81 8.44 16.1% 164 8.3 Methods 8.3.1 Processing of Raw Materials The blend of coal ash, MSW ash and RHA was proportioned to produce a viable SiO 2 /Al 2 O 3 m olar ratio of 2 to 4 which yields desired engineering properties. These formulations as well as those of alkaline materials considered in this investigation are summarized in Table 19 . The blend of raw materials was undergoing mechanochemical processing to produce hydraulic binder as explained in previous investigations [40]. The effects of the relative proportions of rice husk ash and the municipal solid waste ash on the compressive strength development attributes of the resulting hydraulic binder were also investigated. The raw materials formulations considered in this series of tests are introduced in Table 20 . Mix RHA Coal Fly Ash MSW Ash Alkaline Material Water/Binder Ratio 1 0.3 0.2 0.1 Potassium hydroxide (0.4) 0.5 2 0.3 0.2 0.1 Sodium carbonate (0.4) 0.5 Mix RHA Coal Fly Ash MSW Ash Alkaline Material Water/Binder Ratio Sand 1 0 0.2 0.4 Potassium hydroxide (0.4) 0.5 2.75 2 0.1 0.2 0.3 Potassium hydroxide (0.4) 0.5 2.75 3 0.2 0.2 0.2 Potassium hydroxide (0.4) 0.5 2.75 4 0.3 0.2 0.1 Potassium hydroxide (0.4) 0.5 2.75 5 0.4 0.2 0 Potassium hydroxide (0.4) 0.5 2.75 165 8.3. 2 Characterization Methods The mortar mixtures had a silica sand - to - binder ratio of 2.5, and water - to - binder ratio of 0.5 to reach a desired fresh mix workability. They were prepared in a planetary mixer, cast into 50 cube molds, and consolidated under external vibration. The samples were kept in sealed condition a t 90 - 97% relative humidity and at room temperature. They were demolded after 24 hours and continued sealing at 90 - 97% relative humidity and room temperature (23 C ° ) for compression testing at 7 days age. Compression tests were performed in universal test m achine with speed of 0.1 mm/min. Ten reproduced samples were casted and tested for each mix design, and the average values of compressive strength were determined. The chemical and elemental analysis of raw materials was inspected using X - ray fluorescence (XRF) spectroscopy. Their phase identifications were examined using X - ray diffraction (XRD) spectroscopy. FTIR spectroscopy was also performed on the raw materials and the hydraulic binder in the 4000 400 cm 1 range to observe their chemical p roperties (bond nature). The raw materials and the ruptured surfaces of hydrated binder pastes (at 28 days of age) were also evaluated via scanning electron microscopy to gain better understanding into their microstructural traits. SEM observations were ma de on a JCM - accelerating voltage of 10 - 15 kV using a secondary electron (SE) detector. Samples were sputtered with gold prior to SEM observations. The Toxicity Characteristic Leaching Procedure (TCLP) is a test method used to determine whether a waste is hazardous due to its characteristics. TCLP tests were carried out to determine the potential for geopolymerization to reduce the leachability of specific elements in the IFA. The 166 20 heavy metals (Be, Al, V, Cr, Mn, Co, Ni, Cu, Zn, As, S e, Mo, Ag, Cd, Sb, Ba, Hg, Tl, Pb, and Th) were tested before and after mechanochemical processing. 8.4 Test Results and Discussion 8.4.1 Chemical Bond Environment Figure 93 a . presents the FTIR spectra of the raw materials for the coal fly ash, rice husk a sh and MSW incineration ash. The FTIR data for the hydrated mechanochemically processed binder is presented in Figure 93 b. The distinct peak centered around 500 - 560 cm 1 (band A) can be assigned to the O Si O vibrational bending mode of the SiO 4 tetrahedra . This band provides of crystallization [43]. Peaks at infrared spectrum ranges of 1200 900 cm - 1 (bands c, d) can be ascribed to th e asymmetric stretching vibration mode of Si O/Al O peak at of 850 777 cm - 1 (band f), that may be associated with asymmetric stretching vibration of Si O Si. The Si O Si stretching vibration mode is more influential than the O Si O bending mode. Therefore, one may use the Si O Si stretching vibration as an indication of the degree of geopolymerization [44 - 47] . The major differences between the as - received materials and the mechanochemically processed hydraulic binder relate to the shifts in the band around 1100 - 1200 cm - 1 to around 1050 cm - 1 (band g), and around 900 cm - 1 (band c) to 870cm - 1 (band f), both of which decreased slightly in intensity. 167 Moreover, the Si O Si peak shifted to a frequency that is lower than that in ori ginal residual ashes, indicating that a chemical change has been created in the binder phase. These shifts suggest that new binder/phases were created as a result of the mechanochemically induced reactions between ashes and alkaline materials (band c) [48]. This drop in intensity denoted that the amorphous phase in the residual ashes already have depolymerized to Si O and Al O bonds, and the shifts point at the polycondensation of these chemical bonds in the presence of alkaline me dium [49]. Figure 94 . FTIR spectra of: (a) raw ash materials; and (b) the mechanochemically processed hydrated binder . 8.4.2 SEM Observations 168 8.4.3 Mineralogy The XRD patterns of these ashes shown in Figure 95 . suggest that: (i) the municipal solid waste incineration ash is semi - crystalline, exhibiting XRD peaks corresponding to quartz and calcite, and it has a relatively low content of glassy phase when compared with other ashes; (ii) coal fly ash is also semi - crystalline with XRD peaks corresponding to mullite and quartz; and (iii) rice husk ash appears to be largely amorphous with a broad hump within around the region of 20 - 30° 2Theta that could point at the presence of an amorphized cristobalite [50]. The shift of FTIR spectra was observed in mechanochemically hydrated binder and it refereed to the formation of the new phase s of binder ( both Muscovite and Calcite , main elemental composition Ca and . This confirmed by X - ray powder di ffraction analysis of the hydrated. 169 Figure 96 . XRD patterns of the three ashes used in this investigation (C=calcite, Q=quartz, Mu=mullite, and patterns of the mechanochemically processed hydrated binder ; (Q: Quartz, M:Muscovite , P : Portlandite, C : Calcite . 8.4.4 Compressive Strength 8.4.4.1 Effect of Alkali Source The compressive strength test results obtained after 7 days of curing at room temperature in sealed condition are presented in Figure 97 . for geopolymer binders pre pared with two different alkali sources (potassium hydroxide and sodium carbonate). Potassium hydroxide is observed to produce to produce a significantly higher 7 - d ay compressive strength when compared with sodium carbonate. It should be noted that ASTM C1157 requires a 7 - day compressive strength of conditions considered in this experimental program yields a 7 - day compressive strength exceeding 50 MPa, that is more than twice the standard requirement, when potassium hydroxide is used as the source of alkali. Sodium carbonate would be a successful activator as far as the 170 formulatio n can readily release calcium cations to the solution in order to produce sodium hydroxide through reactions with sodium carbonate. In spite of the relatively high calcium content of the binder formulation considered here, its availability in solution coul d be why sodium carbonate could not act as a viable source of alkalis. The compressive strength obtained via geopolymerization reactions is influenced strongly by both the alumina - silicate precursors and the alkaline compound used in the formulation. The m olecular structure and the concentration of alkalis are key factors influencing the geopolymerization process [51, 52] . The OH ions supplied by alkalis (e.g., potassium hydroxide) attack the sialate - siloxo bonds to liberate alumi nate and silicate to the solution that react to form rearranged gels, which finally condensate by releasing water to produce a hardened solid [53, 54]. Strong alkalis tend to act more swiftly when the soluble silica is available, and play a crucial role in dissolving the silica and alumina constituents of the aluminosilicate precursors that enables their participation in the polycondensation stage of the geopolymerization process [53] . Scanning electron m icroscope images of the hydration products ( Figure 98 . ) indicated that the non - reacted raw materials (e.g., spherical fly ash particles) are more notable in the case of binder prepared with sodium carbonate than that formulated with potassium hydroxide. This observation suggests that sodium carbonate could not, in the formulation considered here, could not produce the level of alkalinity required for effective dissolutio n of the aluminosilicate precursors. 171 Figure 97 . Seven - day compressive strengths obtained with different sources of alkalis. (a) Sodium carbonate (b) Potassium hydroxide 8. 4.5 Effects of the Relative Quantities of Rice Husk Ash and Municipal Solid Waste Ash o n the Resulting Hydraulic Geopolymer Binder Performance Rice husk ash is a source of reactive silica; the municipal solid waste ash, on the other hand, is rich in calcium oxide and incorporates some potassium oxide. They can feasibly make synergistic contr ibutions to the chemistry of the hydraulic binder. An experimental investigation was undertaken in order to evaluate the effects of their proportions in the hydraulic binder formulation on the end product performance. 172 Figure 99 . shows the compressive strength test data generated for the hydraulic binder prepared with different RHA and MSW ash contents. The compressive strength of all binder formulations is observed to in crease with increasing RHA content (that is accompanied with decreasing MSW ash content). Rice husk ash (RHA) is a source of active silica; a rise in RHA content would thus raise the prevalence of Si - O - Si bonds which are stronger than either Si - O - Al and Al - O - Al bonds [23, 28]. The reactivity of silica in RHA could also benefit the extent of reactions after similar curing conditions. A rise in RHA content is thus expected to raise the degree of condensation and the prevalence of relatively strong Si - O - Si bonds in the condensed te trahedral aluminosilicate network, thus increasing the compressive strengths obtained with the hydraulic binder. Compressive strength, however, decreased when the rice husk ash content was raised beyond 30% (with 10% MSW content). This reversion of the tre nd in compressive strength with increasing RHA content could be attributed to: (i) hindrance of the reorganization of dissolved silica and alumina due to the excess concentration of soluble silica, which reduces the skeletal density of the geopolymer binde r (reportedly occurs at Si/Al molar ratios exceeding 2) [55], which weakens the resulting gel; and (ii) reduced dissolution of rice husk ash particles, with the remaining unreacted or partially reacted rice husk ash particles (det ected in the SEM images reviewed in the following) acting as porous fillers with adverse effects on strength [17]. For the raw materials types and formulations considered in this investigation, an RHA content of 30% (with an MSW a sh content of 10%) seems to yield a satisfactory chemical stability in solution, inducing polycondensation effects with favorable strength development characteristics. 173 No coal fly ash content in this test - . Unreacted or partially reacted binder particles can be det ected in all these images, which is a characteristic feature of some geopolymers [19]. A relatively dense structure with low amount of unreacted or partially reacted binder particles is noted for the binder formulation with 30% RHA and 10% MSW ash ( Figure 100 .) 174 8.4. 6 Toxicity tests TCLP tests were carried out to determine the potential of the mechanochemical processing and the subsequent hydration reactions to reduce leaching of heavy metals to the environment. Release of the RCRA heavy metals (Pb, Cd, Sr, Ba, Mo, Zn, Co) was evaluated for the blend of raw materials, the mechanochemically processed hydraulic binder, and the hydrated binder paste. The results for Formulation 4 (comprising 30% rice husk ash, 10% MSW ash, 20% coal fly ash and 40% KOH) are presented in Figure 101 . Mechanochemical processing produced significant reduction in the concentration of hazardous metal cations in leachates. This finding points at the immobilizati on capabilities of the physico - chemical phenomena that occur during 175 mechanochemical processing of raw materials. Further drops in release of heavy metals are noted after hydration of the binder. This can be attributed to the release of Al and Si species in the alkaline solution, followed by geopolymerization reactions that yield structures with high heavy metals immobilization qualities [56, 57]. The notable immobilization of Pb observed in Figure 101 . can be attributed to the formation of monomeric and/or oligomeric aluminate and silicate species, which then polycondense to form insoluble products that effectively encapsulate Pb. 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This interaction depends on the quality (bearing capacity, elastic modulus and compressive strength) of the aerated slurry, and the concentration of chicken mesh as well as the specific surface area and the spacing of chicken mesh wires. Slurry - infiltrated chicken mesh sheets exhibit a ductile behavior in tension. The transition from normal - density (non - aerated) slurry to aerated slurries of lower densities produces some drop in peak tensile load, but not in their ductile tensile load - deflection behavior. The aerated slurry - infiltrated chicken mesh frame exhibited a ductile failure mode with a stable hysteretic behavior that provided significant energy absorption capacity. This work also evaluated the energy efficiency of buildings constructed with aerated slurry - infiltrated mesh and biomass - based insulation. The desired seismic performance of the aerated slurry - infiltrat ed chicken mesh frame can be attributed to the high specific surface area of chicken mesh and its desired mechanical interlocking within the cementitious matrix . Treatment of wood chips/particles and shredded straw with aerated slurry effectively mitigates fungal growth in diverse moisture and fungal growth conditions . Together, these studies of slurry - infiltrated mesh and biomass - based insulation offer important lessons for the construction of lightweight, energy - efficient structures that utilize local 186 ma terials. Such buildings can be constructed locally with readily available materials, which reduces costs . Local laborers can also be trained to safely implement the mechanochemical process for creating the slurry , which makes this construction approach aff ordable and feasible for both residential and business purposes in a variety of locations.