A COMPARATIVE STUDY OF LIGHTWEIGHT CONCRETES Thai: for the Down 0! B. S. MICHIGAN STATE COLLEGE Arthur B. Hoppershad I948 A Comparative Study of‘ Lightweight Concretes A Thesis Submitted to The Faculty of MICHIGAN STATE COLLEGE of AGRICULTURE AND APPLIED SCIENCE by Arthur B. Egpperstead Candidate for the Degree of Bachelor of Science July 1948 "Hesrs c._/ 206058 ACKNOWLEDGMENT Appreciation is extended to the following for the material and information which they generously supplied: AleXitE Engineering Division of.Alexander Film Company, Colorado Springs, Colorado; Atlas Brick and Block Company, East Lansing, Michigan; The Briggs Company, Lansing, Michi- gan; The Celotex Corporation, Chigago, Illinois; The Gregg Lumber Company, Grand Rapids, Michigan; The Master Builders Company, Cleveland, Ohio; Office of the Housing Expediter, Washington, D. C.; Pumice Aggregate Sales Corporation, Albuquerque, New Mexico; Pumma-Stone Corporation, Detroit, Midligan; Standard Block and Supply, Lansing, Michigan; Stearns Manufacturing Company, Adrian, Michigan; Western Brick Company, Danville, Illinois; Zonolite Company, Dearborn, Micligan. INTRODUCTION Conventional concrete made with sand and gravel.has long been accepted as an excellent building material. Universal recognition has been accorded its qualities of permanence, adaptability, and strength. It weighs approximately 150 pounds per cubic foot, and when used structurally or with steel Iraming, the economical height to which a Structure can be built is restricted. hiuams, retaining walls, foundations, and bridge abutments, weight percubic foot is necessary and conventional concrete has no equal. Sand and gravel, both as to gradation and physical properties, vary materially from deposit to deposit, and even within a deposit. When making concrete with them, continual investigation of their gradation, soundness, moisture cantent, etc. must be conducted to assure concrete that is economical, and uniform in strength and workability. Any change in source of aggregate for a particular job involves complete redeter- mination of mix design. In addition, gravel deposits are shallow and limited, presenting a problem of conservation. The use of lightweight aggregates in concrete has several effects. In addition to reducing the weight per cubic foot by 20% to 75%, lightweight aggregates impart improve- ments to it. All of the lightweight aggregates contain amounts of dead air space within a cellular structure. All are chemically inert, and possess high fusing temperatures. These inherent properties also give lightweight concrete higher insulation, better accoustical value, and greater fire resistance than conventional concrete. Another important feature is that lightweight aggre- gates, being an artificially processed material, can be carefully controlled during manufacture, resulting in a dependable product with known and uniform properties. Specifications can be written for a particular application, and the results will be dependable. The various raw ma- terials from which lightweight aggregates are made are unlimited in quantity. The future of lightweight concretes is bright. It can be expected that more extensive use will be made of this building material as designers and builders come to recognize the numerous applications and the advantages to the building industry, as well as to the owner. TESTING (All of the different types of lightweight aggregate that were available, were used in making concrete for the Q various tests. A standard mix,by volume, of one part cement to four parts aggregate was used, and sufficient water added to obtain a four inch slump. The aggregates used were:- (1) vermiculite concrete aggregate (2) perlite concrete aggregate (3) slag (4) Cinders with sand (5) gravel with perlite fine aggregate (6) sand and gravel, fUrnishing a comparative standard. From each of these mixes, cylinders (6 x 12 inches) were made for compression tests, briquets for tension tests, and two inch cubes for testing moisture absorbtion and heat transfer. The moisture absorbtion test consisted of lab curing the samples for seven days, air-drying for 24 hours, oven-drying for 24 hours, and immersion in water for 24 hours. The differ- ence between the oven-dried weight and the moist weight after immersion was taken as the absorbed moisture, and the per- centage expressed in terms of oven-dried weight. The heat transfer test consisted of subjecting the cubes to a horizontal flame from a Mekker burner, and recording the heat rise on the opposite side at five minute intervals for thirty minutes. Neither of the two tests described above are standard, but were adOpted for comparative purposes only. The unit weight of each aggregate, and of concrete made from it, was found by filling a container of knownvolume in three increments, and rodding each increment 25 times. Results of the several tests were recorded in graphical form to illustrate more readily the comparative values. Comments on the qualities of each mix will be found under the individual aggregate discussion, as well as suggestions for future work. TEST RESULTS Gallons of'Water per Sack of Cement mammmpmma.mo pnmama vamp opohoqoo nmwph mo pnmfiog pans whan Gm>mm pm Apmamhpm m>ammohgsoo pawn nm>om pm npmumhpm mwwmame megaphomn< «savages madam AoGH 950m gov capmm unmamouhnpma "D Sla‘ Vermiculite an. and Gravel , Perlite and Gravel Sand and Cinders 10 15 Moisture Absorbtion in Percent of Oven-Dried Weight 0 mpwmwpmm<.mo pnmama pans opmhonoo ammph mo pnmfima pans whom nm>mm pm npmnmhpm m>flmmmnmaoo mama nm>om pd npmqmnpm owamnoa cowpnhomp< onspmfios m..— 1 s- e e V e r a v e— 1. H“ H“ r a d S l l G r n r u G 01 e c d C P .1 no m .d m 21.]: I II m d a a Ie d V m m d an .1 1 m r S e O P 4. O 6 O 8! 100 Tensile Strength in Pounds per Square Inch 0 mpmmwpmm¢.mo pamfima vamp upmhonoo gamma mo pnmwoa pans mama nmbmm pm spmnmnpm o>wmmonaaoo mama cm>mm pm npmnmnpm adamnme 1i 1. s an e e e r +u e V V e l .1 +u m m m s a n G G .1 e u C P C 0 d d auzI.m. mm .m MW .d e "v m at .d a 1 m S l r S e 0 P n2 1 O 8 .l O 4 2 300 Compressive Strength in Pounds pefi Square Inch 2500 2000 1500 1000 500 0. Sand and Gravel 4,____ie_lli_te and Gravfi Sand and Cinders“> P m , Perlite . Vermiculite g-fir Compressive Strength at Seven Days Unit Weight of Fresh Concrete Unit Weight of Aggregate 150 Weight in Pounds per Cubic Foot 100 50 Sand and Gravel Perlite and Gravel Sand and Cinders Slag‘ Expa nded Shale and ClaL, ggumic Perlite fl Vermigulitg Unit Weight of Fresh Concrete Unit Weight of Aggregate Weight in Bounds per Cubic Foot 100 ' 50 0 Sand and Gravel Perlite and Gravel Sand and Cinders Pumice Perlite .___J. Vermiculite _., Unit Weight of Aggregate L. A. a... / - T- Mm; , I O . / I I a - [/7 .10 <95 E 75nd TYPICAL SET-UP FOR HEAT TRANSFER TEST *—*»_'\r‘_\\\‘¥\\ \— ‘> T ' Left, Mekker burner Center, Concrete test cube Right, Thermometer TYPICAL BREAKS IN COMPRESSION CYLINDERS g I I t T I \ 7 \\\ ~\x\ \_\,4_ V vermiculite “ iSlag‘XOTT’T‘\ \ '\ _ \Cinders and Sand recording the heat rise on the opposite side at five minute intervals for thirty minutes. Neither of the two tests described above are standard, but were adepted for comparative purposes onli. The unit weight of each aggregate, and of concrete made from it, was found by filling a container of knOanolume in three increments, and rodding each increment 25 times. Results of the several tests were recorded in graphical form to illustrate more readily the comparative values. Comments on the qualities of each mix will be found under the individual aggregate discussion, as well as suggestions for future work. TEST RESULTS 10 Gallons of Water per Sack of Cement 5 0 Sang and Gravel I Perli.e and Gravel. Sand and Cinders I Slag Vermiculite Water-Cement Ratio for Four Inch Slump 100 80 ‘Moisture Absorbtion in Percent of Oven-Dried Weight 60 Sand and Gravel i I ! I Perlite and.Gravel Sand and Cinders -—-_1. Li Slag Perlite Vermiculite L0 20 O Moisture Absorbtion 300 Tensile Strength in Pounds per Square Inch 180 120 60 0 Sand and Gravel I Perlite and Gravel Sand and Cinders Slag Perlite Vergiculit e Tensile Strength at Seven Days 2000 Compressive Strength in Pounds pefi Square Inch 1500 1000 500 o and Gravel Perli he and Gravel Sand and Cindergd Perlit e Vermiculite4_ Compressive Strength at Seven Days 150 Weight in Pounds per Cubic Foot 100 50 Sand and Gravel Perlite and Gravel Sand and Cinders Slaa Expa mded Shale and Clay, gPumic Perlite fl Unit Weight of Fresh Concrete 150 Weight in .Bounds per Cubic Foot 100 '50 g§and and Gravel Perlite and Gravel Sand and Cinders Slag Pumice Perlite Vermiculite fl! Unit Weight of.Aggregate ( r I . .34.. .z. are a\ a . .‘...p-..I...o I TYPICAL SET-UP FOR HEAT TRANSFER TEST xi, \5\\\\\_\\\-\ ’ Left, Mekker burner Center, Concrete test cube Right, Thermometer TYPICAL BREAKS IN COMPRESSION CYLINDERS \\\\‘\\\-\'\_V «_ Vermiculite Cinders and Sand TYPICAL BREAKS IN COMPRESSION CYLINDERS Sand and Gravel i . L? C . Perlite and Gravel TIE LIGHT'J’EIGHT AGGREC‘mTES VERNICULITE Vermiculite is a micaceous mineral mined chiefly in Colorado, Montana, North Carolina, and South Carolina. It occurs in nature as a result of the action of heat and water on phlogopite mica and bbtite. Vermiculite aggregate is produced by exposing the raw ore to heat of plus 1800° F. The water between the laminations changes to steam and expands the flakes to about fifteen times their original size. Due to the bulkiness of expanded vermiculite in propor- tion to its weight, it is more feasible to ship the raw ore to strategically located plants, where the ore is processed and the commercial product distributed. The price of ex- panded vermiculite generally reflects its proximity to the producing plant. To compete with the other lightweight aggregates in a given location, the expanding plant must be contingent to that area. Concrete made with expanded vermiculite weighs as low as twenty pounds per cubic foot, and is used in place of concrete made with sand and gravel primarily for its ex- tremely light weight, its insulation qualities, its accousti- cal value, and where strength is not required. Because of the millions of entrapped air cells caused by the expansion process, vermiculite concrete has a high insulation value. This quality lends itself for use as in- sulating concrete in such installations as roof decks, radiant heating floors, interior walls of cold storage buildings, precast blocks and slabs, boiler insulation, and many other applications demanding low heat conductivity. These same air cells provide the accoustical value of vermiculite concrete. It is used in hospitals, churches, theatres, and other places where low values of sound trans- mission are desired. Vermiculite concrete has a low compressive strength, flexural strength, and modulus of elasticity, and cannot be used for load bearing members. The low strengths exibited can be partly attributed to the high w/c ratio required to obtain a workable mix, but is primarily due to the nature of the aggregate, which is epongy and easily crushed. Vermiculite used in the tests was obtained from the Universal Zonolite Insulation Company, and is manufactured under the trade name Zonolite. The work done with Zonolite brought out several facts. The unit weight of this aggregate varies according to the method of consolidation, i.e. vi- brated or tamped. It is suggested that a mix determined by weight be used rather than one by volume. The testing also indicated that the extremely light weight of this concrete causes a problem of consolidation which is not solved by rodding or interior vibration. It is suggested that exterior vibration might prove more feasible. Evidence of shrinkage was noticed in the test cylinders, probably due largely to the quantity of entrained air bubbles occuring in the mix. It was impossible to determine the amount of entrained air, because the aggregate contains an undetermined amount and floats on water. The mix was very workable when sufficient water was added, and its consistency can be described as slushy, not at all harsh or gritty. Further work with vermiculite concrete should include experiments to determine:- (1) bond strength (2) control of shrinkage (3) its utility as a structural member when used with other aggregates, observing:- (a) compressive strength (b5 flexural strength (c) accoustical and insulating properties (d) the most economical combination for a parti- cular application. PERLITE Perlite is a natural voncanic glass formed when the lava cools in the fissures radiating from the core of a volcano. It is a hard, black rock appearing to be very solid, but actually permeated with minute gas pockets. Perlite deposits are found in the Rocky Mountain region of the Western and Southwestern Stass. .The action of perlite when exposed to heat of plus 2000"F. depends on the source of the ore. Some types explode and other foam when heated. Expodure to this heat causes most types to expand and bleach to colors from pure white to light tan, each particle containing innumerable air bubbles with thin outer walls. Most of the present producing plants are located at or near the perlite deposits. The greatest use of perlite con- crete is found in the surrounding areas. The high transporta- tion charge for the processed perlite limits its economical shipping range, and other lightweight aggregates have found greater application in the states to the east. Facilities for processing perlite ore are presently being developed in other areas, and a much wider use of perlite concrete can be expected in the future. The vitrified air cells in processed perlite give con- Crete made with this aggregate its high values as insulation, as accoustical concrete, and as a lightweight building strong material. It is a relativelyfiaggregate, and in the correct proportions with cement and water passes building code requirements. It has been used effectively as a monolithic pour over existing roofs for insulation and fireproffing, as building units, for refractory bricks, and in prefabri- cated roof slabs. Where sound-deadening is required, it is highly effective. Experiments show however, that the cement content of concrete made with perlite aggregate is much higher than that made with sand and gravel for the same strengths. This means an expensive concrete, but it is quite often justified by the saving in weight, and the gain of fire-proofing, insulation, and sound-deadening. The perlite used in these experiments came from two sources. Dantore fine aggregate came from the Gregg Lumber Company, Grand Rapids, Michigan, their ore coming from Oregon. PerAleX concrete aggregate and fine aggregate was obtained from the Alexander Film Company, Colorado Springs, Colorado. Both types of perlite showed distinct bleeding when enough.water was added to get the desired slump. Normal portland cement was used and no dispersion agent added. The use of air-entraining cement or an agent to create dispersion would help reduce the waterégain and bleeding. It is also suggested that the addition of fine sand be checked as a possible remedy for this condition. Suggestions as to further experimentation with perlite aggregates include:- (1) methods to control water-gain and bleeding (2) determination of bond strength (3) determination of the required proportions of cement and aggregate to obtain given compressive and flexural strengths- PUMICE Pumice is a siliceous mineral of volcanic origin. It is a white or gray porous, glassy froth, containing numerous elongated, parallel cells. Because it is volcanic in origin, the only sources of pumice in the United States are in the Western region where volcanoes were once active” Pumice is mined from open pits and then screened for use as aggregate. Only a small fraction mined is oversize and requires crushing. The pumice obtained from acceptable deposits is quite uniform in composition and strength. Widest use of pumice aggregate for concrete is found in the West where the deposits are readily available and the transportation charges are not excessive. The distant lo- cation of the mines has made it difficult for pumice to economically compete with other lightweight aggregates in the East and Middle West. Pumdce concrete is more expensive than conventional concrete, but possesses the advantages of being lighter in weight, sound deadening, having a low thermal conductivity, being nailable, and easily handled. Pumice concrete has a lower modulus of elasticity than sand and gravel concrete, giving it reduced brittleness- a distinct Vihtue in earth- quake areas. Because it is strong as well as light in weight, pumice concrete is used for additional stories on existing buildings, and for structures where foundation loads are limited. Its insulation qualities make it desirable for application where fireproofing or low thermal conductivity is required. .As accoustical concrete, it is used in walls of theatres and auditoriums, and is especially effective when given a rough finish. Its ability to be nailed and aawn makes it easier to install windows, doors, or parti- tions. As evidence of the increased use of pumice as a lightweight concrete aggregate, the producers of pumice are presently organizing to secure uniform standards for the material, and to exchange existing technical infor- mat 10311 0 EXPANDED SLAG Expanded slag aggregate is made by treating molten blast furnace slag with controlled amounts of water. Thb process causes the slag to expand and become cellular in structure. The expanded material is then crushed and graded in sizes from 3/8 inch to dust. Production of slag aggregate is dependent upon the steel industry for blast furnace slag. Extensive use of this aggregate is found in the East and Middle West where the steel industry centers. The Cellular structure of expanded Slag and its ac- companying dead air spaces provide its value as a sound and heat insulator, and as a fire resistant material. Used in concrete, it is strong and durable, and is used extensively as a monolithic pour and in masonry units. Concrete made from expanded slag has found application in such structures as commercial and institutional buildings, industrial plants, apartment houses, and residences. Its lighter weight means greater ease of handling. It is an excellent insulator against heat and sound, has great fire resistance, and is easily mailed, out, or channeled. Expanded slag aggregate used in the concrete for test- ing was obtained from the Atlas Brick and Block Company, East Lansing, Michigan. The concrete made from this aggregate was very harsh, and considerable bleeding and water-gain was noticed. Slag aggregate is by nature very abrasive. The lack of sufficient fine material and dust was evident. Experiments by others have shown that the addition of fine, silicious sand materi- ally reduces both the harshness and the bleeding. It has also been found that admixtures are not as effective as sand in controlling this condition. Further experiments with slag concrete should include:- (1) attempts to reduces the harshness and bleeding, using— (a) fine, silicious sand (b) admixtures (2) the determination of the prOperties such as:— (a) compressive strength (b) flexuaal strength (c) accoustical and insulation values. CINDERS Cinders are a vitrified waste product obtained from industrial furnaces burning bituminous coal. After crushing, cinders are graded for use in concrete. Cinders are generally available in any locality depen- ding on coal for heat,light, and power. Although they were once to be had for the hauling cost, the popularity of ’ masonry units using cinders has helped to raise their price. A lightweight, strong, and porous aggregate, cinders are chiefly used to make masonry units, popularly called "cinder blocks". They make an attractive and relatively inexpensive unit, being as strong as concrete made from sand and gravel, considerably lighter, and possessing better qualities of insulation and sound-deadening. Cinder blocks can.be used nearly any place where concrete blocks are adaptable. Many examples of buildings using these units can be found in areas where cinders are economically available. Cinders used for testing were abtained from Standard Block and Supply, Lansing, Michigan. The standard practice of adding sufficient sand to fill the voids was followed. Used alone in concrete, cinders make a very harsh mix. The addition of sand materially reduces the harshness, and controls bleeding to a great extent, but adds to the unit weight of the concrete. The most economical combination of sand and cinders must be determined by trial mixes, because of the variation of gragation of the aggregates depending on their source. Further work with cinder concrete should include experiments to determine:- (1) bond strength (2) the effect on bleeding and harshness using various combinations of sand and cinders (3) its utility as structural member, observing:- (a) compressive strength (b) flexural strength (c) insulation and accoustical properties. EXPANDED SP' E AND CLAY EXpanded shale and clay aggregates are generally made by heating the previously crushed raw material in a rotary kiln to temperatures of plus 2000 F. The escaping gases are trapped, forming expanded cellular structures. After cooling, the aggregate is crushed and graded to various sizes. This aggregate is commonly called Haydite, the name under which this expansion process was first patented. Production of expanded clay aggregates is carried on throughout the country, and producing plants are generally located near acceptable deposits of shale of clay raw material. The development of aggregates of this type is assuming extreme importance, because it means that a raw material found in many parts of the country can be used to make an aggregate which is very often superior to sand.and gravel for use in concrete. Extensive investigation of other methods of expansion are presently being carried on to make more available and less expensive aggregates from shale and clay. EXpanded clay aggregate concrete approximates the strength of concrete made with sand.and gravel with the same cement factor. In addition, it weighs one-third less, and is superior to conventional concrete in fireproofing, in- sulation against sound and heat, and durability under ex- treme conditions. Concrete made with this material has found its ideal use throughout the country in all types of structures where lightness in weight is desirable or necessary. It is more expensive than conventional concrete, but because it possesses the advantages of lightness, excellent strength, fireproofness, and insulation, it very often effects economy in the long run. Its popularity and universal use is attested to by a statement made by the Haydite producers that " nearly every city over 200,000 population in the United States and south- ern Canada has some Haydite concrete construction." Being one of the first of the lightweight aggregates to be used in modern concrete construction, expanded shale and clay hasbeen extensively tested in monolithic concrete and in precast masonry units. DISTRIBUTION OF LIQHTWEIGHT AGGREGATE DEPOSITS AND PRODUCERS IN THE UNITED STATES The following map depicting the areas containing de- posits of lightweight aggregate ares, and the overlay show- ing the location of lightweight aggregate producers, were reproduced from information obtained from the Office of the Housing Expediter, Washington 25, D.C. LOCATION OF PRODUCERS OF LIGI-ET'i-JEIGITT AGGREGATES <1 <1 0 (I <1 0 <1 0 <3 <3 <6. <1 <1 q * <1 $4 (1° (Pd < o 0 q 0 <1 <11 <1 <1