Management of the nation’s aging transportation infrastructure constitutes a growing financial burden. Limited resources are available for inspection, maintenance, repair, rehabilitation and replacement of the deteriorating infrastructure. More efficient management of the aging concrete-based transportation infrastructure would allow for effective use of available resources to maintain a viable transportation system. Development of compact, lightweight and economically viable equipment for implementing some analytical chemistry methods have facilitated their growing semi-destructive or nondestructive field applications (e.g., in the field of geology). Initial efforts to make direct use of these methods for semi- or non-destructive field evaluation of concrete, however, have encountered challenges associated with the heterogeneity of concrete structure, and the complexity of concrete structure and deterioration mechanisms. Nuclear Magnetic Resonance (NMR) spectroscopy and relaxometry provide means of resolving and quantifying the chemistry of chemical compounds in various materials. Advances have been made in recent years towards applications of NMR for nondestructive inspection in the fields of manufacturing, arts and health sciences. These advances open the prospects for nondestructive evaluation of the concrete-based infrastructure with portable NMR systems.In this research for the first time a comprehensive experimental approach is adopted to investigate the effects of various deterioration mechanisms of concrete on the NMR relaxation signals of water confined in concrete pore network using a portable NMR device. The relaxation parameters such as transverse and longitudinal relaxation times and self-diffusion coefficients are obtained for concrete exposed to accelerated aging conditions. These parameters are obtained on the surface and in the depth of concrete at various stages of deterioration. At the same time, corroborative measurements are obtained using UPV and elastic modulus tests, as well as the microscopy observations. In case needed, other tests such as XRD, XRF and other analytical techniques are utilized to further investigate the structure of concrete. Moreover, field data is obtained by testing the existing concrete structures with unknown caused of the damage. The obtained data are compared with established trends of concrete specimens. In this work, the NMR trends of associated with various concrete deterioration mechanisms are identified and discussed. These trends are established over time at different depths of concrete exposed to various deterioration mechanisms. Moreover, a numerical study is performed to estimate the porosity and permeability of concrete using a numerical model that receives NMR relaxation data and predicts the properties of porous materials. In this model the NMR-derived fractional volumes of free and bound fluid, logarithmic mean values of relaxation times and empirically determined constant which depends on the surface relaxivity are incorporated. Results from this study will help engineers to identify the cause and extent of damage in existing concrete infrastructure. Additionally, it helps the researchers to study and characterize the damage to concrete structure caused by various deterioration mechanisms from a fresh perspective.
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