SBIR Phase I: Microwave Molecular Dynamics of Bound Water in Hydrating Cements

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This Small Business Innovation Research (SBIR) Phase I project will demonstrate the correlation between bound-water dielectric relaxation observed by broadband permittivity measurement and the degree of hydration in Portland cement, and apply the results to the refinement of a concrete cure monitoring system under development at the company. Complex permittivity over the frequency range 10 kHz to 10 GHz in curing cement shows signal components due to 1) free-water behavior near 10 GHz which decreases during cure and follows percent hydration, and 2) bound-water behavior between 1-1000 MHz which increases during early hours of cure and decreases and broadens thereafter. The bound-water relaxation does not appear in the initial cement paste but does appear after several hours of cure, mirroring the formation of hydration products to which it is attaching. This behavior will be elucidated by varying initial chemistry and determining effects on signal, quantifying changes in relaxation frequency and amplitude with cure time and fitting to appropriate models. The commercial potential of this project is in the construction industry.