Degree of Hydration and Mass Balance Equations for Determination of Mix Proportion of Hardened OPC Concrete

A method for estimating mix proportion of hardened OPC concrete is proposed in this study. A set of mass balance equations was formed to calculate content of concrete compositions including cement, water, sand, and coarse aggregate. The degree of hydration of cement was taken into account in the analysis in order to cover the effect of age of concrete. In order to verify the accuracy of the proposed method, the determination of mix proportion of concrete was conducted on concrete specimens prepared in the laboratory with known mix proportions. Moreover, the mix proportion of concrete at different ages were calculated both with and without consideration of time-dependent degree of hydration in the analysis to clarify the enhanced capability of the proposed method when the effect of age of concrete is considered. It was found from the analytical results that the proposed method could be used to estimate mix proportion of concrete, with a satisfactory precision, at any age. The calculation of mix proportion of hardened concrete with consideration of time-dependent degree of hydration provided less error than that without consideration of the degree of hydration. The percentage of error of the mix proportion prediction of the concrete samples was less than 5%.