Abstract
Hydration studies done several years ago by R.H. Mills, built on the work of T.C. Powers and other researchers to derive a relationship between the ultimate degree of hydration and water-cement ratio (w/c). This paper reviews the αult-w/c hydration equation for possible application to w/c estimation in hardened concrete. Unlike current methods, the empirical method based on hydration equation has the merit of simplicity but its accuracy has not been tested and proved. A χ2-test statistic showed a good agreement between values of original w/c and estimated w/c for pastes hydrated for 448 days. Accuracy seemed particularly good for mixtures of portland cement only. The method is sensitive to the C3A content while use of extenders in mixtures appears to reduce accuracy. These and other shortcomings are discussed including the effects of advances in cementitious material systems. The need for modifications and development towards an improved method is highlighted.