Early-Age Properties of Cement-Based Materials. II: Influence of Water-to-Cement Ratio

The influence of water-to-cement mass ratio (w/c) on early-age properties of cement-based materials is investigated using a variety of experimental techniques. Properties that are critical to the early-age performance of these materials are tested, including heat release, semiadiabatic temperature, setting time, autogenous deformation, and strength development. Measurements of these properties using a single cement are presented for four different w/c, ranging from 0.325–0.425. Some of the measured properties are observed to vary widely within this range of w/c ratios. The heat release and setting time behaviors of cement pastes are contrasted. While early-age heat release is relatively independent of w/c, the measured setting times vary by several hours between the four w/c investigated in this study, indicating the fundamental differences between a physical process such as setting and heat release, which is purely a quantification of chemical reaction. While decreasing w/c certainly increases compressive strength at equivalent ages, it also significantly increases autogenous shrinkage and may increase semiadiabatic temperature rise, both of which can increase the propensity for early-age cracking in cement-based materials.