Effect of water‐to‐cement ratio on internal relative humidity and autogenous shrinkage of early‐age concrete internally cured by superabsorbent polymers

Abstract

AbstractSelf‐desiccation is one common phenomenon of concrete with low water‐to‐cement (w/c) ratios, which may lead to the decrease of internal relative humidity (IRH), and therefore causing autogenous shrinkage (AS). Superabsorbent polymers (SAPs) are used as a kind of internal curing material to mitigate AS of concrete. The IRH and AS are significantly affected by the w/c ratio, and several attempts have been made to investigate the IRH or AS of concrete with different w/c ratios. However, the prediction model of AS considering IRH and w/c ratio of internally cured (IC) concrete is limited. In the present study, the effect of w/c ratio on IRH and AS of IC concrete was investigated, and a two‐stage prediction model of AS based on the results of IRH for IC concrete considering the effect of w/c ratio was proposed. The experiment results and analysis indicated that IRH of IC concrete increased as increase of w/c ratio, and development of IRH experienced two stages: a water‐vapor saturated stage with 100% RH (stage I), and a gradually reducing stage in which IRH decreased gradually (stage II); critical time of IC concrete increased as increase of w/c ratio; expansion peak of IC concrete increased as increase of w/c ratio; AS and AS rate of IC concrete decreased as increase of w/c ratio; IRH, critical time, and expansion peak of IC concrete were higher than that of ordinary concrete; AS and AS rate of IC concrete were lower than that of ordinary concrete.