Effect of internal curing on characteristics of self-compacting concrete by using fine and coarse lightweight aggregates

摘要

Internally cured concrete made with prewetted lightweight aggregates (LWAs) has a risk of segregation because of floating LWAs in the process of vibration. Such risk can be reduced by applying internal curing in self-compacting concrete, because it can avoid vibration or rodding processes. In this study, internally cured self-compacting concretes with fine or coarse LWAs were prepared with a replacement level of 20 and 40% by volume of normal-weight aggregates. A segregation resistance test was performed to quantitatively evaluate the floating of LWAs in self-compacting concrete. The effectiveness of internal curing was evaluated in terms of workability, compressive strength, autogenous shrinkage, and transport properties (i.e., water absorption, water desorption, and chloride resistance). Transport properties were also examined for internally cured mortar, which has identical ingredient proportions to the corresponding concretes used for comparison. The results showed that internal curing is useful in reducing the autogenous shrinkage of self-compacting concrete, and no segregation was observed for the fresh concretes. It was also found that the fine LWAs exhibited a better performance in reducing autogenous shrinkage and improving the transport properties compared with the coarse LWAs. The comparison of water absorption test results between a mortar and its corresponding concrete reveals that an increase in the volume fraction of normal-weight aggregates may decrease the effectiveness of internal curing.