Experimental and Theoretical Studies on Autogenous Shrinkage of Concrete at Early Ages

Abstract

The magnitude of the shrinkage strain is normally proportional to the amount of moisture lost caused by drying or cement hydration. In this study, the development of internal relative humidity and autogenous shrinkage in early age samples of normal- and high-strength concrete were experimentally measured starting from the time of concrete casting. The experimental results show that the development of the internal relative humidity of concrete first follows a vapor saturated stage (RH=100%, Stage I), followed by a gradually reducing stage (RH<100%, Stage II). Shrinkage strain developed in Stage I and Stage II may be correlated with chemical shrinkage and interior humidity reduction, respectively. An autogenous shrinkage model based on aforementioned mechanisms is developed. The model predictions agree well with experimental measurements on the development of autogenous shrinkage in early age normal- and high-strength concrete.