STUDY ON THE EFFECT OF AGGREGATE VOLUME FRACTION ON DYNAMIC ELASTICITY IN HARDENING PROCESS

Abstract

In this contribution, velocities of elastic wave and shear wave were obtained by ultrasonic pulse method with hardening cement paste and mortar whose water to cement ratio was 0.30, 0.40 and 0.55. And four classes（cement paste, 20%, 40%, 60%）of aggregate volume fraction ratio were prepared in each water to cement ratios. Then, Poisson’s ratios and dynamic elasticity were calculated from experimental results of elastic wave, shear wave and bulk density at predefined concrete age. As a result, steep reduction of Poisson’s ratio was observed in early age in all specimens, however, decreasing ratio was different from each aggregate volume fraction. And it was reported that this time dependent changes of Poisson’s ratio made an influence to accuracy of composite model for predicting the dynamic elasticity in the case of the range over 40% volume fraction of aggregate. In that case, the estimated values were improved by taking time dependent changes of Poisson’s ratio into consideration. On the other hand, the estimated value by Hashin - Hansen model of mortar whose volume fraction of aggregate was 60% showed much higher value than measuring. And this difference was considered to be occurred due to large amount of void content than that of lower volume fraction of aggregate.