Experimental and Numerical Assessment of Restrained Shrinkage Cracking of Concrete Using Elliptical Ring Specimens

摘要

A new experimental method is proposed for assessing the cracking tendency of concrete using elliptical ring specimens subject to restrained shrinkage. To explore the mechanism of this method, a numerical model is developed to analyze stress development and crack initiation in concrete rings in which the effect of concrete shrinkage is simulated by a fictitious temperature drop applied on concrete causing the same strain as that induced by shrinkage. Stress developed in a concrete ring is then obtained through a combined thermal and structural analysis. Based on the maximum tensile stress cracking criterion, numerical results are in accordance with experimental results on cracking age for a range of circular and elliptical concrete rings with different geometries. Geometrical factor, i.e., the ratio between the major and minor semiaxes of an elliptical ring, is the main factor that affects tensile stress developed and consequently concrete cracking age in restrained ring specimens. Elliptical rings with appropriate geometry can enable crack initiation much earlier than circular rings, which consequently are able to accelerate the ring test for assessing the cracking potential of concrete. Discussions are made on effects of ring geometry on features of cracking, crack position, and stress development in concrete rings subject to restrained shrinkage to further explore the mechanism of the elliptical ring test for assessing the cracking potential of concrete.