Experimental research on the size effect of mortar and concrete specimen

Abstract

The experiment was performed to investigate the influences of specimen dize and initial notch length on tensile strength, fracture toughness KIC, fracture energy G$_f$, and notch sensitivity of concrete. The splitting tensile test for cylindrical specimen was employed because the splitting test is simple to perform and gives more uniform results than direct tensile or flexural tensile test. The specimens were tested for diameters of 10, 20, 40, and 80 cm with the same length 18.8 cm. The ASTM standard test method (C496), "splitting tensile strength of cylindrical concrete specimens", was followed as closely as possible. The results show that size effect appears conspicuously. As the specimen sizes increase, the splitting tensile strength of the specimen, regardless of initial notch length ratio, was shown to decrease. But the decreasing rate of strength is gradually reduced after an obvious strength drop. The fracture energy and the fracture toughness, which are very important parameter in fracture mechanics, were calculated with several methods. The change of notch sensivity, along to the increase of specimen size, was obtained.