Effect of coarse aggregate content on shear friction of concrete

Shear friction behaviour of normal- and high-strength concretes made with different amounts of coarse aggregate was investigated in this study. A total of 48 push-off specimens were made and tested. Twenty-four of the specimens were made with normal-strength concrete; the rest were made with high-strength concrete. The test variables included the concrete strength, coarse aggregate content and amount of shear reinforcement. The results show that an increase in coarse aggregate content would increase the splitting strength of concrete cylinder, ultimate shear friction strength and shear ductility of the push-off specimens for normal-strength concrete. However, there should be an upper bound of 950 kg/m³ to ensure better ultimate shear friction strength and ductility for high-strength concretes. The same amount of coarse aggregate could be the lower bound for normal-strength concretes to achieve the code-specified splitting strength. The ACI code shear friction strength calculations are conservative. The λ modification factor for normal-weight concrete as specified in the code may be raised up to 1·3, which was the lower bound found in this study.