Modified Reinforcement and Splitting Tensile Strength Factors in ACI 318 Shear Strength Formula for Concrete Without Coarse Aggregate

The tensile strength of concrete plays an important role in predicting the shear strength provided by concrete. In this research, the contribution of longitudinal reinforcement ratio to the shear strength of concrete beams without coarse aggregate is evaluated by considering the splitting tensile strength of concrete. The splitting tensile test has been conducted to six cylinders with compressive strengths ranging from 50.87 to 60.67 MPa in order to determine the concrete splitting tensile strength according to ASTM C496. From the test results, a constant splitting tensile strength factor of 1.3 has been proposed for concrete without coarse aggregate. By using this factor, the effect of the longitudinal reinforcement ratio on the shear strength of concrete has been calibrated to the test results of 12 concrete beams without coarse aggregate. The beams with compressive strengths ranging from 50.3 to 110.4 MPa and varying longitudinal reinforcement ratios have been tested by using a four-point bending test. An exponent factor of 0.5 for the effect of reinforcement has been proposed as a modification to ACI 318 shear strength formula to predict shear strength of high-strength concrete without coarse aggregate. The proposed formula results in average experimental to the predicted shear strength ratio of 1.184.