Studying Tensile Strength of the Recycled Coarse Aggregate Concrete Using Double-Punch Test

Using the recycled materials can be considered as a suitable solution for resolving environmental issues. The recycled coarse aggregates (RCA) can be utilized effectively in manufacturing structural concretes. Due to hardness and errors of direct tensile and splitting tensile tests, double -punch test (DPT) can be regarded as a reliable test method for evaluation of tensile strength.In this study, application of DPT was investigated as a less known method for RCA concretes considering effective factors, such as water–to-cement ratio (0.4, 0.5, and 0.6), maximum nominal size of RCA (10 and 19 mm), curing conditions (wet and dry), and replacement level of RCA (0, 50, and 100%) and the results were validated by direct tensile and splitting tensile test results. A statistical analysis was performed to indicate significance of each variable in DPT results of RCA concretes. Also, compressive strength and modulus of elasticity were assessed and their relationships with tensile strength of the specimens were studied.The maximum RCA size, replacement level of RCA, and mechanical properties were diminished in mixtures by increasing water-to-cement ratio. Generally, DPT results showed remarkable proximity to direct tensile test results with a slight increase. In wet curing condition, mean values of splitting tensile, DPT, and direct tensile tests in the specimens containing 19mm of RCA were 11.61, 10.06, and 9.44% higher than those containing 10mm of RCA, respectively. Moreover, results of statistical analysis showed that the studied factors had significant effects on the results and they must be regarded in evaluation of DPT.