Experimental study on the failure mechanism of recycled concrete

In this study, Young's modulus, strength, and peak strain of recycled concrete under both compressive and tensile loading were experimentally studied to understand its failure mechanism. Due to the different colors of natural aggregates, old hardened mortar, new hardened mortar, and interfacial transition zone (ITZ), the quantity and the distribution of each phase were analyzed by images processing and analysis of cut sections. With the tests, the failure processes and crack situation of the recycled concrete under tensile and compressive loadings were illustrated. It was found that some mechanical properties of recycled concrete are similar to those of mortar, for instance, lower Young's modulus, higher peak strain and more brittleness, due to a larger volume content of both new and old hardened mortar. When compared with old hardened mortar, new hardened mortar has more significant influence on both the strength and the Young's modulus of recycled concrete.