Failure processes of modeled recycled aggregate concrete under uniaxial compression

In order to investigate the failure processes of Recycled Aggregate Concrete (RAC), cracking behavior of modeled RAC specimens under compressive loading was investigated using Digital Image Correlation (DIC). Strain and displacement contour maps were produced to analyze the cracks’ initiation and propagation during loading. The testing results indicate that the discrepancy between the elastic moduli of coarse aggregates and mortar matrix significantly influences the mechanical properties and crack patterns of the modeled materials. It is found that the failure process is related to the relative strength of coarse aggregate and mortar matrix. For modeled RAC, the first bond cracks appear around both the old and new interfacial transition zones (ITZ), and then propagate into the old and new mortar matrix by connecting each other. The observation implies that the initiations and propagations of microcracks are different between RAC and Natural Aggregate Concrete (NAC). The findings in this investigation are useful to improve the mechanical properties of RAC by optimizing the mix proportion.