The effect of carbonated recycled coarse aggregate on the fracture properties of concrete

This study investigates the effects of carbonated recycled coarse aggregate (C-RCA) on the macro and micro fracture properties of recycled aggregate concrete (RAC). Three-point bending and nanoindentation tests are conducted on the RAC with a 50 % recycled coarse aggregate (RCA) replacement rate to study its micro/macro mechanical and fracture properties as well as their potential connections. The results indicate that C-RAC (RAC with C-RCA added) offers significant improvements in mechanical and fracture properties. The properties of macrofracture show dramatic enhancements in cohesive stress, fracture energy and initial fracture toughness, while critical cohesive toughness is reduced. The effects of the microscopic mechanical and fracture properties on the mechanisms of macroscopic behavior are evaluated and the results indicate that the improvements in macroscopic properties are due to significant increases in the reduced modulus, hardness, critical energy release rate and microscopic fracture toughness of old mortar on the RCA after carbonation.