Carbonated recycled coarse aggregate and uniaxial compressive stress-strain relation of recycled aggregate concrete

Carbonation treatment was employed to improve the quality of recycled coarse aggregate (RCA), and the RCA or carbonated RCA (CRCA) was used to prepare recycled aggregate concrete (RAC or RAC-C). The influence of the RCA replacement rate and CRCA on the mechanical properties and stress-strain relation of concrete was investigated. The results have shown that carbonation treatment enhances the physical properties and interfacial transition zone (ITZ) of CRCA, and effectively prevents the degradation in mechanical properties of concrete. Increased RCA or CRCA replacement rate reduces the peak stress and ascending slope and increases the peak strain of RAC or RAC-C. The stress-strain curve of RAC-C has higher ascending slope, peak stress and lower peak strain than that of RAC and is closer to that of natural aggregate concrete (NAC) due to the improved new ITZ. The stress-strain relation result agrees well with the proposed model.