Study on the effect of carbonized recycled coarse aggregate admixture on the properties of self-compacting concrete

In order to analyze the effect of carbonated recycled coarse aggregate (RCA) on the mechanical and chloride ion penetration resistance of self-compacting concrete (SCC), recycled self-compacting concrete (RCASCC) was prepared with RCA treated with different admixtures (15%, 30%, and 50%) and different carbonation pressures (0, 75 kPa, and 150 kPa), and was tested for its compressive strength, flexural strength, electric flux, and its pore structure and micro-morphology were analyzed. The results show that RCA substitution rate and carbonation pressure have a significant effect on the compressive strength, flexural strength and electrical flux of RCASCC, with the increase of RCA dosage, the compressive strength of RCASCC firstly increases and then decreases, while its electrical flux firstly decreases and then increases; with the increase of RCA carbonation pressure, the compressive strength of RCASCC gradually decreases while its electrical flux gradually increases; the increase of RCA dosage and carbonation pressure both reduce the compressive strength of RCASCC, while its electrical flux firstly decreases, while the increase of RCA dosage and carbonation pressure gradually increases. Increasing the RCA doping and carbonization pressure both reduce the flexural strength of RCASCC; when the RCA doping is 30% and the carbonization pressure is 75 kPa, the 28d compressive strength and chlorine ion permeation resistance of RCASCC are improved by 10.3% and 20.9%, respectively, and the pore size of the pre-wetted RCASCC is refined, and the interfacial transition zone is structurally dense.