Ceramics-Silikáty

To investigate the effect of pre-impregnating recycled aggregates with calcium hydroxide (CH) followed by pressurized CO₂ curing of recycled aggregates on the frost resistance of recycled concrete (RAC), rapid freeze–thaw tests were conducted on specimens with different recycled coarse aggregate (RCA) and recycled fine aggregate (RFA) replacement ratios. Mass loss, relative dynamic modulus of elasticity (RDEM), and microstructural characteristics were analyzed. The results indicate that the frost resistance of RAC decreases with increasing recycled aggregate replacement ratio. CH pre-impregnation combined with pressurized CO₂ curing effectively improves the freeze–thaw resistance of RAC. After 50 freeze-thaw cycles, the mass loss of treated RAC was 2.71%-4.59%, lower than that of untreated RAC. Meanwhile, the RDEM of treated RAC increased by 19.48%-60% at 100% RCA replacement and by 41.06%-60% at 100% RFA replacement. Microstructural analysis showed that carbonation products filled pores and microcracks in recycled aggregates and at the interfacial transition zone, thereby refining the internal structure and mitigating freeze-thaw damage. A freeze-thaw damage model based on RDEM was established and showed good agreement with the experimental results