Effects of specific admixtures on autogenous shrinkage of self‐compacting concrete containing recycled coarse aggregate: Nano‐ CaCO ₃ , slag powder, and superabsorbent polymer

Recycled aggregate self‐compacting concrete (RASCC) is susceptible to early‐age autogenous shrinkage due to characteristics of recycled coarse aggregate (RCA), especially under binder‐rich, low‐water‐to‐binder conditions. This study investigated the effects of RCA replacement ratio, nano‐CaCO 3 , slag powder, and superabsorbent polymer (SAP) on the autogenous shrinkage, mechanical properties, and microstructure of RASCC. Results showed that 100% RCA increased the autogenous shrinkage strain at 28 days by 55.46% compared with the control. Considering both mechanical performance and shrinkage control, the recommended dosages are 0.5%–1.0% for nano‐CaCO 3 and 10% for slag powder, which improved compressive strength but increased shrinkage, whereas 0.3% SAP reduced shrinkage by 16.67% and 20.29% at 3 and 28 days, respectively, through internal curing. A prediction model for autogenous shrinkage of RASCC containing these admixtures was established. These findings provide a quantitative basis for optimizing RASCC mixtures and controlling early‐age shrinkage in sustainable construction.