Autogenous shrinkage model for concrete with weathered steel slag coarse aggregate

Weathered steel slag coarse aggregate concrete-filled steel tubes (SACFST) offer a promising solution for enhancing the utilization of steel slag in sustainable construction. While the static and dynamic behaviors of SACFST have been increasingly studied, its shrinkage behavior remains largely unexplored. In SACFST, only autogenous shrinkage occurs because the concrete core is sealed by the outer steel tube. The autogenous shrinkage behavior of SACFST is expected to differ significantly from that of natural aggregate concrete-filled steel tubes due to the substantial difference in stiffness between steel slag coarse aggregate (SCA) and natural coarse aggregates (NCA). This study investigates the long-term autogenous shrinkage behavior of concrete incorporating weathered SCA through 1174-day experiments on 18 specimens with varying SCA substitution ratios (0 %, 50 %, and 100 %) and water-to-binder ratios (0.3 and 0.5). The effects of SCA on autogenous shrinkage were systematically analyzed, and its varying impacts at different water-to-binder ratios were quantified. Using the two-phase composite method, a theoretical model was derived to predict the autogenous shrinkage of steel slag aggregate concrete, accounting for the influence of SCA stiffness. Investigations show that: (1) Sealed concrete with weathered SCA exhibits no expansion deformation after 1174 days; (2) the reduction in autogenous shrinkage due to SCA is more pronounced at higher water-to-binder ratios; (3) the proposed model accurately predicts the autogenous shrinkage of steel slag aggregate concrete, with R² value of 0.994 for predicted results.