Updated internal curing for HPC using pore-regulated coal aggregates

An updated internal curing (IC) method was proposed using pore-regulated coal gangue aggregates (PCAs) for high-performance concrete (HPC). Calcination (200—400 °C) was applied to regulate the pore structure of PCAs to achieve an optimal one. The pore structure, morphology, water absorption, and water desorption of PCAs were tested. Their effects on the fluidity, internal relative humidity (IRH), autogenous shrinkage, compressive strength, micromechanical properties, and microstructure of HPC were studied. The results demonstrated that calcination significantly increased the porosity of PCAs by 19.57—34.95 %, particularly within the mesopores ranging from 30 nm to 1 μm, which led to a 29.38—81.12 % increase in the water absorption capacity of PCAs, as well as the improvement of water desorption efficiency. The incorporation of PCAs sustained the IRH of HPCs at elevated levels and reduced the autogenous shrinkage by 44—55 %. The improved IC efficiency facilitated the deposition of more hydration products and enhanced the interfacial transition zone (ITZ), contributing to refined pore structure and a 1—7.92 % increase in compressive strength at 28d.