Optimizing pore structure of perforated cenospheres for effective internal curing of alkali-activated slag mortars

Based on the controllability of the pore structure of perforated cenospheres (PCs), this study utilized PCs with different etching concentrations for the internal curing of alkali-activated slag (AAS), aiming to achieve the optimal etching parameters for efficient internal curing. Three etching concentrations (0.3 M, 0.7 M, 1.0 M) were set to investigate the effects of water-filled PCs on the performance of internal curing of AAS mortars. The results indicated that the water released from the PCs delayed the hydration of AAS and maintained high internal relative humidity. The chemical shrinkage of AAS could be reduced. Water-filled PCs internal curing promoted the generation of hydration products around the PCs and increased their packing density, leading to a reduction in mesopores and a 12.7—27.7% increase in elastic modulus at 28 d. With the optimal etching concentration of 0.7 M, water-filled PCs significantly mitigate the autogenous shrinkage by 75.8% while enhancing the compressive strength of AAS mortars. •Three etching concentrations of perforated cenospheres (PCs) were investigated for the internal curing efficiency of AAS.•PCs internal curing increased the internal relative humidity and reduced the chemical shrinkage.•PCs internal curing enhanced the packing density and elastic modulus of hydration products.•The optimal 0.7 M etching concentration reduced autogenous shrinkage by 75.8% and enhanced compressive strength.