Characterization and analysis of the self-healing behavior of alkali-activated slag mortar

Alkali-activated slag (AAS) mortar has substantial limitations owing to its autogenous shrinkage, which leads to crack formation, and the self-healing property presents a promising solution to maintain its integrity and durability. Based on this, the self-healing efficiency of AAS mortar under a stable alkaline environment was assessed, with exogenous calcium ions introduced via a Ca(OH)₂ solution, and the self-healing mechanism was investigated with exogenous carbonate ions introduced to promote carbonation. To evaluate the effectiveness of these methods, both the physical properties and the microstructural characteristics of the AAS mortar under different healing environments were analyzed. The results revealed that self-healing environments, including secondary alkali activation and carbonation, substantially improved the rates of compressive strength recovery to 97.96 % and permeability recovery to 32.1 %. AAS mortar samples immersed in a saturated Ca(OH)₂ solution with wet-dry cycles, as well as those alternatingly immersed in Ca(OH)₂ and Na₂CO₃ showed higher matrix-crack bond strength recovery rates (43.7 % and 23.1 %, respectively) than samples exposed to only a saturated Ca(OH)₂ solution (11.4 %). The predominant healing products, including CaCO₃ and calcium aluminum silicate hydrate, effectively bonded to the cracks, contributing to significant recovery of the physical properties. Thus, the optimal self-healing of the AAS mortar requires an alkaline environment with abundant calcium ions to improve CaCO₃ precipitation. Additionally, continuous carbonation with exogenous carbonate ions further improves the healing efficiency. © 2025 Elsevier Ltd.