The self-healing performance and mechanism of limestone calcined clay composites coupling with crystalline admixture in chloride-rich environments

Limestone Calcined Clay Cement (LC3) has shown potential for improving durability in concrete structures; however, its self-healing performance in chloride-rich environments, such as marine settings, remains underexplored. This study investigated the self-healing mechanisms and performance of LC3 composites exposed to seawater and NaCl solution, with a specific focus on determining how crystalline admixtures (CA) influence self-healing capacity. The addition of CA was found to enhance the self-healing capacity of LC3 by accelerating the formation of healing products, such as calcite and other crystalline phases, which effectively sealed cracks. Specifically, LC3 with CA achieved a crack healing ratio of up to 85.9 % in seawater after 84 days of exposure. Electron Probe Micro-Analyzer (EPMA) results demonstrated that LC3 with CA effectively limited chloride penetration in both uncracked and healed conditions compared to ordinary Portland cement, highlighting its superior chloride resistance while preserving its self-healing capacity. The self-healing products analysis identified calcite as the primary healing product in deionized water and sodium chloride solution, while more complex phases, such as brucite and aragonite, dominated in seawater. These findings suggest that LC3 combined with CA exhibits enhanced self-healing capacity and superior chloride resistance, making them a promising material for use in aggressive marine environments. • LC3 composite shows improvement in crack healing (up to 85.9 %) under seawater exposure. • Brucite and aragonite dominate as healing products in seawater. • LC3-CA achieves 42 % reduction in chloride ingress, enhancing durability. • Calcite is the primary healing product in Cl solution and DI water. • Comprehensive analysis covers deionized water, NaCl, and seawater environments.