Performance improvement for the roller shooting mortar via crystalline admixture: from microstructure to self-healing

Abstract Prestressed Concrete Cylinder Pipe protective layer mortar is molded by roller shooting process and plays a critical role in preventing corrosion of prestressed wires. During the roller shooting process, the mortar particles undergo high-speed impact and compaction, forming a dense structure with closely packed particles. This structure retains a significant amount of unhydrated cement particles, which provides excellent rehydration potential, thus promoting crack self-healing. To enhance the self-healing performance by activating the unhydrated cement, this study investigates the effects of crystalline admixture (CA) on the comprehensive performance enhancement of the roller shooting mortar. The results reveal that CA facilitates the generation of hydration products through crystallization effects and optimizes the pore structure (porosity reduced by 36.27%), leading to significant improvements in the mortar’s physical-mechanical properties, impermeability, and resistance to chloride ion penetration. During the cracking stage of the protective mortar, CA exerts a complexation effect that activates the unhydrated cement particles, increasing the healing rate by 130% and accelerating the healing process. Microscopic analysis reveals that the healing products composed of C–S–H gel and calcium carbonate. CA promotes the generation of C–S–H gel and increases the calcium carbonate content by 59.79%. This study provides a technical approach to mitigating cracking issues in roller shooting mortar.