Development of a damage-recovery relationship based on variable re-curing of fire-damaged high-strength mortar

Repair utilizing re-curing has the potential to restore strength and durability without removal and casting operations, thus reducing waste generation and material consumption. In this research, the effect of different post-fire cooling and re-curing conditions on the behavior of high-strength mortar was investigated. After removal from heating, specimens were placed in air or water conditions, and unstressed compressive strength and mercury intrusion porosimetry tests, as well as an epoxy injection process to observe the cracking pattern, were performed in order to understand the relationship between damage and recovery mechanisms. Results showed that air re-curing resulted in the formation of surface cracks due to differential thermal shrinkage, reducing strength. Immediate water submersion also resulted in large strength reductions, but was followed by strength, porosity, and crack recovery due to rehydration. Specimens which were cooled in the air before water submersion underwent less strength loss but also recovered less during re-curing.