Behavior of fire-damaged mortar under variable re-curing conditions

An experimental investigation on the effect of post-fire cooling and re-curing conditions on strength and durability of normal- and high-strength cement mortars was conducted. Results showed that air re-curing resulted in the formation of surface cracks due to differential thermal shrinkage, which reduced the strength. An increase in air permeability indicated low durability; carbonation also occurred in these specimens. Immediate water submersion resulted in large strength reduction, but was followed by strength, porosity, and crack recovery due to rehydration, which also prevented carbonation. Specimens that cooled in the air before being submerged in water lost less strength but also recovered less quickly. A chemical analysis of the high-strength specimens found that growth in the pore structure could be attributed to the rehydration of hydration products that were dehydrated during heating. Complete strength recovery, however, was not observed, which may be attributed to the instability of self-healed cracks.