Effects of Post-Fire Curing on Self-Sensing Behavior of Smart Mortars

Post-fire rehydration is an interesting method to recover the struc- tural performance of fire-damaged concrete. This paper evaluated the viability of using cementitious materials containing carbon nanotubes (CNTs) or carbon-black nanoparticles (CBNs) for damage recovery detection and self-monitoring of strain and stress of fire-damaged structures subjected to post-fire curing. Nano -modified mortars were subjected to high temperatures, rehydration, and measurements of capacitive behavior, electrical resistivity, and self-sensing properties. After 600 degrees C and rehydration, mortars with 9.00% of CBN presented the ability of self-detection of damage recovery, as also verified in mortars with 0.4 to 1.20% of CNT and 6.00% of CBN after 400 degrees C and rehydration. The post-fire curing method filled the pores and microcracks of the cementitious matrix with nonconductive rehydration products, increasing their elec- trical resistivity. Mortars with 0.80 and 1.20% of CNT presented self-monitoring of strain and stress after 400 degrees C and rehydration, as also observed in mortars with 9.00% of CBN after 600 degrees C and rehydration. The post-fire curing process also increased the self -sensing properties because nonconductive rehydration products obstructed conductive stretches, improving tunneling conduction mechanisms rather than contacting conduction. These self-sensing materials are promising alternatives to evaluate post-fire curing processes and self-monitor the strain and stresses of next-generation smart structures.