Residual piezoresistive properties of mortars containing carbon nanomaterials exposed to high temperatures

This study investigated the viability of using smart cement-based composites containing multi-walled carbon nanotubes (MWCNT) or carbon-black nanoparticles (CBN) for Structural Health Monitoring of fire-damaged concrete structures. A total of 112 composites were produced with different nanofiller concentrations, exposed to distinct heat treatments, and subjected to electro-mechanical tests. The results elucidated the influence of temperature on their residual capacitance, conductivity, and piezoresistivity. The thermal decomposition of nanofillers was investigated through thermogravimetric analysis and Raman spectroscopy. The sensing ability of smart composites was improved after exposure to 200 °C. Composites with 0.8% or 1.2% of MWCNT exhibited adequate residual self-sensing ability after exposure to temperatures up to 400 °C. Mortars containing 6% or 9% of CBN exhibited residual self-sensing ability after temperatures up to 600 °C. Composites with 9% of CBN also exhibited an interesting ability of self-detection of damage due to fire. •The viability of using smart mortars for SHM of fire-damaged structures was investigated.•Residual sensing ability of mortars with CBN or MWCNT exposed to high temperatures was reported.•Mortars with high CBN content exhibited self-detection of damage due to fire exposure.•Raman spectroscopy was used to detect fingerprints of remaining nanofillers in fire-damaged mortars.•A 200 °C heat treatment improved the sensing ability of smart composites with CBN or MWCNT.