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 degrees C. Composites with 0.8% or 1.2% of MWCNT exhibited adequate residual self-sensing ability after exposure to temperatures up to 400 degrees C. Mortars containing 6% or 9% of CBN exhibited residual self-sensing ability after temperatures up to 600 degrees C. Composites with 9% of CBN also exhibited an interesting ability of self-detection of damage due to fire.