Enhancing the Self-sensing Performance of Hybrid MWCNT-NCB Cementitious Composite and Its Piezoresistive Performance to Temperature Exposure

The piezoresistive behaviour of smart intrinsic composites incorporating carbon nanomaterials within Ordinary Portland Cement (OPC) matrices has been widely studied. However, these composites typically exhibit limitations in mechanical performance and long-term piezoresistive stability, particularly after exposure to elevated temperatures, and often demonstrate low stress sensitivity. Therefore, this study investigates the use of calcium aluminate cement (CAC) as a thermally stable alternative to OPC by incorporating a hybrid multi-walled carbon nanotubes (MWCNT) and nanocarbon black (NCB) to improve both the mechanical and piezoresistive properties of the composites. An optimized MWCNT/NCB concentration of 0.75/0.60 wt.% resulted in a remarkable fractional change in electrical resistance (FCR) of −44% with a stress sensitivity of 7.5% MPa⁻¹ at ambient temperature. Notably, this performance further improved after exposure to 200 °C, achieving an FCR of −49% and a stress sensitivity of 8.5% MPa⁻¹. Furthermore, the piezoresistive response under cyclic compressive loading at various rates was evaluated. The smart intrinsic composite consistently demonstrated excellent piezoresistive performance, characterized by enhanced FCR and stress sensitivity across a range of stress amplitudes and loading rates. These findings revealed the significant potential of CAC-based hybrid MWCNT-NCB composites as reliable self-sensing materials for structural health monitoring (SHM), capable of maintaining robust performance across diverse environmental and loading conditions.