Enhancing the self-sensing capacity of nanocarbon black-doped calcium aluminate cement composites after high-temperatures exposure

Nanocarbon black (NCB)-filled composites based on Ordinary Portland Cement (OPC) have demonstrated potential for real-time structural health monitoring due to their intrinsic piezoresistive properties. However, their practical application is limited by significant mechanical degradation and reduced stress-sensitivity after high-temperature exposure. This study addresses these limitations by developing and evaluating calcium aluminate cement (CAC)-based composites known for superior thermal stability compared to OPC. The results reveal that the CAC-based composites retain their mechanical integrity before and after exposure to high temperatures at 300 °C and exhibit enhanced self-sensing performance. At lower NCB concentrations, the compressive strength declined due to inadequate micropore filling. In contrast, incorporating 3.0 wt% NCB markedly enhanced mechanical and sensing performance, achieving compressive and flexural strengths of 86 MPa and 5.77 MPa, respectively, before high-temperature exposure. This was accompanied by substantial fractional changes in resistance (FCR) of 41 % and 21.20 %, with corresponding stress sensitivities of 3.42 %/MPa and 3.13 %/MPa, demonstrating the effectiveness of higher NCB content in reinforcing the composite and improving its self-sensing capabilities. After exposure to 300 °C, further hydration of anhydrous CAC in conjunction with silica fume led to enhanced mechanical properties and performance of NCB3.0, reaching 101 MPa (compression) and 7.73 (flexural), with improved FCR values of 41.6 % and 24.15 %, and stress sensitivities of 3.47 %/MPa and 3.13 %/MPa, respectively. These findings highlight the strong potential of CAC-based NCB-doped composites as robust, thermally resilient materials for advanced self-sensing applications in harsh environments, where both structural integrity and sensing are crucial.