Piezoresistive cementitious composites for intelligent civil infrastructure

Nano-carbon blacks (NCBs) are promising conductive fillers for developing self-sensing cementitious composites owing to their excellent electrical conductivity and cost-effectiveness. In this study, cementitious composites containing 0.0–16.0 wt.% NCBs were fabricated to investigate the coupled electrical, mechanical, and piezoresistive behaviors using both direct current (DC) and alternating current (AC) measurements at different curing ages. The results showed that electrical resistivity decreased by nearly five orders of magnitude with increasing NCB content, and the percolation threshold was identified within 4.0–12.0 wt.%. Low NCB dosage slightly improved mechanical performance due to nano-filling and nucleation effects, whereas excessive NCB incorporation caused strength deterioration because of agglomeration. The composites containing 12.0 wt.% NCBs exhibited the optimal piezoresistive performance, with maximum stress sensitivities of 1.48 and 1.91%·MPa−1 under cyclic and monotonic compression, respectively. This study provides a comprehensive understanding of the multi-scale conductive mechanisms and electromechanical behaviors of NCB-based cementitious composites.