Pressure Sensitivity Analysis of Nanosilver and Modified Carbon Nanotube Self-sensing Cementitious Under Various Loading Regimes

Self-sensing cementitious materials enable real-time, long-term, and intelligent digital monitoring of structures, providing a novel approach to structural monitoring. However, challenges such as the difficulty in dispersing conductive fillers, high costs, and the need for large amounts of admixtures hinder their practical application. In this study, a low-temperature plasma modification technique is utilized to enhance the hydrophilicity and dispersion of carbon nanotube (CNT) materials while minimizing surface damage. In addition, the study innovatively incorporates a pressure-sensitive material, silver nanoparticles (AgNPs), which have significant potential in smart wear applications, into the cement matrix. The pressure sensitivity of CNT and AgNPs, two conductive fillers in the cement matrix, is analyzed through three loading regimes: equal amplitude loading, variable amplitude loading, and frequency loading under long cycles. The polarization trends of both specimen groups remain consistent. As the cementitious material ages, the polarization end time increases gradually from 4～5 min at 14 d to about 1.0 h at 28 d, eventually stabilizing at about 1.5 h. Cyclic loading tests with equal amplitude revealed that AgNPs achieve significantly higher pressure-sensitive stability than P–CNT at a very low doping level of 0.004 8%, effectively reducing the required filler content. Experimental results from variable amplitude tests indicated that the stress sensitivity of AgNPs is more than three times higher than that of P–CNT under the same amplitude conditions. SEM analysis showed that excessive stress amplitude loading damages P–CNT fibers, negatively affecting their pressure-sensitive performance. The variable-speed cyclic loading test demonstrated that long-cycle cyclic loading or high-speed loading enhances the stability of the self-sensing cementitious pressure-sensitive curve.