Piezoresistive properties of well-dispersed carbon nanotubes (CNTs) modified cement paste

Abstract

When developing smart cement-based sensors with carbon nanotubes (CNTs) as conductive fillers, CNTs with good dispersion can enhance the conductivity and piezoresistive properties of cement-based materials. In this study, a combination of sonication and dispersant was used to disperse CNTs, and then investigated the piezoresistive properties of well-dispersed CNTs modified cement paste. The experimental results showed that the dispersant used was polyvinylpyrrolidone (PVP), and when the mass ratio of PVP to CNTs was 4:1, the sonication time was 25 min, and the standing time did not exceed 3 h, CNTs had higher dispersion quality. The resistivity of the cement paste decreased by two orders of magnitude with increasing CNTs dosage and exhibited visible percolation phenomenon with percolation thresholds ranging from 0.1 % to 0.3 %. The fractional change in resistivity, stress sensitivity and strain sensitivity of cement paste under cyclic loading reached the maximum values of 10.95 %, 1.146 %/MPa and 123.450 %, respectively, with high repeatability (92.63 %) and low hysteresis (8.40 %) when the content of CNTs was 0.4 %. At the same time, CNTs improved the microstructure of the cement paste, which positively affected the mechanical, electrical conductivity and piezoresistive properties of the material.