Effect of water content on the piezoresistive property of smart cement-based materials with carbon nanotube/nanocarbon black composite filler

A carbon nanotube (CNT)/nanocarbon black (NCB) composite filler was incorporated into cement matrix to develop smart cement-based materials with piezoresistive property. However, the effect of water on the cement-based materials with CNT/NCB composite filler is not easy to avoid in practical engineering. Therefore, in this paper, the effect and mechanisms of water content on the piezoresistive property of cement-based materials with CNT/NCB composite filler are investigated. Cement-based materials with fillers feature the piezoresistive property under different water contents. However, the maximum fractional changes in electrical resistivity, stress sensitivity and strain sensitivity all decrease with the reduction in water content. The maximum values of fractional change in electrical resistivity, stress sensitivity and strain sensitivity of the cement-based material with 2.14 vol% of filler change nonlinearly from −12.94% to −6.80%, 3.15%/MPa to 1.70%/MPa, and 389 to 202, respectively, with decreasing water content. With the reduction in water content, the decrease in contact resistance between fillers and the increase in the composite shrinkage result in a decrease in the sensitivity of the piezoresistive property.