Tailoring sensing properties of smart cementitious composites based on excluded volume theory and electrostatic self-assembly

The excluded volume effect is the reduction in free volume of a matrix filled by secondary fillers, which can enhance the conductive network of carbon nanotubes (CNTs) composites and work effectively with microscale secondary fillers. Besides, the electrostatic self-assembly method has been proved effective for dispersing CNTs. Therefore, this study aims to assemble microscale TiO2 with CNTs to develop smart cementitious composites, in an effort to tailor the sensing properties based on the excluded volume theory and electrostatic self-assembly method. The results show the composites with CNT/TiO2 have a high sensitivity, a wide stress/strain monitoring range, and acceptable mechanical properties. In elastic state, the strain sensitivity of cementitious composites can reach 317. The composite can monitor the compressive stress from 0 to 80.7 MPa, with the maximum fractional change in resistivity as high as 84.09%. Furthermore, due to its low water absorption property, the CNT/TiO2 filler exhibits little negative effect on the mechanical properties of cementitious materials with best piezoelectric performance. (C) 2020 Elsevier Ltd. All rights reserved.