Research on the resistivity attenuation law of cementitious conductive composites induced by stress relaxation

摘要

The present study investigates the piezoresistive effect of conductive concrete. It was found that even under a stress relaxation condition, the macroscopic strain do not change and material resistivity continues to fall, and this phenomenon could not be explained by the traditional tunneling effect. Based on this, the present study created chopped fiber composite cement materials in various mixing proportions. Compared with the mechanical and conductor properties, the volume fraction of 1% chopped carbon fiber composite cementitious material was selected to serve as the object of study, and the basic law of material resistance reduction in the process of stress relaxation was investigated in detail. The results indicate that the relationship between stress and resistivity attenuation approximately obeys the linear correlation in stress relaxation stage. In accordance with the standard linear solid model of viscoelasticity, the law of resistivity relaxation that obeys exponential decay was reached. The present study points out that for the mechanism of resistivity relaxation, the material damage that forms during the loading stage appears to be the phenomenon of damage healing caused by the stress attenuation during the stress relaxation stage, thereby making the fractional damaged conduction path restore its conductivity, and decrease its resistivity. (C) 2019 Elsevier Ltd. All rights reserved.