Assessment of self-sensing capability of Carbon Black Engineered Cementitious Composites

The protection and health monitoring of degraded concrete infrastructure required a multifunctional material which possessing good damage tolerance, whilst providing a self-sensing capacity that designed to specifically diagnose cracking. Engineered Cementitious Composites (ECC) presents superb tensile ductility and pseudo strain-hardening property. In this paper, a type of multifunctional ECC incorporating Carbon Black (CB) nano-particles and Air Entraining Agent (AEA) to decrease the bulk resistivity while increasing the tensile strain capacity is studied. The effect of CB particles on the electrical response of ECC, HFA-ECC (high fly ash ECC) and CB-ECC under direct tension was investigated experimentally by four-point probe test. The experimental results showed that the bulk resistivity of all specimens increased with the crack propagation, and the increase ratio in inelastic phase was much higher than that in elastic phase. The Gauge Factor (GF) in the strain-hardening stage was calculated by using the change in bulk resistivity and tensile strain, and the relationship between GF and crack width was also investigated. The combination of CB and AEA obtained the highest sensing ability from elastic stage to first cracking stage, which can determine whether the internal microcracks are generated by the change of the bulk resistivity.