Crack detection of a HPCFRCC thin plate using electrical resistivity method

Abstract

Electrical resistivity measurement has been used as a test for studying the durability-related properties of cement composites for decades. Applications of electrical resistivity measurement namely health monitoring and crack detection are of great importance for increasing the service life of structures. The former is the capability of cement composite to sense its own strain (piezoresistivity) and the latter is based on the irreversible change of resistivity in the presence of crack. In this study, at first the effect of different fractions of silica fume and carbon fiber on piezoresistivity of cement composites were evaluated by monitoring the variations of resistivity under compression. Secondly, a high performance carbon fiber-reinforced cement composite (HPCFRCC) thin plate specimen was subjected to four-point bending while the variations of resistivity were recorded so that the zone at which the initiation of crack occurs can be detected. Results showed that both compressive strength and water absorption are highly affected by silica fume content while flexural strength slightly changed by increasing silica fume. While the addition of carbon fiber increased water absorption, it marginally affected mechanical strengths. Piezoresistivity test showed the ability of carbon fiber as a functional filler and the facilitated dispersion of fibers in high concentration of silica fume particles. It was confirmed that when carbon fiber content increases to more than 0.4 volumetric percentage, conductivity of specimen substantially increases and required sensitivity from piezoresistivity test is obtained. Crack detection test showed that when cracks are formed the planar surface resistivity of thin plate significantly changes. Thus, the formation and propagation of cracks can be monitored using electrical resistivity measurement in self-sensing cement composites.