Electrical resistance change in compact tension specimens of carbon fiber cement composites

The incorporation of a small volume of carbon fibers into a cement matrix can lead to multiple benefits including improvements in durability and tensile strength. In this paper, the smart material property of the composite which is its ability to respond to electrical stimuli was exploited. It was found that electrical resistance techniques which had previously been only applicable as investigative tools in fracture mechanics studies of metals could now be extended to the field of carbon fiber-reinforced concrete fracture mechanics. Compact-tension specimens of carbon fiber-reinforced mortar with volume percentages between 0% and 0.6% were tested. Fixed frequency electrical resistance measurements of 20 Hz, 100 Hz, 10 kHz and 1 MHz were taken during the tests. Good correlations between the electrical resistance behavior and mechanical behavior were observed. In particular, the electrical resistance may be used to provide some insight on the development and the mechanisms of the fracture process zone, and to provide an estimate of the length of a propagating crack. In addition, the tensile strength of the carbon fiber-reinforced mortar with 0.6% by volume of fibers increased by approximately three times over that of the unreinforced matrix.