Electrical Resistivity, Pulse Velocity, and Compressive Properties of Carbon Fiber-Reinforced Cement Mortar

The electrical resistivity and mechanical properties of carbon fiber-reinforced cement mortar (CFRCM) were investigated. Both cylindrical and prism specimens were used in this investigation to determine the effects of size and shape of specimen on the physical and mechanical properties of the CFRCM systems. Carbon fiber loading was varied up to 6% (w/w), and water-to-cement ratios (w/c) of 0.5 and 1 were used. The specific electrical resistivity of the plain mortar with w/c ratio of 1 (>66,000 Ohm m) was reduced to 3,750 and 0.23 Ohm m upon increasing the carbon fiber content to 1 and 6% (w/w), respectively. The percolation theory was used to represent the variation of the electrical specific resistivity with fiber content in the cement mortar. Increasing the w/c ratio decreased the strength and toughness of the CFRCM composites. Increasing the fiber content increased the peak strain and toughness, but decreased the Young's modulus and electrical resistivity of cement mortar composites. Pulse velocity tests showed that the specimen shape also affected the dynamic Young's modulus, dynamic shear modulus, and the dynamic Poisson's ratio. The compression strength of the CFRCM was influenced by the w/c ratio and the fiber content. A model was used to predict the compressive stress-strain behavior of different CFRCM systems, and relations between static and dynamic properties have been developed. Empirical relations were developed to relate the specific electrical resistivity to unit weight, Young's modulus, and pulse velocity.