Electrical conductivity of asphalt mortar containing conductive fibers and fillers

The objective of this research is to examine the conductivity of asphalt mortar through the addition of electrically conductive fillers and fibers: graphite and steel wool, and prove that this material can be heated with induction energy. The effect of fibers content, sand-bitumen ratio and the combination of fillers and fibers on the resistivity of asphalt mortar was investigated. It was found that the percolation threshold happened sooner by adding electrically conductive fibers than by adding fillers. Percolation threshold was also found to be function of the sand-bitumen ratio and of the volume of fibers content. There is an optimum content of fibers for each sand-bitumen ratio, above which it is difficult to make the mixture and the electrical resistivity increases exponentially. Besides, in case of adding conductive fillers or a mixture of conductive fibers and fillers to the mastic, once the maximum conductivity is reached, it remains constant, independently of the volume of conductive filler added. Nano CT-scan (computed axial tomography) reconstructions were also used to visualize the fibers connected inside the mixture. Finally, to validate the research, three different samples were induction heated and their temperature variation was measured. (C) 2009 Elsevier Ltd. All rights reserved.