Evaluation of Asphalt Mixture Modified with Graphite and Carbon Fibers for Winter Adapt\ation: Thermal Conductivity Improvement

Conventional asphalt concrete is relatively low conductive. This paper focus on the improvement of thermal properties of asphalt mixtures using conductive fillers, and investigating the conduction performance by two-dimensional (2D) simulation. Also, the microstructure of asphalt mixture was analyzed with extremely high magnification to observe the distribution of conductive fillers in the mixture. Indirect tensile (IDT) strength was additionally investigated. Different asphalt mixtures used in this study was modified with milled carbon fiber, chopped carbon fiber, and graphite powder. The study also evaluated the effect of mixed fillers combined carbon fiber with varying admixtures of graphite contents. The thermal properties of modified asphalt mixtures were measured and calculated to evaluate their conduction effects to obtain the appropriate kind and quantity of carbon fibers and graphite. Based on the results of thermal properties of the asphalt mixtures, the 2D simulation was performed on a typical pavement design using the finite element method to comprehend the conduction performance taking place in pavement structure. The IDT test was conducted to compare the IDT strength of asphalt mixture modified with carbon fiber and others. Microstructure analysis was conducted on scanning election microscopy (SEM) images of the fractured surface of specimens. Thermal testing and analysis results indicated that carbon fibers and graphite basically increase the thermal properties of asphalt mixtures. The combination of mixed fillers provided certain advantages over single graphite or carbon fiber filler. The simulation results presented the reasonable and reliable heat conduction correlated with each conductive filler. The IDT test inferred that the tensile strength of asphalt mixture was enhanced with an addition of certain amounts of the chopped carbon fiber. According to microanalysis, graphite particles show the formation of conductive clusters throughout the asphalt mixture, whereas carbon fibers show a long-range connecting effect. (C) 2016 American Society of Civil Engineers.