Effect of carbon fillers on electrical and road properties of conductive asphalt materials

The electrical and road properties of asphalt materials were modified using different conductive materials, such as graphite and carbon fiber. The material property changes were studied using DMA (Dynamic Machine Analysis) testing, wheel track rutting testing, Marshall stability testing, splitting testing, and electrical property characterizing testing. The results showed decreases in the storage modulus and the loss modulus of the asphalt binders at low temperature when the graphite content was less than 30%. The modulus reached maximum values when the graphite content equaled 40%. Additional graphite reduced the storage modulus and loss modulus of the asphalt binders. With increased graphite content, the peak phase angle shifted from low to high temperature, which showed an increase in the glass transition temperature. The glass transition temperature can be used in the evaluation of the low temperature properties of the asphalt binder and the asphalt mixture. With the addition of 40% graphite and 0.3% carbon fiber by weight to the asphalt mixture, the resistance of the asphalt mixture decreased from ∞ to 835 Ω, the Marshall stability increased by 4%, the split strength increased by 18%, and the dynamic stability increased by 78%. However, excessive carbon fiber or too little carbon fiber did not increase pavement strength. In the indirect tensile testing, the evolution processes of the resistivity of the composites were found to have four periods: a reversible sensing period, a balance period, a steadily increasing period, and a sharply increasing period. The four periods correspond to different interior structures of the material, which show that damage and crack self-monitoring is feasible in conductive asphalt mixture.