Effect mechanism of mixing on improving conductivity of asphalt solar collector

This paper investigates the influence of different mixing parameters of 1 forced mixing on the conductivity of asphalt solar collector (ASC). Graphite powder and carbon fibers were used to improve the conductivity of asphalt concrete. The conductivity of ASC was measured with the same mix gradation, mixing procedure but different mixing parameters. The rational vibrating mixing parameters are obtained according to orthogonal experiments of the conductivity. A laboratory test of volume index and conductivity was performed after determining the rational mixing parameters. The effects of common forced mixing the on microstructure of ASC were investigated using scanning electron microscopy (SEM) and computed tomography (CT). The results obtained show that the mixing parameters have a major impact on the conductivity of asphalt concrete, among which the temperature have the strongest influence, while the revolutionary speed has less influence. The rational mixing parameters include: Bitumen temperature T1 160 °C, aggregate temperature T2 180 °C, mixing time t 90 s and mixing revolution speed v 45 r/min. ASC can obtain good conductivity and volume index with rational mixing parameters. The resistivity drops from insulation to 39.8 ohm m and the thermal conductivity increases from 1.531 W/m K to 2.120 W/m K. The microstructure of ASC showed that the conductive fillers have uniform distributions in the sample. Conductive particles and carbon fibers promote the formation of conductive networks, because fibers may bridge up several isolated conductive particles.