Asphalt mixture with nucleus-shell structural microwave enhanced aggregate: Structure design, preparation and performance

Abstract

The natural aggregates in asphalt mixture with poor electromagnetic loss have poorer microwave absorption capacity and lower microwave energy utilization. The nucleus-shell structural microwave enhanced aggregate (NSSA) consisting with external microwave absorbing and heat collecting structure layer (ESL) and internal limestone was designed to enhance the microwave absorption capacity. The composition and thickness of the ESL were determined. The microwave heating efficiency, microwave energy utilization rate and water stability of asphalt mixture with NSSA and the influence of NSSA on the distribution of electromagnetic field intensity were studied by laboratory test and numerical simulation. The electromagnetic parameters test results show that the ESL had better impedance matching with air when the SiC: Fe3O4: cement: water = 1:2:15:6.3. The ESL thickness should not exceed 4.68 mm considering the penetration ability of 2.45 GHz electromagnetic wave. The microwave heating test results show that the heating rate and energy utilization rate of NSSA were 1.76 times and 5.93 times higher than those of limestone. Furthermore, the asphalt mixture with NSSA had higher heating rate, temperature uniformity and energy utilization rate. The overall water stability of asphalt mixture with NSSA remained the same or even better because the ESL wrapped the pores inside the limestone. The simulation results show that the asphalt mixture with NSSA had larger electromagnetic field intensity and better uniformity of electromagnetic field distribution during microwave heating. In conclusion, the NSSA and the asphalt mixture with NSSA has better microwave absorption capacity and microwave energy utilization rate.