Improving microwave heating efficiency of asphalt concrete by increasing surface magnetic loss of aggregates

Abstract

To improve microwave heating efficiency of asphalt pavement, a new technique was proposed by coating a very thin layer of magnetic Fe₃O₄ films on coarse and fine aggregates, using chemical co-precipitation reaction. The microwave healing effects of modified asphalt mixtures were tested via three-point bending fatigue test and flexural failure test. The results showed that the surface temperatures rates of the asphalt concrete specimens with both modified coarse aggregates (Type C) and modified fine aggregates (Type F) were 0.72°C/s after microwave heating for 2 min, which were 45.8% higher than those of the ordinary asphalt concrete (Type O). The microwave healing indexes of Type C and Type F were 87% and 84%, respectively, about four times as much as those under room temperature. The flexural strength recovery rates of Type C and Type F recovered to 75% in the first damage–heal cycle but decreased to 60% in the second cycle. In addition, the pavement performances of the modified specimens have not been reduced by the surface modification method. In view of the significant improvement of the microwave healing efficiency of asphalt mixtures, this suggested preparation principle is expected to be widely used in the repair and reconstruction of asphalt pavement.

Keywords:

• Surface modified aggregates
• Fe₃O₄ coating
• microwave heating
• healing index
• flexural strength recovery rate