Single and multiple healing of porous and dense asphalt concrete

When the temperature of asphalt concrete is above a certain threshold, bitumen may start flowing through any possible crack and healing it. Induction heating is a technique for increasing the temperature of asphalt mixture. It consists of adding electrically conductive and magnetically susceptible particles to the mixture. These particles can be heated thanks to the action of an induction heating apparatus. The objective of this article is to investigate the effect of different asphalt mixture porosities and different types of bitumen on the induction-healing rates of asphalt concrete. With this purpose, semi-circular test samples made of porous asphalt mixture, with bitumen pen 70/100, and dense asphalt mixture, with bitumen pen 40/50, both of them containing steel wool fibres, have been analysed through successive three-point bending and induction heating tests. It has been found that the minimum temperature above which healing of asphalt mixture starts depends on the capacity for flow of bitumen at the threshold temperature. Moreover, the maximum healing level reached by asphalt mixture after damage is related to the type of bitumen used. Finally, it has also been found that successive heating of asphalt mixture may damage the structure of the material, reducing its healing capacity.