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.

Traffic noise is the perpetual form of environmental pollution adversely affecting human health in urban environments. This literature review, intended for pavement researchers and professionals, looks at the continuously evolving low-noise asphalt pavement technologies and the techniques which can be used to evaluate them. Test methods for determining the acoustical properties of asphalt pavements are reviewed, in both the laboratory and field environments. The Close-Proximity (CPX) method is the most commonly used field test for pavement acoustics, followed by the Statistical Pass-By (SPB) and On-Board Sound Intensity (OBSI) methods. SPB seems is the most comprehensive methods, while the CPX is more practical. Methods for measuring the acoustical properties in the laboratory include the impedance tube for sound absorption and laboratory pavement noise simulators; with only the larger drum methods being able to produce conditions similar to in-situ. Methods for noise-relevant non-acoustical characteristics like surface texture, porosity and airflow resistivity were also reviewed. Optimizing surface texture at the macro-scale was found to be important in reducing tire/road noise. For pavement types, porous asphalt concrete (PAC) and its variants result in low-noise properties the most reliably, while having some drawbacks in durability and maintenance. Finally, various acoustical performance prediction models were discussed.

This paper summarizes the main results of experimental research on the induction healing of dense asphalt concrete with steel wool fibers. Different physical properties of dense asphalt concrete, as the steel wool fibers distribution, mechanical properties, thermal conductivity, and healing via induction heating have been analysed. The main results show that short and thick fibers disperse very well in the mixture, while long and thin fibers produce clusters. It was also observed that fibers can be damaged during the mixing and compaction processes. In addition, it was found that steel wool fibers do not significantly improve the mechanical properties and damage resistance of dense asphalt concrete. Moreover, steel wool fibers slightly increase the thermal conductivity of dense asphalt concrete. Furthermore, the temperature reached due to induction heating increases with the number of fibers in the mixture and with their diameter. Finally, it was found that dense asphalt concrete heals through the increase of temperature and that the type and diameter of fibers do not influence the healing properties of dense asphalt concrete.