Optimum moment to heal cracks in asphalt roads by means electromagnetic induction

Asphalt mixtures, the most commonly used materials to build road surfaces, are made of aggregates, which give structural strength, and bitumen, a viscous liquid that can flow and fill the cracks when these occur. This phenomenon is known as asphalt self-healing and is normally too slow to be used in practice. This paper is about a method to accelerate the self-healing, called induction heating. Metal fibres can be added to the asphalt and, once the road is cracked, heated by applying an alternating electromagnetic field, which melts the asphalt and contributes to repair the cracks. The research has explored experimentally the optimum moment to apply the induction heating. To do that, cyclic loading tests have been used and the extension in the number of cycles quantified. Furthermore, the physical properties of the air voids in the asphalts before and after cyclic loading, and after induction heating have been quantified using Computed Tomography Scans. It has been concluded that there is an optimum moment to apply induction heating, which occurs at approximately 35% of the lifetime of the material. Furthermore, it has been observed that the macroporosity of asphalt and diameter of air voids changes with the tests and the induction heating. (C) 2019 Elsevier Ltd. All rights reserved.