The asphalt binder in a roadbed is continually degraded by environmental forces such as solar ultraviolet rays. In time, the material loses its adhesive ability to keep the surface particles intact. The roadbed eventually deteriorates as moisture permeates the surface, resulting in roughness, potholes, and later structural failure. Typical sealants and rejuvenators can extend the life of a roadbed, but they only operate at the surface and cannot prevent deep decay.
Asphalt exhibits self-healing properties at a high temperature, but only if it is left undisturbed. Researchers at the Delft University of Technology investigated the ability to heat asphalt internally with induction energy to increase its healing rate. The first prerequisite of induction heating is that the heated material must be conductive, which the scientists accomplished by adding electrically conductive fillers and fibers to the bitumen. The second prerequisite is that these fillers and fibers connect in closed-loop circuits. When a microcrack appears in the asphalt, conductive materials form closed-loop circuits around the microcrack. A coil induces eddy currents in the closed-loop circuits, which generate heat and melt the bitumen, thus closing the crack.
Contact: Delft University of Technology Civil Engineering and Geosciences, Delft, The Netherlands.
For more information, see Transmaterial Next: A Catalog of Materials that Redefine Our Future