Abstract

Encapsulated healing agents may delay the growth of reflective cracking in asphalt mixtures and contribute to delay the maintenance of asphalt surfaces. When crack damage appears in the asphalt, the capsules membrane ruptures, and the healing agents are released in the vicinity of the cracks. This experimental research shows the rate at which the oil is released from the capsules when the asphalt is exposed to cyclic loading and its capacity to improve the natural crack self-healing capacities of the asphalt. Using a combination of mechanical and chemical testing, it was found that most of the capsules resist asphalt mixing and compaction. It was found that in porous asphalt, the oil is released gradually during the lifetime of the asphalt, while in dense asphalt, the oil is released at the time when cracks start appearing. This is an indication that the gradation of asphalt is a critical parameter to design the strength of capsules for asphalt self-healing. Furthermore, the self-healing efficiency of capsules is higher in porous and stone mastic asphalt than in dense asphalt mixture. Finally, it has been found that there is a moment in the lifetime of an asphalt road when the capsules are most effective to self-heal the existing crack damage.