Effect of moisture and freeze-thaw damage on microwave healing of asphalt mixes

Case I: (a) In mild climate condition, traffic loading causes initiation and propagation of micro-cracks in asphalt concrete. (b) These distresses can be partially healed under the microwave heating imposed by external electromagnetic radiation that is referred to as microwave healing. Case II: (c) In extreme climate condition (e.g., rainy, snowy and cold), moisture and freeze-thaw damages cause asphalt binder to become stiff, loss of adhesion between asphalt binder and aggregate particles and loss of cohesion within asphalt binder. The combination of these factors with traffic loading results in extended micro-cracks and damages in asphalt concrete. (d) These damages can be partially healed through microwave heating/healing process with less efficiency, in comparison with Case I. [Display omitted] •The effects of moisture and freeze-thaw damages on microwave heating/healing process were examined.•Cyclic fracture-healing scenario was conducted to impose mechanical damage.•The concurrent effects of mechanical, moisture and freeze-thaw damages were investigated.•The moisture and freeze-thaw damages decreased microwave healing efficiency.•The freeze-thaw damages have shown the highest adverse effects on microwave healing process. Microwave heating/healing is a kind of maintenance technique to repair micro-cracks in asphalt mixes. This method was conducted mostly on unaged materials, and the effects of moisture and freeze-thaw damages have not completely been studied. The fluidity of the asphalt binder, accomplished by heating, increases the ability of binder to fill micro-cracks and heal the asphalt mixes. Moisture and freeze-thaw damage increase the modulus of asphalt binder resulting decrease of fluidity of material. In contrast, moisture and freeze-thaw damages could reduce the ability of mixes to heal. In this research, mixes were prepared using neat and activated carbon modified asphalt binders. In order to assess the microwave heating properties, mixes were subjected to different levels of moisture and freeze-thaw conditions. The microwave heating performance was investigated under electromagnetic radiation. It was found that activated carbon is a proper binder-based additive that increases electromagnetic absorption of asphalt mixes. Indirect Tensile (IDT) and Semi-Circular Bending (SCB) specimens were fabricated, and different levels of moisture and freeze-thaw cycles were applied. For quantification of microwave healing capability of damaged asphalt