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

Abstract

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 concrete mixes, the cyclic fracture-healing tests were conducted on IDT and SCB specimens. Individual and combined effects of mechanical damage, fracture temperature, notch length, moisture, and freeze-thaw cycles on microwave healing performance of asphalt concrete mixes were investigated. Results showed that moisture and freeze-thaw damages have adverse effects on microwave healing performance of asphalt concrete mixes. Increased critical factors caused further detrimental effects on microwave healing performance of mixes.