Laboratory Evaluation of Self-Healing Index in Asphalt Mixtures

In this research, in order to construct environmentally friendly green asphalt mixtures, steel slag with a size of 9.5-4.75 mm to a volume ratio of 60% of aggregates and red mud waste with 50 and 100% ratios of filler has been used as an alternative to limestone filler, and self-healing index and moisture sensitivity of these mixtures have been evaluated. To do that, the semi-circular bending test (SCB) was performed by seven damage-healing cycles using the microwave irradiation heating method. Results indicated that the steel slag and 50% red mud waste in the first healing cycle increased the optimum healing ratio compared to the control sample, respectively; 53.01% and 32.35%. Also, the moisture susceptibility test results showed that the amount of moisture resistance in mixtures containing steel slag and 50% red mud decreased by 16% and 21%, respectively, compared to the control sample. Using 50% and 100% carbonation cake as a replacement for limestone filler in mixtures containing steel slag has increased the moisture resistance by 9% and 13%, respectively. Also, this weakness of moisture resistance in the sample containing 50% of red mud was compensated by using 50% of carbonation cake, and moisture resistance was increased by 12%. According to the obtained results, the use of these waste materials instead of non-renewable natural resources such as aggregates, in addition to preserve the non-renewable natural resources, will improve the healing performance of asphalt mixtures.