Investigating the effects of aging and New Jig Coal Tailings (NJCT) on mixed-mode I/II fracture behavior of asphalt mixture modified with BituSul

Abstract

Moisture susceptibility and cracking resistance of asphalt pavement made with sulfur additive are two important failures of this type of asphalt mixture that should be considered. Recently, researchers have been trying to improve the mechanical performance of sulfur asphalt mixtures by modifying the asphalt mixture manufacturing method, modifying sulfur manufacturing technology, and applying laboratory conditioning. In this laboratory work, an attempt was made to improve the mechanical properties of an asphalt mixture made with a type of sulfur material called BituSul by different methods. The first method was the moisture susceptibility test and the second method was the fracture test. In the first step, 30 % of PG70-10 bitumen was replaced with BituSul, and a moisture susceptibility test was performed. After estimating the minimum moisture susceptibility of the BituSul-reinforced asphalt mixture, the fracture test was performed on the asphalt mixture without additives, BituSul-reinforced asphalt mixture, and BituSul-reinforced asphalt mixture containing New Jig Coal Tailings (NJCT) (with a replacement ratio of 50 % filler). To compare the fracture behavior of the mixtures over time, two conditions, including one freeze–thaw cycle (FTC) and about fifty-six hours of the aging period, which was equivalent to four years of failure, were applied to the mentioned samples separately. Finally, the samples were tested under mixed mode I/II at −12 °C and + 24 °C. The findings showed that the manufacturing technology used in this research, including how to design and manufacture the samples, the type of bitumen used, and the type of sulfur used (BituSul), caused a 2 % decrease in moisture susceptibility compared to the base sample. The fracture resistance results showed that the application of 0 and one cycle of FTC decreased the fracture indices of the mixture reinforced with BituSul at −12 °C and + 24 °C. Also, the results showed that the fracture stiffness improved for samples containing BituSul at −12 °C and + 24 °C. Finally, the results showed that applying aging to BituSul mixtures and BituSul mixtures reinforced with NJCT improved fracture resistance, fracture flexibility, and fracture stiffness. However, NJCT could not compensate for the improvement of fracture indices of asphalt mixture caused by the presence of BituSul; therefore, the application of aging was reported to be a suitable option to improve the fracture indices of BituSul-reinforced mixtures.