Feasibility of Concurrent Improvement of Pollutants-Absorption Ability from Surface Runoff and Mechanical Performance of Asphalt Mixtures by Using Photocatalytic Nanomodified Porous Asphalt

Abstract

There has been an ever-climbing trend toward environmental concerns in addition to road technical issues, resulting in the testing of new high-quality pavements. First, due to the presence of acidic contaminants in surface runoffs in developed areas rooted in acid rainfall, researchers have discovered that these polluted runoffs can pollute groundwater reserves and are harmful to humans. Second, the porous asphalt (PA) mixtures as a hot mix pavement with an empty space structure have significant performance limitations such as low strength and durability because of their large amount of air voids. Therefore, a novel high-quality and photocatalyst PA pavement with the ability to absorb contaminants from acidic water was introduced at the lab scale in this study. For this aim, PA mixes modified with photocatalytic nanoparticles such as nano zinc oxide (ZnO) and nanosilica (SiO2) were fabricated. The sol-gel method was used to manufacture photocatalytic based on ZnO/SiO2 (ZS) in this research. The aforementioned compound reacts with UV light and oxidizes pollutant particles, including nitrogen oxides (NOx) and sulfur oxides (SOx). This novel PA mix was tested by environmental tests (pollutants absorption) and mechanical performance tests (dynamic creep, resilient modulus, moisture susceptibility, and fatigue life). The results demonstrated that adding the photocatalytic nano-ZS to the bitumen effectively removed acidic contaminants such as NO3 and SO4 from the water by an average of 48% in 24 hours. Besides, results showed that the addition of nano-ZS increased the moisture susceptibility and stiffness of PA mixtures by an average of 45% and caused a dramatic improvement in the rutting resistance of mixes. Moreover, nano-ZS-modified PA mixes had longer fatigue lives than conventional ones. It should be noted that the optimum amount of nano-ZS in PA mixes in this study was 7%.