Environmental and mechanical effects of rubberised open-graded asphalt mixtures incorporating with titanium dioxide: a laboratory investigation

To reduce the impact of automobile exhaust on the urban environment and residents' health, the rubberised open-graded (ROG) asphalt mixtures incorporating with TiO2 particles were developed in the present study. Five types of ROG asphalt mixtures were designed with varying Titanium dioxide (TiO2) content (0.2%, 0.3%, 0.4% and 0.5%, respectively). A comprehensive investigation of pavement performance was carried out for the potential evaluation of the designed mixtures, including the volumetric properties, Marshall stability, rutting resistance, moisture sensitivity and cracking resistance. The tail gas absorption test was to be carried out as well using the self-developed experimental equipment and evaluating method. The testing results showed that the designed mixtures can meet the requirements of the open-graded (OG) asphalt mixture in China's current specifications. The usage of TiO2 in the ROG asphalt mixture showed significant absorption effects on the three types of gases (CO, HC and NO). The increase of catalytic times will significantly reduce the catalytic degradation efficiency, thus affecting the durability of automobile exhaust degradation. Based on the consideration of the environmental and mechanical effects, the optimised TiO2 content incorporated into the ROG asphalt mixture was determined as 0.4%.