VOCs reduction in bitumen binder with optimally designed Ca(OH)2-incorporated zeolite

Abstract

Environment-friendly pavement materials are one of the biggest concerns in infrastructure material design. Bitumen binder is a widely used infrastructure material for highways, but it releases VOCs (volatile organic compounds) during its life time service. VOCs release from bitumen binder will not only lead to environmental pollution, but also result in degradation of pavement performance. This research focused on reducing VOCs in bitumen binder by self-designed Ca(OH)2-incorporated zeolite. Characteristics of Ca(OH)2-incorporated zeolite and its VOC reduction were studied. The research results indicate that decreasing the mole ratio of Al3+/Ca2+ will increase the surface roughness and specific surface area of Ca(OH)2-incorporated zeolite, with potential for higher VOCs reduction. The 1:2 Ca(OH)2-incorporated zeolite mainly contains mesoporous structure. With its water molecules, occluded in cavities and channels, being released during heating, the viscosity of bitumen binder also decreases resulting in a warm mix that positively influences the reduction of VOCs emission further. Adding Ca(OH)2-incorporated zeolite into bitumen can effectively reduce both total emission and toxicity of bitumen VOCs. An optimal heating temperature is needed to obtain peak reduction on VOCs. At warm mix temperature, a remarkable reduction of PAHs release can be achieved due to the Ca(OH)2-incorporated zeolite’s catalytic properties. More than 37% of total VOCs reduction can be achieved by the self-designed Ca(OH)2-incorporated zeolite.