The two major problems that have plagued urban underground roads since their introduction are the harmful emissions caused by hot mix paving and vehicle exhaust accumulation during operation. In order to solve these two problems at the same time, a new asphalt mixture degrading automobile exhaust, which has the advantage of cold mix and cold-application, was presented and studied. A considerable amount of research shows that the use of titanium dioxide (TiO2) for pavements has received considerable attention in recent years to improve air quality near large metropolitan areas. However, the proper method of applying TiO2 to asphalt pavements is still unclear. The new mixture presented in this article contains epoxy emulsified asphalt as the binder; therefore, how to apply TiO2 in the special asphalt mixture proves to be the main focus. By experimental design, four influence factors on the photocatalytic effect, which are the nano-TiO2 particle sizes, dosage, degradation time, and light intensity, have been investigated. The experimental results showed that the 5-nm particle size of TiO2 is better than 10–15 nm for exhaust gas degradation, especially for HC and NO; with an increase in the amount of photocatalytic material, the degradation of CO and CO2 in the exhaust gas did not increase obviously, while the degradation effects of HC and NO were remarkable; in the 4-h time extended degradation test, the experimental data show that the extended time has little effect on the degradation rate of CO2 and CO, and the general trend is that the degradation of exhaust became significant with the extension of time; while setting a 2-h NO degradation rate as an indicator, to make the index more than 50% or 25%, the average illumination of the road surface cannot be less than 60 lx or 40 lx.
Preparation Technique and Properties of Nano-TiO2 Photocatalytic Coatings for Asphalt Pavement