A review on photocatalytic asphalt pavement designed for degradation of vehicle exhausts

This paper presents a comprehensive review on the most recent level of knowledge and developments achieved in utilizing photocatalytic asphalt pavement as a method to reduce vehicle pollutants. It included the mechanism of photocatalysis, available testing facilities, quantifying methods, widely studied techniques of applying TiO2 particles onto asphalt pavements, influencing factors on pollutants degradation and future perspectives. Nano-TiO2 crystal types, doping approach, ambient temperature, relative humidity, intensity and time of irradiation, and pollutant characteristics are the key factors that influence the efficiency and durability of photocatalytic asphalt pavement. The photocatalytic asphalt pavement can achieve a degradation efficiency of 55% for NOx pollutants and 20% for SO2 pollutants at this moment, while suffering from short service life due to busy traffics and complex weather circumstances. In the future perspectives of photocatalytic asphalt pavement, practical costs, applying methods, durability, and negative effects are highly emphasized for the development of sustainable and durable photocatalytic roads.