A study of the efficiency of photocatalytic asphalts in reducing NOx pollution: from laboratory to semi-real scale

This study evaluates the efficiency of three photocatalytic materials for urban pavements on a semi-real scale. The realistic approach allows the material to be assessed against vehicle loads and runs over the service lifetime of the pavement, giving an idea of its durability of the performance under traffic passage. In practice, a series of functional and durability tests were carried out both in the laboratory and through an Accelerated Pavement Testing (APT) facility. On the one hand, the laboratory work made it possible to evaluate the photocatalytic efficiency (according to RhB degradation and ISO 22197-1) as a function of the incorporation mode of the material. On the other hand, the APT measurements allowed the efficiency and durability of the photocatalytic material to be monitored over the equivalent of up to 20 years of heavy-duty traffic. The material does not impact significantly the skid resistance of the pavement and does not compromise road safety. The data demonstrated that the most efficient photocatalytic material is the one sprayed on the pavement surface, with an average NOx removal of 18 ± 4%, but the efficiency would degrade due to the passage of heavy-duty vehicles in the first quarter of its life.