Durability quantification of TiO₂ surface coating on concrete and asphalt pavements

The use of nanosized titanium dioxide in photocatalytic pavements is a promising approach to combat air pollution. Past research focused on the effects of environmental and operational parameters on photocatalytic efficiency and its performance under laboratory and field conditions. Few studies have attempted to quantify the durability of the technology integrated with in-service photocatalytic pavements. This study developed and tested a new photocatalytic quantification method used to quantify the short-term durability of a TiO2 spray application on two pavement surfaces: concrete and asphalt. This was accomplished through developing a nitrate extraction method that could be used on in-service pavements without requiring core extraction. Results of the proposed method were compared to results obtained from the Japanese Industrial Standards (JIS) method. The experimental program included testing photocatalytic samples in the laboratory for NOx reduction and nitrate accumulation based on the JIS method. Results were compared to the nitrate measurements using the proposed method, and a correlation factor was developed. The developed method was then used to quantify the durability of a TiO2-treated photocatalytic pavement over a 5-month monitoring period under field conditions. Results suggest that the service life of TiO2 coating in concrete is between 6 and 11 months and between 10 and 16 months in asphalt pavements.