Photocatalytic pavements

Abstract

Pavements which have been blended, coated, sprayed, etc., with photocatalytic TiO2 additives have attracted world-wide interest during the past decade-plus period based on their environmentally beneficial abilities to provide reactive (i.e., ‘smog-eating pavement’ plus ‘self-cleaning’) and reflective (i.e., ‘cool pavement’) impacts. The former ‘reactive’ capabilities notably involve a de-polluting property where TiO2 irradiation with UV-A spectrum light is able to oxidatively convert a variety of problematic organic and inorganic pollutants within both atmospheric and aqueous runoff zones. This suite of transportation-generated amenable contaminants notably includes NOX residuals which otherwise represent a serious environmental and human-health challenge within high traffic density, inner-urban highway locations with high-density adjacent resident populations. Multiple laboratory-level photo-reactor studies published over the past several decades have demonstrated this photocatalytic NOX-removal capability, while at the same time scientifically exploring and elucidating key relationships between NOX abatement and various environmental factors (e.g., light wavelength and intensity, ambient relative humidity and surface moisture, pavement temperature, surface soiling impacts, etc.). Field monitoring, albeit in more limited fashion, has provided similarly supportive findings at a number of locations involving not only TiO2-bearing pavements but also locations paved with blocks, pavers, bricks, etc. which have been sprayed or coated with TiO2-enriched admixtures. This chapter, therefore, provides an overview of the related literature covering academic, industrial, patent, and related perspectives and both experimental and full-scale findings. While this existing body of knowledge is substantial, complementary.