About the research
This research effort evaluated the environmental impacts and benefits obtained from concrete paving materials blended with photo-chemically-active titanium dioxide (TiO2). The project was completed in combination with a full-scale Missouri Department of Transportation (MoDOT) two-lift paving demonstration project in the St. Louis, Missouri urban area. Two innovative photo-catalytic concrete paving materials have been studied during this project, including: a) a photocatalytic concrete mainline pavement and b) a photocatalytic pervious concrete shoulder pavement. The mainline pavement material was applied using a two-lift paving strategy, where the lower, base-level layer was constructed with less expensive materials (e.g., a low cementitious-content base lift), and the thinner top wearing course was then overlaid immediately with concrete containing photocatalytically active cement. The included photocatalytic concrete paving material is marketed under the trade-name TX Active. The second shoulder pavement element involved a similar, photocatalytic concrete material also containing the titanium dioxide additive, although in this instance the TiO2 was blended into a pervious (rather than conventional) concrete for the roadside shoulder pavement material. Together, this set of innovative mainline and shoulder paving materials, including both a two-lift photocatalytic mainline pavement and a photocatalytic pervious shoulder pavement, is believed to represent one of the most technically advanced and environmentally-friendly concrete pavement systems ever employed in the US. Field-scale assessment of this innovative highway involved both passive and active air quality NO and NO2 testing, respectively using integrative Ogawa samplers and a 2B Technologies ozone titration analyzer. This field-scale assessment also involves water-quality testing of mainline and shoulder pavement runoff.