United States Department of Transportation
i
Laboratory and field studies of photocatalytic NOx and O3 removal by coatings on concrete.
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2017-03-01
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[PDF-11.31 MB]
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Abstract:This project involved thorough testing of titanium dioxide (TiO2)-containing commercial photocatalytic coatings
applied to portland cement concrete for highway applications, focusing on the use of these coatings as an
abatement method for atmospheric nitrogen oxide (NOx) and ozone (O3). The study consisted of four parts:
laboratory chamber testing; outdoor exposure studies; modeling; and field application. Full-factorial experiments
in laboratory chambers designed to examine the impact of variables such as temperature, relative humidity, time,
and pollutant concentrations on NOx and O3 removal by the coatings demonstrated that a commercial stucco was
the best performer of the four original materials tested. After one and two years of outdoor, roadside exposure,
the NOx removal capacity of the stucco decreased significantly, but could be improved by soap and water
washing. A Comprehensive Air Quality Model with extensions (CAMx) for the Houston-Galveston-Brazoria and
Dallas-Fort Worth areas showed the potential of the stucco to reduce average ozone concentrations if large areas
of highway structures are coated. Testing at a field site in north Austin, however, showed no conclusive
difference between air quality in areas with coated and uncoated highway barriers. Therefore, while
photocatalytic concrete coatings have promise for improving air quality, the data from this project suggest that
such improvements may not be significant enough to be measured experimentally in common roadway
configurations such as the site tested for this study.
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