Document Type

Conference Presentation

Publication Date





approximation theory, pavements, nitric oxide, elimination, roads


This paper examines an approximation method to qualitatively assess the air-cleaning performance (i.e., specifically the elimination of aerial nitrogen oxide, NO, released within vehicular exhaust) by full-scale pavements which contain photo-catalytically reactive titanium dioxide under optimal conditions. Two hypothetical road configurations were considered using this method, including both a two-lane, low traffic density (i.e., 4,000 full-day AADT) and a four-lane, moderate traffic density (i.e., 10,000 full-day AADT) design. These options were then comparatively examined on the basis of expected European Union or United States vehicular emission levels. In each case, this method’s day-time-only percentile elimination approximation results were derived using an extrapolation of lab-based specific contaminant elimination rates (i.e., mass NO removed per surface area per time) relative to contaminant release rates which were projected for EU or US vehicular contaminant emission levels. Using this paper’s approximation method, and assuming best-case scenario conditions (i.e., original, un-aged, peak catalytic performance under optimal temperature, relative humidity, etc. conditions), day-timeonly percentile removals in the ~mid-60% to ~90% range were predicted for EU two- and fourlane roadways with low to moderate traffic densities. These EU contaminant elimination approximation percentiles were higher than the actual, observed range (e.g., typically ~mid-10% to ~mid-60% day-time removal percentiles) of published contaminant elimination values which had been measured according to gas-phase contaminant changes during a number of full-scale studies completed at various EU locations and with EU-related vehicle types and emissions. In the case of similar US highway options, this method’s approximated day-time-only elimination percentile results were lower than what was predicted for similar EU road options, with a range of ~30% to ~40%. These latter, lower US road approximations were believed to be related to higher expected US versus EU vehicle emission levels (i.e., by a factor of ~two- to ~three-fold for light and heavy duty vehicles).


This paper was presented by co-author James E. Alleman at the International Concrete Sustainability Conference held in Washington, D.C. on May 16, 2016.

Source Publication Title

Proceedings of the International Concrete Sustainability Conference


National Ready Mixed Concrete Association