According to concrete paving industry group Britpave, additives in concrete pavement could enable it to reduce elevated levels of traffic exhaust emissions. The addition of titanium oxide (TiO2) in concrete may allow the pavement to absorb nitrogen dioxide emissions from road traffic.
“The addition of [TiO2] to concrete means the concrete actually eats pollutants,” said Joe Quirk, Chair-Britpave. TiO2 is a photocatalytic material that reacts in sunlight to absorb nitrate oxides (NO2) and convert them into harmless nitrates. Quirk has said that this could be applied as a pavement spray or as an additive to concrete to combat pollution, and would add only 5% to 10% to the cost of a concrete road.
Quirke said that research carried out by the Eindhoven University of Technology-Netherlands found NO2 reduction of 35% to 40% in areas paved in concrete featuring TiO2. Researchers at the Public University of Navarre-Spain, are developing a nanoparticle coating for concrete uses photocatalytic reaction to reduce up to 90% of nitrogen oxides, 80% of hydrocarbons, and 75% of carbon monoxides. In Segrete, Italy, a road treated by Essroc Italcementi with a TiO2 pavement spray resulted in a NO2 reduction of 60%.
He added that the use of the technology by Highways England could be a useful solution to come out of its review of measures to reduce elevated levels of traffic exhaust emissions, and is being urged to consider this new concrete technology.
Quirke said, “Pollutant-eating concrete roads may sound like science fiction but they are a very real solution that should be considered. They are not the only environmental benefit of concrete roads. In addition, concrete roads can also be:
• Self-heating to reduce ice and snow-build-up
• Self-healing to reduce the need for repair and maintenance
• Energy conductive for easy wireless charging of electric vehicles as they travel over them, and
result in a reduced life cycle carbon footprint due to:
• Thinner pavements
• Longer performance life
• Reduced maintenance”
Several US states like Florida, Texas, Ohio, and North Carolina also tout smog-eating pavement. According to an Engineering News Record (ENR) Online News article titled “Interest Increases in ‘Smog-Eating’ Pavements”, Airports, highways and civic structures are serving as testbeds for a patented technology that uses titanium dioxide to capture pollutants, particularly nitrogen oxides, in pavements—creating “smog-eating roads”. The concept of photocatalysis with titanium dioxide is receiving increasing attention for its photoreactive effectiveness in degrading greenhouse gases. In 2019, a Texas A&M Transportation Institute (TTI) report found that the Orlando International Airport taxiway pavements sprayed with two titanium dioxide products provided by Pavement Technology Inc. (PTI) reduced nitrogen oxide rates by approximately 50%!
When light-energy activated, the material creates a chemoelectric energy field atop pavement that captures and converts harmful gases emitted through motor exhaust into harmless compounds easily absorbed by surrounding foliage, according to PTI.
Michael Durante, Vice President-Finance and Strategic Planning-PTI said, “In good conditions, we can achieve 60% reduction in those gases. We’re also testing to see if there can be a meaningful reduction of heat islands.”
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Chris McGee, Assistant Director of Transportation-City of Raleigh, North Carolina, pitched the technology to the city in 2019. He stated that if all goes according to plan, the city will test about 425,000 sq ft of pavement, half using PTI’s standard reclamation application, and the other half using the titanium infusion. The company collaborated with Louisiana State University several years ago.
Durante said, “Louisiana Sate University (LSU) was testing titanium dioxide with a water-based solution on streets. It didn’t last very long and it wore off. They asked us to look into [applying titanium dioxide to] the wearing course of roads so that it is more permanent. Cores from a Cincinnati client are currently being analyzed at TTI, and other sites include Charlotte and Cary, North Carolina; Akron, Ohio; and St. Petersburg, Florida. The Ohio Turnpike ‘would be the first toll road in the world to test photocatalytic technology’.”
For the New Civil Engineer online magazine article titled “Concrete additives could ‘eat’ transport-related emissions”, please go to: https://www.newcivilengineer.com/latest/concrete-additives-could-eat-transport-related-emissions-04-08-2020/
For the Construction Enquirer online magazine article titled “Concrete firms push for pollution eating roads”, please go to: https://www.constructionenquirer.com/2020/07/30/concrete-firms-push-for-pollution-eating-roads/
For the ENR Online News article titled “Interest Increases in ‘Smog-Eating’ Pavements”, please go to: https://www.enr.com/articles/49901-interest-increases-in-smog-eating-pavements