Tag Archives: Titanium dioxide

Spray-on treatment could keep roads strong for longer while also making cities cooler

Is the heat getting you down? Most people can empathize. Enough of them, in fact, that one company is piloting a new asphalt treatment meant to reduce temperatures and eliminate pollutant particles, all while helping to keep roadways in good condition.

Image credits Maxx Girr.

The compound’s exact makeup is, as you’d expect, still a company secret. But we do know that it is based on titanium dioxide and meant to be sprayed over asphalt surfaces in cities struggling with the urban heat island effect. Although it does help reduce overall temperatures by making built surfaces absorb less heat, the treatment — named A.R.A.-1 TI — is marketed as a “road rejuvenator” and a seal for roadways.

Spray the heat away

The company behind this treatment, Pavement Technology Inc., is collaborating with Texas A&M University to measure its efficiency. This process involves sending road cores (samples retrieved from treated roadways) and air quality measurements to the university’s labs in order to determine what effect the treatment has in real-life situations.

But if the theory translates to practice, it should definitely help cool cities down. The source of the urban heat island effect is sunlight, which carries energy in the form of heat to asphalt and concrete surfaces, such as roads and buildings. These are very good at heating up, which makes everything that much more unbearable during the day (because you’re now standing, on a hot day, in a mile-wide hot surface). At night, these surfaces cede heat back into the environment, keeping the night’s air from cooling down. The more buildings there are in the city, the taller they are, and the more densely-packed, the more heat will be captured, and cities can be between 1 to 7 degrees F (0.6 to 3.4 degrees C) warmer than the areas around them.

All in all, a terrible experience for everyone involved.

Titanium dioxide is more commonly known as titanium white. Chances are that most white things you’ve ever encountered in your life, apart from foods, were painted using titanium white as a pigment. The plan is for this substance, which reflects incoming sunlight, to have a cooling effect on the dark surface of asphalt, which absorbs a lot of heat during the day. We’ve seen previously how green spaces can help reduce the intensity of the urban heat island effect by blocking sunlight; this treatment can be seen as a complementary to greenery, in that it helps reflect part of the sunlight that isn’t blocked by plants such as trees.

The titanium dioxide in the spray scatters and absorbs both visible light and ultraviolet rays — which makes it a popular component in sunscreens — but it also starts a chemical reaction in the presence of light which oxidizes and breaks down pollutants. Although it’s still in the pilot phase so the figures aren’t final yet, Pavement Technologies says its treatment so far has reduced levels of nitrogen oxide (NOx) by 30% to 40% in areas where it’s being trialed. One mile of roadway sprayed with this treatment has the same pollution-eating effect as 20 acres of trees, the company further claims.

The compound is being tested in three regions in Charleston County as of April 2021.

Still, its main intended role is to keep roads working for longer. The spray works by replacing compounds known as maltenes in old asphalt. Maltenes are found in bitumen, the black, oily fraction of asphalt, and they’re what gives fresh asphalt its bouncy, flexible nature. Over time, however, they degrade, and the material becomes brittle, cracking under strain.