Tag Archives: Pavement

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.

Hot pavement can cause second-degree burns within seconds

A new study found that when it’s over 100 degrees Fahrenheit (38 Celsius) outside, the pavement can cause serious burns in only two seconds.

It’s summertime, which means it’s heatwave season. Cities get abnormally hot throughout the year due to the urban heat island effect — largely due to paved surfaces and buildings, which capture more of the sun’s heat. Pavement covers as much as 45% of urban areas, and on a hot summer day, the surface of a road may get as hot as 60 degrees Celsius (140 degrees Fahrenheit).

Needless to say, at that temperature, touching the pavement with your bare skin is quite dangerous. But it can also be dangerous at lower temperatures.

In order to assess just how hot is too hot, a team of surgeons from the UNLV School of Medicine reviewed all the burn victim cases from a Las Vegas burn center, taking into consideration the outside temperatures.

For starters, they found that pavements are indeed a contributor to burn cases. Due to its thermal behavior, it can easily get much hotter than the air temperature, and it passes that temperature with generosity. In other words, it gets hot and it can burn you.

“Pavement burns account for a significant number of burn-related injuries, particularly in the Southwestern United States,” said Dr. Jorge Vega, UNLV School of Medicine surgeon and the study’s lead author. “The pavement can be significantly hotter than the ambient temperature in direct sunlight and can cause second-degree burns within two seconds.”

Over 88% of related incidents occurred when temps were 95 degrees or higher, and the risk increases exponentially as temperatures exceeded 105 degrees. Paved surfaces get much hotter than the ambient air — up to 30 degrees F hotter — and while no one really wants to touch hot pavement, some people might not have a choice (like those who fall down or are in accidents), or they might not realize the dangers that lurk, even with a short touch.

The problem is that even when it’s not very hot outside, the asphalt can still get much hotter than the surrounding environment.

Researchers say this information can also be useful for medical centers. When it gets very hot, they can prepare for an increased likelihood of burn accidents.

“This information is useful for burn centers in hotter climates, to plan and prepare for the coordination of care and treatment,” says Vega. “It can also be used for burn injury prevention and public health awareness, including increased awareness and additional training to emergency medical service and police personnel when attending to pavement burn victims in the field.”

As the current climate crisis continues to unfold, heatwaves will become much more common. This is another example of an unexpected consequence caused by this phenomenon.

France announces plans to pave 1,000 kilometers of road with solar panels

The French government announced its plan to build a 1,000 kilometer (621 mile) long stretch of solar panel-paved roads over the next five years. The locations for deployments have yet to be revealed. The fossil fuel tax is expected to bring in between 200 to 300 million euros ($220 to 440 million) of funding for the project coined “Positive Energy” .

Test laying of the Wattway panels.
Image via GCR

Paving roads with photovoltaic solar panels is an idea first put in practice in the Netherlands in 2014. The French government has announced plans to take that concept one step further and build a total of 1,000 kilometers of power-generating roads over the next five years. Their goal is to provide enough clean energy for 5 million people — about 8 percent of the current French population.

The roads will be built using Wattway panels, a photovoltaic technology unveiled last October by the major French civil engineering firm Colas. It took the firm five years to develop the panels that can be glued directly on top of existing pavement. These seven millimeter-thick strips harvest solar energy using a thin film of polycrystalline silicon, provide enough traction and are solid enough to withstand all types of traffic — Colas tested them under the weight of a 6-axle truck and they worked just fine.

“[The panels were tested on a] cycle of one million vehicles, or 20 years of normal traffic a road, and the surface does not move,” said Colas CEO Hervé Le Bouc.

The solar pavement also withstood the snowplow test, but the company recommends operating the machines with “a bit more care” than on pavement.

Colas CEO Hervé Le Bouc holding a Wattway panel.
Image via inhabitat

France’s Agency of Environment and Energy management states that four meters (13 feet) of solarized road is enough to power one household’s energy needs, not including heating, while one kilometer (3,281 feet) can supply enough electricity for 5,000 inhabitants.

According to Ségolène Royal, France’s minister of ecology and energy, the “Positive Energy” project will be funded by raising taxes on fossil fuels, a decision Royal says is “natural” given the low prices of oil. This is expected to cash in some 200 to 300 million euros ($220 to 440 million) in funding for the project.

Tenders for the “Positive Energy” initiative have been issued and tests on the solar panels will begin this spring. The government has yet to reveal the locations of the new roads.