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Energy Efficiency

The Future of Asphalt Unveiled in Charleston County, SC

Image courtesy of Umit Yildrim

Just as buildings all over the world have evolved in the last several decades to be more environmentally efficient, our nation’s roads are taking the first steps in their own journey to increased sustainability. To anyone not working in infrastructure or asphalt production, a road might seem a lot like toilet paper– sure, there have probably been improvements to the product in the last seventy or so years, but overall it’s still just a roll of paper, much like a road is still just a strip of asphalt for driving. This is a standard that has existed since the late 19th century in America, and it’s about to change dramatically. While municipalities across the country have been using substances like Reclamite to treat their roads for the last 50 years, a county in South Carolina has made waves for rolling out a new and improved treatment chemical. 

Like nearly everywhere else below the Mason-Dixon Line, Charleston County can be a hot place. Highway and construction workers are engaged in a constant battle with the sun and its detrimental effects on roads and highways, while county residents must drive on those same roads every day. One of the biggest sun-induced problems is the heat island effect. Because man-made structures like buildings and especially roads tend to absorb and re-emit the sun’s heat more than natural forests and bodies of water do, urban areas in hot climates are generally even hotter than their rural neighbors. An overview of the effect in the United States found that the difference was anywhere from one to seven degrees Fahrenheit in the daytime, and was even more pronounced in humid areas like the South. Charleston County officials have begun treating their roads with a photocatalytic material that contains titanium dioxide in order to better combat this effect. 

Image courtesy of Jonas Weckschmied

Serving as a testing ground of sorts for a future full-scale rollout, county workers recently sprayed the roads of the Rosemont neighborhood with this new chemical solution. While this solution is approximately double the cost of the typical Reclamite treatments that regularly occur every three to five years, that premium certainly makes an impact. Asphalt roads treated with this chemical solution have a variety of heat and sustainability needs to be addressed. The temperature of a treated road will be as much as twenty degrees cooler than normally treated roads, due to the increased capacity to reflect sunlight and thus reduced level of heat island effect. 

Environmentally, the difference is arguably even more pronounced. When cars and trucks drive, some of the particles given off in exhaust fumes, namely nitrogen oxides, will stick to normally treated asphalt. These toxins, which play a large role in the cause of acid rain and smog, are instead absorbed with the titanium dioxide solution, essentially removing them from the nearby environment before the next rainfall. Additionally, manufacturer Pavement Technology claims that the solution assists with the decomposition of microplastics. 

Image courtesy of Wes Hicks

As the company behind the new product, Pavement Technology Inc. is using Rosemont as just one of many testing sites, including parts of Raleigh, Charlotte, Greenville, Charleston, and Orlando. In collaboration with Texas A&M researchers, Pavement Technology is sending literal chunks of their treated roads called “road cores” as well as air quality data to the university to analyze the product’s efficacy. Ken Holton is confident that the treatment solution will work as advertised. “That’s really going to shorten that time period of that high effect of the heat island,” said Holton, who works as a technical consultant for Pavement Technology. He added that treated roads were already seeing a 30 to 40 percent reduction in nitrogen oxide levels. If true, that difference will have an impact on human health as well as environmental health, as these particulates could otherwise contribute to lung diseases if inhaled.

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