New streets that can reduce the heat in cities
The United States has long been using a technique that our grandparents' grandparents used to deal with the high summer temperatures: painting surfaces white. But in this case it is not a normal paint, they use a coating based on titanium dioxide which, apart from repelling heat, captures and decomposes toxic emissions from exhaust pipes.
Anyone who lives in a city knows what it means to go outside in the middle of July, when the sun is at its highest. It's easy to get a light-headed headache just thinking about it. In the 19th century, the Anglo-Saxons gave a name to this extreme heat that occurs much more intensely in cities than in the countryside: the 'urban heat island'.
The 'urban heat island' refers to the increase in temperature caused by human activity. Tall buildings blocking the air flow, asphalted streets, metal roofs or concrete sidewalks make temperatures much higher than in places where nature is more present.
To combat this problem many American cities have long opted for a remedy that has been used for generations in hot countries like ours, paint surfaces such as floors, walls and ceilings white. But the paint being tested in some of the hottest states such as North Carolina, Orlando and Florida does more than just dissipate heat, it can also, according to its creators, reduce exhaust emissions by 30%.
The asphalt is made from tar, crushed rock, sand or gravel. All asphalts have two molecular structures in common: maltenes, which are responsible for holding the elements together, and asphaltenes, which give the road its black color and firmness. Over time, the maltenes eventually break down and the roads crack.
This material, created by U.S.-based Pavement Technology, is called Plus Ti and promises to be a rejuvenating treatment for roads. It is made from titanium dioxide, a compound that is capable of repairing malteno and returning it to its original characteristics. It is not white, but yellowish and is applied to the road by spray trucks like a sunscreen that disperses the sun's radiation, cooling the roads and reducing the 'urban heat island' effect.
Ken Holton, technical consultant for Pavement Technology, says the product is capable of extending the life of roads if applied just after the asphalt is laid. "It's very exciting," Holton comments. "We thought that reducing tailpipe emissions and cleaning the air for people to breathe was a big deal. And, all of a sudden, heat island [reduction] seems to be an important thing as well."
The company also calls this compound a "smog eater." When titanium dioxide receives sunlight, it is able, the company says, to capture and break down toxic emissions from exhaust pipes, as well as the nitrogen oxides and volatile organic compounds that make up smog - that mixture of smoke and haze produced by car emissions.
Pavement Technology is collaborating with Texas A&M University to see what role titanium dioxide plays in the breakdown of microplastics. Tire wear and tear has been found to be a major producer of tiny bits of plastic that end up in our oceans and end up in our fried fish, marinated dogfish or codfish.
