Tag Archives: asphalt

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.

Asphalt is a major source of air pollution, especially during summer weather

A petroleum-based substance, asphalt is almost everywhere, from roads and roofs to driveways and paved streets. The US alone has about 18 million tons of it. Unfortunately, it seems that all that asphalt is also the source of air pollution, especially in the summer heat, according to a new study.

Credit TexturePalace. Flickr (CC BY 2.0)

Researcher Peeyush Khare from Yale University and his team were curious about the potential impact of asphalt on air quality, especially in cities, as about 45% of urban surfaces are covered with asphalt. Its uses include paving (mixed with stone aggregate), roofing, and in products such as sealants.

No studies have previously quantified emission rates, which are essentially absent in emission inventories. The only exception has been solvent evaporation from cutback asphalt application, which was found to have elevated concentrations of hazardous air pollutants.

The researchers worked with samples of asphalt in an enclosed furnace in order to study their emissions in detail. They exposed the samples to temperatures from 40ºC to 200ºC. Not only did the asphalt release emissions, but their levels doubled when the temperature went from 40ªC to 60ºC, the study found.

The pollutants released were all carbon-based chemicals, Drew Genter, co-author, told New Scientist. “Many of these compounds are conducive to condensing to form secondary organic aerosol after reacting in the atmosphere,” he added. This can later form particles called PM2.5, a dangerous type of air pollution.

The study also looked at the effects of exposing asphalt to moderate solar radiation, finding a 300% increase in emissions for road asphalt. This proves that solar radiation, and not only temperature, can increase emissions.

“That’s important from the perspective of air quality, especially in hot, sunny summertime conditions,” Khare said.

More emissions from asphalt are soon to come, the researchers argued. Climate change is increasing global temperatures, which lead to more emissions. “Megacities are likely to see urban temperature increases driven by climate change and urban heat island effects,” said Gentner.

The researchers rejected making any policy recommendations as first they want to know how much pollution the asphalt emits over its lifetime and how it interacts with other sources of pollution. Nevertheless, they highlighted ongoing research on coal pavement coatings, which may reduce emissions by cooling the asphalt.

Air pollution is the greatest long-term risk to human health as it cuts life expectancy by nearly two years, compared to what it would be if air quality met the World Health Organization (WHO) guideline, according to the Air Quality Life Index. The most affected countries are Bangladesh, India, Nepal, and Pakistan.

The combined effects of ambient (outdoor) and household air pollution are responsible for about 7 million premature deaths every year, largely as a result of increased mortality from stroke, heart disease, chronic obstructive pulmonary disease, lung cancer, and acute respiratory infections. This especially affects people living in urban areas.

The major outdoor pollution sources include vehicles, power generation, building heating systems, agriculture/waste incineration, and industry. In addition, more than 3 billion people worldwide rely on polluting technologies and fuels for household cooking, heating, and lighting, releasing smoke into the home and leaching pollutants outdoors.

The study was published in the journal Science Advances.

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.

Potholes could be fixed by asphalt-printing drones

Finally, it feels like we’re in the future!

If there’s one small thing all motorists hate, it’s potholes. Nothing can ruin your day like an inconspicuous, well-placed pothole — and often times, it takes forever to patch them up. But all that may soon change, thanks to a new futuristic invention by University of Leeds researchers, who have proposed and developed an unorthodox approach to pothole repairs.

They “trained” image recognition algorithms to detect potholes, and then installed them into drone cameras. After the damaged areas were identified, a drone was dispatched to the site, using an on-board asphalt 3D printer to patch the hole.

Intriguingly, while it may rightfully seem a bit overkill to use complex algorithms, drones, and 3D printers to patch potholes, researchers say this may actually save municipalities money in the long run. Phil Purnell, professor of Materials and Structures at the University of Leeds, told Digital Trends:

“When you look at interventions in infrastructure — whether it’s roads, pipes, bridges, or similar — you’re very often using ton and meter-scale solutions for problems that started out as gram and millimeter-scale defects,” he said.

 

Image credits: University of Leeds.

Potholes often start out as small holes but can grow very quickly, and identifying and fixing them quickly can prevent a lot of costs further down the line. If the drone can reliably identify and patch things up, it might be very worth it.

Researchers University College London, who have built the asphalt extruder mounted on the Leeds drone, say that the patching has an accuracy of about 1 mm.

This is not a singular approach — it’s part of a multi-university project looking at the possibility of self-repairing cities, using robotics and modern technology to repair and maintain infrastructure.

While this all sounds incredibly cool and useful, it will still be a while before the technology actually hits the road, as this is only a proof of concept so far. But if you think about it, things that seemed sci-fi a few years ago are already becoming commonplace.

“From a technical view, this is like Formula 1,” he said. “Twenty years ago the idea of [technology such as] energy recovery through braking systems was something that was seen as exotic when it was used on Formula 1 cars. Now it’s commonplace in many hybrid vehicles that you can drive about on the road today. It’s the same thing here. This is all about demonstrating how we can glue the various pieces of this puzzle together. We’re academics, so it’s our job to look at the high concept approach. Through our interactions with industry, they’ll then be able to find ways of implementing it.”

Scanning electron microscope images show an anode of asphalt, graphene nanoribbons and lithium at left and the same material without lithium at right. Credit: Rice University.

Scientists add asphalt to lithium batteries that charge up to 20 times faster

Just a touch of asphalt is enough for high-capacity lithium metal batteries to charge 10 to 20 times faster than the commercially available lithium-ion variety. Additionally, the novel batteries last longer and are safer than current alternatives.

Scanning electron microscope images show an anode of asphalt, graphene nanoribbons and lithium at left and the same material without lithium at right. Credit: Rice University.

Scanning electron microscope images show an anode of asphalt, graphene nanoribbons and lithium at left, and the same material is shown without lithium at right. Credit: Rice University.

These findings were reported by a group of scientists at Rice University led by chemist James Tour. The team used porous carbon made from an asphalt derivative — specifically, untreated gilsonite — to develop the anode for their high-capacity battery. The asphalt was mixed with conductive graphene nanoribbons, and the composite was coated with lithium metal through electrochemical deposition.

When put to the test, the battery exhibited a discharging/charging rate of 20 mA/cm2 — 10 times faster than that of typical lithium-ion batteries (LIBs). The discharge rate was also up to 20 times faster than LIBs, the authors reported in the journal ACS Nano. What’s more, the device exhibited stability even after more than 500 charge-discharge cycles.

“The capacity of these batteries is enormous, but what is equally remarkable is that we can bring them from zero charge to full charge in five minutes, rather than the typical two hours or more needed with other batteries,” Tour said in a statement.

Applications requiring high-power density, as well as rapid charge and discharge could make good use of such devices. Electric cars, which are getting cheaper and rising in sales, will need a fast charging infrastructure if they’re ever to take off, for instance. When it takes just a few minutes to charge electric cars with enough power for them to drive hundreds of miles, their popularity will increase exponentially.

Due to their exceedingly high specific capacity and extremely low electrochemical potential, lithium metal batteries have been on the minds of scientists for some time. What prevented them from reaching the market is an inherent flaw concerning dendrite formation. These are mossy deposits which invade the battery’s electrolyte, which with time short-circuit the anode and cathode. When this happens, the battery fails and can even explode. Up until now, this has remained a challenge for its practical applications.

The asphalt-derived carbon prevents any dendrite formation, however. Previously, Tour and colleagues showed that lithium metal batteries whose anode is composed graphene and carbon nanotubes also prevented the formation of dendrites. The new asphalt composite anode, however, is far simpler and cheaper to make.

“While the capacity between the former and this new battery is similar, approaching the theoretical limit of lithium metal, the new asphalt-derived carbon can take up more lithium metal per unit area, and it is much simpler and cheaper to make,” he said. “There is no chemical vapor deposition step, no e-beam deposition step and no need to grow nanotubes from graphene, so manufacturing is greatly simplified.”

Old tires become material for new and improved roads

Scrap tires, which are very problematic to dispose of and can cause many problems, can now be used to lower road noise and reduce need for road maintenance.

Almost 300 million scrap tires are generated every year in the US alone, according to the Environmental Protection Agency (EPA). You may wonder what’s exactly happening with these wheels, and it’s a pretty good question – but the answer is not pretty. At best, they end up in landfills, but in some cases they become breeding grounds for disease-carrying mosquitoes and rodents. They also carry a significant fire hazard, and are very rarely recycled.

It’s easy to understand why, in recent years, efforts have been made to turn this problem into a sustainable, eco friendly and economically viable solution. Magdy Abdelrahman, for example, an associate professor of civil and environmental engineering at North Dakota State University, is working on ways to turn old tires into new and improved roads. He is experimenting with “crumb” rubber–ground up tires of different sized particles–and other components to improve the rubberized road materials that many US states (and non-US as well) are using to improve aging asphalt.

“It’s very durable,” he says. “We mix it with different materials and in different percentages, and in different conditions, to find the best ways to add rubber to asphalt.”

Despite what you may think, tires are not the world’s largest market for rubber. That pedestal is taken by asphalt rubber, consuming an equivalent of 12 million tires every year. When combining asphalt with tire rubber, it becomes more resilient and sturdy, also lowering the noise created in the driving process. But perhaps the biggest advantage is the elimination of excess, hazardous tires.

“This project will have a broad impact because solid waste is problematic throughout the world,” Abelrahman says. “Asphalt applications have the potential to contribute to the solution of the growing solid waste problem provided that engineering and environmental concerns are addressed. Asphalt binders represent an area that can improve pavement performance.”

Of course you can’t just take old tires, melt them, mix them with asphalt, and expect to have good results. Abdelrahman studies what additives can be used to improve this mix, as well as how it does under different environmental conditions.

“We want to assess the environmental impact of adding components to the mixing of crumb rubber and asphalt, for example, is it going to leach out in the rain?” he says. “Traditional, that is, normal, asphalt-rubber materials will not cause harm to the soil or the ground water. But some additives may. We already know that the technology [rubberized roads] is proven to work, but we want to make it work much, much better,” he adds. “We are trying to find the scientific and engineering aspects to make it better and, at the same time, be sure it is environmentally friendly.”

It’s really important to start recycling old materials in a useful and sustainable way, because otherwise, the next generations will simply have nothing left to use.

“It is really important for them to understand that if we keep using new materials, that our grandchildren won’t have anything left,” he concludes.

Via National Science Foundation