New Phase-Change Concrete Melts Snow and Ice Without Salt or Shovels

Researchers have devised a self-heating substance that can melt snow and ice for up to 10 hours without the need of shovels or salt by incorporating a phase-change compound into concrete. The new substance may lessen the requirement for salting and plowing while helping to maintain the integrity of road surfaces.

The US Department of Transportation (DOT) reports that over 70% of roadways are in areas with snowfall. Accumulation of snow and ice decreases vehicle mobility and road friction, slowing down traffic and raising the possibility of collisions.

Besides the millions of dollars spent on restoring infrastructure damage brought on by snow and ice, the DOT reports that local and state governments spend more than $2.3 billion a year on snow and ice control activities. Before a snowfall, salt is frequently applied to prevent icing, yet the highly concentrated salt solution can damage asphalt or concrete. Water that penetrates the pavement and freezes expands, creating internal pressure and deteriorating the pavement.

Researchers from Drexel University, in the well-known “cold state” of Pennsylvania, describe their self-heating concrete in a recent study as a potential solution to snow-covered roads and the expenses related to cleaning and maintaining them.

“One way to extend the service life of concrete surfaces, like roadways, is to help them maintain a surface temperature above freezing during the winter,” said Amir Farnam, principal investigator at Drexel’s Advanced Infrastructure Materials (AIM) lab and one of the study’s corresponding authors. “Preventing freezing and thawing and cutting back on the need for plowing and salting are good ways to keep the surface from deteriorating. So, our work is looking at how we can incorporate special materials in the concrete that help it maintain a higher surface temperature when the ambient temperature around it drops.”

Paraffin, a substance known as a phase-change material because it produces heat when it transitions from a liquid form at ambient temperature to a solid one when temperatures drop, is the “special material” used by the researchers. Phase-change concrete was tested in a thermally controlled lab environment in a prior study, but in this one, real-world circumstances and real-time testing were used.

Paraffin was incorporated into concrete slabs using two different techniques. The first method involved soaking and absorbing porous lightweight aggregate—the tiny stones and pebbles added to concrete to give it strength—in liquid paraffin before mixing it into the concrete. In the second method, the concrete was mixed immediately with paraffin microcapsules.

Three slabs were poured by the researchers; two had paraffin included in different ways, while the third had no phase-change substance. Since December 2021, all three have been outside, close to a parking lot on the Drexel University campus. Over the course of the first two years, they experienced five snowfalls of one inch or more and 32 freeze-thaw occurrences, which were defined as periods when the temperature fell below freezing regardless of precipitation (rain, drizzle, snow, sleet, or hail).

Thermal sensors and cameras were used to track the snow and ice melting capabilities of the 30-by-30-inch slabs. When air temperatures dropped below freezing, the phase-change concrete kept its surface temperature between 42 °F and 55 °F (5.6 °C and 12.8 °C) for as long as ten hours, the researchers discovered. About a quarter of an inch of snow might be melted every hour at a rate of a few inches because of the heat generated.

“We have demonstrated that our self-heating concrete is capable of melting snow on its own, using only the environmental daytime thermal energy—and doing it without the help of salt, shoveling or heating systems,” Farnam said. “This self-heating concrete is suitable for mountainous and northern regions in the US, such as Northeast Pennsylvania and Philadelphia, where there are suitable heating and cooling cycles in winter.”

The micro-capsule paraffin heated up faster but only held heat for half the duration of the lightweight aggregate slab’s heating, which allowed it to stay above freezing for up to 10 hours. The porosity of the aggregate, according to the researchers, probably helps the paraffin stay liquid below its typical freezing temperature of 42 °F. This means that instead of releasing its heat energy right away when the temperature dropped, the slab held off until the material reached 39 °F/3.9 °C. In comparison, the paraffin slab that was microencapsulated started to release heat energy as soon as it reached 42 °F.

“Our findings suggest that the phase-change material treated lightweight aggregate concrete was more suited for deicing applications at sub-zero temperatures because of its gradual heat release within a wider range of temperature,” said Farnam.

According to the experts, concrete deterioration can be avoided if it can be kept from falling below freezing.

The study was published in the Journal of Materials in Civil Engineering.

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