Researchers at Drexel University have shared promising findings on the development of a self-heating concrete, which could not only save people the hassle of shoveling out the sidewalk on a snowy day, but it could also reduce the use of salt to deice walkways. 

According to the U.S. Environmental Protection Agency (EPA), salts used for deicing can runoff into local waterways, leading to contamination. High chloride levels in the water can be toxic to aquatic life, while salts on sidewalks and roads accumulate and can kill the wildlife on land that eat them. These salts can also damage roads, vehicles, bridges and other infrastructure, leading to $5 billion in repairs per year in the U.S. 

The researchers’ self-heating concrete is currently in use on Drexel’s campus by way of two 30-by-30-inch slabs of the material, which they have been developing for the past 5 years. The two slabs on campus have been in action for the past 3 years. 

In field tests, the slabs have so far been effective in keeping snow, sleet and ice buildup at bay, even when the rest of the surroundings have needed to be shoveled or salted.

“One way to extend the service life of a concrete surfaces, like roadways, is to help them maintain a surface temperature above freezing during the winter,” Amir Farnam, associate professor in the College of Engineering, whose Advanced Infrastructure Materials Lab leads the research, said in a statement. “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 to maintain a higher surface temperature when the ambient temperature around it drops.”

The concrete material uses a low-temperature liquid paraffin to help the slab release heat, even when the outdoor air gets colder. The researchers combined the liquid paraffin directly into the concrete mix for one slab; for the other slab, the team treated a lightweight aggregate made up of small pebbles and stone pieces with liquid paraffin. They also created a control slab of traditional concrete.

Then, it was time to begin testing. The slabs have experienced 32 times when temperature dropped below freezing and five times when snow fell over 1 inch. For the two slabs with the liquid paraffin, they maintained a temperature of 42 to 55 degrees Fahrenheit for up to 10 hours when temperatures dropped below freezing. 

The slab that contained paraffin mixed into the concrete heated up faster, but did not stay warm for as long, while the slab with the treated aggregate was slower to warm but held its warmer temperature for longer. The team published their findings in the Journal of Materials in Civil Engineering and will continue their research to better determine how this material could be effective long-term.

The development of a self-heating concrete is one of several options experts are considering as alternatives to winter salts. Some other materials that have been used or tested for deicing include grape skin compounds, pickle or cheese brine and coffee grounds, although these alternatives may have negative environmental impacts as well. Heated snow mats and electric snow blowers could also be considered for snow removal.

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