Self-heating concrete

Researchers at Drexel University in the US developed a special type of concrete that can warm itself up when it snows or as temperatures approach freezing.

Concrete is sensitive to freezing temperatures, especially in combination with thawing, which all eat away at concrete roads. To help prevent this, the team at Drexel University developed self-heating concrete that is capable of melting snow on its own, using only daytime thermal energy and without the use of salt, shovelling or heating systems.

To the concrete, low-temperature liquid paraffin is added, a phase-change material. This means it releases heat when it turns from its room temperature state, liquid, to a solid material when temperatures drop. The paraffin can be added as microcapsules directly into the concrete, or porous lightweight aggregate can be treated with the liquid.

The researchers poured one slab using each method and a third without any phase-change material, as a control. All three have been outside in the elements since December 2021. In the first two years, they faced a total of 32 instances in which the temperature dropped below freezing, and five snow falls of an inch or more.

Using cameras and thermal sensors, the researchers monitored the temperature and snow and ice-melting behaviour of the slabs. The phase-change slabs maintained a surface temperature between 42- and 55-degrees Fahrenheit for up to 10 hours, when air temperatures dipped below freezing.

This heating is enough to melt a couple of inches of snow, at a rate of about a quarter of an inch of snow per hour. And while this may not be warm enough to melt a heavy snow event before ploughs are needed, it can help deice the road surface and increase transportation safety, even in heavy snow events.

Image: Drexel University via EurekAlert