researchers at drexel university (philadelphia, pa.) have discovered a unique use for paraffin wax, as a phase-change material in concrete mix to store energy and release it as heat when the road needs to be cleared of snow in the winter.

researchers from drexel, purdue and oregon state have discovered that adding phase change materials, such as paraffin oil, to concrete can give surfaces the ability to melt ice and snow. (drexel university)

according to a report from drexel, researchers from purdue university (west lafayette, ind.) and oregon state university (corvallis) collaborated on the breakthrough that has the potential to reduce the dependence on snow plows, deicing chemicals, and road salts. all of those can wear down the road surface and the last two have environmental impacts as runoff into local waterways.

the paraffin oil can be added to porous concrete aggregate or in embedded pipes. as the phase-change material converts from liquid to solid during cooling events, it releases thermal energy that can melt ice and snow.

“paraffin oil, a common ingredient in candles, wax polishes, cosmetics and water-proofing compounds, was their material of choice for this endeavor because it is organic, widely available, chemically stable and relatively inexpensive,” the article explained.

it added, “like all phase change materials, it releases thermal energy when it changes its physical state, which means as temperatures drop and the oil begins to solidify it releases energy through latent heat of fusion. this means paraffin oil can be tailored to embed deicing capabilities in a road surface so that it becomes thermally active during snow events or when deicing is needed.”

the researchers tested the effect of paraffin using a set of concrete slabs, one with paraffin-filled pipes, one with porous lightweight aggregate infused with paraffin, and a third slab without. each was covered with five inches of man-made snow.

“with temperatures inside the boxes held between 35-44°f, both of the paraffin-treated slabs were able to completely melt the snow within the first 25 hours of testing, while the snow on the reference sample remained frozen,” the report said. “the slab with the paraffin-filled tubes melted the snow slightly faster than the one composed of paraffin-treated aggregate.”

in the second experiment, the team lowered the temperature to freezing prior to adding the snow. in this test, the porous aggregate was more effective than the pipes. “this is because the capillary pore pressure delayed the freezing of the paraffin, thus allowing it to release its heat energy over a longer period of time,” the report noted.

with varied temperature changes, the researchers believe that the porous aggregate will be most effective and will be easy to implement in a variety of locations.

the research was published in cement and concrete composites. the abstract stated:

“this paper discusses the use of phase change materials (pcm) in concrete pavement as a method to store energy which can be used as a heat source during cooling events to melt ice/snow. the experimental program includes: (1) use of low-temperature differential scanning calorimetry to evaluate thermal properties of pcm, and (2) use of large-scale concrete slabs containing pcm to evaluate the ability of the pcm concrete to melt snow on the surface of the concrete pavement.

“the temperature in the concrete slabs and the snow melting rate were monitored as quantitative measurements of the efficiency of the pcm in the concrete. in addition, time-lapse images were taken. two approaches were used to incorporate pcm in concrete: placing the pcm in lightweight aggregate (lwa) which was then mixed into the concrete, and placing the pcm in embedded metal pipes embedded in the slab during concrete casting.

“in this study, paraffin oil was use as a pcm that is effective in releasing heat near the freezing temperature of pcm when the pcm undergoes a phase transformation from liquid to solid. the heat released during the phase transformation can melt ice and snow on the concrete pavement surface.

“the results indicate that incorporating pcm in concrete pavement is not only feasible, but also practical.”

see how this works in the video below: