A drive to design safer, snow-free roads
S. Himmelstein | March 09, 2023
Steps in the preparation of the microcapsule type anti-icing agent. Source: ACS Omega 2023, 8, 5, 4906-4920
Maintaining snow- and ice-free roads during winter in many regions can be a labor-intensive chore. Mechanical means of removal can damage road surfaces while the application of salts to melt ice and snow incurs environmental penalties in the form of water pollution and materials corrosion. If only these roads could clear themselves without human intervention…
A promising solution developed by researchers in China offers a salty approach to achieving this goal. Microcapsules filled with a chloride-free salt mixture are added into asphalt prior to the paving of roads to deliver long-term snow melting capabilities. A fine powder is formed by combining a sodium acetate salt with blast furnace slag, silicon dioxide, sodium bicarbonate and a surfactant. Microcapsules are then formed with the application of a polymer solution and incorporated into asphalt mixtures destined for roadways.
Tests demonstrated that a pavement block incorporating the new sustained-release additive lowered the freezing point of water to -6° F. A 5-cm-thick layer of the anti-icing asphalt is expected to be effective at melting snow for seven to eight years. During additional trials of the anti-icing asphalt on the off-ramp of a highway, asphalt embedded with the microcapsules was observed to melt snow that fell on the road while traditional pavement required additional removal operations.
Scientists from Research Institute of Highway Ministry of Transport, Jing-Xiong Management Center and Hebei University of Science and Technology contributed to the development of this road safety solution, which is described in ACS Omega.
Current methods of salt application last 1-3 days (if applied as a liquid that dries), but these stripes also wear off and are affected by wind. The proposed method is expected to last 5-6 years, as a 5-cm (2-inch) top layer. The salt incorporated into this layer as encapsulated microparticles leaches out. This leaching probably follows an exponential curve from high effect initially towards zero effect over a time interval stretching into the future.
Unknowns to me are 1) effect of liquid precipitation and its ability to also leach out the salt--if freezing is needed to enable the leaching, 2) what to do with the eventually inactive asphalt layer--remove and replace or other possibilities, and 3) the overall monetary and environmental cost of this approach.
--JMM