Slipping and sliding on snowy or icy roads is dangerous. Salt and sand help melt ice or provide traction, but excessive use is bad for the environment and can run into nearby water channels and pollute it.
They can also degrade the same roads that they’re de-icing. In addition to this, they cause cars to rust and they have to be applied repeatedly throughout the winter. Even then, once a fresh layer of ice forms on the asphalt, drivers are stuck with it until the ice-spreading trucks arrive again.
Scientists from China’s Hebei University of Science and Technology have developed an ice-melting additive for asphalt that could remain active for years.
They have started out by developing a chloride-free acetate-based salt. Such salts are considerably less environmentally harmful than chlorides, they’re less corrosive to steel and other materials, plus they work at lower temperatures.
The researchers proceeded to mix the salt with a surfactant, silicon dioxide, sodium bicarbonate and blast furnace slag (which has also been used in salt-proof concrete), resulting in a fine powder. Particles of that powder were then coated with a polymer solution, producing microcapsules.
Finally, the scientists replaced some of the mineral filler in a conventional asphalt mixture with those capsules.
When the special asphalt was tested on the off-ramp of a highway, it was found not only to continuously melt the snow that fell upon it, but also to lower the freezing point of water from 0C (32F) down to -21aC (6F).
Based on lab tests, the researchers estimate that a 5-cm (2-in)-thick slab of the pavement would continue to release its salt capsules for seven to eight years, keeping the road clear that whole time.