Anyone who has survived a Northern winter is well acquainted with the dangers posed by winter travel, especially those posed by driving on snow covered roads. To combat this, we coat our streets in any number of chemicals, coatings, and sludges, designed to keep the pavement clear of ice and safe to drive. The North East, and the New England area especially, has become notorious for its gluttonous use of road salt to the exclusion of nearly all other additive methods. While cheap on the surface, this salt reliance has a number of serious drawbacks as described by our sister blog. Among the most easily seen are the fresh coatings of rust found on otherwise new cars and the "dead zones" along the highway. Many of these damages result in uncounted cost, both in individual burden and in the degradation of local ecosystems. While salt removal from water is both time and energy intensive, and thus prohibitive, salt alternatives could offer a greener solution.
*Sand*
Though sand frequently comes to mind when thinking of snow removal and winter driving, it functions as an abrasive rather than a deicer. The distinction drawn between an abrasive anda deicer lies in the effect it has on snow and ice. Compounds and chemicals are considered deicers through the molecular bonds they for with water molecules.
Deicers bond with water in such a way that they raise the freezing temperature enough to prevent solidification under normal circumstances. This ability is both the basis of the deicer's value as well as one of its major downfalls. Because these compounds are able break down both ice and snow while simultaneously preventing frozen accumulation, they allow us to keep roads relatively clear despite adverse weather conditions. This makes chemicals such as salt or Magnesium chloride extremely valuable from a driver safety and snow removal standpoint. However, because they operate by decreasing the freezing threshold of water, these reagents stop working once the new temperature threshold is reached. This also means that the reagents effectiveness decreases continually as the ambient temperature nears the new temperature threshold for freezing.
In contrast, abrasives work by increasing the amount of traction between a vehicle's tires and the existing ice or now pack. This has a number of implications, foremost, it does not contribute to snow or ice removal. However, because the mode of effect is not reliant on chemical bonding, the sand or other abrasive substance remains separated from the water and sand and can thus be more easily removed as particulate matter. Because of this notable difference of function, sand, as an abrasive, cannot be considered as a substitute for salt, a deicer. However, as mentioned in the solutions blog, the combination of salt and sand has a synergistic effect which enables highway maintenance and traffic engineers to use less of each product to achieve a greater result than would have been possible with only one compound or the other.
Resources for combination figures and results:
http://www.usroads.com/journals/p/rmj/9712/rm971202.htm
https://www.michigan.gov/documents/ch2-deice_51438_7.pdf