The issue of managing snow and ice on roads and walkways has been a constant challenge throughout the United States, particularly in regions with heavy snowfalls. As a result, the practice of using salt or sand to reduce the hazards of snow and ice has become a crucial part of public works and safety measures. The decision of whether to use salt or sand, and when to apply them, is imperative for preventing accidents during the winter months.
Is using road salt your Roman Empire? The use of salt for de-icing dates back thousands of years to ancient Rome, where it was used on roads to prevent them from freezing over in winter. In the early 1900s, the use of salt as a de-icing agent popularized in North America, particularly in cities such as Chicago and New York.
Since then, de-icing with salt has become standard in many parts of the world, although the choice between salt and sand, as well as the timing of its application, remains a matter of debate with many sides.
There are various perspectives on the debate of when to place salt or sand down for snow and ice. Proponents of salt argue that it is more effective in melting ice and preventing re-icing, especially as temperatures creep towards freezing. However, concerns about environmental and infrastructure damage caused by salt, as well as its negative effect on water quality, have led to cries for more sustainable alternatives.
On the other hand, advocates of sand argue that it is a safer and more environmentally friendly alternative to salt, particularly in areas near groundwater as contamination rates are higher. Sand does not have the same environmental impact as salt, and it can provide traction on icy surfaces without damaging infrastructure or vegetation. However, sand is not known to melt existing ice or prevent re-icing, making it less suitable for certain conditions.
Let’s dive deeper into the science of salt and sand. Let’s refer to our previous post: How Does Overnight Freezing Temperatures Affect Dispatch?: A Scientific Discussion with Snow Scholars
Water molecules bond together and this compaction forms ice. Sand works because the grains in the sand make it difficult for the water molecules to bond together and this prevents the formation of ice. It’s important to note that it does not melt existing ice, it just stops new ice from forming. Sand can also be utilized to allow cars to drive more safely on roads. The sand increases the friction for car tires, making it less slippery to drive. Alternatives may damage your plants and concrete, but sand is natural and won’t pose that risk. Salt on the other hand, composed of sodium chloride, lowers the freezing point of water causing ice to melt even when it’s below its normal freezing temperature (32°F). Sodium chloride dissolves into separate sodium and chloride ions that disturb the bonds between water molecules (H20). The ions loosen hydrogen bonds and the ice melts down to water (Scientific American, 2022). While effective at melting ice, road salt through runoff can contaminate drinking water. It also endangers wildlife and can increase soil erosion. Salinification (the increase of salt) affects how plants absorb their most essential macronutrient, nitrogen, that is imperative for growth. Raising salinity can also kill any sea life in nearby lakes by causing dehydration. Not to mention, it can hurt our furry friends. Salt can get wedged into some dog’s paws and cause irritation. This is not to say that there is not an appropriate time and place for salt, especially to prevent dangerous situations. Snow Scholars is committed to using salt sparingly, but when necessary to keep you and the environment safe. As a benchmark, around 12 ounces of salt should be used for a 20 ft long driveway. Our team members are educated on the appropriate salt to pavement ratios.
In recent years, there has been increasing research into the development of novel de-icing materials, such as potassium acetate and calcium magnesium acetate, which are less damaging to the environment than road salt. These alternatives are being used in some areas as a means of reducing the environmental impact of winter maintenance practices.
Looking to the future, we may soon see the use of drones and other advanced technologies play a greater role in the monitoring and application of de-icing materials. This could lead to more precise and efficient use of salt and sand, as well as improved safety and a reduced environmental impact.
~ Nina Petrosino, Snow Scholars Writer