In cold areas that get heavy ice and snowfall, icy roads are a major obstacle and hazard. It is always a priority in these places to keep their highways and byways open by de-icing the roads. The two most prominent de-icers that many people use are salt and sand. Both are effective means of dealing with frozen streets, but they also have their drawbacks.
It’s important that you understand the mechanics of de-icing with either salt and sand, so you can figure out which one is best for you as you work out how to melt ice on your driveway or sidewalks.
What They Do -
Salt helps against icy roads by lowering the freezing point of the water in the snow and ice, causing it to melt and in ideal conditions, stay in liquid form longer. Pure water freezes at 32 degrees F, but a 20% solution of salt and water alters the water and lowers its freezing temperature all the way down to almost 0 degrees F.
However, to work on the ice, the salt must end up in a water solution. Currently, when roads are de-iced with salt, people do not splash a 20% saltwater solution on the road, they just dump crystallized rock salt and wait for sunlight, traffic friction, or heat in the pavement to melt some of the ice, or by the salt attracting water from the atmosphere. Once some of the ice has become liquid, the salt dissolves into it and prevents it from refreezing at similar temperatures.
You may find this misleading, but sand, while effective at managing ice, doesn’t melt the stuff either. Sand and other abrasive materials work by improving traction over ice. Friction may melt the ice, but this is an incidental addition to the functionality. This makes sense when you consider that the goal of de-icing a road isn’t just to melt ice, it’s to make the road safe and drivable which is exactly what sand accomplishes.
Salt removes the ice from the road, melting it as long as the temperature is not too low.
Sand can be used effectively at any temperature. As long as it is spread over the ice it will provide the necessary traction.
There is a limited temperature window in which salt can be used to de-ice roads. Salt isn’t magical, it just lowers the temperature at which water will freeze. If the normal forecast ever drops to that temperature, then the salt is useless and it freezes right along with the ice and snow.
Even within the effective range, more salt is needed the colder it is, and the slower it will work.
Also, dry snow will stick to a salted ice patch but will blow off an unsalted ice patch, so if the salt is applied during a storm it can cause further dangers on the road.
Ecological Impact of Using Salt
Salt and saltwater runoff contaminate the area around the road and down the drainage path. Vegetation within 60 feet of the road is damaged, and salt can contaminate groundwater and wells.
Salt will also degrade steel and concrete structures. This means using salt will damage the cars on the road, bridge structures, and even pavement. New construction techniques are minimizing this problem, but it is not yet solved.
If the weather is too cold, the sand can clump and freeze together, becoming part of the ice and providing no traction. Adding some salt can keep this from happening.
Sand is only effective as long it is on the surface. If it is buried under more snow, it must be reapplied. Heavy traffic areas will also quickly move the sand off the road, requiring regular reapplication.
Ecological Impact of Using Sand
Sand and other abrasive materials collect on the sides of the road, in drainage ditches, and can be washed into streams and lakes. Clean up after storms is becoming a bigger and bigger concern. Particles can also be ground up and become an air pollution concern.
Additionally, sand is often combined with salt to improve effectiveness, so all the environmental impacts of salt also apply to most applications of sand, just in smaller doses.
Neither sand nor salt is a perfect solution for removing ice from the roads. However, they are the best current options that are widely available.