Dealing with icy patios, driveways and sidewalks are a fact of life in northern climates where snow and winter conditions are a regular occurrence. There are many different ways to deal with ice, whether using one of many chemical compounds to melt it or using more environmentally friendly products to provide traction and prevent slippage.
De-icers — How Do They Work?
Ice melt products attract moisture to themselves to form a liquid brine which generates heat and melts ice. The product must reach the pavement to become effective. Once on the pavement the brine can spread out and break the bond the ice has with the pavement. As the ice is loosened, it can more easily be shoveled away.
Every year there are more and more choices when it comes to de-icers. A lot of the choices are very similar and differ only in marketing with each product claiming to be the best. Ninety-five percent of all de-icers are made from one, or a blend, of five products. Typically blends are made to try and combine the best advantages of each chemical.
- Calcium chloride – This is basically traditional ice melt. It will melt ice to temperatures of -32C. It gives off heat as it dissolves which melts the ice quicker but leaves a slimy residue. It is corrosive to metal and can be damaging to vegetation if over-applied. Magnesium chloride is a very similar product and becoming more popular. It is less corrosive and safer on concrete and plants.
- Sodium chloride (rock salt) – Rock salt is the least expensive and very efficient. Will melt ice to temperatures of -7ËšC. Effective at drying out icy surfaces. Not as harmful to concrete as other products but can be damaging to vegetation and is corrosive to metal.
- Potassium chloride – Is more expensive than other products. Works well when mixed 50/50 with rock salt. Will melt ice to temperatures of -11ËšC. Relatively safe but can still cause plant injury if over-applied.
- Urea – Commonly used as a fertilizer but is also an effective ice melter. Will melt ice to temperatures of -10C. Over application can harm vegetation.
- Calcium magnesium acetate (CMA) – Is made from dolomitic limestone and acetic acid (main compound in vinegar). It has little affect on plants and concrete but its performance decreases at temperatures below -7C. It works differently than other materials in that it does not form a brine like salts. CMA helps prevent snow particles from sticking to each other on the road surface. It prevents re-freezing more than it melts ice and tends to leave a slush.
Are They Harmful?
Given the alternative of dangerous conditions, the benefits can outweigh potential disadvantages. All de-icers have the potential to damage vegetation, concrete and corrode metal. Moderate use combined with adequate rainfall to dissolve and wash away product should be enough to protect vegetation and hard surfaces.
Damage to concrete occurs not from the effects of the salt but from the effects of the freezing point of water. When the freezing point of water is lowered (by creating a brine), the number of freeze/thaw cycles increases and the expansion of freezing water (hydraulic pressure) can exceed the strengths of concrete.
Other, more natural, products can be used to treat icy sidewalks and driveways. Although they are generally less effective, they pose less harm to the environment and pets. Natural alternatives like sand, poultry grit, sawdust, wood shavings, and kitty litter are mainly effective for their gritty, anti-slip qualities. They provide better traction to walk on the ice but do not actually melt ice. They are often mixed with ice melt products as a way to use fewer chemicals.