Friday, December 10, 2010

Deicing Salts and Concrete Driveways and Vegetation

By Mark J. Donovan

In preparation for winter weather it’s always wise to buy a few bags of deicing salt and have them handy in the garage. However it is important to understand that deicing salts can wreak havoc on concrete driveways and walkways and can damage adjacent shrubbery and vegetation. In addition, there are number of deicing salts available on the market, each with their own unique pros and cons, and that are designed to work effectively at different temperatures. So which one do you use?

All deicing salts do basically one thing. They lower the melting point or freezing point of water. Their effect is to cause the ice to melt and stay in a liquid water state at lower temperatures.

Sodium Chloride, or rock salt, is the most commonly used deicing salt, and it can effectively melt ice down to about 15o Fahrenheit. Unfortunately it is very corrosive to concrete and metal, and can damage vegetation. It also produces a high amount of Chloride ions which is not healthy for the environment. Consequently rock salt should be used sparingly and on asphalt driveways only.

Potassium chloride is another common deicing salt, however it is effective only down to 20o Fahrenheit and it too easily damages concrete.

Calcium chloride dicing salt is another option. It melts ice even faster than Sodium Chloride and can effectively melt ice down to -20o Fahrenheit. It can be an irritant to skin and it too is corrosive to concrete.

The last fairly common dicing salt is Magnesium Chloride. Similar to Sodium Chloride it works down to around 0o Fahrenheit, however it is less damaging to concrete and vegetation. It also releases fewer Chlorides ions than Sodium Chloride.

So this winter make sure to stop by the local hardware store and pick up the right dicing salt for your climate, and driveway and sidewalk surface conditions. Regardless of what deicing salt you choose, the best rule of thumb is to use it as sparingly as possible. By doing so you can accomplish your main goal of eliminating ice build up on your driveway or sidewalk, while at the same time minimizing environmental harm to your concrete surfaces and localized vegetation.

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