While winter poses many challenges already, having to deal with cracked or chipped concrete after applying deicer is never pleasant. This chipping or cracking can occur when a corrosive ice melt product is applied in excess and is allowed to penetrate and damage the concrete. The corrosive function of most ice melts can be classified into two components: (1) the effective temperature of the deicer (the temperature at which the deicer and the melt water will refreeze), and (2) the concentration of chloride in the product. Using these two metrics, we will evaluate the corrosiveness of most conventional ice melt products, and provide some solutions when selecting a non corrosive ice melt. Let's begin!
How to minimize the damage to concrete?
While concrete and asphalt are very resistant to corrosion by deicing products, they are commonly damaged by improper use or the application of a deicer to concrete that is not strengthened. Concrete is incredibly resistant to scaling and damage if it is properly mixed, placed, and cured according to the recommendations of the American Concrete Institute. Having said that, it is still not recommended to apply a deicer to concrete that is less than 1 year old, has been precast, has exposed aggregate, has been stressed in the past, or chipped cracked, and weathered in any way. This is why we recommend waiting to apply the ice if your concrete is less than one year old, or using mechanical methods to remove the snow and ice.
The impact of the effective temperature of the deicer.
As discussed above, the effective temperature of the deicer is the temperature at which it refreezes. This temperature will vary depending on the product, and the environmental conditions outside. For conventional rock salt, sodium chloride, or potassium chloride, that effective temperature will be in the range 20 -25 degrees Fahrenheit. This means that if the temperature outside drops below 20 degrees Fahrenheit, your ice melt will refreeze and potentially damage your concrete. Calcium chloride on the other hand, has the lowest effective temperature of all commercially available ice melt products. Calcium chloride will work down to -25 degrees Fahrenheit, substantially below that of other common deicers. This means that if you live in Northern or Northeastern regions of the United States as well as Central Midwest, calcium chloride ice melt should be the product of choice during deep winter conditions.
How to Chloride concentration affects corrosion?
When people talk about non corrosive ice melt, they are typically referring to the amount of chloride that is in the product. As the deicer melts the ice and snow that it comes in contact with, the dissolved ice seeps into the cracks in concrete and asphalt where it may come in contact with the reinforced rebar, steel, or pipes. It is this action of the chloride that reacts with the iron in the metal, rusting the steel and causing the deicer to be “corrosive.” This is where not all commercially available deicers are made equal.
For a conventional rock salt or sodium chloride, the typical application is approximately 5 lb per 100 square feet of area. This is because rock salt requires a substantially higher application, to be effective. For a more environmentally friendly ice melt, like calcium chloride, the application rate is substantially lower. For example, for Eco Garden Calcium Chloride Ice Melt, We recommend applying at a rate of 1- 4 lbs Per 500 square feet. This means that even at the highest application rate recommended (4lbs per 500 sq.ft.), calcium chloride will apply not only 6.25 times less product, but also 6.25 times less chloride to your concrete or asphalt. At the lowest application rate (1 lb per 500 sq. ft.) you would be applying nearly 25 times less product per the same area, delivering 25 times less chloride. What this means for you, and your concrete or asphalt, is that applying a non corrosive ice melt like calcium chloride, is substantially better not only for your wallet, but also for the environment, and your concrete driveway.