Deicing Salts and Concrete
Although a concrete pavement is hard it is also like a sponge, that is, it absorbs water and the waterbourne chemicals. We all have seen this while washing our vehicle when water spray soaks into the concrete before it begins to puddle.
In the summer the absorption of water is not a problem; however, in the winter a concrete pavement can become damaged when deicers turn ice and snow into water which soaks into the concrete, especially when the water freezes again later.
Among the most popular deicers sold at discount stores are calcium chloride, magnesium chloride, and sodium chloride. Unfortunately, all are known to pose a risk of causing damage to concrete, especially relatively young concrete (less than two years old).
In the paper, The Deleterious Chemical Effects of Concentrated Deicing Solutions on Portland Cement Concrete (Apr 2008), by Lawrence Sutter of Michigan Tech calcium chloride and magnesium chloride pose greatest risk of causing damage to the concrete material. Mr. Sutter recommends that to reduce the risk of damage any deicers used should be applied minimaly. He also notes that sealing the concrete before winter will reduce the permeability of concrete and thus, the effects of the deicing agent.
I have not been a big user of deicing agents because of my fear of damaging the concrete. However, as I age and care for my Mom’s driveway I have noticed that I have become more liberal in my use of deicing agents. I have applied rock salt (sodium chloride) on my Mom’s driveway for about fifteen years with no apparent damage. Her driveway was over 30 years old when we started applying the rock salt.
On my own driveway I have used all three products with no apparent damage yet. But I use a deicer sparingly, that is, only when we find ourselves slipping on the pavement. I had also applied Thompsons Water seal annually to the driveway when we had long term parking on the driveway for our kids vehicles. Thompsons is a linseed oil based material that soaks into the pavement, darkens it a bit, and increases impermeability. It appears to have provided good protection with no apparent scaling or spalling, but this could just be testimony to good concrete and good concrete workmanship.
Of course when choosing a deicing agent there is also the consideration of damage to nearby plants, the environment, and pets.
I am probably going to stick with rock salt (sodium chloride). My thought is: if I can sprinkle a little on my mash potatoes at dinner time, how bad can it be.
But whatever you use remember – USE SPARINGLY (the least amount you need to get your goal accomplished).