This time of year we receive many calls asking if it’s safe to use deicing products on pavers used in patios, walks or driveways to remove snow and ice. Here is what I tell our clients:
Common chemical deicers such as sodium chloride (rock salt), calcium chloride and potassium chloride, do not chemically attack concrete. Instead, these products mix with the water in snow and ice to form liquid brine which lowers the water’s freezing point. As the snow and ice melts on unsealed or porous concrete, some of it will seep into the concrete, saturating it with brine and moisture. When the temperatures drop, this brine and moisture can refreeze and expand. This creates pressure on the concrete’s surface and may cause chipping, flaking, pitting, and other concrete damage. Some of these products also leave a salt residue on pavers that can be difficult to remove and can damage your plants.
If you have concrete paving stones or permeable pavers in your walk, patio or driveway, you can safely use these common deicing products in moderation. Most pavers today are manufactured to very high standards that meet or exceed strict ASTM standards relating to strength and density. They must achieve a rating of 8,000 psi (pounds per square inch) in order to be considered a “concrete paver”. At this level, the concrete does not absorb very much water and therefore the water typically will not freeze and expand within the paver. Any pavers, poured concrete or paving stones that have been sealed have an added layer of protection that minimizes or eliminates the possibility of any water being absorbed. These sealers will also keep the salt residue from staining and penetrating into the paver.
Keep in mind that poured concrete, stamped concrete, brick and some natural stone are much more susceptible to damage because they are more porous than concrete pavers. Avoid using deicers on these surfaces unless absolutely necessary. Be sure to rinse off thoroughly as soon as possible, and then in the spring have them cleaned and sealed to protect them in the future.
As an alternative to using chemical deicers, you can use sand or cat litter. This will not melt the snow and ice, but it will provide traction. They are safe for the landscape and can be easily swept up when they have accomplished their job.