3 AVOID CHEMICAL DAMAGE TO CONCRETE & LANDSCAPE
Salt and/or other de-icing chemicals will do damage to your lot, and may kill surrounding landscaping. Concrete has high strength when it is compressed, or ‘squeezed’. However, it is extremely weak when it is subjected to tension, or ‘pulled’. Salt can take advantage of this weakness. Although concrete appears to be a very dense material, it can and does absorb water.
When you spread salt on your concrete to melt snow and ice, the salt dissolves the snow and makes a salt water mush. The melting action of the salt allows water to enter the concrete. If the temperature then drops and the water freezes, the growing ice crystals can blast apart the concrete. And since salt is also hygroscopic, it attracts and retains water. It can cause concrete to become more saturated with water than it would otherwise. The presence of this extra water in freezing conditions is the problem. The volume of water increases by 9 percent when it freezes within the concrete matrix. The pressure of the growing ice crystals can cause the surface of the concrete to fail. It usually chips off.
Freshly poured concrete is most susceptible to damage. Concrete placed in the late fall needs at least 30 days of drying time. Ironically, this is the time when most car wash construction is happening. This young concrete is still highly saturated with water. The water within the concrete can freeze and cause the surface to pop off.