Someone sent in a question and asked if spreading salt on their driveway and sidewalk would damage it. Thank you for the question. Here is your answer.
While concrete appears to be a very dense material, it is in fact quite like a blotter. It can and does absorb water. If you pour some water on your concrete, you can actually see the water penetrate the surface of the concrete.
When you spread rock salt on your concrete to melt snow and ice, the salt dissolves the snow and makes a salt water slush. 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.
Salt is also hygroscopic. It attracts water and moisture. It can cause concrete to become more saturated with water than it would otherwise. The presence of this extra water in freezing conditions can spell trouble. 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 end up spalling off.
Concrete placed in the late fall needs at least 30 days of drying time. This young concrete is still highly saturated with water. The water within the concrete can freeze and cause the surface to pop off. However, when Harmon Concrete pours a concrete driveway, we use enough cement in the concrete mixture and never dilute the concrete with the addition of water. This ensures the concrete will be able to resist the damaging forces of the freezing water.
Harmon Concrete always orders concrete that will attain a minimum compressive strength of around 4,000 pounds per square inch. When pouring exterior concrete such as concrete driveways and concrete sidewalks, we make sure the concrete is air entrained as well. These two things are an excellent defense against salt attack.
The placement and finishing of the concrete is highly critical as well. The surface of the concrete can be severely weakened by poor workmanship. Sometimes concrete companies will add water to their concrete at the job site or use it as a finishing aid. These practices dilute the amount of cement at the surface of the concrete. The cement is the main ingredient in concrete that holds everything together. To resist the freeze/thaw action of water, you need to have strong concrete at or near the surface.
There is an alternative to using rock salt. The sand will not melt the snow and ice, but it will provide you with traction.
If you still want to use ice to melt the snow and ice, you can have Harmon Concrete seal your concrete driveway, concrete sidewalk, concrete patio or concrete porch. This will allow you to use salts on your concrete without the typical damage associated with unsealed concrete.
Sealing your concrete with clear coatings will minimize or eliminate the possibility of water being absorbed by your concrete. Our exterior concrete sealers contain silanes and siloxanes. These ingredients allow the clear coatings to breathe. We avoid using products that contain silicone or paraffin. These can produce a surface film. A surface film does not allow the concrete to breathe. Concrete soaks up water from the soil. This water passes through the concrete and eventually evaporates. However, if you trap this water at the surface with film forming sealants, you may cause spalling.
For more information on our concrete sealing services, please feel free to contact us at any time. For your added convenience, we have an online appointment scheduling system so you can have one of our owners call or come by on a day and time that works best for you.
We serve the following cities in Arkansas, Fayetteville, Arkansas, Springdale, Arkansas, Rogers, Arkansas, Bentonville, Arkansas, Bella Vista, Arkansas, Eureka Springs, Arkansas, Fort Smith Arkansas, Siloam Springs, Arkansas, (In Missouri) Neosho, Missouri, Joplin, Missouri, Springfield, Missouri, Branson, Missouri, Kansas City, Missouri, (In Oklahoma) Muldrow, Oklahoma, Tulsa, Oklahoma. As long as your concrete project is in Arkansas, Oklahoma or Missouri, we would be honored to work with you.