Concrete Safe Salt
Once your new concrete parking lot or driveway has been properly placed, finished, cured and sealed, you’re done, right? Not quite.
If you’re in a northerly climate, you have to deal with snow and ice accumulation and you might be left wondering the best way to clear them off of your concrete parking lot. If you want to get the most out of your concrete, it's not as simple as throwing some salt down. Take a look at the dos and don'ts of concrete salt and winter care.
The First Year: No Chemicals
First things first, keep the pavement clear of snow and ice and for the first year after construction is complete.
In the first year, it is recommended that no deicer of any type be utilized before the concrete has been allowed to thoroughly dry out. Instead of a deicer, we recommend using sand for slip resistance and traction during the first year of service. New concrete that was properly air entrained to resist the effects of freeze-thaw cycling during the winter months may still exhibit surface scaling if a chemical deicer is applied too soon after construction.
This happens because the microscopic air voids purposely developed within the concrete are still partially full of water at an early age and cannot provide the “pressure relief system” for the increase in volume that occurs when water freezes within the pore structure.
Similarly, deicing chemicals also raise the core pressure within the concrete and if applied early on can also cause scaling distress. Scaling is the loss of surface mortar from the finished surface of the hardened concrete, typically the result of freeze-thaw cycling. Scaling in severe cases can exceed a depth of 3/8”.
After the First Year: Common Rock Salt
After the first year of service, light to moderate applications of deicing chemicals may be applied to the pavement as needed.
We recommend using common rock salt (sodium chloride – NaCl), (the same as table salt) in lieu of other deicing salts such as calcium chloride or magnesium chloride.
Sodium chloride is effective to a temperature of approximately 18 degrees Fahrenheit. The other salts noted above are effective at lower temperatures than sodium chloride and are often sold with “Hot" or "Heat” on the packaging, however they are also much more aggressive towards the concrete physically and chemically.
The Stress of Deicers
All deicing salts can cause distress in the concrete over time, but the effects of sodium chloride are much less severe than other salts. In addition, sodium chloride also has a significant economic advantage over calcium chloride or magnesium chloride in the Michigan market.
One last case for the use of sodium chloride as a deicer over the other chloride-based chemicals is the relatively recently observed calcium oxychloride joint deterioration in concrete pavements. The transverse and longitudinal joints within the pavement progressively deteriorate and widen significantly with time as a result of saturation of the concrete at the joint and the increased use of calcium chloride and magnesium chloride.
Deicer laden water gets trapped within the concrete joint and once a high enough level of saturation is reached, the concrete begins to significantly deteriorate. The reaction that causes the joint distress can occur at temperatures above freezing, making this phenomenon more challenging. The rate at which the deicer containing water enters the joint can be hastened when brines of either calcium chloride or magnesium chloride are used as a pavement pretreatment.
Test Your Salt
If you are unsure which product is being used as a deicer on your pavement, one easy way to check is to see if the pavement still appears damp or wet on a relatively warm (for winter) day. If that is the case, it is very likely that calcium or magnesium chloride has been applied. Compounds containing sulfates and nitrates commonly used in fertilizing products should never be used as concrete deicers because of their very aggressive interactions with the concrete.
So, if you have a concrete lot or driveway in a cooler climate, be sure to keep it clear of snowfall and, if necessary, use sodium chloride (rock/table salt) as little as possible to keep your concrete in tip-top shape. If you keep your concrete driveway clean and clear, it can stay nice for decades. Want to learn more about concrete and paved driveways and how you can experience the benefits of a concrete surface? Download our Concrete Care and Maintenance Brochure below or check out our page about concrete roads, driveways, and parking lots.