The Reason You Should Never Spread Rock Salt on Concrete Driveways



It might be tempting to use rock salt on a slick, icy driveway, but resist the temptation. Salt and de-icers work not by melting ice, but by lowering the freezing point of water, which is 32ยบ F. If you’ve used a de-icer with no apparent effect, it’s because it was simply too cold and remained below the chemical’s freezing point. As temperatures fluctuate, water goes through a freeze/thaw cycle. Water seeps into concrete, which is porous, and when it freezes it expands, causing damage to concrete driveways. Asphalt driveways are far less susceptible to salt damage, as their aggregate of stones, sand, and petroleum is meant to withstand these freeze/thaw cycles. Rock salt may be the worst offender of this type, because it attracts about 10% more water than would otherwise enter the concrete. So what should you opt for instead? Calcium chloride is your best bet, but don’t use too much, as runoff can seep into lawns and kill grass and flowers.