Let it Snow: Are Your Sidewalks Ready for Winter?POSTED 12.05.18
It’s not a trick question. Concrete sidewalks – and driveways – need to be protected from winter ice and snow if you want them to last.
As this map of average winter temperatures by state shows, about half of the United States experiences temperatures at or below freezing. While we might think of concrete is impervious to cold weather – if we think of it at all – the truth is that your sidewalks and driveways can be harmed by snow and ice.
Strong, but not really…
The ancient Romans are responsible for developing concrete as a material for building. Their version was made of lime, water, and volcanic ash. Fast forward to the turn of the century, when lightbulb inventor Thomas Edison applied for and received 49 patents related to concrete. This rock-hard substance has had in interesting ride throughout history, and it’s estimated that nearly 6 billion cubic meters of concrete is used in building each year – that’s about a cubit meter for each of us!
Reinforced concrete is one of the only building materials resistant to both fire and water. Concrete’s slow rate of thermal conductivity make it an effective heat shield. When submerged, concrete outperforms both wood and steel, and it has super-high compressive strength.
Even so, concrete has an Achille’s heel.
Ice, ice, baby
If you re-read what you’ve learned so far, you’ll notice something important. Concrete is water resistant – not waterproof. Unprotected concrete surfaces can pull in moisture. During the winter, snow and ice will make its way into cracks in your concrete sidewalks or driveway. Fluctuations in temperature will melt the frozen water, allowing it to saturate the concrete substrate.
When the temperature falls again, the water will refreeze – and ice expands. The density of a water molecule decreases by about 9%. It makes an ice cube float, but the same process is what cracks boulders in nature – or your sidewalk. Saturated concrete expands, which causes what’s known as spalling. The result is cracking.
Careful with the salt
Too much on your food will ruin the taste, as well as your health. Too much salt for winter de-icing is also bad for your sidewalks and driveways. In general, using salt for snow and ice removal adds to the destructive forces of refreezing water on concrete that hasn’t been waterproofed.
The correct amount of salt as a de-icer can help properly treated concrete sidewalks and driveways, but the benefit usually stops there. More salt is not better – for your concrete or for the environment. According to the City of Orono, Minnesota and the Minnehaha Creek Watershed District in Deephaven, as little as a teaspoon of salt can permanently pollute five gallons of water.
You probably need far less de-icing salt than you think. The Minnehaha Creek Watershed District shares that the proper amount is about four pounds of salt for a 1,000 square foot area. That’s only about four scoops of ice using your favorite coffee mug.
Before the snow
Cracks in concrete sidewalks or driveways should be repaired, and their surfaces should be protected before the winter snows arrive. Concrete itself isn’t waterproof, but it is possible to repair and treat it with special coatings that can make it waterproof.
Many homeowners have concrete patios, garden walkways, and even main entrances that are made of concrete. Concrete last longer and looks better when it’s waterproofed. Today’s treatment processes can waterproof and strengthen concrete up to eight inches deep. It can increase compressive strength up to 23% and keep mother nature from doing damage during the winter months.