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Spring Concrete Care
March 29, 2021
It's March in Minnesota, which means snow is melting, mud is everywhere, and our concrete has winter residue all over it. We at ConCreative Accents want to help you keep concrete performing well and looking great. Here are a few things you should know about concrete during the spring.
CRACKING and HEAVING-
You might have noticed that your concrete driveway, sidewalk, or patio may be sitting a little higher than it was last fall. This is due to frost heaving. During the winter as the moisture in the ground freezes, it causes the ground to expand and lift up, causing your concrete to now be at a new height. You should have nothing to worry about...if the base and expansion were installed correctly, as the temps warm and the frost starts to melt, your concrete should drop back down to its original location. Frost heaving can sometimes cause new cracks, even if your concrete is 20+ years old. If part of your concrete gets caught on something and doesn't allow it to move evenly, could result in a crack. If the ground was more saturated with water than other years past before winter, could cause the ground to freeze more and cause new cracks. Snow melting and not having proper drainage can cause water to get under the concrete. Then at night when it freezes again, can cause expanding and a crack to appear. If your concrete has the correct reinforcement placed in it, will help hold the concrete together and not allow the cracks to enlarge.
Salt and deicers are some of most damaging item’s concrete can see. Here is a little knowledge about concrete and salt; Although concrete sidewalks and driveways look very solid, concrete is actually a porous material that can and does absorb water. In cold weather the snow or ice is a solid and does not penetrate into concrete. But, when ice milters are applied to snow or ice, the melting ice/snow is turned into a salt/water mix and is absorbed by concrete.
Additionally, salt is hydroscopic, which means that salt actually attracts more water to it. So, when ice is melted by salt and changes into a salt/water mix, it enters the concrete with approximately 10% more water than would normally enter concrete. When temperatures fall below freezing (32 degrees), having this extra water in concrete causes a large problem. In these colder temperatures, the extra water in the salt/water mix starts to re-freeze and expand, but the additional water adds additional ice in the concrete, which in turn adds additional hydraulic pressure on the concrete.
When the hydraulic pressures of the re-freezing water exceeds the compression strength of the concrete, damage can occur. Additionally, the more often the freeze/thaw cycle happens, the more likely the damage is to occur. This being said, a one-time use of rock salt is unlikely to cause damage.
WHAT DAMAGE LOOKS LIKE:
The freezing water inside the concrete creates so much upward pressure on the concrete, that the smooth, non-aggregate top of concrete can "pit" or spall. This damage can be in large sections or in scattered smaller spots. When the smooth finished texture of the concrete is gone, these damaged spots show the aggregate mixture of the concrete that is below.
WHAT TO DO TO REMEDY and MAINTAIN CONCRETE
Good news is, these issues can be repaired by yourselves or by hiring a knowledge concrete company.
Small cracks or holes less thank ¼” wide generally don’t pose a structural threat and can be filled or patch as a temporary fix. Fillers and patches are visibly different than the concrete they are applied to. If there are a lot of areas to fix, this can result in a unappealing blotchy overall look, so that is something to be considered. Also, patches aren’t water tight, meaning that eventually, water will seep between the patch and original concrete, reopening the crack or hole. Filling a few small cracks or holes can be relatively easy DIY project done with materials purchased at your local hardware store.
Large cracks or holes greater than ¼”, spalling (horizontal peeling or chipping of the surface), and discoloration can be covered with resurfacing or a concrete overlay (a think layer of cement-based material applied directly over existing concrete).
Resurfacing allows you to add decorative finishes such as stamping or coloring. Your driveway, sidewalk, patio, or steps will look like new with out the added work and expense of removing it and installing a new one. A middle ground between patching and replacing, refinishing with an overlay provides a longer lasting and more aesthetic repair than patching.
The best way to repair salt damage concrete is to grind the concrete surface. This will remove all the weak and damaged concrete, followed by a good cleaning. Preferably with a concrete detergent (NOT muriatic acid, another damaging item to concrete) and pressure washer. Once the concrete has dried for 24 hours and concrete resurfacing material can be applied (a bonding primer should be used prior to installing the overlay). Concrete resurfacing is a polymer modified concrete top coat (overlay) that allows you to put a new surface on your existing concrete. The new overlay and be standard grey broom finish, colored, and patterned or stamped. Finish by applying a sealer (ask Doug what is the best sealer for grey overlay). Or an acrylic sealer for a decorative finished overlay. If only certain sections of the concrete are being resurfaced and your left with a mismatch color, a tinted sealer can be applied to even the color out.
CONCRETE HAS NO DAMAGE-
If your concrete made it through the winter salt damage and crack free. Then a thorough cleaning is the best thing to do. This will clean all the salt residue, dirt, and other grim away. Leaving you with fresh clean concrete ready to be enjoyed this summer. If your concrete hasn’t been sealed in 3 or more years, we recommend resealing it. Best places to get the correct sealer if you choose to do the work yourself is through your contractor and a concrete supply company. We do not recommend the sealers from places like Home Depot, Menards, Lowes and so on. If you feel resealing concrete is something you can’t do or simply don’t want to do, call your contractor. Most of them offer reseals.