Freeze-Thaw Cycles in Concrete
The effects of the freeze-thaw cycle in concrete and how you can prevent them.
The freeze-thaw cycle is one of the main catalysts of erosion. Yes, water and wind impact can also slowly wear down even the toughest rock over millions of years. But one of the fastest and most efficient ways to break stone, rock, asphalt, brick, and concrete, is the freeze-thaw cycle. In fact, water penetration/expansion is the primary cause of concrete and asphalt degradation.
What is this cycle?
The freeze-thaw cycle is something we have covered quite bit, and is the primary reason to get your asphalt seal coated. Basically, what happens is that water gets inside and below the surface of the asphalt. From there it naturally expands and contracts as the weather changes. Normally, this change in water volume damages concrete, but doesn’t totally destroy it. The weather change from night to day, or spring-fall is not too serious. It’s when the water that’s inside concrete starts to freeze that it becomes a serious problem.
When water gets into concrete at all, you are going to have a bad time. It will bleed into small cracks, and then get into smaller and smaller crevices, all the while creating more. Basically, water gets in through a crack system and then extends and deepens that same crack system. Imagine it like a network, or the shape of a spider web.
Once water that’s inside your concrete freezes, then you have an even bigger problem. Freezing water takes up significantly more volume than liquid water, whether the liquid water is hot or cold. This seriously expands the cracks, making existing ones much larger and creating new ones for the water to get deeper inside. Untreated, freezing and melting water can completely destroy concrete or asphalt paving in just a few years.
What to look for
Unfortunately, freezing water may cause internal cracking, which is hard to notice. If you notice cracking that looks like it originated from its interior, or beneath it, then you may have damage from the freeze-thaw cycle. Here is a good guide for identifying various types of concrete cracks.
This happens when chunks break off of the surface of the concrete. It is a problem that gets worse over time, because when the surface breaks off, the aggregate beneath is exposed. The concrete below the surface is not usually sealed against water, so once it is exposed, expect the damage to come in even faster. Spalling can even reveal the rebar/structure at the core of the concrete. If this happens, you may need a replacement if the concrete is structural.
Heaving, often called frost heave, is when the ground below the concrete lifts many inches and the concrete can not move with it. This causes the concrete to lift and break. Frost heave is one of the main ways that concrete is damaged. It’s incredibly difficult to make sure that moisture stays out of the ground below concrete thanks to groundwater and seepage from underground pipes.
The problem may not be due to water though. Tree roots beneath the concrete can cause the same issue.
Preventing freeze-thaw damage to your concrete
One of the best ways to ensure your concrete doesn’t get water in it is the use of deicing chemicals. These chemicals work by lowering the temperature needed by water to freeze. When these chemicals, like sodium chloride (you know, salt), are placed on the concrete surface, they mix with water that falls on that surface. When the water does penetrate the concrete, it is unable to freeze and will (mostly) harmlessly drain out. If you live in a place that gets snow, then keeping all moisture out of your concrete is a lost cause, and you need to adapt to what does get in. Here’s a great list of other deicing mixtures.
Applying a sealer
Just like asphalt, you can apply a sealer to the surface of concrete. A hydrophobic coating will help make the concrete resistant to water penetration. Apply a sealer only after the concrete has fully-cured, and before you use an deicing agent. It also needs to be used before a freeze-thaw cycle has occurred on the concrete, usually in warmer temperatures, so before autumn has set in.
Good construction practices
One of the best ways to ensure your concrete isn’t damaged in the first place is to make sure the construction is done right from the get-go.
Controlling environmental water
Before beginning a paving project, you should make sure that the area is well-irrigated. Gutters, drip edges, and slightly inclined concrete planes help ensure that water drains away from and off of concrete.
This goes for groundwater as well. Before concrete is placed, the earth around it should be well-drained. Earth around concrete should also slope away from it a little to prevent groundwater from flowing toward the concrete. Flashing can also be used to ensure water flows away from the wall structures.
Concrete slabs need to have some wiggle room
No matter your best efforts, water will sometimes get into and under concrete. This will cause expansion and if the concrete has nowhere to expand to, it will break. Make sure that concrete slabs are able to move a little bit with the earth below them. If they can do this, then heaving will cause significantly less fracturing and cracking of concrete than it would otherwise. You can place small barriers between slabs of concrete, using asphalt, wood, or rubber to give your concrete expansion joints. These joints provide some cushion so the concrete can expand without breaking.
Is your concrete damaged?
Do you have freeze-thaw damage on your concrete? Would you like to get it fixed or prevent future damage? If so, you’re at the right place. Reliable Paving, is a large, experienced paving contractor company with the skill and professionalism to get your paving fixed, or done right the first time. Our concrete services include (but are not limited to): repair and sealing. If you want to make sure you can resist the frost, then let us know today, and we can start weatherproofing your concrete.