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Expansion joints are an important part of any concrete walkway or driveway. These joints allow concrete walkways to expand and contract without putting stress on the concrete. Expansion joints prevent concrete cracks and damage that can cause your concrete slabs to deteriorate with time. Without expansion joints, concrete slabs can heave or crack, which lead to repair or even replacement of your concrete slabs.
Concrete expansion joints can be a point of vulnerability in your concrete slab if they're not properly filled. Expansion joints need to be filled with flexible material that can expand and contract with the concrete.
In this article, we'll discuss best practices for filling concrete expansion joints. We'll also answer the question: what is an expansion joint?
Knowing how to fill your expansion joints and why can help you ensure a long service life for your concrete projects. Whether you're a professional or a DIYer, here's what you need to know.
An expansion joint is a small gap in a concrete slab that allows the concrete to expand and contract. Expansion joints can be cut into a large concrete slab like a driveway, or expansion joints can take the form of a gap between your concrete and another slab or structure. Expansion joints are the cracks in the sidewalk that you see in front of your house. Expansion joints are also the gap between the concrete stairs leading up to the house and the house itself.
Expansion joints are necessary any time you're creating a large concrete slab, or any time you're installing a concrete slab next to another structure. For example, you may install a concrete driveway against a concrete path. In this case, there should be an expansion joint between the two structures (and in the structures themselves).
Expansion joints need to be filled because joints create avenues for concrete damage to occur. For example, expansion joints can lead to areas of runoff that cause the erosion of the soil around the concrete slab. Over time, this can cause the slab to heave or dip.
Expansion joints also create areas where water can pool and then freeze during freeze/thaw cycles. Water that freezes can expand and cause cracks in the slab.
Expansion joints even create small cracks where weeds can grow, leading to more cracks and more damage from water that pools under the slab.
Filling expansion joints can prevent all of these problems, thus lengthening the service life of the slab.
Expansion joint foam is a common material that is used to fill expansion gaps. Expansion joint foam comes in many sizes, including:
The size of the expansion joint foam that you choose to use for your concrete projects depends on the size of the expansion joints.
Sealants and fillers that are used to fill expansion joints must be flexible enough to move with the concrete. Caulk is the go-to filler for most expansion joints. Caulk comes in self-leveling and non-sag versions. Self-leveling caulk is thin and will sink into the expansion joint so that it does not need to be leveled by hand. Non-sag caulk is thicker and will need to be leveled off.
Expansion joint foam is an expanding foam that contracts and grows with the size of the joint. It is used with sealant to help fill the space between two slabs or the space at the bottom of the joint. As the concrete contracts or dries, the foam fills the gap and flexes to fill the joint space.
Following best practices for filling expansion joints can help you maintain your concrete.
Use a screwdriver or another pointed tool to remove any debris from the expansion joint before filling it.
Check the temperature of the concrete before installing sealant, and avoid installing sealant when the concrete is too hot or cold.
Fill any void at the bottom of the expansion joint with sand.
Place the expansion joint foam over the sand to create a durable surface where sealant can sit.
Use the caulk gun to install sealant over the expansion joint foam.
Wait a few minutes, then sprinkle sand over the sealant to disguise the sealant and help it blend in with the concrete.
Do not use mortar or a non-flexible material to fill expansion joints. Mortar will crack with time. Mortar is also porous and can allow water to slowly flow into the space beneath your concrete slab.
Maintaining expansion joints is relatively easy. Get rid of any weeds, moss, and grit in your expansion joints. You can clean expansion joints periodically with a jet of water from a hose. Sealant will start to deteriorate over time, so maintaining sealant and replacing it as needed can help extend the life of your concrete.
Most important of all is to remember that expansion joints that are not filled can be compromised by ice, rain, and weeds. This leads to cosmetic problems as well as cracks in the concrete. As time goes on, these cracks can become bigger and more damaging. Cracks become their own kind of expansion joint, and as they get bigger, they can lead to concrete heaving and more cracking. Fill your concrete expansion joints to prevent this from happening.
Discount Contractor Supply is your go-to resource for concrete finishing tools. It takes the right kind of tools to ensure that your concrete projects are done right. To learn more about our tools or how we can help with your concrete projects, contact us.
