subject: Concrete Expansion Joints [print this page] As the temperature changes, concrete contracts and expands and space needs to be left between the slabs to allow for this expansion. A concrete expansion joint has been described as that space that allows the slabs to expand during the curing stage of the concrete. They help prevent cracking in the concrete as the material that is below it settles.
There is more than one way of installing expansion joints especially on sidewalks, patios and driveways. This can be done when it is wet which is usually much easier than when it is dry. There are some special tools that are needed for the installation of a concrete expansion joint when the concrete is still wet. If the area covered by the concrete is large, one should section it into portions that are equal. A line of chalk should be drawn on the concrete after it has been allowed to settle for more than half an hour. This gives a point of reference when cutting out the joint. The tool that is being used can be bought from the stores that sell tools for finishing concrete.
With a saw that will cut through concrete, one can install the concrete expansion joint in dry concrete. This saw can be rented from a store or installed by putting a concrete blade on a saw with the circular shape. As in the wet method a line of chalk needs to be drawn to act as a guide. So the dust does not become a bother, water needs to be poured on the concrete and joints that are cut through the concrete. The deeper the cut in the concrete, the better.
Either by mistake or after some time, these expansion joints may begin to fall apart. This should not worry you much as they can be repaired or replaced with a sealer meant for joints. This helps prevent further damage to the concrete or the other structures involved. The first step is to remove the debris or dirt from the expansion joints. A putty knife can be used to remove the elastic sealer that may have been applied previously. Gouges or cracks could be sealed with patch and mortar repair. Before continuing with the repairs, one needs to let this settle for 24 hours.
A pipe cell insulation needs to be put in the joint which will hinder water from flowing in between the slabs. The edges of the joint need to be masked so as to have an edge that is uniform for the sealer. The sealer is then applied to fill the joint though it should still be flexible to contract and expand with each temperature change. Instructions of the manufacturer need to be followed to the letter when allowing it to set. It is important that when doing these repairs to do them when the temperatures are moderate as this will give a balance between contraction and expansion. If confused there are plenty of concrete experts available to assist.
