I often get the question…What do I use to seal the cracks? All concrete cracks due to curing, expansion and contraction and temperature changes. There is no way to prevent it, however there are means to try to control where it cracks. When new concrete is poured, control joints (the lines in the concrete) are either cut or wet formed to encourage concrete to crack in designated areas. Sometimes these control joints do their job and sometimes they they don’t. When they don’t cracks can form across the surface of the concrete instead of inside of the control joint leaving you with an eyesore. Once concrete cracks, regardless of whether or not it is contained in a control joint that crack becomes a permanent moving joint. It is also invitation for moisture intrusion under the existing concrete. This moisture is the number one cause for soil erosion, settling and heaving. It is imperative that the crack be sealed properly to prevent further concrete movement.

There are a few different methods and materials that I recommend that you use. Depending on the type of crack or joint repair determines the method and material which is used. The most common repair is the control joint repair. If a crack has formed inside of a control joint the best and easiest method for repair is to use a flexible concrete calking to seal the joint yet remain flexible to allow the joint to move over time.

I recommend SIKAFLEX Self Leveling Sealant. This particular type of sealant is ideal for cracks that are less than 1/16″ in width. The low viscus, self leveling characteristics of the sealant allow it to be put in place without any tooling. Simply cut the appropriate size off of the tip of the tube, place inside of the caulking gun and lay the appropriate amount of material in the joint and the caulking will level itself. This is considered a high flow material with the consistency of syrup. Make sure there are no openings in the cracks larger than a 1/16″ or the material will run out.

If you do have some areas where the crack is larger than a 1/16″ you need to pre-seal those larger areas with
SIKAFLEX Concrete Repair. This material is much more rigid with no flow characteristics and will stay where you put it. This material is ideal for filling larger crack up to 1/2″ in with as well as vertical application. To pre-seal cracks prior to using SIKAFLEX Self Leveling Sealant place CONCRETE REPAIR as low in the crack as possible, filling all larger cracks and holes, so that once the Crack Repair is cured the Self Leveling Sealant can be place over the Crack Repair material, covering it, without running out.

For joints and crack that are larger than 1/2″ in width, I recommend using an expandable foam like GREAT STUFF Gaps and Cracks Filler. The expansion foam will fill the large gaps and cracks which will create a seal for the Self Leveling Sealant to sit on. Inject the foam deep into the crack. As the foam is expanding and curing it will rise outside of the crack. That’s ok. Let the foam fully cure and then, with your fingers, remove the excess foam just below the top of the crack leaving it as flat as you can to accept the Self Leveling Sealant.

The process for filling surface cracks is the same with one exception. I prefer SIKAFLEX Crack Flex for crack less than 1/8″ in width. This is also a self leveling product, however has a higher viscosity than the Self Leveling Sealant Allowing you to repair the crack in one step. This caulking comes in a smaller and more manageable 10oz. size and has a smaller tip which is easier to maneuver in the surface cracks. Make sure when filling surface cracks that the caulking gets down into the crack and doesn’t just stay on top where it is susceptible to ultra violet.

Make sure to do the repairs on a calm day. You don’t want the dust and dirt to kick up and get in the sealant. Allow 24 hour for these materials to cure before returning the concrete to service. Following these steps will ensure that the cracks and joints in your concrete will remain sealed from further water penetration yet remain flexible to allow the concrete to move over time.


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