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Question posted - August 14 to August 18, 2017:

How do you keep sealants in control joints from cracking or separating from the substrate?

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Selected Answers

From David King of Modern Maintenance Products NZ Ltd on August 16, 2017:
We coat a lot of swimming pools with an immersion epoxy, and when control joints require replacing, as they have become unstuck from the concrete substrate, we clean or re-cut the joints, and apply the epoxy to the sides of the concrete joints. When the epoxy has cured, we apply the control joint sealant and have found its adhesion to the epoxy coating outstanding. This is because the epoxy is non-porous and maintains a substrate that remains dry, as a damp concrete surface is what causes the sealant to become unstuck in the first place.

From Brian E Bennett of Bennett Construction & Enterprises, LLC on August 14, 2017:
Correct. First, you must chose the right sealant  for the job and properly prep the substrate. This should minimize any cracking or separation. Everything begins with proper prepping and following the directions  for application.

From Zenith Czora of Zen Consultancy on August 14, 2017:
For sealants to perform as intended, the following factors need to be considered to allow successful performance: 1. proper joint design, surface preparation, sealant application method and type of suitable sealant. Sealant for exterior applicaction must always have a minimum of 6 mm of contact or bond surface to ensure adequate adhesion. Sealant depth over the backer rod should be a minimum of 6 mm. Sealant joint width should always be a minimum of 6 mm to allow proper surface preparation and joint filling. Greater joint widths may be required depending on joint movement. Selection of sealant depends on its application and the type of substrates. Sealants should have  very good elastic properties capable of withstanding any building movement,  excellent adhesion,durability and excellent weathering resistance. Surface should be very dry and clean free of dust, grease and loose materials. For porous substrates, a suitable primer could be applied. Use  backing material to achieve the correct joint dimension and to prevent 3-point adhesion that will lead to cracking. Using a release bond breaker tape will also keep the joint sealant from cracking. Sealants manufacturers normally supply a manual on how to use their sealants. It is a best practice to determine first which sealant and application are best suited for the requirements.

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Tagged categories: Sealant

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