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| Bond to Concrete |
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One of the most important aspects of floor coatings and toppings, and the least scrutinized is the bond of epoxy to concrete. Manufactures of epoxy coatings and toppings list bond of epoxy to concrete as being between 300-400 psi with an asterisk stating that the concrete fails. It must be understood that this is a test of the concrete and not a test of the epoxy. In order to determine the bond strength of the epoxy one must use a material stronger than the epoxy. Typically two pieces of aluminum bonded with epoxy come apart at 4000 lbs. The weak link in an epoxy-concrete system is the concrete-not the epoxy. Therefore the following pro-active steps should be taken before any system is installed: NEW CONCRETE: Either the general contractor and/or the architect should determine that the new concrete is strong enough(4000-5000 psi compressive strength). It is important that the installer of the concrete does not use too much water during the pour. Flor-tek's system "Ultra-dek" greatly increases the tensile strength of the new concrete and therefore increases the bond of the concrete to the epoxy. We must be contacted before the concrete is poured to insure that the proper additive is used. The cost of the additive to the concrete is minimal. The result is vastly improved bond strength. New concrete should be acid etched or sanded to remove the latenance on the surface. The concrete should be cured for 28 days before epoxy is applied. OLD CONCRETE: The best preparation for old concrete is "shot blasting". "Shot blasting" can remove old coatings and dirt. The downside of "shot blasting" is that it can leave lines on the floor , which if deep enough, could later telescope through the finished epoxy. The next best method is a combination of acid etching, sanding, and the use of solvents to remove oils and grease. POWDERY CONCRETE: If continual sweeping renders continous dust, then the concrete is too soft for any bond. There are varying degrees of weakness with powdery concrete. Slightly powdery concrete may require annual recoating Very weak concrete should be removed. |