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With Fast-track construction there are more moisture issues than ever before.  The failures are caused not only from Fast-track construction, but from improper moisture testing, lack of moisture retarders and just plain negligence.  I have encountered many situations where the moisture levels are in the high ninety percent range, and the solution is to use a premium mitigation system.  While there are only a few premium coatings on the market these require a lot of attention to detail and in most cases an applicator that is trained by the moisture mitigation coating manufacturer.

In some cases the manufacturer will require a specified number of tests to be run to rule out problems that might cause a future failure.  These can be tests for Alkali Silica Reaction (ASR), which is the most common, or other similar conditions.

Photo 1 – Shot blasting: The most common mistake is not cleaning the concrete well enough.  The best way is to shot blast the surface of the concrete.  The degree of shot blasting is determined by whatever was on the concrete prior to the shot blasting.  But it is necessary to completely remove all traces of adhesive and open up the pores of the concrete.  Sometimes this will require the concrete to be abraded to a Concrete Surface Profile (CSP) of CSP4 and in some severe cases where a penetrant-type mitigation treatment was used, a CSP5.

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Photo 2 – Treatment of cracks and control joints: After the shot blasting it is necessary to take care of all cracks and dormant control joints.  These must be filled with epoxy joint filler, which in some cases are mixed with sand to help bridge the gap.  Most cracks must be chased with a diamond cutting tool to open up the crack to allow proper penetration of the epoxy filler.  Any joints that are active must be honored.

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Photo 3 – Primer coat: Once all of the cracks and joints are taken care of it will be necessary to thoroughly vacuum the concrete surface to remove all foreign matter and fine dust.  Once completed it is necessary to prime the surface of the concrete to ensure a good mechanical bond of the moisture control coating to the concrete.

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Photo 4 – First coat: After the primer has dried it is time to mix the coating for the first coat.  The mixing is done with the used of a power mixer after the two components are combined.  When the power mixing is complete it will be necessary to pour out some continuous puddles of the coating about 6 – 8 inches wide.  Wet out a medium nap paint roller with the coating and apply the first coat coating thoroughly to the surface of the concrete.

Photo 5 – Broadcasting sand into first coat: With this treatment the manufacturer recommends a layer of sand to be broadcast into the wet coating.  This layer of sand is to enhance the bond of the second coat which will be applied after this coat has dried.

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Photo 6 – Second Coat: After the first coat has dried it will be necessary to thoroughly sweep and then vacuum the entire area to get up all of the loose sand.  Keep the sand clean in a clean container so it can be used after the next coat. Once cleaned up it is necessary to mix and apply the second coat, just like the first.  The reason for the second coat is to totally coat the concrete.  The first coat may have pinholes that will not control the moisture and allow for the start of a potential problem.  Also note, the coating is a different color.  This is to prevent areas that might be missed.  Care must be taken not to damage the first coat when working over it.

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Photo 7 – Broadcasting sand into second coat: Immediately after application of the second coat it will be necessary to broadcast sand just like you did after the first coat.  This will ensure a good bond of the self-leveling underlayment that will be applied after this coat has dried.

Moisture is a major problem to our industry and the costs of mitigation are expensive.  In severe cases of high moisture, it is necessary to follow every infinite detail so that once completed there will be no problems.