Whitening of Concrete Sealers – also known as ”Blushing”
This is a frustrating and growing problem in the architectural concrete Industry. There are many reasons why this happens and Drycrete Moisture Stop offers a tangible solution pertaining to whitening of topical sealers, also known as blushing.
Blushing of topically applied sealers is directly associated with applying sealers over moisture laden, freshly placed concrete. Sealing within a couple of days from placement and finishing can almost guarantee that you will have problems. The same is true of any topical coatings, as no one applies such coatings over wet surfaces.
Application related failures include:
- Sealing the concrete within 1-3 days of placement.
- Sealing concrete after pressure washing on the same day.
- Efflorescence created under the topical sealer from moisture vapor emissions due to the lack of vapor barriers and/or insufficient aggregate base.
- Applying to many thick coats of sealer, in fact created an unbreathable barrier.
- Too many coats and/or incompatible sealers
- Sealing too frequently with excessive buildup can also entrap moisture, as the topical sealer becomes far less breathable and unable to dissipate a controlled rate of evaporation.
Environmental related failures include:
- The installation of new sod and sprinklers at the perimeter of a given concrete slab.
- Improper drainage and runoff, resulting in stagnant water puddles and excessive ground moisture.
- High water table, resulting in excessive ground water evaporation through the concrete slab.
Trapped moisture shows up as a whitish discoloration as water is trapped between the surface of the concrete and the topical sealer. The head from the daily sun causes accelerated evaporation and the moisture is trapped. Concrete needs to breathe, and a topical concrete sealer must be “breathable”. Allowing ground water and surface water to freely evaporate or to be stopped integrally by making the entire concrete mass a vapor barrier is the solution to blushing.
How do you fix this, after discovering the problem?
- Strip the existing sealer: This is both labor intensive and requires controlled cleanup.The resulting costs are often a sore point, and if you re-apply the sealer without fixing the cause, there is a good chance that blushing will re-occur.
- Wet sandblasting – This is fast and cost effective due to a simple cleanup. However, it requires high psi pressure washers with a special wand attachment to induce sand into the water at a controlled rate for topical sealer removal without damaging the concrete surface. CAUTION: This needs to be done by a wet sandblasting professional that has ample experience in the use and application of this removal process. The re-application of the sealer needs to be done in very thin coats, to avoid repeating the problem of future blushing – but again, without fixing the root of the problem, this can re-occur.
- Specially blended slow dissipating solvent blends are also used to re-emulsify the sealer, and release trapped moisture underneath to remove the blushing.
The problem with the solutions above, is that they do not address the core problem of blushing – excess moisture within the concrete.
DRYCRETE treats the concrete from within, resulting in a decrease in permeability of >90%, thereby controlling the rate of evaporation to a much lower level, and therefore controllable to remain within the limitations of the breathability of the topical sealer, even if over applied.
It is best to apply DRYCRETE at the time of placement, as a curing compound. On decorative stamped concrete, it is best to apply after the antiquing agent has been properly washed off, and all water puddles have dissipated. DRYCRETE can be applied to moist/wet concrete, as long as there is no standing water puddles – which in facts aids the penetration and reactivity of DRYCRETE deep within the concrete matrix.