Sealer Issues

Issues with dull,worn or milky sealed surfaces

 

As discussed in the FAQ section of our website, solvent-based sealers are used to protect and enhance the look of plain and decorative finished concrete areas. Whether it's a water-based sealer or solvent-based sealer, the finish is a thin film of acrylic polymer which has bonded together to form a seal of the treated area. The process is described in our FAQ. 

 

Over time, acrylic sealers may become dull or cloudy. Normal weathering events, traffic or chemicals (from washing the car!) may cause the sealer to exhibit signs of wear, and some may believe that the sealer has gone! The problem isn't that the sealer has gone, it's that it has worn to the point where it is no longer transparent. The time that sealers take to become dull or cloudy looking is dependant on the circumstances under which the sealed area is used... High traffic areas in Industrial complexes may show the tell-tale signs of wear quickly, whilst low-traffic areas may last for many years without exhibiting any signs of wear.

 

Another issue is a cloudy sealed finish, where moisture has become trapped beneath the sealer and the sealer turns 'milky' in appearance (also known as blushing). Despite having sealed the concrete perfectly, during the driest conditions, you notice some milky or cloudy patches occuring in random spots. What could possibly have happened?

 

Although it was dry and the sealer was applied as directed and allowed to cure fully and looked perfect for a while; rainwater runoff, ground-water or control joints may have allowed water to flow underneath the concrete slab. Concrete, being a porous substance, has literally soaked up this underground water (this process is called wicking) and through evaporation, is attempting to expel it, through the sealer on top. The result is that the moisture causes the sealer to become cloudy or milky looking.

 

'Whitening' is a problem that may occur several days after concrete has been sealed. It is characterized by an excellent quality finish immediately following the application of a sealer, followed by the appearance of frosted or whitened areas several days later.

Concrete is a very porous material and there is always water vapor passing upward through concrete, drawn upwards by the warmth of the sun. As a result, whitening is generally most pronounced in areas of greatest sun exposure and less evident in shaded areas.

Acrylic sealers are designed to “breathe”,which allows water vapor to pass through but prevents liquid water from being absorbed back into the concrete. If a sealer is applied too heavily or frequently, that breathability is compromised allowing water vapor to condense beneath the sealer, causing it to delaminate from the concrete surface. The delaminated areas appear white.

 

'Blushing' is a milky appearance within the sealer itself. Blushing of water-based sealers is either moisture trapped within the sealer as it cures, or the film hasn't cured correctly. Film formation (especially of water-based products) is inhibited by low temperatures (air and/or substrate temperatures below 10°C) and high humidity that slows evaporation.