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Understanding the five most common sealer problems

To be forewarned is to be forearmed. Therefore, understanding some of the basics with concrete sealers and the problems you are most likely to face, will save you a world of pain and heartache. Having this knowledge will empower you to make the right decisions before you get an irreversible problem.

Concrete sealer problems can be a source of frustration for DIY homeowners and concrete contractors if you don’t understand the symptoms. Often we don’t know what the root cause and knowing about common sealer problems will help you.

When you think that a concrete sealer is not looking right or performing as expected, the cause can usually be traced back to one of three problems:

  • Over-application
  • Application in non-ideal conditions or,
  • A buildup of multiple coats

We have distilled the most common sealer issues that people may face, why they happen, and how to avoid them in the sections below.

Problem #1: The sealer bubbled

The presence of bubbles in the sealer is usually caused by a heavy application. Outgassing from the concrete surface during sealer application should be free to quickly move through a thin, wet sealer film.

What is considered thin? At a typical coverage rate of 27m2 per 3.7L, one coat of an acrylic concrete sealer should be about 5 mils thick when wet. When dry, the sealer is only about 2 mils thick.

When the sealer is applied too heavily, the air displaced through the surface can’t escape, and it forms a bubble in the sealer surface.

The bubbling of a sealer can also occur if the application is done in hot weather, or if the concrete is in direct sun. In these conditions, the sealer will “skin over” and dry on the surface before all of the solvents have evaporated.

The pressure of the solvent trying to evaporate will form a bubble in the sealer surface. It’s best to apply sealers during the coolest part of the day when concrete is not in direct sun.

Problem #2: The solvent-based sealer turned white, is peeling or flaking

There are two key contributors to “blushing”, or whitening of a solvent-based concrete sealer.

The first is the application to a concrete surface that is wet, or to fresh concrete that still contains bleed water. When this occurs, the sealer will not bond to the concrete surface but will instead float on a trapped film of water.

The second cause of sealer blushing is applying it too thick. Heavy coats of sealer or a buildup of sealer applied numerous times over the years, will cause moisture to become trapped under the sealer and, in time, the sealer loses adhesion from the concrete.

When this occurs, the trapped moisture and air under the debonded sealer has a refractive index such that the sealer appears white to the human eye. In time, the sealer will peel or flake off the surface.

To avoid this problem, carefully follow the manufacturer’s recommendations regarding the coverage rate and the number of recommended coats.

Problem #3: Water-based sealer is white or powdery

It is important to note that the drying process of water-based sealers is quite complicated and significantly affected by the temperature and humidity of the environment during application.

Water-based acrylic sealers dry by a process called coalescence in which the water and then the coalescing solvent evaporates and fuse together the acrylic particles to form the sealer film.

If the temperature during application is too low (less than 10 degrees) or humidity is too high (above 32 degrees), the coalescing solvent will evaporate before the water does and the sealer will dry white or powdery because the latex particles did not fuse together before drying. 

Therefore, we suggest always find out what temperature and humidity conditions will be and that are required for successful application of a water-based sealer and work as close to these guidelines as possible.

In colder climates, like Melbourne, it’s best to apply the sealer as early in the day as possible to allow for the coalescence process to take place, this can be helped by using a broom or an Oates 61cm Nylon Polish Spreader from www.cleaningshop.com.au.

This helps to break up the surface tension and aids in the process of the concrete absorbing the sealer. You also need to make sure that there are no white patches left as that would cause a problem, thus working the sealer into the concrete with a broom helps.

If the product is left to work for most of the day, and there are no white patches, before the dew sets in at night, you should be ok.

Working with any water-based acrylic sealers in cold climates is problematic but following these guidelines and using a good system, or process and common sense will help to minimize this risk.

In terms of the B883 Stain Resist Sealer and the G887 Stain Protect Sealer we sell, both can be used on green concrete and used as a curing aid. We suggest using a 1:3 ratio as soon as the concrete is dry enough to walk on.

Problem #4: The sealer is stained from oil, leaves, tires etc

The most common concrete sealers are manufactured with acrylic polymers that do not provide exceptional chemical or stain resistance to the concrete.

For more durability and resistance to chemicals and staining, consider an epoxy or urethane coating system, and ensure that the coating is appropriate for exterior use before applying to outdoor concrete.

Problem #5: The concrete is dark and/or blotchy after the sealer is applied

Most solvent-based acrylic sealers will darken concrete and leave a glossy shine to some extent, giving the concrete a “wet look”.

However, because every slab is unique in its colour and texture, the colour of the concrete after the sealer has been applied is difficult to predict.

The mix design, use of chemical admixtures, finishing techniques and porosity are just a few factors that will affect the concrete surface colour.

A sealer will deepen the true colour of concrete and will highlight all the differences in the surface texture that result from floating and finishing.

Sealers also bring out the “grain” in concrete just like a varnish does on wood. If changing the concrete colour after sealing is a concern, use a penetrating water repellent sealer or, even better, we highly recommend doing a small test application of a film-forming sealer to make sure the colour change will be acceptable.

Lastly, if you want us to help you through the process of selecting the right sealer or want us to apply it for you, please contact us today, we are here to help you get the look you want.