At a recent trade show in Dubai, I was surprised to hear from a lot of different visitors (from different countries) complaining to me that epoxy screeds form too many bubbles on the surface. What they meant was that when the screed cures the bubbles leave an ugly looking surface with little holes that is very prone to dirt pick up.
I was surprised that there’s still a lack of knowledge regarding the cause of these bubbles. I am planning a series of articles to help explain from my point of view what causes bubbles and what we can do to avoid them. Bubbles can be attributed to a number of reasons:
1. Problems with the substrate. Usually caused when the substrate Advantages Of Industrial Development is absorbent which leads to air being released
2. Poor application techniques. Most problem associated with bubbles are related to something going wrong during the installation
3. Problems with the actual product. A problem that is growing in importance as many low-cost companies are emerging with questionable product quality
Lets look at each problem separately:
1. When applying epoxy screeds on a porous substrate it’s very important that it has been properly primed and sealed. Bubbles emerge when the substrate is of cheap and porous quality. This is often the case with cement or concrete substrates where the composition of the mortar is not according to standard (for example using an excessive amount of sand or water). The substrate ends up absorbing part of the screed which in turns leads to air being released inside the screed that will lead to holes and huge ugly craters. Often these holes don’t emerge straight away but an hour or two after application.
The solution to poor substrates is to properly seal the floor with several layers of epoxy primer until the surface has achieved a glassy texture. Cost-permitting it is always advisable to apply additional layers on top of the primed surface (whether it’s a simple coating or a screed) before you apply the final coating. A well-sealed and primed surface goes a long way to assuring great results. But what is even more important is to have a decent substrate to begin with.
2. Problems during installation can be attributed to a number of reasons:
When mixing the components that make up the screed (resin, hardener, sand) it’s important to mix at a low revolution. Mixing at high speeds may lead to the material foaming and thus an excessive amount of bubbles emerging. It is advisable to use a mixer with adjustable revolution speed and never exceed 300 rpm. Some installation teams in their hurry to finish quickly, prefer to mix for a short period of time at high speeds. Also after mixing the screed, let the new screed “rest” for 2-3 minutes before applying it.
Most importantly however is what happens when the actual epoxy screed is applied. The use of a spiked roller is essential to properly level and release any trapped air …
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