In the construction of new buildings, it is common practice to apply floor coverings directly to concrete floor slabs.
Unfortunately, floor failures due to excess moisture in concrete are a common occurrence. This is largely due to the impact of tight construction schedules.
Excess moisture within the concrete beneath floor coverings can have other negative effects as well, creating a haven for mould and bacteria, with the resulting odours and impact to occupants’ health.
Let’s talk about floor slabs
Concrete is about the most commonly used building material on the planet, due to its comparatively low cost, innate strength, and versatility of application. Its use for floor slabs is as ancient as the Romans. Direct-stick flooring is of course much more recent, a common and very practical compromise between budget and durability.
When a slab is poured, it must cure over a certain period before floor coverings can be applied. The process of curing involves the evaporation of much of the internal moisture. Usually about 28 days from pour is allowed for this purpose.
Importantly, ‘curing’ is not the same as ‘drying’.
In fact, a concrete slab dries at the rate of about 25mm thickness per month. This means that after a period of 28 days, slightly less than 25mm will have dried, and the internal moisture levels may still be high. A 125mm thick slab may take 5 months to dry to RH of 75% or less.
It’s not just about the curing!
As long as the slab is exposed to rain and external moisture sources, it will not be properly drying.
Effectively, the drying process should be calculated from the date the slab is protected from the weather (weathertight).
For these reasons, the time until the safe application of floor coverings is often underestimated – resulting in a very high risk of failure.
So what goes wrong?
The remaining free moisture in the slab can still move through the porosity of the slab, and can still evaporate as moisture vapour. Once floor coverings have been laid, a certain amount of ‘moisture balance’ movement occurs within the slab, and moisture movement increases. Moisture vapour forces its way out of the top surface of the slab and either creates bubbles under resilient floor coverings or dissolves/dilutes the flooring adhesives.
Then there’s that health point mentioned earlier. Bacteria, mould or fungus grows in moisture trapped between slab and floor coverings, with potential health risks to the users of the building, to say nothing of a bad smell which can’t be cleaned away.
What is the solution?
When high moisture levels are found by the floor layer, the typical response is to apply a coat-on moisture barrier. This is usually an unplanned expense for the project team.
For best results, to avoid the unexpected expense and maybe even make some savings in other directions – apply concrete hydrogel treatment.
AQURON 2000 and AQURON 2000 Medi+ concrete hydrogel treatments are unlike a traditional coat-on moisture barrier. The treatment binds up the free moisture in a hydrogel formation, deep into the concrete porosity. There is no surface coating – no compatibility issues – no risk of the treatment being worn away.
In fact, if AQURON 2000 is applied early, it can also replace the curing compound or water curing process. This is a significant saving in time and money.
This is a serious no-brainer. Save money. Save time.
Talk to the friendly Markham team about your next construction project!
Markham treats an average of 50,000 m2 of concrete floor slabs every month across Australasia. Put our experience and systems to use in your project.