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Here's Why Those Waterproofing Silicates in Your Concrete Admixture Don't Work

Posted on Sep 28, 2017, by Michael Eckert

Adding silicates to concrete is a common tactic for battling the moisture problems that so often derail construction projects. But increasingly, these expensive concrete waterproofing admixtures are being rendered ineffective - or worse, completely redundant - by smart and cost-effective advances in flooring technology.

Why use Silicates?

Moisture is a billion-dollar problem for the construction industry. From fluctuating water tables to concrete that hasn't finished curing, seemingly minor problems with water vapor can soon spiral out of control, resulting in ruined flooring and unhygienic site conditions.

With moisture such a big problem, there's an entire industry built on moisture mitigation. Silicates - special compounds added to concrete - are one of the more common solutions available, and in many construction projects, they're specified as a first port-of-call. In an ideal world, these silicates help reduce vapor emissions in the slab, causing the concrete to become less porous - protecting flooring products like carpet or vinyl tile in the process.

However, silicates aren't as straight-forward as they might appear, and often, they're used in an ineffective - or completely unnecessary - way.

1) Spray on Silicates

Many silicates are applied after the concrete sub-floor has been poured, using a spray-on applicator to imbue the concrete with the silicate mixture. On large construction projects, this process can be time-consuming and expensive - but worse still, this "spray and pray" approach can create extremely imprecise silicate delivery.

In some cases, puddles of silicate can form, while other parts of the concrete remain untreated. This means that while some parts of the sub-floor can benefit from the silicate, overall moisture protection is compromised by areas that weren't treated.

Silicates applied in this way can also interact with existing substances in the concrete subfloor - most commonly fly ash, an additive designed to strengthen concrete (and lower costs). Given the growing prevalence of these types of concrete additives, spray-on silicates offer extremely variable moisture protection - if at all.

2) Integral Mix Silicates

The other common delivery mechanism for silicates is referred to as an "integral mix": the silicate compound is added directly into the concrete, prior to being poured. Unlike the spray-on approach, this ensures a uniform dispersal throughout the sub-floor, and requires less time in application.

However, this reveals another problem with silicate use. In order for integral mix silicates to work effectively, almost all manufacturers require a very specific ratio of water and cement to be adhered to when pouring concrete for the sub-floor. This particular ratio of cement and water ensures that excess moisture won't remain trapped in the sub-floor after installation. If you're able to follow this recommendation, you'll solve most of the moisture problems that are caused by waterlogged cement - effectively rendering the silicate redundant in the process.

An Alternative to Concrete Waterproofing Admixtures 

There's a third and final issue with silicates as a moisture management solution: they're waterproofing agents - not vapor-proofing agents. That may sound like an unimportant distinction, but the real, root-cause of the billion-dollar moisture problem isn't water: it's water-vapor.

Costly moisture problems, like adhesive failure and mold & mildew, are caused by water vapor from the sub-floor, or from the ground, becoming trapped beneath an impermeable layer. This allows moisture vapor to condense into liquid water, destroying adhesives and creating a perfect breeding ground for mold spores to fester.

Most moisture management products, like silicates, trap moisture vapor - but some products, like Milliken's unique cushion-backing, are expressly designed to allow moisture to wick away through the carpet's seams, or return to a stable equilibrium in the sub-floor.

Instead of paying-out for expensive (and often unnecessary) moisture management solutions, you can solve the root-cause of moisture problems through your choice of flooring.

how to prevent the 11 root causes of flooring failure

Michael Eckert

Written by Michael Eckert