Using low alkali levelling compounds to prevent indoor air quality problems

Battling indoor air quality problems can be challenging and expensive, as the source of the problem is often difficult to identify. The problems identified must of course be fixed, but it is even more important to focus on prevention. Indoor air quality problems can be reduced by using low alkali levelling compounds.

Mould is not the only reason for low indoor air quality, as harmful volatile organic compound (VOC) emissions can also cause problems. There are two reasons of VOCs that usually arise in public debate: the plastic flooring used most often in public places, and installing it on a substrate that has too high a moisture content. The matter is, in reality, more complex than that, but there are ways to prevent problems.

Floor levelling compounds offer effective protection

Concrete has a high pH (>12.5), also known as alkaline moisture, which has been proven to cause decomposition in the adhesive and surface material of flooring. As the result of this decomposition process, 2-ethylhexanol and butanol as well as other compounds are emitted into the indoor air. The properties that contribute to the level of emissions are the composition of the products used and the aggressiveness of the substrate—in other words, the joint effect of alkalinity and moisture.

The long-term follow-up studies performed by Kiilto Oy and other studies performed in Finland and Sweden have all suggested that a layer of low-alkaline (pH <11) levelling compound between the flooring material and concrete acts as a buffer against the alkaline stress caused by the concrete below the levelling layer. Even a 2 mm protective layer has been observed to be beneficial, but it is recommended to use a layer that is at least 5 mm thick. This offers better protection against alkaline moisture.

Sustainable solutions contribute to well-being

In order for the protective levelling layer to be effective, the critical moisture limit of concrete is considered to be approximately 90% RH. Below this limit, the moisture moves in vapour form and the surface can be worked on further. Besides the protection of the levelling layer, the functionality of the structure and bonding have to be taken into consideration as well. For example, the more moisture the substrate contains, the longer it takes for the water-thinnable adhesive to cure. In no circumstances should the substrate moisture exceed 85% RH when applying adhesive plastic flooring.

The safety data sheet of the product shows whether the product is low alkali. For example, the low alkali floor levelling compounds and fillings (pH <11) by Kiilto Oy are self-curing products. Their fast curing properties are based on a binder system that contains aluminate cement. When the instructions are followed, the system enables almost the entire amount of added water to form chemical bonds.

However, the most important question regarding indoor air quality does not concern structures, products or chemical reactions, but how they affect our well-being. We spend most of our time indoors these days, and that is the reason why addressing indoor air quality problems and preventing them in the first place is a vital part of our well-being. To ensure that the spaces that we use are healthy and sustainable throughout their life-spans, we need to think ahead, be thorough and utilise high-quality solutions. In the long run, sustainability is also the most cost-effective goal both in terms of the building stock and our health.

Pertti Lindberg
Product Development Manager
Kiilto Oy