Nothing concerns the installer more than the slab on which the job is supposed to take place. Technical Expert Joe Grady examines the various surface treatments available for combating moisture problems on the slab.

The subject of concrete surface treatments for moisture is quite far-reaching, mostly due to the fact that the moisture emissions may vary greatly. In other words, sometimes a “Band-Aid” application method will work in reducing the vapor-emission levels to a satisfactory and safe condition.

For example, the method needed to reduce a 6-pound vapor-emission level is different than the method needed to reduce, say, a 16-pound vapor-emission level. As always, I say make sure the provider of the surface treatment is willing to commit to a level of accomplishment. Make sure you are getting what you bargained for.

Here are some of the methods and chemicals available to bring the concrete slab within industry requirements:

Epoxy

·A two-part, 100%-solids epoxy system. It may be applied by brush, roller, spray, squeegee, or trowel. It is important to remember that epoxy materials tend to blush on the surface (blush is a white, greasy film and/or low gloss). The blush must be completely removed with either detergent in warm water or a solvent wipe. Another option is a much more involved system for controlling moisture vapor emissions in resinous systems.

·An epoxy spray applied on freshly poured concrete.

·A mix of silicate-penetrating material, plus a two-part epoxy, finished with a self-leveler (recommended due to shot blasting).

Silicates

Another method for controlling moisture-vapor emissions is the use of sodium or potassium silicates, commonly known as water glass. Silicates are applied to, and penetrate, the concrete. The lime and other ingredients in fresh concrete react with the penetrating solution to form an insoluble gel in the concrete pores. There are any number of companies that provide this service. Water glass can also be helpful in controlling efflorescence. It is important to remember that these products have limited capabilities, and may not provide long-term performance.

Membranes

Other methods to control high levels of moisture-vapor emissions include:

·A system consisting of an elastomeric (usually acrylic), in conjunction with a fiber mat and a mixture of cement and sand, followed by an epoxy coating.

·A system employing an epoxy penetrant, an epoxy coating, and a fiber membrane.

·A system consisting of a latex-modified asphalt, usually with a mat to provide stability.

·Felt-backed goods are also used, particularly by wood-flooring installers, because the felt backing acts as a dispersant.

I would like to point out at this time that, although not being concrete treatments, there are a few adhesive companies marketing products aimed at preventing moisture-vapor emissions in the 6-to-8-pound range. Not having first-hand experience with these adhesives, I cannot verify the validity of their claims at this time.

Be sure to always get a clear, concise understanding as to each company’s warranty. Solutions to moisture-vapor problems are expensive, and no one wants to put what is most likely a second installation at risk.

The following is a partial list of companies who provide materials and/or services for moisture-vapor emission control. There are other excellent sources, but due to space constraints, it would be impossible to list them all.

Creteseal (800) 278-4273; Sealflex (800) 651-2098; Floor Seal Technology (800) 295-0221; General Polymers (800) 543-7694; Sinak (800) 523-3147.