Testing the Concrete Surface pH level
Most flooring and adhesive manufacturers also require that a pH test of the concrete surface be performed.

Soluble alkali salts are naturally present in concrete. However if there is sufficient moisture within the concrete to place these salts into solution, the pH level at the surface of the slab will rise to levels that can lead to the breakdown of adhesives and flooring materials. What is important to understand is that to perform a pH test one must introduce liquid water. If there is not sufficient water in the concrete to create a solution after the flooring system is installed, pH will not be an issue regardless of what the test indicated. In short, getting rid of the water and protecting the slab from moisture entering from below, will ensure that pH will not be an issue.

Moisture Mitigating Strategies

In the past, most projects have delayed implementation of a moisture mitigation strategy until it is certain that the treatment will be needed. Using this approach, the moisture level of the slabs is tested a few weeks before the flooring is scheduled to be installed. If the moisture levels are found to be acceptable, the moisture mitigation system is not installed. If, however, the moisture levels are not found to be acceptable, the system is installed. The biggest problem with this approach is that more often than not the floors are not found to be at an acceptable moisture level. Implementation of the mitigation system at this late stage significantly increases the cost and is a disruption to other trades.

As moisture-related flooring problems increased over the years so have attempts to treat or mitigate excess moisture in a concrete sub-floor.

The following approaches are currently being used to mitigate high levels of moisture in concrete sub-floors.

Accelerated Drying
In many parts of the country the ambient environment is not conducive to natural drying of a slab in a timely manner. One approach that has proven effective on some projects is to alter the ambient conditions using equipment that can raise the interior air temperature while at the same time lower the ambient relative humidity. This process is not inexpensive and still requires time. This method also works best when surface of the slab is ground or shotblasted open to aid in the release of moisture.

Topical treatments
Current topical treatments for moisture mitigation fall into the following categories: Reactive Penetrants, Moisture Mitigation Coatings, Modified Cementitious Overlays, Alternative Finishes

Reactive Penetrants
There are many companies promoting the use of sodium, potassium or lithium silicate as a solution to slab moisture problems. Some of these products are applied immediately following final finish of the concrete while the application of others is delayed. In all cases these fluid applied products must find sufficient calcium hydroxide in the concrete to complete a reaction. Some of these silicate-based treatments have proven to be very good surface densifiers for industrial warehouse slabs. However, their use as a moisture mitigation strategy cannot be validated by any test recognized by the flooring industry.

Moisture Mitigation Coatings
There are scores of topical coating materials being promoted for moisture mitigation of concrete slabs. These products include acrylics, hybrid epoxies and urethanes. While none of these systems have a perfect track record, to-date the best of these systems have proven to be the most successful approach to topical moisture mitigation.

Wally Johnson, U.S. Concrete’s vice president of sales and marketing points out that the main concern with moisture mitigation coatings is that a high level of moisture will remain present within the concrete. This can lead to the development of osmotic cells beneath or within the coating, or fuel an alkali-silica reaction (ASR) or near-surface alkali reaction (NSAR) if the aggregate materials are susceptible to such.

Modified Cementitious Overlays
There are several companies promoting the use of modified cementitious materials to mitigate concrete sub-floor moisture and pH. One major attraction to this approach is the idea that one can mitigate moisture issues and level the floor in one step. While the jury is not in on all of these materials, at least one major player withdrew its product from the U.S. market after experiencing a major failure.

Alternative Finishes
The high cost of dealing with slab moisture problems and construction delays has led to an increased use of alternative flooring such as bare, polished or stained concrete. While these finishes may be suitable for some facilities they are not suitable for many others.

Other Mitigation Approaches

Integral Admixtures
A number of companies are promoting the use of chemicals introduced into the concrete to mitigate moisture. While a number of these materials are capable of demonstrating waterproofing properties, the effectiveness of most are not able to be validated by test methods recognized by the flooring industry.