1. Moisture: Although moisture is an ingredient in all failures, there is no linear correlation between moisture levels and the majority of flooring failures. The exception is when the moisture levels are high enough to either interrupt and/or prevent curing of the coating and/or adhesive. High vapor emission levels or dewpoint generally creates high moisture levels. Although these two activities are completely unrelated to each other, the end-result has many similarities.
a. Vapor emission: vapor emission is the movement of water in its gaseous state. Water vapor responds only to temperature and humidity. As a result, the vapor emission levels are entirely dependent upon the differences in relative humidity and temperature between the concrete surface, concrete interior and the use environment. Vapor pressures are often blamed for vapor emission problems, but in reality, the actual vapor pressures are so low, that they can only be calculated, not measured. In fact, vapor pressures rarely exceed 0.50 psi and under livable conditions, cannot even achieve pressures exceeding 1.0 psi. Once a relatively impermeable material covers the floor surface, the influence of room/interior environmental humidity is essentially eliminated. Underneath the flooring material, the humidity moves to equilibrium and the humidity under the flooring material(s) typically ranges between 80-100%. If the adhesive/coating has not fully cured, and the concrete temperature is within 5 degrees of dewpoint, condensation can occur, preventing the adhesive/coating from curing.
Whether this is a temporary effect or permanent effect is largely dependent on three basic influences; the progress of adhesive cure, concrete porosity and concrete permeability.
b. Dewpoint: Dewpoint may well be the least understood and least appreciated influence in flooring failures. Dewpoint effects can strongly resemble vapor emission, but is largely controlled by a natural hydrological cycle. Dewpoint can occur as the concrete temperature cools. Moisture begins to condense in and on the concrete surface. The condensed moisture might not even be visible if the interior section of the concrete is cooler than the surface as the moisture will tend to migrate to the cooler interior. If the surface continues to cool and reaches dewpoint, the concrete surface can literally become saturated with moisture. This has potential devastating effects on many types of adhesives and coatings, even though the majority of the industry is virtually unaware of this phenomenon.
2. Alkalinity: the deleterious effects of alkalinity has been identified, yet the exact mechanisms of damage are not completely understood. The ways alkalinity can damage adhesives and coatings are complex. Each type of degradation is dependent on one or more of the following; pH level, concentration of alkalinity, sensitivity of compound and/or its components to alkalinity levels, availability of moisture, temperature, humidity and permeability of applied goods. For example, an adhesive may have excellent resistance to moisture, yet as the pH levels increase, the tendency toward reemulsification may increase exponentially.
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There exist situations when a seemingly modest pH increase can govern whether or not an adhesive can continue to usefully function. If a product were resistant to a pH of 9.0, it doesn't suggest the adhesive would continue to resist, an increase of pH to a level of 9.2. Keep in mind that the pH scale is logarithmic. Each full digit increase (i.e. 7.0 to 8.0) is a tenfold increase in pH. A seemingly inconsequential increase of 9.0 to 9.2, is nearly twice as alkaline.
It is important to note that soluble and emulsifiable are completely unrelated terms. Most adhesives are emulsions that lose their ability to suspend or "dissolve" in relatively "pH neutral" water after completion of its cure. Water-soluble is typically continuing ability of a solid to readily dissolve in a relatively "pH neutral" water medium. Emulsions can become "soluble" as the pH increases. An increase in pH can also separate the solids component of an adhesive from its plasticizer. This prevents the adhesive from functioning as intended and appears as a "moisture-related" flooring failure.
3. ASR (Alkali-Silica Reactions): is sometimes considered a "newly discovered" phenomenon that actually is well-known among those in heavy concrete construction, and its discovery dates back to the 1940's. ASR as a problem, is worldwide and extremely costly. Its occurrence is somewhat unpredictable and incompletely understood. The majority of research to date has been focussed on the structural significance of its destruction and is often referred to as "concrete cancer".
The correlation between "low-level" ASR and flooring failures was not considered until our research (in-house) found many parallels between "mysterious" flooring failures, site conditions and ASR. In fact, the information was so startling that we were at first reluctant to go public with the information until we were certain of the influence of ASR on flooring failures.
Without going into a detailed explanation, ASR occurs when the strongly alkaline cement actually begins to dissolve susceptible sand and rock within the concrete itself. The chemical reaction creates a gel material, which in turn creates tremendous pressures in the pores of the concrete surface. The amount of hydraulic pressure was estimated in a 1953 study to be approximately 500 psi. A later study more precisely determined the pressures to range from as low as 1700 kPa (250 psi), up to 10,300 kPa (1,500 psi). This activity helps to explain the tremendous pressures witnessed under sheet goods and epoxy floor systems. It also is a much more plausible and scientifically responsible theory than the vapor pressure (up to a pressure of 6.9 kPa, 1.0 psi) and unsubstantiated "backpressure" theories.
What cannot be covered in this article are "moisture problems" that are not really concrete originated moisture problems at all, i.e. blue, gray and/or red stains in vinyl, VCT curling (when the center of VCT is still bonded), and many others. Yet many moisture "experts" continue to "repair" problems with unnecessarily expensive and inappropriate methods. These "repairs" are not only a waste of time, resources and money; they also contribute to the ongoing myths that surround what should be a science-based and logical approach.
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