Concrete Flooring Excessive Moisture Issues
Concrete flooring excessive moisture can lead to early failure of the concrete slab and any surface coating adhered to it. Prevent excessive moisture in concrete slab flooring by use of with proper design. Use products like use
Takeaway: Excessive moisture in a concrete slab can lead to premature failure of floor coverings. Learn about the effect of moisture on concrete and other aspects of good concrete coating practice.
Water is an essential ingredient in concrete. Initially, moisture must be present for desired properties. However, excessive moisture in a concrete slab can lead to premature failure of floor coverings.
Many high-quality flooring installations have failed by blistering and peeling due to moisture vapor migration through a concrete slab.
MAXSEAL® SUPER is a special waterproofing coating improves the osmotic effect of the application allowing the penetration into the concrete through its capillary system. The product crystallizes inside sealing, waterproofing and protecting the concrete structure. It has been designed to be applied on fresh or set concrete, pre-cast concrete, concrete blocks or cement plasters but is also suitable for applications in bricks and masonry learn more….
Addressing concrete floor moisture begins with proper design, curing and surface preparation. Testing for moisture content and identifying its source are very important steps toward controlling moisture within the concrete. The relevance and accuracy of any testing depends on the frequency and locations of the tests performed. A moisture mitigation strategy appropriate for the floor covering and structure is determined by these test results and knowledge of the moisture source.
Testing for Concrete Flooring Excessive Moisture
ASTM F1869, Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride, is commonly called the calcium chloride or the MVTR Test. It involves using a dish containing calcium chloride that is placed on the concrete surface and covered with an airtight dome. After waiting 72 hours, the dish is retrieved and weighed and the results reported as pounds of water emitted from 1,000 ft.2 (93 m2) of the surface in 24 hours.
ASTM F2170 Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes, is commonly called the relative humidity or the embedded probe test. In this method, a hole is drilled into the slab and then a sleeve and probe are inserted to take a reading. Usually, the best method for evaluating concrete moisture content involves a combination of techniques. Combining ASTM F1869 and ASTM F2170 provides an indication of both the current moisture vapor emissions and the potential amount of moisture can cause problems with the flooring system.
Moisture Mitigation in Concrete Floors
Moisture vapor emission test results cannot guarantee that floors will not fail unless the slabs are sealed with a permanent penetrating moisture vapor emission control system. Once a moisture level requiring remediation has been identified in the concrete to receive the flooring system, several options are available. Beginning with the simplest, easiest, and least expensive method may not resolve the issue, but can improve the situation so another method may prove effective. Monitoring the internal humidity with ASTM F2170 is especially helpful to gauge the effectiveness of natural drying.
MAXSEAL® SUPER a specialized waterproofing coating improves the osmotic effect of the application allowing the penetration
into the concrete through its capillary system. The product crystallizes inside sealing, waterproofing and protecting the concrete structure. This has the effect of preventing moisture penetration from above or below the slab. Applied on fresh or set concrete, pre-cast concrete, concrete blocks or cement plasters learn more….
Dehumidification
Specialized equipment that supplements the HVAC system designed for the structure is commonly used to lower the relative humidity on exposed concrete or to increase the temperature to accelerate drying. However, the concrete must achieve sufficient strength and maturity before any attempt is made to accelerate natural drying. (Learn more about the importance of proper humidity levels in Why Concrete Delamination Occurs and What to Do About It.)
Application of a Moisture Mitigation System
Installing most moisture mitigation systems requires some sort of surface preparation. Factors to consider include:
- Compatibility of the system with the flooring finish
- Cost
- Cure time
- Difficulty of installation
- Ability of the system to mitigate the existing moisture level
- Service life
Moisture mitigation systems applied as topical treatments to concrete have been successful in reducing moisture vapor emission rates.
Liquid Membranes. Liquid membranes are usually water-resistant and acrylic– or epoxy-based. Low-cost, water-resistant acrylics, typically used for less severe moisture problems, are the simplest to apply.
Reactive Penetrants. Reactive penetrants are designed to react with the calcium hydroxide and moisture within the concrete to form a gel or crystalline deposit that restricts moisture diffusion through the concrete pore structure.
Sealtight – scientific formula causes a reaction that solidifies the component parts of masonry, concrete and cement mortars into a single mass making it waterproof. Sealtight Clear is also resistant to acid, oil, fuels, fats and grease. Increases the density of the substrate, increases wear capability, will prevent dusting, brick fretting, cracking.
Modified Cementitious Overlays. These polymer-modified or polymer/cement hybrids form very dense, partially permeable overlays that reduce moisture and alkalinity to help minimize problems with the floor covering system.
Choice of system is available here Quick Links Drizoro Maxseal Flex | Drizoro Maxseal Foundation Super | SealTuff Trafficable MultiSurface which a completely trafficable cementitious system
Dispersive Membranes. Dispersive membranes include a porous sheet bonded to the concrete with a polymer coating that absorbs the moisture and allows it to wick out through joints and edges of the installed flooring.
Assembly Systems. Assembly systems typically consist of a flexible, non-breathable polymer sheet that has dimples or ridges to interlock with an adhesive to bond to the concrete surface.
Combination Systems. Combination systems utilize two or more of the previously described approaches to moisture and alkali mitigation. Often the design is tailored to the measured moisture-vapor emission rate (MVER).
Consideration of Alternative Flooring
Different flooring systems have varying tolerances to concrete moisture. For example, a thin-set ceramic tile flooring may pose fewer problems for high moisture than a thin-film epoxy coating. Excess moisture can still cause efflorescence, staining, and biological growth, even with moisture-tolerant flooring materials. Carpet can still mold even if it is breathable, and polished concrete frequently must be sealed with a vapor-inhibiting stain or coating that may then have issues with moisture from the concrete.
Replace the Concrete Slab
To solve some concrete flooring with excessive moisture problems, the only solution may be to remove the concrete and install a properly designed vapor-retarding barrier, using a low-moisture emission concrete mix design to produce a properly cured new slab. This course of action is usually the last option to consider after other approaches have failed. (Then, avoid long-term problems by reading the article Correcting and Preventing Concrete Corrosion.)
Summary
Water found in concrete may originate with mixing, curing, or surface preparation, from the environment, or from leakage, spills or cleaning. Excessive moisture in a concrete slab can lead to premature failure of floor coverings. Concrete may be tested for moisture in accordance with the ASTM methods described here.
To learn more about the effect of moisture on concrete and other aspects of good painting practice, visit sspc.org or phone 877.281.7772 to order the complete SSPC Vol. 1: Good Painting Practice.
Written by Fred Goodwin a chemist with >30 years of experience in the construction chemicals industry, including cement manufacture, research, development, and technical support of grouts, adhesives, coatings, shotcrete, stucco, flooring, and concrete repair materials. Our thanks for this article on concrete flooring excessive moisture. Concrete Flooring Excessive Moisture from the surface or from beneath can be destructive.
