The human body is a spectacular marvel of inter-related systems: microscopy, chemical reaction, and physical testing. Believe it or not, the same concepts apply to the understanding needed to complete successful concrete flooring projects. The integrity of a floor’s underlying foundation lays the foundation for flooring success or failure. Although that concept is simple, the complexity of floor physics commonly causes contractors to misunderstand two critically-important terms. Develop a strong understanding of these terms, and you enhance your odds of properly installing the floor.
Curing Does Not Equal Drying
There’s much more to flooring than meets the eye. That’s why quality concrete installation is so important. A flooring system contains: floor covering, adhesive and/or primer, patch and/or leveling compounds, concrete, and some form of vapor retarder, sub-base, and sub-grade soil.
Curing is the process by which the floor forms itself once concrete is poured. Concrete contains multiple ingredients: cement, aggregate and water. The chemical reaction of these components, called hydration, occurs over time and, with each passing day, increases the compressive strength of the slab. Successful flooring installers must allow sufficient time for curing of the concrete slab. When they do, contractors and customers enjoy concrete which is strong and durable. When contractors rush through the cure phase, concrete becomes a complex of potential moisture problems down the road. Talk about building your own nightmare.
Drying is an interactive physics process which occurs in tandem with hydration (curing), but the two serve totally different purposes. Once poured, concrete moisture must migrate from the bottom of the slab to the surface in order to evaporate. Knowing relative humidity (RH) levels in the slab help to establish how the concrete drying process is proceeding. Rush flooring application, and you risk trapping excess moisture in the slab which will eventually lead to flooring or adhesive failures, mold and mildew issues or other moisture-related problems. Utilizing relative humidity (RH) testing to give the slab time and the appropriate conditions for drying, will allow you to apply floor coverings and/or coatings with confidence.
Digital Moisture Content Monitoring
Wagner Meters provides accurate and reliable insight into concrete moisture levels. Contractors place NIST-calibrated, single-use rh probes to appropriate depths of the slab, as per ASTM F2170 standards. The probes reach equilibration with the concrete (in less than an hour) to produce accurate and immediate moisture content results. They deploy a hand-held digital meter to read the relative humidity (RH%) levels at each sensor installed to the appropriate depth in the slab, in order to obtain an understanding of, given this information, what the moisture conditions will be once a flooring or coating system is installed.
Understanding the difference between curing and drying, and many future flooring failures can be avoided.
Smith, Ron “Performing Correct and Accurate RH Testing in Concrete Slab.” Wagner Meters. Web (PDF).
ACI, “ACI Concrete Terminology,” American Concrete Institute, Farmington Hills, MI: May 2010.
Concrete Construction Magazine, Archived Issues.
The Terms of Success Part II “The Real Dangers of Hydrostatic Pressure”
The Terms of Success Part III “Humidity: Relative and Comparative Testing”