Moisture and Alkalinity Testing
Moisture in concrete slabs, including issues related to high alkalinity (present in all new concrete) remains the number one cause of flooring failure in our industry.
New concrete substrates must be properly cured and ‘thoroughly dry’ before commencement of any flooring installation. As concrete curing depends on such things as the environmental conditions, mix design, location of the slab and the time of year, substrate surfaces may require more drying time than normal before they may be considered ready for quantifiable moisture testing (ASTM F2170 and or ASTM F1869) and ultimately a floor covering installation.
While curing to design strength typically takes 7 to 28 days, to become ‘thoroughly dry' the same slab can take months (rule of thumb – allow 1 day of dry time per 1mm of slab thickness or 1 month / per inch of thickness).
Note that moisture from within the slab is only part of the problem. Ambient Relative Humidity (RH) above the slab is also a contributing factor requiring heat and air exchange/ movement to manage RH to acceptable levels.
New concrete substrates must be properly cured and ‘thoroughly dry’ before commencement of any flooring installation. As concrete curing depends on such things as the environmental conditions, mix design, location of the slab and the time of year, substrate surfaces may require more drying time than normal before they may be considered ready for quantifiable moisture testing (ASTM F2170 and or ASTM F1869) and ultimately a floor covering installation.
While curing to design strength typically takes 7 to 28 days, to become ‘thoroughly dry' the same slab can take months (rule of thumb – allow 1 day of dry time per 1mm of slab thickness or 1 month / per inch of thickness).
Note that moisture from within the slab is only part of the problem. Ambient Relative Humidity (RH) above the slab is also a contributing factor requiring heat and air exchange/ movement to manage RH to acceptable levels.
There are two recognized moisture testing methods:
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1. ASTM F2170, Standard Test Method for Determining Relative Humidity in Concrete Slabs Using In-Situ Probes.
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2. ASTM F1869, Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.
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The number (quantity) of tests are the same for both test methods. Three test locations for the first 1000 square feet and one test location for each additional 1000 square feet. Therefore, a 5000 square foot space will require seven individual test locations.
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Existing slabs, on grade or elevated must be tested.
Where there is moisture, mold can grow. Residual moisture vapor from newly poured concrete or moisture ingress from a foundation crack, leaking pipe or broken vapor barrier can cause many issues for flooring and effect the air quality of the living space. |
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pH Testing for Alkalinity
All new concrete is high in alkalinity (approximately 12.5 on the pH scale). As moisture vapour escapes concrete, surfaces are left with alkaline deposits that will exceed the recommended level (for many flooring products) of 7 to 9 on the pH scale. Adhesives (including peal-n-stick), self leveling cements and moisture treatment products can be adversely affected by this and therefore should all have their individual warranty requirements checked before proceeding with installation. Alkalinity-pH testing is simple, quick and inexpensive to perform and typically done at the same time as moisture testing. |
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