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Moisture problems can be identified by an accumulation of water and wet spots on the floor, or visible mold.
Concrete floor moisture can be a reason for concern in any building or home. It is an issue that should not be ignored or brushed off. If unchecked, mold can lead to the following problems: rotting hardwood, damping carpet & de-lamination.
Moisture issues on concrete floors could be the result of many different factors such as, but are not limited to:
Concrete is naturally porous. The moisture on the surface might not be a concern, but moisture traveling from below or within the concrete will tend to migrate up and through it, finding its way out through any available path.
Moisture is by far the most common issue that can compromise a concrete asset and the coating that protects it.
Concrete is more likely to be affected by moisture because of a channel of capillaries that form during the hydration phase. The number of channels can be dramatically increased or decreased depending on the water-cement ratio used in the mix. The permeability of concrete can be reduced by using mixed designs with lower water-cement ratios, adding various kinds of admixtures, or applying a protective layer on the surface. Moisture-related issues are common when applying protective coatings to concrete.
Signs of Moisture on Concrete Floors
You will be able to notice moisture on the concrete floor right away if you pay attention. However, if you’re not yet sure, there are certain signs to look out for including:
Causes of Excess Moisture in a Concrete Slab
Even though existing water sources could pose a problem, they’re not usually the real culprits. The problem could come from the concrete slab itself. Slabs should be installed on a well-drained sub-floor that is adequately protected against water and moisture intrusion. These problems can be solved by using the right vapor retarder for your specific situation.
Always make sure you follow the construction code’s specifications which recommend vapor retarders with a perm rating of 0.3 perms. Installing a vapor retarder directly on the ground/ soil during construction affects its performance. Separating the vapor retarder from the ground/soil with a granular fill will create an elevation to increase separation and provide better results. The concrete may not have had enough time to dry, which could cause cracks. This is a very common problem when there’s not enough lead time.
Dangers of Moisture Vapor Transmission
Some of the potential flooring issues that can result from excessive moisture vapor transmission are:
Concrete Slab moisture testing methods and why it matters
Many tests can be done to check for moisture in concrete slabs. This section will provide information on how to do these tests and what they mean when they are done correctly.
The most basic test for measuring concrete readiness is ASTM D4263, Standard Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method. The Plastic Sheet Method involves taping a 457 x 457mm (18 x 18 in.) square plastic sheet to the concrete floor and waiting at least 24 hours before removing it. Placing an incandescent lamp close to the plastic sheet can help promote moisture to migrate.
Once the plastic sheet is removed, the concrete is inspected for darkening or other signs of moisture. Although this test has existed for decades and is still used as a surface-level test, it has several flaws and sheds little light on the severity of the moisture problem within the concrete slab. First, it does not quantify the amount of moisture; it simply indicates whether or not moisture is present. Second, it only detects moisture in the upper portion of the slab, not in the middle or lower areas where moisture is more apt to reside.
Calcium Chloride Test: Measuring Moisture Vapor Emission Rate of Concrete Sub-floor, per ASTM F1869-11, Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Sub-floor Using Anhydrous Calcium Chloride. The calcium chloride test uses the weight differential of calcium chloride salt placed on the surface of the slab for up to 72 hours to identify a moisture problem. To perform this test, the calcium chloride is placed in a sealed dish and the rate of evaporation is calculated based on the weight differential.
After 72 hours, the disk is retrieved and weighed, and compared to the disk’s pre-test weight. The dish is weighed to record pounds of water emitted per 93square meters (1,000 square feet). This weight difference indicates how much moisture vapor has emerged from the slab during the 72 hours. Failure is identified if the calcium chloride tablet is above 3 pounds in weight. Note that this test can give false readings because 90% of moisture measured comes from the top ½” of concrete. This test does not detect moisture below ¾”.
Relative Humidity Testing: Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes as per ASTM F2170 is a more accurate testing method. This method requires holes to be drilled into the concrete and a sleeve with a humidity probe inserted. This test is more precise because it can show humidity readings at various depths in concrete. Probes can also be left in concrete to deliver readings over time. The quantitative result and the measurement within the middle of the slab make this test a more accurate and reliable way to measure concrete slab moisture.
Electronic Moisture Meter: Standard Guide for Preliminary Evaluation of Comparative Moisture Condition of Concrete, Gypsum Cement, and Other Floor Slabs and Screeds Using a Non-Destructive Electronic Moisture Meter as per ASTM F2659-10(2015). This test focuses on obtaining the comparative moisture condition within the upper 1.0 in. (25.4 mm) stratum in concrete, gypsum, anhydrite floor slabs, and screeds for field tests. A concrete moisture meter measures concrete water percentage in a non-destructive manner. Due to the wide variation of material mixtures and additives used in floor slabs and screeds, this methodology may not be appropriate for all applications.
Mold is a type of fungus that feeds off of water and, in some cases, food. These grow on surfaces where there is moisture. Moisture problems are most commonly found in the basement or a crawlspace. Mold can cause health problems such as allergies, asthma, breathing problems, and even death when they are inhaled while being cleaned up.
Mitigating concrete moisture issues
Once you have your concrete moisture testing completed, there are a lot of methods available to solve any troubles you might have. There are a few different things you can try when it comes to mitigating the damage from water damage.
Issues pertaining to moisture during construction must be handled with urgency and professionally though curbing them before the construction project is complete is m ore advisable. Emphasis should be put on correct concrete mixing ratios and testing for moisture as construction is ongoing and signs of it handled with immediate effect.