Garage Floor Moisture Testing MethodsConcrete moisture vapor emission is a natural occurrence of any concrete slab. Before coating a garage floor, garage floor moisture testing should be completed. New slabs have a mix water drying process and should be allowed to cure a minimum 30-60 days before a coating is applied. It doesn't matter if the slab is above or below grade. Besides the drying process of new concrete, established floors can also wick moisture from sources below the slab, even when approved moisture barriers were installed. This moisture drive can easily break the bond of floor coatings causing your garage floor coating system to fail.Moisture Vapor PressureTemperature and humidity have a direct affect on the pressure exerted on the concrete surface measured in "pounds per square inch". In your garage, the static vapor pressure is often half the pressure inside or below the concrete garage floor slab. This causes the moisture to literally be sucked upward, often trapped beneath the floor coating materials. This hydraulic pressure can easily lift epoxy and other floor coatings causing them to bubble and peel. It is crucial to use even the most basic testing methods to determine if your floor has a moisture issue before coating.
Moisture TestsThere are 3 tests primarily used to determine moisture level content in your garage floor concrete. These three garage floor moisture testing methods include:1) The calcium chloride test involves measuring the amount of absorption of moisture by placing a covered Petri dish of calcium chloride on the concrete slab to remain in place between 60 and 72 hours. The calcium chloride absorbs any moisture vapors that transmits through the concrete floor and you measure the amount using a gram-weight scale with a gradation of 1/10th (0.1) gram. Weigh the calcium chloride container before and after exposure to the concrete slab on the same scale. The test results are stated in pounds per 1000ft squared in a 24 hour period. This test should be conducted in interior conditions when the building is closed with air conditioner and systems turn on simulating actual use conditions. The test is not recommended for exterior use. Since most garages are normally unconditioned space with wide temperature fluctuations, this is still and acceptable method of testing the area. Here's where you can purchase the Gundlach Calcium Chloride Test Kit 
2) Relative Humidity using In-situ Probes is the most accurate method to determine moisture levels. This requires placing probes in the concrete and taking readings with a hygrometer. A relative humidity reading of 75% or below is acceptable for most. These testers are primarily used by professionals as the cost about $400. The Tramex Concrete Encounter Moisture Meter 
is a non-invasive tester also available that does not require the drilling of holes to install the probes.
What do the Test Results Mean?Most flooring manufacturers and ASTM set the vapor transmission limit at 3 lbs/1,000 sq. ft./24 hours. If it is greater than this, you may wish to consider applying a moisture barrier product such as AquaLok II before applying any floor coatings. Aqualok II reacts with available alkali to form a crystalline structure, densifying concrete at the depth of penetration, reducing vapor and moisture drive, and allowing application of coatings and sealants to the concrete floor.Alkalinity TestingAlkalinity is another factor to test for prior to coating concrete. The internal alkaline chemistry of concrete prevents reinforcing steel from rusting. However, when the surface of a concrete slab has an alkalinity over 9 on a pH scale, adhesive and bonding systems will fail. You can use an Economical pH Test Strip with a Range 1.0 to 14.0 to check where the vapor testing is performed. A PH reading in the 7 range is ideal. Readings over 9 will cause devastating damage to your bond.
Learn more DIY tips and garage floor moisture testing methods Here's Why Garage Floor Coatings Fail ------- end garage floor moisture testing methods ---------
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