Analysis of moisture measurement in concrete

Builders and flooring contractors sometimes rely on the calcium chloride test to monitor the moisture content of concrete slabs to determine if the slab is ready to receive floor coverings. The calcium chloride test can measure moisture (steam emissions) in the upper ½ to 1/4 inch of the slab, however, professionals debate whether it gives the contractor the full picture. While it is self-evident that the contractor knows the surface moisture of the slab, it is very important to know the moisture content of the slab.

To help improve the process of accurately measuring moisture in concrete, ASTM developed the F-2170 standard. Standard F2170 is a test method that has some distinct advantages over calcium chloride. The main advantage is that this test method places the probe within the concrete slab itself. This process, known as the in-situ method, provides the contractor with an accurate relative humidity (RH) reading from within the concrete slab itself. The RH test is an excellent tool for predicting the performance of a slab once it has reached equilibrium. Used in this way, it predicts potential moisture-related floor failures.

Concrete absorbs water and a 4-5" thick slab may take 30-60 days to cure properly. Once the concrete has cured for at least 30 days, testing for moisture can begin. Because concrete takes a long time to dry even in satisfactory Attempting a moisture test before 30 days is usually a waste.Concrete may take longer to test if you're working in a particularly wet environment.

Moisture measurements need to be taken in concrete before adhesives, floor coverings or other structural elements are applied. If excess moisture remains in your concrete slab, any adhesives, wood, linoleum, tile, or spray-on resilient flooring you install will eventually fail, potentially lead to lawsuits, and require removal and replacement at considerable expense.

Imagine completing a large construction project, like a new school, only to have to tear out the floor after installation, as trapped moisture in the concrete can cause floor defects. Issues like this are a safety hazard for students, staff, and staff and need to be corrected. Proper moisture testing could have pre-identified problems, but now construction deadlines will be missed, construction contracts will be penalized, and material costs will rise.

Because of this potential for disaster, it's best to correct any moisture problems as soon as possible. Whether the concrete slab is used in a healthcare facility, school, warehouse or office building, it should be tested using ASTM F2170 to prevent structural and cosmetic damage to the finished building.

You need to have a humidity/relative humidity meter and sensor to get high accuracy in your measurements.

Your device should be able to measure the relative humidity (RH) of the concrete as well as the ambient temperature. By determining the humidity conditions in and around the slab, it is easier to determine when it is safe to develop on concrete.

Using an ASTM F2170-compliant meter, the moisture content of concrete at its core can be more accurately measured using a field probe that penetrates the interior of the concrete.

The importance cannot be overemphasized in knowing that moisture lurking beneath the seemingly solid concrete surface can cause floors to cup, crack and buckle if not properly dried. Therefore, when you are working with large quantities of concrete, you need accurate and efficient moisture testing of your concrete slabs.

Don't rely solely on the calcium chloride test, which only gives you a reading of the moisture on the surface of the concrete. Take advantage of in-situ probes in addition to routine calcium chloride testing by using the new, most reliable ASTM F2170-compliant meter for multi-directional insight. A combination of both methods can provide good data and increased confidence in deciding how to install the floor.