Measuring Moisture Content In Concrete

It is vitally important to test your concrete slab s moisture before installing flooring over it.

Measuring moisture content in concrete.

Astm f 2170 is the standard used to measure moisture deep in a concrete slab through the application of thermo hygrometers with in situ probes. Moisture meters include visual led indicators related to the percent reading on the scale for dry moderate and saturated or wet readings. If the concrete is at 5 percent moisture content it will neither absorb nor desorb moisture if the air above it is 70 f 21 c and 75 percent rh. Testing with either method will tell you how precisely how much moisture is present making it possible to choose a surface flooring that is appropriate.

Three methods for testing concrete moisture levels. Rh testing puts the test in the right spot to give accurate concrete moisture measurement. These meters have been used for decades to measure the moisture content in different materials and substances. Astm international provides guidelines for rh testing in its standard f2170.

To use this method astm d 4263 standard test method for indicating moisture in concrete by the plastic sheet method a plastic sheet is tightly taped to the concrete. Therefore measuring rh levels at 40 depth of the slab 20 depth if drying on two sides is more representative of the overall humidity conditions of the concrete. Rh testing uses in situ probes or sensors placed in holes drilled into the slab itself to measure the moisture content at a depth proven to give the best indicator of the moisture level that the slab would have if the surface were sealed at that point. Some flooring system manufacturers have products that can handle 95 rh or mor 2.

Acceptable moisture levels in concrete according to astm standard when testing via astm f2170 the rh level of a concrete slab needs to be at or below 75 unless the flooring system manufacturer provides alternate guidelines. A definitive test that measures the amount of moisture released from the concrete requires a calcium chloride kit or a relative humidity meter. After 72 hours a humidity reading is taken under the plastic with a dew point hygrometer. How concrete hardens and dries concrete is manufactured by mixing cement aggregates such as sand and gravel and water.

How moisture gets into concrete. Often more than one method is used to get an accurate reading of actual moisture content. According to astm f2170 when drying concrete slabs have lower moisture levels near the surface and higher levels towards the bottom of the slab. When testing the moisture content in non wood materials such as concrete a relative scale of 0 to 100 is often used where 0 is bone dry and 100 is saturated.

There are three standard methods for measuring concrete moisture. Thermo hygrometers sometimes called rh meters are a special kind of moisture testing device that can be used to monitor temperature and relative humidity conditions in a given area.