A concrete moisture meter is a type of

moisture meter Moisture meters are used to measure the percentage of water in a given substance. This information can be used to determine if the material is ready for use, unexpectedly wet or dry, or otherwise in need of further inspection. Wood and paper prod ...

used by installers of

flooring Flooring is the general term for a permanent covering of a floor, or for the work of installing such a floor covering. Floor covering is a term to generically describe any finish material applied over a floor structure to provide a walking surface ...

to measure the moisture levels of

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

. These meters have been used for decades to measure the moisture content in different materials and substances. Concrete meters have evolved from the successful wood moisture meter as flooring contractors tried to use their wood meters to measure the moisture in

. Concrete moisture meters are designed to detect moisture to a depth of 1” of a

concrete slab A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Steel- reinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ...

in order to avoid the rebar reinforcement below the surface. They are designed to be used as a relative test. The meters are used to “‘Spot check’ the top surface at one particular location on the slab.” The results can determine the best place to put a concrete

relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

test.

Limitations

There is no ASTM standard for using a concrete moisture meter to determine a final moisture content reading. Concrete moisture meters, either non-pin or pin meters are affected by what it sees in the concrete. This can be anything from the

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

of the concrete and aggregate size to the chemical properties of the slab. Uncovered concrete dries from the top down. Concrete moisture meters measure only the top inch at most and this area is drier than the concrete further down. Once a

floor covering Flooring is the general term for a permanent covering of a floor, or for the work of installing such a floor covering. Floor covering is a term to generically describe any finish material applied over a floor structure to provide a walking surface. ...

has been installed the moisture in the slab equilibrates. In order to ensure the equilibrated moisture will be
safe level
for a floor covering, a relative humidity sensor must be drilled and placed a
40%
of the depth of the slab.ASTM F 2170, ”Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes,” ASTM International.
/ref> This depth has been proven to be the relative humidity percentage that the slab will equilibrate once the top has been covered by a floor covering.

References

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