A newer testing method to the U.S. is the insulated hood relative humidity method which like the in-situ relative humidity method, has been previously used in Europe. The ASTM F2170 and F2420 both measure the equilibrium relative humidity and temperature. The hood method measures the equilibrium relative humidity and temperature directly above the surface of the concrete slab. Relative humidity readings from the hood method tend to be about five percent lower than those from the in-situ method.
The hood method measures the amount of free water in the air directly above the concrete surface and the calcium chloride method measures how much vapor is being emitted from the surface. One of the reasons humidity testing of concrete is becoming specified more often is that these methods are not as sensitive to atmospheric conditions as with the MVER method.
The hood test method consists of securing an insulated air tight box to a bare concrete surface and the equilibrium relative humidity and temperature within the box is obtained through a probe which is inserted into the box. Like with the other moisture tests, the occupied air space above the test area shall be at service temperature and service relative humidity for at least 48 hours before making relative humidity measurements. This method is very good for those situations where drilling may not be advisable.
I could be useful for measuring the effectiveness of moisture mitigation systems.
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