This article was first published in "ProInstaller Magazine, Fall 2014 Issue."
When To Test Concrete To ASTM F2170? - A Quick Tip
ASTM F2170 is an excellent test for determining the actual moisture condition of a slab. As a result, this type of test is recommended by many international standards including ASTM, British Standards, and most Scandinavian standards, as well as being specified by floor covering, coating and adhesive manufacturers worldwide.
There is a potential for condensation to appear on the sensor during the test period, due to the high relative humidity within the concrete until the concrete has sufficiently dried.
If condensation occurs during the test period, then the sensor will continue to indicate that the slab is wetter than it actually is, even if the concrete has subsequently dried. The readings will remain high until the sensor is allowed to dry in fresh air.
By testing non-destructively per ASTM F2659, the inspector can get an instant and precise evaluation of the moisture conditions within 1.0” below the surface of the slab.
This is done by using a moisture meter that gives a measurement of % moisture content by weight. A moisture map of the entire floor can be built up, showing how wet the slab is and where the wettest locations are. This moisture map helps the user determine where it is best to locate the sensors for F2170.
If the meter readings indicate the slab is wet, then the user must still perform F2170, but should only leave the sensors in for long enough to confirm per the manufacturer’s acceptable limits. The new probes are designed to give a good indication of high relative humidity after an hour of testing.
However, if the results are over the manufacturer’s specification after an hour, then it can be confirmed the slab is too wet.
At this stage, the probes can be removed and the sleeves capped until further testing is required before mitigation can be carried out. This can only be done with reusable relative humidity probes that can be removed after one hour and reinserted at any time in the future to ensure accurate results.
Make sure to conduct the test for 72 hours to fulfill the requirement of ASTM F2170 to confirm the slab is dry per manufacturer’s acceptable limits.
Finally, for best results, the combination of ASTM F2659 non-destructive moisture content testing and F2170 in-situ relative humidity testing allows for a more complete picture of the moisture conditions of the slab.
Added 08 Oct 2014 Author: Tramex