Concrete Moisture Emission Vapor Testing: Different Tests, Different Results – Why is That?
The two most popular concrete moisture vapor emission test methods are the ASTM F1869 calcium chloride dome test and the ASTM F2170 in situ relative humidity drill test. These are very different and distinct in methodology and results; they cannot be compared to each other. Both are quantitative result tests, though they measure different things. To compare the results of these two tests is like comparing a person’s blood pressure and temperature. Each one alone has a meaning, but they cannot be compared for any specific result.
The calcium chloride dome test, which takes between 60 and 72 hours, will give a result of an emission rate, as pounds per square foot per a 24-hour timeframe. A gallon of water weighs eight pounds; therefore the measurement is roughly how much moisture vapor changed to a liquid is emitted. With this test, you get an actual weight that can be compared with a physical property.
The relative humidity, drill test (in situ), on the other hand, will give results by inserting a probe into a drilled hole, at 40% depth of the total thickness of the concrete substrate and letting it acclimate for one to two hours. The probe does not measure the weight of condensed vapor, but rather the percentage of humidity in the concrete substrate at that depth.
There are advantages and disadvantages to both types of tests. The calcium chloride test can be performed only one way and must use the same consistent tools, equipment and procedure. The relative humidity test also has only one approved way of performing; however, the tools are varied. For example, after the hole is drilled, a probe is inserted, which can either be a “smart” sleeve or a hollow sleeve (in which a probe is inserted for RH readings).
For comparison purposes, the F1869 (calcium chloride test) can have a maximum 5 lbs. emission rate before a moisture retarder must be applied to the concrete surface, though some products require 3 lbs. or less. The F2170 (in situ test) requires 85% relative humidity as the maximum allowable moisture level.
Here are two real-world examples. Case number one: F1869 results of 11 lbs. emission, F2170 inserted probe results of 75%, “smart” probe results of 94%, pH of 9. In this case the HVAC is operational, the temperature is at 75F, and humidity is at 63%. Case number 2: F1869 results of 9 lbs. emission, F2170 inserted probe results of 85%, “smart” probe readings of 99%, pH of 12. The HVAC is operational as well as negative air machines, with a temperature of 75F and humidity of 46%.
In both cases we have two test styles with three different readings. Each means something is going on, but what? In both cases, the testing was done by the ASTM procedure by certified personnel, with recently calibrated equipment. In each case, the original test results done to ASTM F1869 standards were considered suspicious or were not recognized by the floor-covering manufacturer.
These are just two cases where the results must be carefully considered and the flooring product manufacturer should be contacted for guidance. The most reasonable conclusion is that a form of floor preparation will be required as well as a moisture barrier application; which is an insurance against any future adhesive, flooring or installation failures.
The testing protocol is required so the installation contractor, general contractor, architect or owner may make an intelligent decision as to the type of floor preparation, any moisture barrier application and the potential economic impact this will have on the project.
Bottom line: Testing must be performed within a reasonable time prior to floor covering installation, in case a negative issue is present. This gives the contractor or installer enough reaction time to discuss the correction action required and economic impact. Also, do not neglect the importance of acclimating the test areas. The HVAC must be operational for three days prior to testing, and of course all testing must be performed to ASTM protocol.