This article is a short version of the extensive and complex explanation of the comparison of the Calcium Chloride Vapor Emission Test (ASTM F 1869) and the concrete substrate In-Situ Relative Humidity (R/H) Probe testing procedures (ASTM F 2170).
The Calcium Chloride Vapor Emission Test (ASTM F-1869) is designed to accurately measure the actual quantity of vapor emission released from 1,000 square feet of concrete substrate in a 24-hour period. The test result is measured in pounds per 1,000 square feet in a 24-hour period (lb./k/24) at the time of the testing. This testing and evaluation of released moisture enables the testing agent to advise the Client, their General Contractor and/or the Flooring Contractor of the accurate vapor emission conditions at the time of the testing and to tailor the appropriate selection of adhesives and/or substrate moisture retardant applications necessary for use with the flooring installation for each individual project. The acronym for the pounds of moisture emission emitted is Moisture Vapor Emission Rate or “MVER”.
The In-Situ Relative Humidity Probe Test (ASTM F 2170) is designed to determine the Percentage of Relative Humidity (R/H%) inside the interior of the Concrete slab at a depth of 40% of the slab thickness (2” deep in a 5.0” thick slab). The R/H probe estimates the “potential” amount of moisture recorded in the lower portion of the Concrete slab. There is no factual way to field test and accurately determine the total quantity of moisture in a concrete substrate using the ASTM F 2170 testing protocol.
Point 3.1.1 in the 2170-19 standard defines relative humidity, n—ratio of the amount of water vapor actually in the air compared to the amount of water vapor required for saturation at that particular temperature and pressure, expressed as a percentage.
In order to properly quantify the volume of something you must first know the size of the container you are using to measure with (Gallon, Quart, etc.). Unfortunately, it is impossible to measure the size of the voids in the millions of vertical capillaries contained in a conventional concrete substrate. Without being able to determine the volume of the void space that contains the slab moisture, it is impossible to determine the volume of moisture contained in a concrete substrate by using the ASTM F 2170 test protocol.
When concrete cores are taken to Laboratories for testing the lab cannot actually determine what the true In- Situ Moisture content of the core was, at the time of removal, because the moisture content changed during the transportation of the core to the lab. In my testing experience and in interviews with other moisture testing professionals, the professionals indicated that approximately 8 out of 10 concrete substrates tested with the in-situ R/H probe have produced R/H levels exceeding 85%.
The down side to the R/H probe is that it is extremely sensitive to slab temperature. The ASTM F 2170 standard indicates that a 1-degree change in the slab surface temperature can change the probe R/H% reading up to 5%. The R/H probe test is a pass or fail test. If the probe test result exceeds 75% or 80% (Depending upon the requirements of the individual flooring and adhesive Manufacturer) the substrate has to be treated with a more sophisticated moisture retardant material.
Today’s sophisticated moisture retardant coating applications are expensive, time consuming for application, and at times are not necessary for the success of the flooring application.
While the In-situ probe requires a minimum of 24 hours to perform the testing vs. the 5- day testing period for the Calcium Chloride Moisture Test, the individual in-situ-R/H probe device is approximately 3 times the cost of each calcium Chloride dome devise (dependent upon the quantity purchased, manufacturer and/or other source of supply). Because of the computerized nature of the device the R/H probe can be easily damaged on site.
I am a member of the ASTM F 1869, ASTM F 2170 and ASTM F 710 concrete substrate preparation and pH Testing committees. I often use both tests in evaluating concrete moisture issues for my clients. The two different test procedures evaluate two entirely different moisture conditions. Both tests must be performed in a fully enclosed and properly acclimated facility.
Point 3.1.2 2170-19 standard defines service temperature and relative humidity, n—average ambient air temperature and relative humidity that typically will be found in a building’s occupied spaces during normal use.
Many people believe there is a comparative correlation (results from one test can be directly related to the results of the other test) between the Insitu R/H Probe test and the vapor emissions results recorded via Calcium Chloride testing of the substrate. This is not true. Many believe you can use the R/H Probe test in an un-acclimated area. This concept is also incorrect. The Probe test is more sensitive to improperly acclimated test conditions than the CC test. The F 1869 test provides quantification of the MVER that accurately reflects site conditions that exist at the time the testing is performed. A change of 1.0 F in slab surface temperature accurate can alter the Probes reading as much as 5%.
Many locations being tested do not experience the proper building enclosure conditions, interior Temperature and Relative Humidity conditions required to perform the proper moisture testing and evaluation. Without the proper environmental and building enclosure conditions in place it is impossible to obtain accurate slab moisture testing results.
In order to not mislead the retaining party, any Concrete Moisture Testing performed in an area that is not properly enclosed and is improperly acclimated must be reported as a “qualified test result” based on the insufficient environmental conditions in place at the time of the testing
The absolute best testing sequence is to perform a combination of an equal number of both test procedures at the same time. This is significantly more costly and I have found reluctance by clients to pay for both procedures unless the flooring installation is in a large clean room or unique medical facility flooring application.
My firm uses the ASTM F 1869 Calcium Chloride tests for many of our clients because they require a more exacting test result that will enable the RGC to provide the most cost effective and best performing type of adhesive or vapor retardant membrane application for use with the existing project.
