Doing the right thing: A properly prepared test site for an ASTM F 1669 Calcium Chloride Test.  Four 12 x 12 tiles were removed, then the substrate was cleaned by light grinding and left for 24 hours. Next, the test kit was placed. To the left of the test kit is an ASTM F 2170 relative humidity test, where a hole was drilled and a relative humidity probe is inserted almost 2” into the concrete.


The importance of grinding: If you are not grinding the surface of the concrete before placing Calcium Chloride test kits, you are not doing the test correctly and your results will be invalid. Photo courtesy of George Donnelley.

The ASTM Committee F06 on Resilient Floor Coverings was formed in 1968.  The Committee, comprised of over 150 volunteers, has jurisdiction of over 42 standards that play a role in all aspects important to the floor covering industry and related products, including substrate preparation and concrete moisture testing. Over the past eleven years, several documents regarding concrete have been published that have had a strong impact on the entire floor covering industry.  I have been a member of the committee since 1993 and have been proud to be a part of work that has done a lot to raise the standards in our industry.

The last time I covered this topic was my April 2008 column, “Moisture Testing Update: New Documents will clarify confusing standards.” This column talked about ASTM F710-08 Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring*, which contains a great deal of information on concrete substrates and subfloors and which has been used throughout the industry, not just the resilient side.

The committee recently balloted some changes to another important document, The Calcium Chloride Moisture Test,  officially known as F 1869 Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride*.  This test method has been in use since the 1950s and became an ASTM Standard in 1998.  Since then, laboratory studies and field testing experience has been used to refine the document and make improvements. Several of those changes were recently approved.  The new document will be published shortly as ASTM F 1869-09 Here are several key changes.  The quotes from ASTM F 1869 shall be in bold print so you can see the actual language the standard calls for.



Not on this floor: Calcium Chloride Testing must not be done over any type of patching or leveling compounds, including cementitious or Gypsum.

The scope has been clarified to say “This test method covers the quantitative determination of the rate of moisture vapor emitted from below-grade, on-grade, and above-grade (suspended) bare concrete floors.” The addition of the word “bare” is important.  Several changes to the document have clarified the fact that the test must be done on bare concrete.  For example a new sentence in the scope says “This test shall not be used to evaluate moisture vapor emissions over coatings on concrete or over patching or leveling compounds.” ASTM F.06 Second Vice Chairman Larry Press of Helmitin Adhesives told FCI how important these changes are.

“More protection will be provided to the consumer and/or floor covering contractor/ installer as it concerns moisture reduction systems and the use of F 1869 to quantify a warranty provision,” Helmitin said. “While the document has always been specific that the test could not be used over any type of extraneous materials such as curing compounds, sealers, residual adhesives, etc. it has become a practice of the manufacturers of these systems to hinge their warranty on ASTM F 1869.”

One of the most common mistakes when doing calcium chloride testing is the failure to clean the floor, or not cleaning it properly. I have often spoken in my seminars and written here in FCI about the importance of cleaning the slab by grinding before putting the test kits down. The new version of F 1869 calls this out specifically in very clear terms:

7.1 Remove floor coverings or coatings. Lightly grind an area 20 by 20 in. (50 x 50 cm) to produce a surface profile equal to ICRI CSP-I to CSP-2. Grinding should remove a thin layer of the finished concrete but not expose coarse aggregate, unless the surface had been abrasively treated previously.



Not on this floor: Calcium Chloride Testing must not be done over any type of patching or leveling compounds, including cementitious or Gypsum.

In an October 2005 FCI article (Concrete 101 FCI October 2005), Jon Namba gave a brief description of the term CSP.  “ICRI is the International Concrete Repair Institute and CSP is Concrete Surface Profiles. The ICRI utilizes a set of nine distinct profiles that replicate different degrees of concrete surface roughness. CSP 3 is considered a light shot blast.  Grinding is considered a CSP 2.”  A light grinding should produce a texture similar to medium grit sandpaper.  It is not enough to scrape, sand or wire brush the surface.  It must be cleaned by grinding.

The test method previously required that all slabs had to be cleaned and then left for 24 hours before putting the kits down.  This meant three trips to do the test.  That has changed now for new slabs or on renovations where floors are ripped up well before the test is done.   The new language says, “Concrete floors that have not had floor coverings or coatings within 30 days prior to testing can be ground and tested without this waiting period, provided the [temperature and humidity] conditions have been met.” This change will save a trip on many jobs - reducing the time required to conduct the test. 

Another big issue is temperature at the time of testing.  The test is not accurate outside a specific range of temperature and humidity.  Ideally, the building Heating/Ventilation/Air Conditioning (HVAC) should be on but for many reasons this is not always possible and we are often asked to test when the HVAC is not operating. There may be a temporary system operating, and if conditions are right the test can be done.  The document has not changed in this regard but it is important to make sure you are aware of the requirements. 

The test site should be at the same temperature and humidity expected during normal use. If this is not possible, then the test conditions should be 75 +/-10°F (23.9 65.5°C) and 50 +/-10 % relative humidity. Maintain these conditions 48 hours prior to, and during testing.  Do not even bother doing the calcium chloride test if these conditions cannot be met starting two days before the test and right through the end of the test.

One scenario that has been addressed in the new document regarding temperature is testing slabs in spaces that are normally very hot or very cold.  In this case you should not test at “the same temperature and humidity expected during normal use.” For floors intended to be used at high or low temperatures or humidity (such as cold storage rooms), the test site must be within the temperature and humidity range given above, not at the anticipated service temperature or humidity.

 Finally, it is important to understand that the calcium chloride test does not work over all substrates.  Larry Press commented that the new version of F 1869 “clarifies definitively that this method can no longer be used over what is considered lightweight concrete or those surface underlayments - whether thick or thin applications - that are of a gypsum type base, generally used for their properties for fire or sound.”  

 In F 710 you will find the warning, “Floors containing lightweight aggregate...may need  a much longer drying time.”  The aggregate (rocks) in lightweight concrete hold moisture for a long time, so the surface may be fairly dry but the inside is quite damp.  Because the calcium chloride test doesn’t measure moisture more than one inch down into the slab, there has been a history of inaccurate test results over lightweight concrete. The scope of the new version of F 1869 includes the sentence: “This test shall not be used to evaluate the rate of moisture vapor emitted by lightweight concrete floors containing lightweight aggregate.”   I can hear my readers exclaiming “how can we tell?” in unison right about now.  I agree this is a tough one to work with, but it’s important because the worst case scenario is that you do the test, get low results, install the floor and all the extra moisture down below comes to the top and causes a failure.  So begs the question, “Is this lightweight concrete?”  If it can’t be determined for sure, assume it is and go with ASTM F 2170, the Relative Humidity test.  This test measures the moisture inside the slab and is the preferred method for lightweight concrete. If you are not familiar with F 2170, read up on the subject and learn how to do this test for all concrete slabs.  It’s a more accurate prediction of future moisture problems in a slab because moisture moves up.  Many experts in the industry prefer this method and most adhesive and floor covering manufacturers are recommending it.

Another substrate that is widely used is Gypsum, especially in high rise construction.  Unfortunately the calcium chloride test does not work in this case either.  The new F 1869 warns about this, saying “This test shall not be used to evaluate moisture emissions over gypsum concrete.”  Manufacturers of gypsum underlayments and toppings recommend moisture meters for determining whether gypsum is dry.  Again if you are not sure - ask. 

These are some pretty major changes to an old test method so be sure if you are doing testing that you are aware of the changes so your test results will be accurate.