Calcium chloride testing (ASTM F-1869-16) was once considered standard practice in America for determining moisture levels in concrete floors, and was written into the American Society for Testing and Materials (ASTM) Standard.
However, over the years many of the floors that were originally assessed as acceptable with this test were later found to have developed moisture problems. As a result it has fallen out of favor with flooring installers and has now been removed from the ASTM Standard for testing lightweight concrete. It is also no longer permitted under AS 1884-2012.
The test is designed to measure the moisture vapor emission rate (MVER) of a slab, which makes it similar in principle to the surface-mounted insulated hood test.In this test the moisture is absorbed in a small mound of calcium chloride salt, which is placed on the concrete surface and sealed with a plastic dome.
The increase in weight of the salt is used to calculate the relative humidity in the slab. The biggest problem with the test is that it can only measure the rate of moisture loss in the very top of the slab, and can't take account of the higher concentrations deeper down.
It also tends to underestimate moisture levels that are high and overestimate levels that are low. For decades, calcium chloride testing has been used to determine the suitable moisture content of poured concrete slabs when applying resilient floor coverings.
The standard for performing the calcium chloride test has seen many changes over the years. The initial testing only called for determining qualitative results but it soon became apparent that a more quantitative approach that provided more than just someone’s opinion was needed for threshold decisions.
Various changes were proposed but the calcium chloride method continued to be unwieldy, uncertain in results and inefficient in terms of both time and materials. Clearly a more user-friendly, accurate means of determining concrete moisture would be welcomed by the entire resilient floor covering industry.
Since 2002, ASTM F2170 In-Situ Relative Humidity testing has been replacing calcium chloride as the preferred method for concrete moisture determination. And in 2010 the ASTM committee changed the F1869 Calcium Chloride standard to specifically disallow calcium chloride testing for all lightweight aggregate concrete as results which had long been suspected as inadequate were finally confirmed.
If RH testing using ASTM F2170 was not here to take its place, the entire industry certainly would have been thrown into turmoil. This recent decision clearly demonstrates the need for having an alternative to the antiquated F1869 Calcium Chloride testing standard.
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