Is 3 Pounds Too Low?
In a previous article, I discussed the use of the moisture dome test, ASTM 1869-98, as well as a research study by two California engineering firms in an effort to defuse the litigation attached to concrete quality by using the dome test.
That study, along with one recently published in Concrete Construction magazine, points out the variations in test results. The article in Concrete Construction reports on the results of 232 laboratory tests and 144 field tests conducted on on-grade slabs and elevated slabs. The findings of the authors, Bruce A. Suprenant and Ward R. Malisch, appear to conclude that the industry-accepted maximum tolerance of 3 pounds per 1,000 square feet in 24 hours is unreasonably low.
In a separate article titled “Effect of Water Vapor Emissions on Floor Covering Adhesives,” the authors’ findings on the test for pull-off strength of adhesives are enlightening. Because of variable test results with each adhesive, they could not identify a water-vapor emission rate below which a secure bond could be achieved. So, based on their tests, a secure bond is a function of the adhesive properties and water-vapor emission rates. It is also suggested in the article that adhesive manufacturers could assist by providing data that relates a quantitative measure of bond strength to the vapor emission rates for their product, i.e. 3, 4, or 5 pounds, but currently, very few manufacturers will provide that information.
The question is raised: When the floor hasn’t reached the targeted moisture vapor emission rate for floor covering installation, is the problem in the floor or in the testing?
The article also raises the problem of dome testing variations from both the use of varying test kits, and the fact that in ASTM F1869-98 the formula for calculating the vapor emission rate differs from that of kit suppliers. Tests showed an 10% increase in the emission rate value, with no subsequent maximum rate increase by flooring manufacturers.
The 3-pound requirement was mandated by the Rubber Manufacturers Association decades ago for the purpose of determining the safety factor for rubber, which does not have the permeability of VCT or the felt backing benefits of sheet vinyl.
It must follow that the adhesives in use must bear a degree of responsibility, yet seldom are they the object of scrutiny. At the recent Surfaces 2000 Trade Show in Las Vegas, NV, a committee member from the Floor Covering Adhesive Manufacturers Association stated that the association now feels that substantial progress has been made in the testing protocol. I would hope that the FCAMC includes alkalinity requirements, as the government does, in their purchasing guidelines.
In an article published in Western Floors magazine (now National Floor Trends) in September 1995 titled “Moisture Puts All Floor Covering At Risk,” I said that it was important to use premium adhesives, as there are many grades available. I said then that, if the adhesive industry adopted standards similar to ANSI standards for ceramic tile adhesives, it would help our industry immeasurably. This is still my belief.
Room temperature and humidity, which drives the vapor, has not been discussed often. This data is readily available from the government, as well as in the Hydrologic Cycle and Moisture Migration manual from W.R. Meadows Inc.
It has been noted that dome testing should be done at the same temperature and humidity as the room would be during normal use. Of course, normal construction practices make this virtually impossible.
In conclusion, it would appear that the engineers and consultants on the concrete side of the industry are leading the way in water-vapor transmission and its effects on adhesives.