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Comparing specs

News, Q&A: GMA Techline | April 1, 2009 | By:

Subject: Comparing specs — I want to know how can I compare specification values of ASTM with ISO??

I sell products tested with ASTM methods, but some clients give me an ISO specification. I want to know which product fits their requirements. (Claudia, Mexico)

Reply: You ask an excellent question and one that we have been fully involved in for about five years. The two groups, ASTM and ISO, act independently from one another although ASTM does have liaison people attending the ISO meetings as observers.

That said, the test methods are sometimes on different topics (ISO has a geomembrane water permeability test while ASTM has a vapor transmission test.) and sometimes on the same topic but with very different approaches (geotextile opening size where ASTM does dry sieving and ISO does wet sieving). Perhaps the most perplexing is when the two groups have very similar test methods to one another but just vary a small detail such as specimen size, strain rate, or probe dimension.

All of these differences mean that one must do the test by both methods and develop a correlation for subsequent use. It is a royal pain to do so and George Koerner at GSI is regularly involved. Perhaps some day we will publish what information we have but for now you simply must do the requisite testing yourself.

Sorry, but that’s the current (very unsatisfactory ) status.

Robert M. Koerner, Ph.D., P.E., NAE; E-mail:

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