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Apparent opening size (ASTM D4751) for geotextiles

February 1st, 2014 / By: / Drainage Materials, GMA Techline

RE: Apparent opening size (ASTM D4751) for geotextiles
Our specification calls for a geotextile with an AOS of #50 U.S. sieve (0.3mm). I understand that unlike the rest of the technical property values, AOS is specified by the maximum value (i.e., MaxARV not MARV). Please advise.

Does it mean that I can approve any geotextile with an AOS of less than 0.3mm? Are there any range or guidelines for specifiers? Thanks.

(Jim | Illinois)

Reply: You are precisely correct. AOS is indeed MaxARV. Your AOS numeric value will have to be less than 0.3mm. Do watch out, however, because the associated U.S. sieve number will now increase in sieve number—i.e, a #70 or #100 sieve number (which is a finer mesh than a #50) will be required.

Awkward isn’t it?

P.S. You take care of that Chicago water now since my daughter, son-in-law, and two grandchildren drink it!

Bob Koerner | GMA Techline

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