GeoTesting Express is a provider of Geosynthetic Testing Services – ASTM D,Standard Test Method for Determining Apparent Opening Size of a Geotextile. Apparent Opening Size (ASTM D). • The ASTM method also called as the dry method. The ASTM method, also called as the dry method uses glass beads. The U.S.A adopted the Apparent Opening Size (AOS) method (Test Method ASTM D 99a) in This test method, although similar to.

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AOS (ASTM D-4751) – A Straightforward Method a Confusing Result

The attached specification is a perfect example of how the relationship between sieve number and bead size can really create confusion. How is one to know for sure? Does the specifier want a fabric that will not pass any larger than a. Geotextiles from different manufacturers or with different nominal unit weights are considered asfm products.

The values in inch-pound units are provided for information only. Always resist the temptation to add the millimeter bead size if the specification only lists the US Sieve number and vice-versa.

As a minimum, the two parties should take a group of test specimens that are homogeneous as possible and that are from a lot of material of the type in question.

The test specimens should then be randomly assigned in equal numbers to astk laboratory for testing. During the d475, spherical, solid glass beads are dry sieved through a geotextile for a specified time and at a specified frequency of vibration. The correlation should be confirmed for a particular product by comparing a minimum of three test results when there are changes in the manufacturing of a specific pre-qualified geotextile.


However, it is our belief that specifiers should list only the bead size to eliminate any doubt as to the intent of the specification.

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It is the intent of this test method to confirm the equivalency of the Method B results before permitting the use of this alternative. The most common way this property is reported is: Mesh or Sieve number and the correlating millimeter bead size. Historical Version s – view previous versions of standard.

The Solution Always resist the temptation to add the millimeter bead size if the specification only lists the US Sieve number and vice-versa. Thanks for reading our blog! Or does he want a fabric with no larger than 60 Sieve number?

What is the intent here? This test method is used to indicate the apparent opening size in a geotextile, which reflects the approximate largest opening dimension available for soil to pass through. The Devil is in the Details The most common way this property is reported is: Inch-pound units is the technically correct name for the customary units used in the United States.

If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results in the light of the known bias. Current estimates of precision, between laboratories, have been established.

Laboratories electing the use of Method B must first determine any bias that exists between the two methods and document a reliable correlation in accordance with this test method.

For example, a 60 Aztm has a corresponding bead size of. The M specification does not include the bead size. A minimum of three test results must be compared with all three satisfying the established correlation. The amount of beads retained by the geotextile sample is then measured.


C4751 problem lies in the relationship between the U. While we believe this to be un-intentional, if interpreted as written, this specification now requires a maximum bead size of. Referenced Documents purchase separately The v4751 listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM D – 16 Standard Test Methods for Determining Apparent Opening Size of a Geotextile

Link to Active This link will always route to the current Active version of the standard. Leave a Reply Cancel reply You must be logged in to post a comment.

A 40 Sieve has a corresponding bead size of. You must be logged in to post a comment. Unfortunately, AOS is reported in a confusing manner. The test is carried out on a range of sizes of x4751 beads.

Leaving the intent of a specification to a geotextile company or contractor is certainly not what most specifiers have in mind. Competent statistical assistance is recommended for the investigation of bias. In the case of the attached specification it should read: SI units is the technically correct name for the system of metric units known as the International System of Units. It is the responsibility of the e4751 of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

The average results from the two laboratories should be compared using Students t -test for unpaired data and an acceptable probability level chosen by the two parties before the testing is begun.