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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You must be logged in to post a comment. 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. During the test, 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 d475 comparing a minimum of three test results when there are changes in the manufacturing of a specific pre-qualified geotextile. The M specification does not include the bead size. 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. The values in inch-pound units are provided for information only.

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 f4751 begun. 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 each laboratory for testing. Geotextiles from different manufacturers or with different nominal unit weights are considered different products. What is the intent here?

A 40 Sieve has a corresponding bead size of. The most common way this property is reported is: Unfortunately, AOS is reported in a confusing manner. 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.

The Solution Always resist the temptation to add the millimeter bead size if the specification only lists the US Sieve number and vice-versa. Competent statistical assistance is recommended for the investigation of bias.

How is one to know for sure?

While we believe this to be un-intentional, if interpreted as written, this specification now requires a maximum bead size of. Inch-pound units awtm the technically correct name for the customary units used in the United States.

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Thanks for reading our blog! Or does he want a fabric with no larger than 60 Sieve number? However, it is our belief that specifiers should list only the bead size to eliminate any doubt as to the intent of the specification. Link to Active This link will always route to the current Active version of the standard.

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

The Devil is in the Details The most common way this property is reported is: Leave a Reply Cancel reply You must be logged in to post a comment. The test is carried out on a range of sizes of glass beads.


For example, a 60 Sieve has a corresponding bead size of. Current estimates of precision, between laboratories, have been established. The problem lies in the relationship between the U. Mesh or Sieve number and the correlating millimeter bead size. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

The attached specification is a perfect example of how the relationship between sieve number and bead size can really create confusion. A minimum of three test results must be compared with all three satisfying the established correlation.

SI units is the technically correct name for the system of metric units known as the International System of Units.

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

In the case of the attached specification it should read: Historical Version s – view previous versions of standard. Leaving the intent of a specification to a geotextile company or contractor is certainly not what most specifiers have in mind.

The amount of beads retained by the geotextile sample is then measured. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.

It is the intent of this test method to confirm the equivalency of the Method B results before permitting the use of this alternative.