ASTM D4751-21A

1.1 These test methods cover the determination of the apparent opening size (AOS) of a geotextile either by dry-sieving glass beads through a geotextile (Methods A1 and A2) or by using a capillary porometer (Method B).

1.2 Method B will not be used in lieu of Method A unless the pre-qualification procedure specified in this standard is followed.

1.3 These test methods show the values in both SI units and inch-pound units. SI units is the technically correct name for the system of metric units known as the International System of Units. Inch-pound units is the technically correct name for the customary units used in the United States. The values in inch-pound units are provided for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.