5.1 Thickness is one of the basic physical properties used to control the quality of permanent rolled erosion control products. Thickness values may aid in the calculation of other permanent rolled erosion control product parameters. Thickness however is not generally an indication of field performance and generally should not be used in specifications. This test method is developed to aid manufacturers, designers, and end users in comparing the thickness of permanent rolled erosion control products through the use of an accepted ASTM standard.

5.2 The thickness of permanent rolled erosion control products may vary considerably depending on the pressure applied to the specimen during measurement. Where observed changes occur, thickness decreases when applied pressure is increased. To minimize variation, specific sample size and applied pressure are indicated in this test method to ensure all results are comparable.

5.3 This test method may be used for acceptance testing of commercial shipments of permanent rolled erosion control products, but caution is advised since information on between-laboratory precision is incomplete. Comparative tests in accordance with 5.3.1 may be advised.

5.3.1 In case of a dispute arising from differences in reported test results when using this test method for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens that are as homogeneous as possible and that are formed from a lot of material of the type in question. The test specimens should be randomly assigned in equal numbers to each laboratory for testing. 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. If bias is found, either its cause must be found and corrected or the purchaser and supplier must agree to interpret future tests in light of the known bias.

Note 1-The user should be aware that the compressibility of the materials, their rebound characteristics, and the like will also affect the thickness of the permanent rolled erosion control products following the time they are rolled up on rolls, shipped, and stored.