1. Scope* 1.1 This test method covers a procedure for determining the relative resistance of concrete (including concrete overlays and impregnated concrete) to abrasion under water (see Note 1). This procedure simulates the abrasive action of waterborne particles (silt, sand, gravel, and other solids). NOTE 1—Other procedures are available for measuring abrasion resistance of concrete surfaces not under water. These include Test Methods C418, C779/C779M, and C944. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 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 and health practices and determine the applicability of regulatory limitations prior to use. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure.2)