ASTM C1634-17 + Redline

Note 1: Specification C55 addresses concrete building brick used in non-facing, utilitarian applications (previously referred to in earlier editions of Specification C55 as Grade S—for general use where moderate strength and resistance to frost action and moisture penetration are required). This specification differs from Specification C55 in that it includes expanded consideration for properties of concrete brick used in facing applications and other exposures (previously referred to in earlier editions of Specification C55 as Grade N—for use as architectural veneer and facing units in exterior walls and for use where high strength and resistance to moisture penetration and severe frost action are desired).