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 units 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).

Note 2: Concrete facing brick and other solid concrete masonry facing units covered by this specification are made from lightweight or normal weight aggregates, or both.

Note 3: When particular features are desired, such as density classification, high compressive strength, surface textures for appearance or bond, finish, color, fire resistance, insulation, acoustical properties, or other special features, such properties should be specified separately by the purchaser. Suppliers should be consulted as to the availability of concrete facing brick and other concrete masonry facing units having the desired features.