Masonry Magazine July 1978 Page. 13
NCMA-TEK
An Information series from National Concrete Masonry Association
96
Special Shapes and Sizes for
Reinforced Concrete Masonry
Introduction
The use of reinforced masonry construction predates that of reinforced concrete. Where early uses of this type of construction were mainly special applications such as for accommodation of earth pressures and the like, reinforced masonry has now become standard practice in those localities where design loads require structural properties exceeding those which can be economically obtained with non-reinforced masonry. In areas where high wind and seismic forces are likely to occur, for example, reinforced masonry is required and is the standard for masonry construction. This type of construction consists of masonry, steel reinforcement embedded in grout and so placed that the masonry, steel and grout act together to provide substantially increased resistance to applied loads and forces.
Reinforced concrete masonry walls may be composed of single or multiple wythes. Single wythe walls are built of hollow units with reinforcement and grout placed in some or all cores of the block. Multi wythe walls are usually built similar to cavity walls, two wythes of hollow and (or solid units) with a cavity between-with steel reinforcement and grout placed in the cavity.
Grout
Grout is a mixture of cement, aggregate and sufficient water to permit the mixture to flow readily, without segregation, into cores or cavities in masonry. Proportions of constituent materials of grout are given in ASTM Standard C-476 "Specifications for Mortar and Grout for Reinforced Masonry." Two methods of grout placement are in general use: (1) low lift grouting, where the grout is placed in lifts up to scaffold height, approximately four feet (1.2m); (2) high lift grouting, where grout is placed in story- height or approximately 8-foot (2.4m) high lifts. With the high-lift grouting method, clean-out openings are required at the bottom of each grout space containing reinforcement. Clean-out openings are generally made by removing all or a portion of the face shell of certain block in the first course of masonry. A special unit with scores or notches is sometimes used to permit easy removal of part of a face shell for clean-out openings.
1978 National Concrete Masonry Association