Page 50 - Design of Reinforced Masonry Structures

MASONRY UNITS: APPLICATIONS, TYPES, SIZES, AND CLASSIFICATION 2.3

FIGURE 2.1 Common definitions used to describe masonry units. (Courtesy: BIA.)

Materials from which masonry units can be made include clay or shale, concrete, cal-
cium silicate (or sand lime), stone, and glass. The two major types of masonry units used
in general masonry construction are (1) clay building brick and (2) concrete building brick
and blocks. Both types of units can be either solid or hollow. Units are made hollow by
providing voids that extend through the full height of the units. These voids are commonly
referred to as cores or cells, which are distinguished by their cross-sectional areas. Cores
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1
are void spaces having cross-sectional areas less than 1 ⁄ 2 in. , whereas a cell is a void space
having a cross-sectional area larger than that of a core. Voids that extend through only
part of the height are called frogs. Essentially, frogs are indentations in one bed surface of
bricks manufactured by molding or pressing. Frogs may be in the form of shallow troughs
or a series of conical shapes. Panel frogs are limited to a specified depth and a specified
distance from a face. Deep frogs are frogs that are deeper than ⁄ 8 in., and must conform
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to the requirements for coring, hollow spaces, and void area of the applicable standard.
Indentations over the full height of the ends of units are also referred to as frogs, and the
units are said to have frogged ends. Concrete masonry units with frogged ends are produced
by extending the face shells on one or both sides as required [2.10]. Various definitions are
illustrated in Fig. 2.1.
In construction, masonry units are assembled together with mortar joints in between
them. Mortar is applied to the top and bottom horizontal surfaces of units, which are
referred to as bedding areas. The horizontal layer of mortar on which a masonry unit is laid
is called the bed joint. Most masonry units are rectangular in shape, and defined by their
three dimensions: width, height, and length, in that order (Fig. 2.2). Masonry units used
in wall construction are rectangular in shape, which are laid with their long dimensions
oriented horizontally in the plane of the wall, and height perpendicular in the plane of the