GRADE SW is brick designed to withstand exposure
to below-freezing temperatures in a moist climate like that
of the northern regions of the United States.
GRADE MW is brick designed to withstand
exposure to below-freezing temperatures in a drier
climate than that mentioned in the previous paragraph.
GRADE NW is brick primarily intended for
interior or backup brick. It may be used exposed;
however, it can only be used in regions where no frost
TYPES OF BRICKS
Brick masonry units may be solid, hollow, or
architectural terra cotta. All types can serve a
structural function, a decorative function, or a
combination of both. The various types differ in their
formation and composition.
Building brick, also called common, hard, or
kiln-run brick, is made from ordinary clay or shale and
is fired in kilns. These bricks have no special shoring,
markings, surface texture, or color. Because building
bricks are generally used as the backing courses in
either solid or cavity brick walls, the harder and more
durable types are preferred.
Face brick is better quality and has better
durability and appearance than building brick.
Because of this, face bricks are used in exposed wall
faces. The most common face brick colors are various
shades of brown, red, gray, yellow, and white.
Clinker brick is overburned in the kiln. Clinker
bricks are usually rough, hard, durable, and sometimes
irregular in shape.
Pressed brick is made by a dry-press process,
rather than by kiln firing. Pressed bricks have regular,
smooth faces, sharp edges, and perfectly square
corners. Ordinarily, they are used like face brick.
Glazed brick has one surface coated with a white
or colored ceramic glazing. The glazing forms when
mineral ingredients fuse together in a glasslike coating
during burning. Glazed bricks are particularly suited
to walls or partitions in hospitals, dairies, laboratories,
and other structures requiring sanitary conditions and
ease of cleaning.
Fire brick is made from a special type of clay. This
clay is very pure and uniform and is able to withstand
the high temperatures of fireplaces, boilers, and
similar constructions. Fire bricks are generally larger
than other structural bricks and are often hand-molded.
Cored bricks have ten holestwo rows of five
holes each-extending through their beds to reduce
weight. Walls built from cored brick are not much
different in strength than walls built from solid brick.
Also, both have about the same resistance to moisture
penetration. Whether cored or solid, use the more
available brick that meets building requirements.
European brick has strength and durability about
equal to U.S. clay brick. This is particularly true of the
English and Dutch types.
Sand-lime brick is made from a lean mixture of
slaked lime and fine sand. Sand-lime bricks are
molded under mechanical pressure and are hardened
under steam pressure. These bricks are used
extensively in Germany.
STRENGTH OF BRICK MASONRY
The main factors governing the strength of a brick
structure include brick strength, mortar strength and
elasticity, bricklayer workmanship, brick uniformity,
and the method used to lay brick. In this section, well
cover strength and elasticity. Workmanship is
covered separately in the next section.
The strength of a single brick masonry unit varies
widely, depending on its ingredients and
manufacturing method. Brick can have an ultimate
compressive strength as low as 1,600 psi. On the other
hand, some well-burned brick has compressive
strength exceeding 15,000 psi.
Because portland-cement-lime mortar is normally
stronger than the brick, brick masonry laid with this
mortar is stronger than an individual brick unit. The
load-carrying capacity of a wall or column made with
plain lime mortar is less than half of that made with
portland-cement-lime mortar. The compressive
working strength of a brick wall or column laid with
plain lime mortar normally ranges from 500 to 600 psi.
For mortar to bond to brick properly, sufficient
water must be present to hydrate the portland cement
in the mortar completely. Bricks sometimes have high
absorption rates, and, if not properly treated, can
suck the water out of the mortar, preventing
complete hydration. Here is a quick field test to
determine brick absorptive qualities. Using a
medicine dropper, place 20 drops of water in a l-inch
circle (about the size of a quarter) on a brick. A brick
that absorbs all the water in less than 1 1/2 minutes
will suck the water out of the mortar when laid. To
correct this condition, thoroughly wet the bricks an