MASONRY - Materials for Civil and Construction Engineers - page 311

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Clay Bricks
Clay bricks are small, rectangular blocks made of fired clay. Clays for brick
making vary widely in composition from one place to another. Clays are
composed mainly of silica (grains of sand), alumina, lime, iron, manganese,
sulfur, and phosphates, with different proportions. Bricks are manufactured
by grinding or crushing the clay in mills and mixing it with water to make
it plastic. The plastic clay is then molded, textured, dried, and finally fired.
Bricks are manufactured with different colors, such as dark red, purple, brown,
gray, pink, or dull brown, depending on the firing temperature of the clay
during manufacturing. The firing temperature for brick manufacturing
varies from 900 ° C to 1200 ° C (1650 ° F to 2200 ° F). Clay bricks have an average
density of (125 pcf).
Bricks are used for different purposes, including building, facing and aes-
thetics, floor making, and paving. Building bricks ( common bricks ) are used
as a structural material and typically are strong and durable. Facing bricks
are used for facing and aesthetic purposes and are available in different sizes,
colors, and textures. Floor bricks are used on finished floor surfaces and are
generally smooth and dense and have high resistance to abrasion. Finally,
paving bricks are used as a paving material for roads, sidewalks, patios, dri-
veways, and interior floors. Paving bricks are available in different colors,
such as red, gray, or brown, and typically they are abrasion resistant and could
be vitrified.
Absorption is one of the important properties that determine the dura-
bility of bricks. Highly absorptive bricks can cause efflorescence and other
problems in the masonry. According to ASTM C67 absorption by 24-hour
submersion, absorption by 5-hour boiling, and saturation coefficient are
calculated as:

8.1.2

2 Mg/m 3

W s24 - W d

1 2

Absorption by 24-hour submersion % = * 100

1 2

(8.5)

W d

W b5 - W d

1 2

Absorption by 5-hour boiling % = * 100

1 2

(8.6)

W d

1 W s24 - W d 2

Saturation coefficient =

(8.7)

1 W b5 - W d 2

where

W d = dry weight of specimen,

weight after 24-hour submersion in cold water, and
weight after 5-hour submersion in boiling water.

W s24 = saturated

W b5 = saturated

Clay bricks are very durable, fire resistant, and require very little main-
tenance. They have moderate insulating properties, which make brick houses
cooler in summer and warmer in winter, compared with houses built with
other construction materials. Clay bricks are also noncombustible and poor
conductors.