Brick

Arch 1171 Semester 1st

By Terusaw Solomon
Definition
Brick is a block or a single unit of kneaded clay – bearing soil,
sand and lime or concrete material, fire - hardened or air- dried,
used in masonry construction.

The main constituents of brick making clays are

silica (sand) and alumina, but with varying quantities
of chalk, lime, iron oxide and other minor constituents,

Uniqueness
 Size
 Durability
 Workability
 Economical

It is used for building-up

 Exterior and interior walls
 Roofing
 Piers
 Footings and other load bearing structures
Clay

Clay: It is an earthen mineral mass or fragmentary rock capable of mixing with water and forming
a plastic viscous mass which has a property of retaining its shape when molded and dried.

Clay is classified

 China clay (Residual): used for making pottery.

 Transported (Sedimentary) : used for making bricks.

Physical properties of clay

 Plasticity
 Tensile strength
 Texture
 Shrinkage
 Porosity
 Fusibility
 Color after burning
Size

Size of a standard brick (also known as modular brick) is 19 × 9

× 9 cm and 19 × 9 × 4 cm.
When placed in masonry the 19 × 9 × 9 cm brick with mortar
becomes 20 × 10 × 10 cm.

Length of brick = 2 × width of brick + thickness of mortar

Height of brick = width of brick

Weight of a brick is 2 - 4 kg, An indent called frog, 1–2 cm

deep is provided for 9 cm high bricks to
form a key for holding the mortar.
Types

Solid bricks Perforated bricks

Hollow bricks Cellular bricks

Classification Based on Physical & Mechanical Properties

First class bricks

1. These are thoroughly burnt and are of deep red, cherry or copper color.
2. The surface should be smooth and rectangular, with parallel, sharp and straight edges
and square corners.
3. These should be free from flaws, cracks and stones.
4. These should have uniform texture.
5. No impression should be left on the brick when a scratch is made by a finger nail.
6. The fractured surface of the brick should not show lumps of lime.
7. A metallic or ringing sound should come when two bricks are struck against each other.
8. Water absorption should be 12–15% of its dry weight when immersed in cold water for
24 hours.
9. The crushing strength of the brick should not be less than 10 N/mm2.

Uses: First class bricks are recommended for pointing, exposed face work in masonry
structures, flooring and reinforced brick work.
Second class bricks: are supposed to have the same requirements as the first class ones
except that

1. Small cracks and distortions are permitted.

2. A little higher water absorption of about 16–20% of its dry weight is allowed.
3. The crushing strength should not be less than 7.0 N/mm2.
Second class bricks
Uses: Second class bricks are recommended for all important or unimportant hidden
masonry works and centering of reinforced brick and reinforced cement concrete (RCC)
structures.

Third class bricks: are under burnt. They are soft and light-colored producing a dull
sound when struck against each other. Water absorption is about 25 per cent of dry
weight.
Third class bricks
Uses : It is used for building temporary structures.

Fourth class bricks: are over burnt and badly distorted in shape and size and are brittle
in nature.

Uses: The ballast of such bricks is used for foundation and floors in lime concrete and
road metal.

Fourth class bricks

Classification Based on Uses

Common Bricks: is a general multi-purpose unit manufactured

economically without special reference to appearance. These may
vary greatly in strength and durability and are used for filling,
backing and in walls where appearance is of no consequence. Common bricks
Face

Facing Bricks: are made primarily with a view to have good

appearance, either of color or texture or both. These are durable
under severe exposure and are used in fronts of building
walls for which a pleasing appearance is desired.
Facing bricks
Engineering Bricks: are strong, impermeable, smooth, table
molded, hard and conform to defined limits of absorption and
strength. These are used for all load bearing structures.

Engineering brick
Classification Based on Finish
Sand faced Brick: has textured surface manufactured by sprinkling sand on the inner
surfaces of the mold.

Rustic Bricks: has mechanically textured finish, varying in pattern.

Classification Based on Manufacturing

Hand made bricks: These bricks are hand molded.
Sand faced bricks
Machine made: Depending upon mechanical arrangement, bricks are known as
 Wire-cut
 Pressed bricks
 Molded bricks

Classification Based on Manufacturing

Pale Bricks: are under burnt bricks obtained from outer portion of the kiln.
Body Bricks: are well burnt bricks occupying central portion of the kiln.
Arch Bricks: are over burnt also known as clinker bricks obtained from inner portion of the kiln. Rustic bricks
Characteristic of Good Brick

Size and shape: The bricks should have uniform size and plane, rectangular surfaces with
parallel sides and sharp straight edges

Color: The brick should have a uniform deep red or cherry color as indicative of uniformity in chemical
composition and thoroughness in the burning of the brick

Texture and compactness: The surfaces should not be too smooth to cause slipping of mortar.
The brick should have precompact and uniform texture

Hardness and soundness: The brick should be so hard that when scratched by a finger nail no
impression is made. When two bricks are struck together, a metallic sound should be produced.

Water absorption: Should not exceed 20 per cent of its dry weight when kept immersed in
water for 24 hours.

Crush strength: Crushing strength should not be less than 10 N/mm2.

Harmful Substances in Brick
Lime: When a desirable amount of lime is present in the clay, it results in good bricks, but if in
excess, it changes the color of the brick from red to yellow. When lime is present in lumps, it
absorbs moisture, swells and causes disintegration of the bricks.

Water: A large proportion of free water generally causes clay to shrink considerably during
drying, whereas combined water causes shrinkage during burning.

Gravels (stones): gravels do not allow the clay to be mixed thoroughly and spoil the appearance of
the brick.

Organic matters: On burning green bricks, the organic matter gets charred and leave pores making
the bricks porous; the water absorption is increased and the strength is reduced.

Tasting of Bricks

 Dimension Test
 Water Absorption Test
 Compressive Strength Test
Manufacture of Clay Bricks

There are five main processes in the manufacture of clay bricks:

Extraction of the raw material

 Unsoiling
 Digging
 Weathering
Forming processes
 Blending
 Tempering
 Molding
Drying
 Open air
 Artificial
Firing
 Hydration: Water smoking stage
 Oxidation: Carbon is eliminated
 Vitrification: To convert the mass into glass like substance

Packaging and distribution

Defects of Bricks
Over burning of Bricks: Bricks should be burned at temperatures at vitrification occur. However, if the bricks are
over burnt, a soft molten mass is produced and the bricks loose their shape. Such bricks
are not used for construction works.

Under burning: When bricks are not burnt to cause complete vitrification, the clay is not softened because of
insufficient heat and the pores are not closed. This results in higher degree of water absorption
and less compressive strength. Such bricks are not recommended for construction works.

Chuffs: The deformation of the shape of bricks caused by the rain water falling on hot bricks is known as chuffs.

Efflorescence: This defect is caused because of alkalis present in bricks. When bricks come in contact with
moisture, water is absorbed and the alkalis crystalize. On drying grey or white powder patches
appear on the brick surface. This can be minimized by selecting proper clay materials for brick
manufacturing, preventing moisture to come in contact with the masonry, by providing
waterproof coping and by using water repellent materials in mortar and by providing damp proof
course.

Checks or Cracks: This defect may be because of lumps of lime or excess of water. In case of
the former, when bricks come in contact with water, the absorbed water reacts with lime
nodules causing expansion and a consequent disintegration of bricks, whereas shrinkage and burning cracks
result when excess of water is added during brick manufacturing.
Joints

 The square recessed (raked) joints articulate the brickwork by featuring the joint, but these should
only be used with high-absorption bricks under sheltered conditions; furthermore, the recess should be limited to a
maximum depth of 6 mm.

 The struck or weathered joint also accentuates the light and shade of the brickwork while, as a tooled joint, offering
good weather resistance in all grades of exposure.

 If the visual effect of the joint is to be diminished, the flush joint may be used, but the curved
recessed (bucket-handle) joint, which is compressed by tooling, offers better appearance and weathering
properties.
Clay Cladding
Clay Pavements
Thank You!