BRICKS
Standard sizes are 190 x 90 x 40 mm, with mortar the size comes out to be 200 * 100 x 50 mm
However, the old size of * x *giving masonry of rxa x are still used in many parts of
India.
Clay suitable for making bricks contain
Alumina -20 to 30% is desirable
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Silica - 50 to 60% is desirable
Lime - 5% is desirable
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Iron oxide-5 to 6%
Magnesia- A small quantity only
Pebbles, vegetable and organic matter, excess lime, iron pyrites, sulphates of calcIum and potassium
are harmful.
Manufacture of bricks involves preparation of clay, moulding, drying and burning processes.
1. Preparation of clay: It involves unsoling, digging, cleaning, weathering, blending and
tempering: pug mills are used tor tempering
2. Moulding: t may be by hand moulding or by machine moulding
. Drying: lt may be by natural dryıng or by artificial dryıng
. Burning: t may be in clamps or in kilns. Intermittent and continuous kilns are used depending
upon the demand in the locality. Bull's trench kiln, Hoffman' s kiln and Tunnel kilns are the
continuous kilns.
Classification of Bricks
1. Based on strength, bricks are classified as class 5.5, 5.0, etc. to mean compresSIve strength is 3.5
Nm, 5.0 Nmr, etc. Each class 1S subdivided into A and B on the basis of tolerances in sizes.
2. However, in practice the bricks are classified as first, second, third and fourth class.
The following types of special bricks are also available in markets:
(1) High duty bricks; (2) Perforated bricks; (3) Hollow bricks; (4) Specially shaped bricks; (5) Fire
clay bricks; (6) Paving bricks; (7) Facing bricks; (8) Soling bricks; (9) Sewer bricks.
Tests on Bricks
1. Field tests: Observing size, colour, structure, hardness by scratching, sound test by striking two
bricks with each other and strength test by dropping from a height of I m
2. Laboratory tests conducted on bricks are
(a) Crushing strength test; (b) Absorption test; (c) Shape and size test, (d) EfMorescence test.
Requirement of good bricks are:
Compressive strength> 3.5 Nmm
Water absorption> 20%
Variation in sizes should be within the tolerances prescribed by code. They should not shoW white
patches when soaked in water for 24 hours.
lo meet local requirement, the following materials substi tute tor bricks
. Stabilized soil bricks; 2. Sand + lime blocks; 3. Fly ash bricks; 4. Concrete blocks.
CLAY PRODUCTS
Apart from bricks, the following clay products are used by burning, glazing and vitrifying clay
() Tiles; (2) Terracotta; (3) Earthenw are and (4) Stoneware.
1. Tiles Difierent types of tiles used are roofing tiles, ceiling iles,.ridgs.les, Meoçing, and, wall tiles,
drain tiles.
The following roofing tiles are used in India:
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(a) Half round tiles; (b) Corrugated tles: (C) Pan tiles; (d) Allahabad tiles and (e) Mangalore tiles.
Ceiling tiles are flat tiles provided under roofing tiles to give good appearance when viewed from
below. Ridge tiles are specially shaped tiles to cover ridges in sloping roofs. Clay tiles, glazed tiles
and vitrified tiles are used for tlooring and to give finishing to walls. Drain tiles are laid in
waterloggcd areas to drain the water
2. Terracotta Terracotta means baked earth. It may be manufactured in different colours also. There
are two types of terracotta, viz. porous terracotta and polished terracotta. They are used for making
art pieces and lavatory fittings.
3. Earthenware It is a type of terracotta in which the moulded product is burnt at low temperature to
get semi-vitri fied surface. These products are used for making cheap lavatory fittings and drain
pipes.
4. Stoneware These are the pipes manutactured from refractory clays to which ground ilint and
crushed pottery are added and ground. During grinding pigments are also added. They are
produced under pressure and then burnt at high temperature. They are used for making wash-basins,
gully traps, jars and sewer pipes.
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