This Presentation focuses on Stones, Bricks and Tiles which is under the category of Civil Engineering Materials.

1. Unit-I
Stones, Bricks and Tiles

52. BRICKS

54. Composition of a Good Brick

60. Properties of Bricks
The following are the required properties of good bricks:
(i) Colour: Colour should be uniform and bright.
(ii) Shape: Bricks should have plane faces. They should have sharp and true right angled corners.
(iii) Size: Bricks should be of standard sizes as prescribed by codes.
(iv) Texture: They should possess fine, dense and uniform texture. They should not possess
fissures, cavities, loose grit and unburnt lime.
(v) Soundness: When struck with hammer or with another brick, it should produce metallic sound.
(vi) Hardness: Finger scratching should not produce any impression on the brick.
(vii) Strength: Crushing strength of brick should not be less than 3.5 N/mm2. A field test for
strength is that when dropped from a height of 0.9 m to 1.0 mm on a hard ground, the brick
should not break into pieces.
(viii) Water Absorption: After immersing the brick in water for 24 hours, water absorption should
not be more than 20 per cent by weight. For class-I works this limit is 15 per cent.

61. (ix) Efflorescence: Bricks should not show white patches when soaked in water for 24 hours and
then allowed to dry in shade. White patches are due to the presence of sulphate of calcium,
magnesium and potassium. They keep the masonry permanently in damp and wet conditions.
(x) Thermal Conductivity: Bricks should have low thermal conductivity, so that buildings built
with them are cool in summer and warm in winter.
(xi) Sound Insulation: Heavier bricks are poor insulators of sound while light weight and hollow
bricks provide good sound insulation.
(xii) Fire Resistance: Fire resistance of bricks is usually good. In fact bricks are used to encase
steel columns to protect them from fire.

62. Compressive Strength
Generally, bricks have high compressive strength in the range of 5.5 N / mm2 to 140 N/mm2. If the
crushing strength of the bricks is less than 3.5 N/mm2 it must not be used. A field test about
strength of the bricks is to fall the brick from a height of 1 meter and it must not break in to pieces.

63. Water Adsorption Properties of Bricks
In such heavy rainfall areas, it is therefore recommended, to use cavity walling system. In this
system the exterior wall is constructed in such a way that between the two parallel layers of bricks,
a space or cavity is introduced that not only increase the insulation properties but also avoids the
surface water to get percolated towards inside.
The water absorption of a perfect brick should not exceed 20%

64. Qualities of a good brick:
Brick Earth(Clay): It should be free from pebbles (kankars), stones, organic matter, saltpeter (potassium
nitrate) and other harmful chemical, as it makes poor quality of bricks.
Size of a Brick: A good brick should have a uniform size with plain and rectangular surfaces and
should be parallel from the sides
Tolerance : 3mm in length and 1.5mm in Width
Shape: The shape of a brick should be uniform. The edges of a good brick should be sharp, straight and at
a right angle.

65. Color: There are wide range of colours, such as red, white, grey, brown, purple, blue and black,
along with some intermediate shades. the colour is influenced by the chemical constitution of the
clay, its temperature while burning.
Frog in Brick: A good quality brick should have a proper frog, so that the mortar can be properly
filled in the frog. The size of the frog should be 100 mm in length, 40 mm in width and 10 mm in
depth.
Texture and Compactness: There is a considerable variation in the texture of bricks. The good
bricks should have a pre-compacted and uniform texture. The surfaces of brick should not be too
smooth to cause slipping of mortar. A fractured surface should not show cracks, holes, grits or
lumps of lime.

66. Compressive Strength: The compressive strength of brick depends upon the composition of the
clay and degree of burning. As per ‘National Building Code of India’ (1983), the compressive
strength of brick should be of minimum 3.5 N/mm2 i.e. 35 Kg/cm2
Hardness: Bricks should be sufficiently hard. No impression should be left on the surface of a
brick when it is scratched with fingernails.
Water Absorption: Water absorption of a good brick should not exceed 20 % of its dry weight
when immersed in water for 24 hours.
Soundness: When the brick is struck with a hammer or with another brick, it should give a
metallic ringing sound.

67. First Class Bricks:
Size: perfect in shape 19 x 9 x 9 cm, with sharp edges
Color: good
Ability: free from cracks, chips and pebbles
Water absorption: not more than 20%
Compressive strength: 140kg/cm2
USE: Excellent for all types of construction in the exterior walls. They are also suitable for
flooring.
Classifications of Bricks
Second Class Bricks:
Size: Slight irregular in shape
Color: good
Ability: Fractured surfaces
Water absorption: 22% - 24%
Compressive strength: 70 kg/cm2
USE: For exterior work when Plastering is to be done. And can also be used for interior works
but they may not be used for flooring.

68. Third Class Bricks:
Size: No uniformity in shape and size
Color: Reddish yellow
Ability: Fractured surfaces
Water absorption: 24% - 28%
Compressive strength: 35 -70 kg/cm2
USE: They are used mostly in the ordinary type of construction and in dry situations.
Fourth Class Bricks:
Size: Irregular in shape
Color: Dark in color
Ability: Fractured surfaces
Water absorption: low water absorption
Compressive strength: 150 kg/cm2
USE: despite their high strength and low water absorption, they are not used in building
construction because of their irregular size and shape due to over burning.

69. Manufacturing process of Bricks
Preparation of Soil
Moulding
Drying
Burning

70. Preparation of Soil
Removal of Top Soil: The removal of top soil involves the loose materials present at the top of
the soil for a depth of about 200 mm. These materials should be removed as they contain a lot of
impurities and are not used in the preparation of bricks.
Digging and Spreading: After digging the soil for about 200 mm, the soil is spread
on the level ground, and the heaps of clay are about 600 to 1200 mm.
Cleaning: After spreading the soil on the ground, it should be cleaned of stones, vegetable matter,
pebbles, etc… If excess non-clay materials are present, the clay should be washed and screened.
This whole process will become expensive and clumsy. The lumps in soil should be crushed into a
powder form.
Weathering: The soil is then exposed to the atmosphere for softening for a few weeks depending
on the nature of the soil, which imparts plasticity and strength to the soil.
Blending: To increase the quality of soil, additionally, sandy or calcareous clays may be added in
suitable proportions along with coal, ash, etc. and the whole mass is mixed uniformly with water.
Tempering: After adding the sufficient quantity of water, the soil is kneaded under the feet of men
or cattle to make it stiff and homogeneous. In general, for handmade bricks, the soft plastic clay
could be prepared by using about 25 to 30% water. For making superior bricks on a large scale of
about 20,000, the earth is tempered in a pug mill.

71. Moulding of Bricks
Bricks are made in metric sizes called modular bricks, as prescribed by the Bureau of Indian
Standards. Nominal size of the bricks is 20cm X 10cm X 10cm, which include the thickness of the
mortar and the actual size of modular brick is 19cm X 9cm X 9cm.
A brick mould is a rectangular box of steel or wood, which is open at the top and bottom of the
box and inside dimensions of the mould are 20cm X 10cm X 10cm. Moulding of bricks can be done
using either hand or machine.
Hand Moulding There are two types in hand moulding, i.e. ground moulding and table moulding.
In this type, bricks are moulded manually and preferred where only a small quantity of bricks is
needed.
Ground Moulding: The process of moulding bricks on the ground manually by labour is called
ground moulding. On an average, a moulder can mould about 750 bricks per day. When the bricks
have dried sufficiently, they are moved to the drying shed and placed in an orderly manner.
Table Moulding: This moulding is done on a table of size 2m X 1m X 0.7m instead of on the ground. This table
moulding process is almost similar to ground moulding expect for some minor changes.
Machine Moulding
Moulding machines are used when a large scale of bricks are to be manufactured in less time. These types of
bricks are heavier and stronger than the hand moulded ones and possess a sharp regular shape, a smoother
surface and sharp edges. There are two types in machine moulding

72. Drying of Bricks
Moulded bricks cannot be burnt directly, as they may get damaged. So before burning they
should be dried either naturally or artificially for about two weeks.
Natural Drying: It is also called hack drying, which comprises placing moulded bricks in rows on
their edges, slightly above the ground called a hack. These bricks are air and sun-dried that is
strong enough to use for the construction of small structures.
Artificial Drying: When bricks are needed to dry on a large scale, then this artificial drying is
preferred. They are dried in special dryers which receive heat from specially made furnaces for
artificial drying.
Burning of Bricks
After the process of moulding and drying, bricks are burnt in kilns to impart hardness, strength
and to increase the density of the brick. Some physical and chemical changes take place in the
burning of bricks. Heating brick to about 640°C produces only physical changes. If a brick is
heated up to 700-1,000°C, it undergoes chemical changes. During this reaction, the materials
present in brick alumina and silica fuse together to make the brick strong and stable to prevent
from cracking and crumbling.

73. The types of Kilns used for burning purposes are
Clamp or Open Kiln: This is a temporary structure with some advantages like low initial cost, low
fuel cost and a few skilled labourers are sufficient to complete the process. The disadvantage is
only a small quantity of bricks is manufactured at a time and in that only 60% are good quality
bricks.
Intermittent Kiln: When a large number of good quality bricks are needed, intermittent or
continuous kilns are preferred. In this kilns, the process of burning is discontinuous.
Continuous Kilns: In this process, the burning is continuous and they are of three type’s i.e.,
Bull's Trench Kiln, tunnel Kiln and Hoffman's Kiln. To get a good quality brick it has to be heated to
the required temperature. The bricks begin to lose their shape and materials get vitrified if heating
of brick earth goes beyond 1,300°C.

75. Superiorities of brickwork over stone work:
1.At places where stones are not easily available but where there is plenty of clay, the brickwork
becomes cheaper than stonework.
2.The cost of construction works out to be less in case of brickwork than stonework as less skilled
labour is required in the construction of brickwork.
3.No complicated lifting devices are necessary to carry bricks as they can be easily moved by
manual labour.
4.The bricks resist fire better than stone and hence, in case of a fire, they don’t easily disintegrate.
5.The bricks of good quality resist the various atmospheric effects in a better way than the stones.
6.In case of brickwork, the mortar joints are thin and hence the structure becomes more durable.
7.It is easy to construct connections and openings in case of brickwork than stonework.

76. Inferiorities of Brickwork over Stonework
1.The brickwork is less watertight than stonework. The bricks absorb moisture from the
atmosphere and dampness can enter the building.
2.The brickwork doesn’t create a solid appearance in relation to the stonework and hence, for
public buildings and monumental structures, the stonework is found to be more useful than
brickwork.
3.The stonework is stronger than brickwork.
4.The architectural effects of better quality can be developed by the stonework.
5.The stonework is cheaper at places where stones are easily available.

77. TILES

78. Characteristics of good tiles
Grade
Stone grades may only come in three choices, depending on the retailer's system. Typically, grade
1 is for premium quality stone tiles. Grade 2 is for tiles with minor defects like chips or scratches.
And grade 3 is for tiles with major defects that will only make them suitable for decorative pieces.
True Color
At the time of manufacturing, due to excessive use of calcite or dolomite the tiles may change their
colour to black or yellowish.
Porosity
It is the percentage of pores present in the tiles. Usually sand contains less porosity when
compared to travertine soil. The higher the pores the higher the porosity.
Hardness
The hardness of tiles lies in between 5 to 6 whereas the porecelian tiles have a hardness of 7 to 8.
Static Coefficient of Friction (SCOF)
It can also referred as particular characteristic as "slip resistance." The static coefficient of friction
determines how slippery a tile is and can help you decide what material works best in the bath or
around a pool. A minimum SCOF of 0.5 is prescribed by law. However, depending on the finish, you
can increase the SCOF for travertine.

79. 1 • Batching
2 • Crushing & Milling
3 • Wetting ( Raw Materials + water)
4 • Grinding (slurry)
5 • Atmosphizer( Hot air entry)
6 • Moulding
7 • Drying
8 • Glazing
9 • Burning
10 • Quality check
11 • Packaging
Manufacturing
Process

80. Types of Tiles:
1. Based on Application.
2. Based on Material
Based on Application
•Roofing tiles
•Flooring tiles
•Wall tiles
•Partition tiles.
Based on Material
•Ceramic tiles or non-porcelain tiles
•Porcelain tiles.

82. Efflorescence: starts with salt. Salts are found in the ground and in construction materials such as
brick, mortar, cement, lime, sand, clay, admixtures, and backing materials.
• Typical efflorescence is white but can vary in color, including yellow or brown, depending on the
salt and accompanying chemicals.
• Common salts include calcium sulfate, sodium sulfate, potassium sulfate, vanadyl sulfate,
calcium carbonate, sodium carbonate, potassium carbonate, and manganese oxide.
• Water is the second ingredient. During construction, water used in cement and mortar mixtures
can start the process, dissolving salts in building materials it contacts. Water also comes from
rain, snow, sprinkler systems, cracks, gaps and the ground.
• Water dissolves salts and moves them to the surface of brick walls or cement foundations. As
water evaporates, the salts are left behind, which you see as efflorescence.

83. Removal of Efflorescence
1. Stiff brush
On some smooth surfaces, you may be able to use a stiff brush. Because efflorescence is dry and powdery, a brush
will easily sweep it away.
2. Water rinse
On other surfaces, rinsing with a garden sprayer or pressure washer can dissolve efflorescence, allowing it to run
off. With a pressure washer, use the widest-angle tip that works without damaging the surface. With the rinsing
method, though, the water may bring more salts to the surface as the substrate dries, so re-rinsing or brushing may
be necessary.

84. 3. Chemical cleaning
Brushing and pressure-washing may be insufficient on tough salt deposits. An acidic cleaner, such as
PROSOCO’s can dissolve efflorescence more effectively.
Water 60-100 w/w
Silicic acid, di-ethoxy-octylsilyl
Tri-methyl-silyl ester
1-5w/w
Tri-ethoxy-octysilane 1-5w/w