All about bricks you should know as a civil engineer

this document tell you all about bricks

1. Department of Civil Engineering
Chittagong University of Engineering & Technology
CE 203
ENGINEERING MATERIALS
BRICKS
MD. ASIFUR RAHMAN
LECTURER

2. Bricks
•Bricks are blocks of tampered clay / cement & sand or some other
materials molded to suitable shapes and sizes while it is still in plastic
condition, dried in the sun and burnt, to make them more strong, hard
and durable.
•Bricks are normally rectangular in shape and size is set so as to make
it easy for workers to handle.
•Bricks are very popular and widely used construction material
because, they are cheap, durable and they are easy to handle and
work with

10. Size of Bricks
•Size and shape of bricks can be made over a wide range depending on
purpose of use.
•The standard size of bricks in our country according to P.W.D. is -
9.5"x4.5"x2.75". There are other sized bricks also. But this size is most
economical, because when bricks are put in any construction with mortar
the size becomes 10"×5"×3" (approximately). Therefore the sizes of
walls which are constructed by bricks in our country are 3", 5", 10", 15",
20", 25" and 30". The standard size of bricks can be used safely without
any breakage

11. Frog mark
Frog mark is a depression of about 1 to 2 inch depth made on the face of
the bricks during molding the bricks.
Frog marks serve two functions:
•Frog mark facilitates the bonding of brick with the course of brick above it.
•Trademark or identification mark of the manufacturer is also indicated on
the frog

12. Classifications

13. Classifications based on physical and mechanical properties
Bricks can be classified as:
i. S-grade (or 1st Class brick)
ii. A-grade (or 2nd Class brick)
iii. B-grade (or 3rd class brick)
iv. Over-burnt or Jhamabrick
v. Under-burnt brick
Note that this classification is applicable mostly for burnt clay bricks

14. Classifications based on physical and mechanical properties
S-grade (or 1st Class brick):
Standard Size; Uniform yellow or red colored;
Well brunt; Regular shape; Uniform texture
No efflorescence; No pebbles, gravels or organic matter;
Water absorption capacity ≤ 12-15% when immersed in cold water for 24
hours.;
Crushing strength: σmean= 4000 psi & σmin= 3500 psi;
Emits metallic sound; No finger nail impression.
Usage:
in building of long durability, say 100 years.
for building exposes to corrosive environment;
for making coarse aggregate of concrete.

15. Classifications based on physical and mechanical properties
A-grade (or 2nd Class brick):
•Standard Size; Uniform yellow or red colored;
•Well brunt (slightly over-brunt is acceptable);
•Regular shape; Efflorescence is not appreciable;
•15% < Water absorption capacity ≤ 20%;
•Crushing strength: σmean = 2500 psi; σmin = 2200 psi;
•Emits metallic sound; No finger nail impression.
Usage:
•used in partition walls.
•preferred as brick ballast in foundations & floorings
•for all important or unimportant hidden masonry works
•for the construction of one-storied building, temporary shed

16. Classifications based on physical and mechanical properties
B-grade (or 3rd Class brick):
•Soft and light red colored; Shape and size not regular;
•Under brunt (slightly over-brunt is acceptable);
•Extensive efflorescence; Non-uniform texture;
•20% <AC ≤ 25%;
•Crushing strength: σmean= 2000 psi; σmin= 1500 psi
•Emits dull/blunt sound;
•Left finger nail impression
•Usage:
•Though they have poor strength and texture, yet they are highly economical
and can be used in the construction of temporary and rural structures

17. Classifications based on physical and mechanical properties
Over-brunt or Jhamabrick:
•Non-uniform color –red, black mixed;
•Shape distorted (as larger than the required amount of silica gets fused);
•High water absorption capacity;
•Strength may be higher or equivalent to S-grade (or 1st class) brick.
•Usage:
•have very low strength and are not recommended for application in
major construction works.
•used in flooring, and inferior construction works.
•lime concrete for foundation
•In making shurki/coarse aggregates.
•In concrete of slab and beam which will not come in contact of water.

18. Classifications based on physical and mechanical properties
Under-brunt brick:
▪Half brunt brick;
▪Yellow colored;
▪Low strength;
▪Such bricks should not be exposed to rainwater
Usage:
✓surkiin lime-terracing;
✓soling under RCC footing or basement

19. Classifications based on Raw materials used
Depending on raw materials used in manufacturing bricks can be classified
as:
•Burnt clay bricks
•Fire clay/ refractory /engineering bricks
•Fly ash clay bricks
•Sand lime bricks
•Concrete bricks

20. Classifications based on Raw materials used
Rich in
“Kaolinite”

21. Classifications based on Raw materials used
Burnt Clay Bricks:
•It is obtained by pressing the clay in molds and fried and dried in
kilns. Burnt clay bricks are commonly used in construction across
the globe. It requires plastering when used in construction
•As in our country burnt clay bricks are used extensively, this
lecture therefore contains details of properties and manufacturing
processes of this type of brick.

22. Classifications based on Raw materials used

23. Classifications based on Raw materials used

24. Classifications based on Raw materials used

25. Classifications based on Raw materials used

26. Classifications based on shape

27. Classifications based on ASTM

28. Chemical Composition

29. Chemical Composition

30. Chemical Composition

31. Chemical Composition

32. Chemical Composition

33. Chemical Composition

34. Harmful Ingredients of Brick

35. Harmful Ingredients of Brick

36. Harmful Ingredients of Brick

37. Brick Characteristics

38. Laboratory Test of Bricks

39. Laboratory Test of Bricks
Compressive/ Crushing Strength Test:
Determination of compression capacity of brick is the most important
test of brick. In ASTM standard for clay bricks, compressive strength
test is done on five half bricks (halved lengthwise). Average of the
obtained values is used as compressive the compressive strength of
the whole lot of brick.
Different standards are followed for different types of brick:
▪ for clay bricks – ASTM C67
▪ for concrete blocks – ASTM C14

40. Laboratory Test of Bricks
Frog Mark: R&C
Sample
No.
Compressive
Strength
MPa (psi)
Average
Compressive
Strength
MPa (psi)
Water
Absorption
(%)
Avg. Water
Absorption (%)
1 14.4 (2090)
---
17.5
15.2
2 9.6 (1390) 14.2
3 18.4 (2670) 12.9
4 9.3 (1350) 19
5 9.5 (1380) 12.5

41. Laboratory Test of Bricks
Test of Water Absorption Capacity
This test determines the porosity of bricks which can then be used as an indication
of the potential for the development of problems related to the penetration of salts
and other materials into the units, such as salt attack and efflorescence.
Absorption test is carried out on five half bricks. Bricks are oven dried, weighed
and keep immersed in water for 24 hours. SSD weight of bricks is measured.

42. Laboratory Test of Bricks
Efflorescence:
Efflorescence is a crystalline deposit of salts often seen on the surface of concrete, brick, stucco,
or natural stone surfaces. Although unattractive, efflorescence is usually harmless. In rare cases
excessive efflorescence, within the pores of the material, can cause expansion that may disrupt
the surface.
For this test five pairs of bricks are taken for efflorescence test of brick. One brick from each pair is
immersed in distilled water of one inch depth for 7 days where as other five bricks are kept in air.
After 7 days all bricks are oven dried and examined for efflorescence – each pair of brick is
compared, if the brick immersed in water differs in texture than its pair brick, the brick is
considered effloresced.

43. Laboratory Test of Bricks
Density/Unit Weight:

44. Laboratory Test of Bricks
Distortion / Warpage
The amount of distortion is based on the brick specification and face dimension.
Distortion may be
convex or concave and may be in the plane of the wall or perpendicular to it.

45. Field Test of Bricks

46. Manufacturing of Burnt Clay Bricks in Kilns
The process of manufacturing of bricks from clay involves five basic stages. Depending on type
of kiln, the technology used etc., each processing can be done differently.
1. Preparation of raw ingredients;
2. Pugging or tempering of clay;
3. Molding of bricks;
4. Drying of bricks;
5. Burning of bricks

47. 1. Preparation of raw ingredients (clay/silica/alumina…):
Involves operations like un-soiling the top loose earth, then digging,
cleaning, weathering & blending of the earth. After removing the top
unsuitable soil, the clay is dug out and is spread on the leveled ground,
and is left exposed to atmosphere for softening. Digging the earth before
rains is advantageous; the full monsoon can be utilized for weathering the
earth.
After weathering the earth is chemically analyzed. If any deficiency of any
ingredient is observed, it should be added correspondingly.

48. Pugging or tempering of raw materials:
This step involves breaking up of prepared clay, watering, and kneading
till the earth becomes a homogeneous mass. Then water is added in the
required quantity. The whole mass is kneaded manually (under the feet
of men or cattle) or mechanically with using Pug-mill.

49. Molding of bricks:
After tempering of clay, bricks should be molded as soon as possible. Otherwise,
the pugged clay may become stiff and molding brick may become difficult. Molds
are made slightly greater in size than the standard size of the brick to
compensate for shrinkage on drying and burning.
Molding is of two types: hand molding (ground molding and table molding) &
machine molding. Molding directly on ground has two drawbacks:
i) the lower face is very rough; ii) Bricks cannot have frog marks.

50. Drying of bricks:
The objectives of drying the bricks are
i) to remove as much of moisture from bricks as possible, so as to save fuel and
time while burning.
ii) to avoid the chances of cracking and distortion of bricks during burning and
iii) to increase the mechanical strength of bricks so that they can be handled
and stocked without any damage to the raw bricks.
Drying can be done either using sunlight or by hot air flow in the kiln.

51. Burning of bricks:
In the process of burning, the dried bricks are burned either in clamps (small scale) or kilns
(large scale). Proper burning imparts strength and hardness to bricks and makes them
dense and durable. Heating green bricks up to 640 degree C produces only physical
changes, heating above that (700~1100 C) they undergo chemical changes. As mentioned
before, at about 1100 degree C, lime acts as catalyst to elevate the furnace temperature to
1650 degree C and the two main constituents of bricks-silica and alumina- combine with
each other and bricks become dense and strong.

52. Kiln:
Kiln is a thermally insulated chamber, a type of oven, which produces temperatures sufficient
to complete some process of hardening, drying, or chemical changes and finally making
burnt brick.
Depending on manufacturing process two types kiln are used in brick production:
i) Intermittent kiln;
ii Continuous kiln; e.g. Hoffman’s kiln, Tunnel kiln, Rotary / Mobile / automatic kiln etc

53. Intermittent Kiln
Intermittent kilns work by firing cool wares using a heat source, where the
temperature is slowly increased throughout the firing process
Advantages-
- Suitable for small quantity of brick production at a time.
- Less costly than continuous kiln
Disadvantages -
− Supply of bricks is intermittent
− Quality of burning is non-uniform: near the bottom, the
bricks are over-burnt and near the top are under-burnt.

54. Continuous Kiln
Such kiln consists of a series of connected kilns or one continuous
chamber, through which a fire travels, green brick being set ahead of the
fire, gradually passes through process of drying, preheating, burning,
cooling and then brining out ready brick from kiln.
Most commonly used continuous kilns are–
i. Hoffman’s kiln
ii. Tunnel kiln
iii. Rotary/ automatic kiln

55. Hoffman’s Kiln
This kiln is circular in plan; Modern Hoffman’s Kilns are of oval shape. For air
outflow, chimney is placed at the central point
Advantages of Hoffman Kiln:
• Better control on heat;
• Supply of bricks is continuous;
• Bricks are burnt evenly; bricks of good quality are produced;
Disadvantages of Hoffman Kiln:
• Initial cost is high;
• Requires regular demand of the bricks, which may not be possible.

56. Hoffman’s Kiln

57. Hoffman’s Kiln

58. Tunnel kiln
In a tunnel kiln dry bricks are loaded onto a fireproof trolley or kiln car. This then
travels very slowly through the kiln. Typical schedule through the kiln from end to
end is 3-7 days but variations occur depending on production schedules. Although
tunnel kilns are generally more expensive to build than chamber kilns they are
more economical to run and lend themselves to high degrees of automatic control.

59. Rotary / Mobile tunnel kiln
Rotary tunnel kiln is improved and upgraded from traditional tunnel kiln. Its biggest
characteristic is the adobes stay still while the body of rotary kiln moves. Rotation movement
of the kiln body in orbit intermittent forward - front eat bricks back end spit finished bricks, in
turn, drying, preheating, firing, cooling, the whole process of bricks.

60. Pollution from Traditional Brick Industry

61. Green Technology- AAC Block