Bricks Flashcards
Size of Standard Brick (Modular Brick)
19 x 9 x 9 cu. cm
19 x 9 x 4 cu. cm
Size of mortar to be applied
1 cm
Size of Brick with Mortar
20 x 10 x 10 cu.cm
Size of Field Brick
9” x 4.5” x 3”
Indent in the brick is called
Frog
Size of Frog
10 × 4 × 1 cu. cm
Why are frogs provided
To hold mortar
Average weight of Bricks
30 - 35 N
Classification of Bricks
1st Class
2nd Class
3rd Class
4th Class
Characteristics of 1st Class bricks
i. Thoroughly burnt, deep red, cherry or copper color
ii. Smooth surface, parallel, sharp and straight edges
iii. Free from flaws, cracks and stones
iv. Uniform textures
v. No impression should be left on the brick when scratched by nail.
vi. Metallic or ringing sound when two bricks struck against each other
vii. Water Absorption should be 12-15% of its dry weight.
viii. Crushing strength not less than 10 N / sq mm
ix. Built in Kilns
Uses of First class brics
Pointing, exposed face work in masonry structures, flooring, reinforced brick work
Characteristics of 2nd Class Bricks
i. Thoroughly burnt, deep red, cherry or copper color
ii. Smooth surface, parallel, sharp and straight edges
iii. Small Cracks and distortions present
iv. Uniform textures
v. Moderate hardness
vi. Metallic or ringing sound when two bricks struck against each other
vii. Water Absorption should be 16-20% of its dry weight.
viii. Crushing strength not less than 7 N / sq mm
ix. Built in Kilns
Uses of Second Class Bricks
Used for all important or unimportant hidden masonry works, and centering of reinforced brick and reinforced cement concrete (RCC) structures. Plasters
Characteristics of 3rd Class Bricks
i. Underburnt
ii. Soft and light colored
iii. Dull sound when struck together
iv. Water Absorption about 25% of dry weight
v. Built in Clamps
vi. Irregular shape and size
Use of 3rd Class Bricks
Temporary Structures
Characteristics of 4th Class Bricks
i. Overburnt
ii. Badly distorted in shape and size
iii. Brittle
iv. Built in Clamps
Use of 4th Class Bricks
Used for foundation and floors in lime concrete and road metal
Properties of Good Bricks - Size and Shape
uniform size and plane, rectangular surfaces with
parallel sides and sharp straight edges
Properties of Good Bricks - Color
Uniform deep red or cherry colour
Properties of Good Bricks - Texture and Compactness
The surfaces should not be too smooth to cause slipping of mortar. It should have a precompact an uniform texture.
Properties of Good Bricks - Hardness
Hard - when scratched by a finger nail no impression is made
Properties of Good Bricks - Sound
Metallic sound when two bricks struck together
Properties of Good Bricks - Water Absorption
Should not exceed 15%
Properties of Good Bricks - Crushing Strength
Should be more than 10 N / sq mm
Properties of Good Bricks - Efflorescence
Crystalline deposit of salt when water is dried off (Efflorescence) should not be present
Properties of Good Bricks - Organic Mater
Should not be present
Properties of Good Bricks
i. Size and Shape
ii. Color
iii. Texture and Compactness
iv. Hardness
v. Sound
vi. Water Absorption
vii. Crushing Strength
viii. Efflorescence
ix. Organic Matter
Composition of a Brick
- Silica 50-60%
- Alumina 20-30%
- Lime 5%-10%
< 20% of these:
- Magnesia < 1%
- Oxides of Fe < 7%
- Alkalis < 10%
Very Small Percent of these:
- CO2
- SO3
- H2O
Function of Silica in Brick
- Enables brick to retain its shape and imparts durability
- Prevents shrinkage and warping
What happens if there is excess silica in brick
Brick becomes Brittle and weak on burning
Function of Alumina in brick
Absorbs water and renders clay plastic
What happens if there is excess alumina in brick
The brick will develop cracks on drying
Function of Lime in Brick
Reduces Shrinkage on drying
What happens if there is excess Lime in brick
It will cause the brick to melt and brick loses its shape
Function of Magnesia in Bricks
Affects the color and makes the brick yellow in burning. Causes the clay to soften at slower rate and reduces warping
Function of Iron Oxide in Bricks
- Gives red color on burning when excess of oxygen is available
- Improves impermeability and durability
- Tends to lower fusion point of clay
- Gives strength and hardness
Harmful Substances in Bricks
- Pebbles, Gravels and Grits
- Iron Pyrites
- Excess lime, alkalis
- Organic Matter
- Carbonaceous Materials
- Sulphur
- Water
What happens when pebbles, gravel and grits are present in bricks
They will not allow the clay to be mixed thoroughly and spoil the appearance of the brick. The bricks may crack while working
What happens when Iron Pyrites are present in bricks
leads to deceomposition of bricks during burning due to its(pyrite) oxidation. Discolorisation and splitting of bricks
What happens when excess Alkalis are present in Bricks
Increases water absorption, causes efflorescence.
What happens when Organic Matter are present in Bricks
Upon burning, the organic matter gets charred and leave pores. Increases water absorption and reduces strength
What happens when Carbonaceous Materials are present in Bricks
Greatly affects colour of raw clay
What happens when Sulphur is present in Bricks
Swells the brick upon burning. If in excess, white patches can be seen in the bricks
What happens when Water is present in Bricks
Causes shrinkage during burning
