CONTENTS
Brick is obtained by moulding good clay into a block, which is dried and then burnt. This is the oldest building block to replace stone. Manufacture of brick started with hand moulding, sun drying and burning in clamps.
A considerable amount of technological development has taken place with knowledge about to properties of raw materials, better machineries and improved techniques of moulding drying and burning.
The size of the bricks are of 90 mm × 90 mm × 90 mm and 190 mm × 90 mm × 40 mm.
PROPERTIES OF BRICKS USED IN CONSTRUCTION
The following are the required properties of good bricks:
[1] COLOUR
The bricks should be uniform and bright.
[2] SHAPE
Bricks should have plane faces. They should have sharp and true right angled corners.
[3] SIZE
Bricks should be of standard sizes as prescribed by codes.
[4] TEXTURE
Bricks should possess fine, dense and uniform texture. They should not possess fissures, cavities, loose grit and unburnt lime.
[5] SOUNDNESS
When the brick is struck with hammer or with another brick, it should produce metallic sound.
[6] HARDNESS
Finger scratching should not produce any impression on the brick.
[7] STRENGTH
The 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 m on a hard ground, the brick should not break into pieces.
[8] WATER ABSORPTION
After immersing the brick in water for 24 hours, water absorption should not be more than 20% by weight. For class-I works this limit is 15%.
[9] 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.
[10] THERMAL CONDUCTIVITY
Bricks should have low thermal conductivity, so that buildings built with them are cool in summer and warm in winter.
[11] SOUND INSULATION
Heavier bricks are poor insulators of sound while lightweight and hollow bricks provide good sound insulation.
[12] FIRE RESISTANCE
Fire resistance of bricks is usually good. In fact bricks are used to encase steel columns to protect them from fire.
CLASSIFICATIONS OF BRICKS USED IN CONSTRUCTION
The bricks used in construction are classified as:
[1] FIRST CLASS BRICKS
These bricks are of standard shape and size. They are burnt in kilns. They fulfill all desirable properties of bricks.
- These bricks are table moulded
- The surfaces and edges of the bricks are (4S) Sharp, Square, Smooth & Straight.
- The Bricks are well brunt and have uniform texture, metallic ringing when struck against each other.
- 1st Class Brick is used for superior works.
[2] SECOND CLASS BRICKS
These bricks are ground moulded and burnt in kilns. The edges may not be sharp and uniform. The surface may be somewhat rough. Such bricks are commonly used for the construction of walls which are going to be plastered.
[3] THIRD CLASS BRICKS
These bricks are ground moulded and burnt in clamps. Their edges are somewhat distorted. They produce dull sound when struck together. They are used for temporary and unimportant structures.
[4] FOURTH CLASS BRICKS
These are the over burnt bricks. They are dark in colour. The shape is irregular. They are used as aggregates for concrete in foundations, floors and roads.
TYPES OF BRICKS USED IN CONSTRUCTION
[1] BUILDING BRICKS
These bricks are used for the construction of walls be it residential or commercial Buildings.
[2] PAVING BRICKS
These are vitrified bricks and are used as pavers. Paving Bricks are manufactured to be laid flat on the ground. They are different from the type made to be used vertically for walls and chimneys and other construction projects. They are designed to last when installed in the ground. They can withstand both hot and cold temperatures, snow and rain, and foot traffic.
[3] FIRE BRICKS
A fire brick, firebrick, or refractory bricks is a block of refractory ceramic material used in lining furnaces, kilns, fireboxes, and fireplaces. A refractory bricks is built primarily to withstand high temperature, but will also usually have a low thermal conductivity for greater energy efficiency. These bricks are specially made to withstand furnace temperature. Silica bricks belong to this category.
[4] SPECIAL BRICKS
These bricks are different from the commonly used building bricks with respect to their shape and the purpose for which they are made. Some of such bricks are explained below:
{1} SPECIALLY SHAPED BRICKS
Not every building is designed in such a way that uniform bricks can be used. Special shaped bricks allow for unique and innovative designs to be created.
{2} FACING BRICKS
These bricks are used in the outer face of masonry. Once these bricks are provided, plastering is not required. The standard size of these bricks are 190 × 90 × 90 mm or 190 × 90 × 40 mm.
{3} PERFORATED BUILDING BRICKS
These bricks are manufactured with area of perforation of 30% to 45%. The area of each perforation should not exceed 500 mm². The perforation should be uniformly distributed over the surface. They are manufactured in the size 190 × 190 × 90 mm and 290 × 90 × 90 mm.
{4} BURNT CLAY HOLLOW BRICKS
They are light in weight. They are used for the construction of partition walls. They provide good thermal insulation to buildings. They are manufactured in the sizes 190 × 190 × 90 mm,290 × 90 × 90 mm and 290 × 140 × 90 mm. The thickness of any shell should not be less than 11 mm and that of any web not less than 8 mm.
{5} SEWER BRICKS
These bricks are used for the construction of sewage lines. They are manufactured from surface clay, fire clay shale or with the combination of these. They are manufactured in the sizes 190 × 90 × 90 mm and 190 × 90 × 40 mm. The average strength of these bricks should be a minimum of 17.5 N/mm² . The water absorption should not be more than 10%.
{6} ACID RESISTANCE BRICKS
These bricks are used for floorings likely to be subjected to acid attacks, lining of chambers in chemical plants, lining of sewers carrying industrial wastes etc. These bricks are made of clay or shale of suitable composition with low lime and iron content, flint or sand and vitrified at high temperature in a ceramic kiln.
USES OF BRICKS IN CONSTRUCTION
Bricks are used in the following civil works:
[1] Bricks are used as building blocks.
[2] Bricks are used for lining of ovens, furnaces and chimneys.
[3] They are used for protecting steel columns from fire.
[4] Bricks are used as aggregates in providing water proofing to R.C.C. roofs.
[5] Bricks are used for pavers for footpaths and cycle tracks.
[6] Bricks are used for lining sewer lines.
TESTS ON CONSTRUCTION BRICKS
The following laboratory tests may be conducted on the bricks to find their suitability:
[1] CRUSHING STRENGTH TEST
The brick specimen are immersed in water for 24 hours. The frog of the brick is filled flush with 1:3 cement mortar and the specimen is stored in damp jute bag for 24 hours and then immersed in clean water for 24 hours. The specimen is placed in compression testing machine with 6 mm plywood on top and bottom of it to get uniform load on the specimen. Then load is applied axially at a uniform rate of 14 N/mm² . The crushing load is noted. Then the crushing strength is the ratio of crushing load to the area of brick loaded. Average of five specimen is taken as the crushing strength.
Crushing Strength = Crushing Load / Area of Bricks
[2] ABSORPTION TEST
Brick specimen are weighed dry. Then they are immersed in water for a period of 24 hours. The specimen are taken out and wiped with cloth. The weight of each specimen in wet condition is determined. The difference in weight indicate the water absorbed. Then the percentage absorption is the ratio of water absorbed to dry weight multiplied by 100. The average of five specimen is taken. This value should not exceed 20%
%Absorption = Water Absorbed / Dry Weight × 100
[3] CHECK SHAPE AND SIZE OF BRICKS
Bricks should be of standard size and edges should be truly rectangular with sharp edges. To check it, 20 bricks are selected at random and they are stacked along the length, along the width and then along the height. For the standard bricks of size 190 mm × 90 mm × 90 mm.
IS code permits the following limits:
Lengthwise: 3680 to 3920 mm
Widthwise: 1740 to 1860 mm
Heightwise: 1740 to 1860 mm.
A good brick should have rectangular plane surface and uniform in size. This check is made in the field by observation.
[4] CHECK UNIFORMITY IN COLOUR
A good brick will be having uniform colour throughout. This observation may be made before purchasing the brick.
[5] CHECK THE STRUCTURE
A few bricks may be broken in the field and their cross-section observed. The section should be homogeneous, compact and free from defects such as holes and lumps.
[6] SOUND TEST
If two bricks are struck with each other they should produce clear ringing sound like metal being struck together. The sound should not be dull.
[7] HARDNESS TEST
For this a simple field test is scratch the brick with nail. If no impression is marked on the surface, the brick is sufficiently hard. Hardness test can also be carried out by stricking 2 bricks to produce a metallic sound or by Dropping the brick from height of 1 meter, it the brick didn’t Crack the brick is Hard.
[8] EFFLORESCENCE TEST
The presence of alkalies in brick is not desirable because they form patches of gray powder by absorbing moisture. Hence to determine the presence of alkalies this test is performed as explained below.
Place the brick specimen in a glass dish containing water to a depth of 25 mm in a well ventilated room. After all the water is absorbed or evaporated again add water for a depth of 25 mm. After second evaporation observe the bricks for white/grey patches. The observation is reported as ‘nil’, ‘slight’, ‘moderate’, ‘heavy’ or serious to mean.
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