- One of the oldest building materials,
continues to be the most popular and leading construction material.
SIZE OF BRICKS:-
- Standard size of Bricks (modularize)=19cm x 9cm x 9cm
- Nominal size of Bricks (with mortar) = 20cm x 10cm x 10cm
- Conventional size of Bricks = 23cm x 11.4cm x 7.6cm
Classification of bricks
- First class bricks
- Thoroughly burnt, deep red, cherry or
- Smooth, rectangular surface, sharp and straight edges.
- maximum Water absorption 20% of its dry weight when immersed in cold water for 24 hours
- Crushing strength – should not be less than 10N/mm
- USES:- Used for exposed face work in masonry, flooring, and Ranford brickwork.
- Second class brick
- Small racks and distortions permitted
- Water absorption– 22 % of its dry wt.
- Cushing strength– should not be less than
- Uses– second class bricks are recommended for all unimportant hidden masonry works
|PROPERTIES||1ST CLASS BRICK||2ND CLASS BRICK||3RD CLASS BRICKS||4TH CLASS BRICK|
|COLOR||Deep red cherry or copper color||Uniform red||Pale yellow color as this under burnt||Dark red, bluish color. As this over burnt|
|WATER ABSORPTION||20% of dry weight||22% of dry weight||25% of dry weight||More than 25 % of dry weight|
|CRUSHING STRENGTH||Minimum crushing strength 10N/mm2||7.0N/mm2||Less then 7.0||5.0N/mm2|
|ABRASION||No impression should be left on a brick when scratched with a nail||No impression||Impression present||Impression is present|
|IMPACT RESISTANCE||Should not break into pieces when dropped from a height of 1.0 meter||Should not break||break||break|
|SOUNDNESS||Brick should not break and produce a clear ringing sound when struck with each other.||Brick should not break & produce a clear ringing sound||Dull sound||Brick break easily & produce a dull sound|
|USES||For pointing, exposed masonry work||Used for hidden masonry work||For temporary structure||Used as ballast in lime concrete|
CHARACTERISTICS OF GOOD BRICKS
- Size and shape – uniform size, rectangular surface with parallel sides and sharp straight edges
- Color – uniform deep red color indicative of uniformity in chemical composition and thoroughness in burning
- Hardness & soundness – The brick should be so hard that when scratched by a fingernail, no impression is made. When two bricks stuck together, a metallic sound should be produced
- Impacts:- Brick should not break into the piece when – dropped from a height of 1.0 meter
- Water absorption – should not exceed 20 % of its dry weight when kept immersed in
water for 24 hours.
- Crushing strength:- Should not be less than 10N/mm2
- Bricks earth:- should be free from stones, kantars, organic matter.
Ingredients of good brick earth
- Silica – 50 – 60 % – Prevents shrinkage and warping. excess of silica makes the brick brittle
- Alumina – 20 – 30 % – Provide plasticity to bricks earth. excess of alumina produce
- cracks on drying bricks
- Lime – 10 %- Reduces shrinkage, helps in a fusing of silica and alumina
- Ferric oxide < 7 % -Reddish tinge to brick, give strength and hardness,
- Magnesia < 1 % – magnesia gives a yellowish tinge to be bricks
- Alkalis – < 10 % – excess of alkali cause efflorescence
The function of various Ingredients of Brick earth
- SILICA ( 50 – 60 ) %
- It enables the brick to retain its shape and import durability.
- It prevents shrinkage and warping
- The excess of silica makes the bricks brittle and weak on burning.
- ALUMINA (20 – 30 ) %
- It absorbs water and renders the clay plastic.
- If alumina is present in excess of a specified quantity, it produces cracks in brick on drying
- Lime (10%)
- reacts with silica during burning and thus helps to bind it.
- Magnesia (< 1%)
- gives yellowish tings to brick
- Iron oxide (< 7 %)
- give reddish tings to bricks
- gives strength and hardness improves impermeability & durability
Harmful substance in brick earth
Lime:-desirable amount of lime results in good bricks:- but if lime is present in lumps, it absorbs moisture swells and causes the disintegration of the bricks.
:- lime should be present in finely divided slots & lumps if any should be removed in beginning itself.
- Pebbles, grovels, grits:- do not allow the clay to mixed thoroughly and spoil the appearance of brick.
- Iron pyrites:- tend to oxidize and decompose the brick burning, pyrites decolorize the brick
- Alkalies:- forming less than 10% of row clay, are of great value as fluxes
- mainly present in the form of soda or potash
- alkalies absorb moisture when bricks come in contact with moisture, on drying moisture evaporates leaving behind grey or white powder deposits
- Organic matter:- If left in bricks, undergoes decomposition over a period of time, resulting in the formation of gases, escape of gases making brick porus
The manufacturing process of bricks
- Unsoiling:- Top 20 cm of soil is removed because it contains high organic matter.
- Digging:- After removing the top 20 cm of soil, the remaining soil is dug out and spread over the level field.
- Cleaning:- is the process of removal of impurities from the soil i, e. organic matters, stones, pebbles, etc.
- Weathering:– cleaned soil left in heap and exposed to the atmosphere for at least one month. This is done to develop – homogeneity in the mass of soil, particularly if they are from different sources.
- Blending:- clay is made loose and any ingredient – deficiency spread over it.
- Tampering:- water is added in clay in order to bring it up to req. Plasticity is required. for the next operation of molding. Kneading the brick earth
Frog (indentation mark )
Purpose – act as a key for mortar
- provide lateral stability to brick
3. Drying – is done either naturally or artificially.
- the water content of brick is reduced up to 2.0% so that energy consumption during the burning process reduces.
- during drying bricks must be placed along the edges, not along the surface, so that maximum surface area exposed to the atmosphere.
4. Burning – temp. is (900 – 1200)
EFFLORESCENCE IN BRICKS
IS:- 3495 – Liability of efflorescence shall be reported as nil, slight, moderate, heavy or serious.
(a) Nil- When there is no perceptible deposit of efflorescence
(b) Slight – When not more then 10 percent of the exposed area of the brick is covered with a thin deposit of salts
(c) Moderate:-when there is a heavier deposit then under slight and covering up to 50 percent of the exposed area of the brick surface but unaccompanied by powdering or flaking of the surface.
(d) Heavy:- when there is a heavy deposit of salts covering 50 % or more of the exposed areas but unaccompanied by powdering or flaking of the surface.
(e) Serious:- when there are heaving deposits of salts accompanied by powdering or flaking of exposed surfaces.
Notes;- – wt. of 1 m3 of brick is approximately = 1800 kg
- wt. of 1 brick is (3 – 3.5)Kg
- 1m3 = 500 – 550 Brick
Other types of brick
- Small holes may exceed 25 percent of the total volume of the brick
- Lighter in weight & provides insulation against heat, due to voids present in it.
- has less water absorption compared to other bricks
- Noise reduction
- Autoclave bricks are bricks cured in pressurized steam,
- bricks got cured in less than 10 hours as compared to over 10 days.
- are those bricks providing resistance against decomposition of brick due to chemical action, high temperature, Dampness
- Compressive strength of this bricks various from Types – acid bricks
- Basic bricks – Magnesite, Mullite, carbon & basic ramming brick.
- Neutral bricks