BRICKS

1
BRICKS

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
  1. Thoroughly burnt, deep red, cherry or
    copper colour.
  2. Smooth, rectangular surface, sharp and straight edges.
  3. maximum Water absorption 20% of its dry weight when immersed in cold water for 24 hours
  4. Crushing strength – should not be less than 10N/mm
  5. USES:- Used for exposed face work in masonry, flooring, and Ranford brickwork.
  • Second class brick
  1. Small racks and distortions permitted
  2. Water absorption– 22 % of its dry wt.
  3. Cushing strength– should not be less than
  4. Uses– second class bricks are recommended for all unimportant hidden masonry works
PROPERTIES1ST CLASS BRICK2ND CLASS BRICK3RD CLASS BRICKS4TH CLASS BRICK
COLORDeep red cherry or copper colorUniform redPale yellow color as this under burntDark red, bluish color. As this over burnt
WATER ABSORPTION20% of dry weight22% of dry weight25% of dry weightMore than 25 % of dry weight
CRUSHING STRENGTHMinimum crushing strength 10N/mm27.0N/mm2Less then 7.05.0N/mm2
ABRASIONNo impression should be left on a brick when scratched with a nailNo impressionImpression presentImpression is present
IMPACT RESISTANCEShould not break into pieces when dropped from a height of 1.0 meterShould not breakbreakbreak
SOUNDNESSBrick should not break and produce a clear ringing sound when struck with each other.Brick should not break & produce a clear ringing soundDull soundBrick break easily & produce a dull sound
USESFor pointing, exposed masonry workUsed for hidden masonry workFor temporary structureUsed as ballast in lime concrete

CHARACTERISTICS OF GOOD BRICKS

  1. Size and shape – uniform size, rectangular surface with parallel sides and sharp straight edges
  2. Color – uniform deep red color indicative of uniformity in chemical composition and thoroughness in burning
  3. 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
  4. Impacts:- Brick should not break into the piece when – dropped from a height of 1.0 meter
  5. Water absorption – should not exceed 20 % of its dry weight when kept immersed in
    water for 24 hours.
  6. Crushing strength:- Should not be less than 10N/mm2
  7. 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 ) %
  1. It enables the brick to retain its shape and import durability.
  2. It prevents shrinkage and warping
  3. The excess of silica makes the bricks brittle and weak on burning.
  • ALUMINA (20 – 30 ) %
  1. It absorbs water and renders the clay plastic.
  2. If alumina is present in excess of a specified quantity, it produces cracks in brick on drying
  • Lime (10%)
  1. reacts with silica during burning and thus helps to bind it.
  • Magnesia (< 1%)
  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
  1. mainly present in the form of soda or potash
  2. 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

Perforated bricks

  • 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.

Autoclave Bricks

  • 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.

Refractory Bricks

  • 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

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