HARMFUL INGREDIENTS IN BRICK EARTH

1- LIME

  • If Lime is present in excess , colour of bricks changes from Red to Yellow 
  • When lime is present in lumps, it absorbs moisture , swells and causes disintegration of the bricks. Hence lime should be present in finely divided state , and lumps should be removed in the beginning itself 
2- IRON PYRITES 
  • IF IRON PYRITES ARE PRESENT IN BRICK earth , then bricks tend to oxidise and decompose during burning and may split into pieces 
  • PYRITES discolourise the brick 
3 - PEBBLES , GRAVELS , GRITS 

  • BRICKS containing pebbles will not break regularly as desired.
  • It does not allows clay to be mixed uniformly and thoroughly which will result in weak and porous bricks .
4 - ALKALIES 

  • Excess of alkalies causes brick to melt and loose their shape 
  • These causes Efflorescence- When bricks comes in contact with moisture , water is absorbed and the alkalies crystallise. On drying , the moisture evaporates , leaving behind gray or white powder deposit on the brick which spoil the appearance and this phenomenon is called as efforescence . 
5 - ORGANIC MATTER 

  • During burning of bricks, organic matter gets burnt completely , leaving behind pores and hence making bricks porous .
  • It also absorbs water and therefore reduces strength of brick. 
6- WATER

  • A large amount of free water causes shrinkage of bricks on drying , whereas combined water causes shrinkage during burning 
7 SULPHUR 

  • IF sulphur is present in brick earth and insufficient time is given ( during burning ) for oxidation of carbon and sulphur, then sulphur will cause the formation of a spongy , swollen structure in the brick and the brick will be decoloured by white blotches

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