* introduction:- in this topic we will learn about harmful ingredients in brick and their effects, we know that main composition of good quality bricks is silica, Alumina ,magnesia, iron pyrites and small amount of alkali in desirable quantity proportion. more or less than desirable amount of its constituent make brick shrinkage warping decolour and brittle and having little strength.
* main harmful ingredient in bricks:–
harmful ingredient in brick and their effects are following :-lime ,iron pyrites ,pebbles gravel And grit, alkali ,organic material ,water and sulphur.
1)Lime:- if lime is present in clay brick excess amount it causes change of colour of brick from red to yellow and when lime is burn in lamp it absorb water and swell and brick become disintegrated, so lime should be present in bricks as fine graded material if there is present it might be removed in beginning process.
2) iron pyrites :-iron pyrites is necessary ingredient of red clay brick it is small amount burn in the presence of Oxygen and provide red colour to bricks ,but excess amount of pyrites decolourise the bricks to dark red black or blue black colour of brick.
3) pebbles gravels And grits:-it can not be allow to mix with pebbles gravels and grit , because it can make brick porous and lose their strength and water absorbing capacity is increased.
4)Alkalies :- excess of alkali metal causes bricks to melt and lose their shape these causes effluorescence. When bricks with alkalies come in contact with moisture moisture is absorb and alkali material crystallized on drying of bricks ,when water is evaporated and crystallized material form white powder deposit on the bricks which destroy and spoil the appearance of bricks this phenomenon is known as effluorescence.
5) organic material:- no organic material is allowed to mix with clay of bricks because on burning ,it is completely burn and left vacant space in brick and make brick porous and lose their strength and higher water absorbing capacity.
6) water :-quantity of water causes shrinkage of bricks on drying and combine water causes shrinkage of brick during burning in hot furnace.
7) sulphur :-if sulphur is present in clay of brick it provides oxidation of carbon and sulphur .during burning sulphur provides spongy and swelling structure of white patches on brick and brick become decoloure due to white patches.
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