Lime in its raw or unhydrated form requires careful handling to avoid accident and losses.
A) Quick Lime :
Quick Lime should be protected from water while handling for transport or during storage.It will start getting hydrated with evolution of heat that can cause burn injuries of very serious nature.
When lime stoared in wooden barrels comes in contact with water , so much heat may be evolved as to burn the barrels and also the store house or the trucks or wagons in which it is being transported.
B) fat Lime :
Fat lime must be protected from direct contact with atmosphere moisture & carbon dioxide. Uncovered lime gets air-slaked,that is, gets slowly hydrated by absorbing moisture from the atmosphere.
Such slacked-lime then combines with atmospheric carbon dioxide and starts setting.
It gets converted to a useless hard material which is lift with very little or no binding properties
However,stored temporarily for some time b y pilling it up into a compact heap which is covered with a thick layer of lime dust.This dust saves the main heap from the attack of moist air.
C) Hydraulic Lime :
It safer in transport & can be stored for longer periods as compared to fat lime. It must be treated as a lime & not as a cement & same precautions taken while working with it.
Lime is an important cementing material used in engineering construction. A cementing material may be defined as that material which has the capacity of holding structural units (like bricks, stones, aggregate) together with sufficient strength.
LIME in its simplest form is an oxide of calcium, CaO. It has been used since ancient times in the construction of ordinary buildings and also massive monuments, palaces and forts.
In the present time, lime can be used as reliable and economical cementing material where portland cement is either costly or is not easily available as in hilly regions and remote villages.
Classification :
LIME is available in the market in three main types which are named on the basis of its composition:
Quicklime, hydrated lime and hydraulic lime.
A) Quick Lime / Fat Lime :
It is also called fat lime, rich lime or pure lime. In it CaO content is always greater than 93 percent by weight remaining being MgO and very little clay .
Quicklime is an amorphous (shapeless) white , material which
is highly caustic in character. It has a very high affinity for water and
carbon dioxide. It will absorb the same quickly even from atmosphere converting
itself to a carbonate of calcium, as per following reactions
CaO +Co2 =
CaCO3
CaO + H2O
=Ca(OH)2
Ca(OH)2 + CO2 = CaCO3 + H2O
1)It hardens very slowly.
2)It has high degree of plasticity.
3) Its colour is perfectly White.
4) It sets slowly in presence of Air.
5) It is soluble in water which is changed frequently.
Uses – White washing , plastering , Lime mortar can be used for thin joints of brick work & stone works.
B) Hydrated Lime :
It is that lime to which sufficient quantity of water has already been added at the manufacturing stage to hydrate (slake) it completely.
In composition hydrated lime is Ca(OH)2.in structure. It may be a fine powder.
It comes in ready to use form compared to fat- lime that has to be hydrated or slaked before using. Lime can also be converted to hydrated form at the place of construction. The method is then called slaking of lime.
C) Hydraulic Lime :
It is different in chemical composition form fat lime in that it contains a definite amount of clay in addition to CaO.
The clay content in hydraulic limes may range form 10-30 percent by weight. This clay plus lime composition gives the hydraulic lime a property of hydraulicity.
Which
may be defined as “the capacity to set and harden even under water and in the
absence of air as between very thick walls.”
The hydraulic lime is further classified into three sub-types on the basis of hydraulicity (which is actually related to the clay content ) of the lime.
Divided into following three type :
1)Feebly Hydraulic Lime :
Clay content 5 to 10% , Slakes after few minutes , Sets in water in 3 weeks or so,Feeble.
Uses : The mortar produced by this lime is reasonably strong. Ordinary Masonry Work
2) Moderately Hydraulic Lime :
Clay content 11 to 20% , Slakes after one hour or two hours , Sets in water in a weeks or so,Moderate.
Uses : The mortar produced by this lime is reasonably strong. Superior Masonry Work.
3) Eminently Hydraulic Lime :
Clay content 21 to 30% , Slakes with difficulty , sets in water in a day or so, Eminent.
Uses : The mortar produced by this lime is similar the ordinary cement , It can be used for damp places.
Tanya Decor 