LIME
Introduction
Lime is as important binding material in
building construction when it is mixed with sand and water, the mixture is
called Lime mortar and is used to
bind bricks and stones in walls of buildings and as plaster on walls. When it
is mixed with sand, coarse aggregate and water, the mixture is called Lime-concrete and is used as filler
material for foundations and as base course for flooring etc.,
Sources of Lime
The lime is not
generally found in nature in the free state but it is obtained by burning one
of the following materials.
1. Lime stone presents
in lime stone hills.-
2. Lime stone
builders found in the beds of old rivers.
3. Kankar found below
ground.
4. Shells of sea
animals.
Pure limestone - White chalk
Impure limestone.- kankar
Classification of lime
On of the basis contents of pure
calcium carbonate, lime may classified into the following three categories.
1. Fat lime
2. Hydraulic lime
3. Poor lime or lean
lime
Fat lime
This lime is obtained
by burning pure limestone. The time from which this lime is obtained should
contain about 1.41 95% of calcium oxide and about 5% of other materials in
the form of impurities. This lime is known as fat lime, because, it increase 2 to 3 times in volume, when slaked.
Properties
Ø Its colour is perfectly white
Ø It slakes vigorously
Ø It is easily soluble in water
Ø It swells 2 to 3 times after slaking
Ø In the presence of air it will sets slowly
Ø It has high degree of plasticity
Uses
Ø It is used in white washing.
Ø It is used in plastering.
Ø Its mortar with sand can be used in masonary
works.
Hydraulic lime
It is produced from lime stone of
'kankar' containing calcium carbonate. 10 to 30% of clay, magnesium carbonate,
and oxides of alumina, iron and carbon. During slaking its volume increases
slightly. As it has properties of hardening and setting under water it is
called Hydraulic lime. It is also
called water lime.
Properties
Ø It slakes very slowly
Ø It hardness
Ø It sets under water
Ø It is not perfectly white
Ø It does not dissolve in water
Works
Depending upon the percentage of clay
hydraulic lime is divided into three types.
a. Feebly hydraulic
lime
b. Moderately
hydraulic lime
c. Eminently
hydraulic lime
Feebly hydraulic lime
The lime containing 5 to 10% of clay
impart hydraulic properties in a very feeble manner and hence it is called
feeble hydraulic lime. This lime slakes after a few minutes. It sets in water
to 3 weeks. The mortar produced by this is not so stronger than other types and
hence it can be used for ordinary masonry work.
Moderately hydraulic lime
The lime containing 11 to 20%
of clay imports moderate hydraulic properties and hence it is called moderately
hydraulic lime. If slakes after one or two hours. It sets in water in one week.
If may be used for superior type of masonry work.
Eminently hydraulic lime
The lime containing 21 to 30%
of clay is eminently hydraulic lime. It may set in water in day, the mortar
produced by using this lime is stronger, and it is used for aqueous foundations
etc.,
Uses of hydraulic lime
Ø It is mainly used in lime concrete.
Ø Its mortar with sand may be used for masonry
works.
Ø It is used for white washing.
Ø It is used for soil stabilization.
Ø It is used in water purification process.
Poor lime
If the production of clay is more than 30
percent, it has poor cementing properties, never gain any hydraulicity and sets
or hardness very slowly. Therefore it is called poor lime.
Uses of lime
1. As a matric for
concrete.
2. For making mortar
for use in brick or stone masonry.
3. For plastering
walls, ceilings etc.,
4. For white washing
and as a base for distempers.
5. It is used for the
production of artificial stone, lime, sand bricks.
6. It is used in the
manufacture of paint.
7. As a flux in metallurgical
industry.
8. For soil stabilization
and for improving soil the agricultural purpose.
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