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MANUFACTURING OF LIME MORTAR
CLASSIFICATION OF
LIME:
Broadly lime is
classified into three categories:
(1) Fat Lime
(2) Hydraulic lime (3) Poor Lime
(1) Fat Lime/Pure Lime
/Slaked/High Calcium
or Non-Hydraulic Lime:- Fat lime is also known
as pure lime, white lime or rich lime, this is manufactured using the purest
form of the limestone. It is popular with its name as fat lime since its volume
is increased to about 2 to 2.5 times its originally volume after getting slaked.
It slakes vigorously.
(2) Hydraulic
Lime: This
lime has the hydraulic property, means it can set under the water also. It
contains clay and some amount of ferrous oxide also. This is also known as
water lime.Depending upon the amount of clay hydraulic lime is classified into
further three categories:
(a) Feebly hydraulic
lime
(b) Moderately
hydraulic lime
(c) Eminently
hydraulic lime
Increase in the
percentage of clay makes the slaking difficult and thus increases the hydraulic
property of lime. With about 30 per cent of clay lime resembles the color of
cement.
The color of fat lime
is not white therefore fat lime looks more sanitary than the hydraulic lime.
(3) Poor Lime: Poor lime contains
more than 30 percent of clay therefore it is also known as impure lime. It
slakes very slowly and also does not dissolve into water. It has poor binding
property and its color is muddy white.
This lime forms very
poor mortar and so such lime can be used for inferior types of work or at
places where good lime is not available.
BIS: 712 - 1984 classification
lime under six categories, namely Class A,
Class B, Class C, Class D, Class E and Class F.
Class A
lime is used for
structural purposes because it is eminently hydraulic lime and has the property
of setting even in the absence of air. It has to be supplies in the hydraulic
form only. Its minimum strength with lime sand mortar of proportion(1:3) by
weight at the end of 14 days and 28 days should be respectively 1.75 N/mm2 and
2.80 N/mm2.
Class B
lime is the semi-hydraulic lime which is used for
mortars for masonry and it can be supplied either as quick lime or as hydrated
lime. Its minimum compressive strength with lime sand mortar of proportion(1:3)
by weight at the end of 14 days and 28 days should be respectively 1.25 N/mm2
and 1.75 N/mm2.
Class C
lime is the fat lime which is used mainly
for finishing coat in plastering, whitewashing and with suitable admixture such
as surkhi or any other pozzolanic material to produce artificial hydraulic
mortars. It is to be supplied in hydraulic or quick form.
Class D
lime is the magnesium
or dolomitic
lime
which is used for finishing coat in plastering, whitewashing, etc. It is to be
supplied in the hydrated or quick form.
Class E
lime is the kankar lime and is used for the
masonry works. It is produced by burning lime nodules which
are seen in soils like black cotton soil containing silica in the hydrated
form.
Class F
lime is also known as Siliceous dolomitic lime which is used for undercoat and finishing coat of plaster. It is to be supplied in the hydrated or quick form.
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