Sand
These are fine particles of silica that are formed
by the breaking of rocks. This type of fine aggregate is the most widely used
because it has more advantages than all other types of fine aggregate. The use
of sand reduces the compression effect, increases the void between the
components and helps the lime to harden.
Type
of Sand
Sand used in
construction works is obtained from various sources. The type of sand is
determined by the suitability of these sources. The different types of sand are
as follows.
·
Pit Sand
·
River Sand
·
Sea Sand
Pit
Sand
This sand naturally takes the form of a reservoir in
the earth which is dug out of the ground.
This type of sand is granular and hard so it is considered better in
construction works.
River
Sand
This type is derived from riverbanks and foothills. It
is thin and thick. Thick sand is considered better in construction works. Fine
sand contains dust and dirt. If fine sand is available, it should be washed
before use.
Sea
Sand
This sand comes from the beach. The grains of this
sand are round in shape. Because of seawater, it contains a lot of salts that
are capable of absorbing land from the air. Therefore the use of this type of
sand damages the construction work and the building and other mega structures.
If other types of sand are not available, then should be washed thoroughly and
used. This sand Should not be used in RCC works as salts cause rust to rust
very quickly as the building begins to deteriorate.
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| Type of Sand |
Size
of The Sand
The
following classifications of sand can be made according to size.
·
Coarse Sand
·
Medium Sand
·
Fine Sand
Coarse
Sand
This sand is usually pit sand. Its size varies from 0.5
millimeter to 2.0 millimeters. It is used to make concrete.
Medium
Sand
This type of sand is river sand. Its size varies
from 0.2 millimeter to 0.5 millimeters. It is used in the preparation of concrete
and in plastering.
Fine
Sand
It is usually pit sand and can be river sand. Its
size varies from 0.1 millimeter to 0.2 millimeters. It is used in mortar for
plastering.
Qualities
of Good Sand
Good sand has the following properties
·
The sand should be thick and granular.
·
Sand particles should be hard, strong
and long lasting.
·
The sand should be free of dust and
dirt.
·
Sand should not contain salts.
·
All sand particles should not be the
same size but should be thick and fine.
·
Sand should not contain organic matter.
·
Sand should not contain water-absorbing
ingredients
Bulking
of Sand
The volume of dry sand increases due to moisture
reaching. This ability of sand is called sand bulking of sand. The sand used in
construction works is not 100% dry. Bulking of sand is 25% due to about 4% moisture
content. Excess moisture reduces the spread of sand. 20 percent moisture
content of sand is very low. Fine sand has more bulking than coarse sand. Moisture
actually causes the water layer to freeze around the sand particles. As the
distance between the sand particles increases, so does the volume of the sand. Bulking
should be considered when choosing sand.
Tests
of Sand
The sand is tested in the field in the following
method before being used in the preparation of mortar and concrete.
·
Some amount of sand is held in the hand
and fought with the help of fingers. If rubbing shows marks on the fingers,
there will be dirt and dust in the sand.
·
Taste of sand detects the presence of
salts.
·
Some amount of sand is poured into a
glass of water and stirred well. After shaking, the water is left to settle. In
the presence of dust and dirt, these things will accumulate in the bottom of
the glass.
·
To detect the presence of organic
matter, the bottle is sealed by shaking well with a 3% caustic soda solution in
a sealed bottle. After 24 hours, if the water turns brown, the sand will
contain salty organic matter. The darker the color of the water, the more
organic matter there will be in the sand.
Uses
of Sand
The use of sand in civil engineering works is very
high. In the preparation of concrete, both coarse and fine sand should be used.
The thicker sand is called hero sand which is pit sand. Medium and fine sand is
obtained from the river. Medium and fine sand mixtures are used in the
preparation of plaster. Sand used for making or plastering concrete should be
free of organic matter and dust. It is best to sift it before use. So that
large size unnecessary and organic items can be separated. If there is more
dust in the sand, it should be washed before use. Sand is used as a filling for
flooring. Its use makes the floor strong and long lasting. Sea sand contains a
lot of salts which reduces the durability of concrete. Such sand should not be
used in concrete as the organic matter contained in such sand quickly corrodes
the iron ore. If used in case of compulsion, concrete covers should be provided
thicker.
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