SAND
It consists of small grains of silica and is formed by the
disintegration of rocks caused by weather.
Classification of Sands
The classifications of sand are;
Fine sand,
medium sand,
and coarse sand
Fine sand = 0.075 to 0.425 MM
Medium sand = 0.425 to 2 MM
Coarse Sand = 2.0 to 4.75 MM
Various type of sand
Depending upon the source from which sand is obtained it is
classified as
1)
Pit sand (coarse sand)
2)
River sand
3)
Sea sand
1) Pit Sand
(coarse sand)
It is found as deposits in soil
and has to be excavated out. It consists of sharp angular grain which is free
from salt. It is coarse sand, reddish yellow in color, and is used in
concreting normally
2) River
Sand
This is obtained from the bank and bed of
rivers. It usually consists of fine rounded grains.it may be fine or coarse
sand. It is normally white and grayish in color. It is widely used for
plastering and is available in clean condition
3) Sea
Sand
This is obtained from sea shores. It is
brown in color and it also has the fine rounded grain. As it is obtained from
sea it contains salt, which is used in attracting moisture from atmosphere.
Such absorption causes dampness and disintegration of work. It is generally not
used for engineering purpose due to its retards setting action of cement. It is
normally used for non-structural purposes
Bulking Of Sand
It is the property of sand by virtue of
which its apparent volume increases when some water is added to it. It happens
mainly due to surface tension.
This increase in volume will not take place
when the sand is either dry or fully saturated.
The bulking depends both on moisture
content as well as particle size Bulking increases gradually with the increase
in moisture content.at 4% increase in moisture content by weight, the increase
in volume is about 25 percent.it then decreases with the increase in moisture
content till it become zero when the water is more than 20%.
Bulking is more in fine sand than in coarser
one.
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