4. Particles pass through 4.75mm mesh and
remained on 0.15mm mesh.
Commonly used fine aggregates
a) Sand
b) Crushed stone
c) Ash or cinder
d) Surkhi
5. It consists of small grains of silica formed by
the disintegration of rocks.
Qualities of sand
shall be hard,durable,clean,free from
coatings,clay not included
In natural sand the amount of clay and dust
should not be more than 4 percent by weight
In crushed stone it should not be greater
than10 percent
6. a) Pit sand or quarry sand
b) River sand
c) Sea sand
7. a) Pit sand or quarry sand
Found in deposits of soil and has to be
excavated
Grains of it are sharp and angular
As it is free from clay so it is used in mortar
and concrete
b) River sand
Obtained from banks and beds of rivers
It may be fine or coarse.
In fine it may be silt and wash before use.
In coarse form it is clean and is good for every
purpose
8. c) Sea sand
Consists of fine rounded grain of brown
colour and collected from sea bench.
d) Ash or cinder
Obtained in the form of fine grain from
furnaces and are ground with lime for having
strong mortar known as black mortar.
9. Powered of broken brick is usually used as
fine aggregates in lime mortar.
It is prepared by grinding good quality bricks
free from dust and other particles.
The maximum quantity of clay,fine silt and
dust present in it should not exceed more
than 5 percent by weight.
10. It is used to increase the volume of mortar
Reduces shrinkage and cracking of mortar
It helps pure lime to set
11. 1- Rub the sand between the finger. Stains left
on finger will indicate towards clay.
2- Taste of sand will provide us the presence of
salt.
3- Stirring of sand sample in glass of water.
Amount of clay will settle on sand.
4- stir sand in 3 percent of caustic soda and
keep the bottle for 24 hours. Brown colour
will indicate towards organic matter.
12. Particle whose size is more than 4.75mm but
smaller than 7.5mm are known as coarse
aggregates
Commonly used coarse aggregates
1- Stone ballast
2- Gravel or shingle
3- Brick ballast
4- Breeze and clinker
13.
14. Stone free from undesirable mineral are
broken and screened to have stone ballast.
It is an excellent aggregate as it has no
organic matter.
It is used for making concrete, in the
construction of roads and railway track.
15. It is obtained from river beds and sea
shores.
Being hard these are used as an aggregate
for preparation of concrete.
It can contain clay and salt which which is
removed before use.
3- Brick ballast
Broken brick is a coarse aggregate.
It can be used for the replacement of stone.
It is used where low strength is required.
16.
17. These are by-products of burning of coal.
For containing sulphur they corrode steel
and are not used for R.C.C work or beams or
piller.
Being cheap and light material they are used
for internal concrete blocks.
They show expansion when mixed with
cement
18. Size of this aggregate is from 7.5cm to
15cm.
Harmful materials
Aggregates should not contain any harmful
material like clay or any other
impurities.alkali, iron pyrates, shale, coal ,
mica and sea shells etc.
Aggregates should not be chemically
reactive with cement
