What Is Fine Aggregate?
Types of Fine Aggregates (Classification)
Fine aggregates are classified as follows:
1. Mode of origin
3. Grain size
Classification according to Mode of Origin
• Pit Sand
• River Sand
• Sea Sand
They are sharp and angular in outline. Translation and deposition are done by the wind. Such sand accumulation is sometimes covered by clay.
It will be desirable to wash and clean this type of sand before use.
River sand is found in the river bed in-plane area. Grains of river sand is round in shape. This sand is clean and free from salt encrustations.
No organic impurities are noticed. This sand is commonly for construction work.
This type of sand is found on beaches and along sea-shore. These sand particles are round in shape. Grains are often found covered with salts that are not easily separated.
These salts, when coming in contact with binding material of mortar or concrete, create problems.
Further, these salts encrustations are hygroscopic. They absorb water from the atmosphere and delays setting.
They produce dampness and efflorescence. Hence the type of sand is not preferred. They should be thoroughly washed before use.
Classification of Fine Aggregates According to Composition
• Clean Sand
• Silty Sand
• Clayey Sand
These are well-graded sand containing quartz particles in a wide range of grain sizes.
These are poorly graded, having a considerable proportion of silt and other non-plastic fines.
There is poorly graded sand that has a prominent clay fraction and also plastic fines.
Classification Fine Aggregate According to Grain Size
According to this classification sands are classified as under,
|2 – 1 mm||Coarse|
|1 – 0.25 mm||Medium|
|0.25 – 0.15 mm||Fine|
Fine Aggregate Size Requirement As Per IS 456
If you remember, I have mentioned the size of the fine aggregate as recommended by IS. Let me recall. The aggregates passing through 4.75 mm sieve and retained on 0.15 mm sieve are called fine aggregates.
Different size of sand is necessary for different works. For sand some times terms like fine sand, medium sand, and coarse sand are use.
It is difficult to distinguish one type of sand from others when such terms are used. It is advisable to express sand in terms of fineness modulus.
According to F.M. sand can be classified as under
|Type of Sand||Range of Fineness|
|Fine Sand||2.2 – 2.6|
|Medium Sand||2.6 -2.9|
|Coarse Sand||2.9 – 3.2|
Sand having a fineness modulus more than 3.2 will not be suitable for making satisfactory concrete.
As I have stated earlier considering grain size, types of sand will be as under,
|Type of Sand||Grain Size|
|Coarse Sand||2-1 mm|
|Medium Sand||1 – 0.25 mm|
|Fine Sand||0.25 – 0.15 mm|
Use of Ine Aggregate for General and Specific Purpose.
As per below type of sand
• Use of sand for general purposes
• Specific Uses of Sand
Use of sand for general purposes
• Preparing mortar for masonry work.
• Preparing mortar for different types of plastering and paintings.
• Preaparinf concrete for a slab, beams, columns, etc.
• Filling in trenches
• Levelling ground
• Foundation Concrete
• Different types of precast units, tiles, concrete pipes, etc.
Specific Uses of Sand
Sand can be used for many specific purposes; some important uses are mentioned below.
• To safeguard foundations in back cotton soil.
• Filling in breaches of canal banks.
• Temporary cofferdam
• Blotting excessive of bitumen from the surface of the road.
• For playgrounds
• Moulding works
• Sand-blasting for cleaning
• Counter-weights (Sand Bages)