What is sand? Types of Sand on the basis of Source, Geological origin, Sieve analysis.
Sand is a granular material that occurs from the disintegration of rocks having a particle size smaller than gravel but having a higher size than silt and used as a construction material for the preparation of concrete, mortar, etc.
Types of Sand on the basis of source
There is a different type of sand that is used for construction work. Few are explained below:
It is obtained by forming pits into soils from quarries. Fine Aggregate is free from salts and it is coarse in nature. IT consists of sharp, angular, and rough grains. It is obtained by digging the pit.
Color: Color of Pit sand is normally reddish-yellow. It doesn’t contain any salt.
It is obtained from the banks of the river. T is obtained in the form of fine rounded grains. It is generally found in clean condition. It is used for concreting and plastering.
Color: A color of River sand is white and grayish.
It consists of rounded grains and obtained from seashores. Fine Aggregates contains salts that attract moisture from the atmosphere and cause dampness. It is used for concrete making. It is Fine type of material.
Color: The color of sea sand is light brown.
- It reduces the setting time of cement because of that we generally do not recommend for construction work.
- Salt contains sodium chloride which causes corrosion to reinforcement.
It is produced by crushing either basalt rock or granite. It is a well-graded and coarser type.
Note: Sea sand should not be used because it creates corrosion of reinforcement, setting, and hardening of concrete.
Types of sand on the Basis of Geological Origin
Natural aggregates are the aggregates which are occurred from quarries from rocks such as Igneous, sedimentary and metamorphic. These obtained aggregates required the sieving process and washing for the suitability of concrete preparation.
Artificial aggregates such as broken bricks, blast furnace slag, synthetic aggregates. Blast furnace slag aggregate has excellent fire resistance properties and it is obtained from slow cooling of slag by crushing.
Types of Sand on the Basis of Sieve Analysis
Fine Aggregates is a construction material that is retained on 75 microns I.S. sieve but it passing through 4.75mm I.S. sieve.
IS Sieve that is used for fine aggregate Grading (As per IS:383)
10mm, 4.75mm, 2.36mm, 1.18mm, 600 micron, 300micron, 150micron.
Fineness modulus of Fine Aggregate
Fineness modulus is obtained adding the percentage of the weight of fine aggregate retained on each sieve and dividing by 100.
Type of sand fineness Modulus Range
Fine sand 2.2-2.6
Coarse Sand 2.9- 3.2
Note: IF the fine aggregate has higher fineness modulus value that means the Fine aggregate is coarser and smaller fineness modulus values indicate that aggregate is finer.
The particles which are retained on 4.75 mm sieve. Coarse Aggregates are larger in size as compared to fine aggregates.
IS sieve used for Coarse Aggregates (As per IS:383)
80 mm, 63 mm, 40 mm, 20 mm, 16 mm, 12.5 mm 10 mm, 4.75 mm, 2.36 mm.
Fineness modulus is the cumulative percentage of the weight of the sample retained on various sizes and dividing by 100. For 20mm, Coarse aggregate, fineness modulus ranges from 6 to 7.
For coarse particle size Fineness Modulus
20 mm 6 to 6.9
40 mm 6.9 to 7.5
75 mm 7.5 to 8.
Properties of Good Quality of Fine Aggregates
- Fine aggregates should be free from lumps, silt and Organic impurities like habitats, Vegetable matter, grass, etc which affect the setting and binding property of concrete
- It should be chemically inert.
- It should be free from silt and clay.
- Fine Aggregates should not contain more than 3 percent of silt.
- It should not contain salts that contain sodium chloride that causes corrosion to reinforcement.