Natural sand are weathered and worn out particles of rocks and are of various grades or size depending on the accounting of wearing. The main natural and cheapest resource of sand is river. Dams are constructed on every river hence these resources are erasing very fast. Now a days good sand is not readily available, it should be transported from long distance. Those resources are also exhausting very rapidly. So it is a need of the time to find some substitute to natural river sand.
The artificial sand produced by proper machines can be a better substitute to river sand. The sand should be sharp, clean and course. The grains should be of durable material. The grain sizes must be such that it should give minimum voids. The presence of clay and silt retards the setting of the cement and makes the mortar weaker and the walls or the slab leaks and holds dampness.
The sand in the mortar does not add any strength but it is used as an adulterant for economy and with the same it prevents the shrinkage and cracking of mortar in setting. The sand must be of proper gradation ( it should have particles from 150 microns to 4.75 mm in proper proprtion) When fine particles are in proper proprtion, the sand will have less voids. The cement required will be less when there will be less void in sand. Such sand will be more economical.
Only sand manufactured by V.S.I. Crusher is cubical and angular in shape. Sand made by other types of machines is flaky , which is troublesome in working. There is no plasticity in the mortar. Hence the mason are not ready to work with machine made crushed stone sand. For the same reason inferior river sand may be used. Manufacturing sand from jaw crusher, cone crusher, roll crusher often contains high percentage of dust and have flaky paricle. Flaky and angular particles may produce harsh concrete, and may result in spongy concrete.
There is standard specification for Fine aggregates (Sand). It is divided in four gradations. Generally known as Zone I, Zone II, Zone III and Zone IV. There is sieve Designation for each grade. Gradation is made as per the use of the sand. There are testing sieves for testing the sand. A set of Sieves with square hole is available. Followings are the sieves
- 4.75 mm,2.365,1.1830,600 microns,300 microns,150 microns
- pan
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