Sand is a naturally occurring inorganic substance made up of granulated rocks. Considered as one of the prerequisites for the development of infrastructures, it is of supreme importance in our daily chores.
Requirements of good quality sand
- Sand should be clean, any particles disturbing the neutrality of it should not be there.
- The sand used should be a well-graded mixture from coarser to fine grains, complying with the requirements of IS 383 Latest edition or equivalent.
- For plastering purposes, the fine sand used must not have a modulus less than 1.5 and white slits are preferred not less than 4 percent.
- For brickwork, fine sand used must not have a modulus less than 1.2 to 1.5, and the slit preferred is generally 4 percent.
- Concreting works require coarse sand with a modulus of 2.5 to 3.5 and the slit content must not be less than 4 percent.
- None of the organic matter should be included here.
- There must not be the presence of the trace of earth units.
Types of Sand & Classification of Sand
Followings are the classification of Sand:
- Based on the grain size of the particle, sand is classified as Fine Sand(0.075 to 0.425mm), Medium Sand(0.425 to 2mm), and Coarse Sand(2.0 mm to 4.75mm)
- Based on origin, sand is classified as Pit sand, River sand, Sea sand, and manufactured sand.
Followings are the widely used types of sand:
This is a type of coarse sand that is commonly found in red-orange color. It is secured from deep pits dug 1 to 2 meters from below the topsoil.
The grains of pit sand is rough, angular, sharp and harsh. It is free from salts and other impurities because of which it is a conventional selection for concreting.
River sand is a type of fine sand formed by the corrosion from water current and is
obtained from river streams and banks. It is generally white-grey. Unlike pit sand, the grains of river sand is smooth, rounded and of fine quality.
Hence, it is used globally for a broad range of construction purposes such as plastering.
Sea sand (also known as offshore sand) refers to the sand eroded by seawater. It is secured from seashores and has a distinct brown colour.
The grains of sea sand is very fine in quality with a circular shape. Sea sand consists of salt and other marine impurities which tend to absorb atmospheric moistness and bring forth dampness.
Therefore it is avoided for concrete structure and engineering techniques.
Created by crushing hard granite stones, manufactured sand refers to an artificially created type of sand made as an alternative to river sand for construction.
It is prepared with the required gradation of fineness, shape, surface smoothness, texture, and consistency making it the best sand suitable for construction while providing with greater strength to the concrete by reducing segregation during placing, bleeding, honeycombing, voids, and capillary.
Furthermore, its usage also prevents dredging of river beds to obtain river sand, helping to avoid disasters like groundwater depletion, water scarcity, threat to bridge safety thus making it a more eco-friendly alternative to other sands.
Sieve Analysis of sand
A sieve analysis (gradation test) is a method or procedure used to access the particle size distribution of granular material and to determine its compliance with design, production control requirements, and verification specifications.
The size distribution is often of significant concern to comprehend the way the material functions during usage.
Sieve analysis Procedure:
- Take a typical oven-dried sample of sand that weighs about 500gms.
- Determine the exact mass of the sample.
- Prepare a stack of sieves and place the sieves of sizes 4.75mm, 2.36mm, 1.18mm, 600u, 300u, 150u, and 75u with larger opening sizes above the ones having smaller opening sizes. A pan is placed at the bottom to collect the portion of sand passing through all sieves.
- Pour the sand into the stack of sieves from the top and place the cover. Then fix the stack in the sieve shaker and shake for 10 – 15 minutes.
- Stop the sieve shaker and measure the mass of the retained sand in each of the sieve.
Follow the sample format given below to obtain particle size distribution.
Description of soil………………………… Sample no: …………………….
Mass of oven-dry sample, W ………. s
Tested by………………………………………… Date: …………………….
|Sieve no.||Sieve Opening||Mass in gram of soil retained on each sieve||Percentage of mass retained on each sieve, R||Cummulative percentage retained, ⅀R||Percentage finer, ⅀R/100|
Fineness modulus is an empirical factor obtained by the sum of the total percentages of a sample of the aggregate retained on each of the specified series of sieves per 100.
i.e. Fineness modulus (F.M.) = Sum of Cummulated percentage retained / 100
= ⅀R/ 100
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