SAND USED IN CONSTRUCTION AND THEIR CLASSIFICATION

Sand is a mixture of small grains of rock and granular materials which is mainly defined by size, being finer than gravel and coarser than silt. And ranging in size from 0.06 mm to 2 mm. Particles which are larger than 0.0078125 mm but smaller than 0.0625 mm are termed silt.

Sand is made by erosion or broken pebbles and weathering of rocks, which is carried by seas or rivers. And freezing and thawing during the winter break rock up the sand will be made. Sometimes Sand on beaches can also be made by small broken-up pieces of coral, bone, and shell, which are broken up by predators and then battered by the sea, and even tiny pieces of glass from bottles discarded in the sea and other mineral materials or the bones of fishes or other oceanic animals. Sand can be also considered as a textural class of soil or soil type. A sandy soil containing more than 85 percent sand-sized particles by mass.

Followings are the classification of Sand:  

1. 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)
2. Based on origin, sand is classified as Pit sand, River sand, Sea sand, and manufactured sand.

Sand used in building construction

Followings are the widely used types of sand:

Pit 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: 

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: 

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.

Manufactured Sand: 

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.