M SAND – AN ALTERNATE FOR RIVER SAND DURING SHORTAGE SUPPLY IN TAMIL NADU

DATED: 19-12-2017  

Manufactured sand

Before we get into the advantages and disadvantages of manufactured sand, what exactly is manufactured sand? Manufactured sand is sand produced by crushing rocks, quarry stones or larger aggregates pieces into sand-sized particles. Natural sand, on the other hand is the naturally formed sand extracted from river beds.

The Manufacturing Process

Rocks or quarry stones are blasted and subjected to a series of crushing cycles to reduce the particles to the size of naturally occurring sand.

The produced sand is then sieved and washed to remove fine particles and impurities, and tested for various quality aspects before it is deemed fit as a construction aggregate. The size specification for manufactured sand is that it should pass completely through a 3/8 inch sieve.

Why Manufactured Sand?

There are various factors that are currently driving the production of manufactured sand:

• Global scarcity for natural sand: Injudicious sand mining and continuous depletion of natural aggregate sources have led to the implementation of new environmental/land use legislations which has made the procurement of natural sand difficult and expensive. Sand dredging is heavily taxed/ banned in many parts of the world.

• Growing demand for fine-aggregates in construction: Nearly 65-80% of the volume of concrete and screed mixes is made up of sand/aggregates. The UK market alone requires an approximate 200 Million Tonnes of aggregates every year for various construction purposes.

• Remote location of sand pits: Licensed sand pits producing the required quality of sand are often located in remote locations, leading to and high costs in transportation.

• Presence of silt and clay in natural sand:  Natural sand is inherently high in silt and clay. It can be damaging for screed and concrete, if the sand is not sufficiently processed to bring down clay and other impurity content to acceptable levels.

• Reduce the wastage of low-value by-products in the quarries: The low value aggregates formed as a by-product of rock crushing can be utilized efficiently to create a high value product.

The Advantages of Manufactured Sand

• More cost effective than natural sand: Manufactured sand can be produced in areas closer to construction sites, bringing down the cost of transportation and providing an assurance of consistent supply.

• Compliant with the new European Standards: Manufactured sand can be used as aggregates in screed and concrete mixes, as per EN13139. It can be used as a replacement or as a blended mixture with natural sand.

• Less disruptive to the environment: The land used for quarrying rock can be reclaimed for commercial/residential purposes or used for wetland restoration. This can help in reducing the sand mining from river beds.

• Lesser impurities and good working properties: Manufactured sand is free of silt and clay particles, and has denser particle packing than natural sand. It also offers higher flexural strength, better abrasion resistance, higher unit weight and lower permeability.

The Disadvantages

Workability issues:  Manufactured sand can be of a coarser and angular texture than natural sand, which is smooth and rounded due to natural gradation. This can lead to more water and cement requirement to achieve the expected workability, leading to increased costs.

Larger proportion of micro fines: Manufactured sand can contain larger amounts of micro fine particles than natural sand, owing to its production process. This again can affect the strength and workability of the screed or concrete.

The solution:

Fine crushing and separation requires specialist knowledge and technology. To ensure the manufactured sand is fit for purpose, the end product should be put through a series of quality tests such as:

• Sieve analysis
• Optical microscopic study to check the particle shape
• Workability
• Cube test for compressive strength
• Adulteration test

Manufactured sand can be as an economic and more eco-friendly alternative to natural sand. But, the key is to ensure the sand is procured from a reliable source and that it has been adequately processed and tested to meet the required quality specifications.