Artificial sand now a ?natural? choice for quarries

The market for manufactured sand is growing rapidly. Worldwide restrictions on the use of natural sand are one major reason that quarries all over the globe are starting up sand manufacturing plants. In Malaysia, Thailand and other countries, governments have called an indefinite halt to the excavation of natural sand.

?Deforestation and coastal extraction of natural sand have resulted in huge environmental problems,? says George Fensome, market and sales manager for crushers at Sandvik Mining and Construction. ?Erosion of the existing topography can result in flooding and landslides.

More importantly, the natural filtration of rain water achieved by deposits of natural sand is being lost, thereby causing contamination of water reserves used for human consumption.?

In the quarry business, more and more people are becoming aware of the benefits of manufactured sand. Customers are urgently requesting manufactured sand projects and systems, largely because of environmental and political considerations.

Eduardo Lanna of TCL Group was the first producer in Brazil to realise the full potential and put into practice a working system for manufactured sand.

The vertical shaft impactor (VSI) is an autogenous (rock-on-rock) crusher. Three main crushing actions ? impact, cleavage and attrition ? occur simultaneously within the crushing chamber. The autogenous crushing action of the Sandvik CV-series VSI crusher ensures consistency of product gradation and excellent particle shape.

What are the advantages of manufactured sand compared with natural sand?
If clean, pre-crushed rock is used to make manufactured sand, it doesn?t have to be washed or screened before processing. Consistency of product gradation and shape for road construction is always maintained with autogenous VSI crushing. The benefits include good fines content for asphalt and excellent particle shape in the larger fraction sizes. This is particularly important to achieve good polished stone value (PSV) ratings.

?The main challenge to overcome was changing the existing culture of using natural sand,? Eduardo Lanna says. ?Most of our customers are accustomed to using natural sand due to culture, low cost and availability.?

Eduardo Lanna?s path to success in the sand market came by proving the benefits of his product and demonstrating the rock hard facts to his customers. His studies confirmed the findings of Sandvik with regard to their VSI crusher data.

?After many lab tests, the results showed that it was possible to reduce the amount of cement and water required to produce concrete using manufactured sand,? Eduardo Lanna says. ?Concrete compression resistance also increased.?

Since then, even more applications have arisen. The use of VSI manufactured sand and aggregate for high quality road construction has been instrumental in both achieving and exceeding high international quality standards.

?We have an excellent application that verifies these points, specifically a German company producing quality manufactured sand and aggregate for the construction of urban autobahns in Germany,? George says.

?The use of a high quality modified polymer bitumen combined with the manufactured sand and aggregate reduces noise from the roads and improves drainage, which in turn reduces stopping distances in wet conditions.?

Unlike most natural sand, the VSI output does not need to be pre-washed or post-washed when processing clean material.
TCL?s Eduardo Lanna says the use of the new Sandvik CV117 VSI has improved the whole production process compared with his old compression crushers. Contamination rates resulting from the crushing process are now almost negligible.

He says his production rate has risen 15 per cent since he acquired the Sandvik equipment, a needed enhancement in view of his projections for the near future.

?We believe demand for manufactured sand will increase 30 per cent in the coming year,? he says. That prediction is in line with what George sees in Sandvik?s future.

 ?The best way to resemble natural sand is to make it in a VSI,? he says. Sandvik has sold more than 400 crushers, most of which are used to produce manufactured sand.

?The business of making manufactured sand will become very big, and we are already seeing a huge increase in demand. It took millions of years of erosion and weathering for Mother Nature to make natural sand. The Sandvik VSI creates that same beautiful shape in a matter of seconds.?

A further market opportunity is in processing compression-crushed quarry dust. George Fensome and Eduardo Lanna agree that quarry dust, currently considered a waste product, can be turned into a saleable manufactured sand product. From mining sites to tunnelling projects, if waste material is available there is more business to be done.

?This is another opportunity for increased sales,? George says. ?It also reduces waste, which is good for the environment, and saves the producer money by eliminating landfill or waste disposal costs.?

Eduardo Lanna recalls his experience with quarry dust. ?In 1997, there were about 600,000 tonnes of dust stocked in our quarries,? he says. ?There was no way of selling it, so I took the decision to wash and classify this material using dewatering screens. By the year 2000, all 600,000 tonnes had been processed and sold.?

There are three main types of manufactured sand, according to George Fensome:

1. Manufactured sand whose 75 micron content contains deleterious material such as clay, lignite and mica, some of which has to be removed.

2. Manufactured sand made from clean aggregate that makes it possible to use all the 75 micron content and avoid washing and classification systems. This sector is of particular advantage where water is available only at a premium cost or is not available at all.

3. Manufactured sand blended with existing quarry dust, a waste product resulting from compression crushing. It is possible to use up to 13 per cent quarry dust blended with VSI clean manufactured sand, or to process the quarry dust through the Sandvik CV-series VSI to improve the shape of the fine particles, increasing the percentage acceptable for premium sand/asphalt and concrete applications.
What used to be unsaleable products can now be turned into high quality manufactured sand and aggregate for use in the production of asphalt and concrete products. This is good news, especially for the many sand-deficient corners of the world.

This article first appeared in Solid Ground, No 1, 2010, Sandvik Mining and Construction?s business and technology magazine.

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