Lack of natural sand spurs artificial production

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Reshma Ravishanker, Bangalore, Sept 15, 2013: Spurred by the acute shortage of natural river sand in the State, engineers are now making artificial sand by using steel slag (a by-product of the metal melting process) and crushing rocks. The sand thus made is of the same quality as the natural one, they claim.

The skyrocketing prices of sand have forced the construction industry to find alternative ways to meet the growing demand. The Kollegal sand from the Cauvery river bed and considered of superior quality is not in supply. Hence, the City is getting sand from such places as Challakere, Pavagada and Chitradurga. A truckload of sand (about 900 cubic feet) from these places costs between Rs 35,000 and Rs 40,000.

The construction industry is considering its options. At a workshop-cum-exhibition organised by the Karnataka Engineers’ Federation to commemorate Sir M Visvesvaraya’s 153th birth anniversary on Saturday, sand was the chief topic for discussion.

Later speaking to Deccan Herald, Jayashankar Balan, Commercial Manager at JSW Steel, said, “We think the slag left after manufacturing steel is the best alternative to sand. We can easily produce artificial sand from it.” Artifical sand can be used in building roads, concrete, plaster, mortars and RMC plants, he added.

Balan hoped that by 2020, 70 million tonnes of slag could be stacked. “Instead of treating it as a waste material, we can put it to good use,” he said.

The slag was earlier used for making cement. Growing demand for sand, however, has forced the industry to use it to make that material. Making cement would yield the industry more profits but the switchover was necessary keeping in mind the future, Balan explained.

Approximately 500 tonnes of slag is produced from the manufacture of every 1,000 tonnes of steel. The sand made from such slag “meets all international standards” and costs about Rs 100 per tonne on site (in Bellary and Hospet), considerably less than the river sand. The charges to transport the sand to Bangalore will, however, gobble up all the savings.  This artificially manufactured sand is already being used in states like Goa. The Karnataka State Pollution Control Board (KSPCB) has also okayed the use of such sand, Balan said. According to sources, the National Highways Authority of India has also agreed to experiment with the artificial sand.

Vijay Kumar, a City-based architect, said that India could learn from Europe where natural sand is not at all available. “Artificially manufactured sand is used there in all types of constructions. The quality won’t go down here either,” Kumar asserted.

Rock-to-rock collision
Puzzolana, a Hyderabad-based manufacture of industrial equipment, has adopted the process of breaking complex rocks to meet the sand needs. Similar to the natural way of sand formation, the process involves the rock-to-rock collision principle.

The vertical shaft Impactor (VSI) is used to apply similar principle of ‘Rock on Rock collision’ for crushing. The process is disadvantageous as micro-fine particles (particles of a smaller size) are generated, needing further classification.

Either by a wet or dry process, the fine dust is separated from the sand. In the wet process, a current of water is used to separate the micro particles whereas in the dry process, an auxillary fan that works on the gravity principle is used, according to the company.

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