The Public Works Department (PWD) has permitted the use of slag, a by-product of iron ore smelting by steel plants, in construction of roads. Slag will be first used in Bellary district where mega steel plants are located.
Faced with acute shortage of natural sand, the PWD has been looking for alternatives; one of them being blast furnace slag, a non-metallic material produced when ore is melted.
An expensive by-product resembling natural sand, slag is not commonly used in construction in India, unlike in many advanced countries.
Steel plants in Karnataka produce the material in bulk and are ready to offer it free of cost. Jindal Steel Limited of Torangal in Bellary district is one of them.
The PWD expects contractors to lift slag for road works. But it has not yet given permission for use of slag in construction of buildings.
Official sources said that slag deposits had taken up too much space at steel plants and the companies were looking for an easy way of clearing it.
O K Swamy, chief engineer (North), PWD, said that slag had “piled up like mountains” in the junkyards of certain mining firms. They have, for the first time, come forward to give it free of cost to the government. It is the contractors’ responsibility to lift the stock.
“We have told the engineers and contractors to use it for laying base layers for roads. First, it would be used in Bellary. Transporting it to other parts of the State would be a costlier proposition. Districts like Bellary and Raichur have black soil which is not good for construction. So we can use slag in its place,” he explained.
But permission has not yet been given for using slag, which appears like river sand, in construction of bridges, culverts or other structures built by the PWD, Swamy added.
The PWD has taken experts’ opinion before permitting the use of slag in road work.
Dr V S Viswanatha, Chairman, Civil-Aid Technoclinic Pvt Ltd, in his study report, recommended that the blast furnace slag from JSW Steel could be used instead of natural sand as it satisfied all the conditions prescribed by the Indian standard.
The report said that the feasibility of using slag in asphalt concrete works was being studied. It can be used in combination with manufactured sand or natural river sand in the ratio of 50:50 for rigid pavement works.
But it is not recommended as a 100 per cent replacement for natural sand in rigid pavement works. According to Swamy, another expert report, by the Indian Institute of Science (IISc) on the use of slag, is expected.
Vaman Acharya, Chairman, Karnataka State Pollution Control Board, said the board had strongly recommended that alternatives to natural sand be scouted. According to him, manufactured sand and slag sand are the two substitutes for river sand.
Even debris could be converted into sand. All efforts should be made to use eco sand, considering the acute shortage of natural sand for civil works. Use of slag is approved globally.
Acharya also said that not just JSW, many other steel manufacturing companies in the State were willing to offer slag for use in construction.