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2nd April 2022 (7 Topics)

Surat gets India’s first steel slag road: What is it, how is it different from regular ones?


Surat has become the first city in the country to get a processed steel slag (industrial waste) road.


  • The processed steel slag (industrial waste) road is built as part of a joint-venture project by the
    • Council of Scientific and Industrial Research (CSIR)
    • Central Road Research Institute (CRRI)
    • Union Ministry of Steel
    • government think-tank NITI Aayog
    • ArcelorMtttal-Nippon Steel (AM/NS)
  • The six-lane public road is a kilometre-long stretch in Hazira industries.
  • The construction cost of the processed steel slag road is 30 per cent cheaper than roads built from natural aggregates.
  • The thickness of the road is also 30 per cent lesser than normal ones, while the durability is much longer due to the utilisation of steel slag.
  • This project falls under the initiative of the Waste to Wealth and Clean India Campaign.

The process

  • The slag is generated from a steel furnace burning at around 1,500-1,600 degree centigrade in the form of molten flux material as an impurity.
  • The molten material is poured into the slag pits for cooling as per the customized procedure and further processed to develop stable steel slag aggregates, with “better material properties in place of the natural aggregate commonly used in road constructions”

The load-test

  • Over 30 heavy-loaded trucks use the carriageway on a daily basis.
  • The steel slag road has been constructed using instrumented test sections, comprising strain gauges, pressure cells, displacement gauges and thermocouples to measure load-induced deformation, and stress and strain in the pavement areas. 

Are these roads cost-effective and good for the environment?

  • Utilisation of processed steel slag in road construction paves the way for sustainable use of waste and reduces the reliance on perishable natural aggregates.
  • This process is also expected to reduce GHG emissions and carbon footprint in road construction activity and is in line with India’s commitment to the United Nations Sustainable Development Goal No. 9 for building resilient infrastructure through inclusive and sustainable industrialization and green technologies.
  • The approximate construction cost per square meter of a processed steel slag road is Rs 1,150 as against Rs 1,300 for a bitumen road and Rs 2,700 for cement or a concrete one.
  • The lifespan of a cement or concrete road is over 30 years while that of bitumen and steel slag road is around 15 years.

Do high temperatures affect these roads?

  • The upper surface of the road will be around “1-2 degree higher in mid-afternoon when compared to regular ones”.
    • Thermocouple has been used to maintain the temperature of the outer surface of the road.
  • However, the carbon footprint for such roads is much lower as the ones built using natural aggregates are mined and processed.
  • Besides, after mining and crushing, the material also needs to be transported from one place to another.
    • When it comes to steel slag road, there is no blasting, drilling or crushing as the material is waste coming out of a steel industry which is processed and converted to the form of aggregate material used for construction.
    • The utilisation of waste steel slag for road constructions reduces pollution created by heaps of waste dumped nearby.
    • The particles of steel waste also get into the air and even seep into the ground, reaching the underground water table.
  • The steel slag melts at over 200 degree Celsius, while the temperature during peak summer in India is not above 45 degree Celsius.
    • Moreover, the upper layer is made up of bitumen layers.

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