In March 2022, Surat became India’s first city to get a processed steel slag (industrial waste) road, an innovation of the Central Road Research Institute (CRRI), NITI Aayog, and the Council of Scientific and Industrial Research (CSIR), and ArcelorMittal Nippon Steel Ltd. (AM/NS), at Hazira. This site for road construction was chosen because of the proximity to the AM/NS steel plant, which produces around two million tonnes of steel slag annually, and the availability of heavy traffic on the road for study purposes. Experts are of the opinion that these roads are much more durable during the monsoon. Around 1 lakh tonne of processed steel slag was used in the making of the road.
Around nineteen million tonnes of steel waste is produced by steel plants throughout the country annually, and this waste could grow, as an estimate, to 50 million tonnes by 2030.
Benefits of Steel Slag Road
- The utilisation of processed steel slag in road construction paves the way for sustainable use of waste.
- This road reduces the reliance on perishable natural aggregates.
- This process will also expectedly reduce greenhouse gas (GHG) emissions and carbon footprint in road construction activities. So, it is in line with India’s commitment to the UN Sustainable Development Goal 9 for building resilient infrastructure through inclusive and sustainable industrialisation and green technologies.
- For obtaining steel slag, there is no blasting, drilling or crushing whereas natural aggregates are mined and processed. Steel slag is a waste, coming out of a steel industry which is processed and converted to the form of aggregate material to be used for construction. As such, carbon footprint is much lower
- The process is also cost-effective. As per the Executive Engineer at SMC’s Road Development Department, B.R. Bhatt, the approximate construction cost per square metre of a processed steel slag road is Rs 1,150 as against Rs 1,300 for a bitumen road and Rs 2,700 for a cemented or a concrete one. Thus, the construction cost of such steel slag roads comes down by 30 per cent.
- The lifespan of a bitumen and steel slag road is the same, around 15 years.
- As per experts, the upper surface of the road will be around 1–2 degrees higher in mid-afternoon when compared to regular ones. So, thermocouple (a temperature measuring device) has been used to maintain the temperature of the outer surface of the road.
- The utilisation of waste steel slag for road construction reduces pollution created by heaps of waste, dumped nearby. The particles of steel waste get into the air and even seep into the ground, reaching the underground water table.
- The impact of such roads on tyres would be negligible because the steel slag melts at over 200 degrees Celsius, while the temperature during peak summer in India is not above 45 degrees Celsius. Moreover, the upper layer of the road is made up of bitumen.
About the Project
In the Hazira industries, steel slag road is a six-lane, 1.2 km long experimental public road, which was built by substituting natural aggregates with 100 per cent processed steel slag. It is now open for traffic. Construction of the road began around a year ago by converting mounds of steel waste into steel slag aggregate. The sixth and final lane of the road, consisting of a three-lane to-and-fro carriageway on either side, was completed in early March. Now, the road is being used by over 30 heavy-duty vehicles of multinational companies located in the outskirts of Surat.
This road, which is also part of a research study, 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. The temperature variation in the pavement layer is also being monitored using thermocouples, and the CSIR CRRI will further monitor its performance for another one year.
This project falls under the initiative of the Waste to Wealth Mission and the Swachh Bharat Abhiyan (Clean India Campaign).
Steel Slag and Its Utilisation
The slag is generated from a steel furnace burning at around 1,500–1,600 degrees centigrade in the form of molten flux material as an impurity, which is poured into the slag pits for cooling as per the customised procedure. This slag is further processed to develop stable steel slag aggregates, with better material properties as compared to the natural aggregate, generally used in the construction of roads.
The Indian Road Congress guidelines state that around 600 to 700 mm thickness of road layers are required on the foundation with 8 per cent CBR (California Bearing Ratio) for the construction of a heavy-traffic road, capable of taking the load of 1,000–1,200 trucks per day. However, roads made out of steel slag are 30 per cent less thick compared to normal highways, because of better material characteristics.
The CRRI will now prepare guidelines and specifications for the utilisation of steel slag in road construction. The parameters and performance indicators will be incorporated in the road guidelines and will be given to Indian Road Congress, the Ministry of Roads and Highways, so that steel slag may be utilised for the construction of national highways.
© Spectrum Books Pvt Ltd.