Steel Slag Road Technology:
Transforming Waste to Wealth
Under the banner of "waste to wealth," a cornerstone of the Swachh Bharat Abhiyan, India's drive toward a cleaner and more sustainable future has led to innovative solutions for managing industrial by- products. One such initiative is spearheaded by the Central Road Research Institute (CRRI), a constituent laboratory of the Council of Scientific and Industrial Research (CSIR). Funded by the Ministry of Steel, Government of India and in collaboration with four major steel industries, this research and development effort focuses on transforming steel slag- a waste product from the steel manufacturing process- into a valuable resource for road construction. Steel slag, formed during the separation of molten steel from impurities in steelmaking furnaces, transitions from a liquid melt to a solid state upon cooling, presenting a unique opportunity for large- scale reuse in infrastructure development.
After partial metal recovery, steel slag is commonly disposed of as landfill near steel plants, consuming large areas of land and contributing to air, water and soil pollution. As the second- largest steel producer globally, India generates about 19 million tonnes of steel slag annually, a figure that could rise to 60 million tonnes per year by 2030. This growing volume of solid waste highlights the importance of finding sustainable uses for steel slag, such as in road construction, which aligns with the expanding waste- to- wealth movement.
Steel slag has a tendency to corrode and leach heavy metals, which complicates its use in infrastructure. To overcome these hurdles, CSIR- CRRI has developed a technology to process different types of steel slag into usable aggregates, enabling its effective application in road construction. This innovative solution addresses both environmental concerns and resource optimisation.
Pioneering Steel Slag Roads in India
NH- 6 to Hazira: Surat in Gujarat has achieved a significant milestone by unveiling the country's first one- kilometre long, six- lane bituminous steel slag road. This unique road links National Highway (NH)-6 to Hazira port and was officially inaugurated on June 15, 2022. The collaborative effort behind this pioneering project involved CSIR- CRRI, the Union Ministry of Steel, NITI Aayog and a leading domestic steel company. Remarkably, the road incorporates steel slag in all layers, completely replacing natural aggregates. A substantial
1 lakh tonne of processed steel slag aggregates developed at Hazira based steel plant was utilised during the construction of this road. This steel slag road, despite being 30- 32 percent thinner than the conventional bituminous roads for identical traffic condition, boasts exceptional durability, owing to the dense and resilient nature of steel slag material. It can withstand significant wear and tear, as well as heavier loads compared to traditional bituminous roads. This road, for its technological prowess, received national and international recognitions and has been inducted in "India Book of Records" and "Asia Book of Records" as 'First Steel Slag Road'.
Ziro Valley: In another project, the Border Roads Organisation (BRO) utilised solid waste from steel plants to construct a robust, enduring road along the India- China border in Ziro valley at Arunachal Pradesh. This one- kilometre long steel slag road, engineered by BRO with technological guidance and support from CSIR- CRRI, is designed to withstand heavy- duty usage. Approximately 1200 metric tons of processed steel slag aggregates were transported via railway and road, initially from Jamshedpur to Itanagar and then onward to the project site.
Mumbai- Goa Highway: The third steel slag road project encompassed the construction of a four- lane steel slag road section on NH- 66, the Mumbai to Goa Highway. Through this endeavour, approximately 80,000 tons of raw steel slag aggregates were transformed into processed steel slag aggregates at Dolvi based steel plant and utilised for construction of cement concrete and bituminous steel slag road section on R.H.S and L.H.S carriage ways. Following successful testing by India's largest road building agency, the National Highways Authority of India, the road was officially inaugurated in January 2024. It has since been designated as the first steel slag road section on a National Highway.
Benefits of Steel Slag Road to Common Man
• Improved Road Quality: Steel slag roads offer smoother and safer surfaces, enhancing the overall driving experience.
• Reduced Traffic Congestion: Fewer disruptions and closures for repairs minimise delays, saving time and reducing frustration for road users.
• Enhanced Safety: With fewer potholes, cracks and deformities, steel slag roads reduce the risk of accidents and road injuries.
• Environmental Sustainability: Lower carbon emissions during production contribute to a more sustainable and eco- friendly environment around the roads.
• Economic Savings: Steel slag roads are more cost- effective than conventional roads, leading to savings for both the government and taxpayers.
• Lower Maintenance Costs: Reduced need for repairs and maintenance results in long- term infrastructure savings, easing financial burdens on individuals and households.
• Job Creation: The construction and engineering of steel slag roads have the potential to generate employment opportunities, fostering local economic growth and livelihoods.
The Ecological Impact
The construction of roads typically requires vast quantities of natural aggregates, often sourced through unsustainable quarrying practices, resulting in desertification and significant ecological harm. However, the innovative approach of utilising steel slag in bituminous and cement concrete road construction not only mitigates the environmental impact of this waste material but also helps preserve our ecosystems by fulfilling some of the natural aggregate demand. Such initiatives play a vital role in fostering a circular economy within the country. In a circular economy framework, waste is repurposed as a resource for manufacturing new materials and products. This approach minimises the consumption of new resources, encourages the reuse and remodelling of materials and products, thus making them less resource- intensive. Essentially, it involves maximising the recycling of existing materials and products to their highest potential.
When compared to conventional roads, the steel slag road is not anticipated to exhibit significantly higher surface temperatures during peak summer seasons. Temperature measurements have revealed that the melting point of the steel slag road exceeds 1200 degrees Celsius, while its surface temperature during peak summers typically remains within the range of 45-50 degrees Celsius. While the conventional bituminous roads require strengthening in every 4 to 5 years, the bituminous steel slag road is not expected to require any strengthening for 12 to 15 years. However, the steel slag road showcases superior mechanical properties compared to conventional roads, retaining its strength in varying weather conditions such as sunlight, rain and floods. The Central Road Research Institute (CRRI), in collaboration with other steel companies and government organisations in India, has elevated the "waste- to- wealth" concept to new heights. In its forthcoming projects, CRRI aims to explore the utilisation of steel slag in Indian railways by substituting the railway ballast.
Interview
Prof. Manoranjan Parida
Director, CSIR- CRRI, New Delhi
Q. How is this technology influencing the global landscape and what are CSIR- CRRI's future plans for expanding its international outreach?
A. The sustainable and safe disposal of steel slag is a global challenge. Shri Satish Pandey, Principal Scientist at CSIR- CRRI and the inventor of the steel slag road technology, was honoured with the prestigious "Global Slag Personality of the Year Award" in June 2023 in Düsseldorf, Germany, by Global Slag for his work in developing this technology. He is the first Indian scientist to receive this award since its inception in 2007. Several developed and leading countries, including the USA, Russia, Australia, the UK and Iran, have expressed interest in CSIR- CRRI's steel slag road technology and are collaborating with the institute to implement it in their own regions.
Q. How many steel slag roads have been constructed in India by CSIR- CRRI so far and what measures are being taken to ensure the long- term success of this initiative?
A. CSIR- CRRI's steel slag road technology has been successfully applied in the construction of steel slag road sections in Gujarat, Jharkhand, Maharashtra, West Bengal and Arunachal Pradesh. Plans are underway to start similar projects in Andhra Pradesh, Odisha and Chhattisgarh. To ensure the long- term success of this initiative, CSIR- CRRI, in collaboration with the Ministry of Steel, has developed comprehensive guidelines titled "Guidelines for Processing and Utilisation of Steel Slag as Processed Steel Slag Aggregates in Road Construction." These guidelines will support various road construction agencies in effectively implementing the technology on a broader scale.
Q. Does this steel slag management initiative align with the goals of the Aatmanirbhar Bharat mission and is it fully indigenous?
A. India is undertaking an extensive road development programme and the availability of high- quality natural aggregates at an affordable cost remains a significant challenge for road construction agencies. The use of processed steel slag aggregates offers a fully indigenous and eco- friendly solution, turning waste into wealth while supporting the Aatmanirbhar Bharat mission. This initiative also aligns with the Government of India's Viksit Bharat vision for 2047. The Prime Minister, also the President of CSIR, Shri Narendra Modi has praised CSIR's steel slag road technology as a key contributor to green infrastructure development in the country.
Contributed by: Science Media Communication Cell, CSIR- NIScPR, New Delhi.