World’s longest steel-slag road replaces quarried stone in India

A 1.85-kilometre, four-lane road in Raigarh, India, has earned a Guinness World Records title as the longest built exclusively with processed steel slag aggregates. The project used nearly 200,000 tonnes of the steelmaking byproduct, replacing natural stone across the pavement structure rather than only in a surface layer.

Developed by Jindal Steel and the CSIR-Central Road Research Institute, the road turns slag into engineered aggregate through ageing and stabilisation, metal recovery, crushing, screening and grading. The material underwent physical, mechanical, geotechnical and environmental tests before use. The finished corridor connects with National Highway 49 and is designed for heavy commercial traffic.

The project team estimates that the pavement is about 35% thinner than a conventional bituminous design, with construction costs up to 40% lower. The Raigarh build demonstrates the technology at substantial scale while reducing demand for newly quarried stone.

A technology transfer agreement has been signed to support wider adoption. CSIR-CRRI has also reported receiving a work order for a 40-kilometre road in Odisha, offering a much larger next test of the method.