RANCHI: In a significant breakthrough, the Central Institute of Mining and Fuel Research (CIMFR), Dhanbad, has discovered that hard rock overburden—a waste material generated during coal mining—can be used as a substitute for natural stone aggregates in concrete production.
The study revealed that concrete made with the processed mining waste matches conventional concrete in terms of strength and durability, while being considerably more economical.
The innovation also holds substantial environmental benefits by reducing mining waste and lowering dependence on natural stone resources.
According to Dr. Mustaq Ansari, who has been working on the project for the past four years, the hard rock overburden was processed and incorporated into concrete as a replacement for natural aggregates.
Extensive testing confirmed that the resulting concrete performs on par with conventional concrete, he said.
Ansari added that the technology is currently undergoing the patenting process, and commercial-scale production is expected to begin once the patent is granted.
As part of the study, hard rock recovered from coal mine overburden dumps was processed and crushed for use as coarse aggregate in concrete production.
“The research evaluated the replacement of natural aggregates with overburden aggregates in varying proportions, ranging from 25 per cent to 100 per cent, followed by comprehensive laboratory testing. The findings revealed that concrete produced with overburden aggregates exhibited compressive strength, tensile strength, bond strength, and durability comparable to conventional concrete,” said Ansari.
This indicates that it can be safely used in the construction of roads, bridges, buildings, and other critical infrastructure projects without compromising structural performance, he added.
Furthermore, Ansari informed that the concrete demonstrated satisfactory workability, further supporting its suitability for large-scale applications. In addition to that, if coal mine overburden is used instead of natural stone, every ton of overburden aggregate can prevent the mining of a tonnes of natural stone.
“This would lead to the conservation of mountains, reduced deforestation, and decreased pressure on rivers and biodiversity, while also transforming mining waste into a valuable resource,” said Ansari.
Basically, material previously dismissed as mere waste can now serve as a robust foundation for future construction, he added. A detailed cost analysis, taking into account transportation, crushing, labour and electricity expenses, found that the production of coarse aggregate from coal mine overburden is nearly 65 per cent less expensive than that of natural aggregates.
The study also showed that using overburden-based aggregates in the production of one cubic metre of M30-grade concrete can reduce costs by about 18 per cent.
The economic benefits become even more significant when applied to large-scale infrastructure projects such as roads, bridges, railways, and government construction works, where the cumulative savings could run into several crores of rupees.