KOCHI: The fate of the giant heaps of concrete debris once the four apartment buildings in Maradu are demolished has been a topic of discussion. The demolition will generate around 7,000 tonnes of debris, of which 1,000 tonnes may be concrete waste from the frame of the structures. So what to do with the waste?
A team of researchers from Cochin University of Science and Technology (Cusat) have come up with an answer — convert it into fresh concrete or make masonry blocks. “Good quality concrete waste can be recycled and reused as aggregates for fresh concrete or for manufacturing masonry blocks,” said Dipak Kumar Sahoo, professor, School of Engineering, Cusat.
He said the most economically gainful and ecologically sustainable use of concrete waste lies in its complete reuse as recycled concrete aggregates (RCA) for structural concrete applications. “When waste concrete is crushed, three structurally distinct fractions of crushed materials are obtained,” he said.
The components are superfine fraction below 0.15mm, which can be used in fresh concrete or with quarry sand to get better finish in plastering or pavements.
The major product obtained from crushing concrete waste, coarse RCA between the size range of 4.75mm to 20mm, holds promise as a substitute for fresh natural coarse aggregate (NCA) for structural concrete applications. The only impediment is the Bureau of Indian Standards is yet to explicitly specify its structural suitability in Indian Concrete Code IS 456.
To ascertain the technical feasibility of coarse RCA as a substitute for fresh NCA, a three-year (2013-16) research was undertaken by a team comprising Dipak Kumar Sahoo as principal investigator, Glory Joseph as co-principal investigator and research scholars, Praveen Mathew and Biju Varghese, at School of Engineering.
“Our source for concrete waste was an old-framed building demolished for the Kochi Metro and crushed by a mini jaw crusher in the lab,” said Sahoo. The research showed old concrete can be recycled in-situ or in a crusher plant and used as a coarse aggregate in fresh structural concrete and as aggregates for manufacturing masonry blocks of acceptable quality.