KOCHI:
CUSAT research team’s findings on recycling and reusing the concrete wastes generated from demolition of huge buildings gets attention in the context of demolition of Maradu flats.
CUSAT conducted a three-year long (2013-16) KSCSTE-sponsored research project to ascertain the technical feasibility of coarse RCA (obtained by crushing of concrete waste) as a substitute for fresh natural coarse aggregate (obtained from crushed stone), undertaken successfully by a team consisting of Dr Dipak Kumar Sahoo as the Principal Investigator, Dr Glory Joseph as Co-Principal Investigator and two research scholars, Praveen Mathew and Biju Varghese at School of Engineering, CUSAT.
The study was focused on the complete utilization of crushed concrete waste as a substitute for natural (crushed stone) coarse aggregate (NCA) for use in fresh structural concrete as well as masonry blocks. The research study showed that old concrete can be recycled in-situ, in a crusher plant and used as coarse aggregate in fresh structural concrete and as aggregates for manufacturing masonry blocks of acceptable quality. The concrete waste was sourced from an old framed building which was demolished to facilitate Kochi Metro Rail Project and crushed by a mini jaw crusher in the lab.
The team recommends regarding the reuse of concrete waste generated from the demolition of Maradu flats that it has to be segregated from other demolition wastes and crushed in-situ, in a nearby crusher to the required size range. The fraction between 0.15 and 4.75 mm can be used as quarry sand for producing fresh concrete or cement mortar for masonry and plastering works. No codal restriction is there on its use if it fulfills the particle size distribution specified for sand in IS 10262.
The small quantity of superfine fraction below 0.15 mm obtained from crushing can be used in cement mortar in allowed proportion to get smooth finish in plastering or in pavement or non-structural concrete for finishing works. The fraction between 4.75 and 10 mm can be used as coarse aggregate for manufacturing masonry blocks.
The fractions, 4.75- 10 mm and 4.75-20 mm, are suitable for producing conventional and self-compacting concrete (SCC), respectively, subject to approval by clients because their use as coarse aggregate for structural concrete is not yet permitted in Indian codes. Many countries including Japan have brought out national codes permitting the use of coarse RCA for structural concrete applications.
“Alternatively, the entire concrete waste can be crushed to below 4.75 mm size for use as fine aggregate (sand) or crushed to 4.75-10 mm size for use as coarse aggregate for manufacturing masonry blocks, because to our knowledge there is no codal bar on such uses”, says Dr Dipak Kumar Sahoo.
