Multi-recycled aggregate concrete towards a sustainable solution – a review

Abstract

Reduce, reuse and recycle are the important facets of susta-inable construction and environmental recovery. Increase in the construction activity generates huge amount of construction and demolition waste worldwide, and has a potential to be used as concrete coarse aggregate. In the future, where, most of the cities are likely to become concrete jungles, recycling and multi-recycling of concrete becomes all the more important. Also, the precast industry generates large amount of wastes due to discrepancies in quality of materials. Instead of depositing them as landfi lls or rejecting recycled materials, the possibility of reusing them is investigated and the fi nite number of times the recycling can be done, is examined. The present paper ponders on literature works, done by various researchers to check the variation in properties of recycled concrete aggregate, after fi nite number of generations of recycling. The studies on fresh and hardened state properties of recycled aggregate concrete showed a decrease in quality, with respect to mechanical performance of newly made concrete. The recycled concrete aggregate from precast rejects performed equal to natural concrete and even showed slightly higher compressive strength than natural aggregate concrete and can be replaced up to 20% of natural aggregate, to produce the concrete of accepted quality. The third generation recycled concrete aggregate showed almost twice the amount of mortar as that of fi rst generation re-cycled concrete aggregate. It can be seen that the concrete can be recycled only a fi nite number of times. A relationship between strength and durability properties of recycled aggregate concrete of different generations was derived based on multi-linear regres-sion analysis.