Recycling of concrete construction and demolition waste in alternative binders: Part 1 – Technical study

Abstract

The concrete construction and demolition waste (CDW) is usually recycled as coarse aggregate. The fine fraction remains unused – if recovered at all, it is for downcycling in backfilling. Part 1 of this article is dedicated to a technical study on recycling of the waste concrete powder (WCP) as supplement in blended cements. Part 2 presents assessment of the environmental impacts of those binders. XRD and DTA/TG analyses of WCP are performed. WCP from two types of concrete CDW is used. The behaviour of fresh and hardened pastes with replacement of CEM I 52,5 by WCP (15%, 30% and 45%) is investigated. Standard methods of testing with some modifications are used. The influence of WCP content on the setting, consistency, strength and water absorption is evaluated. Four different curing regimes are applied. The results confirm the initial assumption that WCP can be consider as cementitious supplement. The replacement rate up to 15% practically does not change the behaviour of the binder, while 45% seems to be the maximum, because of binders performances degradation. The replacement up to 30% allows to keep satisfactory technical properties, but offers greater economic and environmental advantages.