Concrete demolition waste: sustainable source for structural concrete

An increasing trend towards the use of sustainable processes has led to recycle materials of different nature into concrete. Recycling contributes to waste valorisation and environmental impact reduction, thus avoiding waste landfill disposal and preserving natural raw materials. Construction and demolition waste (C&DW) constitutes a major portion of solid waste production in the world. Research on the possibility of treating and reusing such waste as aggregate in new concrete has largely increased in the last years. Although it is generally recognised that crushed recycled aggregates derived from C&DW produce concrete with a low compressive strength when used as natural aggregate replacement, many features still need to be studied to properly assess the use of C&DW for building construction purposes, in particular for structural concrete. This paper investigates a suitable treatment of C&DW prior to batching and the set up of structural concrete mix design with the aim to optimize physical and mechanical properties of the new concrete. Fresh- and hardened-state properties of the studied formulations are compared with that of traditional concrete with natural aggregates. Moreover, the effects of C&DW on concrete time-dependent properties such as shrinkage and viscoelasticity, etc. are also investigated.