Recycling Construction and Demolition Wastes as Building Materials: A Life Cycle Assessment
Résumé
The present study addresses the topic of recycling materials from construction and demolition (C&D) wastes by proposing an environmental comparison between two recycling schemes for gravel wastes. The first scheme is the baseline process, and leads to direct most of the gravel to road construction. The second scheme relies on an innovative technology for the processing of gravel, based on electrical fragmentation, which leads to a clear separation between the aggregate contained in the gravel and the cement paste. The purity of the obtained materials opens new recycling outlets—as part of high-quality structural concrete for the aggregate and as a substitute to natural minerals in clinker kilns for the cement paste. This shift towards more-specific outlets for the materials found in reclaimed gravel carries significant modifications in the overall handling of C&D wastes and in the supply of natural and non-natural materials for road construction and concrete formulation. The environmental implications of these modifications are evaluated according to a life cycle assessment methodology, which specifically addresses the influence of the distances and modalities of transportation of wastes to the crushing processes, as well as of natural and recycled aggregate to construction and demolition sites. The results point out significant environmental gains for the alternative recycling scheme, in all the considered impact categories and whatever the implemented scenarios. These gains are modulated by the various transport distances of the heavy materials heeded in the global system.