Development of an Innovative Technique for Demolition Concrete Up-cycling: a Response to Mitigate GHG’s Emissions and Natural Resources Depletion

Concrete is the second most used material worldwide and the first used man-made material. Its production entails large emissions of GHG due to lime decarbonation during the clinkering process, as well as large consumption of non-renewable minerals and natural aggregates. Currently legislative pressure aiming at preserving natural resources is growing tighter on natural aggregates extraction, which motivates research for alternative raw materials in building concrete manufacturing. Among these materials, aggregates from waste concrete are the most promising as they already fulfill some of the physical and mechanical requirements for the use in concrete. One key point that has to be considered is the cement paste content at the aggregate surface, since it adversely affects the adhesion between the aggregates and their surrounding cement matrix in concrete, thereby resulting in concrete with low mechanical properties (). Current practices in concrete recycling consist in largely non-selective crushing and screening processes, which do not allow a straight separation between the clean aggregates and the cement paste. The present study describes a high-voltage pulsed-power process of concrete fragmentation which enables to recover clean aggregates and hydrated cement paste (HCP). This HCP conveys valuable elements – Ca, Si, Fe, Al – that would potentiallyreduce energy and natural resources consumption as well as CO 2 emissions of the clinker making process, if it were introduced in the raw mix of the clinker kiln. Overall environmental benefits of this up-cycling chain depend on the mineralogical composition of the cement paste, which in turn depends on the operational conditions of the concrete fragmentation process. To date, only scarce data are available to assess this recycling scheme. In this framework, our study tackle the subject by putting forward an experimental investigation of the pulsed-power process, coupled with a calculation methodology to assess the environmental benefits associated with the recycling of the obtained hydrated cement paste in clinker manufacturing. The proposed methodology leads the way to a comprehensive environmental assessment of concrete recycling schemes, based on a forthcoming LCA study that will make use of the results presented.