Upcycling concrete rubble into masonry walls: Design and assessment of two prototypes built with digitally augmented tools

Concrete rubble is currently a downcycled material whose upcycling remains under-explored and complex. This paper presents an accessible upcycling strategy to design and build slender structural masonry walls made from off-the-pile large demolition concrete rubble using digitally augmented construction tools. Two full-scale prototypes are designed and built using such strategy, and assessed for their structural and environmental performance. Accessible digital tools for acquisition, design, and fabrication are implemented to handle irregular geometries of heavy concrete rubble while considering availability of construction tools and skills. The accessibility of such strategy relies on picture-based scanning, 2D stacking and orientation through gravity during lifting. Optimisation is addressed by measuring processing time of connections, volume of added material, providing data for the analysis of the walls. The environmental analysis is supplemented by measurements of the electric consumption of all tools, and is conducted through a comparative life cycle analysis. The structural analysis is achieved from material test, strut and tie models and load testing. The research presented in the paper validates the feasibility of constructing single-leaf masonry walls from large concrete rubble pieces using digital augmentation of existing tools. The constructive and structural refinements through prototyping allow the second wall to withstand compression stress of at least 3 stories above ground floor, to present parallel vertical flat faces, be airtight, as well as have regular thermal and acoustic properties of concrete. Compared to irregular stone alternatives, the wall saves 58% of embodied carbon and diverges concrete waste from downcycling.