Circular construction system with reused RC components – compressive load-bearing capacity of subtractively processed dry joints

The reuse of reinforced concrete components from demolished buildings offers substantial potential to reduce construction waste, conserve primary resources, and lower CO 2 emissions. Integrating component reuse within circular construction and digital fabrication concepts further enhances this potential and enables particularly rapid construction progress when using dry joints. A key challenge is to ensure a reliably strong connection between the reused elements, which requires accurate characterisation of the properties of the joint surfaces. In this study, two-part concrete cylinders with cut, milled, and ground joint surfaces were tested under axial compression. High-resolution 3D scans enabled a digital evaluation of surface roughness and fit accuracy of the dry joints, providing quantitative data for correlating joint quality with load-bearing performance. Results show that improved surface quality markedly increases compressive strength. Ground joints achieved the full load-bearing capacity of the monolithic reference specimens, while cut and milled joints reached approximately 85 % and 80 % respectively. All joints significantly exceeded the conservative compressive strength limits specified in the European concrete standards and show high potential for improving design approaches. These findings demonstrate the potential of digitally characterized, force-fit concrete dry joints as a foundation for future automated fabrication and assembly of reused reinforced concrete components within circular construction systems. • Product recycling of entire components reduces CO 2 emissions in new construction. • Robotic joint processing in a fully digital and automated production environment. • High-resolution 3D scanning of joint roughness and joint fit accuracy. • Codes and standards underestimate the compressive capacity of machined joints.