Fachhochschule Lübeck, University of Applied Sciences, Germany


Supplementary injection anchors are used as a repairing-system inside historic masonry for transferring tensile-forces that cannot be transmitted by the masonry itself or for new connections. They consist of a tensile element – usually steel – inserted into the slightly larger borehole and the annulus is grouted with cement. The solid plug of injection material transfers the tensile forces to the masonry. Assuming successful grouting, considerable tensile forces can be transferred at short bond lengths in accordance with design recommendations developed by the author. Supplementary injection anchors have been utilised since the 1920s and are applied within the core philosophy of minimum intervention.
The paper summarizes a recent laboratory test series with 75 anchors focussing on the comparison of bond in masonry structures and bond in concrete. The results are discussed in comparison with the design recommendations for injection anchors in masonry and concrete bond principles.

Key words
Repair; Reinforcement; Injection Anchor; Bond Strength; Minimum Intervention