Experimentelle Untersuchungen zum Auszugsverhalten von Stahlfasern in höherfesten Betonen

Experimental investigation of the pullout behavior of steel fibers in high-strength concrete

Steel-fiber-reinforced concretes are used more and more also in structural concrete elements. Examples for these are among others tunnel lining segments. In this case there is a specific characteristic, that concretes for such elements usually have a compressive strength between 70 and 90 N/mm². These concretes are very brittle with only low fracture toughness, so that damages in form of cracking and spalling often occur in the periphery of the segments. By the addition of steel fibers the ductility of the concrete can be considerably improved. The primary question is, to which extend the stresses can be transferred in concrete cracks by the fibers bridging these cracks.
To investigate the bonding behavior between steel fiber and concrete matrix, single fiber pullout tests were performed in high-strength concrete matrix. Various parameters such as fiber shape, geometry, tensile strength, surface properties, inclination angle and embedment length were investigated. Based on the experimental results, the effect of those parameters on pullout force versus slip relationship, pullout work, fiber utilization and fiber/matrix failure mode were analyzed and discussed.