Tragverhalten von Verbundankern in hoch- und ultrahochfestem Beton

Behavior of adhesive anchors in high strength and ultra high performance concrete

Recently about 170 pull-out tests and further experimental investigations with various chemical anchors installed in high strength and ultra high performance fiber reinforced concrete have been performed. Apart from the concrete base material, other parameters like drilling method, intensity of cleaning of the borehole and water saturation of the concrete have been varied. The results of the confined tests reveal that the bond strength of chemical anchor systems may decrease in high strength concrete. Based on the current state of the art in normal strength concrete, an extrapolation of the behavior to higher strength classes is hardly possible. Chemical anchors with low adhesive bonding might behave unsatisfactorily whereas high bond mortars usually will be suitable for application in high strength concretes. In addition unconfined pull-out tests with large support widths have been performed. As a rule in high strength concrete, depending on the product, chemical anchors may fail in the majority of cases due to rupture of the steel rod, pull-out or pull-out combined with concrete cone breakout in the upper anchorage zone.