Untersuchungen zur Rauigkeit und Tragfähigkeit von Verbundfugen zwischen normalfestem Beton und UHFB

Investigations into roughness and load-bearing capacity of interfaces between normal-strength concrete and UHPC. Reinforced concrete and prestressed concrete bridges built in Germany before 1980 often have low ratios of shear stirrup reinforcement and deficits in the calculated shear capacity. A cross-sectional strengthening of the bridge deck slab with fiber-reinforced ultra-high performance concrete (UHPC) is a simple, fast and economical strengthening option, especially if it is designed as an unreinforced joint. The prerequisite for quasi-monolithic component behavior is a largely rigid bond-slip behavior between the normal strength concrete (NSC) of the bridge deck slab and the UHPC topping concrete, which requires sufficient roughness of the UHPC-NSC joint. For this purpose, a method for the non-contact local and large-area determination of roughness parameters was developed on the basis of high-resolution measurement data from a 3D stripe light scanner, the roughness of joint surfaces of small-scale UHPC-NSC shear test specimens and of an NSC beam with UHPC concrete topping was determined and the effectiveness of the strengthening measure with sufficient joint roughness was verified using small-scale UHPC-NSC shear tests as well as bending and shear force tests on an NSC beam with and without UHPC concrete topping. In the beam tests, the UHPC strengthening caused a change in the decisive failure case from shear force to bending, which predestines this strengthening measure for the compensation of shear force deficits.