Einfluss der Betonuntergrundrauhigkeit auf das Haftvermögen zementgebundener Beschichtungen / Influence of the surface roughness of a concrete substrate on the adhesion of a cement-based coating

Concrete overlays are often used for the repair of damaged concrete surfaces. The material propreties of the concrete overlay are different from those of the substrate. Restraint of shrinkage and thermal strains result in tensile stresses. At the free boundaries of the system the tensile stresses reach a maximum value. If these values reach the adherence strength, strain softening and then delamination occur starting from the free boundaries. The adherence behaviour of such a repair layer depends on the surface roughness and could be characterized by the wedge splitting test by use of non-linear fracture mechanics. The surface roughness of the substrate could be determinated and correlated to the adherence behaviour of concrete repair layers.