Adhesive Power of Ultra High Performance Concrete from a Thermodynamic Point of View

Ultra high performance concrete (UHPC) is well suited to provide adhesive connections with other materials. Here, not only does mechanical interlocking provide adhesion, but also intermolecular forces that are closely related to the surface energy of the used materials. The determination of intermolecular forces for UHPC connected to glass and steel is presented in this work. First, the theoretical relation between intermolecular forces and the surface energy is shown. The main part deals with experiments on the determination of the surface energies. Contact angle measurements are used to determine surface energies of steel, glass, and hardened UHPC. Some ideas on estimation of the surface energy of fresh UHPC using conventional testing methods are presented. Finally, the calculated specific adhesion is compared to the technical adhesion determined by direct tension tests.