The excellent advantages of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) are durability, strength and ductility. Thus, various possibilities for new developments in structural concrete arise. On the one hand the outstanding mechanical properties of hardened UHPFRC allow slender and light building elements, which almost reach the aesthetic occurrence of steel structures. On the other hand its good rheological properties in the initial liquid state can easily be utilised in order to get effective bond to other materials. Hence, mixed building technologies can be developed, where each material contributes its beneficial properties. An impressive example for such developments is the glass-concrete-technology, which combines the robustness of reinforced concrete and the elegance end transparency of glass.
Mixed building technologies (Composite Structures) are generally based on adhesion between the different components. Adhesion depends on numerous parameters like chemical composition, wetability, roughness and morphology etc. which also lead to several different bond mechanisms. These complex interdependencies are not studied systematically yet. The current models only consider the roughness characterised by the mean roughness depth and the strength of the concrete.
This proposal presents a coherent multi-disciplinary approach to study these phenomena. Investigations of the interfacial zone with electron microscopy and computer tomography will give information about the chemical and the geometrical mechanisms of adhesion. Intermolecular forces will be considered by a thermo dynamical approach. Information about the amount of these forces is expected to get by experimental determination of the surface energy of both materials. The theory proposed bases on the correlation between true contact surface and adhesive power. Therefore, special attention will be given on the measuring of the geometry of the surface in a micro scale. The method of evaluation of the measured data will depend on the wetting property of the applied UHPFRC. An extensive mechanical testing program will complete the necessary data for the finding of a reliable calculation model for adhesive bond strength as well as a meaningful constitutive law.
The results of the project will provide the scientific base for safe design of innovative composite constructions with UHPFRC. Moreover, the theoretical model will be formulated by simplified but really existing phenomena, which should provide the possibility for an easy transfer to other materials.