Identification of material properties of FRC using coupled modeling

In this paper identification of material properties in the vicinity of reinforcement of FRC is based on coupled modeling. It consists of the mutual comparison of experimental and mathematical models with the aim of obtaining a more accurate estimate of stresses in experiments and more reliable input data in the mathematical treatment. As the measurements on site are very expensive, experiments simulating the system of the concrete-surrounding medium are prepared in scale models in stands (basins with a glazed front side and a length of 2-6 in), where physically equivalent materials substitute the real ones. Based on similarity rules, very good agreement with reality is attained. Typical applications are found in tunnel construction and reinforcement of slopes using recycled reinforced concretes (waste of bricks and used concrete serve as an aggregate in new built concretes). In order to identify the most exacting location in the concrete, coupled mechanical pullout tests are carried out together with chemical analysis conducted by Raman spectroscopy. It appears that the extent of ettringite on the interface fiber-surrounding matrix plays a very important role, and also other minerals occurring there can influence the interface situation, but less than the ettringite. In the numerical treatment a useful trick is applied, which stems from the idea of generalization of temperature effects - eigenparameters. They describe the plastic behavior as well as the damage at the interfaces. Their applications in the paper will be the most important element of the creation of the coupled model.