Experimental Study on the Load Bearing Behaviour of Textile Reinforced Concrete under Uniaxial Compression – Phase II: Influence of Lateral Compression and Tension

• Applicant: Professor Dr.-Ing. Manfred Curbach
• Subject Area: Structural Engineering, Building Informatics and Construction Operation
• Term: from 2013 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 235549595

Investigations of the applicant show that the influence of textile grids on the load-bearing behaviour of textile reinforced concrete (TRC) under compression is not negligible. In addition to the impact of textiles, the tests showed that even the manufacturing process by manual lamination affects the specimen’s maximum strength negatively in regard to casted ones. Furthermore, the orientation of the layers to the loading direction has a significant influence on the concrete strength. The anisotropic material behaviour of unreinforced specimens, which were manufactured layer by layer, is even stronger for TRC specimens. Here, the variation of the orientation of the textile plane leads even to different failure modes. If the textiles are aligned parallel to the loading direction, a brittle failure occurs. On the other hand, a perpendicular alignment of the textiles to the loading direction will cause a quite ductile behaviour. These differences are probably due to two opposing mechanisms. On the one hand, the textiles act as a discontinuity, because they cannot transfer any compressive stresses perpendicular to their longitudinal direction. This causes diversions in the stress field in the specimen. These disturbances induce additional tensile stresses into the concrete, which lead to an accelerated failure. On the other hand, the textiles cause a lateral constraint, and stabilize the specimens during the loading process. These mechanisms dominate material behaviour and failure mode especially if the textiles are aligned perpendicular to the loading direction. The variation of different parameters, like layer spacing, yarn diameter, mesh size or the use of textile layers located offset from each other showed the various impact factors on the material behaviour of TRC under compression. A result of all tests is that the influence of the single parameters on the strength and the anisotropy decreases with a taller layer spacing.What is open is the question of the transferability of the findings of the obtained results to practical components. A first step towards the solution is to be carried out in the second phase of the project by investigating the biaxial material behaviour of TRC under compression-compression and compression-tension loads, because in most of the structural members, there is a multiaxial stress state, e.g. at beams, which are exposed to shear or torsional loads. The planed tests should mainly investigate the impact of the following parameters: kind of textile reinforcement, manufacturing process and different stress ratios. The results of the uni- and biaxial tests are supposed to be a basis for a numerical material model to conduct virtual parameter studies on large-scale concrete members, like beams or columns. The goal of the numerical calculations is to reduce the number of test on such concrete members, which are quite complex and expensive, but necessary for validation of an engineering model in a 3rd funding period.

• DFG Programme: Research Grants