In the context of the application of carbon Textile Reinforced Concrete (TRC) layers for the durable repair of building surfaces, uniaxial tensile tests on rectangular TRC samples were carried out to compare the bond and load-bearing behavior of an epoxy-impregnated carbon textile and its surface modified version. The aim of the surface modification, consisting of a subsequent coating with epoxy resin and sanding with quartz sand, is the improvement of the composite material regarding crack width reduction and an increase of the load-bearing capacity. A total of 15 series were examined and the parameters: reinforcement type, orientation and ratio were varied. In addition, long-term load tests were conducted. An optical 3D-video measuring system in combination with a DIC-software was used, which allowed the analysis of the process of crack formation during the entire testing time. With the surface modified reinforcement the formation of approx. 1.5 times the number of cracks with averagely 33 % smaller crack widths and up to 50 % smaller crack spacings were observed, regardless of the ratio of reinforcement. The residual behaviour of the series subjected to a permanent load of 1500 MPa over 1000 h showed no reduction of the tensile stress compared to short-term tests.

Carbon textile reinforced concrete (CTRC) has been investigated in terms of its elevated temperature and fire behavior in order to evaluate the influence of impregnation materials. Elevated temperature tests have already been carried out for material combinations of CTRC. For the tensile strength and the bond behavior between textile reinforcement and concrete, the impregnation of the textile reinforcement is the influencing factor. Impregnation materials such as epoxy-resin (EP) or styrene butadiene rubber (SBR) showed a deterioration of the elevated temperature behavior compared to unimpregnated materials. The aim of this paper is to close the research gap on the elevated temperature behavior of carbon textile reinforced specimens impregnated with silicic acid ester, epoxy-resin, and epoxy-resin additionally surface-modified with quartz sand. For this purpose, stationary and transient tensile tests at elevated temperatures up to 1000 °C were performed. Furthermore, thermal analysis of the impregnation materials was performed to analyze the tensile tests by correlating the chemical examination with the experimental test results, and the ignitability of the reinforcements was studied using single flame tests. For the investigated reinforcement materials, the failure temperature of the specimens increases with decreasing tensile strength load level for all test specimens. In comparison to the epoxy-resin impregnation material, the silicic acid ester impregnation resulted in higher failure temperatures for comparable load levels. The decomposition of the impregnation materials proved to be a decisive factor due to comparatively evaluated thermal analysis.

To reduce resource consumption and the carbon footprint of the construction industry, new construction principles that stipulate the minimisation of materials are urgently needed. Floor slabs show high potential for saving materials and CO₂ emissions, as they account for around 50% of the total volume of concrete used worldwide. A promising approach is the use of corrosion-resistant carbon fibre-reinforced polymer (CFRP) reinforcement, which requires only a small concrete cover to meet bond requirements. Regarding the component’s topology, material-efficient ribbed or waffle slabs have been built for decades but their execution has declined owing to their labour-intense production, which calls for manual installation of the formwork. A recently proposed extrusion manufacturing process combines both approaches for material-minimised construction and allows the fast and formwork-free production of carbon reinforced concrete (CRC) components. This article describes the concept, the finding of the form, fabrication and experimental testing of an innovative ribbed floor slab composed of precast extruded carbon reinforced concrete (ExCRC) webs. The novel floor slab consists of a conventionally cast thin-walled top slab and shaped, load-adapted ExCRC webs to achieve high utilisaton of the structural member. The ribbed slab provides a lightweight structural system with drastic savings in dead load compared with a conventional steel reinforced slab. In addition, the high durability and service life of the novel floor slabs makes them ideal components to be recovered after an initial life cycle and to be re-used in new construction projects. The paper gives an outlook to the full-scale production of one-way and two-way slab systems made of ExCRC such as ribbed slabs, waffle slabs and sandwich slabs with a honeycomb infill.