# Shear Capacity of Textile-Reinforced Concrete Slabs without Shear Reinforcement
## 2 Experimental Investigation on Shear Capacity
### Reinforcement  
Non-metallic textile reinforcement can be categorized in different ways, regarding its fiber material, its impregnation material, or its geometry. As fiber materials, carbon, alkali resistant (AR-) glass, aramid, and basalt are usually utilized. Carbon and AR-Glass are the most common and there are several commercially available products world-wide. As impregnation materials, elastic rubber-based systems such as styrene-butadiene-rubber, as well as stiffer types based on epoxy resin or polyacrylate, are widespread. Nowadays, non-impregnated textiles (e.g., used in the construction of shell structures in [5] or [60]) are less common for new constructions due to the low efficiency and the low stiffness, which complicates the handling during manufacturing of TRC members. However, they are still used for repair and external retrofitting, especially for masonry walls. Regarding the geometry, one can distinguish the following types: Planar 2D textiles (biaxial or multiaxial), preformed 3D elements made from 2D textiles, and full 3D textiles (see e.g., [59]). Due to the variety of available \begin{table}
\begin{tabular}{c c} \hline \hline
**Shear Slenderness \(a/d\)** & **Effective Depth** \\ \hline
4 & 4 cm \\
5 & 8 cm \\
6 & 12 cm \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameter variation for the experimental study. Figure 1: Test setup and instrumentation for three-point bending tests. products and combinations, a detailed characterization of the material properties of the reinforcement is indispensable for an experimental campaign on textile-reinforced concrete. It is interesting to note that the mechanical properties of FRP and textile reinforcement are related to different geometrical bases. For textile reinforcement, typically only the filament area without impregnation resin is counted. Reasons for this approach are the non-uniform geometrical cross-section along the axis of individual yarns (Figure 2) and the rather difficult determination of the cross-sectional area due to the small size. As the titer and the filament count of the individual non-impregnated rovings used in production of the textiles are known, the determination of the total filament area per meter is very simple. This is a significant difference to FRP bars or stirrups, for which the geometrical area given by the manufacturer includes the polymeric matrix. In consequence, area-related material characteristics such as stress or modulus of elasticity of impregnated textiles appear higher than for FRP bars, despite similar basis materials and similar compactness. In this study, an epoxy-impregnated biaxial carbon grid was utilized as longitudinal reinforcement. The epoxy-resin was applied and hardened during production by the reinforcement manufacturer. Due to the high stiffness of the mesh, it could not be rolled on regular-sized reels. Hence, in this case, it was delivered in 5 m \(\times\) 1.2 m planar panels. Figure 2a shows the biaxial open grid structure with a 38 mm axial spacing of the yarns, both in longitudinal (warp) and transversal (weft) direction of the fabric. The cross-sectional area of this reinforcement was symmetrical, with 95 mm\({}^{2}\)/m in both directions. The reinforcement layout for this study aimed toward achieving a similar reinforcement ratio for different effective depths. In consequence, the specimens had one to three layers of reinforcement mesh strips of 5 yarns each (Figure 2c). During production, the bottom layer passed beyond the formwork in order to apply a slight prestressing to avoid sagging of the reinforcement (Figure 2b). All layers were aligned so each layers' weft and warp yarns stacked directly on top of each other. This resembles the typical production in practice, as the alignment of openings allows the concrete to pass. In mid-span, an additional fixation for one transversal yarn guaranteed the necessary concrete cover. Furthermore, due to the lower density of the impregnated carbon compared to fresh concrete, the buoyancy could be effectively controlled.