## 4 Materials and Test Specimens  
In this study, an epoxy resin impregnated carbon textile and a high-strength concrete were selected. The chosen biaxial textile solidian GRID Q95/95-CCE-38 from solidian GmbH, whose characteristics where determined in uniaxial single yarn tests [40] (Table 1). A section of the carbon textile reinforcement is displayed in Figure 1.  
The requirements on the concrete had changed due to textile reinforcement, so that the concrete composition had to be adapted. The maximum grain size for the ability of penetration through the textile reinforcement [43], the long-term availability of the raw materials, ecological and economic criteria as well as a short-term feasibility of the results in construction practice were taken into account [44] for the development of the concrete, which was part of the basis project B2 of the C\({}^{3}\) program. The concrete composition used differs slightly from the compositions presented by [PERSON] et al. [44] because locally available raw materials were used. The maximum grain size is 4 mm, which means that the concrete can be classified as mortar. However, due to the high-strength properties, the term concrete was established. The composition of the high-strength concrete is shown in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Substance** & **Density [kg/m\({}^{3}\)]** & **Content [kg/m\({}^{3}\)]** \\ \hline Binder compound CEM II/[PERSON] & 2962 & 707 \\ Quartz sand F38 S & 2650 & 294 \\ Quartz sand 0.1–0.5 mm & 2630 & 243.2 \\ Quartz sand 0.5–1.0 mm & 2630 & 201.4 \\ Quartz sand 1.0–2.0 mm & 2630 & 148.9 \\ Quartz sand 2.0–4.0 mm & 2630 & 593.5 \\ Superplasticizer (polycarboxylatether base) & 1070 & 15 \\ MC-VP-16-0205-02 & Water & 1000 & 165 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mix design of cementitious matrix for concrete HF-2-165-4 (mix design adapted from [44]). Figure 1: Detail of the tested textile carbon reinforcement. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Characteristic** & **Unit** & **Warp Direction (0\({}^{\circ}\))** & **Weft Direction (90\({}^{\circ}\))** \\ \hline Modulus of elasticity & MPa & 244,835 & 243,828 \\ Mean ultimate stress & MPa & 3221 (n = 204 tests) & 3334 (n = 218 tests) \\
5\% quantile ultimate stress & MPa & 2737 & 2762 \\
95\% quantile ultimate stress & MPa & 3705 & 3906 \\ Axial spacing of yarns & mm & 38 & 38 \\ Cross-sectional area per yarn \({}^{1}\) & mm\({}^{2}\) & 3.62 & 3.62 \\ \hline \hline \end{tabular} \({}^{1}\) Filament area without epoxy impregnation.  
\end{table} 
Table 1: Material characteristics of the carbon textile solidian GRID Q95/95-CCE-38 (properties of one individual yarn [41], test setup according to [42]). When concreting, first, the binder and the aggregate are mixed dry for one minute before water and the superplasticizer are added. After a further three minutes of mixing time, the concrete is poured in the formworks. Due to the self-compacting properties of the concrete, no vibration is required. After concreting, the test specimens in the formworks are protected against drying out. After one day, the formworks are removed, and the specimens are stored in water until the 7 th day. From the 8 th day, the samples are stored at room climate (approximately 20 \({}^{\circ}\)C and 65% RH). After reaching a minimum concrete age of 28 days, the test specimens are tested for their short-term, long-term and preloading behavior. The compressive strength and flexural strength of the concrete were determined on test specimens according to DIN EN 196-1 [45] after 28 to 31 days. As an average of 36 specimens, the compressive strength was 123.7 MPa with a coefficient of variation (COV) of 7.7%. The average flexural strength was 12.2 MPa for 18 samples (COV 15.1%). The average modulus of elasticity was determined to be 43,839 MPa (COV 4.9%) [46] on six cylinders of 30 cm height and 15 cm diameter. All test specimens are reinforced with a single layer of the carbon textile. The specimens have dimensions of \(w/t/l=\) 120/30/1000 mm\({}^{3}\).