## Materials and Methods
### Preparation of CT Specimens  
The selected specimen shape resembles the one used for the evaluation of crack propagation in metals (ASTME647 [42]), the so-called Compact Tension (CT) specimen. Preparation of CT specimens was done after 7 days of curing. The cured composite cubes were saw-cut into 12 mm thick plates, using a stationary block cutter with a diamond saw blade. In cases of uneven cutting plane, the surface was manually smoothened with an angle grinder (with a diamond grinding disk). Clear access to the surface where the tensile creep strain progression becomes visible was important. To predict the maximum stress intensity zone and limit the FOV area (where the creep strains initiate), the 80 mm long \begin{table}
\begin{tabular}{l c c c} \hline \hline \multirow{2}{*}{**Component**} & \multicolumn{2}{c}{**Quantity**} & **Water to** \\ \cline{2-4}  & **kg/m\({}^{3}\)** & **wt\% 1** & **Cement Ratio** \\ \hline Water (tap water) & 319.2 & & 0.5 \\ Portland cement (Aalborg White, CEM 1 52.5 R) & 638.4 & & \\ Sand (0.0–0.8 mm) & 1276.9 & & \\ PVA fibres (mesofibres, L = 12 mm,\(\diameter\)160 \(\mu\)m, & & 1 & \\ E = 30 GPa) & & 0.09 2  \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cement composite mix. and 0.5 mm wide notch was cut using a tabletop bandsaw Proxxiromot Mrosp 240/E (with a diamond blade). The tensile stress maximum intensity was achieved at the tip of the notch. The depth of the specimen was also reduced, promoting the plane stress state. The available path for the progress of the initiated strain parallel to the notch was 30 mm. The distance between the loading axis and the tip of the notch was 50 mm. Two drill holes with a diameter of 20 mm were made in further steps, where a stationary drilling machine (with a diamond drilling crown) was used. Summarising, the dimensions adopted for the specimens were 150 mm by 150 mm (perpendicular and parallel to the notch) and 12 mm (thickness). CT specimen geometry was prepared according to Figure 1. The preparation of such a methodology provides test specimens representing the situation close to real CCC structures since the fibres are oriented randomly and dispersed relatively evenly throughout the volume. When the specimens were finished, they were thoroughly cleaned under running tap water and dried in room condition (+20 \({}^{\circ}\)C, RH = 60%) for 24 h. After that, the region of FOV of each specimen was observed, and any protruding parts of the fibres were trimmed by hand using a thin razor blade. Trimming has a beneficial effect on further surface preparation. Such an action was also taken due to the previous trialling where unwanted shadows from sticking fibre ends were noticed (in the DIC images). In some cases, even such diminutive surface irregularities can complicate camera focusing (discussed in Section 2.3). 2D-DIC is based on such a principle that a unique surface pattern follows the deformed object itself while a mechanical test is performed. Then, several digital images are taken that capture changes throughout the time. Preferably, DIC software uses a dense stochastic speckle pattern at the surface of the test specimen to create overlapping subsets of points, matching and analysing deviations from the initial state (e.g., the first image in the series, also called the reference image) [34]. For applying a speckle pattern, an airbrush Royalmax TC-12K with black acrylic-based spray paint was used. In earlier trials, it was found that the speckle pattern tends to emanate and fade due to absorbing into the uncoated, porous surface of the material. Furthermore, in this research, white Aalborg cement was used for the mortar mix; thus, a bright white colour tone (close to RAL 9016) was obtained for the final hardened material. Because of such properties of the surface, the captured images happened to be overexposed (there was no valid solution found by adjusting the camera or the lighting settings). The DIC software could not evaluate the strains at the desired locations within the FOV.