## 2 Materials and Methodology
### Sample Installation and the Direct Shear Test Procedure
This practice has been recorded in the construction of rammed earth walls around the world [38] but also in eastern Croatia, where the mixture for installation is prepared at least 12 to 24 h before installation [42]. A certain amount of water was also previously added to the cereal straw and hemp fibers (approximately 24 h before installation) in order to absorb a sufficient amount of water to reach a saturated, surface-dry state, and on the day of installation, they were mixed with the soil mixture. Lime was added to the mixtures (to which a certain amount of water had been added at least 24 h beforehand) immediately before sample compaction in order to prevent binding before sample installation. \begin{table}
\begin{tabular}{c c c c c} \hline
**ID** & \(w_{avg,0}\), /\% 1  & \(w_{avg,2 day}\), /\% 3  & \(w_{avg,2 day}\) /\% 4  \\ \hline M1 & 20.5 & 20.5 & 1.8 & 1.4 \\ M2 & 13.3 & 12.9 & 1.1 & 0.9 \\ M3 & 13.4 & 12.1 & 1.3 & 1.0 \\ M4 & 13.0 & 12.5 & 1.4 & 1.1 \\ M5 & 14.1 & 13.6 & 1.4 & 1.0 \\ M6 & 16.6 & 15.0 & 1.4 & 1.1 \\ M7 & 14.2 & 13.6 & 1.4 & 1.1 \\ M8 & 14.2 & 13.6 & 1.5 & 1.1 \\ M9 & 13.3 & 13.0 & 1.4 & 1.1 \\ M10 & 14.1 & 13.6 & 1.4 & 1.1 \\ M11 & 14.2 & 13.5 & 1.6 & 0.9 \\ \hline \end{tabular}
\end{table} 
Table 4: Moisture content of the mixtures. A Proctor rammer type A (weight 2.5 kg, diameter 50 mm, drop height 305 mm) was used for compaction. Following installation with controlled compaction energy, a foil was placed on the first layer, and approximately 0.5 kg of the material of the second layer was added, after which a smaller mold with dimensions of 100 \(\times\) 100 \(\times\) 20 mm was placed. After adding the remaining material of the second layer, the second layer was compacted. The foil had the function of easier separation of the compacted layers and of protecting the sample in the smaller mold from possible damage when separating the excess soil. The position of the smaller mold, inside which the test specimen was located, was selected within the lower third of the specimen height. The reason for this is that during the inspection of traditional rammed earth houses in eastern Croatia, the parts with the most voids were observed in the lower third of the layers, which are potentially critical places in the walls. In accordance with the information collected from the field survey [28; 35], the height of the layers for compaction in the mold was chosen, which was approximately 100 mm (in a compacted state). The height of the compacted layers of rammed earth in traditional houses from the area of eastern Croatia ranges from 50 to 150 m [28]. The specimen was pressed from the smaller mold (after the necessary measurements/weighing) into the shearbox mold for the specimens that were tested on the same day. Specimens aged 7 and 28 days were pressed out of the mold onto the pad, taken to the climate chamber and kept under controlled conditions. The average moisture contents of the samples during testing are given in Table 4.  
Tests were performed in direct shear devices AUTOSHEAR (CONTROLS), where specimen shearing was performed along a predefined failure plane. The test was carried out in two phases: (i) consolidation and (ii) shearing. The vertical stresses (\(\sigma_{n}\)) to which the samples were subjected during consolidation and shearing were 25 kPa, 50 kPa and 100 kPa, which are common internal stresses in the walls of traditional rammed earth houses from the area of eastern Croatia. In the case of samples that were tested on the day of installation, a longer duration of consolidation was required (according to Ref. [32]), while in the case of samples that were tested after 7 and 28 days, a shorter duration of consolidation was conducted. The shear rate was 1 mm/min. The higher shear rate was chosen for comparison with other tests conducted as part of a larger study, and the stated rate was also recorded in other rammed earth studies [21; 22].