## 3 Experimental Campaign
### Specimens and Test Setup  
The specimen comprised a composite cantilever consisting of an acrylic tube filled with cement paste. Further details can be found elsewhere [12]. The mold used for the preparation of the sample is a 500 mm long acrylic tube characterized by internal (\(\phi_{i}\)) and external (\(\phi_{e}\)) diameters equal to 16 mm and 20 mm, respectively. Before casting, a polystyrene cap (Figure 1a), weighing less than 0.1 g, was glued to the free end of the tube. Then, the mix was prepared as reported in Section 3.1. Once the mixture was ready, the pouring phase was executed as follows: (i) the acrylic tube was inclined at approximately 15\({}^{\circ}\) with respect to the vertical; (ii) the mix was poured by applying a slight pressure by means of a flexible tube starting from the capped end of the beam; (iii) a mild vibration \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Specimen**} & \multirow{2}{*}{**Material**} & \multicolumn{2}{c}{**Experimental Variable**} \\ \cline{3-4}  & & **T (\({}^{\circ}\)C)** & **Time (Day)** \\ \hline C325d0 & CEM IV/B (P) 32.5 R-SR & 20 \(\pm\) 0.5 & 0 \\ C325d30 & CEM IV/B (P) 32.5 R-SR & 20 \(\pm\) 0.5 & 30 \\ C325d240 & CEM IV/B (P) 32.5 R-SR & 20 \(\pm\) 0.5 & 240 \\ C325d360 & CEM IV/B (P) 32.5 R-SR & 20 \(\pm\) 0.5 & 360 \\ C425d0 & CEM II/A-LL 42.5 R & 20 \(\pm\) 0.5 & 0 \\ C425d240 & CEM II/A-LL 42.5 R & 20 \(\pm\) 0.5 & 240 \\ C325T20 & CEM IV/B (P) 32.5 R-SR & 20 \(\pm\) 0.5 & 0 \\ C325T15 & CEM IV/B (P) 32.5 R-SR & 15 \(\pm\) 0.5 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Test specimens and experimental variables. was externally applied to the tube to eliminate voids and air bubbles. After casting, the specimen was placed in a vertical position, and a purge system (Figure 1b) was mounted on the free end of the specimen. The purge system consisted of a nut glued onto a washer and a bolt. It acted like a plug: by gently screwing the bolt, the remaining air bubbles were removed. At the end of the operations, the specimen was positioned horizontally and placed within the clamping device depicted in Figure 1c,d in order to obtain a composite cantilever beam with a free span equal to 400 mm. The described specimen preparation procedure allows for achieving conventional controlled curing conditions in agreement with the original procedure [12]. The restraint system consisted of two steel plates: the lower one was fixed to the strong floor of the laboratory, and the upper one was screwed onto it after positioning the specimen; a torque wrench was used to gradually tighten the bolts while controlling the tilt angles by means of integrated bubble levels (see Figure 2). Notice that, with respect to the original setup proposed by [PERSON] et al. [12], a slight modification of the configuration of the clamping device was introduced to prevent undesirable localized stress concentrations on the acrylic tube. Figure 1: Views of specimen ends after casting (**a**,**b**), and scheme of clamping device (**c**,**d**). In Figure 2, general views of the specimen (Figure 2a) and of the experimental setup (Figure 2b) are shown. A piezoelectric accelerometer with 7.5 g weight and 1 V/g sensitivity was glued to the free end of the beam. A low-power fan was used to improve the signal-to-noise ratio (by increasing the vibration response of the specimens without significantly altering the broadband nature of the excitation) in view of the identification of the fundamental natural frequency. The data acquisition system consisted of programmable hardware controlled by the S2-DDA software v.2.0.0 [35]. It was characterized by a 24-bit resolution and analog anti-aliasing filter. A sampling frequency of 100 Hz was adopted coherently with the expected value of the fundamental natural frequency of the beam. It is worth noting that adhesion plays a primary role in test execution and data processing.