## 2 Materials and Methods
### Characterization of Raw Materials and Mix Design for Concretes  
The raw materials used in the production of concrete are listed below, along with the standard codes by which they have been characterized:  
* Portland cement CEM I 52,5 R, as in Section 2.1;
* Water: as in item 2.1;
* Aggregates: use of natural sand, as in Section 2.1, and gravel (according to UNI EN 12620 [64]) in specific size fractions, as indicated in Table 3, and with the following mixture: sand 100 kg/mc, gravel 730 kg/mc;
* Recycled EPS: polystyrene beans resulting from grinding of industrial scraps. In Table 4, the granulometric analysis is presented. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Samples** & **EPS (1–2)** & **EPS (2–4)** & **EPS (4–6)** & \begin{tabular}{c} **Sand** \\ **(1–2)** \\ \end{tabular} & \begin{tabular}{c} **Sand** \\ **(2–4)** \\ \end{tabular} & \begin{tabular}{c} **Sand** \\ **(4–6)** \\ \end{tabular} & \begin{tabular}{c} **Cement** \\ \end{tabular} & \
\begin{tabular}{c} **Water** \\ **(8–7)** \\ \end{tabular} &
\begin{tabular}{c} **Density** \\ **(8–9)** \\ \end{tabular} \\ \hline  & [kg] & [kg] & [kg] & [kg] & [kg] & [kg] & [kg] & [kg/m\({}^{3}\)] \\ \hline M1 & & & & 1.35 & & 0.45 & 0.225 & 1716.572 \\ \hline M2 & & & 0.0081 & & & 0.45 & 0.225 & 579.057 \\ \hline M3 & & 0.0061 & 0.0041 & & & 0.45 & 0.225 & 580.773 \\ \hline M4 & 0.0061 & 0.0030 & 0.0041 & & & 0.45 & 0.225 & 583.348 \\ \hline M5 & & & 0.0041 & 0.5580 & 0.6140 & & 0.45 & 0.225 & 1569.094 \\ \hline M6 & & & 1.1159 & 0.6140 & 0.4961 & 0.45 & 0.225 & 2459.202 \\ \hline M7 & & & 0.0020 & 1.1159 & 0.6140 & & 0.45 & 0.225 & 2040.359 \\ \hline M8 & & 0.0030 & 0.0020 & 1.1159 & & 0.45 & 0.225 & 1522.445 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mortar. Mix design specifications, with indications of the quantity of each material. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sieve Diameter** & **Sand 0/6 S** & **Gravel G** & **Mix of Aggregates M** & \begin{tabular}{c} **Theoretical Fuller** \\ **Curve C** \\ \end{tabular}  & **Deviation M-C** \\ \hline
**[mm]** & **\%** & **\%** & **\%** & **\%** \\ \hline
20 & 100 & 92.2 & 96.9 & 100 & \(-\)3.1 \\ \hline
16 & 100 & 67.8 & 87.2 & 89.4 & \(-\)2.3 \\ \hline
14 & 100 & 51.0 & 80.5 & 83.7 & \(-\)3.2 \\ \hline
12.5 & 100 & 38.4 & 75.4 & 79.1 & \(-\)3.6 \\ \hline
10 & 100 & 12.9 & 65.2 & 70.7 & \(-\)5.5 \\ \hline
8 & 100 & 3.6 & 61.5 & 63.2 & \(-\)1. In order to propose the use of recycled R-EPS as a lightweight material in concrete, its apparent density was calculated according to the APPENDIX B of UNI 10667-12:2021 [65] standard. The test showed an apparent density equal to 15.2 kg/mc. In reference to the mix design of concrete with a characteristic compressive strength (Rck) of 35 N/sqmm, the experimental process involved progressively replacing the volume of sand with recycled expanded polystyrene (R-EPS). The experimental setup included the preparation of 11 mixtures:  
* S0, which corresponds to the mix design for concrete with Rck of 35 N/sqmm, considered as the reference. * Mixtures from S1 to S4 with R-EPS, volumetrically replacing increasing percentages of sand across the entire particle size distribution, as shown in Table 5.
* Mixtures from S5 to S10 with R-EPS, volumetrically replacing parts of the particle size distribution of sand (particle sizes 1-2 mm, 2-4 mm, and 4-8 mm), as illustrated in Table 5.  
Table 6 displays the quantity of each material used for each tested mixture. \begin{table}
\begin{tabular}{c c c c} \hline
**Sieve Diameter** & **Remain** & **Remain** & **\% in Weight** \\ \hline
**[mm]** & **g** & **\%** & **\%** \\ \hline
8 & 12 & 12 & 12 \\ \hline
4 & 54 & 54 & 54 \\ \hline
2 & 24 & 24 & 24 \\ \hline
1 & 6 & 6 & 6 \\ \hline
0.5 & 2.5 & 3 & 2.5 \\ \hline
0.25 & 1 & 1 & 1 \\ \hline
0.125 & 0.5 & 1 & 0.5 \\ \hline
0.063 & 0 & 0 & 0 \\ \hline \end{tabular}
\end{table} 
Table 4: Concrete. Granulometric analysis of recycled R-EPS, conducted on a total weight of 100 g.