# Granular Material Development Applied in an Experimental Section for Civil Engineering Purposes
## Materials and Methods
### Methods  
The WBA, APC, crushed M and GM were homogenized and quartered (1/16), obtaining different subsamples. Representative subsamples of WBA, APC, crushed M and GM were taken for chemical characterization. The semi-quantitative elemental analysis of WBA, APC, crushed M and GM was carried out by a spectrophotometer Panalytical Philips PW 2400 sequential X-ray fluorescence (XRF) equipped with the software UniQuant(r) V5.0. Besides this, X-ray diffraction (XRD) analysis was used to determine the crystalline phases of the samples by means of a Bragg-Brentano Siemens D-500 powder diffractometer device with CuK\(\alpha\) radiation. The humidity (H, %) and dried weight (W\({}_{\text{D}}\), %) of the samples were also evaluated. Dynamic leaching tests were performed for four samples per duplicate, following the standard UNE-EN 12457-4. The dynamic leaching tests followed the Department of the Environment of the Generalitat de Catalunya's [28] classifying of solid wastes in accordance with the limits established in the Criteria and Procedures for the Waste Acceptance in Landfills [29], described in the European Landfills Directive. Thus, based on their leaching potential, three levels of different wastes were established, as showed in Table 1: inert solid wastes, non-hazardous wastes and hazardous wastes. The dynamic leaching test consisted of placing a solid with a particle size \(<\) 10 mm in contact with deionized water in an L/S ratio of 10 L kg\({}^{-1}\) for 24 h at room temperature, with continuous rotating agitation. The leachates were filtered with a 0.45 um membrane of nitrocellulose. Two aliquots were tested per sample. Two replicates of each replicate were extracted for further analysis by means of the ICP-MS technique by a PerkinElmer ELAN device, evaluating As, Ba, total Cr, Cu, Hg, Mo, Ni, Pb and Zn. Likewise, the pH and conductivity (k) of the leachates were analyzed. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Element** & **Inert** & **Non-Hazardous** & **Hazardous** \\ \hline As & 0.5 & 2 & 25 \\ Ba & 20 & 100 & 300 \\ Cr & 0.5 & 10 & 70 \\ Cu & 2 & 50 & 100 \\ Hg & 0.01 & 0.2 & 2 \\ Mo & 0.5 & 10 & 30 \\ Ni & 0.4 & 10 & 40 \\ Pb & 0.5 & 10 & 50 \\ Zn & 4 & 50 & 200 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Limit values (mg\(\cdot\)kg\({}^{-1}\)) established by the European Landfill Directive [29] to classify solid waste for its admission to landfills. Figure 4: (**a**) Image of the distribution of the pipes as fish spines. (**b**) Detail of the pipes unification before collecting the leachates in the collection tank. In addition, percolation column long-term tests on the WBA, crushed M and GM were performed per duplicate, following the CEN/TS 16,637 standard. These tests consist of placing around 1 kg of dry material (separately WBA, crushed M and GM) in a cylindrical column (\(\emptyset\) = 50 mm; h = 310 mm). The deionized water was passed through from the bottom to the top of the column (bottom-up) with the help of a pump, set at 24 mL-h-1. The L/S ratios evaluated were 0.1, 0.2, 0.5, 1, 2, 5 and 10. Afterwards, for each of the seven eluates (E1, E1, E3, E4, E5, E6 and E7) obtained for each column, the determined parameters were pH, k, and the analysis by ICP-MS of As, Ba, total Cr, Cu, Hg, Mo, Ni, Pb and Zn. There exist some leaching test methods available that can differ according to aspects such as the material type to be tested, the mass, the particle size, the leachate volume and the duration of the assay. Leaching tests for soils can be classified as batch tests, percolation column tests, and sequential leaching tests or monolithic and bulk tests [30]. These methods aim to determine the concentrations of chemicals in the water that was in contact with the soil for a certain period [31]. Different standardized batch tests and percolation column tests are available for assessing the metal(loid) solubility and associated leaching. It is necessary to homogenize and sieve the soil before leaching [32].