# Grain Size Effect in Elution Test of Electric Arc Furnace Slag
## 3 Results
### Leaching Test  
National legislations regulate the procedures for the leaching test as well as the physical and chemical analysis of the slags. The results are usually compared with the limit values and depend upon the final destination of the materials. The pH value of the leachates is between 9 and 11, and the correlation with the process parameters is not significant. The results of the Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-AES) analysis are reported in Table 3. The relative standard deviation (RSD) of the data is fixed at 10%. For the identified elements, four concentration ranges can  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Position**} & \multirow{2}{*}{**O**} & \multirow{2}{*}{**Mg**} & \multirow{2}{*}{**Al**} & \multirow{2}{*}{**Si**} & \multirow{2}{*}{**Ca**} & \multirow{2}{*}{**Ti**} & \multirow{2}{*}{**Cr**} & \multirow{2}{*}{**Mn**} & \multirow{2}{*}{**Fe**} & \multirow{2}{*}{**Phases Identification**} \\ \cline{5-12}  
be identified: above 1 mg/L are detected for Ca, Si, K and Ba; between 0.1 and 1 mg/L for Sr, V and Mo; between 10 ug/L and 100 ug/L for P, Cr, Fe, Co, Zn, Se and Rb; less than 10 ug/L for Mn, Cu, In, Pb and Cd. The higher is the pH the higher is the release of Ba. The intrinsic variability of leaching tests of the same sample (intra-sample variability) has been evaluated for SiO\({}_{2}\) stabilized slag (namely D and E). Samples D1-D2 and E1-E2 were collected from two different plants in two different days. The leaching test results have been compared in terms of average values and relative standard deviations (RSD%) (Table 4). A high variability in the results is observed, probably due to the sampling or to the furnace feeding. In general, the RSD is high when the element concentration is low. Indeed, descriptive statistics, in terms of minimum and maximum RSD range, per each concentration class defined above, highlights an inverse relationship with the concentration. A higher variability is observed in samples E1 E2 than in samples D1 D2. The intra-sample variability is similar to that observed among the samples (see Supplementary Material Table S2). The same result was obtained with samples of different plants. The principal components analysis confirms the absence of any correlation among samples belonging to the same cooling rate category. The analysis of samples B, C, D1, and E1 have been repeated with the same standard procedure (UNI EN 12,457 2) in a second laboratory to check the repeatability of the test. Results obtained by the two laboratories are not different, suggesting that the primary source of variability is the sample non-homogeneity (see Supplementary Material Table S3). To evaluate the effect of the grain size on the leaching test results, two granularities--4 and 10 mm, respectively--are considered according to EN 12,457 Part 2 and Part 4. The results of samples B, C, D1 and E1 are reported in Table 5. For most of the elements, the highest concentrations are found in the specimens with the lowest granularity, possibly related to their high surface area.