minor phases including kaolinite (2.5 %), akermanite (1.4 %), dolomite (0.6 %), chlorite (0.2 %) and arcanite (0.1 %). Figure 4 – Mineralogical composition of PT1, PT2, PT3, and PT4 determined by XRD-Rietveld. 3.4 Samples pH and moisture content The pH determinations were carried out at FEUP, and the results of pH measurements in solutions with distilled water and CaCl2 are presented in Table 1. The difference in the results between the two methods can be neglected. The PT1 samples exhibited a pH of approximately 6, indicating slight acidity. PT2 displayed pH values ranging from 9.04 to 9.57; PT3, 7.56 to 8.51; and PT4, 7.41 to 7.86, all suggesting mildly alkaline conditions. Table 1 – Mine residues pH determined in solution with distilled water and CaCl2 solution PT1 PT2 PT3 PT4 Subsample H2O CaCl2 H2O CaCl2 H2O CaCl2 H2O CaCl2 A 5.80 5.75 9.04 8.82 7.80 7.56 7.91 7.49 B 5.86 5.74 9.26 8.91 7.62 7.75 7.90 7.48 C 5.94 5.79 9.44 8.97 8.51 8.05 7.67 7.46 D 5.92 5.94 9.57 8.93 8.43 8.05 7.86 7.41 Moisture content was determined at both SECIL and FEUP in accordance with EN 1097-5. PT1 showed moisture levels of approximately 44%, while PT2 presented 33%. For PT3 and PT4 samples, moisture content was not assessed because both were delivered and analyzed as dry materials. 3.5 Microstructural Characteristics
RkJQdWJsaXNoZXIy MTM0Mzk2