Relationships between impurities and texture of dolostones with milling operations and thermal behaviour

Abstract

This study offers a comprehensive approach that makes it possible to describe the main properties of two Argentine dolostones and to delve deeper into the impurities present and their influence on the final behaviour during processing steps such as milling and thermal treatments. The rocks are both calcic dolomites: D-SJ came from the Precordillera de los Andes (Upper Cambric period) and D-BA came from and older formation (Precambric age). Various techniques such as optical microscopy, SEM/EDS, LECO, wet chemical analysis, LOI determination and XRD were all used in the investigation. The milling performance and the thermal behaviour (≤ 1100 ◦C) of dolostones were also studied, together with the thermodynamic simulation between 1000 and 2500 ◦C. The dolostones have similar impurities (mainly calcite, quartz, potassium-containing alumino-silicates and different forms of iron) but their content is higher in D-BA than in D-SJ. This rock is highly heterogeneous, with larger crystals and more irregular faces than those of D-BA, which has a homogeneous appearance, higher porosity and a larger crystallite size and degree of Mg–Ca cation ordering. D-SJ showed a higher resistance during the comminution process than D-BA, giving coarser particle size distributions. The thermal evolution of both dolostones was similar up to 1100 ◦C, although the temperatures at which decomposition processes begin were, in general, slightly higher for D-BA than for the D-SJ, but the reaction was completed in a narrower thermal interval for the former. The thermal behaviour of D-BA was less affected by the granulometry of the sample. The thermodynamic simulation of the thermal evolution of dolostones shows that D-BA presents a lower temperature which the first drop of liquid appears than D-SJ, and a larger amount of liquid formed at the current temperatures used for the sintering step. Although similar in certain aspects, the used thorough approach reveals that the dolostones differ greatly in other ways, which may affect how they are processed as powdered raw materials for industrial ceramic-based products.