Heat-induced phase transitions in mining tailings to create alternative supplementary cementitious materials

The present study investigated the mineralogical changes in five different mining tailings (i.e., bauxite, gold, copper, and lead) with varying heating conditions (i.e., non-heating, 600 °C, and 900 °C) to explore the feasibility of using thermally treated tailings as supplementary cementitious materials. In particular, among the used heating conditions, bauxite tailings heated to 600 °C showed the best reactivity as supplementary cementitious material and thus rigorously studied the fundamentals of the increased reactivity. Well-balanced Al and Si dissolutions from the thermal decompositions of gibbsite, boehmite, and kaolinite seem to be the result of the best reactivity at the bauxite tailings heated at 600 °C among used heating conditions. It is also noted that, although tailings originated from the same types of ore or contained high Al2O3 and SiO2 contents, their supplementary cementitious reactivity differed depending on the contents of highly (i) soluble, (ii) thermally decomposable, and (iii) Al or Si-bearing minerals such as boehmite, gibbsite, kaolinite, and chamosite.