Characterisation and activation of graphite mine tailings for use in cementitious binders

The widespread use and production of Portland cement, amounting to 4.10 billion tonnes annually, poses challenges in acquiring quality raw materials. Also, the demands associated with the global development had led to intensified mining and production of significant quantity of mineral wastes including mine tailing. The quantity of disposed mine tailing is about 217 km3 at present with a predicted annual addition of 12.30 km3 to this volume. This poses major environmental, economic, social, and legal concerns. The Construction and Building materials research under Horizon 2020 program of Europe 2020 strategy promotes the materials for energy efficiency including materials with low embodied energy and materials capable of reusing a high waste content. Use of mine tailings, with a chemical and oxide composition similar to supplementary cementitious materials, in cementitious binders emerges as a potential solution to the above-mentioned problems. However, documented challenges, such as crystallinity, variations physical, chemical, and mineralogical characteristics, acid mine drainage, and heavy metal leaching, hinder its immediate use as a cement precursor. This study focuses on developing a suitable treatment for a siliceous mine tailing from graphite mining for its use as a binder precursor. In this study, mineralogical and activation data are presented with respect to graphite tailings. Mechanical and thermal activation protocols were developed, and the processed tailings were assessed in terms of their physico-chemical properties. The mine tailing exhibited high SiO2 composition 58.5 % and was predominantly crystalline. The XRD analysis indicated the possibility of activation by milling and calcination. The characteristics and reactivity of activated samples indicated that the samples calcined at 850 °C exhibited higher heat of hydration in R3 tests and samples milled for 90 min exhibited higher solubility in alkaline environment.