Evaluation of Raw Materials in Abandoned Kaolin Quarry as Potential Geopolymers

The abandoned kaolin quarries of the Serrenti-Furtei area (South-Sardinia, Italy) where widely exploited for long time during the last century, until the late 70's. The kaolinized bodies have been no longer exploited because of low quality of the ore which results too rich in silica and pyrite for a conventional industrial destination. Nowadays this abandoned open-pit mine constitute an environmental degradation that is in need for a landscape remediation. The aim of this preliminary study is to evaluate the feasibility of using the large stockpiles of material, still in place, as a raw material for the possible production of geopolymers binders based on metakaolin. The use of metakaolin to produce geopolymers mixes has attracted worldwide interests and particularly in the formulation of special cements and mortars. The kaolin samples were thermally activated in a laboratory oven at 530, 630 and 800 °C temperatures. Pastes of thermally activated materials with lime have been prepared and cured at different times. The reactions that took place in the metakaolin-lime-water systems have been monitored using thermogravimetric analysis, differential thermal analysis and X-ray diffraction analysis. In this paper we also evaluate, using proximal sensing photogrammetric survey technique, the different stockpile volumes of mining waste to obtain a detailed quantification of the potential raw material resources. The large availability of these potential resources encourages further studies for the transformation process and the use of these materials in the binders sector.