Preparation of Cement Clinker from Geopolymer-Based Wastes

In order to avoid potential environmental pollution from geopolymer-based material wastes, this work investigated the feasibility of using these materials as alternative raw materials in the preparation of cement clinker. The geopolymer binders and mortars were used as substitutes for natural mineral clays since they are rich in silica and alumina. Simulated geopolymer wastes were prepared by the activation of metakaolin or fly ash by an alkaline silicate solution. The cement-clinkers fired at 1450 °C for 1h were characterized by XRD, XRF, SEM-EDS, and a free lime (CaO(f)) content test. The anhydrous clinker mineral phases C(3)S (Ca(3)SiO(5)), C(2)S (Ca(2)SiO(4)), C(3)A (Ca(3)Al(2)O(6)), and C(4)AF (Ca(4)Al(2)Fe(2)O(10)) were well-crystallized in all investigated formulations. The free lime was lower than 1.3 wt% in all elaborated clinkers, which indicates a high degree of clinkerization. The results demonstrate that geopolymer binder and mortar materials are suitable substitutes for natural mineral clay incement clinker preparation.