Abstract
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 (CaOf) content test. The anhydrous clinker mineral phases C3S (Ca3SiO5), C2S (Ca2SiO4), C3A (Ca3Al2O6), and C4AF (Ca4Al2Fe2O10) 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.
Highlights
IntroductionGeopolymers are a class of alkaline aluminosilicate materials, synthesized by the activation of various reactive aluminosilicate materials of geological origin (e.g., metakaolin) or industrial by-products (e.g., fly ash) by a concentrated alkali hydroxide silicate solution
The X-ray diffraction (XRD) pattern of fly ashbasedgeopolymer shows a mixture of quartz and mullite phases
Both patterns show a broad halo peak at a low 2-theta position, which indicates the presence of amorphous phases. These results agree well with those recently reported in the literature [18,19]. It is well-known that the geopolymer phases are amorphous in nature
Summary
Geopolymers are a class of alkaline aluminosilicate materials, synthesized by the activation of various reactive aluminosilicate materials of geological origin (e.g., metakaolin) or industrial by-products (e.g., fly ash) by a concentrated alkali hydroxide silicate solution. These materials have several advantages: easy preparation, low curing temperature ≤100 ◦ C), reduced gas emissions, and good properties [1,2]. For these reasons, geopolymer materials are considered a promising and sustainable ecological alternative to conventional materials, especially cement and ceramics
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