Abstract
Coal mining wastes are associated with serious environmental problems; they have potential as building materials, including alkali-activated cement. In this study, the effect of different coal mining wastes on the mechanical properties and microstructural development of alkali-activated materials (AAMs) was evaluated through XRD, SEM and FTIR spectroscopy. Different alkali-activated compounds were produced; the alkaline solution was composed of NaOH+Na2SiO3. The results obtained using the calcined coal sludge showed excellent mechanical performance, with compressive strength higher than 60 MPa. However, addition of metakaolin and ordinary Portland cement was necessary to increase the mechanical performance of calcined coal gangue materials. The formation of N-A-S-H gel and the incorporation of iron ions into the cementitious matrix were evidenced. Ultrasonic pulse velocity indicated the early polymerization during the reaction processes. The study verified that the different characteristics of the wastes influence the performance of alkali-activated materials.
Highlights
Coal mining wastes are associated with serious environmental problems; they have potential as building materials, including alkali-activated cement
Better mechanical performance was observed for all CST-activated materials (AAMs) compared to CGT and SPC, which can be explained by differences in the chemical properties, fineness, and mineralogical content
Coal gangue was used as a binder in AAM systems and the main conclusions that can be drawn from this study are:
Summary
Coal mining wastes are associated with serious environmental problems; they have potential as building materials, including alkali-activated cement. RESUMEN: Estudio de la influencia de los diferentes residuos de carbón como aluminosilicatos en las propiedades mecánicas y la microestructura de los cementos activados alcalinamente. Some aluminosilicates are present in the mineral phases, with little or no reactivity, and pre-treatment processes can promote more amorphous phase formation and less crystalline products [6, 9] These characteristics can enhance the potential for coal gangue to be used in the production of construction materials. The main focus of studies on coal wastes has been their potential for use as pozzolanic supplementary materials [7, 10, 12, 14, 15], aggregate materials [11] or as a raw material for the production of bricks [16,17]. These possible applications would reduce the large-scale production of solid wastes and, as a consequence, less land area would be needed for the final disposal of coal wastes
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