Room-temperature phosphate ceramics made with Afşin-Elbistan fly ash /

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2014

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Mahyar, Mahdi

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The mechanical behavior and microstructure of acid-base phosphate ceramics produced at room temperature using coal fly ash from Afşin Elbistan (AE) thermal power plant were investigated. The main goal was to introduce a novel application for this industrial waste which does not meet the standards for use in the cement and concrete industry. Chemically-bonded phosphate ceramics (CBPC) can provide certain advantages over ordinary Portland cement products such as better mechanical strength, better durability, shorter setting time, better high temperature resistance and a lower carbon footprint. The chemical composition of AE fly ash indicated its potential for CBPC production. Activation of the fly ash was done using two phosphate sources; a phosphoric acid solution or a phosphoric acid salt (monopotassium dihydrogen phosphate). Various phosphoric acid solution concentrations and different solution-to-powder ratios were used. To achieve comparable results, acid salt contents with phosphate ion contents equivalent to those of the solutions were chosen. Partial replacement of the fly ash with soda lime glass and calcium aluminate cement was also studied. Compressive strengths were measured up to age 28 days. The microstructure and morphology of reaction products were investigated using scanning electron microscopy. X-ray fluorescence spectrometry was used to determine the chemical analyses of raw materials and x-ray diffraction was used to investigate the crystalline reaction products. Pastes incorporating a 60 wt% solution of phosphoric acid and a solution-to-powder ratio one of 1.0 exhibited the highest performance. AE fly ash pastes, loaded with 10 wt% soda lime glass, and activated with 60 wt% phosphoric acid solution and a solution-to-powder ratio of 1.0 reached the highest 28-day compressive strength with 30 MPa.

Subject Keywords

Fly ash., Coal ash., Waste products., Phosphate ceramics., Portland cement

URI

http://etd.lib.metu.edu.tr/upload/12618009/index.pdf
https://hdl.handle.net/11511/24029

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

M. Mahyar, “Room-temperature phosphate ceramics made with Afşin-Elbistan fly ash /,” M.S. - Master of Science, Middle East Technical University, 2014.