Study of Leaching of Lignite Fly Ash and Strength of Fly Ash Based-Geopolymer

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Ubolluk Rattanasak
Wichian Chalee
Prinya Chindaprasirt


A study was conducted on the leaching of the SiO2 and Al2O3 of lignite fly ash in NaOHsolution and its effect on the strength of geopolymer. The fly ash samples were suspended in thedifferent NaOH concentration solution. The leachates with different leaching time intervals, wereanalysed in term of silica and alumina leached. In addition, the strength of the geopolymer was alsotested. The results revealed that the solubility of the fly ash depended on the concentration ofNaOH and the leaching time. High compressive strength was obtained with a moderate concentrationof NaOH (10M) and a selected leaching time of 10 minutes. A geopolymer with relatively highstrength of up to 65 MPa is obtained and is comparable to the high strength mortar and concretemade from ordinary Portland cement type I.

Keywords : Geopolymer / Fly Ash / Leaching / Solubility / Sodium Hydroxide / CompressiveStrength

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Author Biographies

Ubolluk Rattanasak, Burapha University, Muang, Chonburi 20131

Lecturer, Department of Chemistry.

Wichian Chalee, Burapha University, Muang, Chonburi 20131

Lecturer, Department of Civil Engineering.

Prinya Chindaprasirt, Khon Kaen University, Muang, Khon Kaen 40002

Associate Professor, Department of Civil Engineering.