Volume 31, No. 04, Month OCTOBER, Year 2021, Pages 711 - 722

Factors of fgd-gypsum replacement and alkaline solution ratio on compressive strength and microstructure of fly ash geopolymer

Chudapak Detphan, Tanakorn Phoongernkham, Satakhun Detphan, Khattiya Chompoovong, Sakonwan Hanjitsuwan, Prinya Chindaprasirt

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This research aims to study the factors of FGD-gypsum replacement and alkaline solution ratio on the compressive strength and microstructure of fly ash (FA) geopolymer. FGD was used to replace FA at the ratio of 0%, 10%, 20%, and 30% by weight of the binder. The liquid activators were sodium silicate (Na2SiO3) and 10 molar of sodium hydroxide (NaOH) solutions. The differences in Na2SiO3/NaOH ratios at 1.0, 1.5, 2.0, and 2.5 were investigated. The liquid/binder ratio of 0.60 cured at ambient temperature was used in all mixing. Test results showed that the setting time of FA geopolymer mortar tended to decrease with the increasing of FGD replacement and the Na2SiO3/NaOH ratio. Besides, XRD and SEM results demonstrated that they corresponded to compressive strength results of FA geopolymer. According to the above test results, it can be concluded that using 10%FGD activated with Na2SiO3/NaOH ratios at 1.0 and 1.5 were the optimum mixing ratio to develop the compressive strength of FA geopolymer mortar incorporated with FGD-gypsum.


Fly ash Geopolymer; FGD-gymsum; Alkaline Solution Ratio; Mechanical Properties; Microstructure


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