Effect of lignite fly ash and rice husk ash ratios on physical properties of lightweight porous geopolymers fabricated by pore-forming agent method

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Reungruthai Sirirak
Thanapong Lertcumfu
Arrak Klinbumrung
Nattapong Damrongwiriyanupap
Anurak Prasatkhetragarn


In this study, the porous lightweight geopolymer used lignite fly ash (FA) and rice husk ash (RHA) derived from the local source. The prepared geopolymer slurry was a mixture of FA, RHA, and alkaline solution activators which consisted of Na2 SiO3 and 10 M of NaOH solution. RHA was applied to replace FA content in the 10-50% ratio by weight. The ratio of solid (fly ash and rice husk ash) and liquid (Na2 SiO3 and NaOH) is 0.6, while the ratio of Na2 SiO3 and NaOH is 3. Powder of sponge was employed to create the porous geopolymer materials in 0.5 % by weight. The fresh slurry was poured into cube plastic molds for porous geopolymer casting. Then, the porous geopolymer was cured at 60 oC for 48 hours and 7 days at room temperature. After sintering at 700 oC for 2 hours, the specimens were examined. The micrographs of surface characteristics show an enlarged pore size with increasing RHA amount, corresponding to the % shrinkage/expansion of the specimens. The XRD patterns shows an increase in quartz content by increasing RHA. The water absorption increases with increasing the amount of RHA, related to the porosity. It was found that the amount of RHA can improve the physical properties of geopolymer materials which increases the porosity value when increasing the amount of RHA.

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