Abstract:
The purpose of this research aims to study the effect of curing temperature and concentration of sodium hydroxide (NaOH) on the mechanical properties of fly ash geopolymers. The source of fly ash is from the paper factory of Double A (1991) Public Company Limited, Prachinburi Province. The concentrations of sodium hydroxide solutions are 5, 10 and 15 molar. The geopolymer specimens having a size 50×50×50 mm are cured in room temperature for 7 days, afterthat are cured at 100, 200, 500, 750 and 1000 °C for 3 h. The testing mechanical properties consists of density compressive strength and water absorption. The study results found that higher temperature effect on pale color of the sample and lesser weight of samples. Some specimens have white efflorescence caused by sodium hydroxide residues. The curing temperature in the range of 200 750 ℃ have increment of the compressive strength. The specimens of 10 molar sodium hydroxide solution curing at 200 500 and 750 ℃ have the highest compressive strength. The higher curing temperature results on the higher the water absorption. The specime of 5 molar sodium hydroxide solution has higher water absorption than that of other concentrations. The specimen having a concentration of 10 molar sodium hydroxide solution curing at 200 500 and 750 ℃ has density and compressive strength similar to properties of lightweight bricks.