Effect of Calcination Temperature on Strength and Microstructure of Synthetic Geopolymer from Water Treatment Residue

This research studied the effect of calcination temperature on strength and microstructure of synthetic geopolymer. Water treatment residue (WTR) was calcined in an electric furnace at the firing temperature of 600, 800 and 900°c for 1and 2 hours. The treated WTR was then reacted with sodium hydroxide solution using the ratio of Na2O:SiO2 equals to 0.25. Unconfined compressive strength of the synthetic geopolymer was determined at the age of 7, 14, and 28 days. Experimental results showed that Si2O, Al2O3, and Fe2O3 were the major chemical components of calcined WTR and were presented at 53.70%, 30.10%, 9.56%, respectively. X-ray Diffraction (XRD) analysis of non-calcined WTR appeares the peaks of halloysite (Al2Si2O5(OH)4), muscovite (KAl3Si3O10(OH)2) and quartz (SiO2). The maximum value of strength was obtained from the synthetic geopolymer prepared from WTR calcined at 800 °c for 2 hour and gave a 28-day strength of 103kg/cm2. In addition, strength development was not observed from sample prepared from WTR without calcination.