Effect of Silica to Alumina Ratio on the Compressive Strength of Class C Fly Ash-Based Geopolymers

Abstract:

This study investigated the effect of silica to alumina ratio on the compressive strength of geopolymer. The high calcium fly ash (Class C, ASTM 618) wastes from Mae Moh Thailand power plant, which is SiO₂ (30.97%) and Al₂O₃ (17.16%)-rich materials was employed as the main solid part to prepare geopolymers, apart from kaolinite. The combination of sodium hydroxide (NaOH), sodium silicate (Na₂SiO₃) solution, and distilled water as 1:1:4 mass ratios were used as the liquid activator. The curing temperature in the oven was fixed at 75oC and varied curing time for 24, 48, 72 and 96 hours. Further curing was done at room temperature for 28 days before characterizations. XRD study of synthesized geopolymers showed a hump of not well-defined peaks and some major peaks of quartz, and unreacted kaolinite indicating the incomplete geopolymerization reaction. Infrared study showed the Al-O-Si and Si-O-Si bonds in all geopolymers samples. The compressive strength of geopolymer increased from 32 to 40 MPa when the ratio of SiO₂ : Al₂O₃ was increased from 2.60 to 2.65. However, the compressive strength was decreased after increasing the SiO₂ : Al₂O₃ ratio from 2.65 to 3.0. The highest compressive strength was found when the SiO₂ : Al₂O₃ ratio was 2.65 with the curing condition at 75oC for 96 h which the samples also possessed high density.

• Periodical: Key Engineering Materials (Volume 659)
• Pages: 80-84
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.659.80
• Online since: August 2015
• Authors: Patthamaporn Timakul*, Kanyarat Thanaphatwetphisit, Pavadee Aungkavattana
• Keywords: Class C Fly Ash, Compressive Strength, Geopolymer, Silica to Alumina Ratio

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