IR spectral similarity studies of geothermal silica-bentonite based geopolymer

Abstract

The geopolymer structures are formed through polymerization of silicate and aluminate species. The resulted structure is predicted to be similar with zeolite. In this study, geopolymer samples were made from mix powder of geothermal silica and bentonite, then activated with sodium hydroxide and sodium silicate. The effect of silica content, NaOH molarity and curing temperature effect were investigated on geopolymer IR spectra and compared with 3A zeolite IR spectra. Pearson correlation value (r) and spectral similarity correlation (Corr) were used to assess spectra similarity between geopolymer samples and zeolite. The development of geopolymer bond and microstructure of samples were then investigated by FTIR technique. IR spectra of geopolymer samples show that Si-O-Al absorption bands are formed around 900-1300 cm-1 and 400-800 cm-1. The optimum of silica contents, NaOH molarity and curing temperature obtained from the experiment were 140 grams, 10 M and 80°C with Corr value of 922 and compressive strength of 7,59 MPa. Corr value is proven to have relation with material strength. Higher Corr value is identified to have higher aluminosilicate species which contributes to higher compressive strength.