Evaluation on Formation of Aluminosilicate Network in Ternary-Blended Geopolymer Using Infrared Spectroscopy

Abstract

This study used an optimized mixture of red mud (RM), rice husk ash (RHA), diatomaceous earth (DE), and water glass solution (WGS) with silica modulus of 2.5 to produce geopolymer-based material. The geopolymer product was tested engineering properties which are in good agreement of ASTM requirements for building materials. For microstructure, the geopolymer samples were characterized by using Fourier-transform infrared spectroscopy (FTIR) and focused on evaluation on formation of aluminosilicate network in the ternary-blended geopolymer. The results showed that tetra-silicates or acid silicic (Si (OH)4 or H4SiO4) dissolved and reacted with the iron oxide (Fe2O3) in RM and DE to form the oligomer precursors of sialate-O-Si-O-Al-O-, sialate-siloxo-O-Si-O-Al-O-Si-O-, sialate-disiloxo-O-Si-O-Al-O-Si-O-Si-O-, tetra-silicate [SiO4]4-, and tetra-aluminate [AlO4]4-. The formation of sodium alumino-silicate iron hydroxide polymeric network were easily detected by vibrational modes of –T–O–T– and –T–O–Na units (T refers to tetrahedral such as that of Si or Al) and of –OH and H–O–H. As well as, there were appearances of the membered ring or chain structural units of geopolymers.