The role of active silica and alumina in geopolymerization


  • Van Quang Le* Vietnam Institute for Building Materials
  • Quang Minh Do Ho Chi Minh city University of Technology
  • Minh Duc Hoang Vietnam Institute for Building Science and Technology
  • Hoc Thang Nguyen Ho Chi Minh city University of Food Industry


In this study, the alkaline solutions (NaOH) with concentrations from 1M to 18M, red mud (RM) and silica fume (SF) were used as reactors in geopolymer reactions. RM contains 7.40% SiO2 and 13.65% Al2O3 and SF has 94.50% SiO2, but only the active oxides can participate in the geopolymer reactions. The activity of the oxides was investigated by determining the compressive strength of the samples under different curing conditions. The characteristics of the geopolymer samples were determined by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA)/differential thermal analysis (DTA) and nuclear magnetic resonance analysis (NMR). The experimental results indicate that active silica mainly exists in SF. In the structure of geopolymers, the silicon can bond directly with each other (Si-Si) or be linked through ‘bridging’ oxygen (Si-O-Si) to form independent polymer chains, while aluminium atoms can only replace the silicon atoms in Si-O-Si polymer chains to form Si-O-Al instead.


active silica, alumina, geopolymer, red mud, silica fume


Classification number





Received 23 January 2018; accepted 18 April 2018

How to Cite

Van Quang Le, Quang Minh Do, Minh Duc Hoang, & Hoc Thang Nguyen. (2018). The role of active silica and alumina in geopolymerization. Vietnam Journal of Science, Technology and Engineering, 60(2), 16-23.



Physical Sciences