Self-Fluxing Mechanism in Geopolymerization for Low-Sintering Temperature of Ceramic

Abstract

Kaolin, theoretically known as having low reactivity during geopolymerization, was used as a source of aluminosilicate materials in this study. Due to this concern, it is challenging to directly produce kaolin geopolymers without pre-treatment. The addition of ground granulated blast furnace slag (GGBS) accelerated the geopolymerization process. Kaolin–GGBS geopolymer ceramic was prepared at a low sintering temperature due to the reaction of the chemical composition during the initial stage of geopolymerization. The objective of this work was to study the influence of the chemical composition towards sintering temperature of sintered kaolin–GGBS geopolymer. Kaolin–GGBS geopolymer was prepared with a ratio of solid to liquid 2:1 and cured at 60 °C for 14 days. The cured geopolymer was sintered at different temperatures: 800, 900, 1000, and 1100 °C. Sintering at 900 °C resulted in the highest compressive strength due to the formation of densified microstructure, while higher sintering temperature led to the formation of interconnected pores. The difference in the X-ray absorption near edge structure (XANES) spectra was related to the phases obtained from the X-ray diffraction analysis, such as akermanite and anothite. Thermal analysis indicated the stability of sintered kaolin–GGBS geopolymer when exposed to 1100 °C, proving that kaolin can be directly used without heat treatment in geopolymers. The geopolymerization process facilitates the stability of cured samples when directly sintered, as well as plays a significant role as a self-fluxing agent to reduce the sintering temperature when producing sintered kaolin–GGBS geopolymers.

Eco-Friendly Coal Gangue and/or Metakaolin-Based Lightweight Geopolymer with the Addition of Waste Glass

“…The quantitative analysis of coal-gangue-based geopolymer foams did not detect the kaolinite phase, which confirmed that during treatment the inner hydroxyl structure of kaolinite was reduced, and as a result, an amorphous substance material was formed [75]. Qualitative analysis of geopolymer (Table 6) showed new phases, which were albite and C-S-H, proving the reaction between raw materials and alkaline activator during geopolymerisation [76]. Similarly, results also revealed the mullite phase in all foams, whereas it was identified only in metakaolin from among raw materials.…”

Properties and Applications of Geopolymer Composites: A Review Study of Mechanical and Microstructural Properties

“…Different researchers have studied the DSC analysis of geopolymer concrete [103][104][105][106][107]. Jamil, N. H. et al [107] showed the geopolymer's range of thermograms (exothermal up) (Figure 24), where the geopolymer demonstrates some peaks in the matrix.…”

“…Different researchers have studied the DSC analysis of geopolymer concrete [103][104][105][106][107]. Jamil, N. H. et al [107] showed the geopolymer's range of thermograms (exothermal up) (Figure 24), where the geopolymer demonstrates some peaks in the matrix. Figure 25 depicts the differential scanning calorimetry (DSC) thermograms of geopolymer paste after 28 days, which are similar to the results reported in previous works [101].…”