Speaker
Description
Alkali-activated fly ash-based materials have attracted considerable attention as sustainable alternative binders due to their ability to partially replace ordinary Portland cement while exhibiting favorable mechanical properties, durability, and resistance to aggressive environmental conditions. Furthermore, the investigation of alkali-activated materials at temperatures exceeding 1000 °C is essential for assessing their thermal stability, phase evolution, and microstructural transformations, thereby providing valuable insights into their potential application as high-performance binders and refractory materials under extreme thermal conditions. In this study, two systems were prepared: pure fly ash (FA) and a blend of wood ash (WA) and fly ash (10 wt.% WA and 90 wt.% FA), which were subsequently subjected to alkali activation to enhance precursor reactivity through their calcium- and alkali-rich composition. The high-temperature behavior of fly ash and fly ash–wood ash alkali activated materials was evaluated following thermal treatment at 1000, 1100, and 1200 °C. X-ray diffraction analysis revealed the formation of thermally stable crystalline phases, including nepheline, quartz, and gehlenite in both systems, while albite was additionally identified in the FA–WA samples. Both alkali activated systems maintained structural stability up to 1100 °C; however, significant degradation and collapse of the formed structural network were observed at 1200 °C. Scanning electron microscopy demonstrated progressive densification, reduced porosity, and the transformation of the initially amorphous geopolymeric matrix into a ceramic-like structure with increasing temperature. These findings highlight the influence of wood ash incorporation on phase development and microstructural evolution, as well as the high-temperature performance of alkali-activated fly ash-based materials.
Keywords: Fly ash; Wood ash; Alkali-activated materials; High-temperature treatment; Thermal stability; Microstructural evolution
References:
Provis, J. L. Geopolymers and other alkali-activated materials: Why, how, and what? Materials and Structures 2014, 47(1–2), 11–25.
Kljajević, LJ, Marković, S., Mladenović Nikolić, N., Nenadović, M., Mirković, M., Pavlović, V., Bučevac, D., Nenadović, S. Tailoring fly ash geopolymer ceramics: The influence of alkaline activation and thermal treatment on structure and phase transformation, Ceramics International 2026, 52(5), 6342-6355, https://doi.org/10.1016/j.ceramint.2025.12.390