Journal Article

Heat-tTreated Fly Ash-Calcium Hydroxide Geopolymers: Enhancing Mechanical and Morphological Performances

Jia-Ni, L., Yu-Xin, Y., Hoe-Woon, T., Yong-Jie, H., Nabiałek, M., Abdullah, M.M.Al Bakri, Yun-Ming, L., Cheng-Yong, H., Shee-Ween, O.

2025

Overview

The combined effect of calcium hydroxide (CH) and heat treatment on mechanical and morphological performances of geopolymer remains underexplored, presenting a critical gap in heat-resistance geopolymer research. This paper investigates the effect of CH (0, 2, and 4 wt.%) and elevated temperatures (200–1000°C) on the mechanical and morphological properties of fly ash (FA) geopolymers. The addition of 2 wt.% of CH enhanced compressive strength (35.8 MPa), attributed to coexistence of N-A-S-H and C-S-H, which enhanced structural interlocking and reinforced the compactness. At 200°C, FA geopolymers developed a robust structure due to further geopolymerization; however, structural deterioration occurred at 800–1000°C due to the melting of geopolymer gels and further phase transformation. This study provides guidelines for synthesizing sustainable and thermally resistant construction binders, particularly for applications in industrial flooring and thermal insulation structural walls.