Table 3.

SEM Morphology and EDX analysis of FA-based geopolymer microstructures in relation to alkali concentration and curing temperature. Reprinted with permission from Ref. [50]. Copyright 2016 Elsevier.

Process Parameters		SEM Analysis	EDS Analysis
Alkali molarity	Curing temperature	Morphological features	Si/Al ratio	Na/Al ratio
6 M	27 °C	Spherical particles with partially reacted surface. Few Na-rich elongated grains (<5 μm size). Open pores throughout the matrix.	1.3–1.7	0.2–3.0
6 M	45 °C	More reacted surface with reaction product. Numerous Na-rich elongated grains (5–10 μm size). Open pores and few fibrous grains.	1.3–1.7	0.2–4.0
6 M	60 °C	Surface fully altered into reaction product. Numerous Na-rich fibrous grains (up to 20 μm size). Lower pores amount.	1.3–1.6	0.4–5.0
8 M	27 °C	Well reacted surface with reaction products. Al-rich short prismatic grains (2 μm size) occurring in clusters on broken cenosphere. Na-rich dense gel.	1.2–2.1	0.5–3.5
8 M	45 °C	Fully reacted particles enveloped with reaction product. Numerous Na rich fibrous grains (up to 20 μm size). Na-rich dense gel.	1.3–2.1	0.3–3.5
8 M	60 °C	Fully reacted particles, reaction product on the crust. Numerous Na-rich fibrous grains larger than the fibers obtained at 45 °C. Low porosity and compact structure.	1.3–2.1	0.15–3.5
10 M	27 °C	Fully reacted particles covered with reaction product. Al-rich short prismatic grains (2 μm size) occurring in clusters. Na-rich dense gel.	0.6–2.3	0.15–3.5
10 M	45 °C	Fully reacted particles covered with reaction product. Fibrous grains (up to 50 μm size). Na-rich dense gel.	1.1–3.0	0.12–3.8
10 M	60 °C	Fully reacted FA particles. Na-rich gel particles are fusing together to form a dense structure. Si-rich very fine particles (0.5–2 μm size).	1.2–4.0	0.2–3.5