Microstructural Impact of Alkaline Binders in Self-compacting Geopolymer Concrete Incorporating Sustainable Environmental Materials

The impact of alkaline binder ratios on the microstructural properties of self-compacting geopolymer concrete (SCGC) has been investigated in this paper. Five SCGC mix designs were tested with varied alkaline binder ratios between 0.40 and 0.60, employing 50% FA and 50% GGBS as binders. The binder is introduced with a 14 M NaOH solution and superplasticizer at a rate of 9 kg/m³ together with additional water at a rate of 54 kg/m³. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDAX) are used to evaluate the microstructure. The XRD analysis revealed that binder ratios of 0.50, 0.55, and 0.60 favor gel formation. In contrast, the lower binder ratios of 0.40 and 0.45 indicate a more pronounced crystalline phase and less gel formation and thus incomplete geopolymerization. The SEM and EDAX analyses showed that the particles in the SCGC are irregular and angular and have a large surface area, resulting in strong interfacial bonding and improved material performance. From the results obtained, an alkaline binder ratio of 0.50 provides an optimal balance between gel formation, microstructure uniformity, and a residual crystalline phase. The current research thus sheds light on the importance of the alkaline binder ratio to improve the properties of SCGC for use in sustainable construction.