## 3 Results and Discussion
### Microscopic Test  
The SEM images of the geopolymer under different ratios of water to slag powder at 28 d are shown in Figures 12-14. As shown in Figure 12, at a \(100\times\) magnification, when the ratio of water to slag powder was small, the surface of the geopolymer was dense. The alkali activator promoted the hydration process of the glass phase material in the slag geopolymer, resulting in a large number of gel particles arranged closely, so the material structure in the SEM images had small pores. When the ratio of water to slag powder increased, the increase in water content promoted the hydration and dissolution reaction of the slag in the early stage of reaction, but the pore size of the structure increased, resulting in a decrease in the density of the geopolymer. The SEM images of the material at a \(500\times\) magnification are shown in Figure 13. The image shows that as the water content increased, the shrinkage of the geopolymer material also increased, and the number and width of microcracks gradually increased. As shown in Figure 14, at a \(2000\times\) magnification, when the ratio of water to slag powder was 0.24, there was a large number of flake calcium hydroxide crystals and granular geopolymer gels on the surface. As the ratio of water to slag powder gradually increased, the flake sodium hydroxide crystal gradually decreased. The main reaction product of the geopolymer with the ratio of water to slag powder of 0.28 and 0.30 was gel material. Due to the corresponding increase in the shrinkage reaction of the geopolymer, the structural  
Figure 12: SEM images of geopolymer at different ratios of water to slag powder (\(200\) μm). (**a**) Ratio of water to slag powder 0.24; (**b**) Ratio of water to slag powder 0.26; (**c**) Ratio of water to slag powder 0.28; (**d**) Ratio of water to slag powder 0.30.  
density decreased; moreover, the ratio of the water to slag powder of 0.30 cause the geopolymer material to have a lower density. Figure 14: SEM images of geopolymer at different ratios of water to slag powder (10 \(\upmu\)m). (**a**) Ratio of water to slag powder 0.24; (**b**) Ratio of water to slag powder 0.26; (**c**) Ratio of water to slag powder 0.28; (**d**) Ratio of water to slag powder 0.30. Figure 13: SEM images of geopolymer at different ratios of water to slag powder (40 \(\upmu\)m). (**a**) Ratio of water to slag powder 0.24; (**b**) Ratio of water to slag powder 0.26; (**c**) Ratio of water to slag powder 0.28; (**d**) Ratio of water to slag powder 0.30. In order to study the morphology of geopolymer reaction products, EDS analysis was conducted on micro regions of a 28 d geopolymer under the five ratios of water to slag powder. The SEM images and EDS spectra of micro regions with ratios of water to slag powder of 0.26, 0.28, and 0.30 under a 2000\(\times\) magnification are shown in Figures 15-17. It could be seen from the SEM image that many gels was generated in the slag geopolymer, and the main product was the C-S-H gel. There were micro cracks on the surface of the slag geopolymer, and as the ratio of water to slag powder increased, the shrinkage of the geopolymer increased. Due to a decrease in the density of the geopolymer, the degree of surface porosity increased. According to the EDS spectrum, the main elements in the hydration products of slag-based geopolymer included Ca, Si, Al, Na, Mg, C, O, etc. Due to the existence of the Al element, some Si element in the C-S-H gel was replaced to form the C-A-S-H gel. The mass percentages of the main elements in the polymerization reactants with the five ratios of water to slag powder are shown in Figure 18. As the ratio of water to slag powder increased, the mass fractions of various elements showed a decreasing trend overall, mainly due to the dilution effect caused by increasing the water volume. Under the action of alkaline activator, the increase in water would accelerate the hydration of glass substances in a slag-based geopolymer powder, accelerating the reaction.