## 3 Results
### Effect of Curing Age (Days) on the Morphology  
Figure 7 depicts the SEM micrographs of GGBFS and samples cured at ambient temperature for different days. The morphology of GGBFS is non-homogeneous and distinctly porous [44]. Analyses of samples with different curing days show very different surface morphologies. The specimen micrograph with 7 days curing period showed a high quantity of unreacted particles, heterogeneous microstructure, and micro cracks. Similarly to the specimen micrograph cured for a period of 14 days, it also showed a presence of unreacted particles and micro cracks. This indicates a lower dissolution rate of GGBFS in the mix that caused incomplete activation process and lower UCS in the early stages of alkaline activation process. This could possibly be related to the high amount of silica that hindered the movement of reaction particles in the system, consequently, organic and inorganic phases improved polymerization reactions when reacted separately [43]. Organic and inorganic phase barriers became cracks, resulting in a weak connection of these two phases [45]. Also, much of alkaline solution used to achieve required workability may have evaporated, hence resulting in cracks as it formed pathways when escaping from the synthesized alkaline activated material [44; 45; 46]. On the other hand, fewer unreacted products and dense microstructure can be seen in a specimen cured for a period of 28 days. This indicates a higher dissolution rate of aluminosilicates in the alkaline activation mix and formation of more hydration products responsible for better mechanical properties [8]. The specimens cured for a period of 56 and 90 days showed an insignificant number of unreacted particles, traces of incomplete activation, coherent and much denser microstructure [47]. This clearly indicates the existence of greater hydration products due to a higher dissolution rate of GGBFS particles that optimized the formation of C-A-S-H and N-A-S-H products leading to compact microstructure and better mechanical properties. [PERSON] et al. also reported the same findings [39]. Moreover, the unreacted aggregates acted as inert aggregates, limiting the shrinkage of the samples during the hardening period, and reducing the number of cracks [47].  
Figure 6: XRD pattern of samples (M = magnetite, Q = quartz, H = hydrocalumite, CSH = calcium silicate hydrate, CAH = calcium aluminate hydrate, C = calcite, E = ettringite).  
Table 4 shows the effect of water absorption and open porosity of the sample after 90 days of curing. The sample was immersed in deionised water for 30 days and the results revealed a low water absorption percentage that could be attributed to better alkali activated GGBFS composite within the matrix [15]. This was also corroborated by XRD and SEM analysis. In addition, the C-A-S-H phases within the alkali activated GGBFS composite matrix are highly water-bound [8]. The sample had a lower volume of permeable pores as compared to the 10% permeable limit suggested by [PERSON] [48]. The low volume of permeable pores shows that the sample has fewer capillary pores and air voids, which confirms low water absorption, better UCS and durability [49].  
Figure 7: SEM micrographs of GGBFS and samples cured at ambient temperature for different days.