## 3 Fresh and Hardened Properties of GPC
### Setting Time  
Several researchers investigated the effect of molarity, silicates/hydroxide ratio, binder content, and superplasticizer content on setting time. The setting time of geopolymer decreases with an increase in molarity of NaOH from 10M to 16M due to the faster dissolution rate of aluminosilicates that enhances the geopolymerization process. [PERSON] et al. [116] observed the setting time behavior of FA-based geopolymer with 100% FA, Fly Ash-Silica fume (FAS) mixed geopolymer with 50% FA and 50% silica fume, and the Fly Ash-Silica fume-Furnace Slag (FASS)-based geopolymer containing 50% FA, 35% GGBFS, and 15% silica fume. It was found that with rise in NaOH molarity, the final setting time of both FAS and FASS geopolymer mix linearly increases (Figure 10). Contrarily, the FA mix showed linear decline with the rise in molarity in the initial setting time, while remain constant in the case of final setting time. The increase in setting time might be due to effect of composition of silica fume added or because of slower rate of geopolymerization process [117; 118; 119]. Several researchers [120; 105] have concluded that activator to FA ratio and Na\({}_{2}\)SiO\({}_{3}\)/NaOH ratio have no significant impact on the setting time of FA-based geopolymer mortar. However, it is clear that the setting time of FA-based geopolymer mortar decreases with increasing molarity [120; 121]. While studying the effect of superplasticizer on workability, [PERSON] et al. [110] investigated the setting time effect of ultrafine slag-based GPC with superplasticizers having both NaOH activator and blend of NaOH and Na\({}_{2}\)SiO\({}_{3}\). It has been  
Figure 9: Factors effecting workability. (**a**) Effect of water to ash ratio on flow. (**b**) Effect of NaOH concentration on flow, adopted from [113]; Elsevier, 2009.  
confirmed that the NaOH activator considerably delays the setting time as compared to the geopolymer containing a blend of both NaOH and Na\({}_{2}\)SiO\({}_{3}\). This might be due to the instability of superplasticizers in a high alkaline environment. In addition, the effect of micro-encapsulated phase change materials (MPCM) on setting time of FA and slag GPC was studied by [PERSON] et al. [122]. It was found that the initial setting time increases and final setting time decreases with decreasing concentration of MPCM and depends on samples viscosities, the absorption capacity of microcapsules and the latent heat. The behavior of setting time on GGBFS content was studied by [PERSON] et al. [102]. It was found that with the increase in the GGBFS content, the initial and final setting time decreases due to an increase in viscosity. In addition, the inclusion of additives in GPC accelerates the setting time depending on the type of additive added.  
From above discussion, it is determined that, in general, the setting time decreases with an increase in molarity. However, the inclusion of superplasticizers in GPC reduces the workability which in turn  
Figure 10: Effect of NaOH molarity on setting time of FA, FAS, and FASS-based geopolymer. (**a**) Effect on initial setting time, (**b**) effect on final setting time, adopted from [116]; Elsevier, 2018.  
causes an increment in setting time (Figure 11). This increment could provide an economical solution during formwork when GPC is used practically.