## 3 Results and Discussions
### Fresh State and Rheological Characteristics
#### 3.1.1 Slump Flow, Viscosity and Setting Times
The viscosity of the mixes increased with the decrease in the slump flow at all time intervals, as represented by the equations noted in Figure 5. These correlation equations reveal that the elapsed time did not change the linear relation between viscosity and slump flow; however, the rate of decrease as indicated by the slope of the graphs decreased with respect to time. The control cement-based mortar (FP\({}_{\text{C}}\)M) produced the highest slump flow spread/ relative slump of 480 mm/22.0 and the lowest viscosity of 1.8 Pa.s at 0 min after mixing. This control mix exhibited the highest initial (474 min) and final (522 min) setting times. Almost no change in slump flow spread/relative slump nor viscosity was observed with time in the control mortar produced with a high volume of fly ash (FA). The plastic viscosity values of all the AAM mixes were found to be higher than FP\({}_{\text{C}}\)M.  
The type of reagents influenced the slump flow, viscosity and setting times of AAM mixes. The mixes with reagent one having a higher SiO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\) ratio (as noted in Table 3) exhibited higher viscosity with a lower slump flow/relative slump and lower setting times than their counterparts incorporating reagent two and the control cement-based mortar. This can be attributed to the higher alkalinity of the sodium metasilicate and silicate content present in reagent one, which facilitated the faster dissolution of aluminum and silicate ions from the SCMs, leading to the quicker formation of reaction products. A similar observation was reported in an earlier study where the silicates present in the alkaline solutions reacted rapidly with aluminates released from fly ash dissolution forming alkaline  
Figure 4: (a) Normalized viscosity with time; (b) Normalized slump flow spread with time. Figure 5: Viscosity versus slump flow. aluminosilicate binding gels. These gels formed in the initial phases facilitate the pastes' setting and hardening, leading to higher viscosities and lower slump flow spread with time [19; 33]. Lower reductions in slump flow spread at 30 and 60 min of post-mixing were also evident for mortars with reagent two, as shown in Figure 4b. A reduction in the slump flow/relative slump from 250 to 180 mm (up to a 28% reduction))/5.2 to 2.2 for mortars with reagent two was observed compared to the reduction from 245 to 105 mm (up to 57% reduction)/5.0 to 0.1 for mortars with reagent one at 30 min (Table 4). For instance, the mortar mixed with reagent one, mix CFSM1, almost lost its entire workability at 30 min, exhibiting a decrease in slump flow spread/relative slump flow spread from 245 mm/5.0 at 0 min to 105.0 mm/0.1. The water content and liquid to solid (L/S) ratio are also essential factors in producing mixes with higher slump flow and lower viscosity, as indicated in Figure 5. The presence of a higher water content and higher L/S ratios resulted in higher slump flow spread diameters/relative slump, higher setting times and lower viscosity values for mixes with reagent two compared to their reagent one counterparts, as can be seen from Tables 2 and 3. Similar behavior was observed in previous studies on the two-part alkali-activated fly ash and slag mortars with the increase in L/S ratios [9; 34]. This was attributed to the decreased interparticle frictional forces and increased particle spacing/thickness of the fluid film from the higher amount of suspended fluid in the suspension, which eventually led to a decrease in yield stress and plastic viscosity. Moreover, an increased water content also reduced the concentration of the alkali ions in the solution. This reduction in the alkali ion concentration resulted in an activation solution with lower viscosity, reducing yield stress and plastic viscosity values. An increase in viscosity was observed with the reduction in slump flow spread/relative slump over time.