## 3 Results and Discussion
### Compressive Strength and Linear Expansion of GPC Samples  
In essence, the findings indicate that, as the curing time was extended, \(F\) and \(\Delta\)/\(l_{0}\) increased with gradients that vary from the curing times of 1 day to 14, 30 and 60 days. For GPC samples that were cured at 60 \({}^{\circ}\)C, at atmospheric pressure, the highest \(F\) of 15.01 MPa was obtained by R10, while the highest \(\Delta\)/\(l_{0}\) of 0.9985% was obtained by R25. As the curing time increased from 1 day to 60 days, \(F\) and \(\Delta\)/\(l_{0}\) of each formulation increased as follows:  
* R10: \(F\) increased from 4.71 to 15.01 MPa, and \(\Delta\)/\(l_{0}\) increased from 0.3508% to 0.5213%, as per Figure 7.
* R15: \(F\) increased from 6.01 to 10.49 MPa, and \(\Delta\)/\(l_{0}\) increased from 0.1432% to 0.3101%, as per Figure 8.  
Figure 5: Plastic viscosity (\(PV\)) of GPC slurry at varying concentrations of \(R\)-additive. Figure 6: Yield point (\(YP\)) of GPC slurry at varying concentrations of \(R\)-additive. * R20: F increased from 5.14 to 10.82 MPa, and \(\Delta\)/\(l_{0}\) increased from 0.7625% to 0.9903%, as per Figure 9.
* R25: F increased from 1.72 to 10.33 MPa, and \(\Delta\)/\(l_{0}\) increased from 0.7625% to 0.9985%, as per Figure 10.  
Figure 8: \(F\) and \(\Delta\)/\(l_{0}\), at varying curing times, of GPC samples with R15 formulation that were cured at 60 \({}^{\circ}\)C, at atmospheric pressure. Figure 7: Compressive strength (\(F\)) and linear expansion (\(\Delta\)/\(l_{0}\)), at varying curing times, of GPC samples with R10 formulation that were cured at 60 \({}^{\circ}\)C, at atmospheric pressure. The impacts of increasing the concentration of \(R\)-additive on \(F\) and \(\Delta\)/\(l_{0}\) are elucidated in Figures 11-14 for samples that were cured for 1, 14, 30 and 60 days, respectively. Principally, as the concentration of \(R\)-additive was raised, \(F\) decreased with gradients that vary from the concentrations of \(R\)-additive of 10% to 15%, 20% and 25%. When the concentration of \(R\)-additive was increased from 10% to 15%, \(F\) increased for samples that were cured for 1 day, as shown in Figure 11; exhibited a trivial change for samples that were cured for 14 days, as shown in Figure 12; and, conversely, declined with a high gradient for samples that were cured for 30 and 60 days, as shown in Figures 12 and 13, respectively. The findings are in agreement with [PERSON] et al. [46] and [PERSON] et al. [47], who highlighted that the concentration of \(R\)-additive was increased from 10% to 15%, 20% and 25%, respectively. Figure 10: \(F\) and \(\Delta\)/\(l_{0}\), at varying curing times, of GPC samples with R25 formulation that were cured at 60 \({}^{\circ}\)C, at atmospheric pressure. Figure 9: \(F\) and \(\Delta\)/\(l_{0}\), at varying curing times, of GPC samples with R20 formulation that were cured at 60 \({}^{\circ}\)C, at atmospheric pressure. styrene-butadiene lowers the pH of the alkaline-activator solution and, in consequence, that of the geopolymer matrix, thus impeding the development of compressive strength. Accordingly, the addition of styrene-butadiene at higher concentrations led to further reduction in the pH of the geopolymer matrix and, as a consequence, further reduction in the compressive strength. Furthermore, [PERSON] et al. [47] suggested that styrene-butadiene hinders the reaction between the raw material and alkaline-activator solution as it covers the interfaces of the raw material. Moreover, the addition of \(R\)-additive as an expandable additive led to the increase in bulk volume of the internal cement as explained in [PERSON] et al. [58]. Furthermore, based on [PERSON] [59], it can be added that higher concentrations of \(R\)-additive resulted in further reduction of \(F\) by virtue of the reduction in density. \(R\)-additive is an oil-swellable particle, and hence, as explained in [PERSON] et al.