## 6 Geopolymer OPC Concrete
\begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Parameters** & **Advantage** & **Disadvantage** & **Remarks** \\ \hline \multirow{4}{*}{Activator Molarity} & \multirow{4}{*}{Increase in molarity increase the compressive and tensile strength,} & \multicolumn{3}{c}{Most crucial parameter in preparing GPC mixture. In mix design, it is important to determine the optimum amount of the shrinkage cracks and affects the strength and durability properties} & \multicolumn{1}{c}{Most crucial parameter in preparing GPC mixture. In mix design, it is important to determine the optimum amount of activator polarity for effective strength and development. Moreover, the type of activator and industry in different molarities used impacts differently on the microstructural properties of GPC.  
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt}} \hline \hline \multirow{2}{*}{Activator/binder ratio} & \multirow{2}{*}{Increase in activator/binder ratio results in workable mixture of GPC} & \multicolumn{3}{c}{Most crucial parameter in preparing GPC mixtures. In mix design, it is important to determine the optimum amount of activator polarity for effective strength and development. Moreover, the type of activator and industry in different molarities used impacts differently on the microstructural properties of GPC.} \\ \hline \multirow{4}{*}{Silicate/hydroxoside ratio} & \multirow{2}{*}{Increase in silicate/hydroxoside content provides a workable GPC mixture along with an increase compressive and tensile strength.} & \multicolumn{3}{c}{The optimum amount of elasticity/binder ratio in GPC mixture greater than 1 vall result in porous microstructure [167] and effect of silica and alumina requires less amount of silica/hydroxoside ratio while preparing GPC mixture and vice versa.} \\ \hline \multirow{4}{*}{Silicate/Alumina ratio} & \multirow{2}{*}{Important parameter considered for high strength GPC. Higher the sils/alumina ratio, higher will be the strength development due to increase in SiO-Sb bonds and decrease in SiO-Sb bonds and decreases in SiO-Sb bonds [148].} & \multicolumn{3}{c}{The silica/alumina ratio in GPC mixture depends on precursor type and activator composition and content.} \\ \hline \multirow{4}{*}{Curing temperature} & \multirow{2}{*}{Higher curing temperature in greater early age strength development} & \multicolumn{3}{c}{Greater curing temperature also results in lower later age strength} & \multicolumn{3}{c}{Curing temperature used for GPC depends on the composition of precursor and reactants in geopolymeric process.} \\ \cline{1-1} \cline{3-3} \cline{5-6}  & & & \\ \hline \end{tabular}
\end{table} 
Table 9: Pros and cons of different parameters considered for GPC. In addition, the setting time and workability of GPC are also affected by the addition of OPC. [PERSON] et al. [53] investigated the setting time of GPC, which has been significantly reduced with 5% inclusion of OPC of total binder along with a slight reduction in workability. Consequently, the microstructure has been improved with higher compressive strength at 28 days due to the presence of a substantial portion of calcium-rich aluminosilicate gel. The effect of the OPC content on the setting time and compressive strength of geopolymer OPC concrete is shown in Figure 33.  
[PERSON] et al. [169] found that the properties of high calcium FA-based geopolymer have been improved by OPC usage. The increase in early and later age strength resulted due to the presence of both CSH and C-AS-H gel in the geopolymeric structure [169; 170]. [PERSON] et al. [53] studied the effect of FA-based GPC with 10% and 50% OPC replacement. With the help of SEM, they concluded that the GPC with 50% replacement exhibited more enrichment of C-AS-H, as compared to GPC with 10% OPC replacement, along with few partially reacted or unreacted FA and OPC particles. Hence, it is concluded that GPC containing OPC as partial replacement exhibits better mechanical and microstructural properties due to the presence of C-AS-H gel in geopolymeric reaction.