## 4 Mechanical Properties of Geopolymer Concrete
### Factors on Workability of GPC and PCC
\begin{table}
\begin{tabular}{c c c} \hline
**Author** & **Aim** & **Results** \\ \hline [PERSON] et al. [26] & Investigation of engineering properties of fly ash-based GPC with different SH concentrations compared to OPC & The compressive strength of GPC with the SH concentrations values of 14M and 12M were higher than those of OPC specimens at 7 and 28 days. The elasticity modules of GPC under uniaxial tension were around 7-8\% less than that of OPC. The elasticity modules of GPC under compression were about 12-13\% less than that of OPC. \\ \hline [PERSON] et al. [27] & The comparison of temperature effect on compressive strength of GPC and OPC & The degradation in concrete strength was seen for both GPC and OPC beyond 300 \({}^{\circ}\)C. The relatively better bond properties were found for GPC specimens with the SiO\({}_{2}\)/K\({}_{2}\)O molar ratio of 1 compared to the similar levels of compressive strength for OPC. \\ \hline [PERSON] et al. [28] & Evaluating the strength of RGPC compared to ROPC based on percentage of waste rubber fibers & The compressive strength in both RGPC and ROPC decreased while increasing the percentage of waste rubber fibers at all ages. The elasticity modules of RGPC and ROPC was sharply decreased by 36.34\% and 34.54\%, respectively, while increasing fiber content from 0 to 30\%. \\ \hline [PERSON] et al. [29] & The effect of W/S ratio on behavior of GPMs and PCMs & The increment of W/S ratio led to the decrement of compressive strength at each age (1, 7, 28 days). GPMs mixes had very rapid and higher strength, approximately three times that of equivalent PCMs, achieving 55–66\% of their strength at 28 days in the first 24 h after mixing. \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._In [PERSON] and [PERSON] [31], the efficiency of GPC under different curing conditions was explored in order to evaluate the setting and workability of fly ash GPC, as well as concrete strength at the early age. The laboratory results showed that the test specimens cured in an ambient temperature had a higher proportion for desirable workability and compressive strength compared to heat curing. The inclusion of class F fly ash in the content of this concrete mixture led to a significant increase in the value of compressive strength compared to that of OPC. In an experimental program by [PERSON] et al. [32], the interaction of mineral and chemical admixture with different cements for self-compacting concrete (SCC) was investigated. Diverse characteristics in the cement combination was sufficient to influence the properties of SCC. The laboratory observation indicated that the compatibility of cement and admixtures are deeply attributed to molarity ratio of chemical combinations, such as C\({}_{3}\)A, C\({}_{2}\)S/C\({}_{3}\)S, participating in concrete structure and specific surface area available in cement, as well as the superplasticizer type utilized in this case. Similarly, in another attempt, [PERSON] et al. [33] presented the investigations to point out the effect of various SPs involving naphthalene (N), melamine (M) and polycarboxylate (PC) on workability, and compressive strength of the concrete mixtures consisted of alkaline-activated material (AAM), such as FA, which was considered a sustainable contender for OPC. The results showed that SP type along with water/precursor (W/P) ratio were two dominate factors affecting on the improvement of compressive strength concrete workability. As for the combinative usage of sustainable material in concrete production, [PERSON] et al. [34] conducted a laboratory program to investigate the efficiency of combined ingredients such as ground granulated blast furnace slag (GGBS) and fly ash combination, considering water to binder (W/B) ratio on the concrete properties including workability (slump) and compressive strength in the case of alkali activated geopolymeric recycled aggregate concrete (GRAC). The results showed that GGBS and FA are significantly responsible for the workability and mechanical properties, respectively.