## 4 Conclusions  
This study focused on investigating the effects of initial surface evaporation on the performance of FA-based geopolymer pastes. Evaporation was controlled optionally for some test specimens by placing them in a sealed cover during the curing process. In addition, the thermal performance of two different types of Class F (low calcium) fly ash (namely Gladstone and Gladstone/Callide) was also investigated. The main points emanating from the preset investigation can be depicted as follows:  
* It can be seen that the degree of initial surface evaporation has a major effect on the final performance of the GP specimens, where sealing of the samples during the curing process, and hence limiting excess initial surface evaporation, produced more consistent results as well as much higher strength readings. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{**Sample ID**} & \multirow{3}{*}{\
\begin{tabular}{c} **Unsealed Gladstone** \\ **FA-Based GP Cubes** \\ \end{tabular} } & \multirow{3}{*}{
\begin{tabular}{c} **Sealed Gladstone** \\ **FA-Based GP Cubes** \\ \end{tabular} } & \multicolumn{3}{c}{**Sealed**} \\  & & & **F-Based GP Cubes** & & **Gladstone/Callide** \\ \cline{2-6}  & **400 \({}^{\circ}\)C** & **800 \({}^{\circ}\)C** & **400 \({}^{\circ}\)C** & **800 \({}^{\circ}\)C** & **400 \({}^{\circ}\)C** & **800 \({}^{\circ}\)C** \\ \hline GP 01 & 5.19 & 6.71 & 14.10 & 15.88 & - & - \\ GP 02 & 6.56 & 7.41 & 14.61 & 15.34 & - & - \\ GP 03 & 7.02 & 7.66 & 14.08 & 14.86 & - & - \\ GP 04 & 8.41 & 9.41 & 15.09 & 15.37 & 14.63 & 16.46 \\ GP 05 & 8.57 & 9.33 & 15.08 & 15.79 & 14.15 & 16.13 \\ GP 06 & 6.55 & 7.57 & 22.39 & 21.68 & 17.82 & 19.57 \\ GP 07 & 7.03 & 7.91 & 20.33 & 20.99 & 18.21 & 20.07 \\ GP 08 & 7.21 & 8.19 & 19.27 & 19.52 & 18.23 & 20.66 \\ GP 09 & 18.18 & 18.24 & 19.66 & 19.31 & 18.68 & 20.70 \\ GP10 & 18.13 & 18.50 & 19.75 & 20.04 & 17.27 & 17.90 \\ Minimum & 5.19 & 6.71 & 14.08 & 14.86 & 14.15 & 16.13 \\ Maximum & 18.18 & 18.50 & 22.39 & 21.68 & 18.68 & 20.70 \\ Average & 9.55 & 10.09 & 17.43 & 17.88 & 17.00 & 18.79 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Average percentage of mass losses. * Unsealed specimens exhibited an approximately 25% lesser value for the average initial strength, and approximately 35% and 25% lesser readings for the average residual strength readings at 400 \({}^{\circ}\)C and 800 \({}^{\circ}\)C, respectively. In addition, in the case of unsealed specimens, a comparably higher degree of thermal cracking and splitting were observed compared to the sealed specimens. * The initial strength readings also increased from approximately 15-58 MPa (GP 01-05) and 40-55 MPa (GP 06-10) for unsealed samples and 29-74 MPa (GP 01-05) and 22-58 MPa (GP 06-10) for sealed samples as the Na\({}_{2}\)SiO\({}_{3}\)/NaOH ratio increased from 0.5 to 2.5, presumably due to the increased levels of sodium silicate. Furthermore, an enhanced SiO\({}_{2}\) to Al\({}_{2}\)O\({}_{3}\) ratio is likely to cause an acceleration of the geopolymerization process, and hence resulted in relatively higher early strengths for the samples. * Majority of both Gladstone and Gladstone/Callide FA GP specimens exhibited higher initial strength readings at relatively lower alkaline solution to FA ratios. A maximum reading of approximately 75 MPa for the Gladstone and 57 MPa for the Gladstone/Callide FA GP specimens were recorded at 0.4 alkaline solution to FA ratio. This can be attributed to their comparatively denser microstructures, thus forming more homogenous materials with fewer number of pores. * In the case of the Gladstone/Callide FA specimens, large increments in strength, with a striking maximum of approximately 90 MPa, was observed compared to those made from Gladstone FA after being exposed to 400 \({}^{\circ}\)C. These variations can be attributed to a relatively higher level of silicon and aluminum, which in turn resulted in enhanced internal strength, primarily emanating from higher degrees of sintering, especially, at elevated temperatures.