## 3 Sampling and Characterization  
Different compositions (10%, 20%, 30%, and 40% BA) were used. The weight percentages of SS and NaOH were adjusted in each sample with a SS/NaOH ratio at 15 in order to study the effect of BA content and curing temperature (CT) on the intumescence behaviour of thermal geopolymer foams (TGPFs). The samples were designated according to the percentage content of BA and the CT. The sample designations and compositions are represented in Table 1.  
The samples were manually cut to proper shape and dimensions with a hacksaw for the characterization.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{\
\begin{tabular}{c} **Sample** \\ **No.** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Sample** \\ **Designation** \\ \end{tabular} } & **Wt.\% Age of** & **Curing** & **Wt.\% Age of** & **Wt.\% Age of** & **Na2 SiO3 to** & **Liquid to** \\  & & **Bottom Ash** & **Temperature** & **Sodium** & **Sodium** & **NaOH Ratio** & **Solid Ratio** \\ \hline \multirow{2}{*}{\(1\)} & BA10-200 & 10 & 200 & 84.5 & 5.5 & 15.36 & 9 \\  & BA10-400 & 10 & 400 & 84.5 & 5.5 & 15.36 & 9 \\  & BA10-500 & 10 & 500 & 84.5 & 5.5 & 15.36 & 9 \\  & BA10-600 & 10 & 600 & 84.5 & 5.5 & 15.36 & 9 \\  & BA20-200 & 20 & 200 & 75 & 5 & 15 & 4 \\  & BA20-400 & 20 & 400 & 75 & 5 & 15 & 4 \\  & BA20-500 & 20 & 500 & 75 & 5 & 15 For the bulk density and foamability, the samples were cut in orthogonal blocks, and their edges were measured to calculate the volume. The bulk density was calculated by the following formula:  
\[\textit{Bulk density}\left(\frac{g}{cm3}\right)=\textit{Mass}/\textit{ Volume}\]  
The apparent density of TGPFs was calculated using a pycnometer, and the foamability was calculated using the following formula:  
\[\%\textit{Foamability}=1-(\textit{bulk density}\div\textit{ apparent density})\times 100\]  
The water absorption index (WAI) is a measure of open porosity [13; 14]. All the samples were weighed and then placed in water for 48 h. After 48 h, these samples were taken out of water and then weighed again. WAI values were calculated by the following formula:  
\[\text{WAI}(\%)=\left(\frac{m2}{m1}-1\right)\times 100\]  
where \(m_{1}\) is the weight of the sample before water absorption and \(m_{2}\) is the weight of the sample after water absorption.  
The weight loss index (WLI) test has been used as a measure of resistance to dissolution in water and the degree of geopolymerization [15]. The samples were weighed and then placed in the water for 48 h. After 48 h in water, the samples were taken out of water and dried in an oven at 120 \({}^{\circ}\)C. After drying, these samples were weighed again. WLI was calculated by using the following formula:  
\[\text{WLI}(\%)=\left(\frac{m2}{m1}-1\right)\times 100\]  
where \(m_{1}\) is the weight of the sample before immersing in water and \(m_{2}\) is the weight of the sample after drying in the oven.  
Samples were subjected to a compression test, FTIR analysis, SEM, and XRD. The FTIR analysis was carried out on FT/IR4100 typeA spectrometer, Jasco, Tokyo, Japan at a scanning speed of 2 mm/sec and a resolution of 4 cm\({}^{-1}\). Compression tests were carried out on TIRAtest 2810 E6 Universal Testing Machine, Germany according to ASTM standards C-365. A load cell of 10 kN and a strain rate of 1 mm/min were employed in the test.