# Replacement of Natural Sand with Expanded Vermiculite in Fly Ash-Based Geopolymer Mortars
## 2 Experimental Program
### Mix Proportion, Production and Testing  
Twelve geopolymer mixtures were prepared, consisting of six mixtures with a 10 molar NaOH solution (group A) and six mixtures with a 15 molar NaOH solution (group B). In each group, sand was replaced with expanded vermiculite at two volume replacement ratios: 15% and 30%. FA was used at volume ratios of 50% and 70% of the total mixture. The mix proportions were obtained based on the trial mixes. After preparing the trial mixes, it was observed that a content of expanded vermiculite in the mixture higher than 30% presented workability problems and a very low compressive strength. Therefore, the ratio of expanded vermiculite was limited to maximum of 30% in this study. Table 4 shows the mix proportions of different geopolymer mixes. For producing the geopolymer mixes, sand, FA and vermiculite were first mixed for 3 min. Then, the pre-mixed alkaline activator and water were mixed with the dry components for 2 min. Finally, the fresh mixture was poured into prism-shaped models to produce 40 \(\times\) 40 \(\times\) 160 mm specimens. Different tests were conducted on each unique mix to assess the fresh and hardened properties of the geopolymer mixes, including the flowability, apparent porosity, dry unit weight, water absorption, compressive strength, \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Mix**} & **Water** & **Na\({}_{2}\)SiO\({}_{3}\)** & **NaOH** & **NaOH** & **Sand** & **Fly Ash** & **Vermiculite** & **Sand** & **Fly Ash** & **Vermiculite** \\  & **(kg/m3)** & **(kg/m3)** & **(kg/m3)** & **(Molar)** & **(kg/m3)** & **(kg/m3)** & **(kg/m3)** & **(kg/m3)** & **(\%)** & **(\%)** \\ \hline S50F50V0A & 180 & 180 & 90 & 10 & 525 & 722 & 0 & 50 & 50 & 0 \\ S35F50V15A & 180 & 180 & 90 & 10 & 367 & 722 & 10.2 & 35 & 50 & 15 \\ S20F50V30A & 180 & 90 & 10 & 210 & 722 & 20.4 & 20 & 50 & 30 \\ S30F70V0A & 220 & 180 & 90 & 10 & 295 & 946 & 0 & 30 & 70 & 0 \\ S15F70V15A & 220 & 180 & 90 & 10 & 147 & 946 & 9.5 & 15 & 70 & 15 \\ S60F70V30A & 220 & 180 & 90 & 10 & 0 & 946 & 19.1 & 0 & 70 & 30 \\ S50F50V0B & 130 & 180 & 90 & 15 & 572 & 787 & 0 & 50 & 50 & 0 \\ S35F50V15B & 110 & 180 & 90 & 15 & 412 & 811 & 11.4 & 35 & 50 & 15 \\ S20F50V30B & 110 & 180 & 90 & 15 & 236 & 811 & 22.9 & 20 & 50 & 30 \\ S30F20V0B & 210 & 180 & 90 & 15 & 302 & 971 & 0 & 30 & 70 & 0 \\ S15F70V15B & 210 & 180 & 90 & 15 & 151 & 971 & 9.8 & 15 & 70 & 15 \\ S60F70V30B & 185 & 180 & 90 & 15 & 0 & 1012 & 20.4 & 0 & 70 & 30 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mix proportions of geopolymer mortar. \begin{table}
\begin{tabular}{c c} \hline \hline
**Color** & **Gold** \\ \hline Shape & Accordion-shaped granule \\ Water capacity held & 240\% (by weight) \\  & 28\% (by volume) \\ Cation exchange capacity & 50–150 meg/100 g \\ Thermal conductivity & 0.065–0.062 W/mK \\ Permeability & 95\% \\ pH & 8.1 \\ Sintering temperature & 650–1000 \({}^{\circ}\)C \\ Combustibility & Non-combustible \\ Specific heat & 0.20–0.26 Kcal/kg\({}^{\circ}\)C \\ Specific gravity & 0.22 \\ Bulk density & 140 kg/m\({}^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Properties of the expanded vermiculite obtained from the supplier. ultrasound pulse velocity and thermal conductivity. The flowability test was performed according to EN 1015-3 [32]. The apparent porosity, unit weight and water absorption of the geopolymers were obtained from the prisms according to ASTM C20 [33]. The uniaxial compressive strength test was performed on half of the prisms based on TS EN 12390-3 [34], and the ultrasound test was performed on the prisms according to TS EN 12504-4 [35]. For measurement of the thermal conductivities of the prism specimens, a C-Therm Analyzer with a modified transient plane source was applied. Figure 3a-c shows the performed tests for the compressive strength, ultrasound velocity and thermal conductivity of the geopolymers, respectively. Three nominally identical samples were used for each unique configuration.