# Low-Grade Clay as an Alkali-Activated Material
## 3 Experimental Procedure  
### Materials  
The source binder material used in this experiment is low-grade clay from the Ballarat region of Victoria, Australia. The clay was made into powder using a Ball Mill Grinder Machine. The mill was composed of a total of 15 balls, and 5000 cycles were applied. Ground clay powder was sieved through a 100 \(\upmu\)m sieve, and the clay passing was used for characterization, pre-treatment, and casting of the mortar specimen. The clay was investigated under three different conditions: natural clay without thermal pre-treatment, clay calcinated at 120 \({}^{\circ}\)C for 24 h, and clay calculated at 750 \({}^{\circ}\)C for 5 h.  
The chemical composition was determined using Bruker Axs S4 Pioneer X-ray fluorescence equipment, as shown in Table 1. The particle size distribution was determined using a Malvern Mastersizer analyzer and the crystalline composition with a Bruker Axs D8 ADVANCE Wide Angle X-ray diffraction (XRD) instrument. XRD analysis was performed at 40 kV, Cu K\(\alpha\) = 1.54178 A wavelength, and a scanning range of 2 theta in 5\({}^{\circ}\)-95\({}^{\circ}\). Sample holders were filled using the front-loading procedure. The data obtained from XRD were interpreted using Bruker-DIFFRAC.EVA software and Rietveld analysis [37, 38]. The surface area was determined using the Brunauer-Emmett-Teller method by N\({}_{2}\) absorption. The crystalline and amorphous content, specific surface area, and particle size distribution are shown in Table 2.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Oxide (\%)**} & **Clay Without** & \multirow{2}{*}{**Clay Pre-Treated at 120 \({}^{\circ}\)C**} & **Clay Pre-Treated at 750 \({}^{\circ}\)C** \\  & **Pre-Treatment** & & \\ \hline Al\({}_{2}\)O\({}_{3}\) & 20.06 & 19.63 & 20.20 \\ SiO\({}_{2}\) & 62.13 & 63.57 & 65.50 \\ CaO & 0.71 & 0.67 & 0.70 \\ Fe\({}_{2}\)O\({}_{3}\) & 5.54 & 5.17 & 5.35 \\ K\({}_{2}\)O & 4.41 & 4.11 & 4.15 \\ MgO & 2.08 & 2.05 & 2.23 \\ MnO & 0.05 & 0.05 & 0.05 \\ TiO\({}_{2}\) & 0.90 & 0.91 & 0.85 \\ P\({}_{2}\)O\({}_{5}\) & 0.33 & 0.30 & 0.31 \\ LOI & 3.79 & 3.54 & 0.66 \\ Total & 100.00 & 100.00 & 100.00 \\ \hline \hline \end{tabular} Note: LOI = loss on ignition (unburnt carbon content).  
\end{table}
Table 1: Oxide composition of clay.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Property**} & **Without** & \multirow{2}{*}{**Pre-Treated at 120 \({}^{\circ}\)C**} & **Pre-Treated at 750 \({}^{\circ}\)C** \\  & **Pre-Treatment** & & \\ \hline Amorphous phase (\%) & 21.6 & 23.8 & 23.1 \\ Crystalline phase (\%) & 78.4 & 76.2 & 76.9 \\ Surface Area (m\({}^{2}\)/g) & 12.45 & 8.66 & 6.03 \\ D (10) \(\upmu\)m & 3.00 & 4.25 & 5.23 \\ D (50) \(\upmu\)m & 14.76 & 17.03 & 22.41 \\ D (50) \(\upmu\)m & 77.88 & 65.18 & 66.75 \\ \hline \hline \end{tabular} The alkali activator used was a combination of commercial sodium hydroxide (15 M) solution, supplied by Science Supply Australia Pty Ltd. and grade D sodium silicate solution, supplied by PQ Australia Pty Ltd., with a specific gravity of 1.53 and alkaline modulus of 2, where Na\({}_{2}\)O = 14.7%, SiO\({}_{2}\) = 29.4%, and H\({}_{2}\)O = 55.9% by mass. Local river sand from Victoria, Australia, with a fineness modulus of 2.6 was used as fine aggregate. The fine aggregate was prepared in accordance with AS 1141.5 [39].  
\end{table}
Table 2: Amorphous and crystalline content and BET surface area of clay material.