# Effect of Curing Conditions on Microstructure and Pore-Structure of Brown Coal Fly Ash Geopolymers
## 3 Experimental Procedure  
### Materials Used  
The brown coal fly ash used in this study was obtained from the Loy Yang power plant in the La Trobe Valley, Victoria, Australia. The brown coal fly ash supplied was obtained directly from the electrostatic precipitators with no treatment or time in storage ponds prior to being used in concrete production. Table 1 shows the chemical composition of the ash, determined by Bruker Axs S4 Pioneer X-ray fluorescence (XRF) instrument (Bruker Corporation, Massachusetts, United States). The significant variation in the CaO content has been observed in brown coal both in Australia and from other countries [13; 29]. This has included CaO concentrations in excess of 2.25% and as such is not regarded as untypical. The particle size distribution was obtained using Malvern Mastersizer analyzer (Malvern Panalytical Ltd, Malvern, United Kingdom). The amorphous content and crystallinity of Loy Yang fly ash was determined using Bruker Axs D8 ADVANCE Wide Angle X-Ray Diffraction (XRD) instrument (Bruker Corporation, Massachusetts, United States) and presented in Table 2. The XRD measurement was performed at 40 kV, Cu K\(\alpha\) = 1.54178 A wavelength; scanning range 2 theta in 5\({}^{\circ}\)-95\({}^{\circ}\). The sample holders were filled using the front-loading procedure. The data obtained from XRD were interpreted using Bruker-DIFFRAC.EVA software and a Rietveld analysis [30; 31] in order to quantify the amorphous and crystalline percentage. The fly ash surface area was determined using Brunauer Emmett Teller method by N\({}_{2}\) absorption [32; 33].  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Brown Coal Fly**} & \multicolumn{8}{c}{**By Weight (\%)**} \\ \cline{2-13}  & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **CaO** & **K\({}_{2}\)O** & **TiO\({}_{2}\)** & **P\({}_{2}\)O\({}_{3}\)** & **MgO** & **Na\({}_{2}\)O** & **SO\({}_{3}\)** & **MnO** \\ \hline [PERSON] & 47.52 & 17.29 & 5.98 & 2.25 & 0.50 & 1.26 & 0.74 & 4.63 & 6.26 & 13.03 & 0.54 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The chemical composition.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Properties Investigated**} & **Loy Yang** \\ \hline BET Surface Area, (m\({}^{2}\)/kg) & 279 \\  & 10 microns & 6.5 \\ \% passing at & 20 microns & 19.7 \\  & 45 microns & 45.1 \\  & 75 microns & 62.0 \\ Amorphous (\%) & 62.5 \\ Crystalline (\%) & 37.5 \\ Unburnt carbon content (\%) & 1.43 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The physical and mineralogical properties.  
The alkali activator used contained a mixture of commercially available sodium hydroxide (15 M) solution from Science Supply Australia and the sodium silicate solution had a specific gravity of 1.53 and alkaline modulus = 2, where Na\({}_{2}\)O = 14.7%, SiO\({}_{2}\) = 29.4% and H\({}_{2}\)O = 55.9% by mass [5; 34]. Both the coarse and fine aggregate were prepared in accordance with AS 1141.5 [35]. The river sand in uncrushed form (specific gravity of 2.5 and a fineness modulus of 3.0) was used as a fine aggregate. The granite crushed aggregate of two-grain sizes, 7 mm of 2.58 specific gravity and 1.60% water absorption and 10 mm of 2.62% specific gravity and 0.74% water absorption, were used as coarse aggregates. It is noted that the coarse aggregate was selected to produce laboratory-scale concrete specimens and is comparable with the other studies [34; 36; 37].