# Early Age Assessment of a New Course of Irish Fly Ash as a Cement Replacement
## 2 Materials and Methods  
The ash used for the analysis was taken from that stored at the Moneypoint power station situated in Co. Clare, Ireland (Figure 1). The samples for the study were obtained from three different sections within the ash field, reflecting ash deposits from different phases of operation (Figure 2). Four ash samples (each 5 kg) were collected at each of the three sections. The ash was taken from a depth of 1 m from the surface and stored within air tight containers to maintain the moisture content. All experiments were carried out using commercially obtained CEM I cement with and without fly ash at various replacement levels, as described in Table 1. The chemical compositions of the materials were determined by X-ray fluorescence (XRF), and X-ray diffraction (XRD) was used to monitor the changing mineralogical composition over time as hydration continued, as described in Tables 2 and 3. As shown in Table 2, most of the fly ash is SiO2, with high levels of Al2O3 and Fe2O3. Due to the lower CaO content and alumina content between 15 and 35%, this ash can be classified as Class F [6], as shown in the ternary diagram (Figure 3). A series of cement pastes were prepared at a w/c of 0.5 and cast into 20 \(\times\) 20 \(\times\) 20 mm cube moulds (Figure 4) and cured at 20 \({}^{\circ}\)C. XRD was carried out at 1, 7, 28 and 100 days, with a 20 mm cement cube being removed, powered down to  
Figure 1: (**a**) Location of Moneypoint power station in Ireland, (**b**) Moneypoint site layout. 10 \(\upmu\)m [7] and placed in the diffractometer for pattern acquisition. XRD data were collected using a Rigaku Miniflex600 spectrometer and scanned between 0 and 90\({}^{\circ}\) 20. \begin{table}
\begin{tabular}{c c c} \hline \hline
**CEM I-FA** & **CEM I** & **FA** \\ \hline
100-0 & 150 & 0 \\
90-10 & 135 & 15 \\
80-20 & 120 & 30 \\
65-35 & 97.5 & 52.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Binders studied (wt.%). \begin{table}
\begin{tabular}{l c c} \hline \hline
**Oxide (g/100 g)** & **CEM I a**  & **FA** \\ \hline SiO\({}_{2}\) & 19.04 & 53.70 \\ Al\({}_{2}\)O\({}_{3}\) & 5.01 & 16.81 \\ Fe\({}_{2}\)O\({}_{3}\) & 2.83 & 13.46 \\ CaO & 63.4 & 7.41 \\ MgO & 2.31 & 2.08 \\ K\({}_{2}\)O & 0.54 & 2.03 \\ Na\({}_{2}\)O & 0.28 & – \\ SO\({}_{3}\) & 2.65 & 1.11 \\ CaO (free) & 1.71 & – \\ CO\({}_{2}\) & 2.2 & – \\ Periclase & 1.0 & – \\ P\({}_{2}\)O\({}_{5}\) & & 0.41 \\ TiO & & 1.82 \\ MnO & & 0.13 \\ LOI & 3.20 & 2.55 \\ Density (g/cm\({}^{3}\)) & 2.95 & 2.24 \\ Blaine fineness (m\({}^{2}\)/kg) & 386 & 450 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Composition of CEM I cement and fly ash. Figure 2: Fly ash storage zones at Moneypoint power station, Co. Clare. Particle-size distribution and SEM images of the ash taken from the site are shown in Figures 5 and 6. As may be seen, the ash consists of very fine particles, with circa 99% passing a 0.1 mm sieve. This can also be seen in the SCM images taken at a 50 \(\upmu\)m resolution. Figure 4: mm cement samples. \begin{table}
\begin{tabular}{l l l l} \hline
**CEM I a** & \multicolumn{2}{c}{**FA b**  } \\ \hline C\({}_{3}\)S & 55.86 & Quartz & 1.29 \\ C\({}_{2}\)S & 10.07 & Calcite & 1.11 \\ C\({}_{3}\)A & 8.12 & Hematite & 4.65 \\ C\({}_{4}\)AF & 8.24 & Mullite & 7.95 \\ Lime & 1.64 & Magnetite & 3.37 \\ Calcite & 4.79 & Amorphous & 81.65 \\ Gypsum & 4.27 & & \\ Periclase & 0.96 & & \\ K\({}_{2}\)SO\({}_{4}\) & 0.86 & & \\ Na\({}_{2}\)SO\({}_{4}\) & 0.28 & & \\ K\({}_{2}\)O & 0.05 & & \\ Na\({}_{2}\)O & 0.15 & & \\ MgO & 2.21 & & \\ SO\({}_{3}\) & 2.53 & & \\ \hline \end{tabular}  
* CEM I composition calculated using normalisation [8]. b Determined using XRD Rietveld.  
\end{table} 
Table 3: Mineralogical composition of CEM I and fly ash used (wt.%). Figure 3: CaO-SiO\({}_{2}\)-Al\({}_{2}\)O\({}_{3}\) ternary diagram. Figure 7 shows an SCM of the 20% fly ash replacement after 60 days of hydration. The images show the formation of portlandite and ettrinigite, as highlighted by their expected crystal formation.