## 2 Materials and Methods
### Methods
#### 2.2.2 Olivine Comminution Employing the LA Abrasion Test and AR Technique  
A Los Angeles (LA) abrasion machine was used to grind the olivine particles to smaller sizes before applying them to the clay so as to improve the reactivity between the olivine and the clay, making it suitable for hydration and subsequent carbonation. The AR technique was employed to optimize the olivine sand particles during the breakage process so as to get particles in a define particle size class. Particles in the fine-sized class (\(-75\)\(\mu\)m)  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Property** & **Value** & **Standard Method** \\ \hline OMC (\%) & 20.5 & [41] \\ HC (m/s) & 8.26 \(\times\) 10\({}^{-10}\) & [42] \\ pH & 7.6 & [41] \\ Specific gravity & 2.3 & [41] \\ \hline HC = hydraulic conductivity; OMC = optimum moisture content; MDD = maximum dry density. & \\ \end{tabular}
\end{table}
Table 1: \(Cont.\)  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Major Oxides** & **Concentration (wt\%)** & **Standard Method** \\ \hline SiO\({}_{2}\) & 40.02 & \\ \hline Al\({}_{2}\)O\({}_{3}\) & 5.98 & \\ \hline Fe\({}_{2}\)O\({}_{3}\) & 8.04 & \\ \hline CaO & 0.20 & \\ \hline MgO & 44.01 & \\ \hline LOI & 1.75 & \\ \hline Sand (\%) & 32.25 & [41] \\ \hline Silt (\%) & 67.75 & [41] \\ \hline D\({}_{50}\)(mm) & 0.018 & - \\ \hline Specific gravity & 2.99 & [41] \\ \hline pH & 8.91 & [41] \\ \hline Electrical conductivity (mS/cm) & 0.17 & [41] \\ \hline Colour & Light green & - \\ \hline \hline \end{tabular}
\end{table}
Table 2: The olivine physico-chemical characteristics.  
were used to mix with the clay in the current study to promote effective reactivity between the clay and the olivine since the reactivity between olivine and the soil increases with the olivine particle size decreasing.  
The representative feed olivine sand particles (approximately 3000 g), together with the grinding steel balls, were fed into an Eco-smartz Los Angeles Abrasion machine (Code: NL 1008 X/003) (see Figure 1) for grinding. The technical specifications of the abrasion machine are given elsewhere [43]. The abrasion machine was adequately cleaned before feeding the olivine particles to prevent contamination, and the machine was then set to begin the grinding. After each grinding duration (200 min), the abrasion machine was stopped, and the contents were removed cautiously and poured into a tray. This procedure was repeated for all the representative feed samples. In this study, 9 steel balls of 0.441 kg, on a 3000 g bed of olivine sand particles upon grinding for 200 min is ideal for obtaining fine olivine size particles (\(-75\) um), based on our previous investigation [43]. The particle size distribution of the product from the breakage process were then analyzed using the sieve analyses. Precaution was taken to ensure that the sieves were not clogged, and a sieving time of 20 min was employed using a mechanical sieve shaker. Details about the comminution of olivine sand particles using the Los Angeles abrasion test and employing the AR method for the analysis are given elsewhere [43]. In order to better understand the application of the AR method in the optimization of olivine sand comminution, the authors would therefore like to invite interested readers to visit the study. In summary, the AR analysis of our previous study demonstrated that the use of 9 steel balls of 0.441 kg on a 3000 g bed of olivine sand particles upon grinding for 200 min is ideal for obtaining fine olivine size particles (\(-75\) um), which are required for achieving significant hydraulic conductivity reduction since the reactivity between the soil and olivine increases with the fineness of the olivine particles.  
Figure 1: Eco-smartz Los Angeles Abrasion machine.