## 3 Experimental Program
### Methods  
#### 3.2.1. Moulding Portland Cement Stabilized Iron Ore Tailings (IOT) Specimens  
Cylindrical specimens (50 mm in diameter and 100 mm in height) were moulded for the unconfined compression and initial shear stiffness tests, as well as for performance under wetting-drying and for consolidated isotropically drained triaxial tests using the undercompaction method [18]. A target dry unit weight (\(\gamma_{d}\)) for a particular specimen was then instituted as a result of the dry compacted iron tailings-Portland cement mix divided by the total volume of the specimen [19]. As exhibited in Equation (1) [20], porosity (\(\eta\)) is a function of dry density (\(\gamma_{d}\)) of the mix and Portland cement content (PC). Each substance (iron mine tailings and Portland cement) has a unit weight of solids (\(\gamma_{SiOT}\) and \(\gamma_{5\mathrm{PC}}\)), which also must be measured for computing porosity.  
\[\eta=100-100\left\{\left[\frac{\gamma_{d}}{1+\frac{PC}{100}}\right]\left[ \frac{1}{\gamma s_{IOT}}+\frac{\frac{PC}{100}}{\gamma s_{PC}}\right]\right\} \tag{1}\]  
After the weighing of the dry materials (i.e., iron mine tailings and cement), these were manually mixed with a spoon until a powder having a visual uniformity was obtained. Next, the correct amount of distilled water was supplemented to reach moisture content of 11.6% (optimum moisture content for standard Proctor compaction effort--see Table 1) for the iron tailings--Portland cement blend, and the mixture continued up to the formation of a homogeneous paste. Following, the specimen was statically compacted inside a cylindrical split mould to its target dry unit weight. Three layers were used in the compaction process, with the top of the first and second layers being slightly scarified in order to guarantee the adherence of the subsequent layer. Once the moulding was finished, the specimen was retrieved from the mould, measured, weighed and sealed inside a plastic bag (to maintain water content) and sent to be cured in a humid room at 23 \(\pm\) 2 \({}^{\circ}\)C with relative moisture of about 95%. As acceptance criteria, the obtained dry unit weight (\(\gamma_{d}\)) should range within \(\pm\) 1% of the target value, whereas the moisture content (\(w\)) should be around 0.5% of the previously assigned value. Within each tested dosage, the cement content was calculated over the mass of dry iron mine tailings and the dry unit weight (\(\gamma_{d}\)) was determined as the ratio between the mass of dry solids and the total volume of the test specimen.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Physical Properties** & **Iron Ore Tailings (IOT)** \\ \hline Specific gravity of solids & 2.916 \\ Uniformity coefficient & 10.7 \\ Coefficient of curvature & 3.9 \\ Mean particle diameter-(mm) & 0.085 \\ Liquid limit (\%) & - \\ Plastic limit (\%) & - \\ Plasticity index (\%) & Nonplastic \\ Medium sand (0.425 mm \(<\)\(d\) \(<\) 0.200 mm) (\%) & 4.0 \\ Fine sand (0.075 mm \(<\)\(d\) \(<\) 0.425 mm) (\%) & 49.0 \\ Silt (0.002 mm \(<\)\(d\) \(<\) 0.075 mm) (\%) & 42.0 \\ Clay (\(d\) \(<\) 0.002 mm) (\%) & 5.0 \\ USCS Classification (ASTM 2017) & SM \\ Maximum dry unit weight at standard energy compaction (kN/m\({}^{3}\)) & 19.2 \\ Optimum moisture content at standard energy compaction (\%) & 11.6 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Physical properties of studied iron ore tailings.