## 4 Results and Analysis
### Durability under Wetting-Drying Cycles  
Figure 6 presents \(G_{0}\) variation of iron ore tailings compacted at \(\gamma_{d}\) of 17, 18 and 19 kN/m\({}^{3}\) and treated with 1 to 5% of early strength Portland cement. Wetting-drying cycles were performed after 2, 4 and 7 days of curing. Such performance mimics the behaviour of the studied blends after being submitted to harsh on-field conditions over 12 cycles of such procedures. It is well established that increasing both the quantity of cement and \(\gamma_{d}\) improves the stiffness of the compacted iron ore tailings-Portland cement mixes considering wetting-drying cycles. Disregarding the initial curing time (2, 4 or 7 days), Figure 6 shows a comparable qualitative response regarding the impact of wetting-drying cycles: \(G_{0}\) increased from zero to three wetting-drying cycles and then oscillated about an average, distinctive for each \(\gamma_{d}\) and quantity of cement employed, for additional cycles. The oven drying for 42 h at 71 \(\pm\) 2 \({}^{\circ}\)C, during the drying part of the wetting-drying cycles, triggered the catalysis of the chemical reactions of the Portland cement, bringing about the increase of \(G_{0}\) of iron tailings-Portland cement mixes in the initial cycles. Distinct results were achieved by [PERSON] et al. [28], who assessed the effect of wetting-drying cycles on \(G_{0}\) of a nonplastic silt. Test results by [PERSON] et al. [28] indicated that \(G_{0}\) of nonplastic silt-Portland cement (also early strength) blends mostly reduced with more wetting-drying cycles, reaching a steadiness at about six wetting-drying cycles.  
Figure 7 presents the correlation of \(q_{u}\) and \(G_{0}\) as a function of \(\eta\)/\(C_{iv}\) index after 12 wetting-drying cycles. Looking at \(q_{u}\) results Figure 7a, it can be noticed that after 12 wetting-drying cycles, \(q_{u}\) is related to \(\eta\)/\(C_{iv}\) index through Equation (4). This equation has the same form as Equation (2) and the scalar of present equation is found above results of 90 days of curing at 23 \({}^{\circ}\)C. The \(q_{u}\), after 12 wetting-drying cycles, being above the results of 90 days of curing at 23 \({}^{\circ}\)C is an example of enhancement triggered by the catalysis of the chemical reactions of the Portland cement, due to oven drying for 42 h at 71 \(\pm\) 2 \({}^{\circ}\)C.  
Figure 6: \(Cont.\)  
Figure 6: Performance (initial shear stiffness (\(G_{0}\)) variation) of compacted iron ore tailings treated early strength Portland cement after wet–dry cycles after: (**a**) curing for 2 days, (**b**) curing for 4 days and (**c**) curing for 7 days.  
Figure 7: Compacted filtered iron mining tailings treated with early strength Portland cement and cured for 2, 4 and 7 days: (**a**) \(q_{u}\) versus \(\eta/C_{ip}\) after 12 wet-dry cycles and (**b**) \(G_{0}\) versus \(\eta/C_{ip}\) after 12 wetting–drying cycles.  
On the other hand, focusing on the \(G_{0}\) results in Figure 7b, it can be noted that after 12 wetting-drying cycles, \(G_{0}\) is related to \(\eta\)/\(C_{iv}\) index through Equation (5). Such an equation has the same form as Equation (3), and the scalar of present equation is higher than the results of 90 days of curing at 23 \({}^{\circ}\)C. However, for \(q_{u}\) and \(G_{0}\), results after 12 wetting-drying cycles are of the same order of magnitude as the results after 90 days of curing at 23 \({}^{\circ}\)C.  
\[q_{u}(\mathrm{kPa})=6.45\times 10^{4}\times\left[\frac{\eta}{C_{iv}}\right]^{-1.30} \tag{4}\]  
\[G_{0}(\mathrm{MPa})=8.59\times 10^{4}\times\left[\frac{\eta}{C_{iv}}\right]^{-1.30} \tag{5}\]