# Strength Characteristics of Iron Tailings Blended Soil as a Road Base Material
## 2 Materials and Methods
### Test Methods  
According to the guidelines of test method given in test regulations for inorganic binder stabilized materials in highway engineering (JTGE51-2019) [19], the native soil, tailings, soil curing agent, water and cement were accurately weighed in accordance with the specified ratio of each testing material in Table 4. Firstly, the ITS and soil were mixed and stirred and the soil curing agent was added to the weighed water for dilution such that 80% diluted solution was sprayed into the modified soil to ensure uniform stirring. After that, it was placed inside a sealed bag to cure for 12 h duration. Then, the required cement and the remaining 20% dilute solution were added into the modified soil to ensure secondary stirring. Finally, the ITBS is statically pressed into a cylindrical sample having a diameter and height of 50 mm by using a jack and a mould and was then put into a standard curing box. Unconfined compressive strength (UCS) tests were conducted when the particular age was reached. Splitting tensile strength refers to the ultimate strength of the tested materials under axial tension. The preparation and curing of samples for this test are consistent with those of UCS samples. The tests in this study were conducted using a pavement material strength testing machine. Firstly, the splitting test fixture was installed in the equipment, and the cylindrical specimen was placed horizontally between the upper and lower jaws. After that, the loading rate was maintained at 1 mm/min to apply pressure to the specimen while recording the pressure value at the time of failure of the ITBS specimen. The flexural-tensile strength of base material refers to the ultimate strength of bearing axial tension under transverse bending. The sample is uniformly mixed in accordance with the procedure mentioned above. The mould size of flexural strength is 50 mm\(\times\)50 mm\(\times\)200 mm, the inner wall of the beam mould is brushed with oil and then the mixture is placed into the mould in three layers such that each layer is compacted evenly. After that, the material present in the mould is compressed with the help of jack and counter-force frame, and is then carefully cured in a curing tank. The flexural tensile strength test was carried out on the pavement material strength testing machine by three-point loading method. The loading rate is kept constant and continuous during the test, and maintaining a loading rate of 50 mm/min until failure. The mineral composition was tested by performing XRD analysis. The diffraction pattern was measured by a D-8 ADVANCE-X X-ray diffractometer (Bruker, Karlsruhe, Germany) such that the scanning range of 2\(\theta\) was recorded as 10\({}^{\circ}\)-80\({}^{\circ}\). Before the XRD \begin{table}
\begin{tabular}{l l l} \hline
**ITS Content (\%)** & **Cement Content (\%)** & **Curing Agent (\%)** & **Water Content (\%)** \\ \hline
30, 40, 50, 60, 70 & 0, 1, 2, 3, 4, 5 & 0, 0.5, 1, 1.5, 2 & 8, 10, 12, 14, 16 \\ \hline \end{tabular} \({}^{\dagger}\) The contents given here are the percentages of the corresponding substances in the ITS and the plain soil.  
\end{table} 
Table 4: Mixture ratios of experimental materials \({}^{\dagger}\). \begin{table}
\begin{tabular}{l l} \hline
**Parameter** & **Value or Description** \\ \hline Component & A by-product of the citrus industry \\ Color & Black, dark amber \\ State & Liquid \\ Density & 1.70 g/cm\({}^{3}\) \\ Solubility & Completely soluble in water \\ Odor & Sharp sulfurous smell \\ \hline \end{tabular}
\end{table} 
Table 3: Physical and chemical properties of ionic curing agent. tests, the tested samples were ground into powder with a size lower than 0.075 mm and dried at 60 \({}^{\circ}\)C for 12 h.  
SEM tests were conducted to investigate the microstructure of ITBS using a JSM-6490 LV scanning electron microscope of Electronics Co., Ltd. (Tokyo, Japan).