Engineering Properties and Microstructure of Soils Stabilized by Red-Mud-Based Cementitious Material.

Area of Science:

• Geotechnical Engineering
• Materials Science
• Environmental Science

Background:

• Red mud (RM) is a significant industrial byproduct of aluminum refining, posing environmental challenges.
• Effective recycling and reuse strategies for RM are crucial for sustainable industrial practices.
• Geotechnical applications offer a promising avenue for RM valorization.

Purpose of the Study:

• To investigate the feasibility of using red mud combined with magnesium oxide (MgO) or calcium oxide (CaO) as a soil stabilizer.
• To evaluate the impact of these RM-based binders on the physical, mechanical, and micro-structural properties of stabilized soil.
• To determine the optimal binder ratios and assess the performance under freeze-thaw conditions.

Main Methods:

• Preparation of RM-based binders by mixing red mud with MgO or CaO.
• Stabilization of soil using the prepared RM-based binders.
• Characterization of stabilized soil properties, including unconfined compressive strength (UCS).
• Investigation of micro-structural changes and performance under freeze-thaw cycles.
• Addition of sodium hydroxide (NaOH) to promote hydration reactions.

Main Results:

• RM-MgO and RM-CaO binders significantly improved the unconfined compressive strength (UCS) of the stabilized soil.
• Optimal binder ratios were identified: RM:MgO = 5:5 and RM:CaO = 8:2 for maximum UCS in initial mixtures.
• The addition of NaOH further enhanced UCS, with optimal ratios of 2:8 for RM-MgO and 4:6 for RM-CaO stabilized soils.
• Stabilized soils exhibited improved resistance to freeze-thaw erosion, with RM-MgO showing superior performance compared to RM-CaO.
• Hydrated magnesium silicate and hydrated calcium silicate were identified as key strengthening agents.

Conclusions:

• Red mud, when combined with MgO or CaO and NaOH, serves as an effective binder for soil stabilization in geotechnical applications.
• The stabilized soils demonstrate enhanced mechanical properties and durability, particularly under freeze-thaw conditions.
• This approach offers a viable solution for the sustainable management and valorization of red mud waste.