Comparison of advanced hydraulic properties between treated and untreated bauxite residue

¹ Gradute Student, Dept. of Civil Engineering, California State University Los Angeles, USA
² Assistant Professor, Dept. of Civil Engineering, California State University, Los Angeles USA
³ Project Engineer, Golder Associates, Inc., 13515 Barrett Parkway Drive, Suite 260 Ballwin, Missouri, USA
⁴ Professor, Dept. of Civil Engineering, California State University, Los Angeles USA

^* Corresponding author: wkwan4@calstatela.edu

Abstract

Advanced hydraulic characteristics of treated and untreated Bauxite Residue (Red Mud) are studied and compared using a Steady-State Centrifugation (SSC) Unsaturated Flow Apparatus (UFA). Red Mud is the by-product waste from the Bayer process during aluminum production that has shown the potential of being reused as fill material in embankment construction, which can reduce the energy consumption of disposing the minging waste and producing fill materials. There is a limited number of documented studies on unsaturated hydraulic characteristics of RM. Furthermore, the high alkalinity (pH > 12) of the bauxite slurry is a challenge for reusing the material. Past studies have shown two effective and economic neutralization methods: (i) mixing with seawater and (ii) addition of gypsum. This study utilizes Cal State LA centrifuge facilities to characterize the unsaturated hydraulic properties of the treated and untreated Red Mud. The experimental results are used to develop the Soil Water Retention Curve (SWRC) for the three types of Bauxite Residue: untreated, treated with saline solution, and treated with gypsum. The results show that adding gypsum is more effective than mixing with saline solution in reducing the pH value of RM, and the samples treated with saline solution provide the lowest range of unsaturated hydraulic conductivity values compared with the other two types.