Biopolymer amendment for mitigating dispersive characteristics of red mud waste

Abstract

Previous studies revealed that the geotechnical properties of red mud waste (RMW) closely resemble that of conventional soils. Due to the predominant presence of exchangeable sodium, the RMW tends to exhibit high-dispersion behaviour. In this study, mitigation of the dispersion characteristics of RMW using eco-friendly biopolymers was investigated. Two types of biopolymers, namely guar gum (GG) and xanthan gum (XG), in 0·5, 1, 2, 3 and 4% (by weight), were selected for the study. The untreated and polymer-amended RMW samples were subjected to cylindrical dispersion crumb tests for examining the dispersion phenomenon, and the hardened samples were further analysed for microstructure, mineralogical and elemental compositions. Turbidity and pH of water in the crumb tests as well as consistency limits of untreated and polymer-amended RMW were also tested. The microstructural analysis revealed an increase in particle aggregations with an increase in the biopolymer content, while elemental compositions showed gel formation by GG cross-linking with calcium. As such, GG proved to be more effective over XG in mitigating the dispersion characteristics of the RMW. Overall, this study shows that GG biopolymer has potential to be used for mitigating dispersion and controlling dusting in field applications.