Influence of Fly Ash on Geotechnical Behaviour of Red Mud: A Micro-mechanistic Study

The disposal of highly alkaline and hazardous bauxite residue mud generated from the Bayer process in the alumina industry leads to the serious environmental impact on natural resources. Effective and bulk utilization of red mud needs to be done to minimize an adverse impact on environment. The present study contracts to explore the possible utilization of red mud as a geomaterial by modifying its properties with fly ash (Class ‘F’). Detailed geotechnical properties (plasticity characteristics, compaction characteristics, swell index and Unconfined compressive strength (UCS)), physicochemical properties (pH and electrical conductivity) and micro-analyses (XRD, SEM, EDAX and FTIR) have been performed in the red mud amended with varying fly ash content up to 80%. The characterization of red mud demonstrates the higher value of specific gravity, liquid limit, optimum water content (OWC), maximum dry density (ρdmax), pH value, and electrical conductivity than that of the same of fly ash. Further, the amendment with various fly ash content has observed a significant effect on the plasticity and compaction characteristics of the red mud. The results show a significant reduction in liquid limit, plastic limit, OWC and ρdmax of red mud with an increase in fly ash content. Ultimate increase in the UCS of red mud is observed at its substitution with 15% fly ash which can be considered as an Optimum Fly Ash Content (OFC) from strength point of view. Further, experimental results are elucidated through physicochemical and microanalyses.