Characterization of coarse fraction of red mud as a civil engineering construction material

Abstract

Red mud is a highly alkaline (pH > 11) industrial solid waste produced by aluminum industries during extraction of alumina using Bayer process. The unutilized red mud stored either in slurry form or in dry stacking takes vast tract of usable land and has an adverse effect on the quality of ground water, surface water and also on animal and plant life. An attempt has been made here to characterize the coarse fraction (>75 μm) of red mud as an alternate construction material (medium value utilization). Different physical, chemical and morphological properties are investigated and the results are compared with Indian standard sand. The morphology using particle size analyzer is elaborated and correlated with engineering properties like shear strength and flowability parameters. In addition, chemical properties like pH, electrical conductivity, total dissolve solids (TDS), zeta potential, lime reactivity and leachate analysis are also investigated along with thermal property and are compared with that of Indian standard sand. The result of zeta potential test shows that the point of zero charge of red sand lies between the pH values of 5.5–6.5. Based on the lime reactivity, the red sand is found suitable as fine aggregate for cement and concrete. Low thermal conductivity of red sand reveals that it can dissipate the heat more efficiently. Leachate analysis shows that most of the heavy metals are within acceptable limit except Al. Based on the present study, the red sand can be used as a sustainable construction material there by utilizing the industrial waste and conserving natural resources.