Performance and Microstructure Characterization of Red Mud Based Concrete

Abstract

Red mud is a residue of the bayer process in the alumina industries, as its disposal creates ecological imbalances in the environment due to its high alkalinity. Red mud was partially used as a sustainable cementing material in the present study to defeat these negative impacts. So far, red mud was used in non-structural concrete constructions due to its limited pozzolanic properties. Whereas the present research work majorly focused on the enhancement of red mud pozzolanic properties and its usage in the structural concrete. In this regard, red mud was calcined at a temperature of 600and#8304; C for 1 to 6hrs and evaluated its physical, chemical, morphological and pozzolanic properties. From the results, physical properties (Viz., specific gravity, bulk density, particle size, specific surface area and mass loss) are reduced up to 2hrs of calcination due to moisture loss. But, after 2hrs of calcination, above physical properties are increased due to agglomeration between red mud particles, which was also seen in the SEM analysis. Red mud majorly contains silica, alumina and iron oxide in all calcined red mud. Whereas 2hrs calcined red mud has shown a higher percentage of silica (i.e., 24%). From the XRD analysis, mineral phase changes observed in the red mud with calcination, gibbsite and goethite (traced in non-calcined red mud) have changed to alumina and hematite (in 2hrs of calcination). In order to understand the pozzolanic property of calcined red mud, a strength activity index test has conducted. From the results, 2hrs calcined red mud has shown the better pozzolanic property than others, which was due to the presence of higher silica and poorly crystallinity of the red mud in 2hrs of calcination. Afterwards, 2hrs calcined red mud was partially replaced up to 20% of cement weight and prepared two grades of concrete (i.e., M35 and M70). Moreover, mechanical, durability and microstructural properties are evaluated with age progression up to 150days.