Abstract
Red Mud is the solid residue generated from Alumina refinery during the process of bauxite ore processing through Bayer’s process. Typical generation of red mud is 1.5 tons of red mud per ton of alumina produced. The disposal and storage of red mud has been a concern for the alumina industry since its inception, more than a hundred years ago. With the increase in alumina production, the magnitude of the problem is getting multiplied. Its alkaline nature (Na2O ~ 3-7%) and fine size make red mud unsuitable for many applications; a limited utilization is reported in cement industries as one of the raw mix components for cement. The present work deals with the utilization of red mud in geopolymer based paving blocks. Alumina, silica and alkali are the essential items required for geopolymer preparation. Having all these in red mud, the current study attempted to use the same in geopolymer based products. The focus has been on bulk utilization of red mud; target strength of 20 MPa after 28 days of curing (M20 grade) has been the goal as this strength is sufficient for many applications. The study focused on optimizing the red mud content, alkali concentration, fly ash content, etc. The samples are tested for its compressive strength and leachability. The study reveals that significant amount of red mud incorporation is possible with products conforming to USEPA 1311 norms.
Highlights
Red mud is the by-product of the Bayer process of alumina production from bauxite ore
Over 95% of the alumina produced all over the world is derived from bauxite using the Bayer process of alumina production [1] and the rest is either produced by the sintering process or a combination of both Bayer and sintering processes [2].In the Bayer process of alumina production, bauxite ore is treated with concentrated caustic solution at an elevated temperature and pressure; the alumina from the Al-hydroxide phases of bauxite ore are brought in to the solution, leaving the undissolved components in the residue- the red mud
Higher density of red mud is due to presence of iron minerals in larger quantities than that in fly ash, as can be seen from the chemical analysis and the mineral phases revealed in the XRD pattern
Summary
Red mud is the by-product of the Bayer process of alumina production from bauxite ore. Over 95% of the alumina produced all over the world is derived from bauxite using the Bayer process of alumina production [1] and the rest is either produced by the sintering process or a combination of both Bayer and sintering processes [2].In the Bayer process of alumina production, bauxite ore is treated with concentrated caustic solution at an elevated temperature and pressure; the alumina from the Al-hydroxide phases of bauxite ore are brought in to the solution, leaving the undissolved components in the residue- the red mud. The red mud having a hazardous and toxic nature causes damage to the ecology and environmental, and can be disastrous if the storage dams fail [6]; the spillage of 700,000 m3 of red mud slurry having high pH value of about 12 in Ajka, Hungary has caused of the loss of 10 humans and burning of hundreds people besides devastation of more than 40 square km [7, 8]
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