• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.333-340
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• 2019

Red mud is an industrial by-product produced during the manufacturing aluminum hydroxide (Al(OH)3) and aluminum oxide(Al2O3) from Bauxite ores. In Korea, aproximately 2 tons of red mud in a sludge form with 50% moisture content is produced when 1ton of Al2O3 is produced through the Bayer process. Neutralization of red mud will help to reduce the environmental impact caused due to its storage and also lessen significantly the ongoing management of the deposits after closure. It will also open opportunities for re-use of the residue which to date have been prevented because of the high pH. Moreover, attention to liquefied red mud(LRM) that does not require heating and grinding process for recycling is needed. In this paper, characteristics of compressive strength for cement paste with content of LRM neutralized by nitric acid and sulfuric acid. The results showed that compressive strength of cement paste with neutralized LRM is higher than that of cement paste with LRM.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.693-702
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• 2023

This research explores the potential application of Liquid Red Mud(LRM), a byproduct of industrial processes, in the construction sector. We neutralized LRM(pH 10-12) using nitric acid, aiming to understand its viability in construction applications. The study involved substituting LRM(pH 7-8) in mortar formulations, varying by cement type. We assessed the properties of these mixtures by measuring flow, setting time, and compressive strength. Additionally, X-ray Diffraction(XRD) and Scanning Electron Microscopy(SEM) analyses were conducted to examine the chemical properties. Results indicated a reduction in flow value for LRM and LN(neutralized LRM) compared to the control (Plain ) across different cement types. The setting times(initial and final) for LRM and LN were notably shorter than Plain. In compressive strength tests, LRM replaced with slag cement showed enhanced initial strength, though long-term strength gains were marginal across different cement types. SEM analysis revealed distinct voids in Plain and LN, with LRM exhibiting a fibrous microstructure. XRD patterns in SN(slag neutralized) resembled those in OR(original red mud) and ON(original neutralized), with a notable peak at a 2θ value of 22°. The study concludes that unneutralized LRM, when substituted for slag cement in mortar, yields superior initial strength compared to its neutralized counterpart.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.139-140
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• 2023

In this study, red mud with low recyclability was manufactured as liquid red mud, neutralized with sulfuric acid and nitric acid, and then added to cement paste to conduct research on physical and chemical properties. As a result, liquid red mud-added cement paste neutralized with sulfuric acid and nitric acid showed higher compressive strength after one day than cement paste with plain and non-neutralized liquid red mud. This indicates that nitric acid and sulfuric acid neutralization can increase initial strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.70-71
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• 2021

An increasing amount of red mud (RM) is being generated globally with the growth in alumi-num production. To avoid the RM becoming a pollutant, methods for effectively recycling RM at a low cost are being investigated. This study proposes a method for recycling RM as a construc-tion material. The cement paste with neutralized liquefied red mud had higher compressive strength than that of plain cement paste and cement paste with liquefied red mud without neutralization at 1 d of aging; this indicates that nitric acid neu-tralization increases the early-age strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.23-24
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• 2019

In this paper, the compressive strength characteristics of cement paste were compared with the addition of liquefied red mud with the addition of nitric acid in order to improve the strength of the deteriorated cement. The results showed that the compressive strength with between 7 days and 28 days was greater than that of liquefied red mud. The ratio of daily compressive strength of the liquefied red mud is higher than that of the Plain with a 1 percent addition rate, and the ratio of compressive strength is lower than that of the Plain on the 28 days. Therefore, the compressive strength of neutralization liquefied red mud compared to liquidated red mud was relatively high, and the compressive strength of the red mud was shown to be improved to a level almost similar to that of Plain.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.165-166
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• 2022

In this paper, the characteristics of slag cement mortar added with neutralized liquid red mud with nitric acid to reduce pH by neutralizing liquid red mud with nitric acid were reviewed to improve strength degradation of cement concrete added with liquid red mud. As a result, the compressive strength of cement mortar added with liquid red mud was higher than that of Plain on 1 and 3 days, and the strength of red mud neutralized with nitric acid was lower than that of cement mortar added with liquid red mud on 7 days, but the strength was recovered on 28th. It was found that the addition of red mud has the effect of improving the strength in the early age.