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. 2022 Jan 31;15(3):1123.
doi: 10.3390/ma15031123.

Reuse of Red Mud and Bauxite Tailings Mud as Subgrade Materials from the Perspective of Mechanical Properties

Xiaoduo Ou  1 , Shengjin Chen  1   2 , Jie Jiang  1 , Jinxi Qin  3 , Lu Zhang  4
Affiliations

Reuse of Red Mud and Bauxite Tailings Mud as Subgrade Materials from the Perspective of Mechanical Properties

Xiaoduo Ou et al. Materials (Basel). .

Abstract

In order to reuse red mud and bauxite tailings mud (two typical aluminum industrial wastes) to reduce the occupation of land resources and environmental damage, these two wastes were combined to develop subgrade materials for the first time. With different combinations, the effects of the amounts of red mud, tailings mud, and cementitious materials on the strength of tested subgrade materials were investigated. The mechanism of strength growth was analyzed by a micro-test. The test results showed that the material strength of three combinations met the requirements when the unconfined compression strength (UCS) of all combinations increased with age. The UCS of the A1BC2 combination (the mass ratio of red mud and tailings mud was 2:1, the mass ratio of cement and quicklime was 1:1, and the mass ratio of waste and cementitious materials was 1:0.2) was the best, with the UCS being 3.03 MPa in 7 days. Microscopic imaging showed that specimens with high red mud contents had compact structures without cracks. The strength of these materials is mainly due to hydration reactions and pozzolanic reactions; the cementitious products generated by the reactions solidify Na+ and inhibit the release of OH-, while the addition of tailings mud can reduce the content of Na2O in the material, which makes the environmental compatibility of the A3BC2 combination the best (the mass ratio of red mud and tailings mud was 1:2, the mass ratio of cement and quicklime was 1:1, and the mass ratio of waste and cementitious materials was 1:0.2). Its pH value was 8.75. This experiment verifies the feasibility of the combined application of red mud and tailings mud in subgrade materials. To this end, a feasible scheme for the simultaneous consumption of these two kinds of aluminum industrial wastes has been proposed.

Keywords: Bayer red mud; bauxite tailings mud; environmental protection; mechanical properties; subgrade material.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Photograph of the red mud reservoir.
Figure 2
Figure 2
Photograph of the tailings mud reservoir.
Figure 3
Figure 3
Specimens for the compaction test.
Figure 4
Figure 4
Specimens for the unconfined compression test.
Figure 5
Figure 5
Relation between maximum dry density and optimum water content of various combinations (a–c).
Figure 6
Figure 6
Change graphs of UCS of different combinations with the same dosage of cementitious material (a–c).
Figure 6
Figure 6
Change graphs of UCS of different combinations with the same dosage of cementitious material (a–c).
Figure 7
Figure 7
Comparisons of the UCS of each combination cured for 7 days.
Figure 8
Figure 8
Comparisons of the UCS of each combination cured for 28 days.
Figure 9
Figure 9
Comparisons of the UCS of BC2 composites cured for 28 days with and without immersion.
Figure 10
Figure 10
500× SEM image of the A1BC2 combination.
Figure 11
Figure 11
2000× SEM image of the A1BC2 combination.
Figure 12
Figure 12
500× SEM image of the A3BC2 combination.
Figure 13
Figure 13
2000× SEM image of the A3BC2 combination.
Figure 14
Figure 14
Image of the hydration products of the A1BC2 Combination (1).
Figure 15
Figure 15
Image of the hydration products of the A1BC2 Combination (2).
Figure 16
Figure 16
Variation of pH values with leaching time.
See this image and copyright information in PMC

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