Abstract
In order to effectively utilize aluminum industrial waste—red mud and bauxite tailings mud—and reduce the adverse impact of waste on the environment and occupation of land resources, a red mud–bauxite tailings mud foam lightweight soil was developed based on the existing research results. Experiments were conducted to investigate the mechanical properties and microscopic characteristics of the developed materials with different proportions of red mud and bauxite tailings mud. Results show that with the increase in red mud content, the wet density and fluidity of the synthetic sample was increased. With 16% red mud content, the water stability coefficient of the synthetic sample reached its maximum of 0.826, as well as the unconfined compressive strength (UCS) of the sample cured for 28 d (1.056 MPa). SEM images reveal that some wastes of the sample without red mud were agglomerated, the peripheral hydration products were less wrapped, and when the amount of red mud was 16%, the hydration products tightly wrapped the waste particles and increased the structural compactness. The final concentration of alkali leaching of samples increased with the addition of red mud. The maximum concentration of alkali leaching was 384 mg/L for the group with the addition of red mud of 16%. Based on the obtained mechanical strength and alkali release analysis, the sample B24R16 was selected as the optimum among all tested groups. This study explored a way to reuse aluminum industrial waste, and the results are expected to be applied to roadbed and mining filling.
Highlights
Red mud and bauxite tailings mud are aluminum industrial wastes
With the increase in global alumina production capacity, large amounts of aluminum industrial waste are produced every year [6,7], and aluminum production enterprises need a lot of land to store aluminum industrial waste, which has a huge impact on land resources and the natural environment [8,9]
The microstructure of foamed lightweight soil was tested by SEM; before the test, the samples were cut into 6 mm × 4 mm × 2 mm slices by a geotechnical knife and dried; and the samples were sprayed with gold for further use (Table 4)
Summary
Red mud and bauxite tailings mud are aluminum industrial wastes. Bauxite tailings mud is the water-bearing residue of bauxite raw ore (shallow clay ore) after grinding and washing [1]. As red mud contains soluble alkali [4,5], the leaching of soluble alkali under the action of precipitation will cause pollution to the surrounding environment, which seriously limits the application of red mud in engineering, resulting in an extremely low utilization rate of red mud. In the process of utilization of red mud, in addition to considering mechanical properties, durability, and other conditions, the impact of the release of soluble alkali in red mud into the surrounding environment is of great significance. The application of red mud in building materials is currently a research hotspot in red mud reuse and an important way to absorb red mud [10–12]. If the feasibility of combining bauxite tailings mud and red mud to develop building materials is realized, it would make sure the reuse of the two wastes and further reduce environmental hazards. It is shown that red mud contains more Na2O, which can provide hydroxide radicals for the hydration process
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