Recycling red mud from the production of aluminium as a red cement-based mortar

Abstract

Current management for red mud is insufficient and a new method is needed. A series of experiments have been carried out to develop a new approach for effective management of red mud. Mortars without or with 3%, 6% and 9% red mud were prepared and their fresh and hardened properties were measured to access the possibility of recycling the red mud in the production of red cement-based mortar. The mechanisms corresponding to their mechanical performance variations were explored by X-ray powder diffraction and scanning electron microscopy. The results show that the fresh mortars with red mud present an increase of viscosity as compared with the control. However, little difference is found when the content of red mud is altered. It also can be seen that red mud increases flow time and reduces the slump flow of the mortar. Meanwhile, it is found that mortar with red mud is provided with higher air content. Red mud is eligible to adjust the decorative mortar colour. Compressive strength of mortar is improved when less than 6% red mud is added. However, overall it has a slightly negative effect on tensile bond strength. It decreases the Ca(OH) content and densifies the microstructure of hardened paste. The heavy metal concentrations in leachates of mortars with red mud are much lower than the values required in the standard, and it will not do harm to people's health and the environment. These results are important to recycle and effectively manage red mud via the production of red cement-based mortar.

Metal matrix production: Casting of recycled aluminum cans and incorporation of rice husk ash and magnesium

“…Essentially, it is the process of extracting alumina from bauxite. 14 Through the Hall–Heróult process, alumina is processed and then metallic aluminum is extracted. Approximately 5 kg of bauxite is required to produce 2 kg of alumina and 1 kg of primary aluminum.…”

Comparative study on durability of binary geopolymer concrete

“…The derivative thermo gravimetry (DTG) peak related to Portlandite decomposition became clear after 12h of aging was explained by [29], but not until 28 days. The increasing in compressive strength was observed by substitute the 6% of the red mud in concrete was discovered by the [30]. This might be due to microstructure solidification, as seen by a reduction in Ca(OH) 2 concentration with red mud replacement.…”

Development of a mineral binding material with elevated content of red mud

“…Among other multi-tonnage wastes, red mud attracts attention as a byproduct of processing bauxites into alumina by the Bayer's method in nonferrous metallurgy [7,[11][12][13][14][15][16][17][18][19][20][21]. Employing the indicated industrial method, during treatment of bauxites with caustic soda, approximately 35-40 % of the original ore are wasted, forming alkaline red mud with a concentration of solid phase at 15-40 %.…”

“…This is shown by relevant development in the production of ceramics with plastic formation, including chemically resistant, ceramic tiles and finishing materials [17,18]. Regarding the development on the use of red mud in cement technology, it is mainly related to the introduction of a small amount of 3-5 % by weight of this waste into raw material blends as a correcting iron-containing additive in accordance with the regulated standards for existing production [19][20][21].…”