The use of red mud in the construction industry materials.



The possibilities of utilizing red mud from aluminum production waste, the features of their application in the production of building materials based on hydraulic binders, were studied. The possibility of using sludge in the form of agglomerate as additives in concrete has been established.

Key words: red mud, agglomerate, industrial waste, recycling, additive in concrete.

As a result of the operation of aluminum smelters, waste is generated, consisting mainly of oxides of iron, aluminum, titanium and other useful metals. These wastes, called “red mud”, are finely ground wastes containing a large amount of valuable components, the recovery of many of which can be cost-effective. Currently, the amount of waste accumulated (due to the lack of efficient recycling technology) amounts to hundreds of millions of tons. Sludge fields occupy tens of thousands of hectares of land in the area of ​​operation of alumina production. Utilization of these wastes is not only an effective means of reducing the anthropogenic impact on the environment, but also seems economically attractive, since a distinctive feature of red mud is a significant content of metal oxides in them (up to 50 %) and rare metals

Research on the processing of red mud is carried out all over the world and hundreds of ways for their disposal have been developed. In recent years, the number of publications on the topic of red mud recycling has increased significantly. Despite numerous studies, so far only a small part of the red mud is processed, due to the low profitability of most technologies, high capital costs for the development of new ones and the complexity of the sale of products

The multicomponent composition of these wastes allows their use in various industries [1–10].

There are many critical reviews in the literature on methods for processing red mud, both considering all areas of their application [3–6] and describing specific areas, for example, using them for cleaning pollutants [7], extracting metals from them [8], pyrometallurgical processing [9], use in construction [10].

One of the most areas of industrial waste disposal is their use in the production of building materials, which allows up to 40 % to satisfy the demand for raw materials, this most important industry.

As scientific studies have shown, the use of red mud is possible as: additives for agglomeration, pelletizing, blast-furnace smelting of iron ores, raw materials for producing iron, a slag-forming agent for refining cast iron and steel, a partial substitute for clay in the manufacture of foundry molds, additives in the production of cement and ceramics, additives in the production of building bricks and refractories, as a basis for mineral fertilizers [11]

A promising direction for the disposal of alumina production waste may be their use in the production of building materials based on hydraulic binders [12,13]

The aim of the research is to study the possibility of utilizing red mud in the form of agglomerate in the technology for producing concrete. To obtain experimental data, red mud was used, which is a waste of the Ganja Alumina Refinery. In its composition, red mud is a fine fraction of mineral residues and contains residual compounds formed in the production process.

To reduce the content of harmful impurities in the red mud sinter, redox sintering should be carried out at a temperature of 1100–1200 ° C, this provides a product with a reduced alkali content of 58–60 %, sulfur by 31–38 % and phosphorus by 10- 15 %.

Quantitative dependences of the degree of removal of harmful impurities of sulfur, phosphorus and alkalis from red mud from temperature and time of heat treatment are established.

The obtained scientific results supplement the existing theory of sintering of finely dispersed ores and materials in the field of kinetics and the mechanism of formation of a multiphase sinter binder in a system of bauxite minerals with their fine germination.

A feature of red mud as a material for agglomeration is not only its fineness, but also its extremely high moisture capacity: about 35 %. From the red mud during the formation of the strength structure, a high-quality agglomerate is obtained. It has a large-porous, nosmature physical structure.

Preliminary experiments have shown that the use of agglomerate from red mud is advisable in the form of additives in concrete.

Experiments on the selection and determination of the composition of samples of building materials. The selection of the composition of building materials was carried out empirically, based on research data

The chemical composition of the agglomerate after sintering is shown in table 1. During the agglomeration of red mud, sulfur and alkali are removed by about 40–50 %.

Table 1

The chemical composition of sinter from red mud,%

Fegen	Al2O3	SiO2	CaO	Na2O	TiO2	Sgen	Pgen	V2O5	Ignition loss
46.11	22.35	11.33	7.27	3.2	6.5	0.4	0.71	0.63	1.5

The following ingredients were used as materials for the manufacture of concrete samples: sand, cement, red mud sinter, and water

The composition of sample 1 on the dry component included: 30 % cement and 60 % sand. As materials for the production of concrete sample 1, 60 g of sand was taken as a fine-grained aggregate, 30g of cement as a binder, and water was required. The dry components were mixed together.

The composition of 2 samples on the dry component included: 30 % cement and 60 % agglomerate.

Table 2

Shows the composition of concrete mixtures

№	1	2
Unit	gr
Cement	30	30
Sand	60
Agglomerate		60
Water	15	17

With the same composition, concrete mixtures with fine sand showed a smaller cone spread, the Agglomerate has a greater water absorption due to a rough surface and cracks in the grain, as a result of which the concrete mixture on the sinter is more rigid than on natural sands, the mobility of the concrete mixture sharply decreases compared to the mobility of the mixtures on natural sands, data are shown in table 3

The prepared mixture was placed in detachable metal molds, then compacted on a vibrating platform, after which the prepared concrete samples were stored in molds for 24 hours under wet conditions. The test result is affected by the size and shape of the samples, so they are strictly observed. After a day, concrete samples are removed from the molds, after which they were stored for 7, 14 and 28 days under normal hardening conditions.

Strength characteristics of concrete samples were determined in accordance with the requirements of GOST.

Table 3

Concrete strength

Age of				№
Samples	1		2
		Compressive strength, Rst, МPа
7 day.	30,1		40,6
14 day.	45,7		48.5
28 day.	48,0		50,7
120 day.	52,8		56.7

According to test results, the strength of concrete samples on agglomerate is higher than the strength of samples on sand.

The activity of the agglomerate depends on the composition, as well as on the size of its particles and the length of stay in the high temperature zone.

In the production of concrete, mineral fillers are widespread. Their classification and application are regulated by relevant standards. So, a dispersed inorganic additive of natural (limestones, dolomitic limestones, dolomites, sandstones, etc.) or technogenic origin (slags of metallurgical industries, sludges, ash, etc.) introduced into the mixture during their preparation for the purpose directional regulation of their construction and technical properties of concrete and giving them new properties.

Thus, the use of agglomerate from red mud as additives to concrete can improve its quality and to a large extent utilize harmful production waste.

References:

1. Tsakiridis P. E., Agatzini-Leonardou S., Oustadakis P. Red mud addition in the raw meal for the production of Portland cement clinker // Journal of Hazardous Materials. 2004. Vol. 116. No. 1–2. P. 103–110.
2. Cakici A. I., Yanik J., Karayildirim S. U. T., Anil H. Utilization of red mud as catalyst in conversion of waste oil and waste plastics to fuel // Journal of material cycles and waste management. 2004. Vol. 6. No. 1. P. 20–26.
3. Power G., Grafe M., Klauber C. Bauxite residue issues: I. Current management, disposal and storage practices // Hydrometallurgy. 2011. Vol. 108. No. 1–2. P. 33–45.
4. Klauber C., Grafe M., Power G. Bauxite residue issues: II. Options for residue utilization // Hydrometallurgy. 2011. Vol. 108. No. 1–2. P. 11–32.5
5. Grafe M., Power G., Klauber C. Bauxite residue issues: III. Alkali nity and associated chemistry // Hydrometallurgy. 2011. Vol. 108. No. 1–2. P. 60–79
6. Grafe M., Klauber C. Bauxite residue issues: IV. Old obstacles and new pathways for in situ residue bioremediation // Hydrometallurgy. 2011. Vol. 108. No. 1–2. P. 46 –59.
7. Liu Y., Naidu R., Ming H. Red mud as an amendment for pollutants in solid and liquid phases // Geoderma. 2011. Vol. 163. No. 1–2. P. 1–12.
8. Liu Y., Naidu R. Hidden values in bauxite residue (red mud): recovery of metals // Waste Management. 2014. Vol. 34. No. 12. P. 2662–2673.
9. Пирометаллургическая переработка комплексных руд / Л.И. Леонтьев, И. А. Ватолин, С. В. Шаврин, И. С. Шумаков. – М.: Металлургия, 1997. — 432 c.
10. Lima M. S. S. etс. Red mud application in construction industry: review of benefits and possibilities // IOP Conference Series: Materials Science and Engineering. 2017. Vol. 251. P. 1–10.
11. Ахметбек, А. Н., Касенов, А. Ж. Возможность использования красного бокситового шлама в строительстве // Образование и наука без границ. — 2017.Т.12. — С. 64–67
12. Баженов Ю. М., Шубенкин П. Ф., Дворкин Л. И. Применение промышленных отходов в производстве строительных материалов. Москва:Стройиздат, 1986. 54 с.
13. Саидов Д. Х., Умаров У. Х. Влияние минерально-химических добавок на коррозионностойкость цементных бетонов с применением промышленных отходов // Инженерный вестник Дона, 2013, № 2