PROSPECTS FOR THE USE OF BENTONITE IN THE PRODUCTION OF LIGHTWEIGHT CERAMIC AGGREGATES

ABSTRACT

The presented scientific work presents the results of a comparative study of bentonite clay samples from the Khojakul deposit of the Republic of Karakalpakstan, in order to assess their suitability as a raw material base for the production of ceramic gravel. The results of complex analysis, including the determination of chemical composition and X-ray phase analysis of the studied material are described. The content of montmorillonite, quartz and other associated minerals was quantitatively assessed. On the basis of the obtained data conclusions about mineral homogeneity and chemical stability of the studied raw materials were made. The key physical and chemical parameters affecting the technological properties of bentonite clays of Khojakul deposit were established.

АННОТАЦИЯ

В представленной научной работе приведены результаты сравнительного исследования образцов бентонитовых глин Ходжакульского месторождения Республики Каракалпакстан, с целью оценки их пригодности в качестве сырьевой базы для производства керамического гравия. Описаны результаты комплексного анализа, включающего определение химического состава и проведение рентгенофазового анализа исследуемого материала. Проведена количественная оценка содержания монтмориллонита, кварца и других сопутствующих минералов. На основании полученных данных сделаны выводы о минеральной однородности и химической стабильности исследуемого сырья. Установлены ключевые физико-химические параметры, влияющие на технологические свойства бентонитовых глин Ходжакульского месторождения

Keywords: bentonite, montmorillonite, expanded clay gravel, chemical analysis, X-ray analysis, properties, thermal insulation.

Ключевые слова: бентонит, монтмориллонит, керамзитовый гравий, химический анализ, рентгенофазовый, свойства, теплоизоляция.

Introduction.  Modern requirements to construction materials necessitate the development of effective and economically feasible solutions in the production of light porous aggregates. One of such materials is expanded clay, characterized by low density, high strength and good thermal insulation properties. The main raw materials for its production are traditionally clay rocks with suitable physical and chemical characteristics [3-4].

In recent years, the use of bentonite clay as an alternative raw material component for the production of expanded clay [7]. Bentonite is characterized by high plasticity, dispersibility and content of montmorillonite phase, which can have a positive effect on the quality of the final product. However, for industrial applications, a comprehensive analysis of its chemical and mineralogical properties and thermal behaviour is required [1-2].

The purpose of this study is to evaluate the suitability of bentonite clays of Khojakul deposit of the Republic of Karakalpakstan as a raw material for the production of expanded clay gravel. The paper presents the results of chemical and X-ray phase analysis, and also considers the main technological parameters that determine the potential of this raw material in expanded clay technology [10]

Research materials and methods. Bentonite clay samples taken from the Khojakul deposit located in the Republic of Karakalpakstan were used as an object of research. 

To determine the mineralogical composition of bentonite clay samples, the method of X-ray phase analysis was applied, performed by powder method on X-ray diffractometer Shimadzu LABX XRD-6100 (Japan) using monochromatic radiation CuKα. X-ray diffraction surveys were carried out with a scanning step of 0.02° at the tube operating parameters: current - 30 mA, voltage - 30 kV. The results of X-ray phase analysis showed that the mineral composition of the studied samples is represented mainly by montmorillonite, with admixtures of quartz, feldspar and traces of chlorite. The predominance of montmorillonite indicates a high degree of bentonitization of clay, which is a positive factor when using the material as a porous component in the production of expanded clay.

The chemical composition of the samples was determined by the method of accelerated chemical analysis, which provides a prompt and reliable assessment of the content of the main oxide components [8]. The analysis was carried out for the presence and quantitative content of basic oxides (SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, K₂O, Na₂O, etc.) that characterize the raw material in terms of suitability for expanded clay production.

The complex interpretation of the obtained data indicates a high clay component, low carbonation and satisfactory mineralogical composition of bentonites of the Khojakul deposit. The established physical and chemical parameters allow us to consider the studied raw materials as promising for production of expanded clay gravel with good thermal insulation and mechanical characteristics.

Results and discussions. The results of analyses of chemical composition of a number of samples of basalt of Khojakul (KhojB) deposit are presented in Table 1.

Table 1.

Chemical composition of bentonite clay samples from the Khojakul deposit

As can be seen from the data, bentonitic clays of Khojakul deposit are characterized by increased content of silicon dioxide (SiO₂), the average value of which is 54.83 %. Such a level of SiO₂ content brings them closer to andesites in chemical composition, which may contribute to the formation of a denser and stronger microstructure during heat treatment. A significant content of aluminium oxide (Al₂O₃) - up to 17.87 % - was also found, which causes an increase in heat resistance and strength characteristics of the material. The concentration of iron oxide (Fe₂O₃) varies in the range of 7.41-9.84 %, which corresponds to a moderate level, permissible for claydite production [9].

Figure 1. X-ray image of bentonite clays of Khojakul deposit

Mineralogical composition of investigated bentonite samples of Khojakul deposits was established by methods of X-ray phase analysis, the results of which are shown in Fig.1.

The X-ray diffraction [5-6], reflections corresponding to the minerals, quartz (SiO2) are observed in the X-ray diffraction pattern of bentonite clay samples: (d=0.443; 0.369; 0.364; 0.332; 0.317; 0.222; 0.197; 0.181; 0.166; 0.153; 0.137 nm); Montmorillonite (Na,Ca)₀.₃(Al,Mg)₂Si₄O₁₀(OH)₂-nH₂O): (d=0.746; nm); and minor amounts of calcite (CaCO3): (d=0.421; nm) and illite (K₀.₆₅Al₂(OH)₂(Si₃.₃₅Al₀.₆₅)O₁₀): (d=0.399; 0.396; 0.255; 0.212; nm).

Conclusion. As a result of the conducted complex research of bentonite clay of Khojakul deposit it is established that this natural material has a favourable chemical and mineralogical composition for use in the production of expanded clay.

X-ray phase analysis confirmed the presence of montmorillonite as the main mineral phase, as well as the presence of quartz, illite, feldspars and insignificant amounts of iron and titanium-containing minerals. The identified mineral components and their ratio meet the requirements for clay raw materials used in the technology of porous ceramic materials production. Thus, bentonite clays of Khojakul deposit can be recommended as a promising local raw material for the production of expanded clay with high performance characteristics.

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