THEORETICAL FOUNDATIONS OF ORGANIZING THE DIRECTED CRYSTALLIZATION PROCESS IN OBTAINING HIGH-QUALITY CLINKER BRICKS FOR SPECIAL PATHWAYS

JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 76 THEORETICAL FOUNDATIONS OF ORGANIZING THE DIRECTED CRYSTALLIZATION PROCESS IN OBTAINING HIGH-QUALITY CLINKER BRICKS FOR SPECIAL PATHWAYS Djumaniyazov Z.B., Boltabayev D.Z., Yakubov Y.X., Kabulova G.B., Xo‘jyazov Sh.X. Urgench State University named after Abu Rayhan Beruni e-mail: [email protected] https://doi.org/10.5281/zenodo.17977053 Abstract. The process of clinker brick production is based on technological methods and the possibility of producing high-quality clinker bricks using rationally composed lightweight fusible clay raw materials and alumino-calcium industrial waste. During the firing process, the formation of anorthite imparts high chemical stability and mechanical strength to the product. These two indicators are key factors, forming the foundation for pathways and decorative exterior construction materials. Keywords: Clinker, ceramic, crystallization, oxidation-reduction, ceramic mass, firing, chemical stability, mechanical strength, coke powder, dissociation. ТЕОРЕТИЧЕСКИЕ ОСНОВI ОРГАНИЗАSИИ ПРОSЕССА НАПРАВЛЕННОЙ КРИСТАЛЛИЗАSИИ ПРИ ПОЛУЧЕНИИ ВIСОКОКАЧЕСТВЕННОГО КЛИНКЕРНОГО КИРПИЧА СПЕSИАЛЬНIХ ПРОИЗВОДСТВ АнноттаsиY. Клинкер g‘ишт ишлаб чиqариш жараёни, технологик усуллар ва раsионал таркибли енгил суyuqланувчан тупроqли хом ашёлар ва алyuмокалsийли саноат чиqиндилари негизида yuqори сифатли клинкер g‘ишт ишлаб чиqариш имкониyaтига асосланади. Пишириш жараёнида анортит hосил бо‘лиши билан маhсулотга yuqори кимёвий барqарорлик ва механик мустаhкамлик бахш eтилади. Бу иккала ко‘рсаткич асосий ко‘рсаткичлардан бо‘либ, йо‘лаклар ва ташqи безакбоп qурилиш маhсулотларнинг асосини ташкил eтади. Калит со‘злари. Клинкер, керамика, кристалланиш, оксидланиш-qайтарилиш, керамик масса, пишириш, кимёвий барqарорлик, механик мустаhкам, кокс кукуни, диссоsиyaланиш. MAXSUS ISHLAB CHIQARISH UCHUN YUQORI SIFATLI KLINKER G'ISHTLARINI ISHLAB CHIQARISHDA YO'NALTIRILGAN KRISTALLIZLANISH JARAYONINI TASHKIL ETISHNING NAZARIY ASOSLARI АннотаsиY. Проsесс производства клинкерного кирпича основан на технологических приемах и возможности получениya вiсококачественного клинкерного кирпича с использованием раsионально составленного легкоплавкого глинистого сiрya и отходов алyuмокалsиевой промiшленности. В проsессе обжига происходит образование анортита, которiй придает изделиyu вiсокуyu химическуyu устойчивост и механическуyu JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 77 прочность. Eти два показателya yaвлyayuтсya клyuчевiми факторами, составлyayushими основу длya дорожек и декоративнiх наружнiх строительнiх материалов. Клyuчевiе слова. клинкер, керамика, кристаллизаsиya, окисление-восстановление, керамическаya масса, обжиг, химическаya стойкость, механическаya прочность, коксовiй порошок, диссоsиаsиY. Introduction. The innovative policy pursued in our country necessitates the development of solutions aimed at improving the quality indicators of industrially manufactured products. In this context, many experts note that the quality indicators of clinker bricks used in construction do not meet the required standards. One of the types of materials that can be used as high-quality clinker bricks in construction is clinker brick itself, which is considered the highest quality material in terms of all its properties and characteristics. The process of clinker brick production is based on technological methods and the possibility of manufacturing high-quality clinker bricks using rationally composed lightweight fusible clay raw materials and alumino-calcium industrial waste. During the firing process, the formation of anorthite imparts high chemical stability and mechanical strength to the product. These two indicators are key factors forming the foundation for pathways and decorative exterior construction materials. To achieve these quality indicators, European construction material manufacturers have started implementing the dry grinding process of raw materials to improve product quality [1, 2]. As a result of grinding the bulk mixture, solid agglomerates break down, the mass partially becomes amorphous, and structural defects emerge. Consequently, new reactive particles are formed, improving the technological properties of the raw material [3]. During the grinding process of minerals, structural and chemical reformation occurs, altering the length and angles of interatomic bonds. A significant number of point defects, dislocations, and lattice deformations are observed in the mineral structure of the mass. Additionally, the breaking of bonds between structural fragments and the partial transition of the mass into an X-ray amorphous state can be detected. According to scientific studies by G.I. Storozhenko et al. [4] and Y.A. Korotkov and V.N. Sorokin [5], grinding the bulk mixture leads to a reduction in the size of its particles, an increase in the specific surface area, and simultaneously enhances the reactivity of the raw material during thermal processing. Methods and materials. Furthermore, based on theoretical knowledge, the primary process in the natural formation of feldspars is the chemistry of the melt, and its formation temperature can be applied in the production of construction materials. This can be utilized in the JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 78 synthesis of artificial plagioclase products, specifically in the firing process of ceramic materials to promote the formation of anorthite. According to research conducted by W.D. Kingery, when ceramic products are fired in oxidation-reduction environments, the ceramic mass achieves an optimal internal structure at approximately 100°C lower temperatures in a reducing atmosphere compared to an oxidizing atmosphere [6]. In the production of silicate materials, including ceramics and glass products, coal, anthracite, and coke are used to create reducing environments. The selection of these materials is based on factors such as their availability, cost, and environmental cleanliness. In our research, the possibilities of using coke powder as a reducing agent in clinker brick production were studied. Results and discussion. Coke powder is generated during the sorting of coke fuel used in the lime saturation process for gas production at the "Khorezmshakar" JSC enterprise. Currently, an average of 20–30 tons of this powder is produced daily, with its total volume exceeding 8,000 tons. Due to the lack of effective technological solutions for its utilization, this powder is being stored at the company's designated waste disposal site. Its technical description is given in Table 1 below: Table 1 Technical description of coke cookie № Sulfur content Moisture content Calorific value Ash content 1 up to 6.0–10.0 % up to 3.0–6.0 % 39,800 kJ 8,0-11,0 % The introduction of coke powder into the clinker brick mass provides multifunctional capabilities, which can be characterized as follows: – Coke powder has an organic nature and possesses heat-generating capability upon combustion. Since the coke powder added to the clinker brick mass is evenly distributed throughout its volume, its uniform burning ensures an even heat distribution within the clinker brick layers. – Within the fired mass layer, coke not only burns but also creates a reducing environment. In such an environment, the decomposition of certain components or their reduction to lower oxides increases the formation of the liquid phase. The generated liquid phase surrounds the refractory components, thereby accelerating the sintering process of the mass. The cooling of this system leads to densification and volumetric shrinkage of the clinker brick mass, ultimately enhancing specific properties of the final product in a positive direction. – The addition of coke powder to the clinker brick mass increases its plasticity to some extent. – The combustion of coke generates small amounts of gases, which increase the partial JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 79 pressure on each particle surface or contribute to its densification. This, in turn, positively affects the overall strength of the final product. – In loess-like rocks, the relatively high content of SiO₂, Al₂O₃, and CaO compared to other components plays a crucial role in their ability to participate in oxidation-reduction reactions. The carbon introduced through coke powder enhances the chemical interaction of these components, accelerating the reaction rate. The reduction of these components in the presence of carbon can be represented as follows: 1. SiO2 + C = CO2 + Si 2. 2Al2O3 + 3C = 3CO2 + 4Al 3. 2CaO + C = CO2 + 2Ca 4. Si + O2 = SiO2. 5. 4Al + 3O2 = 2Al2O3 6. 2Ca + O2 = 2CaO 7. 3SiO2 + 4Al = 3Si + 2Al2O3 8.SiO2 + 2Fe = Si + 2FeO We will calculate the isobaric-isothermal potentials for these reactions. At 298 K, the enthalpy values for the above reactions are: kJ/mol The isobaric-isothermal potential values for the reactions at 298 K are: =+4,5+51,06-1,3-9,9=+44,4 J/(mol∙K) If the average process temperature is 950°C (1283 K), then: -611,2 – (1223·0,044) = 665,01 Among the iron oxides present in loess-like rocks, only Fe₂O₃ is prone to thermal dissociation. In an oxidizing or neutral environment, the dissociation of this oxide begins at 1000°C. However, in a reducing environment, this process occurs at significantly lower temperatures, as previously noted [7]. JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 80 At high temperatures and in the presence of reducing agents such as C, CO₂, and H₂, the dissociation rate of iron oxides increases sharply. The dissociation rate of the process can be determined using the following formula: (4.1) Here, E – Activation energy, T – Temperature, A – Constant, R – Universal gas constant. The dissociation rate is influenced by several factors, including: – The adsorption of reducing agents or reaction products on the oxide surface, – The physical state of solid particles, – The release rate of gases formed within the mass, and others. Below 570°C, FeO is unstable and decomposes as follows: FeO → Fe3O4+Fe Above 570°C, the decomposition of iron oxides occurs as follows: Fe2O3→Fe3O4→FeO→Fe Below 570°C, the decomposition proceeds as follows: Fe2O3→Fe3O4→Fe The reduction of Fe₂O₃ in the presence of carbon proceeds as follows: C+O2→2CO Fe3O4+CO→3FeO+CO2 FeO+CO→Fe+CO2 In the reduction of iron oxides, various reducing agents such as CO, C, H₂, and other hydrocarbons can participate. Below 1000°C, CO remains stable and decomposes according to the reaction: CO ↔ C + CO₂ The resulting carbon deposits on the surface of loess-like rock particles. Above 1000°C, CO₂ and water vapor become stable. At high temperatures, heated carbon reacts intensely with CO₂ and water vapor, producing active reducing agents such as CO and H₂, which directly participate in the reduction of iron oxides. The reaction between carbon and water vapor proceeds as follows: JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 81 С+Н2О→СО+Н2 This process results in the formation of highly active FeO within the loess-like rock mass. This FeO reacts intensively with other components, leading to the formation of a liquid phase, which softens the mass. In a reducing environment, Fe₂O₃ reacts with CO, reducing to FeO, creating a reducing gas atmosphere in the kiln. Fine Fe₂O₃ particles give ceramics a yellowish color, whereas coarse Fe₂O₃ particles cause black spots on the surface. When ceramics are fired in a reducing atmosphere, fayalite (2FeO·SiO₂) forms earlier than in an oxidizing atmosphere. To ensure a reducing environment, up to 3% coke waste should be added to the mass. At this stage, FeO gives the ceramic a light bluish color. However, the CO concentration should not exceed 2-3%, as higher levels may result in soot deposits, which adhere to the product's surface. Fe2O3+СО Fe3O4+СО2 Fe3O4+СО FeO+СО2 FeO+ SiO2 2FeO*SiO2 Moreover, Fe²⁺ has a significant impact on the reconstruction of metaphase ions in subsequent stable phases. In systems based on loess rocks, the first and second reactions in an oxidizing environment, as well as the third reactions in a reducing environment, are expressed as follows [7]: 1) Al2O3*2SiO2= (3Al2O3*2SiO2) + SiO2; 2) Al2O3*2SiO2 + Fe2O3 = FeO*Al2O3+ (FeO*SiO2)+ SiO2+ O2; 3) Al2O3*2SiO2+ FeO = FeO* Al2O3+ (FeO*SiO2)+ SiO2; 4) Al2O3*2SiO2+ FeO = (FeO* Al2O3) + (3Al2O3* 2SiO2)+ SiO2; 5) Al2O3*2SiO2+CaCO3 + SiO2 = CaO* Al2O3* 2SiO2 +CO2. The calculations presented in the provided data indicate that, compared to Fe₂O₃ in an oxidizing environment, the presence of wüstite-FeO in a reducing environment accelerates the physicochemical interactions in loess-based masses. In the third reaction, the formation of hercynite (FeO∙Al₂O₃) and fayalite (2FeO∙SiO₂) involves FeO in the reducing environment, which is more reactive than Fe₂O₃ in the oxidizing environment. Additionally, FeO actively participates in the formation of mullite. However, the transformation of Fe₂O₃ into FeO becomes more complex due to evaporation processes within the mass. This factor is not particularly significant for ceramic products such as household and sanitary ware, but it is highly important for wall and pavement materials. In clays containing JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 82 CaCO₃, the formation of hercynite, anorthite, and mullite occurs more reliably and at an earlier stage in a reducing environment compared to oxidizing conditions. The decarbonization reaction of CaCO₃, MgCO₃, and dolomite manifests actively at different temperatures under varying pressures. For example, the presence of Fe₂O₃, TiO₂, SiO₂, and other components in clay and inorganic additives significantly influences the decarbonization rate of MgCO₃ at 650°C and CaCO₃ at 900°C during dehydration [8] (figure 1), as the participation of CaO and MgO can enhance the formation of a glassy phase. The CaO formed from the decomposition of CaCO₃ interacts with mullite in a reducing environment, leading to the formation of anorthite at temperatures above 900°C. The reducing atmosphere positively influences the acceleration of the anorthite formation reaction. It is known that anorthite, a framework-structured mineral with low CaO-to-SiO₂ ratios, differs significantly from other calcium-silicate compounds due to its superior chemical stability and mechanical strength. Figure 1. Scheme of the decarbonization reaction of CaCO3, MgCO3 and dolomite Accordingly, calculations were carried out in the CaO-Al₂O₃-SiO₂ system at temperatures ranging from 900°C to 1000°C, confirming the presence of anorthite, diopside, gehlenite, mullite, and wollastonite crystal lattices (figure 2). Due to the formation of numerous crystals in this system, ranging from simple oxides to ternary compounds, the probability of anorthite, diopside, gehlenite, mullite, and wollastonite minerals forming within the observed temperature range (900-1000°C) is significantly high. JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 83 Figure 2. Phase diagram in the CaO-Al2O3-SiO2 system The calculation of crystal lattice energy was carried out based on the formula proposed by A. E. Fersman. (4.2) Here, • W represents the valency of ions, • R denotes the radius of ions. The total energy of the crystal lattice of compounds is calculated using the following formula: I=253,1(eqА+ eqВ+ eqС+.....) (4.3) Here, A, B, C, D, N represent the number of ions in the crystal lattice. The total energy of the anorthite (CaO·Al₂O₃·2SiO₂) crystal lattice is calculated using the following formula: The unit structure energy of the crystal lattice in anorthite (Iан) (I'ан) is calculated using the following formula: Ian= I`an/ (Si2+Al2)=10585/(2+2)=2646 kcal/mol The total energy of the crystal lattice for gehlenite (2CaO∙Al2O3∙SiO2) is calculated as follows: I`gel=253,1(1,75х2+4,95х+8,60х1+1,55х8)=8358,4 kcal/mol Igel=I`gel/(Si+Al2)=8358?4/(1+2)=2786 kcal/mol The total energy of the mullite crystal lattice (3Al2O3∙2SiO2) is calculated based on the following formula: JOURNAL OF FOOD SCIENCE VOLUME 3, ISSUE 10, november 2025 ISSN: 2181-385X 84 I`mul=253,1(4,95х6+8,60х2+1,55х8)=15180,8 kcal/mol The unit structure energy of the mullite crystal lattice is calculated as follows: Imul=I`mul/(Si2+Al6)=15180,8/(2+6)=1897,6 kcal/mol For wollastonite, this value is equal to the following: I`wol=256,1(1,75х1+8,60х1+1,55х3)=3840 kcal/mol Бу холда, Iwol=I`wol=3840 kcal/mol In the complex mixture of CaO, Al₂O₃, and SiO₂ mentioned above, mullite crystallization occurs at temperatures below 900-1000°C. As the temperature increases, CaO interacts with mullite and separates in the form of anorthite. СаО+Аl2O3∙2SiO2= СаО∙Аl2O3∙2SiO2 In the production of high-quality clinker bricks, important factors for ceramic mass include the softening, solubility, viscosity, surface tension, and ability to form new structures of loess rocks under temperature influence. As noted in our previous scientific studies, loess rocks are complex multi-component mechanical mixtures that do not have a fixed melting point, as the crystal lattices of aluminosilicate minerals gradually break down under the influence of temperature. For this reason, determining the temperature at which the crystalline phase decreases and the liquid phase increases, as well as understanding the transition range of the material from a solid state to a pyroplastic state, is a crucial stage in clinker brick production. This range is referred to as the softening interval. When heating loess rock, an easily fusible compound is formed in the Na₂O-CaO-SiO₂ system, which has an eutectic point at 725°C. The Na₂O-SiO₂ system, on the other hand, has an eutectic point at 793°C. Similarly, the CaO-SiO₂ system also possesses an eutectic point. In the FeO-CaO-SiO₂ system, eutectic points at 1030°C, 1093°C, and 1117°C have been recorded under oxidizing conditions. However, scientific literature provides little to no information on phase transformations occurring in systems composed of SiO₂–Al₂O₃–CaO–FeO–Na₂O–K₂O under reducing conditions (figure 3).