PRODUCTION OF ASPHALT CONCRETE MIXTURES BASED ON MODIFIED BITUMEN AND STONES

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 133 PRODUCTION OF ASPHALT CONCRETE MIXTURES BASED ON MODIFIED BITUMEN AND STONES A.Sh. Safarov1, U.A. Safaev2, Bozorboyeva L.U3, F.Sh. Karimberdiev4, F.N. Rakhmatullaev5 Tashkent State Technical University, Faculty of Oil and Gas, Department of Ecology and Environmental protection1,2,3,4,5 https://doi.org/10.5281/zenodo.18041649 Abstract. The article is aimed at reducing slag waste in the metallurgical industry of our republic. This work studies the technology of producing asphalt concrete mixtures based on modified bitumen and stone-aggregate mixtures. The purpose of the research is to improve the durability, long service life and temperature resistance of road pavements by enhancing bitumen with various modifiers and optimizing the composition of stone-aggregate mixtures. During the study, the use of waste (slag heap) from the metallurgical industry to increase the durability of bitumen and to create road pavements resistant to hot and cold temperatures was analyzed. In addition, the proportion of stone materials of different fractions, their granulometric composition, and adhesion properties were examined, and an optimal asphalt concrete mixture composition was developed. The obtained results can be applied in road construction to create high-quality, long-lasting pavements. Keywords: bitumen, asphalt concrete, slag heap, stone-aggregate materials, metallurgical industry. Introduction It is known that the metallurgical industry, while bringing great benefits to the country, has a detrimental effect on the environment. One of the current pressing issues is solid waste from the metallurgical industry. As a result of many years of research and in-depth studies, a solution to this problem has been found. That is, a technology has been developed to produce road construction materials with high performance characteristics using solid waste, which is one of the pain points of the metallurgical industry. The main aspects that should be paid attention to when constructing a road, that is, when obtaining asphalt concrete, are the selection of a mixture with a constant granulometry of aggregate materials, this parameter guarantees high mechanical properties of the coating due to the compaction of large fractions by small fractions. Because the coating formed by mixing the mineral part of asphalt concrete with a continuous granulometry has high strength and stability. Table 1 shows the physical and mechanical parameters of the rock mixture, which is the main solid waste of metallurgy, and their suitability for practical use. Physical and mechanical properties of stone Table 1 № Indicator name Unit of measur e Test results Compatibility of results with MH MH requirement In practice 1 Grain content, 1,5 D % not allowed 0,0 fits SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 134 mm for S 3 category 1,25 D 0-10 9,0 fits D 0-15 14,9 fits 0,5 D 20-40 31,5 fits 5 45-70 58,5 fits 0,16 75-90 89,1 fits 2 The amount of dust and silt % Up to 3.0 2,5 fits 3 Amount of lumped clays % Up to 0,25 0,0 fits 4 Grindability grade % Up to 15-25 М 1000 17,5 М 1000 fits 5 Tissue density г/см³ - 1,97 - 6 Maximum density, wet г/см³ - 2,42 - 7 Maximum density, dry state г/см³ - 2,30 - 8 Optimum humidity % - 5,10 - 9 Reserve (density) coefficient - 1,17 - As can be seen from the table, the indicators of stone mixtures correspond to the indicators of natural materials used in practice for asphalt concrete. The physical and mechanical parameters of the sandy fraction in the stony mixture also correspond to the parameters of the natural sand used in practice (Table 2). Physico-mechanical properties of the sand in the stone Table 2 № The name of the indicators to be detected Unit of measure Test results Indicator matching MH requirement In practice 1 Grain compositio n 0,63 % Over 45 55,40 fits <0,16 Up to 10 8,90 fits 2 Magnitude module Over 2,5 2,68 fits 3 Amount of dust and silt particles, maximum % 5,0 3,50 fits The granular composition of the gravel mixture and the maximum density at optimal moisture are shown in Figures 1 and 2. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 135 Figure 1. The upper (1) and lower (2) limits of the required granularity and the granularity of the gravel mix (3). Figure 2. The maximum density of the stony mixture at optimal moisture According to the results of the research, the physical and mechanical properties of slag (slag) separated during the steel production process of "Uzmetkombinat" JSC GOST 3344-83 "Crushed stone and gravel sand for road construction. It complies with the requirements of the "Technical Conditions" standard. The grade of stone (stone) on the level of crushing is M1000. The bulk density is equal to 1.97 g/cm3. The maximum density at optimal moisture (moisture 5.1%) is equal to 2.42 g/cm3. In the dry state, it is equal to 2.30 g/cm3. In order to improve the physical and chemical properties of bitumen, which is the main binder in the preparation of asphalt concrete compositions, it is very effective to activate it in various ways or add active substances. From a technological point of view, it is recommended to reduce the viscosity of bitumen to enhance its adhesion to mineral materials. One of the effective ways to reduce the viscosity of bitumen is to modify it by adding surfactants. The physical and mechanical properties of the resulting compositions are largely related to the adhesion strength of bitumen with mineral fillers. During the scientific work, the development of modified bitumen compositions using activated secondary rock materials as fillers and their physical and mechanical properties were studied. The softening points of the compositions under the influence of temperature were determined by the Ring and Ball method, and the obtained results showed that the softening point of the rocky sand bitumen composition is significantly lower than that of ordinary sand (Table 3). Effect of bitumen content on the softening point of samples Table 3 SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 136 № Examples Time Ring and Ball Softening Point, °C Softening point of ring and ball, mm 1 Bitumen 1 hour 60 12.2 2 Sandy bitumen 2 hour 60 8.7 3 Coarse sand bitumen 5 hour 60 0.9 The brittleness temperature of the prepared samples was determined by the Fraas method. The essence of the method is that a sample of a cooling bitumen composition is periodically tested by bending, and as a result, the appearance of a crack in the sample or its fracture indicates the brittleness limit. The results obtained showed that the cold resistance of the bitumen composition is quite high (Table 4). Brittle temperature of samples at specified time Table 4 № Examples Time, seconds Decomposition temperature, °C 1 Bitumen 20 - 30 2 Sandy bitumen 20 - 38 3 Coarse sand bitumen 20 - 42 For many years, the main criterion for classifying bituminous binders in international standardization has been the measurement of penetration at 25 ° C. This indicator was determined by the depth of penetration of the needle into the bitumen sample with a needle load of 100 g and a load exposure time of 5 seconds. The results obtained are presented in Table 5. Penetration indicator in bituminous compositions Table 5 № Examples Penetration temperature°С Time, seconds Penetration, мм 1 Bitumen 25 5 32,5 2 Sandy bitumen 25 5 22,4 3 Coarse sand bitumen 25 5 10,2 Conclusion Based on the obtained compositions, asphalt concrete mixtures were prepared and their structure was studied. In particular, IR spectroscopy showed that additional C-S bonds were formed in the composition of stone, sulfur and road bitumen produced in the metallurgical industry and that they improve the physical and mechanical properties of the composition. That is, the results of the experiment confirmed that the composition formed during the preparation of sulfur, rock, and bitumen asphalt concrete increased in strength, ductility, and resistance to hot and cold conditions. Considering that the construction and repair of roads in our country is currently a very global issue, we can cover the roads with high-quality, durable, and most importantly, secondary asphalt concrete obtained from local raw materials. The main secondary raw materials are solid waste from the metallurgical industry, i.e., gravel, sulfur and bitumen from the oil and gas industry. The strength, quality and other characteristics of the asphalt concrete composition obtained on the basis of these substances fully meet the technical requirements of GOST 9128-97 “Asphalt concrete mixture and asphalt concrete for roads and airfields”. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 12 DECEMBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 137 REFERENCES 1. Kh. Koldoshev "Production of construction materials based on industrial waste" training manual, Samarkand 2017. 2. Tarasevich B.N. "Main Classes of Organic Compounds in the IR Spectrum". Information materials. Moscow 2012. 3. R. Khakimov M. Boydedaev “Development of a technology for obtaining modified asphalt concrete mixture” Science and Education" Scientific Journal. April 2021 / Volume 2 Issue 4. pp. 227-231. 4. Inatova M. S., Murodova D., Khamraeva M. 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