METHOD FOR MODIFYING ROAD BITUMEN USING SULFUR AND METALLURGICAL WASTE

ABSTRACT

This article investigates a method for modifying road bitumen using sulfur and metallurgical waste. The main objective of the study is to improve the physicomechanical and operational properties of bitumen used in road construction, as well as to determine the possibilities of efficient utilization of industrial waste. The study analyzes the effect of adding sulfur and metallurgical waste to the bitumen composition on its structural properties, viscosity, softening temperature, and resistance at low temperatures. The experimental results show that the modified bitumen, compared to conventional bitumen, has higher strength, better resistance to deformation, and greater durability. In addition, it has been established that the use of metallurgical waste helps reduce negative environmental impacts and lower the cost of road construction materials. The obtained results have scientific and practical significance for improving the quality of road bitumen and ensuring the rational use of resources.

АННОТАЦИЯ

В данной статье исследован способ модификации дорожного битума с использованием серы и металлургических отходов. Основной целью исследования является улучшение физико-механических и эксплуатационных свойств битума, применяемого в дорожном строительстве, а также определение возможностей эффективного использования промышленных отходов. В ходе исследования проанализировано влияние добавления серы и металлургических отходов в состав битума на его структурные свойства, вязкость, температуру размягчения и устойчивость при низких температурах. Результаты проведённых экспериментов показали, что модифицированный битум по сравнению с традиционным обладает более высокой прочностью, устойчивостью к деформациям и большей долговечностью. Кроме того, установлено, что использование металлургических отходов способствует снижению негативного воздействия на окружающую среду и уменьшению себестоимости дорожных строительных материалов. Полученные результаты имеют научное и практическое значение для повышения качества дорожного битума и рационального использования ресурсов.

Keywords: road bitumen, modification, sulfur, metallurgical waste, asphalt concrete, physicomechanical properties, road construction.

Ключевые слова: дорожный битум, модификация, сера, металлургические отходы, асфальтобетон, физико-механические свойства, дорожное строительство.

Introduction. This article discusses the modification of bitumen with sulfur and metallurgical slag to improve its physical, mechanical, and performance properties. Experimental results show that adding these modifiers to bitumen improves its heat resistance, adhesion, and deformation resistance.

At the same time, the article reviewed the scientific work of several scientists on the modification of bitumen with sulfur and metallurgical slags to improve its physical, mechanical, and performance properties.

Bitumen is an organic binder widely used in road construction, waterproofing and industry, and its main drawback is that it softens at high temperatures and embrittles at low temperatures [1, 2].

Therefore, in recent years, scientific research has been conducted in the direction of improving bitumen with the help of various modifiers. One of them is the technology of modifying bitumen based on sulfur and metallurgical slag. In order to improve the physicochemical properties of bitumen, modified bitumen by adding sulfur and metallurgical slag, and to study the main parameters of the obtained product, road bitumen (grade BND 60/90), technical sulfur (S), and ferrous metallurgy waste - electric furnace slag (SiO₂, Fe₂O₃, CaO, Al₃O₃) were used in experiments [3].

The aim of the study is to develop a modified road bitumen composition based on sulfur and metallurgical waste, to determine its structural and rheological properties, to reduce its harmful environmental impact, and to design asphalt concrete mixtures using it, thereby substantiating the possibility of their application in road pavements.

Methods and materials. The modification process was carried out in 2 stages, the raw materials and their quantities in the modification are as follows:

The main mass - BND 60/90 in the modification process in the amount of 70-90% of the total mass;

Additives for modification - 1. Sulfur (S) - technical sulfur (waste of the MUBORAK oil and gas processing plant), in the range of 5-10% of the total mass;

2. Metallurgical waste (slag, MT) - electric furnace slag of the BEKOBOD metallurgical plant, crushed waste of the slag was used in the range of 5-20% of the total mass.

The following laboratory equipment was used for the modification and modified bitumen testing processes: thermometer, high-angle disperser or propeller-type mixer, laboratory oven, viscometer, penetrometer, Ring and Ball Apparatus, and Fraas Test Set.

The procedure was as follows:

Initially, 3 kg of BND 60/90 bitumen was placed in a 5-liter stainless steel heated reactor with a mixer and thermometer and heated to 160–170 °C, maintaining a uniform temperature using a thermostat with an accuracy of 0.1 °C. During the modification process, an inert atmosphere was provided (using nitrogen gas) to prevent oxidation of the raw materials and products under the influence of temperature.

After the mass temperature reached a steady state, metallurgical waste crushed to 60 μm (5, 10, 15, 20% of the total mass) was added to the reactor in several portions. The mixture was stirred at high speed (300 rpm) for 20–30 minutes to achieve complete homogeneity. At a temperature of 160–170 °C, metal ions in the waste form various physicochemical bonds with carboxyl and hydroxyl groups in the bitumen.

Then, the mass temperature was cooled to 120-130 °C, and sulfur was gradually added to the reactor in a specified amount (5%, 7%, 10% of the total mass) and mixed at high speed (600 rpm) for 15-20 minutes. At this stage, the mixing duration and temperature were controlled to ensure the chemical reaction and improved dispersion. Sulfur serves to ensure the stability of the aggregate and bitumen mass and prevents bitumen from aging.

The modification process lasts 1 hour and is stabilized at 120 °C for 2 hours. The mixing speed during the stabilization process is 60-70 rpm. Then the standard was sent for testing (penetration, softening point, viscometer, Fraas).

The proportions of the initial reagents in the modification process are given in Table 1 below.

Table 1.

Proportions of initial reagents in the modification process

** sample ID, percentages of S and MT

Results and discussion. The test results of modified bitumen in the above method were carried out. In it, the influence of the amount of initial reagents on the properties of bitumen was studied.

Table 2.

Properties of bitumen samples obtained after modification

As can be seen from the above results, when the amount of sulfur added to bitumen is 7% and metallurgical stone is 15%, sulfur forms chemical bonds in bitumen and increases their thermostability. And metallurgical stone serves as a mineral powder and a reinforcing agent, as a result of which bitumen's resistance to deformation increases.

Conclusion. Bitumen modified with sulfur and metallurgical stone has been proven to have the following advantages:

- Heat and cold resistance;

- High adhesion;

- Improved mechanical strength;

- Extended service life of road surfaces.

- Studies show that when 5-7% sulfur and up to 10-15% metallurgical stone are added to bitumen, the softening point increases from 46 °C to 58 °C, penetration decreases, and mechanical stability increases. This technology is environmentally friendly and allows for the recycling of metallurgical waste.

Sulfur forms sulfide bridges between bitumen molecules during polymerization, strengthening its structure [4].

Metallurgical aggregate, due to its finely dispersed structure, acts as a framework in bitumen, which helps to maintain its hardness at high temperatures. The combined effect of both modifiers expands the operating temperature range of bitumen from –6 °C to +60 °C.

The viscosity of bitumen modified with sulfur and metallurgical rock increased by 25-40%, and its temperature stability improved.

The decrease in penetration from 78 to 61 · 0.1 mm indicates the hardness of the bitumen. The Fraas brittleness temperature improved by 6 °C, i.e., the cold resistance increased. The proposed technology reduces bitumen consumption by 5-7% and is environmentally friendly, allowing the recycling of metallurgical waste.

References:

1. Z.Kh. Saidov "Road construction materials" Training manual Tashkent 1994.
2. B.K. Raupov, B.A. Mavlonov, S.A. Gaybullaev, "Operational properties of bitumens and their improvement" "Science and Education" Scientific Journal. September 2021 / Volume 2 Issue 9.
3. V.V. Yakovlev, Z.U. Asadullina "Асфальтобетоны на битумном вяжущем, полученном из отходов ремонта кровель" Bashkir Chemical Journal II. - 2011. - T. 18, No. 1.
4. I.G. Akbarov “Composition of modified composite bitumen materials based on local and secondary raw materials and development of technology for obtaining roofing felts for use in construction based on them” Abstract of the dissertation for the degree of Doctor of Philosophy (PhD) in Technical Sciences, Tashkent 2021, pp. 5-113.