PROSPECTS FOR INDUSTRIAL USE OF CONCRETE BASED ON MODIFIED SULFUR-CONTAINING BINDERS

ABSTRACT

This article discusses the improvement of the physical, mechanical and operational properties of composite materials modified with sulfur binder plasticizers used in the modern construction industry. The influence of plasticizers on the fire-resistant properties of composite materials has also been studied. In addition, based on an in-depth analysis of the literature, the importance of the type and size of fillers and their mixing technology in the formation of a structure with low porosity of a sulfur-binding composite material was studied. The article discusses in detail the method of obtaining a stable sulfur-binding composite material, preparing a solid filler, soaking the filler in an organic modifier, wetting and heating the filler with the modifier, mixing it with elemental sulfur and cooling. with the formation of a solid product.

АННОТАЦИЯ

В данной статье рассматривается улучшение физико-механических и эксплуатационных свойств композиционных материалов, модифицированных серными вяжущими пластификаторами, применяемых в современной строительной индустрии. Также было исследовано влияние пластификаторов на огнестойкость композиционных материалов. Кроме того, на основе глубокого анализа литературы изучено значение типа и размера наполнителей, а также технологии их смешивания в формировании структуры с низкой пористостью серовяжущего композиционного материала. В статье подробно рассматривается способ получения устойчивого серовяжущего композиционного материала, включающий подготовку твердого наполнителя, его пропитку органическим модификатором, смачивание и нагрев наполнителя с модификатором, смешивание его с элементарной серой и охлаждение с образованием твердого продукта.

Keywords: Sulfur concrete, modification, fiberglass, flint, dispersed aggregate, mechanical properties, flammability, thermal conductivity.

Ключевые слова: Серобетон, модификация, стекловолокно, кремний, дисперсный наполнитель, механические свойства, воспламеняемость, теплопроводность.

1. Introduction.

With the development of technology, most of the disadvantages have been eliminated. Thus, the addition of sulfur-binding plasticizers (in particular, polysulfides) not only increases the plastic properties of the alloy, but also helps reduce cracks, and additives in the form of dicyclopentadiene increase the fire resistance of these building materials [1-3].

The properties of sulfur-containing concrete are the result of its internal structure, which is currently being studied in great detail [4]. Without the addition of fillers, sulfur is a substance with a homogeneous structure (homogeneous), which means that its molecules are densely arranged relative to each other. In the presence of a filler, sulfur molecules fill the internal spaces of the studied binder by ‘attaching’ the filler molecules in such a way that the porosity in it is almost imperceptible (even under a microscope). The small porosity of sulfur-containing concrete largely depends on the areas of its application. [5]. This is due to the use of sulfur-containing concrete as the main material for waste storage, waste water collectors and other structures.

The main technological parameter in the production of sulfur concrete is the viscosity of the sulfur solution, because it determines such technological properties as the ability of mineral fillers to form a homogeneous mass. It is known that in composite building materials, the filler comes into contact with the binder over a significant area due to the improved surface area [6].

At the first stage of the interaction of the binder and the mineral filler, the surface of the mineral fillers and the surfaces of the ultrafine fillers are wetted. Therefore, in the production of sulfur concretes, the formation of the main structure occurs at the stage of mixing the filler with dissolved sulfur. In this case, during the cooling of sulfur, homogeneous crystals are formed on the surface of the mineral filler, the size of which is much lower than the amount of sulfur without filler [7]. At the optimal filling level, almost all sulfur is converted to a homogeneous fine crystalline state. The reduction of sulfur crystals not only determines the strength of the sulfur binder. A film of optimum thickness is formed around the filler grains.

In Saudi Arabia, the use of sulfur-sand-bitumen mixture for road construction works has allowed savings of 60 percent of funds compared to traditional asphalt concrete in terms of estimated costs of materials, labor and equipment. Although the cost of sulfur is a bit high in some European countries, where good quality aggregates are not available, using sulfur-sand-bitumen mixtures gives very good results [8-9].

2. Methods.

In the method of preparing sulfur concrete mixture, a mixture of aggregates consisting of 10 mm thick flint, 3 mm sand, preheated to 160 °C is placed in a heated forced-moving concrete mixer, mixed, sulfur mixture heated to 160 °C, iodine modifier is added and mixed, to the obtained mixture forms or the concrete is dropped into the placer. The composition of the sulfur concrete mixture by weight is as follows: basalt waste filler pebble 31.65-44.26 + sand 24.07-33.64%. Mix them for 1-2 minutes at a temperature of 160°C. The composition of the binder is sulfur 13.550-27.13, iodine 0.005-0.01, filler - thermal power plant ash 8.545-17.14. The binder and filler mixtures are mixed for 2-3 minutes at a temperature of 160°C.

A method of obtaining a stable sulfur binder composite material includes preparing a solid filler, soaking the filler in an organic modifier, wetting and heating the filler with the modifier, mixing it with elemental sulfur, and cooling to form a solid product[10-11]. The invention makes it possible to obtain stable and high-strength sulfur composite materials.

The method of obtaining a composite material with a stable sulfur binder includes the following operations:

- preparation of solid fillers in a group consisting of a combination of mineral fillers, slag, silicon sand, secondary products of industrial production.

- soaking the filler in an organic modifier with diesel oil prepared for the purpose of impregnating the filler and with dark petroleum oil containing catalytic cracking residue.

- wetting and heating the filler with a modifier in order to activate the surface of the filler with sulfur;

- powdered solid or dissolved elemental sulfur is added to the filler soaked in the modifier;

- optional solid sulfur is stirred to bind the filler soaked in the modifier with elemental sulfur at a temperature sufficient to melt;

- the liquid mixture is cooled until it takes the form of a solid product.

Technical sulfur, sulfur compound waste can be used to prepare sulfur concrete [12]. Dense rocks, artificial and natural porous materials, production waste (grinding grains of rock and sedimentary rocks) are used as inert fillers and fillers[13-14].

Sulfur binder production technology is simpler and cheaper than cement production technology. According to the results of production development, the production technology of sulfur binders has the following indicators compared to traditional methods with cement: energy consumption is reduced by 1.5-2 times; environmental safety of production is increased; capital costs for production organization are reduced by 40-50%; waste-free production is achieved; the cost is reduced by 1.5-2 times; the shelf life is significantly increased (almost without limitations).

3. Results and discussion.

To increase the fire resistance and properties of concrete materials based on sulfur-containing binders, polymer modifiers were proposed and their optimal conditions and physical-mechanical properties were studied.

It is known that the value and economic efficiency of innovations in the construction materials industry always increase when they can be solved simultaneously as a result of their use[15]. Concretes based on sulfur-containing binders are distinguished from ordinary heavy concrete by their small water permeability and water permeability, their ability to maintain their shape and strength in a short period of time, and their high resistance to corrosion. At the same time, there are certain negative properties that limit the use of concretes based on sulfur-containing binders, which are attributed to their low temperature (140 °C), thermal resistance and high toxicity in production [16-19]. In order to eliminate the main shortcomings of concretes based on sulfur-containing binders, to expand the fronts of their use, and to obtain constructive materials from them, the authors developed fire-resistant sulfur-containing concretes based on MB-100 modifiers (tables 1 and 2).

The technology of making concrete based on sulfur-containing binders is carried out according to the following: sand with a size of 4-5 mm, crushed stone with a size of 10-50 mm, sulfur in the required amount and modifiers that improve flammability and mechanical properties of the MB-100 brand are added and heated at a temperature of 1130-170 °С and at room temperature is cooled [20-21]. The composition of prepared concretes based on sulfur-containing binders is presented in Table 1.

Table 1.

Optimum composition of modified sulfur-based concretes

Table 2.

Properties of sulfur concrete prepared on the basis of MB-100 brand modifier

Based on the requirements of the current regulatory documents for determining the optimal amount of the MB-100 modifier, their physical-mechanical, chemical and thermophysical properties were determined for the selected compositions (Table 2).

Physical-mechanical, chemical and thermophysical properties of concretes based on sulfur-containing binders were determined on the basis of current normative documents (Table 2). The density of concretes based on sulfur-containing binders prepared on the basis of MB-100 modifier flammability-reducing compositions was achieved due to the addition of a certain amount of additives to the composition by approximately 1.5-2%

4. Conclusion.

It was observed that the compressive and bending strength indicators of sulfur-containing concrete prepared based on MB-100 brand modifier additives, which reduce flammability, increased by 3-4% compared to the strength of ordinary sulfur-containing concrete.

The effect of MB-100 modifier on the setting time of sulfur-containing concretes was not noticed, reaching the same time as conventional sulfur-containing concretes for 1.1 hours.

No changes were observed in the chemical resistance of sulfur-containing concretes based on MB-100 modifier brand flammability-reducing additives from the chemical resistance of traditional sulfur-containing concretes. MB-100 modifier, which was added to concretes based on sulfur binders to reduce their flammability, increased the thermophysical properties of concrete without changing physical-mechanical, chemical properties, and transferred the material from the combustible group to the difficult combustible group.

Acknowledgments.

This scientific work was conducted as part of the Uzbek-Turkmen international applied project ‘Development and investigation of properties of hydrophobic chemically resistant organ-mineral composite materials based on industrial waste’ (in accordance with agreement № AL-7623031217 dated April 1, 2024) funded by the Agency for Innovative Development of the Republic of Uzbekistan.

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