No 1-2 (2025)

The Bazhenov chrysotile-asbestos deposit, located in the Sverdlovsk region. It is the world richest in reserves, unique in the breadth of fiber set in length and strength, without harmful to human health fibers of crocidolite and tremolite. It is difficult to overestimate its importance for the region’s economy and industry. Due to the Bazhenov deposit discovery owes the city of Asbestos was build, which arose next to the quarry, also many enterprises of the building materials and asbestos products appeared.

The problem hidden inside the calculation of compressed reinforced concrete columns in accordance with the requirements of SP 63.13330.2018 “SNiP 52-01–2003 Concrete and reinforced concrete structures. The main provisions” regarding the calculation of the conditional critical force. Despite the fact that concrete, which is part of reinforced concrete, is an elastic–viscoplastic building material, which has physical nonlinearity and nonlinear creep even at low loading levels (from about 20% of the prismatic strength of concrete), the calculation of compressed columns is based on postulates and formulas applicable to absolutely elastic rods that are loaded they work according to Hooke’s law.It is revealed that the conditional critical force used for reinforced concrete columns is the critical Eulerian force, designed to calculate rods made of absolutely elastic material for stability during longitudinal bending, as evidenced by solving the problem of stability of an elastic rod pivotally supported at the ends, loaded with a longitudinal compressive force.This solution is the basis for the calculation of reinforced concrete columns for stability. Formulas are derived by which, when calculating columns according to an undeformed scheme, the effect of deflection on their bearing capacity is taken into account.It is shown how the eccentricity of the longitudinal force applied to the column is taken into account, and the assumptions that apply in this case are given. It was revealed that when determining the conditional critical force according to SP 63.13330.2018, the stress–strain diagram normalized by SP 159.1325800.2014 “Reinforced concrete superstructures of highway bridges. Calculation rules”, is not taken into account. These provisions confirm the need for further investigation of the identified problem.

One of the trends in modern construction is the use of highly dispersed additives to produce Ultra-High Performance Concrete in terms of both strength and durability, especially for high-rise construction projects. The durability of concrete is determined by two main parameters – the reactivity of the cement stone components in relation to an aggressive environment and the permeability to an aggressive environment. The article discusses the use of finely dispersed calcium carbonate as an additive that increases the durability of concrete in general, and sulfate resistance in particular. The mechanism of action of calcium carbonate is based on a combination of the effect of a micro filler and chemical interaction with Portland cement minerals. Calcium carbonate interacts with the hydration products of tricalcium aluminate, reducing the amount of C₃A available for interaction with gypsum, followed by the formation of the main destructor when exposed to sulfates, ettringite. Calcium carbonate at high dosages reduces the strength of concrete. To correct this negative effect, it is proposed to use nanoscale calcium carbonate along with the already widely used micro-sized CaCO₃. The use of nanoscale calcium carbonate increases the total reaction capacity of the introduced additive, while reducing its total amount and, thus, preventing a decrease in concrete strength with a significant increase in its sulfate resistance. Nanoscale calcium carbonate densify the zone of interfacial interaction at the “cement matrix – filler” boundary, forming complex compounds with cement monominerals, which is confirmed by the data of physico-chemical studies. To further enhance the durability of concrete, the combined use of finely dispersed calcium carbonate with silica is proposed in order to bind free lime into low-base calcium hydrosilicates.

Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) exhibits exceptional axial tensile strength and a plastic fracture behavior distinct from conventional fiber-reinforced concrete. This distinction arises from a strain-hardening phase, characterized by the formation of multiple, uniformly distributed microcracks and an increase in tensile stress beyond the cracking threshold. This study investigates the axial tensile performance of UHPFRC specimens reinforced with varying types and volumetric contents of fibers. Brass-coated corrugated steel fiber with length-to-diameter ratios of 15/0.3 mm and 22/0.3 mm, along with straight fiber with a ratio of 13/0.2 mm, were employed as dispersed reinforcements, with fiber content ranging from 1% to 3% by volume. The findings reveal that neither fiber type nor content significantly influences the cracking stress. However, the maximum tensile stress and fracture energy demonstrate a linear increase with the fiber factor, which integrates fiber volume fraction and geometric characteristics. For equivalent fiber factor values, both corrugated and straight fibers exhibit similar tensile stress, but corrugated fibers contribute to higher fracture energy. Based on the experimental results, an equation was derived to determine the minimum required fiber volume, given specific geometric properties, to achieve strain-hardening behavior under axial tension.

In modern architectural and design solutions for buildings appearance formation facades external finishing with fine-grained concrete (FGC) based on composite gypsum binders (CGB) continues to gain popularity instead of traditionally used Portland cement. These materials have significant advantages in regulating their setting time and hardening speed. At the same time it is necessary that FGC based on CGB provide increased strength, water resistance and frost resistance, and their surface has water-repellent (hydrophobic) properties. The article presents the results of experimental studies of the physical and mechanical characteristics of the developed fine-grained concretes based on composite gypsum binders with a mineral additive of highly active metakaolin VMK-45 and a complex of organic additives – SP Melflux 1641F + RPP Vinnapas 8034H. The results of performed studies allow us to assert that the developed water-resistant and frost-resistant MZB based on KGV class B22.5 with a hydrophobic surface can be used for external finishing of buildings and structures facades. The water-repellent properties of the hardened MZB surface are manifested mainly due to the use of a chemical additives complex, which action principle is based on combination of electrostatic and steric repulsion, effect achieving with the help of lateral hydrophobic polyester chains of molecules, creating a protective hydrophobic film.

To evaluate effectiveness of mechanical activation of mineral powder applied as a mineral additive for building materials structure formation control it is proposed to use two characteristics: the ratio of coefficients k_a/k_s and the surface fractal dimension D_s. Proposed mathematical algorithm allows us to characterize dispersed systems by changes in the energy properties of a surface of particles directly involved in the process, and to calculate the fractal dimension of the surface formed with grinding. The adequacy of the proposed model was tested on highly dispersed powders of quartz sand and saponite-containing material isolated from a recycled water suspension of kimberlite ores processing. It is shown that for the studied systems raw materials the 30-minute duration of mechanical dispersion process on a planetary ball mill leads to a significant change of the substance surface properties, and the fractal dimension was 2.36 for quartz sand and 2.46 for saponite-containing material. It is also shown that the traditionally used criteria for evaluating effectiveness of raw materials mechanical grinding on parameters specific surface area and particle size parameters are important, but insufficient. The developed model of mechanical activation, which uses treated substance various constants, establishes the relationship not only between the total number of bonds broken during processing and the number of bonds that change surface properties (the ratio of coefficients k_a/k_s), but also takes into account changes in the surface geometric characteristics.

The conducted research and analysis of foreign experience showed that the most effective method of combating the adhesion of rocks to working surfaces is their lining with anti-adhesive and easily replaceable polymer plates. Thus, at the pelletizing plant of pelletizing factory of JSC Mikhailovsky GOK, as a result of the conducted research, the classification of polymer anti-stick lining plates (PASLP) was adopted, namely: PASLP HP (high pressure) SD (standard design); PASLP LP (low pressure) SD (standard design); PPFP IWR (increased wear resistance and impact resistance); PPFP HWR (high wear resistance and impact resistance). In the last 35 years, the following sheet materials have been recommended on the Russian market for various purposes: LDPE, HDPE, PP, PPFP-ASTIKI, PPL-EI, PPL-UI(CBM), Supralen1000, Tivar1000, VMPE 500, SVMPE1000, SVMPE9000, PE500, PE1000, PE9000, lnkulen 100, 500, 1000, 9000. For the correct selection of such materials for specific mining and geological and mining-technical conditions of operation of various process equipment, methods tested in the open press are recommended, allowing the selection of PASLP (sheets) depending on the strength of rocks according to the scale of prof. M.M. Protodyakonov and determining the optimal sheet thickness for various operating conditions of the equipment. Positive experience in combating the adhesion of finely ground iron ore concentrate and raw materials to the working surfaces of the process equipment of the pelletizing plant of JSC Mikhailovsky GOK named after A.V. Varichev is recommended for wide implementation at related enterprises of the Kursk Magnitka Anomaly, as well as at similar enterprises in other sectors of the mining and processing industry.

The urgency of the problem of recycling polymer waste is increasing every year. It is promising to use thermoplastic waste as binders in polymer-mineral compositions for the production of small-piece construction products such as paving slabs, curbs, parking limiters, elements of landscape design, etc. Technical requirements for the compositions of polymer-mineral compositions, the properties of their products, test methods are not regulated. One of the most informative characteristics is static uniaxial compression tests. It is necessary to accumulate statistics on strength tests of composites based on secondary thermoplastics and develop mathematical patterns of the influence of sample size, primarily their thickness, on strength properties. Therefore, the work is aimed at improving the methodological aspects of assessing the compressive strength of polymer-mineral samples based on thermoplastic matrices. Crushed polymer waste of polyethylene terephthalate and polypropylene, a combination additive ethylene vinyl acetate, and limestone flour were used to make the samples. Samples of various thicknesses were made by pressing from hot mixtures, then their compressive strength was determined. As a result, a differentiated approach to the geometry of the samples is proposed, taking into account the peculiarities of their manufacture and the complexity of obtaining samples of exactly the same thickness. A linear basic dependence of strength on the thickness of the sample is obtained, and a method for calculating compressive strength from the experimental thickness of the sample to the control one is proposed. It is proposed to take the sample thickness of 4 cm as a control, by analogy with the current standards for cement composites. Using the basic dependence and the proposed conversion method, it is possible to design formulations of compositions using various powdered mineral fillers (filling degree of more than 50% by weight) and various thermoplastic wastes, combining rigid thermoplastic polyethylene terephthalate and polyolefins in compositions.

The paper considers the technology of obtaining non-oxidized bitumen by double cracking of oil residue, such as tar and fuel oil. The whole indicators of non-oxidized road bitumen are substantiated by comparative analysis with existing industrial technologies for producing petroleum-based road bitumen in accordance with GOST 33133–2014 “Public roads. Viscous petroleum road bitumens. Technical requirements”. It is concluded that it is important to preserve the molecular structure of bitumen as a percentage of such components as asphaltenes and maltenes. It is revealed that the molecular structure of oxidized and compounded bitumen is unstable due to the different sizes of asphaltenes, which reduces its technical characteristics. Modified bitumen with polymer additives is considered and a comparative analysis with non-oxidized bitumen is carried out, it is concluded that the modifiers only support the disturbed structure of bitumen, which leads to a short service life of the roadway. The stages of the double cracking process are described in detail. The material balance of the double cracking technology and the requirements for non-oxidized bitumen at the outlet in accordance with GOST 33133–2014 are considered. The socio-economic effect of the introduction of technology for the production of non-oxidized bitumen in the road industry is calculated. The master plan and visualization of the UPBN-50 industrial installation, located on the basis of the State Unitary Enterprise “DSU-3”, is presented.