Increased Frost Resistance Research Articles

Comparative study on the effect of crystalline agents for improving frost resistance of concrete from the perspective of reaction mechanism

The crystalline agents can be used to improve the concrete frost resistance by its densification effect on the microstructure of concrete, while the effect of which depends on the type and penetration process of the crystalline agents. This study, therefore, aimed to investigate the effect of two types of crystalline materials, in terms of organic and inorganic one, and two kinds of penetration methods including surface coating and soaking, in concrete. In addition to freeze-thaw test and electric flux test, the thermal gravity analysis, mercury intrusion porosimetry and scanning electron microscope were carried out. The results showed that after vacuum drying and soaking treatment, the material’s penetration depth has reached 7 mm. Deeper penetration depth shifted the freeze-thaw failure mode sudden to gradual, significantly enhancing frost resistance as a result. Among them, organic crystalline agent increased frost resistance by 2.5 times and decreased electrical flux by approximately 90 %, while inorganic crystalline agent only enhanced frost resistance by 1.5 times and reduced electrical flux by only about 37 %. From a reaction mechanism perspective, the hydrophobic layer within the pores formed by organic crystalline material has the most contribution, in which the needle-like substances generated by inorganic one filled the pores with limited effect to barrier water.

МЕТОДОЛОГИЯ УПРАВЛЕНИЯ АГРОБИОЛОГИЧЕСКОЙ, АДАПТИВНОЙ И ПРОДУКЦИОННОЙ УСТОЙЧИВОСТЬЮ НАСАЖДЕНИЙ ВИНОГРАДА В НЕСТАБИЛЬНЫХ ПОГОДНЫХ УСЛОВИЯХ И ТЕХНОГЕННОЙ ИНТЕНСИФИКАЦИИ ПРОИЗВОДСТВА

The article presents the results of agrobiological and physiological-biochemical studies to ensure the stability of grape plantations in unstable weather conditions and anthropogenic intensification of production. Studies in the agroecological conditions of the Krasnodar region on the southern chernozems revealed the most productive norm of loading of grape bushes with shoots for the technical varieties Kurchanskiy, Dmitriy, Vladimir, Granatovyi, Antaris and Alkor, on leached chernozems – for the table seedless variety Centennial Seedless. According to the results of electrophoretic separation of peroxidases in polyacrylamide gel and an increased content of ascorbic acid, increased frost resistance was established in the varieties Kristall, Vostorg, Krasnostop AZOS. The Vostorg and Zarif varieties proved to be more adaptive to the stresses of the summer period in terms of leaf hydration, bound water content, the ratio of chlorophylls and carotenoids, the amount of proline and water-soluble sugars, membrane permeability. The role of physiologically active substances in increasing the adaptive potential of grape plants has been established. The treatment of Merlot vines with methyl jasmonate and epibrassinolide during deep dormancy period, as well as proline, salicylic acid and epibrassinolide during induced dormancy period had a positive effect on the condition of the vine: there was a decrease in electrolyte yield. Sustainable grape cultivation is achieved with the systemic use of the «Bioconcentrate-Z» effluent by the non-root method. Against the background of nonroot treatments of Merlot and Cabernet Sauvignon varieties, a higher level of plant water supply, an increase in potassium content, green pigments, organic acids and grape yields were established. Physiologically active compounds and the preparation Turinbash have a positive effect in intensive own-root plantations of native and promising introduced grape varieties against the background of phylloxera infection in the southern part of Dagestan. The created yield forecasting method based on the NDVI of the grape plant and the actual data of multispectral images of the phenophases of flowering and growth allows to increase the accuracy of the calculated yield capacity to the actual one with a deviation from 0 to 0.8 kg per bush, the accuracy of the forecast increases by 2 times by the end of the growth phase and by the beginning of the maturation phase. Key words: GRAPES, METHODS, MANAGEMENT, SUSTAINABILITY, PRODUCTIVITY, QUALITY, FORECASTING

Adaptive restructuring of grape metabolism in winter period

In the unstable conditions of the Anapo-Taman zone of the Krasnodar Krai, the urgency of the problem of winter hardiness of grapes increases due to an increase in the average annual air temperature against the background of an increase in the frequency of low critical air temperatures in the winter. The adaptive rearrangements of grape metabolism associated with resistance to winter stresses have been studied. Objects of research: grape varieties of different ecological and geographical origin: Crystal, Dostoyny, Krasnostop AZOS, Vostorg, Aligote, Zarif. The electrophoretic separation of peroxidases in polyacrylamide gel in the studied grape varieties revealed that the quantitative and qualitative composition of isoforms changed during the winter period and depended on the variety and the influence of the stress factor. During the autumn-winter period, the varieties Crystal, Krasnostop AZOS, Vostorg revealed an increased total content of anthocyanins in (13.2-14.4 conventional units), ascorbic acid in shoots (13.7-18.4 µg/g of raw weight) in contrast to the varieties Aligote, Zarif. According to the research, it was found that the Crystal grape variety has increased frost resistance, followed in descending order by Krasnostop AZOS, Vostorg, Dostoyny. These varieties have great adaptive capabilities in unstable conditions of a changing climate and are recommended for cultivation in the Anapo-Taman zone, as well as for use in breeding as sources of frost resistance. Varieties Aligote, Zarif are singled out as less frost-resistant.

ВИНОГРАДАРСТВО ГУДЕРМЕСКОГО РАЙОНА ЧЕЧЕНСКОЙ РЕСПУБЛИКИ В ПЕРИОД РАСЦВЕТА ОТРАСЛИ

The article reveals the main factors and moments that characterize the develop-ment of viticulture in the Gudermessky district of the Checheno-Ingush ASSR in the 80s of the XX century. It is emphasized that this area is more suitable for viticulture than the "old" areas – Naursky, Shelkovskoy and Nadterechny. In confirmation, emphasis is placed on more favorable edaphoclimatic conditions, the possibility of introducing a non-covering and semi-covering grape culture, a higher adaptability of the population to the industry, due to the proximity to the Khasavyurtovsky District, where the population was engaged in viticulture much earlier. It was found that by the mid-1980s 8 specialized farms (wine collective farms) operated in the district, which are part of the production and collective farm association "Checheningushvino". The area of vineyards was systematically growing, the wine collective farms achieved high results in terms of gross production of grapes and grape yield capacity. A special place was given to securing vineyards for mobile groups of wine-growers (family contract) and tenants. The culture of grapes in the region occupied a prestigious place among other branches of the agro-industrial complex. It was especially noted that the processes of intensification of production were launched. High-value grape varieties with increased frost resistance were tested, allowing them to switch to a non-covering crop; the bushes were transferred to more advanced pruning, which were distinguished by a greater capacity in terms of load with shoots, etc. After the release of the Anti-Alcohol Decree and subsequent negative processes that led to the collapse of the country (and to military operations in Chechnya), the industry began to curtail. However, the experience accumulated by generations of growing grapes finds its application.

Increase in physical and mechanical properties of decorative concretes for the post‐war restoration of residential and public buildings in the Kharkiv region with the addition of highly dispersed calcite (chalk)

AbstractDuring the war active, a huge number of residential and public buildings were destroyed not only in Kharkiv and the region, but throughout Ukraine. For the restoration of destroyed buildings, new types of cement will be needed to look for and will be created decorated concretes based on them that would provide high operational and technological properties of constrictions and will be focused on local materials. Carbonate additive such as highly dispersed calcite (chalk) can be used for as local additive for concrete due to significant reserves are located in Kharkiv region. In the article research on the impact of joint action additive of highly dispersed calcite (chalk) and natural pigment (ocher) is presented by physical and mechanical properties such as density, strength, water resistance, and frost resistance. It has been established that, depending on the percentage of highly dispersed calcite (chalk), the physical and mechanical properties are changed irregularly. On the basis of the conducted researches it was established that the optimal amount of the addition of high‐fossil chalk, which provides increased frost resistance and corrosion resistance of concrete in an aggressive environment, containing chlorides, sulfates and magnesium ions, is from 10 % to 30 %. In addition, it increases density, compressive strength, stretching strength at bending. At the same time, it should be noted at an increased amount of fine chalk to 40% leads to a decrease in physical and mechanical characteristics. But the introduction of plasticizer in the amount of 0.5% leads to increased compressive strength and, accordingly, increases the positive qualities of chalk. The concrete compositions that getting with high decorative and operational properties are allowed to use them for the restoration of the city and increase in urban space.

Ceramic Bricks of Increased Frost Resistance of Kushchevsky Deposit Clay Raw Material as the Building Material within Architectural Shaping Dynamics

Introduction. The architectural and construction discourse, which has become widespread today, states that even though there develops the informational networking type of interaction among the participants of the socio-cultural exchange, the architecture will still get its rightful place because it is the most important component of the living environment of a community.Despite the rapid and successful development of applied areas of the Architectural Science caused by the dynamics of mass construction (or construction of single buildings and structures, but those, which are originally clearly meant to meet the mass requirements of the society, its stereotyped ideas about the look of a modern urban metropolis) and changes in construction technologies, design and engineering methods, forms and production resources, there is no clear understanding of what does the architecture implicate, not merely in the frame of scientific achievements, but also in the frame of the technical, technological and material progress of civilization.The problem set by the latest dynamics in the architectural and construction field (industry) is increasing the durability of wall building materials, mainly the ceramic bricks. The method of increasing the frost resistance of ceramic bricks made of Kushchevsky deposit clay raw material by adding a structuring additive into the clay mass, which ensures the required properties of the material’s pore structure, is presented in this scientific article.Materials and Methods. The present scientific work builds up on the results of the research on the effect of the proposed additive on the frost resistance of a ceramic crock made of Kushchevsky clay raw material by plastic molding. The results of the chemical analyses of the clay raw material of Kushchevsky deposit and the modifying additive are shown. As an additive there is used the waste (a calcium-bearing by-product) which is released during manufacture of the phosphate mineral fertilisers and has the form of spherical granules of 30–100 microns in diameter.In addition to determining the physical and mechanical characteristics of the burnt samples modified with a mineral additive, the porous characteristics of a ceramic crock were studied using the mercury porosimeter. With the help of the device, which is made on the basis of a quartz dilatometer and a freezer, the dilatometric measurements were carried out by freezing the water-saturated samples at the temperature of up to –20°C.Results. The carried-out experiments showed the increase in the frost resistance of the plastic-molded ceramic crock made of the clay rock of the Kushchevsky deposit when adding the carbonate-bearing mineral additive due to formation of the optimal porous structure. During numerous successive periods of freezing and thawing there was recorded good resistance of the modified samples to tensile stresses arising in the crock. The implementation of this method (of adding the proposed additive into the clay mass) in the brick factories is guaranteed to provide the manufacture of the ceramic building products with increased frost resistance.Discussion and Conclusions. Deformation curves of pores calibrating graduation in samples with and without a mineral additive are presented, along with the study results of the samples’ deformation during freezing.In conclusion, a matrix with the results of the climatic annual parameters of the Russian Federation is presented, confirming the need for the building materials to comply with the improved performance characteristics. The implementation of this method in ceramic brick manufacturing lines will foster the production of products with increased frost resistance.

Strengthening and restoration of damaged reinforced concrete structures with composite plastics

This paper considers directions to devise methods for restoring the operational suitability of reinforced concrete structures. Mistakes of designers and non-compliance with the concreting technology of monolithic reinforced concrete structures lead to the formation of cracks and deflections of unacceptable size in reinforced concrete beams and floor slabs, as well as to insufficient strength of the elements. Such structures require not only an increase in bearing capacity but also the restoration of the operational suitability of damaged structures. A technique for restoring the serviceability of bendable reinforced concrete structures with increased deflections and excessive crack opening is proposed. To restore bendable reinforced concrete structures, surface reinforcement with pre-stressed fiber-reinforced plastics is suggested, which is ensured by the creation of a building lift in the damaged elements. Fiber-reinforced plastics have a high strain modulus, elastic nature of the diagram, and increased frost resistance; they tolerate fatigue effects well and are resistant to the effects of chemically active substances. Unlike conventional reinforcement methods, surface reinforcement techniques are characterized by high gain efficiency, corrosion resistance, low labor intensity, and short terms of work; they ensure strength increase and provide for economic feasibility. This study's results established that the use of fiber-reinforced plastics not only increases the bearing capacity of reinforced concrete structures but also helps reduce the width of the cracks formed. Thus, it is possible to avoid an increase in the cross-section of structures and reduce the time of operations, which could lead to additional costs

The Effect of Low-Modulus Plastic Fiber on the Physical and Technical Characteristics of Modified Heavy Concretes Based on Polycarboxylates and Microsilica.

Manufacturers of building materials strive to optimize the three basic concrete properties—strength, durability, and shrinkage deformation, of which the focus is generally on the durability in the structure when designing and monitoring the poured concrete. Studying concretes’ structural performance and the change in their characteristics over time enables the solution of many important issues associated with the design of reliable, durable, and cost-effective buildings and structures. This article presents studies aimed at improving the physical, technical, and operational characteristics of cement concrete and reducing cement consumption in heavy concretes through the use of complex modifiers and volumetric fiber reinforcement. Four concrete compositions of widely recognized grades were developed, of which samples were molded and tested for compressive and flexural strength, frost resistance, volumetric water absorption, and density. Test results confirmed the possibility of binder (cement) economy up to 18% and increasing frost resistance up to W300 when using microsilica, reduction in volumetric water absorption of up to 40% when using both microsilica and hyperplasticizer, and increasing flexural strength by over 30% when using polymer fiber. The developed compositions passed the industrial tests, and were successfully introduced in the production process of the operating reinforced concrete products’ manufacturer.

Desiccation does not increase frost resistance of pedunculate oak (Quercus robur L.) seeds

Key messageDecreasing acorns moisture content does not significantly increase the frost resistance of pedunculate oak seeds. Slight reduction in acorn moisture content below the relatively high, optimal level decreased seed survival at temperatures below − 5 °C. The limiting temperature for pedunculate oak’s acorns below which they lose their ability to germinate is about − 10 °C.ContextSeed moisture content plays an important role in successful seed storage of many species, as desiccation increases frost resistance; however, oak seeds tolerate desiccation only to a very small extent.AimsIn our study, we examined the impact of decreasing moisture content in acorns of pedunculate oak (Quercus robur L.) on their frost resistance (below − 3 °C) and the growth of seedling derived from frozen seeds.MethodsGermination and seedling emergence of individual seeds, as well as the dry mass of their 3-month-old seedlings, were measured after acorn desiccation (24–40%, fresh weight basis) and desiccation followed by freezing at temperatures from − 3 °C to − 18 °C for 2 weeks.ResultsDecreasing acorns moisture content did not significantly increase the frost resistance of pedunculate oak seeds. The lowest temperature at which at least half seeds remain viable was − 10 °C. Slight acorns desiccation had only a small positive effect on seeds frozen below − 11 °C (down to − 13 °C), but in this case (acorn moisture content of 33%), low germinability after freezing made storage uneconomic because of the high mortality of seeds. Germinated seeds after desiccation and freezing showed no significant difference in later growth.ConclusionFresh pedunculate oak seed can survive freezing temperature down to − 10 °C and produce good quality seedlings. Temperatures around − 11° to − 13 °C are near lethal to acorns and significantly reduce their viability. Overall, desiccation does not increase their frost resistance; therefore, in practice, it is important to keep acorns during a cold storage in the highly hydrated state.

Structure, Impermeability and Durability of Cement Concrete

The paper presents the main hypotheses of frost destruction of cement concrete. The influence of cyclic temperature changes and the effect of static and dynamic (shock) loads on concrete on changes in the structure and strength of concreteis considered. The paper provides results of comparative tests of frost resistance of concrete containing a porous additive and a plasticizer, which contribute to an increase in the density and impermeability of its structure. It has been shown experimentally that the introduction of air-entraining additives with an additional effect of hydrophobization is productive from the standpoint of ensuring frost resistance of concrete of relatively low classes (up to C30/37), compressive strength up to 50 MPa and water absorption by mass more than 4.0 %. It is advisable to increase the frost resistance of concrete with greater impermeability and strength by increasing these indicators, in particular, due to the maximum decrease in the initial water content and high-quality compaction. This conclusion is experimentally confirmed by the data presented in the paper, since the “mechanism” of frost destruction of cement concrete is multifactorial, and the growth of its density (impermeability) and strength provide a higher ability to resist “force” effects associated with repeated alternating deformations of concrete, as well as the action of external loads, accumulation of fatigue phenomena, hydrodynamics of liquid filtration under the influence of changing temperature fields, etc. A comparative assessment of concrete frost resistance has been carried out using standardized and patented techniques containing a porous (air-entraining) additive, as well as plasticizing and mineral additives of amorphous micro-silica, introduced into concrete in order to increase its density, impermeability and strength and on this basis – increasing frost resistance. Experimental data are presented, reflecting the relationship and patterns of decrease in frost resistance of concrete subjected to the simultaneous action of static (for compression – different levels from the corresponding indicator of concrete strength) and shock, concentratedly applied dynamic loads. The regularity of the relationship between the accelerated frost destruction of concrete and the action of mechanical loads that cause cracking in its structure has been confirmed.

The new winter bread wheat variety of universal type ‘Donskaya Step’

Introduction and methodology. Wheat bread belongs to the greatest inventions of the mankind. Therefore, the study aimed at solving the issues of improving its productivity and quality, stabilizing the gross yield of wheat grain have always arisen a great interest of researchers and specialists in agricultural production. The most accessible source of improving yields and gross harvests is a variety.The purpose of the current study was to characterize the winter bread wheat variety ‘Donskaya Step’ according to the main economically valuable traits and properties. The study was carried out by the FSBSI “ARC “Donskoy”” from 2016 to 2020 on the experimental plots of crop rotation belonging to the winter wheat department. The object of the study was the winter bread wheat variety ‘Donskaya Step’. The variety ‘Ermak’ was used as a standard variety. There were used four forecrops: maize for grain, peas, sunflower and green fallow. The trials were conducted in sixfold replications. The accounting area of the plot was 10 m2.Results. The variety was sent to the State Variety Testing in 2016. In 2020 it was introduced into the State List for the North Caucasus and Low Volga regions of the Russian Federation. This variety has a high potential for grain productivity. The maximum yield of 11.83 t/ha was obtained in 2017 when sown in weedfree fallow. The average yield through four years of the competitive variety testing (2016–2020) was 9.77 t/ha, which is on 0.96 t/ha higher than that of the standard variety ‘Ermak’. The variety ‘Donskaya Step’ is a middle-maturing variety that forms ears and ripens as the standard variety ‘Ermak’. The variety forms high and stable yields due to increased frost resistance, drought resistance and resistance to the main wheat leaf diseases.

SPECIAL PURPOSE PLASTICATORS FOR POLYVINYL CHLORIDE

Background Elastic materials based on polyvinyl chloride (PVC) are widely used in various fields: medical products, cables, shoes, hoses, floor coverings, seals, packaging films, etc. Polyvinyl chloride is a polar rigid polymer, and for plasticizers are used to give it softness and rubbery properties. The most widespread in the production of elastic PVC materials are dialkyl phthalate plasticizers for general purposes - dioctyl phthalate and diisononyl phthalate. Aims and Objectives The paper considers the efficiency of the use of an environmentally friendly oil-free plasticizer triethylene glycol bis (2-ethylhexanoate) in a PVC compound intended for the manufacture of frost-resistant hoses. Results The effect of triethylene glycol bis (2-ethylxanoate) in comparison with dioctyl adipate (DOA) and a polymer plasticizer, which is an ester of adipic acid Edenol 1215, on the physical and mechanical properties of PVC compounds, oil and petrol resistance, frost resistance and other performance characteristics, as well as a dynamo-mechanical analysis of the investigated materials was carried out on a NETZSCH DMA 242 device. The plasticizer triethylene glycol bis (2-ethylhexanoate) contributes to the greatest decrease in the glass transition temperature of PVC compound and provides higher elasticity at low temperatures and, as a consequence, better frost resistance in comparison with dioctyl adipate and Edenol 1215 The oil and petrol resistance of PVC compounds obtained with triethylene glycol bis (2-ethylxanoate) is comparable to the sample plasticized with DOA and is noticeably inferior to the material with the plasticizer Edenol 1215, which has a higher molecular weight. Triethylene glycol bis (2-ethylhexanoate) is a promising plasticizer for the industrial production of PVC compounds with increased frost resistance.

Estimation of the possibility of using anaerobic impregnating compositions to increase frost resistance of rubber suspension elements of road vehicles

The conditions of operation of non-metallic elements of air suspension of road vehicles are analyzed. The influence of negative temperatures on non-metallic (rubber) elements of an air spring has been studied. An assessment of the possibility of using impregnating compositions for servicing the rubber elements of the air suspension of road vehicles in various temperature conditions has been carried out. It is shown that the use of impregnating compositions when servicing rubber elements of an air suspension allows minimizing cracking of the material and, consequently, increasing the durability of the suspension.

Influence of forming pressure on frost resistance of ceramics

The object of research is low-melting clays of the Kyiv region (Ukraine). The work is devoted to the study of obtaining ceramic materials resistant to low temperatures. Frost resistance is one of the most important characteristics for regions in which ceramic materials are used with frequent temperature transitions through 0 °C. The production of frost-resistant ceramic wall materials is determined by the type of raw materials and technological production parameters. The main technological methods for increasing frost resistance are: the use of less dispersed clays; batch homogenization; formation of raw material without textural defects and prevention of cracks during drying and firing. The work shows that the existing methods for increasing frost resistance can be implemented by reducing water absorption due to the creation of a microporous structure with predominantly closed pores by increased pressure of a semi-dry method of formation. An increase in the pressing pressure leads to an increase in the number of contacts of the molecules of the ceramic mass at the stage of formation. Due to this, the strength of the molded samples at a pressing pressure of more than 30 MPa is higher compared to samples molded by the plastic method. It was also found that an increase in the pressing pressure makes it possible to speed up the drying process of ceramic products, reducing energy consumption for their production. Due to an increase in the pressing pressure to 50 MPa, the strength of samples obtained by semi-dry pressing is 55.4 MPa, while for samples during plastic formation it is 22.9 MPa. Water absorption, on the contrary, for dry pressing is 9.3 %, while for plastic pressing it is 12.2 % at a firing temperature of 1000 °C. It is shown that increasing the pressing pressure is an effective way to improve the quality of ceramic materials based on local low-plasticity clay raw materials. Saving natural and energy resources, developing new sources of raw materials and comprehensive improvement of products with environmental friendliness of production remain important today.

Капиллярный подсос стенового керамического материала в зависимости от поровой структуры кирпича

The article presents the results of the study by the method of mercury porosimetry of pore structure of ceramic samples formed in the factory, obtained by plastic molding and semi-dry pressing, as well as samples of bricks selected from structures built in the XIX century. It is shown that materials with a larger volume of open large pores have increased frost resistance. There has been established dependence of the capillary suction of ceramic materials on the size of the pores, taking into account the penetration of salt solutions (nitrates, sulfates, chlorides and carbonates) into the brickwork. There has been studied the efficiency and expediency of the introduction of microsilica (terra silicea) into the clay mass from the point of view of the possible effect on the pore structure and strength of the ceramic material. The results of the research will certainly contribute to the development of effective methods related to the preventing the formation of salt deposits (salt efflorescence) violating the aesthetics of the brick building facades, and will allow developing the methods for the restoration of brick structures destroyed as a result of erosion, salt corrosion and biodegradation.

Improving the strength and resistance of cement composites to the external environment by utilizing complex additives

The article discusses the influence of complex additives on the strength and resistance of cement composites to environmental impacts. One of the additives - PFM-NLK (concrete modifier)- a factory fabricated mixture of a superplasticizer with the addition of air-retaining and water proofing substances. Another one is a complex additive containing a superplasticizer, sodium tetraborate and boric acid.Common denominator is the content of the superplasticizer. It allows reducing the W / C ratio of the mixture thereby increasing the density and strength of the composite, and, accordingly, its frost and corrosion resistance. PFM-NLK water-proofing and air-retaining substances additionally work toward the formation of a material structure with increased frost resistance. The components of the other additive, boric acid and sodium tetraborate, form a borate buffer system, which leads to the softening of the “chemical impact” and thus further increases the corrosion resistance. The research findings revealed the effectiveness of complex additives and substantiated the regularity that if each factor is separatelyfacilitative forproperty improvement, then, when they are combined, the effect is multiplied. The PFM-NLKcomponents, when combined, contribute to obtaining a material structure with high frost resistance. An additive containing a hyper-plasticizer, boric acid and sodium tetraborate leads to an increase in strength and acid resistance.

The breeding work on the winter bread wheat varieties of intensive type in the FSBSI “Agricultural Research Center “Donskoy”

The systematic study on winter wheat breeding began in 1955 in the former Zernograd experimental station, and now the Federal State Budgetary Scientific Institution “ARC “Donskoy”. Under these conditions, the development of the most suitable for local conditions varieties of intensive type with increased frost resistance determined the main direction of winter wheat breeding in those years. In the early 1980s, the area of black fallow increased in the Rostov region, much attention was paid to irrigated agriculture. There was planned to increase the area under irrigation in the North Caucasus to 1 million hectares. Therefore, there was set a goal to develop highly productive, low-stemmed, resistant to lodging varieties, responsive to mineral fertilizing with complex immunity to diseases. The breeding work of the laboratory for the breeding and seed production of winter bread wheat of an intensive type over the past forty years resulted in the development of 22 varieties of intensive type with good adaptability to the conditions of the Rostov region. In 2020, 17 winter bread wheat varieties of an intensive type were included into the State List of Breeding Achievements, five varieties ‘Yubiley Dona’, ‘Zodiak’, ‘Univer’, ‘Razdolye’, ‘Rubin Dona’ are currently undergoing the State Variety Testing at the SVTs of the Russian Federation. A stable productivity improvement is possible only with the emphasis on the development of varieties with broad adaptive properties, providing sufficiently high yields under various cultivation conditions. Among the breeding traits that affect productivity stability, the most significant in the conditions of the Don are winter and frost resistance, disease resistance, drought resistance, early ripeness, and grain quality. Therefore, the adaptive potential increase is the most important task for the future breeding. In order to solve this problem, intraspecific and interspecific hybridization, followed by targeted selection, remains the main breeding method of winter bread wheat of an intensive type.

Change in the Surface of Elastomers Based on Epichlorhydrin Rubber Modified by Functionalized Carbon Nanotubes

In this paper, we study the possibilities of the modification of epichlorohydrin rubbers by special-type functionalized carbon nanotubes activated by oxygen. The purpose of this modification is to improve the tribological properties and increase frost resistance. Two types of samples with the addition of 1 and 10% nanotubes are compared with the initial unmodified rubber. The operating conditions are simulated using tribological tests performed in the express mode. Electron microscopic surface studies of the initial elastomer and samples after tribological tests reveal a change. The introduction of nanotubes is shown to promote the formation of agglomerates of a characteristic shape, increasing the surface uniformity, and its greater stability during friction. Differences in the surface topography are already evident in samples with 1% nanotubes and noticeably increase in samples with 10% nanotubes. Using scanning probe microscopy, sample sections (topography and elastic properties) are studied after tribological tests. The surface at the cut edge is found to be denser and smoother than in the bulk layers of the sample as the elastic moduli of these regions are almost identical. The introduction of activated functionalized carbon nanotubes into epichlorohydrin rubber is shown to lead to hardening of the elastomer and increases its wear resistance.

Дослідження властивостей опору сталефібробетону

На основі теоретичних досліджень прийнятої моделі проаналізовано основні теоретичні дослідження опору сталефібробетону – зв’язок між напруженнями і деформаціями. Визначена ефективність фібрової арматури залежно від довжини і розташування фібр в просторі. Доведено, що в’язкість сталефібробетону приблизно в 10...12 разів більша за в’язкість бетону та залізобетону.

Effect on concrete of plasticizing agents based on brown coal and peat wastes

Purpose. To investigate the use of highly effective plasticizing agents that reduce the water requirements of concrete mixes, change the time of their setting, reduce water release and separation, improve the structure and physical and technical properties of hardened solutions and concrete, increase their durability. As non-deficient and cheap raw materials for the industrial production of plasticizing agents, it is advisable to use brown coal wastes in the production of mountain wax-carbon alkaline reagent (CAR) and peat plasticizer – (PP). Methods. For the modification of CAR and PP wastes of soap and oil-and-fat production – soap solutions (SS) as well as neutralized waste from desulfurization shops of coke production were used. As a result, modified CAR−1 and PP−2 agents were obtained. Soap solution keeps limiting fatty acids in the form of sodium salts as an active component and, being introduced into a concrete mix, it gives concrete positive properties (accelerate hardening, increase frost resistance), but they have weak plasticizing properties. The analysis of the modification of CAR and PP which keeps their positive properties with unchanged or increased strength of concrete. Results. The possibility of using industrial waste of soap (or oil and fat) and coke chemical production as agents in concrete in the manufacture of reinforced concrete products is analyzed. Practical relevance. The use of complex plasticizers CAR and PP−2 allows to dispose industrial waste and contributes to the protection of the environment from pollution. Agents CAR−1 and PP−2 on the basis of industrial waste are efficient for the production of high-slump and cast concrete mixes without the cost of concrete strength, reducing the vibrocompaction while molding the products by 1.5...2 times compared with plain concrete mixes and improving the quality of reinforced concrete products.