Pub Date : 2022-02-04DOI: 10.21122/2227-1031-2022-21-1-50-56
V. N. Chernoivan, N. Chernoivan, A. V. Torkhova
Combined insulated rolled roofs, all layers of which are sequentially laid on the supporting structure and covered with a waterproof carpet, make up more than 80 % of the roofs of residential and public buildings in operation and under construction. Such a significant number of structures with a combined roll roofing in the Republic of Belarus is due to the fact that in the early 70s of the last century, a program for the development of prefabricated housing was launched in the Soviet Union. As practice has shown, after three to five years of operation, the combined insulated roll roofs needed current repairs – to eliminate leaks. The repair basically boiled down to the gluing of additional layers of rolled waterproofing material in the areas of roof leaks. Field studies have allowed us to establish the reasons why, in less than 10–12 years of operation, the combined insulated rolled roofs need major repairs. The analysis of the results of field studies has shown that the main factor affecting the failure of the roof is the high humidity of the insulation material. The main reason for moistening the material of the thermal insulation layer during the operation of the roof is the destruction of the vapor barrier layer. Based on the results of the performed field studies and regulatory documents of the Republic of Belarus, the authors of the publication offer a constructive solution and technology of work for the rehabilitation of operated combined insulated rolled roofs. The mainadvantages of the proposed solution are: provision of any thermal resistance to heat transfer of the combined coating without dismantling the structural elements of the existing roof; use of PVC membranes as a water-insulating carpet, which will allow to eliminate roof leaks within 20 years of operation without additional costs.
{"title":"Proposals for Rehabilitation of Operated Combined Insulated Rolled Roofs","authors":"V. N. Chernoivan, N. Chernoivan, A. V. Torkhova","doi":"10.21122/2227-1031-2022-21-1-50-56","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-50-56","url":null,"abstract":"Combined insulated rolled roofs, all layers of which are sequentially laid on the supporting structure and covered with a waterproof carpet, make up more than 80 % of the roofs of residential and public buildings in operation and under construction. Such a significant number of structures with a combined roll roofing in the Republic of Belarus is due to the fact that in the early 70s of the last century, a program for the development of prefabricated housing was launched in the Soviet Union. As practice has shown, after three to five years of operation, the combined insulated roll roofs needed current repairs – to eliminate leaks. The repair basically boiled down to the gluing of additional layers of rolled waterproofing material in the areas of roof leaks. Field studies have allowed us to establish the reasons why, in less than 10–12 years of operation, the combined insulated rolled roofs need major repairs. The analysis of the results of field studies has shown that the main factor affecting the failure of the roof is the high humidity of the insulation material. The main reason for moistening the material of the thermal insulation layer during the operation of the roof is the destruction of the vapor barrier layer. Based on the results of the performed field studies and regulatory documents of the Republic of Belarus, the authors of the publication offer a constructive solution and technology of work for the rehabilitation of operated combined insulated rolled roofs. The mainadvantages of the proposed solution are: provision of any thermal resistance to heat transfer of the combined coating without dismantling the structural elements of the existing roof; use of PVC membranes as a water-insulating carpet, which will allow to eliminate roof leaks within 20 years of operation without additional costs.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88083589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-04DOI: 10.21122/2227-1031-2022-21-1-42-49
V. Prokhorov, S. V. Troyanchuk, M A Razakov
The paper examines two methods of choosing the initial reference point for exergy of the moist air flow. The first method is characterized by a zero exergy value at the current temperature and humidity of the outdoor air, which are variable both in daily and annual periods. Another is characterized by constant values of parameters of moist indoor air (its temperature and humidity in the room). A comparative study has shown the advantages of the second method: greater stability of values in air processing processes and their convenient presentation on exergy chart. However, it should be noted that this method provides a non-standard technical representation in which the entire energy flow is reduced to zero. The climatic information (temperature and humidity of the outside air) for numerical-analytical experiment has been used from official open sources. The city where the air conditioning system was supposedly installed is Stavropol. The research has been carried out in the summer and cold periods of the year. It is assumed that there are not installed any large heat sources in the room and the main heat sources appeared depending on the period of the year. Additionally, the air conditioning system was equipped with a recirculation line from the serviced room with a mechanical ventilator. The recirculated air entered the mixing chamber in the air conditioning unit which is reducing the consumption of heat energy in the cold season. There are the processes of air conditioning on the Ramzin's h–d-diagram for warm and cold operational modes of air conditioning unit, the air conditioning system under consideration.
{"title":"Particularities of Exergy Analysis in Air Conditioning Systems","authors":"V. Prokhorov, S. V. Troyanchuk, M A Razakov","doi":"10.21122/2227-1031-2022-21-1-42-49","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-42-49","url":null,"abstract":"The paper examines two methods of choosing the initial reference point for exergy of the moist air flow. The first method is characterized by a zero exergy value at the current temperature and humidity of the outdoor air, which are variable both in daily and annual periods. Another is characterized by constant values of parameters of moist indoor air (its temperature and humidity in the room). A comparative study has shown the advantages of the second method: greater stability of values in air processing processes and their convenient presentation on exergy chart. However, it should be noted that this method provides a non-standard technical representation in which the entire energy flow is reduced to zero. The climatic information (temperature and humidity of the outside air) for numerical-analytical experiment has been used from official open sources. The city where the air conditioning system was supposedly installed is Stavropol. The research has been carried out in the summer and cold periods of the year. It is assumed that there are not installed any large heat sources in the room and the main heat sources appeared depending on the period of the year. Additionally, the air conditioning system was equipped with a recirculation line from the serviced room with a mechanical ventilator. The recirculated air entered the mixing chamber in the air conditioning unit which is reducing the consumption of heat energy in the cold season. There are the processes of air conditioning on the Ramzin's h–d-diagram for warm and cold operational modes of air conditioning unit, the air conditioning system under consideration.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74112967","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-04DOI: 10.21122/2227-1031-2022-21-1-57-62
I. R. Smirnov
The production of concretes with a hard hardening rate is not feasible without the use of modifying additives. The development of the chemical industry has led to the emergence of a large number of additives with different properties. Some increase the frost and corrosion resistance, the strength of building materials, while others affect the setting of concrete and the water-cement ratio. Of greatest interest is the joint work of the additives in the composition of the cement stone. The paper analyzes and determines the effect of various combinations of chemical additives (sodium carbonate Na2CO3, sodium chloride NaCl and sodium nitrate NaNO3) on the structure formation and properties of cement stone as part of a complex additive using the simplex-lattice experiment planning method. In the course of the research, to obtain cement stone, Portland cement M500 D0 has been used with the addition of Na2CO3, NaCl and NaNO3 in the established proportions. As a result of tests, it has been found that the following proportions of the components in the composition of the complex additive are optimal: NaNO3 – 12–38 %; NaCl – 34–54 %; Na2CO3 – 26–42 %. With the introduction of this complex into the composition of the concrete mixture, positive dynamics have been observed in neutralizing the corrosion effect on reinforcement in concrete, as well as an accelerated set of concrete hardness. The results obtained can be used at specialized enterprises of the chemical industry, as well as in further research in the development of modifying additives.
{"title":"Complex Additives for Concrete Based on Substances of Organic and Mineral Nature","authors":"I. R. Smirnov","doi":"10.21122/2227-1031-2022-21-1-57-62","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-57-62","url":null,"abstract":"The production of concretes with a hard hardening rate is not feasible without the use of modifying additives. The development of the chemical industry has led to the emergence of a large number of additives with different properties. Some increase the frost and corrosion resistance, the strength of building materials, while others affect the setting of concrete and the water-cement ratio. Of greatest interest is the joint work of the additives in the composition of the cement stone. The paper analyzes and determines the effect of various combinations of chemical additives (sodium carbonate Na2CO3, sodium chloride NaCl and sodium nitrate NaNO3) on the structure formation and properties of cement stone as part of a complex additive using the simplex-lattice experiment planning method. In the course of the research, to obtain cement stone, Portland cement M500 D0 has been used with the addition of Na2CO3, NaCl and NaNO3 in the established proportions. As a result of tests, it has been found that the following proportions of the components in the composition of the complex additive are optimal: NaNO3 – 12–38 %; NaCl – 34–54 %; Na2CO3 – 26–42 %. With the introduction of this complex into the composition of the concrete mixture, positive dynamics have been observed in neutralizing the corrosion effect on reinforcement in concrete, as well as an accelerated set of concrete hardness. The results obtained can be used at specialized enterprises of the chemical industry, as well as in further research in the development of modifying additives.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90241848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-04DOI: 10.21122/2227-1031-2022-21-1-73-81
R. Ivut, I. Tsarenkova
The paper identifies promising directions in the economic development of the road sector, ensuring the rational use of investments and improving the processes of construction, reconstruction and repair of roads based on the logisticsapproach, as well as contributing to the organization of safe and economically profitable transportation of goods and passengers necessary for the sustainable economic development of the country and increasing its transit potential. The set of basic logistics principles is supplemented with applied ones, the application of which will allow to manage the cycle of economic activity in the road sector as a whole. Describing the features of the logistics approach in the field under study, it has been established that the hierarchy of the construction of logistics systems is due to the use of various schemes of control actions, depending on the specifics of the functioning flows of each level. The management of the macro-logistic road management system is based on the need to increase the competitiveness of road transport services by improving the maintenance of transport flows, which is dependent on the level of development of the road infrastructure and the construction of a system for changing its state. The foundation of micro-logistic systems is formed by the resource flows of road construction production, perceived in a systemic unity. The main idea of the logistics approach to the economic development of the road economy is manifested through rational planning (macro-level) and implementation (micro-level) of measures for the development and operation of roads. The requirements of users are the basis for the choice of directions for improving their condition, which links the organization of work on road facilities with the strategy for the development of the transport and logistics system of the country. Organization of transportation of goods and passengers by road is consistent with the processes of road works, which together makes them optimal for each of the areas and the formed system as a whole. The logistics approach provides the necessary connecting framework in the management of intersectoral flow processes for the provision of road transport services and road activities, as well as intra-industry – between road services as part of the logistics system.
{"title":"Formation of Logistics Approach to Economic Development of Road Sector of the Republic of Belarus","authors":"R. Ivut, I. Tsarenkova","doi":"10.21122/2227-1031-2022-21-1-73-81","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-73-81","url":null,"abstract":"The paper identifies promising directions in the economic development of the road sector, ensuring the rational use of investments and improving the processes of construction, reconstruction and repair of roads based on the logisticsapproach, as well as contributing to the organization of safe and economically profitable transportation of goods and passengers necessary for the sustainable economic development of the country and increasing its transit potential. The set of basic logistics principles is supplemented with applied ones, the application of which will allow to manage the cycle of economic activity in the road sector as a whole. Describing the features of the logistics approach in the field under study, it has been established that the hierarchy of the construction of logistics systems is due to the use of various schemes of control actions, depending on the specifics of the functioning flows of each level. The management of the macro-logistic road management system is based on the need to increase the competitiveness of road transport services by improving the maintenance of transport flows, which is dependent on the level of development of the road infrastructure and the construction of a system for changing its state. The foundation of micro-logistic systems is formed by the resource flows of road construction production, perceived in a systemic unity. The main idea of the logistics approach to the economic development of the road economy is manifested through rational planning (macro-level) and implementation (micro-level) of measures for the development and operation of roads. The requirements of users are the basis for the choice of directions for improving their condition, which links the organization of work on road facilities with the strategy for the development of the transport and logistics system of the country. Organization of transportation of goods and passengers by road is consistent with the processes of road works, which together makes them optimal for each of the areas and the formed system as a whole. The logistics approach provides the necessary connecting framework in the management of intersectoral flow processes for the provision of road transport services and road activities, as well as intra-industry – between road services as part of the logistics system.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89138335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-04DOI: 10.21122/2227-1031-2022-21-1-63-72
D. Leontiev, V. Bogomolov, V. I. Klymenko, L. Ryzhyh, S. I. Lomaka, A. V. Suhomlin, A. V. Kuripka1, A. Frolov
The paper proposes a method for determining a vehicle stopping distance based on a braking rate and a coefficient of using an adhesion force by an automated control system for regulating a braking force on the example of a multi-axle vehicle. The aim of the study is to calculate parameters of the braking efficiency of a multi-axle wheeled vehicle equipped with an automated braking force control system based on the adhesion between a tire and a supporting surface. A peculiarity of the considered method is the use of the calculated braking coefficient of the vehicle and the coefficient of use of adhesion forces during the operation of automated system for regulating the braking force. The presence of new mathematical relationships between the position of the coordinate of the vehicle’s gravity center, realized by the clutches of its wheels, and the braking coefficient of the vehicle makes it possible to simulate the change in the deceleration of a wheeled vehicle in various braking modes of its motion. The terms describing the interaction of an elastic tire with a supporting surface in the braking mode of a wheeled vehicle have been substantiated. Equations are written that permit to calculate: a position of the coordinate of gravity center of a multi-axle wheeled vehicle relative to its front and rear axles; a braking coefficient value of a multi-axle wheeled vehicle based on the coordinates of the position of its gravity center, clutches that are realized between its tires and a supporting surface; load distribution between the respective front and rear axles of the vehicle. To calculate the stopping distance of a wheeled vehicle, it is proposed to take a coefficient value of use of the adhesion force equal to 0.83, regardless of the change in weather and climatic conditions in which the vehicle is operated (a calculation error under an accepted assumption is not more than 5 %). In a graphical form, a design diagram of the coordinate position of a gravity center of a multi-axle wheeled vehicle is presented, which gives a general idea about the redistribution of masses between front and rear axles of the vehicle. Scientific publications on the change in the value of the realized adhesion between the tire and the supporting surface in the braking mode of the automobile wheel under various factors have been analyzed in the paper. The proposed concept for determining parameters of the braking efficiency of a multi-axle wheeled vehicle clarifies some provisions in the theory of vehicle motion, in particular, it allows to apply the calculated method for determining the deceleration of a vehicle in the problem of increasing vertical loads on the axles of a multi-axle wheeled vehicle in the braking mode. The given method for calculating coefficients of weight distribution between adjacent front or rear axles of a multi-axle wheeled vehicle increases an accuracy of determining the amount of deceleration of the vehicle by the calculation method.
{"title":"About Braking of Wheeled Vehicle Equipped with Automated Brake Control System","authors":"D. Leontiev, V. Bogomolov, V. I. Klymenko, L. Ryzhyh, S. I. Lomaka, A. V. Suhomlin, A. V. Kuripka1, A. Frolov","doi":"10.21122/2227-1031-2022-21-1-63-72","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-63-72","url":null,"abstract":"The paper proposes a method for determining a vehicle stopping distance based on a braking rate and a coefficient of using an adhesion force by an automated control system for regulating a braking force on the example of a multi-axle vehicle. The aim of the study is to calculate parameters of the braking efficiency of a multi-axle wheeled vehicle equipped with an automated braking force control system based on the adhesion between a tire and a supporting surface. A peculiarity of the considered method is the use of the calculated braking coefficient of the vehicle and the coefficient of use of adhesion forces during the operation of automated system for regulating the braking force. The presence of new mathematical relationships between the position of the coordinate of the vehicle’s gravity center, realized by the clutches of its wheels, and the braking coefficient of the vehicle makes it possible to simulate the change in the deceleration of a wheeled vehicle in various braking modes of its motion. The terms describing the interaction of an elastic tire with a supporting surface in the braking mode of a wheeled vehicle have been substantiated. Equations are written that permit to calculate: a position of the coordinate of gravity center of a multi-axle wheeled vehicle relative to its front and rear axles; a braking coefficient value of a multi-axle wheeled vehicle based on the coordinates of the position of its gravity center, clutches that are realized between its tires and a supporting surface; load distribution between the respective front and rear axles of the vehicle. To calculate the stopping distance of a wheeled vehicle, it is proposed to take a coefficient value of use of the adhesion force equal to 0.83, regardless of the change in weather and climatic conditions in which the vehicle is operated (a calculation error under an accepted assumption is not more than 5 %). In a graphical form, a design diagram of the coordinate position of a gravity center of a multi-axle wheeled vehicle is presented, which gives a general idea about the redistribution of masses between front and rear axles of the vehicle. Scientific publications on the change in the value of the realized adhesion between the tire and the supporting surface in the braking mode of the automobile wheel under various factors have been analyzed in the paper. The proposed concept for determining parameters of the braking efficiency of a multi-axle wheeled vehicle clarifies some provisions in the theory of vehicle motion, in particular, it allows to apply the calculated method for determining the deceleration of a vehicle in the problem of increasing vertical loads on the axles of a multi-axle wheeled vehicle in the braking mode. The given method for calculating coefficients of weight distribution between adjacent front or rear axles of a multi-axle wheeled vehicle increases an accuracy of determining the amount of deceleration of the vehicle by the calculation method.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85107502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-04DOI: 10.21122/2227-1031-2022-21-1-82-88
T. F. Mancerova, Ngo Anh Tuyet
The regional cluster of renewable energy sources (RES) is an industrial cluster and has the characteristics of the energy industry. Therefore, it needs its own mechanism and structure of formation to ensure integrated development. The paper examines the structure of the regional RES cluster for Vietnam and proposes an apparatus for managing it. Taking into account the experience of other countries, the formation of the structure of the regional RES cluster for the conditions of Vietnam has been substantiated in order to ensure the socio-economic development of the country and its energy system,built and analyzed in accordance with the actual conditions for the use of renewable energy sources in Vietnam and includes five components: profile and non-profile members of the cluster, suppliers, consumers, competitors. A diagram describing the structure of the cluster is illustrated in detail, the roles of the participants are presented. The organizational and management structures of the regional cluster, which correspond to the specific conditions of Vietnam are considered in the paper. The management structure of the Vietnam regional cluster consists of a senior steering committee, facilitator, project manager and working groups. The responsibilities of the participants in the organizational structure are formulated in such a way as to reflect their role in the work of the regional renewable energy cluster. The structure of a regional RES cluster is able to show the relationship between participants inside and outside of the cluster. The organizational structure of the regional cluster and the strategy for its development are the foundations for building a policy in the field of renewable energy sources in the country.
{"title":"Structure and Organization of Regional Renewable Energy Cluster in Vietnam","authors":"T. F. Mancerova, Ngo Anh Tuyet","doi":"10.21122/2227-1031-2022-21-1-82-88","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-82-88","url":null,"abstract":"The regional cluster of renewable energy sources (RES) is an industrial cluster and has the characteristics of the energy industry. Therefore, it needs its own mechanism and structure of formation to ensure integrated development. The paper examines the structure of the regional RES cluster for Vietnam and proposes an apparatus for managing it. Taking into account the experience of other countries, the formation of the structure of the regional RES cluster for the conditions of Vietnam has been substantiated in order to ensure the socio-economic development of the country and its energy system,built and analyzed in accordance with the actual conditions for the use of renewable energy sources in Vietnam and includes five components: profile and non-profile members of the cluster, suppliers, consumers, competitors. A diagram describing the structure of the cluster is illustrated in detail, the roles of the participants are presented. The organizational and management structures of the regional cluster, which correspond to the specific conditions of Vietnam are considered in the paper. The management structure of the Vietnam regional cluster consists of a senior steering committee, facilitator, project manager and working groups. The responsibilities of the participants in the organizational structure are formulated in such a way as to reflect their role in the work of the regional renewable energy cluster. The structure of a regional RES cluster is able to show the relationship between participants inside and outside of the cluster. The organizational structure of the regional cluster and the strategy for its development are the foundations for building a policy in the field of renewable energy sources in the country.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81328417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-03DOI: 10.21122/2227-1031-2022-21-1-19-27
E. I. Batyanovskiy, N. S. Gurinenko, A. M. Korsun
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.
{"title":"Structure, Impermeability and Durability of Cement Concrete","authors":"E. I. Batyanovskiy, N. S. Gurinenko, A. M. Korsun","doi":"10.21122/2227-1031-2022-21-1-19-27","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-19-27","url":null,"abstract":"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.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72728679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-03DOI: 10.21122/2227-1031-2022-21-1-36-41
V. Molodin, S. Leonovich
. The adhesion of concrete is a decisive factor in restoring the performance of reinforced concrete structures. During the operation of reinforced concrete in an aggressive environment, aggressive agents penetrate through the pores and capillaries to the reinforcement which begins to corrode. The resulting corrosion products have a large volume than the metal itself, and create pressure on the protective layer concrete from the inside. Ultimately, it exfoliates, the unprotected reinforcement is destroyed even more intensively, and soon the structure loses its bearing capacity. Standard restoration includes cleaning the damaged surface, additional reinforcement and concrete coating of the structure. However, after sometime, peeling of the repair concrete is often observed. This is because a layer damaged by corrosion does not provide high-quality adhesion of the “old” concrete to the “new” one. The reason is the destruction of the structure of the surface concrete layer by aggressive influences. In most cases, carbon dioxide is an aggressive agent. The study of the effect of carbon dioxide on cement stone has shown the destruction of the crystalline framework of the material and a decrease in its cohesive strength. Micrographs of cement stone damaged and undamaged by corrosion, taken with magnification 7000 times, convincingly demonstrate the results of the destructive work of carbon dioxide. This has a significant effect on grip. The use of forced heating of the repair mixture when it is placed in contact with the restored structure leads to the appearance of temperature gradients that enhance thermal diffusion. And the greater the temperature gradient, the more intense and deeper the penetration of the cement dissolution products from the repair concrete into the concrete body of the structure being restored. And this, in turn, contributes to the impregnation of the damaged cement stone with the liquid phase from the repair concrete mixture. Crystallizing, the cement dissolution products form a new crystalline structure in the damaged cement stone, which enhances its cohesive strength and binds the repair concrete to the intact concrete structure of the restored structure, ensuring the quality of adhesion.
{"title":"Bonding of Recovery Concrete with Corrosion-Destroyed Reinforced Concrete Structure","authors":"V. Molodin, S. Leonovich","doi":"10.21122/2227-1031-2022-21-1-36-41","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-36-41","url":null,"abstract":". The adhesion of concrete is a decisive factor in restoring the performance of reinforced concrete structures. During the operation of reinforced concrete in an aggressive environment, aggressive agents penetrate through the pores and capillaries to the reinforcement which begins to corrode. The resulting corrosion products have a large volume than the metal itself, and create pressure on the protective layer concrete from the inside. Ultimately, it exfoliates, the unprotected reinforcement is destroyed even more intensively, and soon the structure loses its bearing capacity. Standard restoration includes cleaning the damaged surface, additional reinforcement and concrete coating of the structure. However, after sometime, peeling of the repair concrete is often observed. This is because a layer damaged by corrosion does not provide high-quality adhesion of the “old” concrete to the “new” one. The reason is the destruction of the structure of the surface concrete layer by aggressive influences. In most cases, carbon dioxide is an aggressive agent. The study of the effect of carbon dioxide on cement stone has shown the destruction of the crystalline framework of the material and a decrease in its cohesive strength. Micrographs of cement stone damaged and undamaged by corrosion, taken with magnification 7000 times, convincingly demonstrate the results of the destructive work of carbon dioxide. This has a significant effect on grip. The use of forced heating of the repair mixture when it is placed in contact with the restored structure leads to the appearance of temperature gradients that enhance thermal diffusion. And the greater the temperature gradient, the more intense and deeper the penetration of the cement dissolution products from the repair concrete into the concrete body of the structure being restored. And this, in turn, contributes to the impregnation of the damaged cement stone with the liquid phase from the repair concrete mixture. Crystallizing, the cement dissolution products form a new crystalline structure in the damaged cement stone, which enhances its cohesive strength and binds the repair concrete to the intact concrete structure of the restored structure, ensuring the quality of adhesion.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73891742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-03DOI: 10.21122/2227-1031-2022-21-1-28-35
B. Khroustalev, Tianxin Liu, Y. Aliakseyeu, Zhongyu Li, V. D. Akeliev, V. Minchenya
Scientific and practical calculations on the thermal stability of typical automobile road surface (semi-limited objects) with fluctuations in air temperatures, transitions from positive to negative, with actual heat transfer coefficients, thermal conductivity of components, specific mass isobaric heat capacities, material densities, periods of regular fluctuations are presented. The study shows that temperature fluctuations occur in road surfaces, therefore deformations are brought about in them, generating thermal cracks. Thermal deformations include free, proportional to temperature gradients, stressed deformations due to temperature stresses, characterized by linear thermal expansion coefficients. In road materials, physical and mechanical properties change over time: strength, moduli of elastic longitudinal deformations, shear, transverse deformation coefficients. Thus, the temperature of pavement materials depends on the coordinates, time, and thermophysical characteristics of the materials. Thermal engineering calculations have shown that many road surfaces have limited thermal stability; under the influence of relatively small external influences, they are more stable (supercooled water vapor exists for a short time, turning into a liquid, saturated, supersaturated steam into a superheated liquid, this depends on the radiation characteristics of the surfaces, the presence of external disturbances, etc.). Thus, a complex non-stationary thermal regime takes place, when the temperature fields of the coatings, their gradients of temperature potentials, and masses depend on the boundary conditions of the 1st–4th kind. A citation analysis of the data of the Journal Citation Reports of world scientific serial publications has been developed to carry out research on heat and mass transfer in road surface. The analysis shows that in order to improve the reliability and durability of pavements, fundamental studies of both the physical and technical and thermal properties of all components of road construction mixtures are of great importance.
{"title":"Thermodynamic Aspects of Pavement Engineering","authors":"B. Khroustalev, Tianxin Liu, Y. Aliakseyeu, Zhongyu Li, V. D. Akeliev, V. Minchenya","doi":"10.21122/2227-1031-2022-21-1-28-35","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-28-35","url":null,"abstract":"Scientific and practical calculations on the thermal stability of typical automobile road surface (semi-limited objects) with fluctuations in air temperatures, transitions from positive to negative, with actual heat transfer coefficients, thermal conductivity of components, specific mass isobaric heat capacities, material densities, periods of regular fluctuations are presented. The study shows that temperature fluctuations occur in road surfaces, therefore deformations are brought about in them, generating thermal cracks. Thermal deformations include free, proportional to temperature gradients, stressed deformations due to temperature stresses, characterized by linear thermal expansion coefficients. In road materials, physical and mechanical properties change over time: strength, moduli of elastic longitudinal deformations, shear, transverse deformation coefficients. Thus, the temperature of pavement materials depends on the coordinates, time, and thermophysical characteristics of the materials. Thermal engineering calculations have shown that many road surfaces have limited thermal stability; under the influence of relatively small external influences, they are more stable (supercooled water vapor exists for a short time, turning into a liquid, saturated, supersaturated steam into a superheated liquid, this depends on the radiation characteristics of the surfaces, the presence of external disturbances, etc.). Thus, a complex non-stationary thermal regime takes place, when the temperature fields of the coatings, their gradients of temperature potentials, and masses depend on the boundary conditions of the 1st–4th kind. A citation analysis of the data of the Journal Citation Reports of world scientific serial publications has been developed to carry out research on heat and mass transfer in road surface. The analysis shows that in order to improve the reliability and durability of pavements, fundamental studies of both the physical and technical and thermal properties of all components of road construction mixtures are of great importance. ","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89983655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-03DOI: 10.21122/2227-1031-2022-21-1-12-18
Ю. Федотов, магистр А. Т. Леконцев, A. Vakhrushev, A. Fedotov, A. T. Lekontsev
The aim of this work is to carry out molecular dynamics simulation of the uniaxial stretching of a cooled Al/Cu composition. The LAMMPS software package has been used for calculations, which includes the classic molecular dynamics code with an emphasis on modeling materials. The Ovito program has been used for visualization, which has a large number of functions, so that the user can thoroughly investigate the results obtained. When describing the interatomic interaction in the Al/Cu nanocomposite, we used the potential of the embedded EAM atom. The choice of potential is due to the fact that it adequately describes and reproduces the properties of a wide class of materials, including metals, semiconductors and alloys. The simulation has been carried out in two stages. At the first stage, a sample consisting of two crystallites of aluminum and copper in the form of parallelepipeds, connected along one of the joint boundaries, was placed in the computational domain and cooled at constant pressure. Cooling was carried out to stabilize the nanosystem. At the second stage, corresponding to the deformation, the temperature and pressure were changed in accordance with the ongoing physical processes. The algorithm of the thermostat and the Nose – Hoover barostat has been used to control the temperature and pressure at the initial stage of cooling. The paper demonstrates the nature of the distribution of longitudinal stresses over the entire volume of the crystal in the process of stretching. When the sample reached the elastic limit, the nucleation of crystal lattice defects and their distribution over the crystal in the form of shifts and rotations of atoms in crystal planes were observed. Areas of plastic deformation origin have been determined. The maximum destruction of the material occurred along the interface. The parameters of the Al/Cu composition (deformation, temperature, mechanical stress) have been dynamically investigated using molecular dynamics simulation. Comparison of the characteristics of the sample in the deformation process has been carried. Under loading conditions, a variety of processes are implemented in the material, including generation of defects, elastic and plastic deformation, generation of damage, and mechanical mixing.
{"title":"Modeling of Deformation and Destruction Processes of Al/Cu Nanocomposites","authors":"Ю. Федотов, магистр А. Т. Леконцев, A. Vakhrushev, A. Fedotov, A. T. Lekontsev","doi":"10.21122/2227-1031-2022-21-1-12-18","DOIUrl":"https://doi.org/10.21122/2227-1031-2022-21-1-12-18","url":null,"abstract":"The aim of this work is to carry out molecular dynamics simulation of the uniaxial stretching of a cooled Al/Cu composition. The LAMMPS software package has been used for calculations, which includes the classic molecular dynamics code with an emphasis on modeling materials. The Ovito program has been used for visualization, which has a large number of functions, so that the user can thoroughly investigate the results obtained. When describing the interatomic interaction in the Al/Cu nanocomposite, we used the potential of the embedded EAM atom. The choice of potential is due to the fact that it adequately describes and reproduces the properties of a wide class of materials, including metals, semiconductors and alloys. The simulation has been carried out in two stages. At the first stage, a sample consisting of two crystallites of aluminum and copper in the form of parallelepipeds, connected along one of the joint boundaries, was placed in the computational domain and cooled at constant pressure. Cooling was carried out to stabilize the nanosystem. At the second stage, corresponding to the deformation, the temperature and pressure were changed in accordance with the ongoing physical processes. The algorithm of the thermostat and the Nose – Hoover barostat has been used to control the temperature and pressure at the initial stage of cooling. The paper demonstrates the nature of the distribution of longitudinal stresses over the entire volume of the crystal in the process of stretching. When the sample reached the elastic limit, the nucleation of crystal lattice defects and their distribution over the crystal in the form of shifts and rotations of atoms in crystal planes were observed. Areas of plastic deformation origin have been determined. The maximum destruction of the material occurred along the interface. The parameters of the Al/Cu composition (deformation, temperature, mechanical stress) have been dynamically investigated using molecular dynamics simulation. Comparison of the characteristics of the sample in the deformation process has been carried. Under loading conditions, a variety of processes are implemented in the material, including generation of defects, elastic and plastic deformation, generation of damage, and mechanical mixing.","PeriodicalId":42375,"journal":{"name":"Science & Technique","volume":null,"pages":null},"PeriodicalIF":0.2,"publicationDate":"2022-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80079453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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