Ресайклинг материалов дорожных одежд: аналитический обзор

The paper presents an analytical review of materials recycling for pavement dressing. Recycling or repeated usage of pavement dressing materials while making reconstruction and repair of road pavements is not considered as a new conception and it has been realized in various countries of the world since 20th century. Recycling (hot, cold) is based on methods of its execution, properties of pavement dressing materials which are subjected to processing and which influence on the quality of final material, technical and operational indices, specific economic efficiency. Investigations on the processes of structure formation, thermo-physical properties in components based on granulates of transformed pavement dressings during recycling demonstrate that regeneration makes it possible to attain 100 % recovery of material properties for road pavement base. The paper describes other factors which represent a complex of challenges concerning exterior and internal problems. These problems have arisen due to actual processes of heat and mass transfer in one layer, multi-layer systems of pavement dressings. At known coefficients of heat conductivity, steam- and mass permeability, diffusion, filtration, temperature conductivity, density of material layers etc. initial and boundary conditions it is possible to carry out optimization of heat- and mass transfer problems from bottom surface of road layer to its base (sand, bulk materials, ground). In addition to it, while taking into account development of scientific prospective direction that concerns nano-technology and creation of nano-materials for higher reliability of road dressings it is necessary to consider nanomaterial science in road-construction industry as the most actual one because when we study problems pertaining to fractional composition of all road dressing components including transfer to nanomaterials, for example, application of modified water-reducing agent based on nanostructured carbon it is possible significantly to increase physical and technological properties of asphalt concrete and concrete road dressings. The paper reveals that it is necessary to continue and expand study of physical and technical and thermophysical properties of new materials on the basis of nano-technologies with application of modified, nanostructured carbon-based plasticizer for construction-road industry because especially these additives significantly increase cement activity that leads to improvement of strength, reliability and longevity for the obtained materials.Рассмотрен анализ ресайклинга материалов дорожных одежд. Переработка или многократное использование материалов одежд при реконструкции и ремонте дорожных покрытий не является новой концепцией и реализуется в разных странах мира с начала ХХ в. Ресайклинг (горячий, холодный) основан на способах его реализации, свойствах материалов дорожных одежд, подлежащих переработке, от которых зависят качество конечного материала, технико-эксплуатационные показатели, удельная экономическая эффективность. Исследования процессов структурообразования, теплофизических свойств компонентов на основе гранулятов трансформируемых дорожных покрытий в процессе ресайклинга показывают, что при регенерации добиваются полного восстановления свойств материалов для устройства оснований дорожных покрытий. В статье описываются другие факторы, которые представляют комплексы вопросов, относящиеся к «внешней» и «внутренней» задачам. Эти задачи обусловлены реальными процессами тепло- и массопереноса в одно- и многослойных системах дорожных одеждах. При известных коэффициентах теплопроводности, паро- и массопроницаемости, диффузии, фильтрации, температуропроводности, плотности материалов слоев и т.д., начальных и граничных условиях возможна оптимизация проблем теплои массопереноса от «нижней» поверхности слоя дороги к ее основанию (песок, сыпучие материалы, грунты). Кроме того, с учетом развития научно-перспективного направления, связанного с разработкой нанотехнологий и созданием наноматериалов для повышения надежности дорожных одежд, необходимо рассматривать наноматериаловедение в строительно-дорожной отрасли как наиболее актуальное, так как, изучая вопросы фракционного состава всех компонентов, составляющих дорожную одежду, включая переход к наноматериалам, например применение модифицированной пластифицирующей добавки на основе наноструктурированного углерода, можно значительно повысить физико-технологические и теплофизические свойства асфальтобетонных и бетонных цементных дорожных одежд. В статье показано, что необходимо продолжить и расширить изучение физико-технических и теплофизических свойств новых материалов на основе нанотехнологий с применением модифицируемой, пластифицирующей добавки на основе наноструктурированного углерода для строительно-дорожной отрасли, так как именно эти добавки значительно увеличивают активность цемента, что приводит к повышению прочности, надежности и долговечности полученных материалов

Особенности тепло- и массообменных процессов в дорожных одеждах

The paper presents a fragment of on-going investigations directed on creation of optimum data environment that ensures an access to world scientific journals and other publications which are necessary for qualitative implementation of works on priority directions of R&D in the field of road-construction industry in the period of 2016–2020. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific serial publiccations which are necessary for execution of investigations on heat and mass transfer in road dressings. The road dressings are considered as open heterogeneous thermodynamic systems. Their deformations occur under various climatic conditions due to heat and mass transfer processes and interaction of transport flows and road surface. Crack formation takes place in depth of the road dressings and on road surfaces as a result of temperature, mass transfer processes. As it is known material structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-concrete, concrete, reinforced concrete scrap and products of its recycling, brick rubble, various wastes of production etc.) influence on heat and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to air viscosity, velocity of geometric permeability characteristics, capillary pressures in road pavements.Работа является фрагментом продолжающихся исследований, направленных на создание оптимальной информационной среды, обеспечивающей доступ к публикациям из мировых научных журналов и других изданий, необходимых для качественного выполнения теоретических и экспериментальных исследований по приоритетным направлениям научно-технической деятельности в области дорожно-строительной отрасли в 2016–2020 гг. Использовался цитат-анализ с применением данных Journal Citation Reports отбора мировых научных серийных изданий, необходимых для выполнения исследований по тепло- и массопереносу в дорожных одеждах. Дорожные одежды – открытые гетерогенные термодинамические системы. В различных климатических условиях имеют место их деформации вследствие тепло- и массообменных процессов и взаимодействия транспортных потоков с поверхностью дороги. При наличии температурных, массообменных процессов происходит трещинообразование как по глубине дорожных одежд, так и на дорожных покрытиях. Как известно, на тепло- и массоперенос влияет структура материалов конструктивных слоев, в особенности устроенных из техногенных отходов (асфальтобетонный, бетонный, железобетонный лом и продукты их переработки, кирпичный бой, различные отходы производств и т. д.). Представлены результаты исследований тепловых потоков пограничных слоев в зависимости от вязкости воздуха, скорости, геометрических характеристик, проницаемости, капиллярных давлений в дорожных покрытиях

Теплоустойчивость и тепломассообмен дорожных покрытий

The paper presents a fragment of on-going investigations directed on creation of optimal information environment that ensures an access to the R&D publications from the known scientific journals and other scientific serials which are necessary for qualitative execution of scientific and technological activities on priority areas in highway engineering. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific publications which are necessary for execution of investigations on heat and mass transfer in road dressings. Their deformations occur under various climatic conditions due to heat and mass transfer processes, interaction of transport flows and road surface that leads to crack formation in depth and on the surface of road dressings. Structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-, reinforced concrete, concrete, brick scrap and products of their recycling, various wastes of production etc.) exerts an influence on heat and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to viscosity, air velocity, geometric characteristics, permeability, capillary pressures in materials. It has been shown that calculations based on principles of complex number usage have specific features in engineering practice: it is required to observe their accuracy in approaches, calculation reduction due to some accuracy degradation as a consequence of transition from complex numbers to their modules with exclusion of phase shift account and related with propagation of thermal waves. In this respect calculations of heat resistance without phase shifts are considered as rather important if they are in agreement with principles based on the fact that a complexity is characterized by thermal absorptivity of the material in a great number of calculations. The investigations have been supported by Henan Center for Outstanding Overseas Scientists, Grant Number GZS 2018006 (People’s Republic of China, Henan Province).Материалы статьи являются фрагментом продолжающихся исследований, направленных на создание оптимальной информационной среды, обеспечивающей доступ к научным публикациям из известных научных журналов и других изданий, необходимым для качественного выполнения научно-технической деятельности по приоритетным направлениям в области дорожно-строительной отрасли. Использовался цитат-анализ с применением данных Journal Citation Reports отбора мировых научных серийных изданий, необходимых для выполнения исследований тепло- и массопереноса в дорожных одеждах. В различных климатических условиях имеют место их деформации вследствие тепло- и массообменных процессов, взаимодействия транспортных потоков с поверхностью дороги, при которых происходит трещинообразование по глубине и на поверхностях дорожных одежд. На тепло- и массоперенос влияют структура материалов конструктивных слоев, особенно выполненных из техногенных отходов (асфальто-, железобетонный, бетонный, кирпичный лом и продукты их переработки, различные отходы производств и т. д.). Представлены результаты исследований тепловых потоков пограничных слоев в зависимости от вязкости, скорости воздуха, геометрических характеристик, проницаемости, капиллярных давлений в материалах. Показано, что расчеты, основанные на принципах использования комплексных чисел, имеют особенности в инженерной практике: требуется точность в подходах, сокращение объема вычислений, обусловленных некоторым снижением точности вследствие перехода от комплексных чисел к их модулям, с устранением учета сдвига фаз и связанных с распространением тепловых волн. При этом актуальны расчеты теплоустойчивости без сдвигов фаз, согласуемые с принципами, основанными на том, что во многих расчетах комплексность характеризуется коэффициентом теплоусвоения материала

Fatigue Resistance of Asphalt Concrete Pavements. Peculiarity and Assessments of Potentials

This article presents the results of research of processes of deformation and destruction of asphalt concrete pavements under cyclic loads. As the ground for such approach to estimation of the asphalt concrete properties served the proof that regardless of the composition and structure of asphalt concrete with an equal amount of elastic (viscoplastic) bonds possess the same relaxation ability. This situation is a significant feature of the behaviour of asphalt concrete, which opens the way for the development of certain approaches to the analysis of their properties, evaluation of reliability and durability. The promising methodology for the comparative assessment of fatigue and cyclic durability of asphalt concrete by exploring the complex set of elastic and viscoplastic bonds in their structure depending on the temperature, magnitude, and modes of action of the loads is proposed in the presented work. In the future, the establishment of patterns of behaviour of asphalt concretes with the same set of elastic bonds is allows to optimize compositions based on the principles of temperature-structural analogy that is relevant in studying fatigue and cyclic durability as well as low-temperature crack resistance and shear stability

Prevalence and associated factors of musculoskeletal disorders among Chinese healthcare professionals working in tertiary hospitals: a cross-sectional study

Abstract Background Musculoskeletal disorders (MSDs) are prevalent in working populations and could result in a number of detrimental consequences. In China, healthcare professionals (HCP) in large hospitals may be likely to suffer from MSDs considering the facts of shortages in medical staff, the large Chinese population base, the aging of the population and patients’ inclination to go to large hospitals. This study aimed to determine the prevalence and factors associated with MSDs among HCP working in tertiary hospitals. Methods A self-administered questionnaire incorporating the Nordic Musculoskeletal Questionnaire and the Dutch Musculoskeletal Questionnaire was conducted among 14,720 HCP in eight tertiary hospitals selected by random cluster sampling in Shandong, China. Multivariable logistic regression analysis was used to quantify the association of psychological, ergonomic, organizational and individual factors with MSDs. Results The 12-month period prevalence rate of experiencing an MSD in at least one body region for at least 24 h, experiencing an MSD for at least three months, and seeking health care for this condition were 91.2, 17.1 and 68.3%, respectively; these rates were highest for the lower back (72.8, 14.3, 60.3%) and knees (65.7, 8.1, 46.7%), followed by the shoulders (52.1, 6.2, 38.9%), neck (47.6, 4.8, 32.6%), wrists/hands (31.1, 3.2, 23.1%), ankles/feet (23.6, 1.9, 13.4%), upper back, hips/thighs and elbows. MSDs were associated with workload (work hours per week, break times during workday), psychological factors (psychological fatigue, mental stress), employment status and ergonomic factors. Regarding the ergonomic factors, lower back MSDs were associated with bending the trunk frequently, heavy or awkward lifting, and bending or twisting the neck; knee MSDs were associated with walking or standing for long periods of time; and shoulder MSDs were associated with maintaining shoulder abduction for long periods of time and bending or twisting the neck. Conclusions MSDs among HCP in tertiary hospitals in Mainland China were highly prevalent. The many factors listed above should be considered in the prevention of MSDs in HCP

Recycling of Materials for Pavement Dressing: Analytical Review

The paper presents an analytical review of materials recycling for pavement dressing. Recycling or repeated usage of pavement dressing materials while making reconstruction and repair of road pavements is not considered as a new conception and it has been realized in various countries of the world since 20th century. Recycling (hot, cold) is based on methods of its execution, properties of pavement dressing materials which are subjected to processing and which influence on the quality of final material, technical and operational indices, specific economic efficiency. Investigations on the processes of structure formation, thermo-physical properties in components based on granulates of transformed pavement dressings during recycling demonstrate that regeneration makes it possible to attain 100 % recovery of material properties for road pavement base. The paper describes other factors which represent a complex of challenges concerning exterior and internal problems. These problems have arisen due to actual processes of heat and mass transfer in one layer, multi-layer systems of pavement dressings. At known coefficients of heat conductivity, steam- and mass permeability, diffusion, filtration, temperature conductivity, density of material layers etc. initial and boundary conditions it is possible to carry out optimization of heat- and mass transfer problems from bottom surface of road layer to its base (sand, bulk materials, ground). In addition to it, while taking into account development of scientific prospective direction that concerns nano-technology and creation of nano-materials for higher reliability of road dressings it is necessary to consider nanomaterial science in road-construction industry as the most actual one because when we study problems pertaining to fractional composition of all road dressing components including transfer to nanomaterials, for example, application of modified water-reducing agent based on nanostructured carbon it is possible significantly to increase physical and technological properties of asphalt concrete and concrete road dressings. The paper reveals that it is necessary to continue and expand study of physical and technical and thermophysical properties of new materials on the basis of nano-technologies with application of modified, nanostructured carbon-based plasticizer for construction-road industry because especially these additives significantly increase cement activity that leads to improvement of strength, reliability and longevity for the obtained materials

Ресайклинг материалов дорожных одежд: аналитический обзор

The paper presents an analytical review of materials recycling for pavement dressing. Recycling or repeated usage of pavement dressing materials while making reconstruction and repair of road pavements is not considered as a new conception and it has been realized in various countries of the world since 20th century. Recycling (hot, cold) is based on methods of its execution, properties of pavement dressing materials which are subjected to processing and which influence on the quality of final material, technical and operational indices, specific economic efficiency. Investigations on the processes of structure formation, thermo-physical properties in components based on granulates of transformed pavement dressings during recycling demonstrate that regeneration makes it possible to attain 100 % recovery of material properties for road pavement base. The paper describes other factors which represent a complex of challenges concerning exterior and internal problems. These problems have arisen due to actual processes of heat and mass transfer in one layer, multilayer systems of pavement dressings. At known coefficients of heat conductivity, steam- and mass permeability, diffusion, filtration, temperature conductivity, density of material layers etc. initial and boundary conditions it is possible to carry out optimization of heat- and mass transfer problems from bottom surface of road layer to its base (sand, bulk materials, ground). In addition to it, while taking into account development of scientific prospective direction that concerns nanotechnology and creation of nanomaterials for higher reliability of road dressings it is necessary to consider nanomaterial science in road-construction industry as the most actual one because when we study problems pertaining to fractional composition of all road dressing components including transfer to nanomaterials, for example, application of modified water-reducing agent based on nanostructured carbon it is possible significantly to increase physical and technological properties of asphalt concrete and concrete road dressings. The paper reveals that it is necessary to continue and expand study of physical and technical and thermophysical properties of new materials on the basis of nanotechnologies with application of modified, nanostructured carbon-based plasticizer for construction-road industry because especially these additives significantly increase cement activity that leads to improvement of strength, reliability and longevity for the obtained materials

Prospects for Evaluating the Damageability of Asphalt Concrete Pavements During Cold Recycling

The article considers improvement of the methodology for accounting for the degradation of asphalt concrete working in the upper layers of the pavement. Development of recycling technologies for road structures is an ongoing process; it allows reaching a higher quality of reclaimed materials and using them for subsequent construction of structural layers, including the upper layers without the protective ones, as well as during repair and reconstruction of roads of various technical categories. At the same time, the system of pre-project assessment (diagnostics) of the state of asphalt concrete pavements cannot be considered optimal and effective because the determined indicators demonstrate that, firstly, various surface and structural defects are present, and, secondly, that the indicators mentioned above are more relevant to the road structure as a whole. The joint handling of the theoretical and experimental data allows concluding that damageability level depends on the physical, mechanical and structural properties, the main being maximal structural strength and the number of elastic bonds involved in the deformation process. A variant of modelling of asphalt concrete damageability depending on the work capacity is proposed, when the reduced amount of dissipated energy is replaced with sufficient accuracy for practice by the ratio of the actual number of load application cycles (freezing and thawing cycles) to the limit. A correlation between the level of damageability and the kinetics of changes of the interpore space of asphalt concrete under the influence of strain (temperature, climatic factors) has been established. Results allow fixing (predicting) the level of damageability by measuring the level of water permeability. The research methodology and equipment for implementation thereof was developed earlier, it can be effectively used at the stage of pre-project diagnosis

Особенности тепло- и массообменных процессов в дорожных одеждах

The paper presents a fragment of on-going investigations directed on creation of optimum data environment that ensures an access to world scientific journals and other publications which are necessary for qualitative implementation of works on priority directions of R&D in the field of road-construction industry in the period of 2016–2020. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific serial public- cations which are necessary for execution of investigations on heat and mass transfer in road dressings. The road dressings are considered as open heterogeneous thermodynamic systems. Their deformations occur under various climatic conditions due to heat- and mass transfer processes and interaction of transport flows and road surface. Crack formation takes place in depth of the road dressings and on road surfaces as a result of temperature, mass transfer processes. As it is known material structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-concrete, concrete, reinforced concrete scrap and products of its recycling, brick rubble, various wastes of production etc.) influence on heat- and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to air viscosity, velocity of geometric permeability characteristics, capillary pressures in road pavements

Особенности тепло- и массообменных процессов в дорожных одеждах

The paper presents a fragment of on-going investigations directed on creation of optimum data environment that ensures an access to world scientific journals and other publications which are necessary for qualitative implementation of works on priority directions of R&D in the field of road-construction industry in the period of 2016–2020. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific serial public- cations which are necessary for execution of investigations on heat and mass transfer in road dressings. The road dressings are considered as open heterogeneous thermodynamic systems. Their deformations occur under various climatic conditions due to heat- and mass transfer processes and interaction of transport flows and road surface. Crack formation takes place in depth of the road dressings and on road surfaces as a result of temperature, mass transfer processes. As it is known material structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-concrete, concrete, reinforced concrete scrap and products of its recycling, brick rubble, various wastes of production etc.) influence on heat- and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to air viscosity, velocity of geometric permeability characteristics, capillary pressures in road pavements