Процессы структурообразования и свойства бетонов на органогидравлических вяжущих

The article addresses the issues of structure formation of road composite materials containing hydraulic (рortland cement) and organic (bitumen) binders. It has been determined that organic and hydraulic binders, being thermodynamically incompatible, are capable of interaction and complement each other. Structure formation processes are associated with interphase transition layers interaction mechanism and the direct formation of phase contacts with cement crystallohydrates. The interphase boundary is diffuse and is established through interphase transition layers. The emergence of interfacial layers is thermodynamically advantageous, since it contributes to a decrease in Gibbs free energy and does not contradict modern concepts of solid state physics. It was established that with cement content of about 30 % of complex bitumen-cement binder volume, there will appear (nucleate) phase contacts that will prevail in the binder structure when the cement content is more than 60 %. In the case phase contacts prevail, concrete will demonstrate significant strength at high temperatures, but low temperature and fatigue crack resistance, which will lead to their durability loss. The cement content of 30–40 % of the total complex binder can be considered optimal

Процессы структурообразования и свойства бетонов на органогидравлических вяжущих

The article addresses the issues of structure formation of road composite materials containing hydraulic (рortland cement) and organic (bitumen) binders. It has been determined that organic and hydraulic binders, being thermodynamically incompatible, are capable of interaction and complement each other. Structure formation processes are associated with interphase transition layers interaction mechanism and the direct formation of phase contacts with cement crystallohydrates. The interphase boundary is diffuse and is established through interphase transition layers. The emergence of interfacial layers is thermodynamically advantageous, since it contributes to a decrease in Gibbs free energy and does not contradict modern concepts of solid state physics. It was established that with cement content of about 30 % of complex bitumen-cement binder volume, there will appear (nucleate) phase contacts that will prevail in the binder structure when the cement content is more than 60 %. In the case phase contacts prevail, concrete will demonstrate significant strength at high temperatures, but low temperature and fatigue crack resistance, which will lead to their durability loss. The cement content of 30–40 % of the total complex binder can be considered optimal.Рассмотрены вопросы структурообразования дорожных композитных материалов, содержащих в своем составе гидравлические (портландцемент) и органические (битум) вяжущие. Установлено, что, являясь термодинамически несовместимыми, органические и гидравлические вяжущие способны к взаимодействию и дополняют друг друга. Процессы структурообразования связаны с механизмом взаимодействия межфазных переходных слоев и непосредственного образования фазовых контактов кристаллогидратами цемента. Исследования процессов срастания кристаллогидратов цемента через органические пленки, микроскопический и рентгеноструктурный анализ подтвердили данные результаты. Граница раздела фаз является размытой и осуществляется через межфазные переходные слои. Процесс появления межфазных слоев выгоден с термодинамической точки зрения, поскольку способствует уменьшению свободной энергии Гиббса и не противоречит современным представлениям физики твердого тела. При содержании цемента около 30 % от объема комплексного битумно-цементного вяжущего начнут появляться (зарождаться) фазовые контакты, которые будут преобладать в структуре вяжущего при содержании цемента более 60 % по объему. В случае преобладания фазовых контактов бетоны будут обладать значительной прочностью при высоких температурах, но низкой температурной и усталостной трещиностойкостью, что приведет к потере их долговечности. Оптимальным можно считать содержание цемента в количестве 30–40 % от общего объема комплексного вяжущего

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

Validation of Adhesive and Temperature Property Characteristics of Microsurfacing by Performance-Based Mixture Design Approach

Performance-based mixture design of microsurfacing offers a promising solution to the best application of asphalt emulsions. The presented study investigated a novel approach to evaluate the spalling resistance and high and low-temperature resistance of microsurfacing. The laboratory tests, including mixture bond strength (MBS), driving wheel pavement analyzer (DWPA), multi-stress creep recovery (MSCR), load wheel rutting (LWR), and single edge notch beam (SENB) were conducted to characterize the performance-related properties; the response surface method (RSM) was used to obtain the optimal proportions of the mixture. According to the experimental results, the performance-based mixture design method improves the comprehensive performance of microsurfacing, such as adhesion at high and low temperatures. The results of RSM show that temperature is the most important factor that affects the adhesion of mixture. There is a strong correlation between adhesive and temperature performance detected by different test methods. Due to different chemical mechanisms caused by cement and emulsified asphalt, the high-temperature performance index of the microsurfacing mixture is lower than that of HMA. Furthermore, the low-temperature resistance is analyzed and suggested indicator is proposed

Frost Resistance and Pore Structure of Concrete Incorporated with Rubber Aggregates and Nano-SiO₂

This paper aims to develop frost-resistant concretes, and investigate their pore structures and freeze–thaw damage mechanism. The frost-resistant concrete mixtures are designed by using rubber particles and nano-SiO2 to partially replace sands. The chord lengths, specific surface areas, contents and spacing coefficients of the pores in the designed concretes are measured and analyzed. The results show that concrete mixture incorporated with 5% silanized rubber and 3% nanosilica shows good synergetic effect by considering both mass loss and relative dynamic modulus of elasticity (RDME). The freeze–thaw damage degree of the concrete could be reduced by adding high elastic rubber particles, due to filling and constraining pores, and resulting in better uniform pore distribution and smaller pore spacing coefficient. Furthermore, the correlations between frost resistance and pore are analyzed and proposed

Preparation and Photocatalysis of CuO/Bentonite Based on Adsorption and Photocatalytic Activity

A CuO/bentonite composite photocatalyst was prepared to fully utilize the adsorption capacity of bentonite and the photocatalytic activity of CuO. CuO and bentonite were chosen as a photocatalyst due to the excellent optical property of CuO and large specific surface area of bentonite, together with their high stability and low production cost. The sample was characterized by XRD, SEM, and BET. The effects of several factors on degradation process were investigated such as dosage of H2O2, irradiation time, pH of the solution, and dosage of catalyst. The optimum conditions for decolorization of methylene blue solution by CuO/bentonite were determined. Under optimal conditions, the decolorization efficiency of methylene blue by a 1.4% CuO/bentonite (400 °C) composite photocatalyst under visible irradiation at 240 min reached 96.98%. The degradation process follow edpseudo-second-order kinetics. The photocatalytic mechanism is discussed in detail. This composite structure provides a new solution to the cycle and aggregation of the photocatalyst in water

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

Optimizing the Composition Design of Cement-Based Expanded-Polystyrene (EPS) Exterior Wall Based on Thermal Insulation and Flame Retardance

The use of thermal insulated decorative panel materials with low thermal conductivity and high flame retardance is a key step toward energy-saving buildings. However, traditional thermal insulation materials are always highly conductive and inflammable, which restricts their application for new buildings. This study aims to prepare the non-combustible, cement-based EPS mixtures with thermal conductivity lower than 0.045 and density less than 140 kg/m3 and characterize it with mechanical, thermal, and flame retardant properties. The effect of particle size, Silica coated and content of EPS on the physical, mechanical, thermal, and combustion performance are conducted in this paper. The comprehensive indoor tests including density, water absorbing, softening coefficient, compressive strength, tensile strength, moisture susceptibility, thermal conductivity, and scanning electron microscopy (SEM) along with combustion performance are reported to evaluate the effects of several variables on the investigated cement-based nonflammable EPS (CEPS)mixtures. The results show that small and gradation EPS particles significantly improve the comprehensive performance of mixtures. In addition, Silica coated ESP significantly improve the flame retardance of mixtures while reduce the mechanical characteristics slightly. These results contribute to the selection of appropriate materials to enhance the thermal insulation, flame retardance and mechanical properties of CEPS

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