INFLUENCE OF THE INTENSITY OF DEVELOPMENT OF DESTRUCTIONS STRUCTURE OF CEMENTS UNIFORMLY COMPRESSED CONCRETES WITH INCREASING LOAD ON THEIR DEFORMATION AND DISRUPTION

Problemy sovremennogo betona i zhelezobetona ◽

10.35579/2076-6033-2020-12-13 ◽

2020 ◽

Author(s):

В.В. Совгира ◽

В.Н. Совгира

Keyword(s):

Load Level ◽

Cement Stone ◽

Loading Conditions ◽

Cement Concrete ◽

Plastic Properties ◽

Elastic Plastic ◽

Fine Grained ◽

Deformation And Fracture ◽

Analytical Expressions ◽

Increasing Load

В статье приведены особенности процесса интенсивности развития деструкций, псевдопластического деформирования и разрушения однородно и неоднородно сжатого тяжелого бетона прочностью в диапазоне fc,10 = 23,6; 40,8; 71,0 МПа [2…5 и др.] и отмечаемое отличие процесса интенсивности развития деструкций, деформирования и разрушения одноосно сжатого тяжелого, мелкозернистого и керамзитового бетона прочностью fc,10 = 50,2; 54,9 и 36,9 МПа при «мягком» и «жестком» режимах нагружения одноосно сжатых бетонных призматических колонн 5 типоразмера. Выполнен анализ литературных источников с исследованиями изменения упруго-пластических характеристик vc, Еcsek тяжелого, мелкозернистого и конструкционного керамзитового бетона с учетом влияния значимых факторов и их изменение с увеличением уровня нагрузки при описании зависимости σc-εcх. Установлено, что рекомендованные строительными нормами vcи, и Ес одноосно сжатого бетона количественно и качественно не отражают характер изменения упруго-пластических свойств тяжелого, керамзитового и мелкозернистого бетона (цементно-песчаной матрицы) центрально сжатого бетона с ростом уровня нагрузки. Предложены аналитические выражения зависимости σc-εcх, описывающие опытные значения диаграмм деформирования одноосно сжатого тяжелого, мелкозернистого (цементно-песчаной матрицы) и керамзитобетона серии В призменной прочностью fc,10 =50,2; 54,9 и 36,9 МПа исследованных бетонных образцов 5 группы типоразмеров с «мягким» и «жестким» режимами нагружения. Приведены исследования, свидетельствующие о том, что механизм деформирования и процесс развития деструкций (разуплотнения) структуры цементного камня, тяжелого, мелкозернистого и керамзитобетона с ростом уровня нагрузки отражаются на нелинейном характере изменения упруго-пластических свойств: vc -коэффициента упругости; секущего модуля упругости Еcsek = Еc ∙vc, которые отображают реологические свойства цементных бетонов в рекомендуемых выражениях (1…3). Предложены аналитические выражения зависимости изменения коэффициентов упругости (vc) и коэффициентов интенсивности развития деструкций (KD) одноосно сжатых бетонов с ростом уровня нагрузки при «мягком» и «жестком» режимах нагружения исследованных серий цементных бетонов с использованием: εсx; εсlx ; νсu ; νс, отражающих процесс изменения упруго-пластических свойств тяжелого, керамзитового, мелкозернистого бетона и цементного камня на восходящих и нисходящих участках полных диаграмм деформирования цементных композитов при центральном сжатии кратковременной статической нагрузкой. Исследованиями отмечено, что интенсивность развития деструкций в структуре однородно нагруженного тяжелого бетона существенно (в 1,17 раза) ниже, чем в одноосно сжатом мелкозернистом (цементно-песчаной матрице) и керамзитовом бетоне, и в 1,52 раза менее в цементном камне. Экспериментами установлено характерное расположение уровней параметрических точек Ѳcх; fоcrс; fνcrс тяжелого бетона с ростом уровня нагрузки исследованных видов бетонов, отражающих интенсивность развития деструкций структуры цементных бетонов. The article presents the features of the process of the intensity of the development of destruction, pseudoplastic deformation and fracture of uniformly and inhomogeneously compressed heavy concrete with strength in the range fc,10 = 23,6; 40,8; 71,0 MPa [2...5 and others] and the marked difference in the intensity of the development of destruction, deformation and fracture of uniaxially compressed heavy, fine-grained and expanded clay concrete with strength fc,10 = 50,2; 54,9 and 36,9 MPa under the “soft” and “hard” loading conditions of uniaxially compressed concrete prismatic columns of the 5th standard size. An analysis of literary sources was carried out with studies of changes in the elastic-plastic characteristics of vc, Еcsek heavy, fine-grained and structural expanded clay concrete taking into account the influence of significant factors and their change with increasing load when describing the dependence σc-εcх. It was found that the recommended by the Building Standards vcи , and Ес uniaxially compressed concrete quantitatively and qualitatively do not reflect the nature of the change in the elastic-plastic properties of heavy, expanded clay and fine-grained concrete (cement-sand matrix) of centrally compressed concrete with increasing load level. Proposed analytical expressions of the dependence σc-εcх, describing experimental values of deformation diagrams of uniaxially compressed heavy, fine-grained (cement-sand matrix) and expanded clay concrete of series B with prismatic strength fc,10 = 50,2; 54,9 and 36,9 MPa of the investigated concrete samples of the 5th group of standard sizes with “soft” and “hard” loading conditions. Studies are given that indicate that the mechanism of deformation and the process of development of destructions (decompression) of the structure of cement stone, heavy, fine-grained and expanded clay concrete with increasing load level affects the nonlinear nature of the change in the elastic-plastic properties: vc - coefficient of elasticity; secant modulus of elasticity Еcsek = Еc ∙ vc , which reflect the rheological properties of cement concrete in recommended expressions (1...3). Analytical expressions are proposed for the dependence of changes in the elastic coefficients (vc) and the coefficient of developmental rate of destruction (KD) of uniaxially compressed concrete with an increase in the load level under the “soft” and “hard” loading conditions of the investigated series of cement concrete using: εсx; εсlx ; νсu ; νс , reflecting the process of changing the elastic-plastic properties of heavy, expanded clay, fine-grained concrete and cement stone in the ascending and descending sections of the complete diagrams of deformation of cement composites under central compression with a short-term static load. Studies have noted that the intensity of the development of destruction in the structure of uniformly loaded heavy concrete is significantly (1,17 times) lower than in uniaxially compressed fine-grained (cement-sand matrix) and expanded clay concrete and 1,52 times less in cement stone. The experiments established a characteristic arrangement of the levels of parametric points Ѳcх; fоcrс; fνcrс of heavy concrete with an increase in the load level of the investigated types of concrete, reflecting the intensity of the development of destruction of the structure of cement concrete.

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ПОЛНЫЕ ДИАГРАММЫ РАЗВИТИЯ ДЕСТРУКЦИЙ ОДНОРОДНО И НЕОДНОРОДНО СЖАТОГО БЕТОНА ПРИ ОСЕВОМ И ВНЕЦЕНТРЕННОМ НАГРУЖЕНИИ БЕТОННЫХ КОРОТКИХ КОЛОНН

Problemy sovremennogo betona i zhelezobetona ◽

10.35579/2076-6033-2019-11-18 ◽

2019 ◽

Author(s):

V. Sovgira ◽

V. Sovgira

Keyword(s):

Stress State ◽

Cross Section ◽

Concrete Columns ◽

Load Level ◽

Transverse Deformation ◽

Plastic Properties ◽

Elastic Plastic ◽

Loading Mode ◽

The Cross ◽

Increasing Load

В статье приведены результаты выполненных исследований механизма интенсивности развития деструкций, псевдопластического деформирования и разрушения однородно и неоднородно сжатого тяжелого бетона призменной прочностью в диапазоне fc1522,265,6 МПа при мягком и жестком режиме нагружения одноосно и внецентренно сжатых бетонных колонн. Выполнен анализ литературных источников с исследованиями изменения упруго-пластических характеристик vc, Еcsek тяжелого бетона с учетом влияния значимых факторов и их изменение с увеличением уровня нагрузки при описании зависимости c-cх и c,е - cх,е. Установлено, что рекомендованные Строительными Нормами vcи и Ес одноосно сжатого бетона количественно и качественно не отражают характер изменения упруго-пластических свойств неоднородно сжатого бетона с ростом уровня нагрузки. Предложены аналитические выражения зависимости изменения коэффициентов упругости (vc, vc,е), секущих модулей упругости (Еcsek, Еc,еsek) и коэффициентов интенсивности развития деструкций (KD, KD,е) однородно и неоднородно сжатого бетона с ростом уровня нагрузки при мягком и жестком режиме нагружения исследованных серий тяжелого бетона с использованием сlx сlx,е Ес Nc,e/Ncu,e сu и сu,е, отражающих процесс изменения упруго-пластических свойств бетона на восходящих и нисходящих участках полных диаграмм деформирования бетона и их существенное отличие при центральном и внецентренном сжатии. Исследованиями отмечено, что интенсивность развития деструкций в структуре неоднородно нагруженного бетона существенно ниже, чем в одноосно сжатом. Экспериментами установлено характерное изменение по высоте сечения внецентренно сжатых бетонных элементов коэффициента поперечных деформаций , свидетельствующее о том, что с увеличением уровня нагрузки коэффициент наиболее сжатой фибры на всех уровнях нагрузки, значительно (в 1,21,5 раза) меньше волокон менее нагруженных фибр. Отмеченное свойство обусловлено изменением внутреннего напряженного состояния с ростом нагрузки и перераспределением напряжений силовыми связями структуры неоднородно сжатого бетона с субмикро- и микроуровней волокон наиболее нагруженной грани по высоте сечения внецентренно сжатых элементов на менее нагруженные волокна. Этот процесс перераспределения напряжений по высоте сечения бетонных колонн как свойство проявляется на изменении поперечной деформации cу,е и, как следствие изменения коэффициента поперечной деформации , влияющего на напряженное состояние сжатой зоны подобно внутренним силовым связям, обеспечивающим существенное повышение максимальных напряжений и деформаций в неоднородно сжатом бетоне.The article presents the results of studies of the intensity of development of destructions, pseudoplastic deformation and destruction of uniformly and non-uniformly compressed heavy concrete with prism strength in the range of fc1522,265,6 MPa in the soft and hard loading mode of uniaxially and eccentrically compressed concrete columns. The analysis of literary sources with studies of changes in the elastic-plastic characteristics of vc, Еcsek heavy concrete, taking into account the influence of significant factors and their change with increasing load level when describing the dependence c-cх and c,е - cх,е . It has been established that the vcu and Ес recommended by the Building Norms of uniaxially compressed concrete do not quantitatively and qualitatively reflect the nature of the change in the elastic-plastic properties of non-uniformly compressed concrete with increasing load levels. Analytical expressions are proposed for the dependence of the change in elasticity coefficients (vc, vc,е), cross-section elastic modulus (Еcsek, Еc,еsek) and the intensity factors for the development of destructions (KD, KD,е) of uniformly and non-uniformly compressed concrete and hard loading mode of the studied series of heavy concrete using: сlx сlx,е Ес Nc,e/Ncu,e сu and сu,е , reflecting the process of changing the elastic-plastic properties of concrete in the ascending and descending parts of the complete concrete deformation diagrams and their significant difference under uniaxial and eccentrically compression. Studies have noted that the intensity of the development of destructions in the structure of non-uniformly loaded concrete is significantly lower than in uniaxially compressed. Experiments established a characteristic change in the height of the cross section of eccentrically compressed concrete elements of the transverse strain coefficient , indicating that with an increase in the load level, the coefficient of the most compressed fiber at all load levels is significant (1,2-1,5 times) less fibers, less loaded fibers. This property is caused by the change in the internal stress state with increasing load and stress redistribution by force bonds of the structure in non-uniformly compressed concrete from submicro- and microlevels of the fibers of the most loaded face along the height of the cross section of eccentrically compressed elements to less loaded fibers. This process of stress redistribution along the height of the cross section of concrete columns as a property manifests itself in a change in transverse deformation cу,е and, as a result, a change in the transverse deformation coefficient , affecting the stress state of the compressed zone, similar to internal force connections, providing a significant increase in maximum stresses and strains in non-uniformly compressed concrete.

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СРАВНИТЕЛЬНАЯ ОЦЕНКА РАЗЛИЧНЫХ ТЕХНОЛОГИЧЕСКИХ ПРИЕМОВ ВВЕДЕНИЯ ДОБАВОК УГЛЕРОДНЫХ НАНОМАТЕРИАЛОВ В БЕТОНЫ И БЕТОННЫЕ СМЕСИ

Problemy sovremennogo betona i zhelezobetona ◽

10.35579/2076-6033-2019-11-14 ◽

2019 ◽

Author(s):

P. Ryabchikov ◽

V. Yakimovich ◽

S. Kovshar

Keyword(s):

Uniform Distribution ◽

Carbon Nanomaterials ◽

Solid Phase ◽

Cement Stone ◽

Careful Study ◽

Cement Concrete ◽

Chemical Additives ◽

Processing Methods ◽

Fine Grained ◽

Stone Concrete

В материале статьи отражены основные результаты исследования влияния различных технологических приемов введения отечественных углеродных наноматериалов (УНМ) в тяжелые и мелкозернистые бетоны и бетонные смеси. Введение малого количества твердофазного вещества УНМ в бетон представляет собой сложную задачу с позиций его равномерного распределения по объему приготавливаемой бетонной смеси, т. к. это не растворимое в воде вещество. Кроме этого, вследствие малого собственного размера частицы УНМ при комнатной температуре и атмосферном давлении начинают самоорганизовываться , объединяясь и укрупняясь вплоть до образования микроскопических гранул . Введение в цемент (бетон, раствор) углеродных наноматериалов различными технологическими приемами обеспечивает рост прочности цементного камня (бетона, раствора) как в условиях естественного (нормально-влажностного) твердения, так и в случае ускоренного твердения при тепловой обработке образцов. На уровень прироста прочности цементного камня (бетона, раствора), в отдельных случаях достигавшего 4060 , оказывает основное влияние вид (состав) УНМ и дозировка вещества оптимальная примерно соответствует 0,05 от массы цемента. Все проверенные способы введения УНМ могут быть реализованы при производстве бетонных смесей (бетонов, растворов). При тщательной проработке технологии введения тем или иным способом возможно обеспечение равномерного распределения УНМ в объеме смеси, что подтверждается примерным равенством увеличения прочности цементного камня для различных способов введения (смешиванием с цементом, песком, химическими добавками, диспергированием в воде затворения). Но наиболее перспективным представляется прием введения УНМ в комплексе с порошкообразными твердофазными пластифицирующей и ускоряющей твердение цемента химическими добавками для бетона. Полученные результаты исследований развивают предпосылки к более широкому использованию УНМ в конструкционных цементных бетонах.Тhe main results of a research of influence of various processing methods of introduction of domestic carbon nanomaterials (СNM) to heavy and fine-grained concrete and concrete mixes are reflected in material of article. Introduction of small amount of solid-phase substance СNM to concrete represents a difficult task from positions of its uniform distribution on volume of the prepared concrete mix since this insoluble substance in water. Besides, owing to the small own size of a particle of СNM at the room temperature and atmospheric pressure begin to self-organize, uniting and being integrated up to formation of microscopic granules. Introduction to cement (concrete, mortar) of carbon nanomaterials various processing methods, provides growth of durability of a cement stone (concrete, mortar) both in the conditions of natural (normal and moist) curing, and in case of the accelerated curing at thermal treatment of samples. The type (structure) of СNM and dosage of substance has the main impact on the level of gain of durability of a cement stone (concrete, mortar) in some cases reaching 40 60 optimum approximately there correspond 0,05 of the mass of cement. All checked ways of introduction of СNM can be realized by production of concrete mixes (concrete, mortar). At careful study of technology of introduction ensuring uniform distribution of СNM in volume of mix is one way or another possible that is confirmed by approximate equality of increase in durability of a cement stone for various ways of introduction (mixing with cement, sand, chemical additives, dispersion in water). But reception of introduction of СNM in a complex with the powdery solid-phase chemical additives plasticizing and accelerating cement curing for concrete is represented to the most perspective. The received results of researches develop prerequisites to wider use of СNM in constructional cement concrete.

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Concretes, Modified by the Addition of High-Diffused Chalk, for Small Architectural Forms

Materials Science Forum ◽

10.4028/www.scientific.net/msf.968.82 ◽

2019 ◽

Vol 968 ◽

pp. 82-88 ◽

Cited By ~ 4

Author(s):

Svitlana Chepurna ◽

Olga Borziak ◽

Svitlana Zubenko

Keyword(s):

High Performance ◽

Low Cost ◽

Physical And Mechanical Properties ◽

Complex Compounds ◽

Cement Stone ◽

Cement Concrete ◽

Dense Structure ◽

Corrosive Media ◽

Plastic Properties ◽

Highly Dispersed

In modern construction, a large variety of small architectural forms are used, for the production of which cement concrete is traditionally used, which should have improved physical and mechanical properties and decorative properties, while having a low cost. Improvement of these properties is achieved through the use of carbonate additives - highly dispersed chalk. Experimental results show that the addition of highly dispersed chalk affects the structure of cement stone, which is represented by low-base hydrosilicates, calcium hydrocarbonate and complex compounds that create a dense structure, which reduces the permeability of the material for corrosive media. It is assumed that the addition of highly dispersed chalk improves the elastic-plastic properties, increases the crack resistance, which provides high performance properties of concrete.

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Study of the Relationship between Concrete and its Reinforcement Elastic-Plastic Characteristics

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1043.109 ◽

2021 ◽

Vol 1043 ◽

pp. 109-114

Author(s):

Violetta Bratoshevskaya

Keyword(s):

Pore Space ◽

Crystalline Hydrate ◽

Internal Stresses ◽

Material Structure ◽

Cement Stone ◽

Plastic Properties ◽

Elastic Plastic ◽

Adsorption Interaction ◽

A Charge ◽

The Relationship

The relationship between the elastic-plastic properties of concrete and its ability to resist the external loads and internal stresses effects arising under the influence of aggressive environmental factors has been studied. In concrete, micro-and macrocracks are filled with air and a liquid phase migrates with periodic environmental temperature, therefore, humidity changes. When the structure is compacted by crystalline hydrate neoplasms arising from supersaturated solutions, their surface increases and, correspondingly the part of water hydraulically bound to it also increases which changes its mobility with temperature. This entire system of interphase and single-phase structural bonds and interactions in concrete changes with fluctuations in humidity, cooling, and especially during phase transitions during freezing. The research found that the introduction of hydraulic additives into the binder, which carry a negative charge on their surface, leads to a charge change of the material structure pore space. The penetration kinetics of aggressive environments, adsorption interaction with the cement stone capillaries surface has been studied.

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Finite Pure Plane Strain Bending of Inhomogeneous Anisotropic Sheets

Symmetry ◽

10.3390/sym13010145 ◽

2021 ◽

Vol 13 (1) ◽

pp. 145

Author(s):

Sergei Alexandrov ◽

Elena Lyamina ◽

Yeong-Maw Hwang

Keyword(s):

Plane Strain ◽

Yield Criterion ◽

Large Strains ◽

Rigid Plastic ◽

Plastic Properties ◽

Elastic Plastic ◽

Starting Point ◽

The Difference ◽

Inside Radius ◽

Elastic Unloading

The present paper concerns the general solution for finite plane strain pure bending of incompressible, orthotropic sheets. In contrast to available solutions, the new solution is valid for inhomogeneous distributions of plastic properties. The solution is semi-analytic. A numerical treatment is only necessary for solving transcendent equations and evaluating ordinary integrals. The solution’s starting point is a transformation between Eulerian and Lagrangian coordinates that is valid for a wide class of constitutive equations. The symmetric distribution relative to the center line of the sheet is separately treated where it is advantageous. It is shown that this type of symmetry simplifies the solution. Hill’s quadratic yield criterion is adopted. Both elastic/plastic and rigid/plastic solutions are derived. Elastic unloading is also considered, and it is shown that reverse plastic yielding occurs at a relatively large inside radius. An illustrative example uses real experimental data. The distribution of plastic properties is symmetric in this example. It is shown that the difference between the elastic/plastic and rigid/plastic solutions is negligible, except at the very beginning of the process. However, the rigid/plastic solution is much simpler and, therefore, can be recommended for practical use at large strains, including calculating the residual stresses.

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Influence of innovative three-element binder on permanent deformations in recycled mixtures with emulsion and foamed bitumen

Archives of Civil and Mechanical Engineering ◽

10.1007/s43452-021-00192-9 ◽

2021 ◽

Vol 21 (2) ◽

Author(s):

Grzegorz Mazurek ◽

Marek Iwański ◽

Przemysław Buczyński ◽

Renata Horodecka

Keyword(s):

Hydrated Lime ◽

Component Composition ◽

Load Level ◽

Point Of View ◽

Cement Dust ◽

Basic Part ◽

Fine Grained ◽

Time Deformation ◽

Hydraulic Binder ◽

Foamed Bitumen

AbstractThis article is detected to the assessment of durable deformations of recycled mixtures made of foamed bitumen (MCAS) and emulsion (MCE). In the basic part of research and analyses, attention was focused on determining the scale of three-component composition modifying rheological phenomena of recycled mixtures and other selected features considering various methods of bituminous binder proportioning. Cement, hydrated lime, and dusts from cement dust extracting system were included in the composition hydraulic binder. In this paper, the effect of graining of recycled mixture was also taken into account. One of the main scientific aims of the paper was to evaluate the degree of changes in durable deformations described in the power model depending on proportions of elements making three-element hydraulic binder. In effect, it was pointed out that the influence of hydraulic binder differently affected the durable deformation of recycled mixture depending on ways of bitumen binder implementation. There-element binder exerted the highest influence on mechanical properties of mixtures with fine-grained mixtures made according to the MCAS technology. The presence of 4 groups of mixtures with different properties was demonstrated using the classification neuron net. Based on that information, a set of the most recommended solutions from the point of view of time deformation resistance, low sensitiveness to the load level at moderate stiffness was selected. The best representative among them was the arrangement with 20% of hydrated lime, less than 40% of CBPD dusts and 40 ÷ 60% of cement.

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Cumulation of a spherically converging shock wave in metals and its dependence on elastic-plastic properties, phase transitions, spall and shear fractures

Journal of Physics Conference Series ◽

10.1088/1742-6596/490/1/012191 ◽

2014 ◽

Vol 490 ◽

pp. 012191 ◽

Cited By ~ 3

Author(s):

E A Kozlov ◽

A V Petrovtsev

Keyword(s):

Shock Wave ◽

Phase Transitions ◽

Plastic Properties ◽

Elastic Plastic ◽

Converging Shock Wave

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Determining Elastic-Plastic Properties of Al6061-T6 from Micro-Indentation Technique

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.592-593.610 ◽

2013 ◽

Vol 592-593 ◽

pp. 610-613

Author(s):

Sina Amiri ◽

Nora Lecis ◽

Andrea Manes ◽

Davide Mombelli ◽

Marco Giglio

Keyword(s):

Manufacturing Process ◽

Optimization Procedure ◽

Test System ◽

Standard Test ◽

Material Behavior ◽

Plastic Properties ◽

Representative Strain ◽

Elastic Plastic ◽

Dimensionless Analysis ◽

Micro Indentation

Different approaches have been proposed in order to determine the material behavior of ductile materials. Since, the mechanical properties of a mechanical component are modified during manufacturing process due to plastic deformation, heat treatment and etc, a non-destructive indentation experimental procedure addressed to predict the elastic-plastic properties of material after manufacturing process is of interest. This is especially true for small size components where it is complex to extract specimens to test on standard test system. Based on dimensionless analysis and the concept of a representative strain, different approaches have been proposed to determine the material properties of power law materials by using indentation process. In this work, the Johnson-Cook (JC) constitutive model of the aluminum alloy Al6061-T6 is characterized by means of a well-defined optimization procedure based on micro-indentation testing and high fidelity finite element models and an optimization procedure but without the concept of dimensionless analysis and a representative strain. This methodology allows determining a set of JC constants for Al6061-T6. The obtained results have good agreement with parameters calibrated by means of universal standard tests and reverse engineering approach.

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