Experimental Evaluation of Residual Stresses in the Concrete

2016 ◽  
Vol 835 ◽  
pp. 433-438
Author(s):  
Lukáš Zvolánek ◽  
Miroslav Kratochvíl ◽  
Jaroslav Kadlec ◽  
Ivailo Terzijski
Keyword(s):  
Elastic Modulus ◽  
Residual Stresses ◽  
Experimental Evaluation ◽  
Concrete Composition ◽  
Volume Changes ◽  
Free Shrinkage ◽  
Concrete Mixtures ◽  
Surrounding Environment ◽  
Eurocode 2 ◽  
Degree Of Restraint

Generally, volume changes commences almost immediately after the cement and water come in contact during concrete mixing. Humidity of surrounding environment affects the magnitude of shrinkage. Hence, we took it into account by means of Eurocode 2. This paper proposes the evaluation of residual stresses in concrete. To describe the development of residual stresses, magnitude of free shrinkage, degree of its restrain and corresponding value of elastic modulus has to be known. All required quantities was measured apart from degree of restraint. It was tested three types of concrete mixtures. Obtained results show that the free shrinkage value can be significantly reduced by technological way such as the change of concrete composition.

Performance Enhancement of Recycled Aggregate Concrete – An Experimental Study

2021 ◽  
Author(s):  
Sivamani Jagan ◽  
Thurvas Renganathan Neelakantan ◽  
Palaniraj Saravanakumar
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Elastic Modulus ◽  
Performance Enhancement ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Coarse Aggregates ◽  
Durability Properties ◽  
Concrete Mixtures

Extensive studies have been performed on the mechanical and durability properties of the concrete prepared with recycled coarse aggregates (RCA), however, only modest consideration has been given to the studies on the behaviour of RAC prepared by alternative mixing approach techniques. This study presents the mechanical properties of the recycled aggregate concrete (RAC) with different percentages of RCA prepared by normal mixing approach (NMA), two-stage mixing approach (TSMA) and sand enveloped mixing approach (SEMA) techniques. The manufactured concrete mixtures were tested for compression, tension, flexure and elastic modulus at 7, 28 and 90 days. The results indicate that the mechanical properties of the RAC (with 100% of RCA) prepared through TSMA and SEMA were improved by 9.36 and 12.14% at 28 days. Perhaps, prolonged curing to TSMA and SEMA mixtures improved the mechanical properties of the RAC that is nearly equal to normal aggregate concrete (NAC) prepared by NMA.

Effects of Concrete Compositions on the Elastic Modulus

2021 ◽  
Vol 322 ◽  
pp. 41-47
Author(s):  
Rudolf Hela ◽  
Lenka Bodnárová ◽  
Klára Křížová
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Negative Impact ◽  
The Other ◽  
Technological Factors ◽  
Factors Influencing ◽  
Other Hand ◽  
Eurocode 2 ◽  
Compressive Strength Of Concrete ◽  
Reducing Costs

The paper comments on the influence of various technological factors influencing the values of elastic modulus. Today, the composition of concrete combines the classic input components with the significant use of mixed cements, active admixtures and superplasticizers in order to achieve the required compressive strength of concrete and durability while reducing costs. On the other hand, the composition of these concretes has a negative impact on the elastic modulus which are significantly lower than the values derived from compressive strength in Eurocode 2. At the end of the article is a list of measures that are a prerequisite for obtaining the required concrete elastic modulus.

Numerical Investigation of the Influence of Microstructure on the Residual Stress Distribution and Distortion in DP600 Welds

2011 ◽  
Vol 681 ◽  
pp. 79-84 ◽  
Author(s):  
A.M.Akbari Pazooki ◽  
M.J.M. Hermans ◽  
I.M. Richardson
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Phase Transformations ◽  
Dual Phase Steel ◽  
Ferrite Matrix ◽  
Volume Changes ◽  
Heating And Cooling ◽  
Distortion Level ◽  
Martensitic Phase Transformations ◽  
Cct Diagrams

Dual phase steel consists of martensite embedded in a ferrite matrix. The material experiences high heating and cooling rates during welding, which alter the microstructure significantly. In this work the effects of solid state phase transformations on the prediction of residual stresses and distortion during welding of DP600 steel is investigated. Phase fractions have been calculated implicitly using continuous cooling time (CCT) diagrams. The results of the model are compared with experimental measurements for bead-on-plate welds made on DP600 sheets. It is found that the volume changes and the increase of the strength due to the martensitic transformation have both a significant effect on the residual stress and distortion level although in opposite directions. Martensitic phase transformations in DP600 steel tend to reduce tensile residual stresses in the weld metal.

scholarly journals Investigation of the Residual Stress State in an Epoxy Based Specimen

2015 ◽  
Vol 651-653 ◽  
pp. 375-380
Author(s):  
Ismet Baran ◽  
Johnny Jakobsen ◽  
Jens H. Andreasen ◽  
Remko Akkerman
Keyword(s):  
Elastic Modulus ◽  
Stress State ◽  
Residual Stresses ◽  
Process Model ◽  
Coefficient Of Thermal Expansion ◽  
Numerical Models ◽  
Mechanical Analysis ◽  
Biaxial Stress ◽  
Image Correlation ◽  
Drilling Process

Process induced residual stresses may play an important role under service loading conditions for fiber reinforced composite. They may initiate premature cracks and alter the internal stress level. Therefore, the developed numerical models have to be validated with the experimental observations. In the present work, the formation of the residual stresses/strains are captured from experimental measurements and numerical models. An epoxy/steel based sample configuration is considered which creates an in-plane biaxial stress state during curing of the resin. A hole drilling process with a diameter of 5 mm is subsequently applied to the specimen and the released strains after drilling are measured using the Digital Image Correlation (DIC) technique. The material characterization of the utilized epoxy material is obtained from the experimental tests such as differential scanning calorimetry (DSC) for the curing behavior, dynamic mechanical analysis (DMA) for the elastic modulus evolution during the process and a thermo-mechanical analysis (TMA) for the coefficient of thermal expansion (CTE) and curing shrinkage. A numerical process model is also developed by taking the constitutive material models, i.e. cure kinetics, elastic modulus, CTE, chemical shrinkage, etc. together with the drilling process using the finite element method. The measured and predicted in-plane residual strain states are compared for the epoxy/metal biaxial stress specimen.

Residual stresses determination in injection molded virgin and recycled HDPE blends: mechanical properties and morphology

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Mirigul Altan ◽  
Mehmet Emin Yurci ◽  
Nihan Nugay
Keyword(s):  
Elastic Modulus ◽  
Impact Strength ◽  
Residual Stresses ◽  
Thermal Stresses ◽  
Mold Temperature ◽  
Morphological Properties ◽  
Time Layer ◽  
Melt Temperature ◽  
Injection Molded ◽  
Recycled Hdpe

AbstractAn experimental study of residual thermal stresses has been carried out in injection molded virgin and recycled high density polyethylene (HDPE) blends. Effects of blend concentrations on residual stresses were investigated under different injection conditions such as melt temperature, mold temperature and cooling time. Layer removal technique was used for measuring residual stresses. In order to determine the relation between the residual stresses and material characteristic of HDPE blends, mechanical and morphological properties of the blends were also investigated. Elastic modulus and impact strength were important key factors for determining the blend characteristics. As a result, it was found that HDPE blends gave higher residual stresses but lower impact strength with higher elastic modulus when recycled concentration was increased. Furthermore, it was seen that shape and size of the crystallites were also effective on residual stresses. Small and spherulitic crystallite structured blends such as 30 % recycled HDPE induced reduction in residual stresses due to easier relaxation with lower elastic modulus and higher impact strength while lamellar crystallite structured blends such as 50 % recycled HDPE gave higher elastic modulus but lower impact strength with higher residual stresses.

scholarly journals БЕТОННЫЕ СМЕСИ И БЕТОН С ДОБАВКОЙ «УКД-1» – ОЦЕНКА ИЗМЕНЕНИЙ СВОЙСТВ

2019 ◽  
Author(s):  
O. Marko ◽  
V. Livinskaya ◽  
E. Korbut
Keyword(s):  
Standardized Test ◽  
Experimental Studies ◽  
Test Methods ◽  
Concrete Composition ◽  
Chemical Additive ◽  
Concrete Mixtures ◽  
Cost Of Energy ◽  
Concrete Materials ◽  
Kinetics Of

В материале статьи изложены результаты исследований влияния отечественной комплексной химической добавки ( УКД-1 ), содержащей структурированный углеродный наноматериал (УНМ) и характеризующейся совмещенным (ускоряющим твердение и пластифицирующим) эффектом, на изменения во времени формуемости бетонных смесей и на кинетику твердения бетона в беспрогревном варианте технологии монолитного бетонирования. Целью исследований являлось установление закономерностей изменения формуемости (осадки конуса) подвижных бетонных смесей с добавкой УКД-1 во времени в зависимости от изменяющихся факторов свойств цемента, температуры, условий транспортирования для разработки соответствующих рекомендаций по использованию этой новой добавки в монолитном бетоне. При выполнении экспериментальных исследований использовали стандартизированные методы испытаний. В результате установлено, что влияние добавки УКД-1 на сохранение формовочных свойств бетонных смесей подчиняется общим закономерностям, характерным для входящих в ее состав пластифицирующего и ускоряющих твердение бетона веществ, и определена допускаемая продолжительность транспортирования смесей с этой добавкой в диапазоне температуры от 05 оС до 2530 оС, что обеспечивает необходимые условия для ведения бетонных работ. С использованием стандартизированных и оригинальных методик экспериментально выявлены закономерности роста прочности тяжелого цементного бетона под влиянием отдельно взятого ускоряющего компонента добавки УКД-1 и этой добавки в зависимости от ее дозировки (в диапазоне 0,52,0 от массы цемента). Экспериментально оценены зависимости темпа роста бетона с добавкой УКД-1 от основных технологических факторов качества цемента, величины водоцементного отношения, состава бетона и консистенции бетонной смеси, температуры среды твердения и теплоизолирующих характеристик форм-опалубок. Это позволило обосновать рациональные режимы и параметры условий твердения бетона с добавкой УКД-1 для обеспечения прочности (на сжатие) в диапазоне 50100 от требуемой в проектном возрасте (28 сут.) без затрат энергии на ускорение его твердения.The results of researches of influence of domestic complex chemical additive ( UKD-1 ), containing the structured carbon nanomaterial (CNM) characterized by the combined (the accelerating curing and plasticizer) effect on the time variation of the formability of concrete mixtures and on kinetics of curing of concrete in technology of monolithic concreting technology without warming up are expounded in the article. The aim of this study was to establish patterns of change in formability (slump) of flowable concrete mixtures with the addition of UKD-1 in time depending on the varying factors: the properties of the cement, the temperature conditions of transportation, and to develop appropriate recommendations for the use of this new additive in monolith concrete. In carrying out experimental studies using standardized test methods. As a result, found that the influence of the additive UKD-1 for the preservation of the molding properties of concrete mixtures follows the general laws specific to its constituent plasticizing and accelerating the hardening of concrete materials, and defined the permissible duration of transportation with these additive mixtures in the temperature range from 0...5 C to 25...30 C, that provides the necessary conditions for year-round maintenance of concrete work. Standardized and original methods has reviled the regularities of growth of the strength of heavy cement concrete under the influence of the separately taken accelerating component of the additive UKD-1 and this additive, depending on the dosage (in the range (0,5...2,0) of the mass of cement)). The dependence of the growth rate of concrete with the additive of UKD-1 from the basic technological factors quality of cement, the values of water-cement ratio, concrete composition and consistency of the concrete mix, ambient temperature curing and heat-insulating characteristics form formwork experimentally evaluated. This proved the rational modes and parameters of the conditions of concrete hardening with the addition of UKD-1 for strength (compression) in the range of (50...100) of the required project in the aged (28 days), without cost of energy to accelerate its hardening.

Experimental Evaluation of Residual Stresses in Ceramics

1995 ◽  
Vol 6 (1) ◽  
pp. 21-30
Author(s):  
E.E. Gdoutos, ◽  
I M. Daniel, ◽  
H M. Hsiao,
Keyword(s):  
Residual Stresses ◽  
Experimental Evaluation
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