The Influence of the Initial Concrete Strength on its Deformation under Triaxial Compression (original) (raw)
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Experimental Study of Plain Concrete under Triaxial Stress
ACI Materials Journal, 1996
The mechanical behavior of plain concrete under triaxial stress states was investigated experimentally to establish the sensitivity of the mechanical properties to an array of physical and experimental variables, and to enhance the available database of such tests for the benefit of improved understanding and modeling of the constitutive behavior of the material. The test program was particularly focused on the deformation aspects of the response and the process of damage buildup, and consisted of 130 different tests. Parameters of the experimental program were the porosity of concrete, the moisture content at the time of testing, and the load path used in the tests. The most important response index was the history of damage accumulated in the microstructure, which was measured in terms of volumetric expansion and plastic deformation of the material. A simple strain-based model was formulated to represent the experimental trends. It was shown that the expansive strain of the cross section supporting the compressive strut best organized the experimental data. This result indicates that expansion due to damage is responsible for the stiffness degradation and the softening of resistance that is observed in concrete with increasing deformation levels; hence, this is one of the most important state variables characterizing the constitutive behavior of the material.
Experimental study of the mechanical behavior of plastic concrete in triaxial compression
Cement and Concrete Research, 2005
This paper is going to present the results of an extensive experimental parametric study of the mechanical responses of various types of plastic concrete in unconfined and triaxial compression tests. Plastic concrete consists of aggregates, cement, water and bentonite, mixed at a high water cement ratio, to produce a ductile material. It is used for creating an impermeable barrier (cut-off wall) for containment of contaminated sites or seepage control in highly permeable dam foundations. A plastic concrete cut-off wall acts essentially as a barrier to stop or reduce the groundwater flow. In this study the effect of specimen age, cement factor, bentonite content and confining pressure on shear strength and permeability of plastic concrete were investigated. The observed behavior is more and more ductile for increasing confining pressure. It is shown, also, that any increase in confining pressure increases the compressive strength as well as the elastic modulus and the deformability of the specimen. It is shown that an increase in cement factor increases the shear strength as well as the elastic modulus. It is obtained that increase of bentonite content, decreases the compressive strength as well as the elastic modulus. Increasing the age of the specimens causes an increase of the compressive strength as well as the elastic modulus and also the shear strength parameters are affected. Also, it is obtained that increase in confining pressure and cement factor reduces the permeability. D
Stress-strain behavior of plastic concrete using monotonic triaxial compression tests
Journal of Central South University, 2012
The mechanical behavior of plastic concrete used in the cut-off walls of earth dams has been studied. Triaxial compression tests on the specimens in various ages and mix designs under different confining pressures have been done and the stress−strain behavior of such materials and their strength parameter changes have been experimentally investigated. It has been observed that increasing the confining pressures applied on the specimens causes the material behavior to be alike the more ductile materials and the compressive strength increases considerably as well. Moreover, a parametric study has been carried out to investigate the influence of essential parameters on the shear strength parameters of these materials. According to the research, increasing the coarse to fine aggregates ratio leads to the increase of compressive strength of the specimens as well as the increase of the cohesion and internal friction angle of the materials. Furthermore, the bentonite content decrease and the cement factor increase result in an increase of the cohesion parameter of plastic concretes and decrease of the internal friction angle of such materials.
Evaluation of Strength Criteria for Very-High-Strength-Concretes under Triaxial Compression
ACI Structural Journal, 2007
In this study, the empirical relationships proposed in the current literature were verified to assess their validity for compressive strengths between 60 and 132 MPa (8700 to 19,145 psi). A relationship was suggested to predict the ultimate strength of very high-strength concrete under triaxial compression. Furthermore, strength criteria essentially developed to estimate the ultimate strength of intact rock were applied to the concrete. The results of triaxial tests were employed to verify the applicability of these strength criteria for high-strength concrete. It is interesting to note that the strength criteria developed for intact rocks can also be applied to the assessment of ultimate strength and failure curve in high-strength concretes. Knowing only the cylinder compressive strength and the ratio of tensile-to-compressive strength, the failure envelope can be successfully evaluated by means of these criteria without performing triaxial tests in high-strength concretes.
Dynamic properties of concrete materials with high rates of tri-axial compressive loads
Sustainability, 2000
This study is to find the dynamic properties of concrete materials under both high strain-rates and triaxial stress states and to formulate the dynamic constitutive model of concrete. Thus, triaxial rapid compressive loading tests for concrete specimens were executed. In tests, the compressive strength of concrete, the confining pressure and the loading rates were chosen as test parameters. Based on test results, the influence of these parameters on the mechanical properties of concrete are examined, and then the constitutive model of concrete with the strain-rate effects is proposed.
Cement and Concrete Research, 2008
The aim of this study is to characterize the behaviour of concrete under high triaxial loading at levels of confinement and axial stress of the order of the GigaPascal. This study is carried out within a more general scope of understanding concrete behaviour under impact. The studied concrete has properties as close as possible to those used in current construction projects. A triaxial press of high capacity is used to characterize the triaxial behaviour of concrete according to various loading paths. Hydrostatic, triaxial, proportional and oedometric tests are performed and show the influence of the loading path on the compaction process. The triaxial and proportional tests show the existence of strain limit states, defining a limit states threshold independent from the loading path.
Inelastic deformation of round concrete columns in triaxial compression
Mechanics of Composite Materials, 2010
The inelastic strains are used to characterize the deformation of concrete in triaxial compression. The relation between the plastic volumetric strain and the plastic strain deviator in round confined concrete columns is analyzed. This relation is described by the inclination of the incremental plastic strain vector. A relationship for the inclination as a function of the plain concrete strength, confinement properties, and hydrostatic pressure is found. 173 0191-5665/10/4602-0173 3 2 3 2 arccos J J
2007
This thesis comprises of two different kinds of work. The first part is focussed on existing experimental data. Investigations and observations of the behaviour of plain concrete under triaxial and multiaxial compression following cyclic loading and a variety of stress paths has been presented. The behaviour of concrete with different constituents was also investigated. The directions of the plastic strain vectors were identified. Two loading surface were also identified: (i) the Peak Nominal Stress surface (PNS) which was identified from the peak stresses recorded from stress control tests and (ii) the Volume Transition Stress surface (VTS) which determines the onset of the volumetric dilation. The plastic VTS is the surface which was identified from plastic strain components only. At this surface, the directions of the plastic strain vectors are purely deviatoric. A proposal for the shapes of the yield surface for concrete is given. These shapes were identified by the plastic work...
The Journal of Strain Analysis for Engineering Design, 2009
This article presents the production of strain measurements on porous concrete samples for use in triaxial compression and extension tests with a very high lateral confining pressure. When a massive concrete structure is subjected to severe loadings (e.g. rock falls, near-field detonations, and ballistic impacts), the material undergoes triaxial loading at a high confining pressure. To reproduce high levels of stress with well-controlled loading paths, static tests are carried out on concrete using a high-capacity triaxial press, called GIGA. This press allows the testing of concrete specimens (7 cm in diameter and 14 or 15.5 cm long) for levels of confining pressure ranging up to 850 MPa and axial stresses of up to 2.35 GPa. The porous characteristic of the material together with the high confining pressure require both developing a material protection device and building strain gauge-based instrumentation of unprecedented design for such confining pressures. In addition, the effect of pressure and other sources of error on strain and stress measurements are identified herein thanks to tests performed on model materials. This study shows that the effect of pressure on strain gauge measurements is negligible, whereas this same effect proves significant in the axial displacement measurement by means of a linear variable differential transformer (LVDT) sensor and must be taken into account therefore during the data processing phase. This article will present the initial results of triaxial compression tests conducted at high confining pressure on both dry and saturated concrete samples instrumented with gauges. It will also provide results of a triaxial extension test conducted at high confinement on dry concrete: a unique step in characterizing the triaxial behaviour of concrete. Moreover, it will be demonstrated that simultaneous axial strain measurements using gauges and the LVDT sensor serve to evaluate strain homogeneity of the sample tested at high confinement.