scholarly journals Stress-strain curve of concretes with recycled concrete aggregates: analysis of the NBR 8522 methodology

2017 ◽  
Vol 10 (3) ◽  
pp. 547-567 ◽  
Author(s):  
D. A. GUJEL ◽  
C. S. KAZMIERCZAK ◽  
J. R. MASUERO
Keyword(s):  
Test Procedure ◽  
Strain Curve ◽  
Recycled Concrete ◽  
Load Test ◽  
Recycled Aggregates ◽  
Elastic Behavior ◽  
It Use ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Brazilian Standard

ABSTRACT This work analyses the methodology "A" (item A.4) employed by the Brazilian Standard ABNT 8522 (ABNT, 2008) for determining the stress-strain behavior of cylindrical specimens of concrete, presenting considerations about possible enhancements aiming it use for concretes with recycled aggregates with automatic test equipment. The methodology specified by the Brazilian Standard presents methodological issues that brings distortions in obtaining the stress-strain curve, as the use of a very limited number of sampling points and by inducing micro cracks and fluency in the elastic behavior of the material due to the use of steady stress levels in the test. The use of a base stress of 0.5 MPa is too low for modern high load test machines designed do high strength concrete test. The work presents a discussion over these subjects, and a proposal of a modified test procedure to avoid such situations.

scholarly journals Analysis of High Strength Concrete processed from Recycled Concrete Aggregates

2021 ◽  
Vol 9 (12) ◽  
pp. 1757-1763
Author(s):  
Shanu Sharma
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Coarse Aggregate ◽  
Strain Curve ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Hardened Concrete ◽  
Stress Strain Curve ◽  
Stress Strain

Abstract: As everyone is aware of the fact that Natural Coarse Aggregate (NCA) is the main constituent of traditional concrete mixes. Whenever an existing concrete structure is demolished, it produces smashed concrete waste in the large amount. Concrete waste give rise to negative effects on the environment. To evade the environmental pollution and mark effective reuse of the concrete waste as Recycled Aggregates in the place of NCA. This operative initiative provides an opportunity to reduce air pollution and soil exploitation to some extent. Such concrete is sustainable in nature and also eco-friendly to the environment. Also, such waste material will lower the usage of naturally occurring stone to produce NCA and thus various natural energy resources will be safeguarded. This study covers the suitability norms for a material to be used for Recycled Aggregate. In this study the natural aggregate is replaced with recycled aggregate in the different percentages (0%, 25%, 50%). When percentage of recycled aggregate mixed in the fixed proportion as percentage replacement to natural aggregates, it imparts improvement in the property of fresh as well as hardened concrete like, compressive strength & split tensile strength. Laboratory results of this research indicates that the value of compressive strength, tensile strength stress-strain curve & NDT of these mixes drives on decreasing, but at the 25% replacement level, it achieves target mean strength. Hence, for the fundamental concrete mix Natural Coarse Aggregate can be efficiently replaced by the Recycled Aggregate to the range of 25%. Keywords: Concrete, Recycled aggregate, Natural Coarse Aggregate (NCA), Compressive Strength, Tensile strength, , NDT, Stress-Strain Curve

Experimental Study on Stress-Strain Curve of Recycled Coarse Aggregate Concrete under Uniaxial Compression

2013 ◽  
Vol 357-360 ◽  
pp. 1415-1419 ◽  
Author(s):  
Zhi Heng Deng ◽  
Li Chen ◽  
Jian Qian ◽  
Chao Lou Meng
Keyword(s):  
Coarse Aggregate ◽  
Strain Curve ◽  
Recycled Concrete ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Recycled Coarse Aggregate ◽  
Rational Expression ◽  
The Difference ◽  
Two Stages

In order to study the mechanical properties of recycled concrete with the same strength, three kinds of recycled concrete have been made which their intensities reached C25, C30, C35 at the recycled coarse aggregate replacement ratios (0%, 50%, 100%), and severally completed the stress-strain curve test on the same strength of recycled concrete, separately analyzed the variance about failure pattern and peak strain, elastic modulus that all belonged to recycled concrete under the condition of the same strength. Studies have shown that the overall shape of recycled concretes stress-strain curves is similar to normal concretes under the same strength, and the difference is small, modulus of elasticity decreases with the increase of recycled coarse aggregate replacement ratio, while the peak strain basicly remains unchanged. Their curves can be used two stages respectively and also be represented by three fitting polynomial and rational expression, their descent stages steepened gradually with the increase of recycled coarse aggregate replacement rate.

scholarly journals Analysis of damage-plasticity model of concrete under uniaxial compression loading

2021 ◽  
Vol 10 (1) ◽  
pp. 29
Author(s):  
Mohammad Rafiqul Islam ◽  
Abbas Ali ◽  
Md. Jahir Bin Alam ◽  
Tanvir Ahmad ◽  
Salman Sakib
Keyword(s):  
Analytical Data ◽  
Strain Curve ◽  
Material Behavior ◽  
Elastic Behavior ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Compression Loading ◽  
Model Code ◽  
Concrete Damage ◽  
Two Phases

Concrete is a quasi-brittle material and shows different behavior in compression and tension. It shows elastic behavior at initial stage and damage-plasticity behavior beyond elastic limit. Therefore, development of material behavior model of concrete is a complex phenomenon. In this study, concrete damage plasticity theory has been described under experiment on concrete cylinder considering uni-axial compression loading and interpreted with analytical data calculated using CEB-FIP model code equation. The code has divided the stress-strain curve for concrete compression into three sections according to concrete’s elastic and non-elastic behaviors. Those three sections have been considered to calculate analytical data. In experiment, concrete behavior has been observed in two phases. The damage value for different stresses at the various points on the stress strain curve has been calculated. According to analytical data, the concrete shows elastic behavior up to 8.3MPa stress point and no damage occur in the concrete within the limit. However, in experimental data, concrete shows elastic behavior up to only 2.28MPa and damage occurred beyond the stress. Finally, the percentage of damage of concrete due to compression obtained from analysis and experiment has been assessed and compared. Above 32 percent of concrete damage is found for 22.5 MPa in both cases.  

Numerical Simulation of Marine Recycled Concrete Specimen Based on ABAQUS

2012 ◽  
Vol 482-484 ◽  
pp. 621-626
Author(s):  
Wen Bai Liu ◽  
Wang Nan Chen ◽  
Xia Li
Keyword(s):  
Numerical Simulation ◽  
Uniaxial Compression ◽  
Sea Water ◽  
Strain Curve ◽  
Concrete Specimen ◽  
Water Erosion ◽  
Recycled Concrete ◽  
Experimental Results ◽  
Stress Strain Curve ◽  
Stress Strain

Based on ABAQUS, this article builds up a dispersion cracking model and carries out the numerical simulation of the influence of sea water erosion depth and intension upon marine recycled concrete specimen. Compared with stress-strain curve from the experiment, it can be easily found that the experimental results match well with that of simulation through the numerical simulation of uniaxial compression on average concrete, recycled concrete corroded by seawater and the same concrete after vacuum pumping, which shows two kinds of curves stay close to each other. From the results of the simulation, strain develops from the edges to the middle of the cube until it runs through the whole section, which basically corresponds with the outcome observed in the experiment.

scholarly journals Advances in Quantification of Meniscus Tensile Mechanics Including Nonlinearity, Yield, and Failure

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
John M. Peloquin ◽  
Michael H. Santare ◽  
Dawn M. Elliott
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Yield Point ◽  
Strain Field ◽  
Test Procedure ◽  
Strain Curve ◽  
Transverse Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Recruitment Model

The meniscus provides crucial knee function and damage to it leads to osteoarthritis of the articular cartilage. Accurate measurement of its mechanical properties is therefore important, but there is uncertainty about how the test procedure affects the results, and some key mechanical properties are reported using ad hoc criteria (modulus) or not reported at all (yield). This study quantifies the meniscus' stress–strain curve in circumferential and radial uniaxial tension. A fiber recruitment model was used to represent the toe region of the stress–strain curve, and new reproducible and objective procedures were implemented for identifying the yield point and measuring the elastic modulus. Patterns of strain heterogeneity were identified using strain field measurements. To resolve uncertainty regarding whether rupture location (i.e., midsubstance rupture versus at-grip rupture) influences the measured mechanical properties, types of rupture were classified in detail and compared. Dogbone (DB)-shaped specimens are often used to promote midsubstance rupture; to determine if this is effective, we compared DB and rectangle (R) specimens in both the radial and circumferential directions. In circumferential testing, we also compared expanded tab (ET) specimens under the hypothesis that this shape would more effectively secure the meniscus' curved fibers and thus produce a stiffer response. The fiber recruitment model produced excellent fits to the data. Full fiber recruitment occurred approximately at the yield point, strongly supporting the model's physical interpretation. The strain fields, especially shear and transverse strain, were extremely heterogeneous. The shear strain field was arranged in pronounced bands of alternating positive and negative strain in a pattern similar to the fascicle structure. The site and extent of failure showed great variation, but did not affect the measured mechanical properties. In circumferential tension, ET specimens underwent earlier and more rapid fiber recruitment, had less stretch at yield, and had greater elastic modulus and peak stress. No significant differences were observed between R and DB specimens in either circumferential or radial tension. Based on these results, ET specimens are recommended for circumferential tests and R specimens for radial tests. In addition to the data obtained, the procedural and modeling advances made in this study are a significant step forward for meniscus research and are applicable to other fibrous soft tissues.

Improving elastic modulus measurements for rock based on geology

2000 ◽  
Vol 6 (4) ◽  
pp. 333-346 ◽  
Author(s):  
Paul M. Santi ◽  
Jason E. Holschen ◽  
Richard W. Stephenson
Keyword(s):  
Elastic Modulus ◽  
Strain Curve ◽  
Elastic Behavior ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Rock Types ◽  
Plastic Materials ◽  
Straight Line ◽  
Elastic Plastic Materials ◽  
Engineering Projects

Abstract Since many engineering projects in rock never mobilize strengths near the uniaxial compressive strength (UCS) of the rock, elastic modulus becomes a critical parameter to describe the rock's behavior under loading. There are a number of methods available for calculating the elastic modulus from laboratory test data, and each method gives a slightly different value. The objective of this study is to evaluate the most repeatable method for each of a number of rock types, and then to develop guidelines to aid the practitioner in selecting the best method as a function of rock behavior. UCS tests were performed on 78 samples of nine rock types, including two basalts, two granites, two limestones, a quartzite, a sandstone, and a gypsum. Elastic moduli were calculated using six different methods reported in the literature or modified for this study. The modified secant and modified secant-at-50-percent-strength moduli (modified by shifting the origin to best intercept the extension of the main straight-line portion of the stress-strain curve) were the most repeatable methods for rocks with elastic and plastic-elastic behavior. Elastic-plastic materials, which have a broad concave-downward stress-strain curve, are best evaluated using the tangent modulus on the upper of two distinct straight-line segments. For materials which show creep or extended plastic deformation with no sharp failure, the secant-at-50-percent-strength modulus and modified secant-at-50-percent-strength modulus are the most repeatable.

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