The document describes research assessing the strength of reinforced concrete structures using ultrasonic pulse velocity (UPV) and Schmidt rebound hammer (SRH) non-destructive tests. The tests were used to determine relationships between compressive strength test results and NDT values. Regression analysis was used to develop models correlating compressive strength with UPV and SRH readings. The results show significant correlations for both methods, with SRH prediction found to be more efficient under certain conditions. Combining the two NDT methods improved strength estimation and produced more reliable results closer to true values.
Predicting a mathematical models of some mechanical properties of concrete ...Alexander Decker
This document summarizes a study that aimed to develop mathematical models to predict mechanical properties
of concrete from non-destructive testing methods. Specifically, the study examined properties of normal strength
concrete and high-strength concrete with compressive strengths ranging from 20-100 MPa using Schmidt
hammer and ultrasonic pulse velocity tests at ages of 7, 28, 56, and 90 days. The results showed good
correlations between compressive strength and both test methods. Relationships were also found between
modulus of elasticity, rebound number, and age of concrete. The document provides background on types of
concrete and non-destructive testing methods.
1. Three new porosity models are proposed to model the relationship between accumulative porosity and pore size in rocks. Experimental results show that one of the models, which relates porosity to the maximum pore size, most closely matches measured pore size distribution data.
2. Pore geometry, orientation, and aspect ratio influence the strength and stiffness of porous rock. Numerical simulations show that compressive strength and Young's modulus decrease as the angle between the major axis of elliptical pores and applied stress increases from 0 to 90 degrees. Strength and stiffness also depend on pore aspect ratio.
3. Two methods for modeling dry bulk modulus at varying porosities are compared - the pore space stiffness method and critical porosity
Brittle Ductile Behaviour For ( STEEL - RIENFORCED CONCRETE - CONCRETE )Ahmed Abdullah
- Steel exhibits ductile behavior by allowing large strains before rupturing or failing. It can stretch substantially under tension.
- Concrete and cast iron exhibit brittle behavior, failing abruptly with little warning once their strength limits are exceeded. Their stress-strain curves are steep with little plastic deformation.
- Reinforced concrete can show ductile behavior if designed properly with sufficient confinement and ductile reinforcement to allow inelastic deformations without collapse.
The Crack Pattern Of R.C Beams Under LoadingAhmed Abdullah
1. A reinforced concrete beam was tested under static two-point concentrated loading to study the effect of different web reinforcement arrangements on ultimate shear strength.
2. It was observed that diagonal cracks developed first in deeper beams while flexural cracks developed first in shallower beams with sufficient reinforcement.
3. The crack pattern and failure mode were similar across all test beams despite variations in web reinforcement, with diagonal cracks forming first in deeper beams.
The document discusses various mechanical properties of rocks including uniaxial compressive strength, elastic moduli, point load index, shear box testing, rebound hammer testing, sonic velocities, shear durability index, Brazilian tensile strength testing, rock density, porosity, permeability, specific gravity, unit weight, void ratio, moisture content, and degree of saturation. It provides details on methods to measure these properties and factors that influence the measurements.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
call for paper 2012, hard copy of journal, research paper publishing, where to publish research paper,
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
This document provides an introduction to the principles of engineering rock mechanics. It discusses key topics in rock mechanics including stress, strain, intact rock properties, discontinuities, rock masses, permeability, anisotropy, inhomogeneity, testing techniques, rock mass classification systems, rock dynamics, interactions in rock mechanics, excavation principles, stabilization principles, surface excavation instability mechanisms, and design and analysis of surface excavations. The document is intended to serve as a textbook on rock mechanics for engineering students and professionals.
This document presents revisions to the Hoek-Brown failure criterion for rock masses. It resolves uncertainties in applying the criterion and incorporating it into numerical models. The revised criterion sets out a recommended calculation sequence and defines equations to determine rock mass strength parameters like cohesive strength and friction angle from the Geological Strength Index rating of rock mass quality. It also distinguishes between undisturbed and disturbed rock masses using a new disturbance factor.
Predicting a mathematical models of some mechanical properties of concrete ...Alexander Decker
This document summarizes a study that aimed to develop mathematical models to predict mechanical properties
of concrete from non-destructive testing methods. Specifically, the study examined properties of normal strength
concrete and high-strength concrete with compressive strengths ranging from 20-100 MPa using Schmidt
hammer and ultrasonic pulse velocity tests at ages of 7, 28, 56, and 90 days. The results showed good
correlations between compressive strength and both test methods. Relationships were also found between
modulus of elasticity, rebound number, and age of concrete. The document provides background on types of
concrete and non-destructive testing methods.
1. Three new porosity models are proposed to model the relationship between accumulative porosity and pore size in rocks. Experimental results show that one of the models, which relates porosity to the maximum pore size, most closely matches measured pore size distribution data.
2. Pore geometry, orientation, and aspect ratio influence the strength and stiffness of porous rock. Numerical simulations show that compressive strength and Young's modulus decrease as the angle between the major axis of elliptical pores and applied stress increases from 0 to 90 degrees. Strength and stiffness also depend on pore aspect ratio.
3. Two methods for modeling dry bulk modulus at varying porosities are compared - the pore space stiffness method and critical porosity
Brittle Ductile Behaviour For ( STEEL - RIENFORCED CONCRETE - CONCRETE )Ahmed Abdullah
- Steel exhibits ductile behavior by allowing large strains before rupturing or failing. It can stretch substantially under tension.
- Concrete and cast iron exhibit brittle behavior, failing abruptly with little warning once their strength limits are exceeded. Their stress-strain curves are steep with little plastic deformation.
- Reinforced concrete can show ductile behavior if designed properly with sufficient confinement and ductile reinforcement to allow inelastic deformations without collapse.
The Crack Pattern Of R.C Beams Under LoadingAhmed Abdullah
1. A reinforced concrete beam was tested under static two-point concentrated loading to study the effect of different web reinforcement arrangements on ultimate shear strength.
2. It was observed that diagonal cracks developed first in deeper beams while flexural cracks developed first in shallower beams with sufficient reinforcement.
3. The crack pattern and failure mode were similar across all test beams despite variations in web reinforcement, with diagonal cracks forming first in deeper beams.
The document discusses various mechanical properties of rocks including uniaxial compressive strength, elastic moduli, point load index, shear box testing, rebound hammer testing, sonic velocities, shear durability index, Brazilian tensile strength testing, rock density, porosity, permeability, specific gravity, unit weight, void ratio, moisture content, and degree of saturation. It provides details on methods to measure these properties and factors that influence the measurements.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
call for paper 2012, hard copy of journal, research paper publishing, where to publish research paper,
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
This document provides an introduction to the principles of engineering rock mechanics. It discusses key topics in rock mechanics including stress, strain, intact rock properties, discontinuities, rock masses, permeability, anisotropy, inhomogeneity, testing techniques, rock mass classification systems, rock dynamics, interactions in rock mechanics, excavation principles, stabilization principles, surface excavation instability mechanisms, and design and analysis of surface excavations. The document is intended to serve as a textbook on rock mechanics for engineering students and professionals.
This document presents revisions to the Hoek-Brown failure criterion for rock masses. It resolves uncertainties in applying the criterion and incorporating it into numerical models. The revised criterion sets out a recommended calculation sequence and defines equations to determine rock mass strength parameters like cohesive strength and friction angle from the Geological Strength Index rating of rock mass quality. It also distinguishes between undisturbed and disturbed rock masses using a new disturbance factor.
The document discusses rock mass properties and the Hoek-Brown failure criterion for estimating the strength of jointed rock masses. It presents the generalized Hoek-Brown criterion equation and describes how to determine the intact rock properties of uniaxial compressive strength (σci) and the Hoek-Brown constant (mi) from triaxial test data or estimates. It also discusses estimating the Geological Strength Index (GSI) of the rock mass.
The document discusses several failure criteria for rocks, including:
1) The Mohr-Coulomb criterion, which defines shear strength as a function of cohesion and friction angle.
2) The Hoek-Brown criterion, which models the non-linear relationship between principal stresses and incorporates rock mass quality.
3) The Griffith failure criterion, which postulates that stress concentrations at flaws like cracks cause propagation and failure.
It also briefly mentions the Drucker-Prager yield criterion and that empirical criteria tailored to a specific rock type may provide the most precise failure prediction.
Stress is a concept fundamental to Rock Mechanics principles and applications. There is a pre-existing state in the rock mass and we need to understand it, both directly, and as a stress state applies to analysis and design.
Structural morphology optimization by evolutionary proceduresStroNGER2012
The paper deals with the identification of optimal structural morphologies through evolutionary procedures.
Two main approaches are considered. The first one simulates the Biological Growth (BG) of natural structures like the bones and the trees. The second one, called Evolutionary Structural Optimization (ESO), removes material at low stress level. Optimal configurations are addressed by proper optimality indexes and by a monitoring of the structural response. Design graphs suitable to this purpose are introduced and employed in the optimization of a pylon carrying a suspended roof and of a bridge under multiple loads.
All structures are subjected to degenerative effects that may
cause initiation of structural defects such as cracks which,
as time progresses, lead to the catastrophic failure or
breakdown of the structure. Thus, the importance of
inspection in the quality assurance of manufactured
products is well understood.
Nondestructive material testing with ultrasonicsFatma Abdalla
Ultrasonic pulse velocity (UPV) testing is a non-destructive testing method used to evaluate the quality and strength of concrete structures. UPV works by measuring the speed that ultrasonic pulses travel through the concrete, with higher velocities indicating higher quality concrete of greater density, homogeneity, and strength. The document describes experiments conducted to determine the relationship between UPV test results and compressive concrete strength for samples with varying water-cement ratios. UPV and compressive strength tests were performed on concrete samples at different ages. The results showed that UPV and strength increase with age and samples with lower water-cement ratios have higher UPV and strength. Correlation curves were developed to allow predicting concrete strength from
CROSS-CORRELATION OF STRESSES IN THE TRAN REINFORCEMENT UNDER SHEAR LOAD AND ...IAEME Publication
The main aim of the present study is to give an answer to the question whether the transverse reinforcement, which is required for the shear resistance of columns, must be added to the one required for the cross section confinement, or it is possible for one to substitute the other. The superposition of these reinforcements is defended by the fact that the shear reinforcement results from the shear action, while the transverse reinforcement, required by the confinement, results from the axial compression of the section. The present study is experimental and uses strain gauges, in order to check the stresses of the transverse reinforcement. Useful conclusions are drawn.
This document summarizes research on dislocations and grain boundaries in metals. It discusses how early theories defined dislocations and their role in deformation. Experiments on bicrystals in the 1930s-1950s showed grain boundaries act as barriers to dislocation motion, causing pileups. Later work established criteria for when slip can transfer between crystals based on factors like resolved shear stress and crystal orientation compatibility. Understanding dislocation-boundary interactions is crucial for predicting failure in polycrystalline metals used in applications.
The document discusses the use of computed tomography (CT) scanning to analyze the pore structure of rocks. CT scanning allows the internal density distribution of materials to be detected. Researchers have used CT scanning to observe pore morphology, fractures, and changes in rock microstructure under loading. The document focuses on using digital image processing and fractal theory to analyze CT images of rock samples and characterize pore structure. Specifically, it examines calculating the fractal dimension directly from gray-scale CT images to quantify the complexity and self-similarity of pore distributions, avoiding errors from binarizing images. Nine rock samples with different pore ratios were CT scanned at high resolution and their fractal dimensions were computed and compared.
Two 7075 aluminum samples were prepared and tested to determine their fracture toughness properties. A compact tension sample reached a maximum load of 4435 lbs before fracturing, yielding a KQ value of 89.1 ksi in1/2. However, this value was determined to be invalid for being KIC due to the ratio of maximum to critical load exceeding 1.1. A single edge notch bend sample fractured at 4295 lbs but its final crack length was too small to measure, and its KQ value of 33.1 ksi in1/2 was also found to not represent KIC. In summary, neither sample provided a valid measurement of plane strain fracture toughness KIC for the 7075 aluminum material
Vibration analysis of a cantilever beam with crack depth and crack location e...editorijrei
This document summarizes a study that analyzed the natural frequency of a cracked cantilever beam made of different metal alloys using finite element analysis. The researchers varied the crack depth and location in the beam and measured the resulting changes in natural frequency. They found that increasing crack depth or moving the crack location closer to the fixed end resulted in decreasing natural frequency. Aluminum alloy beams exhibited the highest natural frequencies while magnesium alloy beams had the lowest.
Implementation of a tension-stiffening model for the cracking nonlinear analy...Luis Claudio Pérez Tato
The development of a smeared-crack model offers a general crack-modeling method that is independent of the structural configuration. It treats cracking as a constitutive material behaviour rather than a geometric discontinuity and lends itself well to implementation in large finite element codes. This paper deals with the implementation in XC of a constitutive model for reinforced concrete elements that takes into account the increase in stiffness of a cracked member due to the development of tensile stresses in the concrete between the cracks, effect known as tension-stiffening. The nonlinear analysis in XC of fiber-like sections with this constitutive model allows for a more general, direct and intuitive evaluation of the crack amplitude than applying the mostly specific formulae developed in the standards. The numerical results obtained by the program compare extremely well with existing designing results issued by other applied methods.
2.evaluation of crack propagation phenomenon in bituminous mixEditorJST
Crack propagation was experimentally simulated using semicircular specimen with a crack initiated on one side. The work shows that the rate of crack propagation can be described by a power relationship between the stiffness of the mixture and the number of cycles to failure, which is mixture and binder dependent.
The document discusses failure of engineering materials. It describes that failure is undesirable as it puts lives and economics at risk. While causes of failure are known, prevention is difficult. Common causes are improper material selection, processing, or design flaws. The document then goes on to describe different types of failure like brittle and ductile fracture as well as fatigue failure. It provides details on how these failures occur and how they can be tested and characterized.
This document discusses several index tests used by engineers and geologists to determine the strength and deformation properties of soils and rocks in the field. It describes the Brazilian test, point load index test, impact test, and Schmidt hammer rebound test. The Brazilian test measures tensile strength. The point load index test uses a handheld device to apply a compressive force and induce tensile cracking. The impact test evaluates coal degradation. The Schmidt hammer rebound test measures surface hardness in a non-destructive manner using rebound value correlations. These index tests provide immediate preliminary results without extensive preparation and can be correlated to laboratory strength tests.
Plasticity, Theory of Plasticity ,Creep in concrete ,Creep, Stiffness ,Elasticity ,Plasticity ,Euler-Bernoulli beam equation, Buckling, Ductility VS Malleability, Ductile Materials, Brittle Materials ,Modulus of Elasticity, Plastic Strain, Tensile Strength, Yield Strength, Ultimate Strength, Solid mechanics or Mechanics of solids, Strength of Materials, Types of forces, Normal forces, Fatigue , Resilience, Unit of Resilience, Modulus of rigidity , Modulus of Resilience, Modulus of Toughness Poisson’s Ratio.
A fracture mechanics based method for prediction ofSAJITH GEORGE
The document presents a fracture mechanics-based method for predicting cracking in circular and elliptical concrete rings undergoing restrained shrinkage. It describes an experimental program using different ring geometries and material tests to determine properties. A numerical model is developed using ANSYS to model the restrained shrinkage process and calculate stress intensity factors. The model uses a fictitious temperature field to simulate shrinkage and determines cracking age by comparing driving and resistance curves. It finds cracking occurs earlier in elliptical rings and the method accurately predicts experimental cracking ages.
Numerical and Analytical Solutions for Ovaling Deformation in Circular Tunnel...IDES Editor
Ovaling deformations develop when waves propagate
perpendicular to the tunnel axis. Two analytical solutions are
used for estimating the ovaling deformations and forces in
circular tunnels due to soil–structure interaction under
seismic loading. In this paper, these two closed form solutions
will be described briefly, and then a comparison between these
methods will be made by changing the ground parameters.
Differences between the results of these two methods in
calculating the magnitudes of thrust on tunnel lining are
significant. For verifying the results of these two closed form
solutions, numerical analyses were performed using finite
element code (ABAQUS program). These analyses show that
the two closed form solutions provide the same results only
for full-slip condition.
Shear rate threshold for the boundary slip in dense polymer filmsNikolai Priezjev
This document summarizes a study on the shear rate threshold for boundary slip in dense polymer films using molecular dynamics simulations. The key findings are:
1) The slip length Ls is negative at low shear rates due to a viscous interfacial layer and increases rapidly at higher shear rates when the layer viscosity is reduced.
2) The friction coefficient at the melt/solid interface undergoes a transition from nearly constant to a power law decay with slip velocity.
3) At large slip velocities, the friction coefficient is determined by the product of the structure factor peak and contact density of the first fluid layer.
The document summarizes scaling laws observed for geological faults. It finds that fault displacement scales linearly with fault length over 7 orders of magnitude, with a proportionality constant of around 10-2. Faults propagate through the formation of brittle process zones of microcracks around the fault tips. The width of these process zones increases linearly with fault length. These observations are consistent with an elastic-plastic crack model where fracture energy increases linearly with fault length. Similar scaling laws apply to earthquakes and other fractures in rock.
Ultra sonic pulse velocity test for concrete as nondestructive test method in...Mohammed Layth
Ultrasonic pulse velocity (UPV) testing provides non-destructive evaluation of concrete by transmitting ultrasonic pulses through the material. The pulse velocity is dependent on concrete density and elastic properties, which relate to quality and compressive strength. UPV can detect voids, cracks, and defects by measuring the time it takes pulses to travel between transducers placed on the surface. Well-trained operators using modern UPV equipment can reliably examine concrete interior and determine properties like uniformity, cracking, strength, layer thickness, and elastic modulus. However, UPV has limitations and cannot replace destructive testing.
Ultrasonic pulse velocity test for concreteCivil Engineer
Ultrasonic pulse velocity (UPV) testing uses ultrasonic waves to assess the quality and uniformity of concrete in a non-destructive manner. UPV testing involves transmitting ultrasonic pulses through concrete and measuring the transit time, from which the pulse velocity can be calculated. Higher pulse velocities indicate higher quality concrete with fewer voids or defects. UPV testing can detect voids, cracks, and changes in concrete properties. It provides information on concrete strength and uniformity that can be used to evaluate structures and estimate deterioration.
The document discusses rock mass properties and the Hoek-Brown failure criterion for estimating the strength of jointed rock masses. It presents the generalized Hoek-Brown criterion equation and describes how to determine the intact rock properties of uniaxial compressive strength (σci) and the Hoek-Brown constant (mi) from triaxial test data or estimates. It also discusses estimating the Geological Strength Index (GSI) of the rock mass.
The document discusses several failure criteria for rocks, including:
1) The Mohr-Coulomb criterion, which defines shear strength as a function of cohesion and friction angle.
2) The Hoek-Brown criterion, which models the non-linear relationship between principal stresses and incorporates rock mass quality.
3) The Griffith failure criterion, which postulates that stress concentrations at flaws like cracks cause propagation and failure.
It also briefly mentions the Drucker-Prager yield criterion and that empirical criteria tailored to a specific rock type may provide the most precise failure prediction.
Stress is a concept fundamental to Rock Mechanics principles and applications. There is a pre-existing state in the rock mass and we need to understand it, both directly, and as a stress state applies to analysis and design.
Structural morphology optimization by evolutionary proceduresStroNGER2012
The paper deals with the identification of optimal structural morphologies through evolutionary procedures.
Two main approaches are considered. The first one simulates the Biological Growth (BG) of natural structures like the bones and the trees. The second one, called Evolutionary Structural Optimization (ESO), removes material at low stress level. Optimal configurations are addressed by proper optimality indexes and by a monitoring of the structural response. Design graphs suitable to this purpose are introduced and employed in the optimization of a pylon carrying a suspended roof and of a bridge under multiple loads.
All structures are subjected to degenerative effects that may
cause initiation of structural defects such as cracks which,
as time progresses, lead to the catastrophic failure or
breakdown of the structure. Thus, the importance of
inspection in the quality assurance of manufactured
products is well understood.
Nondestructive material testing with ultrasonicsFatma Abdalla
Ultrasonic pulse velocity (UPV) testing is a non-destructive testing method used to evaluate the quality and strength of concrete structures. UPV works by measuring the speed that ultrasonic pulses travel through the concrete, with higher velocities indicating higher quality concrete of greater density, homogeneity, and strength. The document describes experiments conducted to determine the relationship between UPV test results and compressive concrete strength for samples with varying water-cement ratios. UPV and compressive strength tests were performed on concrete samples at different ages. The results showed that UPV and strength increase with age and samples with lower water-cement ratios have higher UPV and strength. Correlation curves were developed to allow predicting concrete strength from
CROSS-CORRELATION OF STRESSES IN THE TRAN REINFORCEMENT UNDER SHEAR LOAD AND ...IAEME Publication
The main aim of the present study is to give an answer to the question whether the transverse reinforcement, which is required for the shear resistance of columns, must be added to the one required for the cross section confinement, or it is possible for one to substitute the other. The superposition of these reinforcements is defended by the fact that the shear reinforcement results from the shear action, while the transverse reinforcement, required by the confinement, results from the axial compression of the section. The present study is experimental and uses strain gauges, in order to check the stresses of the transverse reinforcement. Useful conclusions are drawn.
This document summarizes research on dislocations and grain boundaries in metals. It discusses how early theories defined dislocations and their role in deformation. Experiments on bicrystals in the 1930s-1950s showed grain boundaries act as barriers to dislocation motion, causing pileups. Later work established criteria for when slip can transfer between crystals based on factors like resolved shear stress and crystal orientation compatibility. Understanding dislocation-boundary interactions is crucial for predicting failure in polycrystalline metals used in applications.
The document discusses the use of computed tomography (CT) scanning to analyze the pore structure of rocks. CT scanning allows the internal density distribution of materials to be detected. Researchers have used CT scanning to observe pore morphology, fractures, and changes in rock microstructure under loading. The document focuses on using digital image processing and fractal theory to analyze CT images of rock samples and characterize pore structure. Specifically, it examines calculating the fractal dimension directly from gray-scale CT images to quantify the complexity and self-similarity of pore distributions, avoiding errors from binarizing images. Nine rock samples with different pore ratios were CT scanned at high resolution and their fractal dimensions were computed and compared.
Two 7075 aluminum samples were prepared and tested to determine their fracture toughness properties. A compact tension sample reached a maximum load of 4435 lbs before fracturing, yielding a KQ value of 89.1 ksi in1/2. However, this value was determined to be invalid for being KIC due to the ratio of maximum to critical load exceeding 1.1. A single edge notch bend sample fractured at 4295 lbs but its final crack length was too small to measure, and its KQ value of 33.1 ksi in1/2 was also found to not represent KIC. In summary, neither sample provided a valid measurement of plane strain fracture toughness KIC for the 7075 aluminum material
Vibration analysis of a cantilever beam with crack depth and crack location e...editorijrei
This document summarizes a study that analyzed the natural frequency of a cracked cantilever beam made of different metal alloys using finite element analysis. The researchers varied the crack depth and location in the beam and measured the resulting changes in natural frequency. They found that increasing crack depth or moving the crack location closer to the fixed end resulted in decreasing natural frequency. Aluminum alloy beams exhibited the highest natural frequencies while magnesium alloy beams had the lowest.
Implementation of a tension-stiffening model for the cracking nonlinear analy...Luis Claudio Pérez Tato
The development of a smeared-crack model offers a general crack-modeling method that is independent of the structural configuration. It treats cracking as a constitutive material behaviour rather than a geometric discontinuity and lends itself well to implementation in large finite element codes. This paper deals with the implementation in XC of a constitutive model for reinforced concrete elements that takes into account the increase in stiffness of a cracked member due to the development of tensile stresses in the concrete between the cracks, effect known as tension-stiffening. The nonlinear analysis in XC of fiber-like sections with this constitutive model allows for a more general, direct and intuitive evaluation of the crack amplitude than applying the mostly specific formulae developed in the standards. The numerical results obtained by the program compare extremely well with existing designing results issued by other applied methods.
2.evaluation of crack propagation phenomenon in bituminous mixEditorJST
Crack propagation was experimentally simulated using semicircular specimen with a crack initiated on one side. The work shows that the rate of crack propagation can be described by a power relationship between the stiffness of the mixture and the number of cycles to failure, which is mixture and binder dependent.
The document discusses failure of engineering materials. It describes that failure is undesirable as it puts lives and economics at risk. While causes of failure are known, prevention is difficult. Common causes are improper material selection, processing, or design flaws. The document then goes on to describe different types of failure like brittle and ductile fracture as well as fatigue failure. It provides details on how these failures occur and how they can be tested and characterized.
This document discusses several index tests used by engineers and geologists to determine the strength and deformation properties of soils and rocks in the field. It describes the Brazilian test, point load index test, impact test, and Schmidt hammer rebound test. The Brazilian test measures tensile strength. The point load index test uses a handheld device to apply a compressive force and induce tensile cracking. The impact test evaluates coal degradation. The Schmidt hammer rebound test measures surface hardness in a non-destructive manner using rebound value correlations. These index tests provide immediate preliminary results without extensive preparation and can be correlated to laboratory strength tests.
Plasticity, Theory of Plasticity ,Creep in concrete ,Creep, Stiffness ,Elasticity ,Plasticity ,Euler-Bernoulli beam equation, Buckling, Ductility VS Malleability, Ductile Materials, Brittle Materials ,Modulus of Elasticity, Plastic Strain, Tensile Strength, Yield Strength, Ultimate Strength, Solid mechanics or Mechanics of solids, Strength of Materials, Types of forces, Normal forces, Fatigue , Resilience, Unit of Resilience, Modulus of rigidity , Modulus of Resilience, Modulus of Toughness Poisson’s Ratio.
A fracture mechanics based method for prediction ofSAJITH GEORGE
The document presents a fracture mechanics-based method for predicting cracking in circular and elliptical concrete rings undergoing restrained shrinkage. It describes an experimental program using different ring geometries and material tests to determine properties. A numerical model is developed using ANSYS to model the restrained shrinkage process and calculate stress intensity factors. The model uses a fictitious temperature field to simulate shrinkage and determines cracking age by comparing driving and resistance curves. It finds cracking occurs earlier in elliptical rings and the method accurately predicts experimental cracking ages.
Numerical and Analytical Solutions for Ovaling Deformation in Circular Tunnel...IDES Editor
Ovaling deformations develop when waves propagate
perpendicular to the tunnel axis. Two analytical solutions are
used for estimating the ovaling deformations and forces in
circular tunnels due to soil–structure interaction under
seismic loading. In this paper, these two closed form solutions
will be described briefly, and then a comparison between these
methods will be made by changing the ground parameters.
Differences between the results of these two methods in
calculating the magnitudes of thrust on tunnel lining are
significant. For verifying the results of these two closed form
solutions, numerical analyses were performed using finite
element code (ABAQUS program). These analyses show that
the two closed form solutions provide the same results only
for full-slip condition.
Shear rate threshold for the boundary slip in dense polymer filmsNikolai Priezjev
This document summarizes a study on the shear rate threshold for boundary slip in dense polymer films using molecular dynamics simulations. The key findings are:
1) The slip length Ls is negative at low shear rates due to a viscous interfacial layer and increases rapidly at higher shear rates when the layer viscosity is reduced.
2) The friction coefficient at the melt/solid interface undergoes a transition from nearly constant to a power law decay with slip velocity.
3) At large slip velocities, the friction coefficient is determined by the product of the structure factor peak and contact density of the first fluid layer.
The document summarizes scaling laws observed for geological faults. It finds that fault displacement scales linearly with fault length over 7 orders of magnitude, with a proportionality constant of around 10-2. Faults propagate through the formation of brittle process zones of microcracks around the fault tips. The width of these process zones increases linearly with fault length. These observations are consistent with an elastic-plastic crack model where fracture energy increases linearly with fault length. Similar scaling laws apply to earthquakes and other fractures in rock.
Ultra sonic pulse velocity test for concrete as nondestructive test method in...Mohammed Layth
Ultrasonic pulse velocity (UPV) testing provides non-destructive evaluation of concrete by transmitting ultrasonic pulses through the material. The pulse velocity is dependent on concrete density and elastic properties, which relate to quality and compressive strength. UPV can detect voids, cracks, and defects by measuring the time it takes pulses to travel between transducers placed on the surface. Well-trained operators using modern UPV equipment can reliably examine concrete interior and determine properties like uniformity, cracking, strength, layer thickness, and elastic modulus. However, UPV has limitations and cannot replace destructive testing.
Ultrasonic pulse velocity test for concreteCivil Engineer
Ultrasonic pulse velocity (UPV) testing uses ultrasonic waves to assess the quality and uniformity of concrete in a non-destructive manner. UPV testing involves transmitting ultrasonic pulses through concrete and measuring the transit time, from which the pulse velocity can be calculated. Higher pulse velocities indicate higher quality concrete with fewer voids or defects. UPV testing can detect voids, cracks, and changes in concrete properties. It provides information on concrete strength and uniformity that can be used to evaluate structures and estimate deterioration.
Predicting a mathematical models of some mechanical properties of concrete ...Alexander Decker
This document summarizes a study that aimed to develop mathematical models to predict mechanical properties
of concrete from non-destructive testing methods. The study evaluated properties of normal strength concrete
(NSC) and high strength concrete (HSC) using Schmidt hammer and ultrasonic pulse velocity tests at ages of 7,
28, 56, and 90 days. Good correlations were found between compressive strength and both test methods. The
ultrasonic pulse velocity in HSC increased 8% from 28 to 90 days. Relationships were developed between
modulus of elasticity, rebound number, and age. The percentage increase in ultrasonic pulse velocity from 7 to
90 days was 3.5-
IRJET- In-Situ Testing of Concrete Structures – A ReviewIRJET Journal
This document reviews various in-situ testing methods for concrete structures. It discusses common non-destructive testing (NDT) methods like rebound hammer testing and ultrasonic pulse velocity testing that can evaluate concrete strength and homogeneity. The document summarizes several studies that have investigated using these NDT methods to predict compressive concrete strength by correlating NDT results with destructive testing data. It concludes that while NDT methods are useful for assessing concrete properties, interpretation of test results can be difficult due to various factors affecting measurements.
Characterization of Differential Concrete Mix Designs by Ultrasonic Pulse Vel...IRJET Journal
This document summarizes a study that characterized different concrete mix designs using ultrasonic pulse velocity testing. Six mix designs were tested with varying water-cement ratios, slump, and compressive strengths. Concrete cubes were cast and tested for ultrasonic pulse velocity and compressive strength at various ages. The objectives were to examine how drying conditions and mix properties influence ultrasonic pulse velocity results, determine the relationship between velocity and compressive strength, and develop charts relating non-destructive test results to mix designs. Results aimed to improve accuracy of using non-destructive methods to evaluate concrete strength.
IRJET - To Determine the Strength of Existing Structure through NDT Testi...IRJET Journal
This document discusses using non-destructive testing (NDT) methods like rebound hammer testing and ultrasonic pulse velocity testing to determine the strength of existing concrete structures. The researchers performed these NDT tests on columns, beams, and slabs of an existing building. Test results showed the concrete quality was medium to doubtful based on ultrasonic pulse velocity tests, and likely 18-22 MPa compressive strength based on rebound hammer tests. The study concluded NDT is an effective way to evaluate existing structures without damaging them.
1) The study examines the effect of age on ultrasonic pulse velocity (UPV) in concrete and mortar specimens through direct, indirect, and semi-direct testing methods at 7, 28, and 56 days.
2) UPV was found to increase more rapidly between 7 and 28 days than 28 to 56 days. Mortar specimens showed a greater increase in UPV with age than concrete.
3) UPV results varied between the top and bottom surfaces of semi-direct tested concrete beams, with the bottom surface yielding higher velocities.
Constructing a mathematical models to predict compressive strength of concIAEME Publication
The document presents a study that constructed mathematical models to predict the compressive strength of concrete from non-destructive testing methods. The study used normal strength concrete and high strength concrete mixes with cement, fine and coarse aggregates, and silica fume. Non-destructive tests including the Schmidt hammer test and ultrasonic pulse velocity test were performed on samples at various ages, along with destructive compressive strength tests. Relationships between compressive strength and test results were established. The results showed correlations between strength and test values, and that combined non-destructive test methods increased strength prediction reliability.
Non destructive evaluation of in-situ strength of high strength concreteIAEME Publication
This document summarizes a study on evaluating the in-situ strength of high-strength concrete (HSC) structures using non-destructive testing (NDT) techniques. Tests were conducted on HSC mixes with compressive strengths ranging from 50-130 MPa. Ultrasonic pulse velocity (UPV) and rebound hammer tests were performed on cubes before destructive compression testing. Correlation curves were developed between destructive and non-destructive parameters. Equations were formulated to correlate compressive strength with UPV, rebound number, and a combined method. Field tests on various structures found about a 10% variation between predicted strength from equations and experimental strength from cores. The study concluded that NDT techniques can reliably
Non destructive evaluation of in-situ strength of high strength concreteIAEME Publication
This document summarizes a study on evaluating the in-situ strength of high-strength concrete (HSC) structures using non-destructive testing (NDT) techniques. Tests were conducted on HSC mixes with compressive strengths ranging from 50-130 MPa. Ultrasonic pulse velocity (UPV) and rebound hammer tests were performed on cubes before destructive compression testing. Correlation curves were developed between destructive and non-destructive parameters. Equations were formulated to correlate compressive strength with UPV, rebound number, and a combined method. Field tests on various structures found about a 10% variation between predicted strength from equations and experimental strength from cores. The study concluded that NDT techniques can reliably
This document discusses the fatigue behavior of high volume fly ash concrete (HVFAC) under constant amplitude and compound loading. It presents test results of 95 HVFAC and 100 conventional concrete prism specimens tested under constant amplitude flexural fatigue loading. It also discusses test results of 24 HVFAC specimens under compound fatigue loading to verify the validity of Miner's hypothesis for HVFAC. Probability distributions were developed from the fatigue life test results and S-N curves were established relating stress level to fatigue life for both concretes. The findings provide useful data on fatigue performance of HVFAC.
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity
Measurements of Geophysical Velocity for Building InspectionAli Osman Öncel
The document describes a study that evaluated the compressive strength of concrete using nondestructive testing methods. Specifically, it used the rebound hammer test, ultrasonic pulse velocity test, and a combined method that uses both. Statistical analysis, including simple and multiple linear regression, was used to develop correlations between the nondestructive test results and actual compressive strengths from cylinder and core samples. The combined method was found to improve the accuracy of estimating compressive strength by taking into account factors that influence each test method differently. Equations derived from the statistical analysis can be used to predict compressive strength on site based on rebound hammer and ultrasonic pulse velocity measurements.
Non destructive testing on concrete ( ndt )RakeshRaki94
This document discusses non-destructive testing methods for concrete, including various surface hardness, rebound hammer, penetration, dynamic, combined, radioactive, magnetic, and acoustic emission techniques. It focuses on rebound hammer and pulse velocity methods. For rebound hammers, it describes how the hammer impacts the surface and the rebound number indicates hardness. Pulse velocity methods measure the time of travel for ultrasonic or mechanical pulses, with direct, indirect, and surface transmission techniques. Suggested velocity criteria are provided to assess concrete quality.
This document discusses several methods for estimating the fatigue life of Type 304LN stainless steel under strain-controlled cyclic loading, including the four-point correlation method, modified four-point correlation method, universal slopes method, modified universal slopes method, uniform material law, hardness method, median's method, and methods proposed by Mitchell and Basan. The results of estimating fatigue life using these methods are compared to experimental strain-controlled fatigue test results on Type 304LN stainless steel at various strain amplitudes. Most methods overestimate fatigue life except the median's method, which provides a reasonably accurate estimation of fatigue life, especially at higher strain amplitudes. Basan's method, modified universal slopes method, and uniform material law also predict fatigue life with reasonable accuracy
The rebound hammer test provides a non-destructive way to estimate the compressive strength of concrete. The test works by measuring the rebound of an elastic mass that strikes the concrete surface. A higher rebound indicates higher compressive strength. The test is simple to perform but only provides information about the local area tested and does not evaluate other properties. The ultrasonic pulse velocity test uses transducers to transmit and receive ultrasonic pulses through concrete. Faster pulse velocities indicate higher quality, more uniform concrete. The test can identify voids, cracks, and other discontinuities. Both tests provide non-destructive ways to evaluate concrete properties but require trained operators and consideration of various factors that affect readings.
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Techshore Inspection Services offers QA/QC Civil-concrete NDT and Quantity surveying & Cost estimation. It is very important to ensure that the structure is suitable for its intended use after the concrete has hardened. For this purpose, we can perform non-destructive testing that does not damage the concrete. Non-destructive testing can be applied to both old and new structures. Lets understand the various concrete ndt methods
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2. 214 Sci. Res. Essays
Figure 1. Pulse velocity testing equipment (PUNDIT).
use of Ultrasonic Pulse Velocity (UPV) to the non- TEST EQUIPMENTS
destructive assessment of concrete quality has been
The UPV equipment (e.g. PUNDIT) includes a transducer, a
extensively investigated for decades. It is more likely to receiver and an indicator for showing the time of travel from the
assess the quality and characteristics of at site concrete transducer to the receiver (Figure 1) (Pundit manual 1998).
and composed of measuring the transit time of an Ultrasonic pulse uses fast potential changes to create vibration that
ultrasonic pulse velocity through the concrete (Solís- leads to its basic frequency. The transducer is firmly attached to
Carcaño and Moreno, 2008). The velocity of the signals concrete surface to vibrate the concrete. The pulses go through the
pass through in a concrete depends on the density and concrete and reach the receiver (ASTM, 2002).
The pulse velocity can be determined from the following
elasticity. According to the theory of the sound equation:
propagation in solids, the sound transmission velocity is
depends on the density and the elastic modulus of the V=L/T (1)
concrete and it is independent of the excitation frequency
that causes the agitation. The excitation may cause where V = pulse velocity (km/s), L = path length (cm), T = transit
time (µs).
longitudinal (compression) waves and transverse (shear)
waves in the concrete (Hobbs and Tchoketch, 2007). Based on this technique, the velocity of sound in a concrete is
Numerous data and the correlation relationships between related to the concrete modulus of elasticity:
the strength and pulse velocity of concrete have been
arranged. Galan (1967) reported a regression analysis to
predict compressive strength of concrete based on sound
(2)
characteristics like UPV and estimated concrete strength
and damping constant. where, E = modulus of elasticity, ρ=density of the concrete.
A particular transducer must be used in the purpose of
determining dynamic elastic modulus and Poisson’s ratio The transducer detects the pulses which reach first and it is usually
of concrete and based on the wave type (longitudinal or the leading edge of the longitudinal vibration. The positions of pulse
velocity measurements are categorized in, a: Opposite faces (direct
transverse). There is not any standard correlation
transmission), b: Adjacent faces (semi-direct transmission) or c:
between concrete compressive strength and the Same face (indirect or surface transmission) which are shown in
ultrasonic pulse velocity and this matter was controlled by Figure 2.
many aspects (Turgut, 2004). However, the value of this In this study, the direct method is used for column, semi-direct
method to estimate the quality of concrete is based on method for beam and in-direct method for slab. The latter method is
the fact that the curve slope between the two variables is suitable for quality assessment in concrete while the pulse velocity
depends only on modulus of elasticity not shape of concrete.
comparatively coherent. Consequently, a calibration The Schmidt Rebound Hammer (SRH), known as the Rebound
curve between compressive strength and ultrasonic pulse or Impact Hammer test is considered as a non-destructive method,
velocity obtained for each concrete is needed otherwise widely used for assessing rock quality materials considering surface
not enough dependability would be attained (Popovics rebound hardness that is related to the compressive strength. This
and Popovics, 1997). The nature of the aggregates which test is fast, cheap and an important guide test for rock material
is one of the major aspects that is generally more description. The methodology of the SRH test is expected to ensure
the trustworthy data achievement and on site or the laboratory
plentiful, rigid, and resistant part in concrete influences analysis (Amasaki, 1991). SRH includes a spring loaded piston with
this correlation and changes the elastic properties of the steel mass (Figure 3) as explained In British Code (BS1881 part
concrete (Sturrup et al., 1984). 202, 1986). The SRH as a hardness test works in a way that the
3. Shariati et al. 215
Figure 2. Direct (a), Semi-direct (b) Indirect (surface) transmission (c).
Figure 3. Operational system of a Schmidt Rebound Hammer (SRH).
rebound of an elastic material is related to its surface hardness angle of the hammer affects the result. After the impaction, the
against the hitting material. Based on the standard, the energy rebound readings should be recorded. There is not any distinctive
attracted by the concrete is according to its strength rebound of an relationship between hardness and strength of concrete but
elastic material (ACI Committee, 1988). The kinetic energy equals experimental data relationships can be obtained from a given
to the energy released by the key spring of the piston in the straight concrete (Basu and Aydin, 2004). A common normalization
impact direction which it is released onto the hammer (Basu and procedure which could be used for any type of Schmidt hammer
Aydin, 2004) even if this test involves impact problems and the with the same nominal design fired in any direction (Galan, 1967).
related stress-wave propagation (Qasrawi, 2000). Concrete surface However, the relationship between hardness and concrete strength
should be carefully selected and prepared to be used by polishing depends on issues affecting the concrete surface such as
so that the test surface is then ground smooth. A fixed power then saturation degree, temperature, carbonation surface preparation
applies by pushing the hammer against the surface. The slope and location (Willetts, 1958; Amasaki, 1991) also the type of
4. 216 Sci. Res. Essays
Figure 4. UPV and SRH tests in site.
Table 1. Concrete mix proportion.
Cement Coarse aggregate Fine aggregate Water Retarder SP
Ingredient
(Kg/m3) (Kg/m3) (Kg/m3) (kg/m3) (ml/ m3) (ml/m3)
Amount 390 1020 805 195 1150 2305
aggregate, mix proportions, hammer type, and hammer inclination this research to obtain a mathematical relationship using SRH and
affect the results (Grieb, 1958). Surfaces with scaling, UPV for investigation the reinforced concrete buildings.
honeycombing, high porosity, or rough texture must be avoided. All
samples must be at the same age, moisture conditions and the
TEST PROGRAMME
same carbonation degree (Qasrawi, 2000). It is essential to take 10
to 12 readings for each surface and by the existence of aggregate Main members of an existing structure including column, beam and
and voids instantly under the plunger the test is sensitive (Neville slab were tested by NDT methods (Figure 4).
and Brooks, 1987).
Obviously by just using the SRH, the concrete surfaces reflect.
Based on British Code (BS1881 part 202, 1986), the measured Material properties and test procedure
number by rebound hammer is an indication of the first 30-mm
depth of concrete. Another research (Aydin, 2009) recommended a Concrete mix proportion (Table1) used by the construction
method for determining the Schmidt hammer rebound hardness. company in Malaysia respect to (M523 part 2 1993) which is the
According to a research by Teodoru (1989), the SRH obtained Standard for specifying, production and compliance criteria for the
results are only delegate of the outer concrete layer with a ready-mixed concrete supply in Malaysia that was adopted from
thickness of 30 to 50 mm. The simplicity of obtaining the suitable British codes (BS5328, 1976).
correlation data in a given instant causes the rebound hammer to The design slump would be limited from 25 to 75 mm and the
be most useful for quick surveying in large areas of similar concrete coarse aggregate used has a nominal maximum size of 19 mm
types in the considered construction (Qasrawi, 2000). Also the while the fine aggregate has a fineness modulus of 2.70.
advantages of using rebound hammer in concrete presented The relationship between compression strength of concrete
(Neville, 1973) and stated that the rebound hammer test should not collected from crashing test records and estimated results from
be accepted as a replacement for compression test but another NDT’s records was established and compared. Both, the Schmidt
researcher (Bilgin et al., 2002) strongly showed the importance of Rebound Hammer (SRH) and the Ultrasonic Pulse Velocity (UPV)
SRH used for mechanical excavators with gathering arms, such as tests, are only useful provided that a correlation can be developed
tunnel heading machines, may extensively improve daily advance between the rebound number/ultrasonic pulse velocity readings and
rates. This is a very easy test to conduct and the rebound value is a the strength of the same concrete. This study planned to adapt the
good symptom of rock characteristics and gives significant Schmidt Rebound Hammer (SRH) equipment and the Ultrasonic
correlation with net breaking rates of rebound hammers. Pulse Velocity (UPV) tester to investigate the concrete structures in
The non-destructive methods for evaluation of the actual site. A combined method for the above two tests is established in
compressive strength of concrete in existing structures are based order to improve the strength estimation of concrete.
on experimental relations between strength and non-destructive
parameters. Manufacturers typically give experimental relationships TEST SPECIMENS
for their own testing system of devices.
Regression analysis approach is used as destructive testing in All specimens for compression test were cubes of 150 mm side
5. Shariati et al. 217
Figure 5. Rebound number/compressive strength calibration curve.
length for concrete strength recording. The loading speed for 150 Schmidt Rebound Hammer (SRH) results
mm side length cube was used is 13.5kN/s. The compressive
strength of hardened concrete was determined by using specimens The best fit line, which represents the relationship
tested at 1, 3, 7, and 14 days intervals. Two specimens were tested
between the rebound number and the compressive
and the averaged results for each strength test at each age were
used. strength of concrete, is a straight line which has the
following equation:
SCHMIDT REBOUND HAMMER (SRH) TEST fc(R)=1.7206R - 26.595 (3)
The rebound number was obtained by taking 36 readings for
column, 18 readings for beam and 24 readings for slab. Readings where, R is the rebound number.
were done in a horizontal position for beam/column and vertical
position for slab as described in British codes (BS1881 part 202 The number of used data in the correlation is n = 18. The
1986). The mean rebound number and mean strength obtained R2 value is found to be 93.6%, which indicates a
from compression strength test of specimens provided the data to
construct a correlation curve.
significant correlation. The 95% prediction interval is quite
narrow (f c ±4.42 MPa) where most of the data values are
within this interval (Figure 5). The standard error are
ULTRASONIC PULSE VELOCITY (UPV) TEST found to be S.E. = 2.1024.
Each concrete member for UPV test was tested as described in
British codes (EN 12504-4, 2004). The pulse velocities are
measured in direct and semi direct method between opposite faces Ultrasonic Pulse Velocity (UPV) results
for column, adjacent faces for beam and indirect method for slab.
The UPV readings, there are 36 readings for beam, 12 readings for
column and 20 readings for slab. For this test also, the mean
The best-fit curve that represents the relationship has the
strength obtained from UPV and mean strength obtained from each following equation:
member provided the data to achieve a correlation curve.
fc(V)=15.533V - 34.358 (4)
ANALYSIS AND RESULTS where, V is the ultrasonic pulse velocity.
Calibration curves for each test method are drawn using The number of data used in the correlation n = 18. The
regression analysis. The correlation relation between R2 value is found to be 91.9%, which indicates a
predicted and compression strength of concrete are significant correlation. The 95% prediction interval is quite
represented by plotting the averages of rebound wider than the previous one (f c ±11.39 MPa) where the
number/ultrasonic pulse velocity against the compressive most data values are within this interval. (Figure 6) and
strength of each member. the standard error are found to be S.E. = 3.3746.
6. 218 Sci. Res. Essays
Figure 6. Ultrasonic Pulse Velocity (UPV)/compressive strength calibration curve.
Combined analysis author’s calibration curve is higher than the other ones,
achieved by other researchers (Figures 7 and 8) and
Dependability of results was enhanced while the SRH calibration curve is almost close to the
combination of two NDT methods was used together. To manufacturer’s calibration curve but for UPV calibration
analyze the combined method, a multiple regression was curve is the furthest one from the manufacturer’s
used to predict the concrete compressive strength. calibration curve. The effect of different features such as
Consequently, the results showed a significant correlation the proportions of aggregate, water/cement ratio, curing
between compression strength, UPV and rebound could be the cause of this difference and it does not
numbers together (Mahdi Shariati, University Putra mean less confident of this method.
Malaysia, M.S thesis 2008). The compressive strength
can be predicted from the combined ultrasonic pulse
velocity and rebound number using equation 5 with R2 = CONCLUSION
0.95 where the n=18 and S.E. =1.8491 and the 95%
prediction interval is quite narrow (f c ±3.7 MPa): The rebound number method appears to be more
2 competent in forecasting the compression strength of
fc(V)=-173.04+4.07V +57.96V+1.31R (5)
concrete compare than the ultrasonic pulse velocity
where, V is the ultrasonic pulse velocity and R is the method. However, the development of calibration curves
rebound number. to conform both the Schmidt Rebound Hammer (SRH)
and the UPV testing techniques for usual concrete mixes
showed that the use of these two methods individually is
DISCUSSION not appropriate to predict an accurate estimation for
concrete strength. The use of the Schmidt Rebound
Obviously, the Schmidt Hammer Rebound (SRH) with Hammer (SRH) test for strength estimation of in situ
best fit line has a better correlation than UPV. The concrete alone is not recommended unless using an
regression model achieved from combination of two NDT available specific calibration chart.
methods are more precise and closer to the experimental The use of combined methods produces more
results to those results that were achieved from individual trustworthy results that are closer to the true values when
methods. compared to the use of the above methods individually.
An acceptable level of precision was additionally
COMPARISON WITH OTHER PUBLISHED WORKS appreciated for concrete strength estimation. Therefore,
for engineering investigation, the resulting regression
The compressive strength of concrete predicted by the model for strength evaluation could be used securely for
7. Shariati et al. 219
Research by author
Dreux (1985)
Rebound number
Figure 7. Comparison of Schmidt Rebound Hammer (SRH) test with others.
Research by author
Figure 8. Comparison of Ultrasonic Pulse Velocity (UPV) test with others.
8. 220 Sci. Res. Essays
concrete strength estimation. Hobbs BM, Tchoketch K (2007). Non-destructive testing techniques for
the forensic engineering investigation of reinforced concrete buildings.
Forensic Sci. Int., 167(2-3): 167-172.
Leshchinsky A (1991). Non-destructive methods Instead of specimens
ACKNOWLEDGMENT and cores, quality control of concrete structures, pp. 377–386.
Malaysian Standards M (1993). 523 Part 2 Specification for concrete,
The author highly appreciates assistance of Mr. Sina including ready-mixed concrete.
Neville A (1973). Properties of concrete, Pitman London.
Mirzapour Mounes for experimental assistance. Neville A, Brooks J (1987). Concrete technology. Mag. Concrete
Research 39: 140.
Popovics S, Popovics J (1997). A critique of the ultrasonic pulse velocity
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