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1
Morelli, Roberto. "Resistivity testing of concrete." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/15425.
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Gudmarsson, Anders. "Resonance Testing of Asphalt Concrete." Doctoral thesis, KTH, Väg- och banteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155906.
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This thesis present novel non-destructive laboratory test methods to characterize asphalt concrete. The testing is based on frequency response measurements of specimens where resonance frequencies play a key role to derive material properties such as the complex modulus and complex Poisson’s ratio. These material properties are directly related to pavement quality and used in thickness design of pavements. Since conventional cyclic loading is expensive, time consuming and complicated to perform, there has been a growing interest to apply resonance and ultrasonic testing to estimate the material properties of asphalt concrete. Most of these applications have been based on analytical approximations which are limited to characterizing the complex modulus at one frequency per temperature. This is a significant limitation due to the strong frequency dependency of asphalt concrete. In this thesis, numerical methods are applied to develop a methodology based on modal testing of laboratory samples to characterize material properties over a wide frequency and temperature range (i.e. a master curve). The resonance frequency measurements are performed by exciting the specimens using an impact hammer and through a non-contact approach using a speaker. An accelerometer is used to measure the resulting vibration of the specimen. The material properties can be derived from these measurements since resonance frequencies of a solid are a function of the stiffness, mass, dimensions and boundary conditions. The methodology based on modal testing to characterize the material properties has been developed through the work presented in paper I and II, compared to conventional cyclic loading in paper III and IV and used to observe deviations from isotropic linear viscoelastic behavior in paper V. In paper VI, detailed measurements of resonance frequencies have been performed to study the possibility to detect damage and potential healing of asphalt concrete. The resonance testing are performed at low strain levels (~10^-7) which gives a direct link to surface wave testing of pavements in the field. This enables non-destructive quality control of pavements, since the field measurements are performed at approximately the same frequency range and strain level.<br><p>QC 20141117</p>
3
Banthia, Nemkumar P. "Impact resistance of concrete." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26956.
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During its service life, a structure may be subjected to various environmental and loading conditions. However, in general, the properties determined under one set of conditions may not be used to determine the behaviour of the material under a different set of conditions. For example, it is well known that concrete is a strain rate sensitive material; therefore, its properties determined under conventional static loading cannot be used to predict the performance of concrete subjected to high strain rates. The problem is serious because these high strain rate loadings are associated with large amounts of energy imparted to the structure in a very short period of time, and concrete is a brittle material. Since the strain rate sensitivity of concrete prohibits the use of its statically determined properties in assessing its behaviour under dynamic conditions, high strain rate tests are required.
Impact tests were carried out on about 500 concrete beams. An instrumented drop weight impact machine was used. The instrumentation included strain gauges mounted in the striking end of the hammer (called 'the tup'), and also in one of the support anvils. In addition, three accelerometers were mounted along the length of the beam in order to obtain the beam response, and also to enable the inertial correction to the observed tup load to be made. Two different concrete mixes, normal strength with a compressive strength of 42 MPa, and high strength with a compressive strength of 82 MPa, were tested. The effect of two types of fibres, high modulus steel, and low modulus fibrillated polypropylene, in enhancing concrete properties was investigated. In addition, tests were also conducted on beams with conventional reinforcement. Hammer drop heights ranging from 0.15m to 2.30m were used. Static tests were conducted on companion specimens for a direct comparison with the dynamic results.
In general, it was found that concrete is a very stain rate sensitive material. Both the peak bending loads and the fracture energies were higher under dynamic conditions than under static conditions. Fibres, particularly the steel fibres, were found to significantly increase the ductility and the impact resistance of the composite. High strength concrete made with microsilica, in certain circumstances, was found to behave in a far more brittle manner than normal strength concrete.
High speed photography (at 10,000 frames per second) was used to study the propagation of cracks under impact loading. In general, the crack velocities were found to be far lower than the theoretical crack velocities. The presence of reinforcement, either in the form of fibres, or of continuous bars was found to reduce the crack velocity. A model was proposed based on a time step integration technique to evaluate the response of a beam subjected to an external impact pulse. The model was capable of predicting not only the experimentally observed non-linear behaviour of concrete under impact loading, but also the more pronounced brittle behaviour of high strength concrete.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
4
Whitcomb, Richard W. "Quantitative ultrasonic evaluation of concrete." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19004.
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Gudmarsson, Anders. "Laboratory Seismic Testing of Asphalt Concrete." Licentiate thesis, KTH, Väg- och banteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104236.
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Nondestructive laboratory seismic testing to characterize the complex modulus and Poisson’s ratio of asphalt concrete is presented in this thesis. These material properties are directly related to pavement quality and the dynamic Young’s modulus is used in thickness design of pavements. Existing standard laboratory methods to measure the complex modulus are expensive, time consuming, not truly nondestructive and cannot be directly linked to nondestructive field measurements. This link is important to enable future quality control and quality assurance of pavements based on the dynamic modulus.Therefore, there is a need for a more detailed and accurate laboratory test method that is faster, more economic and can increase the understanding and knowledge of the behavior of asphalt concrete. Furthermore, it should be able to be linked to nondestructive field measurements for improved quality control and quality assurance of pavements. Seismic testing can be performed by using ultrasonic measurements, where the speed of sound propagating through a material with known dimensions is measured. Seismic testing can also be used to measure the resonance frequencies of an object. Due to any excitation, a solid resonates when the frequency of the applied force matches the natural frequencies of the object. In this thesis, resonance frequency measurements have been performed at several different temperatures by applying a load impulse to a specimen while measuring its dynamic response. The measured resonance frequencies and the measured frequency response functions have been used to evaluate the complex modulus and Poisson’s ratio of asphalt concrete specimens. Master curves describing the complex modulus as a function of temperature and loading frequency have been determined through these measurements.The proposed seismic method includes measurements that are significantly faster, easier to perform, less expensive and more repeatable than the conventional test methods. However, the material properties are characterized at a higher frequency range compared to the standard laboratory methods, and for lower strain levels (~10-7) compared to the strain levels caused by the traffic in the pavement materials. Importantly, the laboratory seismic test method can be linked together with nondestructive field measurements of pavements due to that the material is subjected to approximately the same loading frequency and strain level in both the field and laboratory measurements. This allows for a future nondestructive quality control and quality assurance of new and old pavement constructions.<br><p>QC 20121120</p>
6
Bukenya, Patrick. "Ambient vibration testing of concrete dams." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10178.
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In this thesis, seven techniques namely; rational fractional polynomial, complex exponential, frequency domain decomposition (FDD) based techniques which include; frequency domain decomposition (FDD), enhanced frequency domain decomposition (EFDD), curve fitting frequency domain decomposition (CFDD) and stochastic subspace identification (SSI) methods namely; unweighted principal component (UPC), principal component (PC) and canonical variant analysis (CVA)) have been applied to data from ambient vibration testing of two concrete dams namely; Roode Elsberg and Kouga dams.
7
Hedlund, Nadja. "Non-Destructive Testing Of Concrete Bridges." Thesis, Luleå tekniska universitet, Byggkonstruktion och brand, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-81923.
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Non-destructive testing is of great value in cases where a structure's future is investigated to find out what the best measure is. It is not always the best solution to demolish and build new. Many structures can be repaired and function several more years. In this thesis the main goal is to investigate some different non-destructive techniques and learn more about difficulties and strengths. The test subjects will be a cast T-beam in a laboratory environment as well as a case study of a railway bridge in Abisko. The different testing equipment being used in this thesis is a covermeter, a rebound hammer and ultrasonic pulse velocity. For both the T-beam and the bridge the results are overall very good. The covermeter is proven to be both easy to use and very reliable and the ultrasonic pulse velocity was more to learn about and more difficult but is giving very good results as well. Conclusions after the thesis project is that it requires a lot of experience of the user and time to make non-destructive testing useful and competitive in the society. Getting all the pieces together it is a powerful tool that hopefully is a sustainable asset in the future, regarding both economic and environmental issues.
8
Mitchell, Andrew Douglass. "Shear friction behavior of high-strength concrete." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19274.
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Blum, Frank. "A focused, two dimensional, air-coupled ultrasonic array for non-contact generation." Thesis, Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04072004-180005/unrestricted/blum%5Ffrank%5F200312%5Fms.pdf.
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Loedolff, Matthys Johannes. "The behaviour of reinforced concrete cantilever columns under lateral impact load." Thesis, Stellenbosch : Stellenbosch University, 1989. http://hdl.handle.net/10019.1/67104.
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Microreproduction of original thesis.<br>Thesis (PhD)--Stellenbosch University, 1990.<br>Some digitised pages may appear illegible due to the condition of the original microfiche copy.<br>ENGLISH ABSTRACT: see item for full text<br>AFRIKAANSE OPSOMMING: sien item vir volteks.
11
Chai, Hsi-Wen. "Design and testing of self-compacting concrete." Thesis, University College London (University of London), 1998. http://discovery.ucl.ac.uk/1317644/.
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Self-compacting concrete (SCC) can flow into place and compact under its own weight into a uniform void free mass even in areas of congested reinforcement. The research reported in this thesis examined the production of SCC with readily available UK materials, with the overall aims of evaluating test methods and establishing a suitable mix design procedure. There have been significant recent developments and applications of SCC in several countries, notably Japan. A literature survey gave an understanding of the advantages and properties of SCC, test methods and the range of constituent materials and their relative proportions for its successful production. A range of SCC mixes can be produced with the common features of a lower aggregate content than conventional concrete and the use of superplasticizers. Most mixes also contained one or more of pulverized fuel ash, ground granulated blast furnace slag and an inert powder filler. A four stage experimental programme was carried out: *tests on pastes to assess the effect of the types and proportions of the powders and superplasticizers on the rheology. *tests on mortars to determine suitable dosage of superplasticizers for high fluidity, low segregation and low loss of workability with time after mixing. Flow spread and funnel tests were used. *tests on fresh concrete to enable suitable types and quantities of coarse aggregate to be combined with these mortars to produce SCC. Fluidity and viscosity were measured using slump flow and V-funnel tests, and passing ability using L- and U-type tests. Two-point workability tests were also carried out, and a novel way of assessing segregation resistance was developed. *tests on hardened concrete to determine compressive strength, bond to reinforcement and drying shrinkage. A mix design procedure, based on a method suggested by Japanese workers, has been developed. This includes optimisation of the mix with a linear optimisation tool from a commercial spreadsheet package.
12
Buchner, Susanne. "Full scale testing of prestressed concrete structures." Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/804425/.
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Mahawish, Ali Hassan. "Axisymmetric compression testing of concrete by nitrogen." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316326.
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Meyer, Karl F. "Transfer and development length of 06-inch diameter prestressing strand in high strength lightweight concrete." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20727.
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Lam, Yuet-kee Jeffery, and 林悦基. "Full-range analysis of reinforced concrete members and frames." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182268.
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Reutlinger, Christopher George. "Direct pull-out capacity and transfer length of 06-inch diameter prestressing strand in high-performance concrete." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19026.
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Chan, Denny Yuk. "Structural integrity assessment of cantilevered type concrete structures by instrumented impact hammer (IIH) technique & ultrasonic pulse velocity (UPV) technique." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174088a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.
18
Lau, Connie K. Y. "Non-destructive evaluation with ultrasonic pulse velocity (UPV) in concrete structure." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174441a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.
19
Mong, Seng Ming. "Non-destructive evaluation with ultrasonic pulse velocity (UPV) in concrete structure." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21175032a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.
20
Haines, Robert Anthony. "Shear Testing of Prestressed High Performance Concrete Bridge Girders." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7120.
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This report details the design and construction of an AASHTO Type IV prestressed girder and a PCI BT-56 prestressed girder. It also details the shear testing and shear performance of the BT-56 girder. The results are compared with results from previous research dating back to 1986. Finally, all research was compared with the AASHTO Standard (2002), AASHTO LRFD (1998) and AASHTO LRFD (2004) Specifications to examine thier overall accuracy in predicting shear strengths.
21
Ng, Ah Book. "Physical models in fire study of concrete structures." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64055.
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Palumbo, Nicolino. "Accelerated corrosion testing of steel reinforcement in concrete." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60681.
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In the last few decades, there has been an increasing worldwide problem of deterioration of reinforced concrete structures, caused primarily by the corrosion of the steel reinforcement embedded within the concrete. Several factors can influence the corrosion process in different types of inservice structures. This thesis reviews the basic principles of the reinforcement corrosion. Various protection and rehabilitation schemes that can be undertaken in the repair of deteriorated concrete structures are presented. In particular, three specific types of structures in the Montreal region which have undergone rehabilitation are presented as typical case studies. Additionally, major research work done in the area of reinforcement corrosion over the last twenty years is reviewed.<br>This thesis reports the results of an experimental research program carried out at McGill University dealing with accelerated electrochemical corrosion testing of reinforced concrete. The main objective of this study is to determine the importance and influence of the depth of the concrete cover thickness on the rate of corrosion of steel reinforcement and thereby, on the resistance of concrete. Appropriate conclusions and recommendations regarding the construction variables affecting the corrosion process are brought forth.<br>These conclusions and recommendations can be summarized.
23
Syropoulou, Stella. "AC Impedance Testing of Surface Treatments on Concrete." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511869.
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Katab, Anwar Othman. "The testing of repair techniques for concrete structures." Thesis, University of Sunderland, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290443.
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Kizito, Nicholas Magera. "Predicting and testing the tensile relaxation of concrete." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/5036.
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Includes abstract.<br>Includes bibliographical references.<br>Tensile relaxation is an important property in structural concrete members such as concrete overlays and patch repairs under sustained imposed restraint. Tensile relaxation helps in reducing tensile stresses in concrete which leads to mitigation of cracking in restrained concrete members. Normally, it is assumed that tensile relaxation is influenced in a similar way by the same parameters that influence creep despite potential differences between the two. Moreover, relaxation is predicted from functions that link it to creep. Whereas it is easy to find published literature on creep of concrete, little can be found on the relaxation behaviour of concrete. More research is therefore needed to understand the factors that influence relaxation and its prediction. This study aimed at comparing the influence of selected factors on creep and relaxation to establish a correlation if any between the two. The parameters investigated include: w/c ratio, age of loading, initial stress-strength ratio and aggregate content. Tensile relaxation tests are difficult to perform and hence prediction models are often relied upon to predict relaxation. Two simplified approximate methods are suggested in the fib Model Code to obtain the relaxation function from the creep function. The Age Adjusted Effective Modulus method (AAEM) given in the MC2010 and the Approximate Relaxation Function (ARF) in MC90-93 are mentioned. Values from the two were compared with experimental relaxation results to verify their accuracy in predicting the relaxation potential of selected concretes. Results show that tensile relaxation of concrete, similar to creep is affected by parameters such as w/c ratio, age of loading and aggregate content. It is observed that the magnitude of tensile relaxation, with other factors held constant, was found to reduce with a reduction in w/c ratio, increase in age and increase in aggregate content. The initial stress-strength ratio does not seem to have a significant influence on relaxation. However, an increase in the initial stress leads to a small and un- proportional increase in relaxation. The use of models linking the creep function and relaxation function to predict low-age relaxation is probably valid. Although both the AAEM and ARF methods yield fairly good predictions of relaxation, the simplicity of the AAEM makes it a better option.
26
Kaděrová, Jana. "Multi-filament yarns testing for textile-reinforced concrete." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2012. http://www.nusl.cz/ntk/nusl-225556.
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The scope of the presented master thesis was the experimental study of multi-filament yarns made of AR-glass and used for textile-reinforced concrete. The behavior under the tensile loading was investigated by laboratory tests. A high number of yarn specimens (over 300) of six different lengths (from 1 cm to 74 cm) was tested to obtain statistically significant data which were subsequently corrected and statistically processed. The numerical model of the multi-filament bundle was studied and applied for prediction of the yarn performance and for later results interpretation. The model of n parallel filaments describes the behavior of a bundle with varying parameters representing different sources of disorder of the response and provides the qualitative information about the influence of their randomization on the overall bundle response. The aim of the carried experiment was to validate the model presumptions and to identify the model parameters to fit the real load-displacement curves. Unfortunately, due to unsuccessful correction of measured displacements devalued by additional non-linear contribution of the unstiff experiment device the load-displacement diagrams were not applicable to model parameters identification. The statistical evaluation was carried only for the maximal load values and the effect of the specimen size (length) on its strength was demonstrated. The size effect curve did not exclude the existence of spatial correlation of material mechanical properties modifying the classical statistical Weibull theory.
27
In, Chi-Won. "Defect characterization in heterogeneous civil materials using ultrasound." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47545.
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Asphalt and Portland cement concrete constitutes a significant portion of the total infrastructure all over the world. It has been reported that much of this concrete infrastructure is now approaching or has already passed its original design life. Thus it is critical to be able to quantitatively assess the condition of these concrete components. In order to rehabilitate or repair the civil infrastructure, nondestructive evaluation (NDE) techniques have been of great interest for infrastructure management agencies. However concrete components present several specific NDE challenges that must be addressed. . Concrete naturally exhibits large scale heterogeneous microstructure with a great deal of local material property variability, For this reasons, many conventional NDE techniques that work well for steel and other homogeneous materials cannot be applied to concrete; concrete is unable to transmit high frequencies, as the heterogeneity of the concrete causes signals of smaller wavelengths or wavelengths equal to the nominal aggregate size to be scattered and severely attenuated. Nevertheless, progress has been made towards accurate and reliable in-place NDE of concrete structures and materials, for example impact echo, ultrasonic pulse velocity method, and the ultrasonic wave transmission method. However, the detection of smaller sized defects or remote defects that are located away from the testing location still pose problems. In addition, the large size and potential limited access conditions of civil structures raise additional challenges. To overcome the limitations of current NDE techniques for concrete, this research considers two different types of ultrasonic waves (coherent and incoherent wave) to quantitatively characterize and monitor defects in heterogeneous concrete materials. The global objective of this research is to determine the feasibility and applicability of using these ultrasonic waves as a global, rapid, reliable, and non-biased technique for the routine screening of defects or monitoring of concrete structures and materials. Three different problems are considered: 1) characterization of segregation in asphaltic concrete, 2) crack depth determination in pier cap of concrete bridge structure, and 3) monitoring of self-healing process in cement-based concrete.
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Kapanpour, Mehrdad. "Superplasticizers in concrete." Thesis, Kansas State University, 1985. http://hdl.handle.net/2097/9856.
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Ng, Yu-ting Ivan, and 吳汝鋌. "Performance and robustness of self-consolidating concrete." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B4088790X.
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Gaber, Ahmed Yaseen 1962. "Pore-water pressure debonding of asphaltic concrete." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277077.
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The report presents an evaluation of a modification to an asphalt-debonding test procedure when used with a water debonding apparatus developed at the University of Arizona, the Pore-Water Pressure Debonding Device. The method being modified is that outlined by Jimenez in his report "Testing for Debonding of Asphalt from Aggregates". A regular test specimen, 4 inches in diameter by 2½ inches high, is water-saturated at 122°F and subjected to repeated pore-water pressure varying from 5 to 30 psi. The above factors are kept constant and the following ones are varied: air void content, stress frequency, stress repetition, stress duration and testing temperature. Test results of the modified testing procedure demonstrated the following trend: the higher the value of any of the aforementioned test variables, i.e., the void content, stress frequency, stress repetition, or stress duration, or any combination of these variables, the greater the loss of the mix resistance to stripping.
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Tso, Karmen, and 曹嘉雯. "Full-range behaviour of concrete beams partially prestressed with unbonded tendons." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38225578.
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Jafar, Ali, and Mohan Maharjan. "Understandability of General Versus Concrete Test Cases." Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4358.
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One possibility to automate more of software testing is to have developers write more general test cases. Given a general (parameterized test case), that holds in many situations, software can generate many different test instances and execute them automatically. Thus, even though the developers write fewer and smaller tests they can test more. However, it is not clear what other effects the use of generalized test cases has. One hypothesis is that “More general test cases are harder to understand than concrete ones and thus would lead to overall tests that are harder to understand”. Software understandability can be defined as the system that is written by one person is easy to read and understand by another person easily without any resistance. However, software understandability is hard to measure because understandability depends on the cognitive behavior of human. Software understandability assists in software reusability and software maintainability.
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Saeed, Yasir Matloob. "Behavior of Prestressed Concrete Beams with CFRP Strands." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2726.
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The high cost of repairing reinforced or prestressed concrete structures due to steel corrosion has driven engineers to look for solutions. Much research has been conducted over the last two decades to evaluate the use of Fiber Reinforced Polymers (FRPs) in concrete structures. Structural engineering researchers have been testing FRP to determine their usability instead of steel for strengthening existing reinforced concrete structures, reinforcing new concrete members, and for prestressed concrete applications. The high strength-to-weight ratio of FRP materials, especially Carbon FRP (CFRP), and their non-corrosive nature are probably the most attractive features of FRPs.
In this study, an experimental program was conducted to investigate the flexural behavior of prestressed concrete beams pre-tensioned with CFRP strands. The bond characteristics were examined by means of experimentally measuring transfer length, flexural bond length, and bond stress profiles. A total of four rectangular beams pre-tensioned with one 0.5-in. diameter CFRP strand were fabricated and tested under cyclic loading for five cycles, followed by a monotonically increasing load until failure. In investigating bond properties, the experimental results were compared to the equations available in the literature.
The results from the four flexural tests showed that the main problem of CFRP strands, in addition to their liner-elastic tensile behavior, was lack of adequate bonding between FRP and concrete. Poor bonding resulted in early failure due to slippage between FRPs and concrete. As a result, a new technique was developed in order to solve the bonding issues and improve the flexural response of CFRP prestressed concrete beams. The new technique involved anchoring the CFRP strands at the ends of the concrete beams using a new "steel tube" anchorage system. It was concluded that the new technique solved the bond problem and improved the flexural capacity by about 46%.
A computer model was created to predict the behavior of prestressed beams pre-tensioned with CFRP. The predicted behavior was compared to the experimental results. Finally, the experimental results were compared to the behavior of prestressed concrete beams pre-tensioned with steel strands as generated by the computer model. The CFRP beams showed higher strength but lower ductility.
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Sasher, William C. "Testing, assessment and FRP strengthening of concrete T-beam bridges in Pennsylvania." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5876.
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Thesis (M.S.)--West Virginia University, 2008.<br>Title from document title page. Document formatted into pages; contains viii, 177 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 130-136).
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Lahlouh, El-hachemi. "Compressive membrane action in concrete silos." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280887.
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Machado, Rafael Ignacio. "Experimental investigation of steel tubed reinforced concrete columns." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19457.
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Lesnicki, Krzysztof Jacek. "Nonlinear resonance methods for assessing ASR susceptibility during concrete prism testing (CPT)." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41054.
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This research focuses on the characterization of damage accumulation in concrete specimens. Specifically, a nonlinear vibration technique is used to characterize the damage introduced by ongoing alkali-silica reactions (ASR). The nonlinear resonance testing consists of an analysis of the frequency response of concrete specimens subjected to impact loading. ASR introduces a third gel like phase, which can be expansive in the presence of moisture. The result of ASR is the formation of microcracks and debonding between aggregate and cement phases. Collectively, these changes act to increase the specimens' nonlinearity. As a result, it is found that the concrete samples exhibit nonlinear behavior; mainly a decrease in resonance frequency with an increasing level of excitation strain. The relationship between the amplitude of the response and the amount of frequency shift is used as a parameter to describe the nonlinearity of the specimen. The specimens used in this research are of varying reactivity with respect to ASR, which is induced in accordance with ASTM C 1293. The level of nonlinearity is used as a measure of damage caused by the progress of ASR throughout the one year test duration. These nonlinear resonance results are compared to the traditional measures of expansion described in the standard. The robustness and repeatability of the proposed technique is also investigated by repeated testing of samples assumed to be at a specific damage state. Finally, a petrographic staining technique is used to complement nonlinearity measurements and to further gain understanding of ASR. The results of this study show that the proposed nonlinear resonance methods are very sensitive to microstructural changes and have great potential for quantitative damage assessment in concrete.
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Hammarström, Elias. "Non-Destructive testing of concrete with ground penetrating radar." Thesis, Luleå tekniska universitet, Byggkonstruktion och brand, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-72621.
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Concrete structures are susceptible to deterioration over time and it is vital to continually assess concrete structures to maintain the structural integrity and prolong the service life. In recent years there has been an increased interest in non-destructive testing of concrete, i.e. assessing the state of the concrete without causing any damage to the structure in the process. There are many different techniques that falls under the term non-destructive testing and one of these that have gained prominence during the last few years is Georadar or ground penetrating radar, often shortened as GPR. GPR is a technique where microwaves are sent into the surface of the concrete by a device, the waves will reflect back to the device when encountering interfaces of areas with different electric properties. The waves are then received by the same device indicating the internal structure of the concrete. This makes the technique an excellent way to find reinforcement bars as the electric properties of concrete and metal strongly differ. In theory though, the technique should also be able to detect other internal differences in concrete, such as voids and corrosion areas but further research is still needed in these areas. This aim of this report is to evaluate ground penetrating radar as a non-destructive technique for assessment of concrete structures. In order to do this different tests has been conducted to evaluate the general performance and usability with a literature review introducing the science behind and what conclusions other researches has reached and using a testing methodology to reach the results. The tests can in a simple way be divided into two parts, first lab tests on a slab in a controlled setting where the internal structure was known, and then two shorter field trips in order to evaluate the performance properly insitu. The results were, to some extent, ambiguous. Although it was found that GPR is an excellent method for finding and locating near-surface reinforcement it was also concluded that the results could vary significantly depending on the location. In one of the field trips the performance of the GPR technique was compared to the performance of traditional cover meter and in this case the portability of the cover meter outperformed the somewhat clunky handling of the GPR. The concrete cover measurement using post-processing of the radar data gave a rough estimate, but once again evaluation still relied on the insitu conditions and the estimate were sometimes questionable. Finding reinforcement below the first layer yielded differing results and it was concluded that further tests were needed to fully evaluate the capabilities of the technique in this regard. The conclusions of the thesis was that although the tests show some potential for the method the results expected from GPR would strongly depend on suitability of the project and experience of the user. One important limiting factor was the availability of devices. For the current project only one specific device was used, it was theorized that another GPR device could get better results depending on the purpose. Furthermore, the lack of experience was also considered to be a limiting factor that might have had an effect on the results. For future research more tests on lower reinforcement and tests on detection of deterioration were suggested. Comparative studies with other similar non-destructive techniques were also considered to be an area of possible interest.
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Li, Yuan. "Standardized physical property testing of self-consolidating concrete (SCC)." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1679681111&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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El-Ali, Mohammad Abdullah 1958. "Effect of variations in compaction on asphaltic concrete." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276662.
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In this report the influence of several variables including asphalt content, mixing temperature, compaction temperature and compaction energy on void content, voids-in-the-mineral-aggregate (VMA), density and stability of asphaltic concrete mixtures was established. Straight lines were obtained on double logarithmic paper for each asphalt content when the logarithm of Marshall stability values as ordinate were plotted versus the logarithm of the corresponding number of blows of a Marshall compactor as the abscissa. The straight lines were very nearly parallel and therefore, it was possible to develop a single empirical formula expressing the relationship between stability at any compactive effort, within the range of 20 to 110 blows per face, in terms of the standard stability at 75 blows per face of specimen. Results indicate that void content, VMA, density and stability were significantly affected by compaction temperature, asphalt content, compactive effort and mixing temperature.
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Kgoboko, Kobamelo. "Collapse behaviour of non-ductile partially prestressed concrete bridge girders." Title page, contents and summary only, 1987. http://web4.library.adelaide.edu.au/theses/09EN/09enk445.pdf.
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Lu, Shan. "Measurable Mictostructural Properties and their Relationship to Chloride Migration and Durability of Concrete." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/Lus2001.pdf.
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Loria-Salazar, Luis Guillermo. "Reflective cracking of flexible pavements literature review, analysis models,and testing methods /." abstract and full text PDF (free order & download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453593.
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Rubin, Ariel. "Strenghtening of reinforced concrete bridge decks with carbon fiber composites." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19320.
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Insel, Emre. "Shear testing of concrete sandwich panels with carbon fiber grid reinforcement." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1313919671&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Azzawi, Mostfa Al. "Investigations on FRP-Concrete Bond." Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7116.
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This dissertation presents findings from three separate investigations, a laboratory study and two field studies that evaluated the durability of the Fiber Reinforced Polymer (FRP)-concrete bond. The laboratory study explored the role of porosity on CFRP-concrete bond following immersion in warm water. Two disparate field studies measured residual bond after 20 years outdoor exposure of FRP repairs of full-size masonry walls and after 12 years for partially submerged piles supporting the Friendship Trail Bridge, Tampa Bay.
The ACI 440 code requires the same surface preparation for all externally bonded FRP concrete repairs. This disregards the role of porosity that is a function of the water / cementitious (w/c) ratio. Concretes with high w/c ratios are low strength concretes, have large voids and a more elaborate capillary pore network compared to low w/c, high strength concretes. Epoxies will therefore penetrate deeper into high porosity concretes. As a result, the performance of low strength, high porosity concrete under moisture exposure can be anticipated to be superior. The laboratory study was intended to determine whether this hypothesis was correct or not.
Three different concrete mixes with water / cementitious ratios of 0.73, 0.44 and 0.25 representing high, medium and low porosities were used for the study. The corresponding target compressive strengths were 2,500 psi, 5,000 psi and 7,500 psi respectively. A total of eighteen, 9 in. x 9 in. x 2.5 in. thick slabs, three for each concrete porosity were tested. Slabs were allowed to cure for over 90 days before surfaces were lightly sand blasted to provide the required concrete surface profile (CSP 3). Specimens were then pre-conditioned in an oven for 48 hours to ensure uniform drying.
Concrete porosity was characterized using mercury porosimetry, SEM, 3D surface scanning and images obtained using a portable microscope. Two commercially available CFRP materials were bonded to the oven-dried prepared slab surfaces and the epoxy allowed to cure at room temperature for 4 weeks. Twelve FRP bonded slabs were completely submerged in potable water at 30 oC (86 oF) as part of the aging program. The six remaining slabs were used for establishing baseline bond values through destructive pull-off tests. The twelve exposed slabs were similarly tested following 15 weeks of exposure.
Results showed minimal degradation in the high porosity, low strength concrete but over 20% reduction in the low porosity, higher strength concrete. Analysis of the failure plane indicated that the lower porosity of the high strength concrete had limited the depth to which the epoxy could penetrate. This was confirmed from magnified images of the bond line taken using a microscope and from a careful assessment of the failure mode. Findings also suggest that the CSP 3 surface profile (light sand blasting) may be adequate for lower strength concrete but not so for higher strength concrete. For applications where FRP concrete repairs of higher strength concrete are permanently or intermittently exposed to moisture, alternative surface preparation may be needed to allow epoxy to penetrate deeper into the concrete substrate. The viscosity of the resin hitherto not considered may be a critical parameter.
In 1995, two full-scale concrete masonry walls were repaired using three horizontally aligned 20 in. (508 mm) wide uni-directional carbon fiber sheets using different commercially available epoxies. Twenty years later the CFRP-CMU bond was determined through selective pull-off tests that were preceded by detailed non-destructive evaluation. Results showed that despite superficial damage to the top epoxy coating and debonding along masonry joints, the residual CFRP-CMU bond was largely unaffected by prolonged exposure to Florida’s harsh environment.
Therein, 99% of samples exhibited in cohesive failure of the CMU or mortar. Pull-off strength was poorer at mortar joints but because the CFRP was well bonded to the masonry surface, its impact on structural performance of the repair was expected to be minimal. Overall, the repairs proved to be durable with both epoxy systems performing well.
The Friendship Trail Bridge linking St. Petersburg to Tampa FL was demolished in 2016. This was the site of three disparate demonstration projects in which 13 corroding reinforced concrete piles were repaired using fiber reinforced polymer (FRP) in 2003-04, 2006, and 2008. The repairs were undertaken using combinations of carbon and glass fiber, pre-preg and wet layup, epoxy and polyurethane resin, and were installed using either shrink wrap or pressure bagging. Residual FRP-concrete bond was evaluated after up to 12 years of exposure through 120 pull-off tests conducted on 10 representative repaired piles. Results showed a wide variation in the measured pull-off strength depending on the type of resin, the number of FRP layers, the prevailing conditions at the time the epoxy was mixed and the method of installation. Epoxy-based systems were found to be sensitive to ambient conditions at installation. Pressure bagging improved performance. The highest residual bond was recorded in pressure bagged piles repaired in 2008. The findings suggest that in marine environments epoxy-based systems installed using pressure bagging can lead to durable repairs.
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Wong, Koon-Wan. "Non-linear behaviour of reinforced concrete frames /." Title page, contents and abstract only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phw872.pdf.
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Xia, Xiahua. "Acoustic resonance spectroscopy (ARS) of concrete components." Thesis, King's College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267620.
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Wissawapaisal, Komwut. "Nondestructive testing of reinforced and prestressed concrete structures using acoustic waveguides." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2049.
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Thesis (Ph. D.)--West Virginia University, 2001.<br>Title from document title page. Document formatted into pages; contains xiv, 204 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 190-195).
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Barrus, Natasha Christine. "Sensitivity of Resistivity Measurements on Concrete Bridge Decks to Operator-Controlled and Concrete Material Variables." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3203.
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The objectives of this research were to investigate the sensitivity of two-prong and fourprong resistivity measurements to certain operator-controlled variables and to conduct a direct comparison of the sensitivity of two-prong and four-prong resistivity measurements to certain concrete material variables. Four full-factorial experiments were designed for this research. In the experimentation on operator-controlled variables with two-prong resistivity testing, main effects that are both statistically significant and practically important include hole depth and surface water. In the experimentation on operator-controlled variables with four-prong resistivity testing, probe position, surface water, and prong spacing are all neither statistically significant nor practically important. This high degree of unexplained variation may be of concern to practitioners. In the experimentation on concrete material variables with two-prong and four-prong resistivity testing, main effects that are both statistically significant and practically important include chloride concentration and temperature, both of which exhibit inverse relationships with resistivity. These research findings support several important recommendations for resistivity testing. Operators of the two-prong resistivity device should use an accurately positioned drill stop to ensure that the prepared holes are consistently the correct depth, and they should expect to obtain different values depending on the presence of surface water on the deck surface. Operators considering use of the four-prong resistivity device should not expect the measurements to be sensitive to probe position with respect to rebar, presence of surface water, or prong spacing for conditions similar to those investigated in this research. Operators interested in monitoring resistivity values over time to ascertain material changes in a bridge deck should develop protocols for measuring concrete temperature in the field and subsequently normalizing resistivity measurements to a standard temperature.