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Alexander M Vaysburd - One of the best experts on this subject based on the ideXlab platform.
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A quantitative approach to the concept of Concrete Repair compatibility
Concrete Repair Rehabilitation and Retrofitting IV, 2015Co-Authors: Benoît Bissonnette, Luc Courard, Andrzej Garbacz, François Modjabi-sangnier, Alexander M VaysburdAbstract:The work reported in this paper is part of a wider research program intended to provide the Repair industry with improved fundamental knowledge to implement rational design methods and rules for Repairs. In that regard, there is a strong need to study the fundamental relationships and parameters that underlie the Repair compatibility concepts, in particular those relating to dimensional compatibility. In the first part of the paper, classical formulas derived for thick cylindrical specimens were used to analyze the tensile stress buildup in annular restrained shrinkage test specimens, taking into account the restraining conditions of the investigated ring test method and the individual Concrete properties/phenomena determined experimentally (elastic modulus, creep coefficient, drying shrinkage deformation). By comparing the ring test results with the calculated tensile stresses, the validity and accuracy of the theoretical approach could be appraised. A quantitative approach for the evaluation of the performance of Concrete Repair in terms of dimensional compatibility was then developed. Derived from the basic strain balance approach (ratio between the total deformability in tension and the drying shrinkage deformation), a parameter referred to as dimensional compatibility index (CI) was introduced in order to analyze the evolution of dimensional compatibility as a function of time for a given Concrete mixture, taking into account the actual degree of restraint in the element. Compatibility index evolution curves were calculated for various Repair Concrete mixtures in order to highlight material behavior relating to composition parameters and temperature. As it requires the evaluation of a limited number of individual properties that are for most readily available (i.e. strength, elastic modulus, shrinkage), the compatibility index expressed in terms of deformation carries a lot of potential as a relatively simple and convenient analytical tool for assessing the cracking sensitivity of Concrete Repair materials. Overall, it can be stated that a good correlation was found between the ring test results and the tensile stress values calculated based on individual Concrete properties / phenomena and that the proposed calculation method lays ground for evaluating quantitatively the dimensional compatibility of Repair materials and defining suitable performance criteria. 1999; Vaysburd et al., 2015). Experimental studies have then confirmed the significant role played by creep in the global dimensional balance and the risk for cracking, especially shrinkage-induced cracking (Morgan, 1996; Pigeon & Bissonnette, 1999; See et al., 2003). One of the most significant findings is that tensile creep appears to be more sensitive than shrinkage to certain mix design parameters (Pigeon & Bissonnette, 1999), which opens up the possibility of designing materials in view of optimizing their creep to shrinkage ratio. Moreover, a correlation between tensile creep and shrinkage was observed, a trend that could be taken advantage of in both calculations and the identification of performance criteria for Repair materials. One of the main challenges to be faced now lies in evaluating quantitatively compatibility and determining what it requires under given circumstances (characteristics of the structure to be Repaired and the environment). So far, even though the concepts have been described in great detail by a number of authors, there are still no reliable criteria or design rules, fundamental or empirical, available to engineers. Some interesting empirical approaches have been suggested, for instance the stress performance margin (Marosszeky, 1992), which consists of an index meant to compare the cracking sensitivity of various Repair materials, or the USACE’s tentative Performance criteria for Repair materials (Emmons et al., 1993), which summarizes the limit values a material should exhibit in selected test procedures for shrinkage and cracking. Those indices and criteria are certainly a step in the right direction, but they lack a fundamental basis, as they do not address explicitly compatibility. Besides, for the compatibility approach to become accessible to the industry, simple and reliable characterization tests are needed. Various test procedures (ring test, beam curling test, box test) have been developed in recent years for the evaluation of the cracking sensitivity of Repair materials (Morency et al., 2005). Some of those so-called performance tests could become key tools for the identification of performance criteria, provided that clear relationships with both the basic material properties and the composite Repair behavior are established. Recently, laboratory and field studies have demonstrated the potential and benefits of different innovative materials or products like shrinkagecompensating Concrete, self-consolidating Concrete, and shrinkage-reducing admixtures. In order to perform successful Repairs with such materials on a consistent basis (optimization and robustness of Repair materials), it is needed to quantify their key compatibility properties and determine what is the sensitivity of those properties to the mixture composition and constituents. 2 OBJECTIVES AND PROPOSED APPROACH The work reported in this paper is part of a wider research program intended to provide the Repair industry with improved fundamental knowledge to implement rational design methods and rules for Repairs. In that regard, there is a strong need to quantify and correlate the relevant aspects of dimensional compatibility in order to consistently achieve Repair works that do not undergo harmful cracking and loss of bond with time. Ultimately, the objective is to provide the industry with performance criteria and guidelines. More specifically, this paper summarizes the work achieved to relate quantitatively the individual dimensional compatibility-related properties (notably elastic properties, creep, drying shrinkage) to the corresponding stress and strain values recorded in an annular restrained shrinkage test, commonly referred to as the ring test. In the first part of the program, classical formulas derived for thick cylindrical specimens were used to analyze the tensile stress buildup in restrained shrinkage test specimens. A quantitative approach for the evaluation of Concrete Repair with a single dimensional compatibility parameter, the compatibility index, was then developed. Compatibility index evolution curves were finally calculated for a range of Repair Concrete mixtures in order to validate the approach and highlight material behavior relating to composition parameters and temperature. 3 MECHANICAL ANALYSIS OF THE RING TEST EXPERIMENT The dimensional balance inside a Repair is governed by the volume changes and mechanical properties of the Repair material, together with the level of restraint provided by the existing structure. Thus, in order to evaluate the restrained shrinkage cracking sensitivity of materials, the analysis must take into account the combined effect of these properties and phenomena. This complex task can be simplified by addressing the evolution of the stress state in a simple restrained-shrinkage element such as that used in ringtype tests (Fig. 1). In this type of experiment, the tested material is cast around a rigid steel ring, which opposes the shrinkage deformations that occurs after setting and curing. The actual level of restraint provided by the steel ring depends on the respective geometrical and material stiffnesses of the two annular bodies (steel and Concrete rings) in contact with each other. The internal stresses that develop in the system are determined by monitoring the deformations in the steel ring with strain gages. Figure 1. Example of ring test specimen (ASTM C1581) to study the restrained-shrinkage behavior of mortar and Concrete
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Condition Evaluation and Durability Planning in Concrete Repair
Concrete international, 2014Co-Authors: Alexander M Vaysburd, Benoît BissonnetteAbstract:Repair methods for Concrete must take into account the changes to Concrete characteristics that occur as part of deterioration. If these changes are considered during Repair, it can help prevent failure and extend service life. Concrete Repair restores an acceptable level of functionality to structures or components that are defective. A deteriorated or distressed structure must be assessed before Repairs can begin. It is necessary to know the cause and level of deterioration to treat it properly. Repair requires a number of steps, from condition evaluation and durability planning, to construction and maintenance. It is necessary to take all steps to ensure that Repairs are effective.
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Concrete Repair bond: evaluation and factors of influence
2014Co-Authors: Benoît Bissonnette, Alexander M Vaysburd, Andrzej Garbacz, Luc Courard, Kurt F. Von FayAbstract:Repair and strengthening of existing Concrete structures are among the biggest challenges civil engineers are facing today and will have to face in the years to come. Present concerns of sustainable development emphasizing Repair instead of new construction will only strengthen this trend. Concerted efforts towards improving the durability of Concrete Repairs are still needed from scientists and engineers. One of the critical aspects of durability of Concrete Repairs and overlays is lasting and sufficient interfacial bond between Repair material and existing Concrete substrate. This paper summarizes some of the findings of a collaborative study devoted to the most significant factors influencing bond in Repairs (roughness, degree of saturation and carbonation of the substrate) and its field evaluation (type of loading, device misalignment). Based on the test results collected in different test programs, guideline-type recommendations for surface preparation prior to Repair were issued. • to evaluate effect of load misalignment upon tensile pull-off test results; • to evaluate the optimum moisture conditioning of a Concrete substrate prior to Repair; and • to evaluate the effect of substrate carbonation upon bond strength.
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Concrete Repair Specifications: Guidance or Confusion
Concrete international, 2011Co-Authors: Robert M. Snover, Alexander M Vaysburd, Benoît BissonnetteAbstract:Sound engineering specifications are an integral part of true Repair sustainability. Although there have been significant advances in understanding the complexity of Concrete Repair and its engineering, premature failure of Repairs has become a real problem. These failures were due to: (1) incorrect diagnosis of the causes of the deterioration; (2) incorrect design of the Repairs; (3) selection of inappropriate Repair materials; and (4) poor workmanship. Writing a Concrete Repair specification is a complex engineering task that requires extensive knowledge of science, engineering, and field practices, as well as high standards of responsibility. The main objective of this article is to help the industry use resources more efficiently and economically. Every means of making Concrete Repair practice, including project specifications, more reliable will have an enormous technical and economic significance, considering the volume of deteriorated Concrete structures and the limited resources for their remediation.
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Concrete Repair: Research and practice – The critical dimension
2008Co-Authors: Alexander M Vaysburd, P.h. Emmons, B. BissonnetteAbstract:Creating a scientifically based Concrete Repair technology is an ultimate goal of the industry at the beginning of the 21st Century. Improved performance of Repaired Concrete structures will depend on whether this objective is achieved or not. It will depend on the willingness and the ability of all partners in the Concrete Repair field to cooperate in developing such a technology. Although significant research advancements have been made with regard to understanding (but not control of) several chemical and physical phenomena responsible for Repair failures, the trend to the “low performance” Concrete Repairs has yet to be reversed. Research is not occupying its time-honored place well ahead of practice, and in some areas of Concrete Repair, it is lagging behind. With special attention to durability of Repaired structures, the paper addresses some of the shortcomings in the scientific input in areas of Repair durability such as condition evaluation methods, key electrochemical factors, service life prediction and performance testing techniques. USA states (Vision 2001): “Slightly more than 50% of the Concrete Repairs performed satisfactorily on the US Army Corp of Engineers Projects.” A similar unsatisfactory situation was found in the UK British. Research Establishment study on Repair Materials Performance (BRE 2006). 215 case histories were studied and only 50% of the Repair projects were successful. Failures Ascribed: − Incorrect diagnosis of the original cause of deterioration − Incorrect design − Selection of inappropriate material − Poor workmanship. In the last two and a half decades, the situation in Repair area changed substantially and everybody places emphasis on durability, but, as less than satisfactory performance data shows, not necessarily using the right approach. One of the important factors contributing to the deterioration of newly Repaired Concrete structures is the service environment and climatic conditions to which the Concrete structure is exposed. But the most critical
P.h. Emmons - One of the best experts on this subject based on the ideXlab platform.
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Concrete Repair: Research and practice – The critical dimension
2008Co-Authors: Alexander M Vaysburd, P.h. Emmons, B. BissonnetteAbstract:Creating a scientifically based Concrete Repair technology is an ultimate goal of the industry at the beginning of the 21st Century. Improved performance of Repaired Concrete structures will depend on whether this objective is achieved or not. It will depend on the willingness and the ability of all partners in the Concrete Repair field to cooperate in developing such a technology. Although significant research advancements have been made with regard to understanding (but not control of) several chemical and physical phenomena responsible for Repair failures, the trend to the “low performance” Concrete Repairs has yet to be reversed. Research is not occupying its time-honored place well ahead of practice, and in some areas of Concrete Repair, it is lagging behind. With special attention to durability of Repaired structures, the paper addresses some of the shortcomings in the scientific input in areas of Repair durability such as condition evaluation methods, key electrochemical factors, service life prediction and performance testing techniques. USA states (Vision 2001): “Slightly more than 50% of the Concrete Repairs performed satisfactorily on the US Army Corp of Engineers Projects.” A similar unsatisfactory situation was found in the UK British. Research Establishment study on Repair Materials Performance (BRE 2006). 215 case histories were studied and only 50% of the Repair projects were successful. Failures Ascribed: − Incorrect diagnosis of the original cause of deterioration − Incorrect design − Selection of inappropriate material − Poor workmanship. In the last two and a half decades, the situation in Repair area changed substantially and everybody places emphasis on durability, but, as less than satisfactory performance data shows, not necessarily using the right approach. One of the important factors contributing to the deterioration of newly Repaired Concrete structures is the service environment and climatic conditions to which the Concrete structure is exposed. But the most critical
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how to make today s Repairs durable for tomorrow corrosion protection in Concrete Repair
Construction and Building Materials, 2000Co-Authors: A.m Vaysburd, P.h. EmmonsAbstract:Abstract The future of the Concrete Repair industry appears to be promising and bright, judging from the projections based on current trends in Repair, rehabilitation, restoration and strengthening of existing infrastructure. However, this optimism must be tempered in light of the need to change the image of the industry as one that is often self-serving — the industry that is Repairing the Repairs. Due to the increasing public concern with durability of Concrete structures in general, and Repaired Concrete structures in particular, the subject of steel corrosion and corrosion protection in Repaired Concrete structures is discussed with reference to the deficiencies in our knowledge of corrosion and corrosion protection in Concrete Repair, methods of testing, and in the science of Repair durability.
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How to make today’s Repairs durable for tomorrow — corrosion protection in Concrete Repair
Construction and Building Materials, 2000Co-Authors: A.m Vaysburd, P.h. EmmonsAbstract:Abstract The future of the Concrete Repair industry appears to be promising and bright, judging from the projections based on current trends in Repair, rehabilitation, restoration and strengthening of existing infrastructure. However, this optimism must be tempered in light of the need to change the image of the industry as one that is often self-serving — the industry that is Repairing the Repairs. Due to the increasing public concern with durability of Concrete structures in general, and Repaired Concrete structures in particular, the subject of steel corrosion and corrosion protection in Repaired Concrete structures is discussed with reference to the deficiencies in our knowledge of corrosion and corrosion protection in Concrete Repair, methods of testing, and in the science of Repair durability.
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Concrete Repair IN THE FUTURE TURN OF THE CENTURY - ANY PROBLEMS?
Concrete international, 1994Co-Authors: P.h. Emmons, A. M. Vayasburd, J. E. McdonaldAbstract:It is noted that when details are correctly designed and specifications are properly prepared and complied with, the Repair process will possess properties that will be serviceable and durable. The paper delineates some of the major issues to consider in achieving long-lasting Concrete Repairs. Comments are made on the current state of Concrete Repair. In order to produce durable Repair with limited and predictable change over time and without deterioration, it is necessary to consider the factors affecting the design and selection of the Repair system, as a whole system. The importance of this systems approach to Repair is emphasized. Factors in such a systems approach to Repair are noted and discussed: compatibility with existing material; dimensional compatibility; chemical and electrochemical compatibility; permeability compatibility; condition of the interfaces; properties of the environment; and workmanship.
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FACTORS AFFECTING THE DURABILITY OF Concrete Repair: THE CONTRACTOR'S VIEWPOINT
Construction and Building Materials, 1994Co-Authors: P.h. Emmons, A.m VaysburdAbstract:Abstract The purpose of this paper is to present the Repair contractor's point of view on the current state of knowledge of Concrete Repair and to present the methodology for the design and production of long-lasting Repair jobs. It is the contractor who has the ultimate responsibility for executing the ‘realcrete’ works and, therefore, for the quality of the final product. Our main desire, along with the research workers, design engineers, material producers, owners and the whole team involved, is to eliminate the undesirable practice of Repairing the Repairs.
Peter H Emmons - One of the best experts on this subject based on the ideXlab platform.
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corrosion inhibitors and other protective systems in Concrete Repair concepts or misconcepts
Cement & Concrete Composites, 2004Co-Authors: Alexander M Vaysburd, Peter H EmmonsAbstract:Abstract In recent times in many parts of the world, reinforcement corrosion has become the main factor in early, premature deterioration, and sometimes failure, of Concrete structures. One of the major factors contributing to this deterioration process is the environmental and climatic conditions to which a Concrete structure is exposed. When the severity of environment is compounded with poor quality Concrete and/or defective design and construction practices, the process of deterioration becomes interactive, cumulative and very rapid, and a cancerous growth that cannot be easily stopped. The poor durability performance of many Concrete structures is causing disruption and expenditure on remedial works which owners and society cannot afford and do not wish to see repeated. A glimpse of reinforcement corrosion and some of the protection options is presented in this paper. The effect of corrosion inhibiting admixtures in Concrete and Concrete Repair is discussed in detail. The complex issue related to the effectiveness of inhibitors in Repairs is addressed, based on analysis of the differences between electrochemical activities in new and Repaired structures. The paper concludes that as long as one continues to blindly use protection methods applicable for newly constructed structures for Concrete Repairs, the business of “Repairing the Repairs” will be on the rise. A broader understanding of the electrochemical differences between new and Repaired Concrete is necessary for effective protection of reinforcement in Repaired structures.
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Concrete Repair technology a revised approach is needed
Concrete international, 2004Co-Authors: Alexander M Vaysburd, Peter H Emmons, James E Mcdonald, N. P. Mailvaganam, Benoît BissonnetteAbstract:This article analyzes some common problems with Concrete Repairs, attempts to provide revised opinions on various Concrete Repair issues and explores issues that need further investigation. Most faults and problems in Concrete Repair can be attributed to lack of attention to condition evaluation, design objectives and details, or poor construction practices. Developing improved performance materials will not help unless the designer and the artisan are skilled at their jobs. It is suggested that improvement in rehabilitation/Repair performance should be approached in two stages. First, design and worker errors should be reduced through improved education and training. In the second stage, improved performance materials should be introduced.
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SELECTING DURABLE Repair MATERIALS: PERFORMANCE CRITERIA--FIELD STUDIES
Concrete international, 2000Co-Authors: Alexander M Vaysburd, Peter H Emmons, James E Mcdonald, Randall W Poston, Keith KesnerAbstract:Concrete Repair is a complex process, with unique challenges that differ from those associated with new Concrete construction. The durability of a Concrete Repair depends, in large measure, on the correct selection and application of Repair materials. Concrete Repair must successfully integrate new materials with existing ones to form a composite system capable of resisting service loads and various environmental factors. The development of and adherence to Repair material performance criteria is a logical way to improve the durability of Repaired structures. The performance of selected commercially available Concrete Repair materials was evaluated in a laboratory investigation. This paper summarizes the results of a concurrent field-exposure study in which the same materials were installed in simulated Repairs and exposed to varying environmental conditions. The research aims were to validate preliminary performance criteria of the field-testing program under realistic conditions; and to study the relationship between field Repairs and test specimen results.
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corrosion protection in Concrete Repair myth and reality
Concrete international, 1997Co-Authors: Peter H Emmons, Alexander M VaysburdAbstract:Deterioration and distress of reinforced Concrete structures in service is a result of a variety of physicochemical processes. These processes include attack by acids or alkalis, cycles of wetting and drying, freezing and thawing, alkali-aggregate reactions, etc. However, among the most serious deterioration processes are those caused by corrosion of reinforcing steel. Corrosion results in the reduction of effective cross-sectional area of the reinforcing bars, and also results in cracking, spalling, and delamination of Concrete cover. The authors would like to reiterate the need for a reliable testing method to evaluate corrosion protection in Repair systems, and to emphasize its urgency. The design of reliable testing procedures for the evaluation of performance of steel reinforcement in new Concrete and in Repair systems should consider such factors as materials, geometry, environment and loading conditions. The type of material stress influences the deteriorative process occurring therein, and should also be considered.
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Performance Criteria for Concrete Repair Materials. Phase 1.
1995Co-Authors: Peter H Emmons, Alexander M VaysburdAbstract:Abstract : The durability of Concrete Repairs depends to a large extent on the proper selection and application of Repair materials. Restrained contraction of Repair materiais, the restraint being provided through bond to the extsting Concrete substrate, is a major factor which significantly increases the complexity of Repair projects as compared to new construction. Preliminary performance criteria for dimensionally compatible Repair materials were developed based on a state-of-the-art review of the literature on cement-based Repair materials. These preliminary criteria are intended for screening and selecting cement-based materials for Concrete surface Repairs. A comprehensive experimental program of laboratory and field tests was developed to verify the performance criteria. (MM)
Benoît Bissonnette - One of the best experts on this subject based on the ideXlab platform.
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UHPFRC for Concrete Repair
MATEC Web of Conferences, 2018Co-Authors: Alexandrine Maltais, Nikola Petrov, Michel Thibault, Benoît BissonnetteAbstract:As part of the St. Lawrence Seaway lock maintenance, the current practice is to perform Concrete Repairs entirely with reinforced Concrete, using either ordinary Concrete or high performance Concrete (HPC) mixtures. However, with the recent advances in the field of ultra-high performance fiber-reinforced Concrete (UHPFRC), the use of this new material is considered in view of improving the overall performance of Repairs. The goal is to implement Repairs capable of dissipating a lot of energy before breaking when a ship hits a Concrete lock wall. Numerous rehabilitation materials and methods have been experimented in the past. They all were unsuccessful due to inadequate shear and impact strength characteristics of the Repair materials used. These needs can be efficiently fulfilled with UHPFRC, with their superior mechanical properties and very high energy-dissipation ability. To analyze the in-situ behavior of UHPFRC, two main mixture designs were investigated: a 160-MPa mixture containing 3% of steel fibers and a 120-MPa mixture containing 3.5% of a steel fiber blend. Thick Repairs with average depths of 700 mm were carried out during the winter shut down period, in very harsh climatic conditions (-12 °C, gusty wind). The performance exhibited by the Repairs after a full year shows that UHPFRCs can withstand very effectively the impacts from the transiting vessels
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A quantitative approach to the concept of Concrete Repair compatibility
Concrete Repair Rehabilitation and Retrofitting IV, 2015Co-Authors: Benoît Bissonnette, Luc Courard, Andrzej Garbacz, François Modjabi-sangnier, Alexander M VaysburdAbstract:The work reported in this paper is part of a wider research program intended to provide the Repair industry with improved fundamental knowledge to implement rational design methods and rules for Repairs. In that regard, there is a strong need to study the fundamental relationships and parameters that underlie the Repair compatibility concepts, in particular those relating to dimensional compatibility. In the first part of the paper, classical formulas derived for thick cylindrical specimens were used to analyze the tensile stress buildup in annular restrained shrinkage test specimens, taking into account the restraining conditions of the investigated ring test method and the individual Concrete properties/phenomena determined experimentally (elastic modulus, creep coefficient, drying shrinkage deformation). By comparing the ring test results with the calculated tensile stresses, the validity and accuracy of the theoretical approach could be appraised. A quantitative approach for the evaluation of the performance of Concrete Repair in terms of dimensional compatibility was then developed. Derived from the basic strain balance approach (ratio between the total deformability in tension and the drying shrinkage deformation), a parameter referred to as dimensional compatibility index (CI) was introduced in order to analyze the evolution of dimensional compatibility as a function of time for a given Concrete mixture, taking into account the actual degree of restraint in the element. Compatibility index evolution curves were calculated for various Repair Concrete mixtures in order to highlight material behavior relating to composition parameters and temperature. As it requires the evaluation of a limited number of individual properties that are for most readily available (i.e. strength, elastic modulus, shrinkage), the compatibility index expressed in terms of deformation carries a lot of potential as a relatively simple and convenient analytical tool for assessing the cracking sensitivity of Concrete Repair materials. Overall, it can be stated that a good correlation was found between the ring test results and the tensile stress values calculated based on individual Concrete properties / phenomena and that the proposed calculation method lays ground for evaluating quantitatively the dimensional compatibility of Repair materials and defining suitable performance criteria. 1999; Vaysburd et al., 2015). Experimental studies have then confirmed the significant role played by creep in the global dimensional balance and the risk for cracking, especially shrinkage-induced cracking (Morgan, 1996; Pigeon & Bissonnette, 1999; See et al., 2003). One of the most significant findings is that tensile creep appears to be more sensitive than shrinkage to certain mix design parameters (Pigeon & Bissonnette, 1999), which opens up the possibility of designing materials in view of optimizing their creep to shrinkage ratio. Moreover, a correlation between tensile creep and shrinkage was observed, a trend that could be taken advantage of in both calculations and the identification of performance criteria for Repair materials. One of the main challenges to be faced now lies in evaluating quantitatively compatibility and determining what it requires under given circumstances (characteristics of the structure to be Repaired and the environment). So far, even though the concepts have been described in great detail by a number of authors, there are still no reliable criteria or design rules, fundamental or empirical, available to engineers. Some interesting empirical approaches have been suggested, for instance the stress performance margin (Marosszeky, 1992), which consists of an index meant to compare the cracking sensitivity of various Repair materials, or the USACE’s tentative Performance criteria for Repair materials (Emmons et al., 1993), which summarizes the limit values a material should exhibit in selected test procedures for shrinkage and cracking. Those indices and criteria are certainly a step in the right direction, but they lack a fundamental basis, as they do not address explicitly compatibility. Besides, for the compatibility approach to become accessible to the industry, simple and reliable characterization tests are needed. Various test procedures (ring test, beam curling test, box test) have been developed in recent years for the evaluation of the cracking sensitivity of Repair materials (Morency et al., 2005). Some of those so-called performance tests could become key tools for the identification of performance criteria, provided that clear relationships with both the basic material properties and the composite Repair behavior are established. Recently, laboratory and field studies have demonstrated the potential and benefits of different innovative materials or products like shrinkagecompensating Concrete, self-consolidating Concrete, and shrinkage-reducing admixtures. In order to perform successful Repairs with such materials on a consistent basis (optimization and robustness of Repair materials), it is needed to quantify their key compatibility properties and determine what is the sensitivity of those properties to the mixture composition and constituents. 2 OBJECTIVES AND PROPOSED APPROACH The work reported in this paper is part of a wider research program intended to provide the Repair industry with improved fundamental knowledge to implement rational design methods and rules for Repairs. In that regard, there is a strong need to quantify and correlate the relevant aspects of dimensional compatibility in order to consistently achieve Repair works that do not undergo harmful cracking and loss of bond with time. Ultimately, the objective is to provide the industry with performance criteria and guidelines. More specifically, this paper summarizes the work achieved to relate quantitatively the individual dimensional compatibility-related properties (notably elastic properties, creep, drying shrinkage) to the corresponding stress and strain values recorded in an annular restrained shrinkage test, commonly referred to as the ring test. In the first part of the program, classical formulas derived for thick cylindrical specimens were used to analyze the tensile stress buildup in restrained shrinkage test specimens. A quantitative approach for the evaluation of Concrete Repair with a single dimensional compatibility parameter, the compatibility index, was then developed. Compatibility index evolution curves were finally calculated for a range of Repair Concrete mixtures in order to validate the approach and highlight material behavior relating to composition parameters and temperature. 3 MECHANICAL ANALYSIS OF THE RING TEST EXPERIMENT The dimensional balance inside a Repair is governed by the volume changes and mechanical properties of the Repair material, together with the level of restraint provided by the existing structure. Thus, in order to evaluate the restrained shrinkage cracking sensitivity of materials, the analysis must take into account the combined effect of these properties and phenomena. This complex task can be simplified by addressing the evolution of the stress state in a simple restrained-shrinkage element such as that used in ringtype tests (Fig. 1). In this type of experiment, the tested material is cast around a rigid steel ring, which opposes the shrinkage deformations that occurs after setting and curing. The actual level of restraint provided by the steel ring depends on the respective geometrical and material stiffnesses of the two annular bodies (steel and Concrete rings) in contact with each other. The internal stresses that develop in the system are determined by monitoring the deformations in the steel ring with strain gages. Figure 1. Example of ring test specimen (ASTM C1581) to study the restrained-shrinkage behavior of mortar and Concrete
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Condition Evaluation and Durability Planning in Concrete Repair
Concrete international, 2014Co-Authors: Alexander M Vaysburd, Benoît BissonnetteAbstract:Repair methods for Concrete must take into account the changes to Concrete characteristics that occur as part of deterioration. If these changes are considered during Repair, it can help prevent failure and extend service life. Concrete Repair restores an acceptable level of functionality to structures or components that are defective. A deteriorated or distressed structure must be assessed before Repairs can begin. It is necessary to know the cause and level of deterioration to treat it properly. Repair requires a number of steps, from condition evaluation and durability planning, to construction and maintenance. It is necessary to take all steps to ensure that Repairs are effective.
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Concrete Repair bond: evaluation and factors of influence
2014Co-Authors: Benoît Bissonnette, Alexander M Vaysburd, Andrzej Garbacz, Luc Courard, Kurt F. Von FayAbstract:Repair and strengthening of existing Concrete structures are among the biggest challenges civil engineers are facing today and will have to face in the years to come. Present concerns of sustainable development emphasizing Repair instead of new construction will only strengthen this trend. Concerted efforts towards improving the durability of Concrete Repairs are still needed from scientists and engineers. One of the critical aspects of durability of Concrete Repairs and overlays is lasting and sufficient interfacial bond between Repair material and existing Concrete substrate. This paper summarizes some of the findings of a collaborative study devoted to the most significant factors influencing bond in Repairs (roughness, degree of saturation and carbonation of the substrate) and its field evaluation (type of loading, device misalignment). Based on the test results collected in different test programs, guideline-type recommendations for surface preparation prior to Repair were issued. • to evaluate effect of load misalignment upon tensile pull-off test results; • to evaluate the optimum moisture conditioning of a Concrete substrate prior to Repair; and • to evaluate the effect of substrate carbonation upon bond strength.
-
Concrete Repair Specifications: Guidance or Confusion
Concrete international, 2011Co-Authors: Robert M. Snover, Alexander M Vaysburd, Benoît BissonnetteAbstract:Sound engineering specifications are an integral part of true Repair sustainability. Although there have been significant advances in understanding the complexity of Concrete Repair and its engineering, premature failure of Repairs has become a real problem. These failures were due to: (1) incorrect diagnosis of the causes of the deterioration; (2) incorrect design of the Repairs; (3) selection of inappropriate Repair materials; and (4) poor workmanship. Writing a Concrete Repair specification is a complex engineering task that requires extensive knowledge of science, engineering, and field practices, as well as high standards of responsibility. The main objective of this article is to help the industry use resources more efficiently and economically. Every means of making Concrete Repair practice, including project specifications, more reliable will have an enormous technical and economic significance, considering the volume of deteriorated Concrete structures and the limited resources for their remediation.
A.m Vaysburd - One of the best experts on this subject based on the ideXlab platform.
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how to make today s Repairs durable for tomorrow corrosion protection in Concrete Repair
Construction and Building Materials, 2000Co-Authors: A.m Vaysburd, P.h. EmmonsAbstract:Abstract The future of the Concrete Repair industry appears to be promising and bright, judging from the projections based on current trends in Repair, rehabilitation, restoration and strengthening of existing infrastructure. However, this optimism must be tempered in light of the need to change the image of the industry as one that is often self-serving — the industry that is Repairing the Repairs. Due to the increasing public concern with durability of Concrete structures in general, and Repaired Concrete structures in particular, the subject of steel corrosion and corrosion protection in Repaired Concrete structures is discussed with reference to the deficiencies in our knowledge of corrosion and corrosion protection in Concrete Repair, methods of testing, and in the science of Repair durability.
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How to make today’s Repairs durable for tomorrow — corrosion protection in Concrete Repair
Construction and Building Materials, 2000Co-Authors: A.m Vaysburd, P.h. EmmonsAbstract:Abstract The future of the Concrete Repair industry appears to be promising and bright, judging from the projections based on current trends in Repair, rehabilitation, restoration and strengthening of existing infrastructure. However, this optimism must be tempered in light of the need to change the image of the industry as one that is often self-serving — the industry that is Repairing the Repairs. Due to the increasing public concern with durability of Concrete structures in general, and Repaired Concrete structures in particular, the subject of steel corrosion and corrosion protection in Repaired Concrete structures is discussed with reference to the deficiencies in our knowledge of corrosion and corrosion protection in Concrete Repair, methods of testing, and in the science of Repair durability.
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FACTORS AFFECTING THE DURABILITY OF Concrete Repair: THE CONTRACTOR'S VIEWPOINT
Construction and Building Materials, 1994Co-Authors: P.h. Emmons, A.m VaysburdAbstract:Abstract The purpose of this paper is to present the Repair contractor's point of view on the current state of knowledge of Concrete Repair and to present the methodology for the design and production of long-lasting Repair jobs. It is the contractor who has the ultimate responsibility for executing the ‘realcrete’ works and, therefore, for the quality of the final product. Our main desire, along with the research workers, design engineers, material producers, owners and the whole team involved, is to eliminate the undesirable practice of Repairing the Repairs.