Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., Highway Bridges, Marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed in order to avoid these high cost repairs. Thus it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements.<p> This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4 potentiostat manufactured by GAMRY INSTRUMENTS. DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution. EIS measurements were applied on samples subjected to incremental chloride additions. Furthermore, carbon steel rebars embedded in concrete samples pre-contaminated with chloride ions added to the mix will be used to relate corrosion rates inside concrete to those obtained from synthetic solutions and to measure moisture content inside concrete using a nondestructive TDR-based technique.

Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., Highway Bridges, Marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed in order to avoid these high cost repairs. Thus it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements.<p> This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4 potentiostat manufactured by GAMRY INSTRUMENTS. DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution. EIS measurements were applied on samples subjected to incremental chloride additions. Furthermore, carbon steel rebars embedded in concrete samples pre-contaminated with chloride ions added to the mix will be used to relate corrosion rates inside concrete to those obtained from synthetic solutions and to measure moisture content inside concrete using a nondestructive TDR-based technique.

<p>  </p> <p>Glass Fiber Reinforced Polymer (GFRP) rebars are frequently used to construct offshore structures, bridges, and airport terminals due to their high tensile strength, lightweight, and non-corrosive nature. GFRP rebars are also non-magnetic, electrically non-conductive, and have a higher strength-to-weight ratio than steel rebars. Consequently, many studies have been conducted to investigate the bond behavior of cast-in GFRP rebars, leading to the formulation of ACI 440. </p> <p>Post-installed rebar technology has become increasingly popular due to its flexibility in retrofitting and extending existing structures. Given the growing demand for post-installed technology and the superior qualities of GFRP rebars, there is a keen interest in understanding the behavior of post-installed GFRP rebars. Post-installed connections involve inserting a rebar in a pre-drilled hole in hardened concrete using an injectable epoxy. The post-installed system allows for construction between existing and new concrete for structural extension and rehabilitation purposes.</p> <p>Currently, only limited work has been performed on post-installed GFRP rebars at relatively small embedment depths. The adhesive mortars used for post-installation generally have a high bond strength. Most of the connections with post-installed rebars are made close to the edges of the members. Due to edge proximity, concrete-related failure modes (concrete splitting) govern, and the high bond strength of the post-installed system is not utilized. </p> <p>This study aims to understand the bond-splitting behavior of GFRP rebars post-installed using epoxy-based adhesive (DeWalt Pure200+). Experimental and Numerical investigations were conducted with various parameters that influence the bond-splitting. These parameters include but are not limited to, concrete cover, embedment depth, concrete strength, rebar diameter, and transverse confinement. </p> <p>An optimal experimental program was designed to test the minimum concrete cover, relative concrete cover, rebar diameter, rebar surface characteristics, and rebar embedment depth. The experimental investigation was carried out in two phases to determine the local bond strength by conducting confined pullout tests away from the edges at shallow embedment depths and the bond-splitting tests at varying parameters. Due to its low transverse strength, a unique grip using a steel pipe grouted with epoxy grout was used for the pullout tests. A new test specimen and test setup were designed to execute the experimental program at deeper embedment depths successfully.</p> <p>Numerical simulations were then performed using the macroscopic space analysis (MASA) program to investigate additional parameters and cases. The numerical models were first validated using results obtained from experimental investigation. Solid tetrahedral elements were used for modeling concrete elements with microplane models to simulate the damage in concrete. GFRP rebars were modeled using solid hexahedral elements with linear elastic material properties. The connection between concrete-to-GFRP rebar was modeled using 2-node bar elements embedded in the contact layer. The bond-slip curve gives the characteristic properties of the bar elements.</p> <p>The influence of individual parameters on the bond strength of the post-installed GFRP rebars was calculated, and comparisons were made with existing bond-splitting models for post-installed steel rebars. This thesis presents the details of the experimental program, the test specimen, the test setup, numerical modeling, and the results obtained on the GFRP bars post-installed with different sets of parameters. The studies prove the feasibility of using GFRP bars as post-installed for structural extensions/retrofitting and highlight certain aspects that must be considered while designing such connections.</p>

M.Tech. (Department of Civil Engineering, Faculty of Engineering and Technology), Vaal University of Technology / This research investigated the structural bond strength of GFRP rebars in concrete beams under dynamic loading with the aim to characterize the structural bond behaviour and evaluate the limitations of the GFRP rebars under dynamic loading. The dynamic loading in this study was set at 500 repeating cycles to simulate a more realistic dynamic loading scenario such as earthquake since most dynamic loading studies are carried under ten repeating cycles. The experimental work was divided into 2 main tests which were firstly, the tensile tests of the GFRP rebars in order to evaluate the tensile strength of the rebars and characterize their properties. Secondly, the flexural tests of GFRP and steel reinforced concrete beams in order to evaluate the bond strength of GFRP and steel rebars, to characterize the average bond strength of GFRP and steel reinforced concrete beams under dynamic loading and finally to compare the average bond strength of GFRP rebars to Steel rebars in both dynamic and static loadings. The tensile tests were carried out using a Universal Testing Machine (UTM) and the results of the tensile tests of the GFRP rebars showed that the average experimental tensile strength of GFRP rebars was only 56.65% of the nominal tensile strength provided on the supplier data sheet. As for flexural tests, they were carried out through a four-point bending test using a UTM in conjunction with a universal dynamic shaker to create the dynamic loading set up. Steel reinforced concrete beams were used as control beams during the tests and factors such as the tensile strength of the GFRP rebars, the slip of the rebars, the load-deflection relationship and the stress-strain relationship were investigated. The results of the tests showed that the tensile strength of the GFRP rebar is strongly proportional to the maximum beam load bearing capacity and the maximum stresses of GFRP reinforced concrete beams. The results also showed that the average bond strength of GFRP rebars in static loading (8.44 MPa) was only 80% of the average bond strength in dynamic loading (10.95 MPa). Moreover, the experimental work showed that the failure of GFRP reinforced concrete beams depicted large deflections (19 mm) and slips (5 mm to 12.5 mm) when compared to steel reinforced concrete beams (for which the maximum deflection was 9.66 mm at failure and slippage values of 2 mm to 10 mm). Based on that it could be stipulated that the tensile strength of GFRP rebars is one determinant factor to the bond strength behaviour of GFRP rebars in concrete. Hence, the structural bond behaviour of GFRP rebars could be well-defined if more studies were done on the bond behaviour of GFRP rebars in concrete beams under dynamic loading using another type of GFRP rebars that would consist of a relatively high tensile strength as compared to the ones used in this study and different surface texture.

Résumé : La technologie des armatures en matériaux composites de polymères renforcés de fibre (PRF) reste relativement récente (moins de 20 ans) et souffre d’une moins bonne réputation en termes de durabilité, ce qui tend à freiner son acceptation par les professionnels du secteur. Les travaux présentés dans ce mémoire ont pour but d’étudier les effets de l’humidité et de l’alcalinité sur les performances mécaniques et thermomécaniques de barres d’armature en PRF. Si de nos jours l’évolution des propriétés des armatures de PRF a été largement étudiée par différents chercheurs, nous n’avons que peu d’informations sur les modes de dégradation qui entrainent ces pertes de performances. Le but des travaux entrepris dans ce mémoire est de trouver des pistes d’investigation pour la compréhension de ces mécanismes de dégradation qui pourraient éventuellement par la suite être reprises dans le cadre de travaux de thèse. Les travaux qui ont été entrepris s’articulent autour de deux projets. Le premier s’intéresse à l’étude du vieillissement accéléré de barres de polymère renforcé de fibres de verre (PRFV) de différents diamètres et soumis à un environnement humide. Le second s’intéresse à l’étude de barres de PRFV et de polymère renforcé de fibres de basalte (PRFB) de même diamètre soumis à un environnement alcalin qui simule le milieu interstitiel du béton. / Abstract : The FRP rebars technology remains relatively recent and suffers from a bad reputation in terms of durability which slows its acceptation among the professionals of the construction field. The aim of the work presented in this essay is to study the effects of moisture and alkalinity on the mechanical and thermo mechanical performances of FRP rebars. Nowadays, the progressions of FRP performances have been widely studied by different researchers but we still have few knowledge about the modes of degradation which lead to performance losses. The final goal of this work is to find investigation trails for the understanding of those degradation mechanisms which could possibly be taken over as part of a thesis work. The work is divided into two projects. The first one is the study of accelerated aging of glass fibers reinforced polymer (GFRP) rebars, of different diameters, conditioned in a moist environment. The second one concerns the behavior of GFRP and basalt fibers reinforced polymer (BFRP) rebars, of same diameter, conditioned in an alkaline environment which simulates the interstitial solution of concrete.

The improvement of construction systems and management systems do not move together in construction industry, not using the effective management approaches decrease the productivity of the work. The firms both in national and international area in manufacturing industry use supply chain management to preserve their competitive force. As material costs account for a high percentage of the overall cost, the success of a project is heavily dependent on material related factors and processes. In Turkey because of extensively using in-situ concrete in construction, the supply chain for reinforcement and concrete is very important. One of the components of concrete is &ldquo / re-bar&rdquo / and its supply chain, rbSC (rebar supply chain) was investigated within the scope of this research. In this study a framework was developed on the basis of the information from a literature survey and a field-test consisting of face-to-face interviews and questionnaire to determine the factors affecting the rbSC externally and those related to the supply chain participants. The developed rbSC performance framework was analyzed with Structural Equation Modeling rules. LISREL software was used, and the outputs of LISREL were evaluated by relationing with the information obtained from literature survey. The developed framework can be used to maximize both effectiveness of the rbSC process and efficiency of time and cost related issues in the rbSC. rbSC performance was associated with the project performance at the end of the study to reach a higher-level scale. The difference between the performance ratings obtained by self-assessment of a participant and those obtained through assessment done by the others was used to determine the affects of cultural issues on performance. Common reasons for the lower performance were analyzed due to cultural context and recommendations were set down for rbSC participants to solve the problems.

<p>Embedded plates are used to support the external attachments such as heavy piping, brackets, sprinkler systems, or other equipment in nuclear power plants. The plates are welded with deformed reinforcing bars or deformed wires and anchored to reinforced concrete walls. The ACI code (ACI 318-19/ACI 349-13) provides design equations to calculate the anchor strength in concrete under tension load. These empirical equations are based on experiments conducted on headed studs, hooked bars, headed bolts, and adhesive anchors. With the lack of experimental data and code provisions on straight deformed reinforcing bars or deformed wires used as anchors, it is believed that anchoring bars with the embedment length as per code prescribed development length will provide sufficient strength to transfer tensile forces to the concrete, ignoring other failure modes such as concrete breakout. </p> <p>In this study, eight large scale group anchor tests were performed to evaluate their concrete breakout strength as per ACI 349-13. The test specimens were made with deformed reinforcing bar anchors (DRAs) and deformed wire anchors (DWAs). The tests included the effect of different bar types, bar sizes, and anchor spacings on the breakout capacities of such connections. The mean average back-calculated effective <i>k </i>value is 33.25 for DRAs and 36.26 for DWAs. The experimental study confirms that the axial tension capacity of embedded plates anchored to concrete using deformed reinforcing bars or deformed wires can be limited by concrete breakout strength.</p>

Das Bauwesen befindet sich in einem ständigen Fortschritt. So war und ist der Stahlbeton der meistverwendetste Baustoff auf der Welt. Jedoch haben sich infolge des stetigen Wandels und Fortschritts der Wissenschaft mittlerweile auch andere Verbundwerkstoffe hervorgetan, die den größten Nachteil, die fehlende Korrosionsbeständigkeit des Stahls, nicht mehr beinhalten. Mit Hilfe von nichtmetallischen Faserverbundwerkstoffen als Bewehrungselemente im Beton ergeben sich folglich dauerhaftere Konstruktionsmöglichkeiten. Jedoch muss das Tragverhalten der neuen Bewehrungselemente aus z. B. Glas- oder Carbonfasern weitreichend untersucht sein, bevor diese effizient und zuverlässig in Bauwerken eingesetzt werden können. Zur Beschreibung des Tragverhaltens der FVK-bewehrten Bauteile ist die Kenntnis über das Verbundverhalten zwischen FVK-Bewehrung und Beton essentiell, um eine Verwendung in der Baubranche finden zu können. Aus diesem Grund wurde im Rahmen dieser Arbeit das Verbundverhalten zwischen verschiedenen Carbonstäben und einem ausgewählten hochfesten Beton weitreichend untersucht, um neue Kenntnisse über die in Deutschland und auch international noch relativ unerforschte Thematik erzielen zu können. Aufbauend auf der Beschreibung des Standes des Wissens zum Verbunverhalten von Stahlbeton, zu FVK-Bauteilen im Allgemeinen und zum Verbundverhalten von FVK-bewehrten Bauteilen, wurden eine Vielzahl an experimentellen Verbundversuchen durchgeführt. Zu Beginn wurden in einer ersten Versuchsserie verschiedene Carbonstäbe mit unterschiedlichen Oberflächenprofilierungen und Herstellungsmethoden im Verbundversuch miteinander verglichen. Im Zuge dessen konnte festgestellt werden, dass die Höhe der übertragbaren Verbundspannungen in starkem Maße von dem Herstellungsverfahren bzw. der Oberflächenprofilierung der Stabvarianten abhängen. Mit Hilfe der Voruntersuchungen konnte die Stabvariante 7 (Carbonstab mit einer Oberflächenprofilierung infolge Fräsung) als Vorzugsvariante für weitergehende Betrachtungen ausgewählt werden. In den anschließenden Kapiteln wurde der zuvor als Referenzstab definierte Carbonstab experimentell umfangreich untersucht sowie erste analytische Modelle vorgeschlagen, um den Einfluss von wesentlichen Parametern auf das Verbundverhalten charakterisieren zu können. Folgende Einflussparameter wurden experimentell erforscht: Betonfestigkeit, Verbundlänge, Carbonstabchargen, Größtkorn/Betonzusammensetzung, Betonierrichtung, Prüfgeschwindigkeit. Zusätzlich erfolgte noch der Vergleich des Verbundverhaltens zwischen dem Carbonstab und einem konventionellem Betonstahl. Die Untersuchungen der verschiedenen Einflussfaktoren zeigten, dass viele Erkenntnisse aus dem Stahlbetonbau auch für den Carbonstab übernommen werden können. Jedoch konnte mit Hilfe der experimentellen Versuche auch gezeigt werden, dass weitere Phänomene auftreten können, die aus dem konventionellen Betonbau nicht bekannt sind. Zusätzlich zu den Auszugversuchen wurde die Spaltneigung des Carbonstabes mit Hilfe von verschiedenen Dehnkörper- und Endverankerungsversuchen in Zusammenhang mit dem hochfesten Beton erforscht. Im Zuge dessen konnte festgestellt werden, dass der Referenzcarbonstab aufgrund des guten Verbundverhaltens zwischen Carbonstab und dem hochfesten Beton bei Probekörpern mit realen Betondeckungen eine zum Teil hohe Spaltneigung aufweist. Durch die Verwendung von verschiedenen Probekörpern mit unterschiedlichen Betondeckungen konnte gezeigt werden, dass der Bewehrungsgrad einen maßgeblichen Einfluss auf die Spaltneigung besitzt. Zum Abschluss der Arbeit wurden ein analytisches Verbundgesetz für den Carbonstab sowie verschiedene Ansätze für die Herleitung eines Bemessungsverbundwertes aufgezeigt. Für die Beschreibung eines Verbundgesetzes wurden die bekannten Ansatzfunktionen aus der Literatur an die experimentellen Ergebnisse angepasst und miteinander verglichen. Dabei stellte sich heraus, dass das aus dem Stahlbeton bekannte Verbundgesetz mit einer geringfügigen Modifikation für den Referenzstab geeignet ist. Somit steht zukünftigen Forschungstätigkeiten ein Verbundgesetz zur Verfügung, welches den gesamten Verlauf der Verbundspannungs-Schlupf-Kurve abbildet. Für die Definition eines möglichen Verbundwertes erfolgte zuerst eine Aufarbeitung der verschiedenen Ansatzfunktion aus dem Stahlbeton sowie weiterer Ansätze aus dem Stand der Technik für FVK-Bauteile. Dabei wurden die jeweiligen Möglichkeiten zur Herleitung eines Verbundwertes für die Berechnung von Carbonbetonbauteilen auf den Referenzcarbonstab übertragen. Im Zuge dessen konnte gezeigt werden, dass zwischen den verschiedenen Ansatzfunktion teils gravierende Abweichungen bestehen, die zu unterschiedlichsten Verbundwerten führen. Ebenfalls konnte nachgewiesen werden, dass einige Ansatzfunktionen die realen Bauteilbedingungen nicht berücksichtigen, wodurch sich unrealistische Verbundwerte ergeben können. Insbesondere die Beachtung der höheren Spaltneigung des Carbonstabes erfolgt in der Regel in den verschiedenen Ansätzen nicht. Jedoch muss die höhere Spaltneigung des Carbonstabes im Beton im Vergleich zu konventionellen Stahlstäben Berücksichtigung finden, um abgesicherte und auf der sicheren Seite liegende Verbundwerte definieren zu können. Aufgrund mit Hilfe von Dehnkörperversuchen aufgezeigten Abhängigkeit zwischen dem Schlupf und der Spaltneigung des Stabes im Beton, kommt der Definition des zulässigen Schlupf- und folglich des Verbundwertes eine im Vergleich zum Stahlbeton noch größere Bedeutung zu.

Este trabalho apresenta estudos, ensaios e análises de resultados a respeito do comportamento à fadiga das estruturas de concreto armadas com barras isoladas e telas soldadas, começando pelas lajes de pontes, seus elementos mais sensíveis à fadiga. A parte experimental desta pesquisa consiste na investigação experimental do comportamento à fadiga de lajes de concreto armado, executadas com e sem pré-lajes armadas com barras de aço isoladas ou em tela soldada. Foram realizados ensaios de fadiga de barra ao ar em 36 corpos de prova de CA50 f10 mm, isoladas e em tela, com o objetivo de construir a Curva de Wöhler dessas barras de produção nacional. Além disso, foram ensaiadas 20 lajes executadas com e sem pré-lajes de concreto, montadas com diversas configurações de armadura, submetidas a ensaios estáticos e dinâmicos. A configuração de armadura adotada nas lajes da pesquisa foi baseada nas utilizadas com freqüência neste tipo de elemento das pontes. A escassez de dados precisos a respeito do comportamento de lajes armadas com barras ou com telas soldadas de fabricação brasileira submetidas a ações cíclicas conduziu ao propósito de se elaborar uma pesquisa de caráter experimental sobre esse tema, cujos resultados e conclusões pudessem fornecer informações mais precisas a respeito do desempenho das lajes. / This research presents the studies, tests and the analysis of the results about the behavior of concrete structures reinforced with rebars or steel mesh due to fatigue loading, starting with bridge slabs which are the most susceptible elements to fatigue. The experimental part of this research consists in testing the behavior due to fatigue of concrete slabs, with or without pre-slabs and reinforced with continuous bars or steel mesh. Axial testing in air of 36 specimens of CA50 f10 mm in continuous bars and mesh were made in order to build the Wöhler Curve for Brazilian conditions. Beyond that, tests were made in 20 concrete slabs with pre-slabs, with several reinforcements arrangement. The 20 slabs were submitted to static and dynamic loading. The reinforcement configuration was based on the commonly used for these elements. The scarcity of more precise data about the behavior of concrete slabs reinforced with rebars or welded mesh made in Brazil submitted to cycle loading was the major reason to make a research based on the testing results about this theme, which results and conclusions are capable of producing more accurate information about the behavior of the slabs.

Este trabalho apresenta estudos, ensaios e análises de resultados a respeito do comportamento à fadiga das estruturas de concreto armadas com barras isoladas e telas soldadas, começando pelas lajes de pontes, seus elementos mais sensíveis à fadiga. A parte experimental desta pesquisa consiste na investigação experimental do comportamento à fadiga de lajes de concreto armado, executadas com e sem pré-lajes armadas com barras de aço isoladas ou em tela soldada. Foram realizados ensaios de fadiga de barra ao ar em 36 corpos de prova de CA50 f10 mm, isoladas e em tela, com o objetivo de construir a Curva de Wöhler dessas barras de produção nacional. Além disso, foram ensaiadas 20 lajes executadas com e sem pré-lajes de concreto, montadas com diversas configurações de armadura, submetidas a ensaios estáticos e dinâmicos. A configuração de armadura adotada nas lajes da pesquisa foi baseada nas utilizadas com freqüência neste tipo de elemento das pontes. A escassez de dados precisos a respeito do comportamento de lajes armadas com barras ou com telas soldadas de fabricação brasileira submetidas a ações cíclicas conduziu ao propósito de se elaborar uma pesquisa de caráter experimental sobre esse tema, cujos resultados e conclusões pudessem fornecer informações mais precisas a respeito do desempenho das lajes. / This research presents the studies, tests and the analysis of the results about the behavior of concrete structures reinforced with rebars or steel mesh due to fatigue loading, starting with bridge slabs which are the most susceptible elements to fatigue. The experimental part of this research consists in testing the behavior due to fatigue of concrete slabs, with or without pre-slabs and reinforced with continuous bars or steel mesh. Axial testing in air of 36 specimens of CA50 f10 mm in continuous bars and mesh were made in order to build the Wöhler Curve for Brazilian conditions. Beyond that, tests were made in 20 concrete slabs with pre-slabs, with several reinforcements arrangement. The 20 slabs were submitted to static and dynamic loading. The reinforcement configuration was based on the commonly used for these elements. The scarcity of more precise data about the behavior of concrete slabs reinforced with rebars or welded mesh made in Brazil submitted to cycle loading was the major reason to make a research based on the testing results about this theme, which results and conclusions are capable of producing more accurate information about the behavior of the slabs.