A combined experimental and analytical program was conducted to investigate the effects of Alkali-Silica Reaction (ASR) and Delayed Ettringite Formation (DEF) on D-regions in reinforced concrete (RC) bridge bents. Four large-scale RC specimens, which represent cantilever and straddle bents in Texas bridges in each specimen, were constructed. The first specimen represented the unexposed control specimen, while the other three were conditioned in the field with supplemental watering to promote ASR/DEF and served as the exposed specimens. The control and two exposed specimens with various levels of ASR/DEF, after eight months and two years of field conditioning, were load tested to failure. The last specimen remains in field with additional exposure to promote ASR/DEF and will be load tested in future studies. The width and length of preload-induced cracks and developing cracks that initiated in the exposed specimens and grew over time, indicating concrete expansion due to ASR/DEF mechanisms, were measured. Petrographic analysis results of concrete cores extracted from the exposed specimens after their load testing confirmed the formation of ASR gel and minimum accumulation of ettringite. The structural testing results showed that the failure mechanism in all three tested specimens was due to a brittle shear failure in the beam-column joint. However, slightly greater stiffness, strength, and ductility were observed in the exposed specimens as a result of the activation of the reinforcing steel in the specimens due to the expansion of the concrete primarily from ASR, which effectively prestressed and confined the core concrete. Sectional analysis and Strut-and-Tie Modeling (STM) of the experimental specimens were applied. Three-dimensional nonlinear Finite Element Analyses (FEA) were also conducted to numerically simulate the overall structural performance, internal response, and out-of-plane behavior of the experimental specimens. The effects of varying constitutive relations of the concrete in tension on models of the specimens were compared with the measured experimental response. A method to mimic ASR/DEF effects on exposed specimens was proposed and incorporated into the FEA approach. As a result, forces that prestress and confine the core concrete were effectively applied through the reinforcing steel prior to subsequent structural loading. The three-dimensional FEA approach was able to simulate the out-of-plane behavior of the beam-column joint and the proposed method yielded comparable results with the measured overall and internal behavior of specimens.

För att bibehålla elnätet stabilt är det viktigt för elproducenterna attkunna möta samhällets behov av elkraft. Detta behov varierar beroendepå tid på dygnet och även av årstid. Att kunna samla energi då behovetär lågt, för att sedan utvinna och distribuera energi då behovet ökar ärdärför viktigt. Vattenkraft är en av de energikällor som är enklast attreglera. Denna energi är dessutom relativt miljövänlig. Att ha en stabiloch säker vattenkraft är därför viktigt för samhället.I detta examensarbete har vissa problem som kan uppstå i ettvattenkraftverkets studerats, närmare bestämt alkali-silikatreaktion ibetong. Denna reaktion framträder genom att betongen sväller. Tillföljd av detta kan konstruktionen spricka. Detta beror på att en gelbildas när alkalier och kisel reagerar med varandra. Denna gel kan taupp vatten och då svälla.En specifik vattenkraftstation har i detta examensarbete studeratsnärmare, nämligen Malgomaj kraftverk. Detta är en anläggning somligger i ett område där, till skillnad från övriga Sverige, det finnsbergarter som har en medelsnabb reaktion med avseende på alkalikiselreaktion.Att denna geografiska placering blir ett problem beror påatt det stenmaterial som finns att tillgå i vattenkraftstationens närhethar använts som ballast i anläggningens betongkonstruktion.I den vattenkraftstation som studeras har problem iakttagits på grundav svällningar av betongkonstruktionen kring turbinen. För att få enuppskattning om hur vattenkraftstationens deformationer i framtidenkommer att utbildas har en modell av problemområdet byggts uppmed hjälp av finita elementmetoden, en så kallad FEM-modell. Dennamodell kalibreras mot mätdata och ska sedan ligga till grund för enuppskattning av vattenkraftstationens livslängd.Resultatet från undersökningen i detta examensarbete visar attdeformationerna är små men betydande för vattenkraftstationensmöjlighet till att fortsätta sin energiproduktion. / To maintain a stable power grid, it is important for electricity producers to meetsociety's need for electricity. This need will vary depending on time of day and eventhe season. Being able to accumulate energy when demand is low, and regain energywhen demand increases, is therefore important. Hydropower is one of the energysources that are easiest to regulate. Having a stable and secure hydropower istherefore important for society.In this thesis one problem that can occur in a hydroelectric plant has been studied,namely alkali-silica reaction (ASR) in concrete. This reaction causes the concrete toswell, due to a formation of gel when alkali and silicon react together.A specific hydropower station has been studied in detail, namely Malgomajhydropower plant. This is a facility that is located in an area where, unlike the rest ofSweden, there are stone materials that have a moderately rapid reaction with respectto the ASR.Problems for this hydroelectric power station have been observed because of swellingof the concrete structure surrounding the turbine. To get an estimate prognosis ofhow the hydropower plant will deform in the future, a finite element method-model(FEM-model) has be created of the problem area. This model is calibrated againstmeasured data and will then form the basis for an appreciation of the hydropowerstation's remaining lifetime.The results in this thesis show that the deformations are small but significant for thehydropower station's opportunity to continue its energy production.

Numerous cases of premature concrete deterioration due to alkali-silica reaction and/or delayed ettringite formation have developed within highway infrastructure in the state of Texas over the past two decades. Although experimental research and in-situ load testing on an international scale has indicated that moderate levels of deterioration are unlikely to pose a threat to structural safety, the discovery of reinforcing bar fracture in Japan due to ASR-related expansion has called into question the integrity of heavily damaged structures. A two-part experimental program was conducted at The University of Texas at Austin relating to ASR/DEF-induced reinforcing bar fracture. Work conducted under TxDOT Project 0-6491 included the fabrication and monitoring of four concrete specimens. Methods were employed to simulate a fracture of the transverse reinforcement within the time frame of the study and the applicability of various NDT monitoring techniques to detect bar fracture was evaluated. Furthermore, a number of reinforcing bar samples were tested and analyzed to investigate (1) the development of reinforcing bar cracking due to the bending operation and (2) the progression of cracks after application of an expansive opening force on bars with 90° bends. Research findings and conclusions form a preliminary assessment on the potential for reinforcing bar fracture within affected infrastructure in Texas. / text

Alkali-silica reaction (ASR) and delayed ettringite formation (DEF) are expansive reactions that can lead to the premature deterioration of concrete structures. Both have been implicated in the deterioration of numerous structures around the world, including many transportation structures in Texas. As a result of considerable research advances, ASR and DEF are now avoidable in new construction, but evaluating and managing the existing stock of structures damaged by these mechanisms remains a challenge. While the published guidance for evaluating structures is very effective at diagnosing the presence of ASR and DEF, there remain significant weaknesses with respect to the evaluation of structural safety and serviceability and nondestructive testing (NDT) is a minor component of the evaluation process. The research described in this dissertation involved a wide range of tests on plain and reinforced concrete at multiple scales. This included small cylinders and prisms, larger plain and reinforced concrete specimens in outdoor exposure, full-scale reinforced concrete beams, and core samples from the outdoor exposure specimens and full-scale reinforced concrete beams. Nondestructive test methods were applied at all scales, and the full-scale beams were also tested in four-point flexure to determine the effects of ASR and DEF on flexural strength and serviceability. Severe expansions from ASR and DEF did not reduce the strength of the full-scale beams or result in excessive deflections under live loads, despite significant decreases in the compressive strength and elastic modulus measured from core samples. Most NDT methods were found to be effective at low expansions but had difficulty correlating to larger expansions. Two promising NDT methods have been identified for future research and development, and guidance regarding existing test methods is offered. / text

The Accelerated Mortar Bar test (AMBT) is rapid, reproducible, and perhaps the most widely used technique for examining the potential alkali-silica reactivity of aggregates. Unfortunately, this test is often unreliable as it may identify non-reactive aggregate as reactive and vice versa. With the aim of improving the accuracy of AMBT, two modifications to the current procedure were evaluated: 1) the maturity of mortar bars prior to alkali hydroxide exposure and 2) reduction of the storage temperature. The original and modified versions were performed on six aggregates with alkali-silica reactive (ASR) components, and their expansions and ASR classifications were compared. Results show that increasing the maturity had no significant impact on expansions. However, modifying the storage temperature to 60˚C and extending the period of testing to 28 days can be very effective in terms of more reliably identifying the existing falsely identified aggregates.

The Accelerated Mortar Bar test (AMBT) is rapid, reproducible, and perhaps the most widely used technique for examining the potential alkali-silica reactivity of aggregates. Unfortunately, this test is often unreliable as it may identify non-reactive aggregate as reactive and vice versa. With the aim of improving the accuracy of AMBT, two modifications to the current procedure were evaluated: 1) the maturity of mortar bars prior to alkali hydroxide exposure and 2) reduction of the storage temperature. The original and modified versions were performed on six aggregates with alkali-silica reactive (ASR) components, and their expansions and ASR classifications were compared. Results show that increasing the maturity had no significant impact on expansions. However, modifying the storage temperature to 60˚C and extending the period of testing to 28 days can be very effective in terms of more reliably identifying the existing falsely identified aggregates.

Les principaux objectifs de cette thèse étaient d'évaluer la formulation et la durabilité des géopolymères à base de métakaolin utilisés comme liants dans des matériaux de construction. Les géopolymères sont des matériaux à activation alcaline faisant l'objet d'études de plus en plus nombreuses de la communauté internationale car ils représentent une alternative aux ciments Portland traditionnels. La première partie de cette étude a donc été dédiée à la formulation de ces matériaux réalisés exclusivement à partir de métakaolin flash et de silicate de sodium et a permis de mettre en évidence des performances comparables à un CEM I 52.5. Une caractérisation physico-chimique ainsi qu'une étude du réseau poreux a souligné les différences entre ces deux matériaux et a permis l'élaboration d'une base de donnée sur les caractéristiques du matériau. La réalisation de béton, allant jusqu'à la fabrication en usine de préfabrication, a montré la capacité des géopolymères à remplacer totalement les liants hydrauliques connus, en terme de mise en œuvre et de performances mécaniques. Les questions de durabilité liées au fort taux d'alcalins dans cette matrice ont été traitées par des études sur la réaction alcali-silice et sur la carbonatation. Les résultats obtenus ont permis de conclure que la réaction alcali-silice ne serait pas préjudiciable dans une matrice de métakaolin activé par du silicate de sodium, et que la réaction très rapide des alcalins de la solution interstitielle des pâtes de géopolymère avec le CO2 atmosphérique ne conduirait pas à une chute de pH significative, préjudiciable dans les matrices cimentaires, mais faciliterait l'apparition d'efflorescences. / The main objectives of this thesis were to assess the formulation and durability of metakaolin-based geopolymers as a binder for civil engineering materials. Geopolymers are alkali-activated materials; they are increasingly studied by the international community as they represent an alternative to traditional Portland cement. The first part of this study has been dedicated to the formulation of these materials, exclusively made from flash metakaolin and sodium silicate, which has shown performances comparable to a CEM I 52.5. A physicochemical characterization and a study of the porous network have highlighted differences between these two materials and allowed developing a database on the characteristics of the material. The achievement of concrete, up to precast plant, showed their ability to completely substitute known hydraulic binders, in terms of workability and compressive strength. Durability issues related to the high alkali content in this matrix were assessed by studies on alkali-silica reaction and carbonation. The results obtained have concluded that the alkali-silica reaction would not be detrimental in a matrix of metakaolin activated by sodium silicate, and that the very rapid reaction of the alkalis in the geopolymer pastes pore solution with atmospheric CO2 do not lead to a significant drop of the concrete pH, which could be detrimental in cement matrix, but could lead to the appearance of efflorescence on the surfaces of geopolymer.

Over the last decades, researchers have proposed a number of tools for the condition assessment of concrete infrastructure affected by alkali-silica reaction (ASR). Amongst those, increasing attention has been given to the Stiffness Damage Test (SDT), Damage Rating Index (DRI), and Residual Expansion (RE) laboratory test procedures that aim to determine the cause and extent (i.e., diagnosis) of damage along with the potential of further deterioration (i.e., prognosis) of affected concrete. Yet, most of the data gathered so far while using the aforementioned tools has been obtained on laboratory test specimens presenting distinct conditions from affected structural members in the field, especially regarding restraint effects. This work aims to understand the impact of restraint on ASR-induced expansion and damage. Thirty-two 450 mm by 450 mm by 675 mm concrete blocks with various reinforcement configurations (i.e., unreinforced, 1D and 2D reinforcement) and incorporating highly reactive coarse and fine aggregates (i.e., Springhill coarse and Texas sand) were manufactured and stored in conditions enabling ASR-induced development (i.e., 38°C and 100 R.H). Two expansion levels were selected for analysis (i.e., 0.08% and 0.15%); once reached, cores were extracted from three different directions (i.e., longitudinal, transversal and vertical) of all blocks and mechanical (i.e., SDT and compressive strength), microscopic (i.e., DRI, scanning electron microscope, etc.) and expansion (i.e., RE) test procedures were conducted on the concrete cores. Results suggest that the presence of restraint influences the induced expansion, resulting in an anisotropic response of the specimens. Furthermore, similar to the expansion behavior, an anisotropic distribution of induced damage and mechanical properties reduction are observed for the restrained concrete blocks in which the restraint configuration seems to significantly affect ASR-induced damage development and features. This led to the observation of a higher number of damage features, ASR development and mechanical properties reduction in cores obtained from unrestrained directions. Yet, some anticipated results from the current research will be studied in detail in the near future where the reliability of the existing techniques (i.e., residual expansion and soluble alkalis) for appraising ASR potential for further induced development and distress (i.e., prognosis) in affected concrete presenting distinct restraint scenarios will be evaluated.

Pressure is mounting in the concrete industry to adopt eco-efficient methods to reduce CO₂ emissions. Portland cement (PC), an essential concrete ingredient, is responsible for over two-thirds of the embodied energy of the concrete, generating about 8% of global greenhouse gas emissions. Extraction and transportation of aggregates and raw materials that comprise concrete mixes are also directly linked to their embodied energy; thus, recycled concrete aggregates (RCA) have been proposed as a promising alternative to increase sustainability in new construction. In this context, many studies have been conducted over the past decades on the properties of RCA concrete. Recent studies have shown that suitable fresh (i.e., flowability) and short-term hardened (i.e., compressive strength) properties might be achieved when the unique microstructural features of RCA are accounted for in the mix-design process of the recycled concrete. However, manufacturing RCA from construction demolition waste (CDW) or returned concrete (RC) presents its unique challenges. Amongst others, the variation in the source of RCA and the presence of damage due to several deterioration mechanisms causes major concern. Due to the presence of reactive aggregates in many quarries in Canada, alkali-silica reaction (ASR) is one of the most common deterioration mechanisms. The durability and long-term performance of RCA concrete are not fully understood and should be further investigated, especially in regards to a) the potential of further (secondary) deterioration of recycled concrete bearing coarse and fine alkali-silica reactive aggregates b) the impact of the severity of the initial reaction on mechanical properties and kinetics of expansion in recycled concrete and c) the impact of using sound and alkali-silica reaction (ASR) affected RCA on the chloride diffusivity (and thus corrosion initiation) of concrete. This work aims to appraise the durability performance of RCA concrete made of 100% coarse RCA, particularly two families of RCA selected (i.e., returned concrete RCA, demolished concrete RCA) to represent waste currently being generated. Furthermore, two types of reactive aggregates are selected to investigate the impact of the source of the reaction (i.e. reactive coarse aggregate as original virgin aggregate - OVA and reactive sand within the residual mortar - RM) within the RCA. ASR is the distress mechanism used to introduce damage to the manufactured RCA. A new mix design technique was used to produce recycled concrete mixtures to increase eco-efficiency, improve fresh-state properties, and reduce cement use in RCA concrete. In conclusion, the initial reaction's location and severity significantly impact the compressive strength, SDT parameters, chloride diffusion rate, and shear strength of concrete specimens. Specifically, the location of the initial reaction can influence the distribution and extension of damage within the various parts of recycled concrete, while the severity of the initial reaction can affect the overall integrity of the aggregates as well as the availability of silica and alkalis for secondary reaction. These results demonstrate the importance of assessing the severity of the initial reaction and its source in order to ensure the durability and long-term performance of recycled concrete made with reactive RCA.

Cette thèse apporte une nouvelle contribution à la caractérisation non destructive des matériaux en béton endommagés par la réaction alcalis-silice (RAS). À cette fin, des techniques et outils de caractérisation non linéaire ont été mises au point. Un banc de test de résonance non linéaire a été développé. Des améliorations ont été apportées au niveau de la chaine d'excitation et au niveau du traitement du signal afin d'optimiser la sensibilité du banc de test. Les essais non linéaires ont été effectues sur sept échantillons de béton endommagés par la RAS, trois échantillons de béton endommagés thermiquement, deux échantillons de béton endommagés mécaniquement et trois échantillons de béton sains. La non-linéarité comportementale des matériaux étant souvent attribuée au comportement hystérétique des micro-défauts contenus dans ces derniers, il a été montré dans un premier temps, que le béton endommagé par la RAS présente un comportement hystérétique. Cette étude a été faite à partir des essais de l'acousto-élastique. Le banc de test de résonance non linéaire a été ensuite utilisé pour la caractérisation des bétons sains et endommagés par la RAS. II a été montré que la technique non linéaire, en plus de permettre une caractérisation sans avoir l'historique de l'état du matériau, permet également de détecter de façon précoce l'endommagement du matériau réactif. L'influence de la teneur en eau sur les paramètres non linéaires a également été étudiée. II a été montré que les valeurs mesurées sur des échantillons de béton conservés dans des conditions de forte teneur en eau sont plus faibles. Dans l'objectif de trouver une particularité à l'endommagement causé par la RAS, la nature visqueuse du gel produit par la RAS a été utilisée. Une démarche, qui s'inspire des essais de fluage en statique réalisés sur des matériaux, a été utilisée pour répondre à cette question de signature de la RAS, tout en appliquant la technique de résonance non linéaire. Le modèle ressort-amortissement de Maxwell a été utilise pour l'interpretation des résultats. Ainsi, le temps de réponse au fluage a été analysé sur des échantillons endommagés par la RAS. II en ressort que le gel issu de la RAS rallonge le temps de réponse au fluage. Enfin, les limites de la technique de résonance non linéaire pour une application in situ ont été expliquées et une nouvelle technique non linéaire estimée applicable sur site a été initiée. Cette technique consiste à utiliser une source externe telle une masse pour provoquer la non-linéarité dans le matériau, pendant qu'une onde ultrasonore sonde le milieu.||The aim of this thesis is to contribute to the non-destructive characterization of concrete materials damaged by alkali-silica reaction (ASR). For this purpose, some nonlinear characterization techniques have been developed, as well as a nonlinear resonance test device. In order to optimize the sensitivity of the test device, the excitation module and signal processing have been improved. The nonlinear tests were conducted on seven samples of concrete damaged by ASR, three samples of concrete damaged by heat, three concrete samples damaged mechanically and three sound concrete samples. Since, nonlinear behaviour of the material is often attribute to its micro-defects hysteretic behaviour, it was shown at first that concrete damaged by ASR exhibits an hysteresis behaviour. To conduct this study, an acoustoelastic test was set, and then nonlinear resonance test device was used for characterizing sound concrete and concrete damaged by ASR. It was shown that the nonlinear technique can be used for characterizing the material without knowing its initial state, and also for detecting early damage in the reactive material. Studies were also carried out on the effect of moisture regarding the nonlinear parameters; they allowed understanding the low values of nonlinear parameters measured on concrete samples that were kept in high moisture conditions. In order to find a specific characteristic of damage caused by ASR, the viscosity of ASR gel was used. An approach, based on static creep analysis, performed on the material, while applying the nonlinear resonance technique. The spring-damping model of Maxwell was used for the interpretation of the results. Then, the creep time was analysed on samples damaged by ASR. It appears that the ASR gel increases the creep time. Finally, the limitations of the nonlinear resonance technique for in situ application have been explained and a new applicable nonlinear technique was initiated. This technique use an external source such as a mass for making non-linearity behaviour in the material, while an ultrasound wave is investigating the medium.