An investigation on the damaging effects of potassium acetate deicer (KAc) on concrete durability was conducted. Different SCM replacement levels were used. ASTM C 1293 and ASTM C 1260 test methods results indicated that KAc is capable of inducing alkali-silica reaction (ASR) expansion in specimens containing reactive aggregate. Class C fly ash was ineffective even at a replacement level of 45%. Class F fly ash and slag were effective in mitigating ASR expansion for specimens exposed to diluted (25% by weight) KAc. KAc showed an increase in pH value upon exposure to concrete specimens. Concrete specimen without SCM and exposed to deicers had higher [K]/[Na] molar ratio near the surface but ions penetrated less compared to specimens containing SCM. ASTM C 666 and MTO LS-412 test methods results showed that air-entrained concrete slabs and prisms without SCM and exposed to KAc are resistant to scaling and freezing and thawing damage.

Increased accident rates during the nighttime and wet weather conditions on the United States highways necessitate the enhancement of highway concrete barrier visibility. The visibility of these delineators is dependent on their reflectivity. Several methods are proposed that stand to increase the reflectivity of these concrete barriers, such as the use of white cement versus gray cement and the attachment of raised pavement markers to the side of the barriers. The incorporation of recycled glass into the concrete mixture is one of the proposed methods that was put through further laboratory study. The aim of the laboratory testing was to identify proper mixing proportions that mitigate the potential for the alkali-silica reaction (ASR) in recycled glass aggregate concretes without producing any negative effects on the compressive strength of the concrete. The retroreflectivity of these concrete mixtures was also evaluated and is presented in this report.

No description available.

This thesis is unique in that it investigated two completely different forms of concrete deterioration: physical sulfate attack and the alkali-silica reaction (ASR). Research was undertaken to better understand physical sulfate attack in order to provide much needed guidance on how to prevent durable this form of deterioration. A testing regime was designed to evaluate and analyze different concrete mixtures with varying water to cementitious material ratios (w/cm), cement types (Type I and V), and use of supplementary cementing materials (SCMs) in accelerated laboratory exposure and outdoor exposure testing. The accelerated laboratory testing evaluated the performance of concrete cylinder segments fully submerged in 30% (by mass of solution) sodium sulfate solution exposed to a temperature and humidity cycle that would promote cycles of alternative conversion between anhydrous sodium sulfate (thenardite) and decahydrate sodium sulfate (mirabilite). In the outdoor exposure site, two different sized concrete cylinders per mixture proportion were partially submerged in 5% (33,000 ppm) sodium sulfate solution and exposed to alternative wetting and drying conditions, along with, temperature fluctuations that would promote conversion between thenardite (Na2SO4) and mirabilite (Na2SO4∙10H2O). With regard to ASR test methods, it has been shown with past research that it is not possible to evaluate “job mixtures” or determine alkali thresholds using ASTM C 1293 (Concrete Prism Test) with evaluating aggregates and concrete mixture proportions for the susceptibility of ASR when testing job mixtures. The most commonly cited issue with the concrete prism test is excessive leaching of alkalis during the course of the test, which may not be a major issue when using the standard, high-alkali concrete mixtures as per ASTM C 1293 but is clearly an issue when testing lower-alkali concrete mixtures. For low-alkali mixtures, alkali leaching can reduce the internal alkali content below the threshold that triggers expansion for a given aggregate. A comprehensive study was initiated that evaluated various modifications to ASTM C 1293, with the intention of developing a testing regime better suited to testing “job mixes” and/or low-alkali concrete mixtures. / text

Recycling composite glass with different colours in order to be manufactured into new glass products is at present not economically viable. Therefore, the search for new issues other than stockpile areas or dumping sites could be a serious opportunity. To a certain extent, one of the possible solutions is to use the recycled glass in manufacturing cements and in the preparation of concrete mixtures. However, it is essential to manage the two main behaviours that the glass can have when used in cement-based materials: (1) the use of glass as coarse aggregates reveals harmful behaviour related to alkali-silica reaction; (2) on the other hand, it can result in useful behaviour related to pozzolanic reaction if used as fine particles. Furthermore, the significant alkali content should not be overlooked as their mass corresponds to about 13% of the total mass of the glass and as they may activate the alkali-silica reaction. An experimental programme was conducted to provide answers to the various questions raised about the use of glass in cement-based materials. The first part of this work was primarily devoted to the evaluation of the reactive potential of glass in mortars (alkali and pozzolanic reactions). At this stage, nine classes of glass particles ranging from 3[mu]m to 2.5 mm were considered. Then, fine glass particles were used in order to counteract the negative effect of some classes of coarse aggregates having revealed alkali-reactive behaviour. The second part of this work was performed to study the mechanisms that could explain the behaviours of fine and coarse particles in aqueous and concentrated environments. Different answers have been proposed to explain the observed behaviour in terms of grain sizes of glass.

Alkali silica reaction (ASR) and delayed ettringite formation (DEF) are two causes of concrete deterioration. Both mechanisms cause expansion of concrete and thus extensive cracking. Most previous research on ASR and DEF focused on understanding the material science of the mechanisms. This dissertation adds to the smaller body of knowledge about ASR/DEF’s effect on the structural behavior of reinforced concrete columns. It compares the structural performance of ASR/DEF affected concrete columns to mechanically cracked columns, evaluates the relative performance of four different concrete repair methods for strengthening damaged columns, and describes how to model pre-existing cracks in the finite element program ATENA. Previous research on scaled columns used mechanically cracked concrete as an approximation of ASR/DEF cracking damage. These earlier column tests, by Kapitan, were compared to two columns affected by ASR/DEF. Due to a deficiency in original design of the actual columns modeled, all of these scaled column specimens failed in bearing during testing under biaxial bending. The ASR/DEF affected columns exhibited nearly identical performance (including bearing capacity) as Kapitan’s control specimen. Thus, with over one percent expansion due to ASR/DEF, there was no reduction in bearing capacity for these columns. Based on the bearing failure observed in these scaled column specimens, concrete repairs were designed to increase confinement of the column capital to address the bearing capacity deficiency. A series of bearing specimens was constructed, externally reinforced using four different strengthening schemes, and load tested. From this bearing specimen series, both an external post-tensioned repair and a concrete jacketing repair performed well beyond their designed capacities and are recommended for bearing zone confinement repair of similar ASR/DEF affected concrete columns. Further, this dissertation presents how Kapitan’s scaled column results were modeled using ATENA (a reinforced concrete finite element program). A technique for modeling the mechanical cracking was developed for ATENA. Once calibrated, a parametric study used the model to find that a 0.17-inch wide through-section crack in the scaled columnd (5/8 inches in the field) was the threshold that reduced capacity of the scaled column to the factored design load. / text

Over the last decade, a number of reinforced concrete bent caps within Houston, Texas have exhibited premature concrete damage (cracking, spalling and a loss of material strength) due to alkali-silica reaction (ASR) and/or delayed ettringite formation (DEF). The alarming nature of the severe surface cracking prompted the Houston District of the Texas Department of Transportation to initiate an investigation into the structural implications of the premature concrete damage. Specifically, an interagency contract with the University of Texas at Austin charged engineers at Ferguson Structural Engineering Laboratory to: 1. Establish the time-dependent relationship between ASR/DEF deterioration and the shear capacity of affected bridge bent caps. 2. Develop practical recommendations for structural evaluation of in-service bridge bent caps affected by ASR and/or DEF. To accomplish these objectives, six large-scale bent cap specimens were fabricated within the laboratory. Four of the specimens (containing reactive concrete exposed to high curing temperatures) represented the most severe circumstances of deterioration found in the field. The remaining two specimens (non-reactive) provided a basis for the comparison of long-term structural performance. All of the specimens were subjected to a conditioning regimen meant to foster the development of realistic ASR/DEF-related damage. Resulting expansions were characterized over the course of the study through a carefully-planned monitoring program. Following a prolonged exposure period, three of the six bent cap specimens (representing undamaged, mild, and moderate levels of deterioration) were tested in shear. Observations made over the course of each test captured the service and ultimate load effects of ASR/DEF-induced deterioration. Six shear-critical spans were tested prior to this publication: three deep beam and three sectional shear tests. The remaining six shear spans (contained within the remaining three specimens) were retained to establish the effects of severe deterioration through future shear testing. Subsequent analysis of the expansion monitoring and shear testing data provided much needed insight into the performance and evaluation of ASR/DEF damaged bent structures. The results ultimately formed a strong technical basis for the preliminary assessment of a damaged bent structure within Houston, Texas. / text

La réaction alcali-silice est une réaction endogène du béton qui peut contribuer à diminuer la durée de vie d'ouvrages coûteux. La modélisation est nécessaire pour pouvoir évaluer la durée de vie restante des ouvrages atteints. L'alcali-réaction provoque un gonflement du béton dû à une fissuration microscopique sous pression de produits de réaction qui sont des gels gonflant par absorption d'eau. Si le béton est chargé, la fissuration microscopique se développe en fonction du chargement local du béton, ce qui induit une anisotropie de comportement et de déformation du béton. L'objectif de notre travail est de simuler, à partir d'hypothèses simples sur les mécanismes réactionnels en jeu, pour une classe de granulats à réactivité rapide, le déroulement de la fissuration du béton au niveau microscopique, de façon à estimer les déformations et les propriétés mécaniques du béton attaqué. Nous utilisons pour cela une description micromécanique du béton qui nous permet de calculer les propriétés mécaniques et les déformations en fonction de l'état de fissuration, et un critère énergétique de fissuration de façon à faire évoluer l'état de fissuration. Le fonctionnement du modèle est testé sur de nombreux cas qui font apparaître que l'utilisation d'un critère de rupture énergétique en micromécanique est bien adaptée à l'alcali-réaction. L'identification des paramètres du modèle sur des essais en laboratoire donne de bons résultats pour des chargements en dessous de 10 MPa, mais conduit à des estimations très élevées des énergies mécaniques. Le modèle a en effet une tendance à surestimer l'anisotropie du gonflement qui est compensée par l'augmentation de l'énergie surfacique de fissuration / The alkali-silica reaction is an endogenous chemical reaction affecting concrete. Therefore, it is important to model the effects of the reaction so as to estimate the life span of the attacked structures. The reaction leads to a microscopic cracking, due to the pressure of the reaction products which swell by absorption of water, inducing swelling of the concrete. If the concrete is mechanically loaded, the orientation of the microscopic cracking is affected by the local stress state, which induces anisotropy of the mechanical properties and deformations of the concrete. Our work aims at simulating, starting from simple assumptions about the reaction mechanisms, and for a class of fast-reacting aggregates, the development of cracking at the microscopic scale, so as to estimate the deformations and mechanical properties of the attacked concrete. In this purpose, we use a micromechanical description of the concrete, thanks to which we can compute the mechanical properties and deformations from the state of cracking of the concrete. In addition to that, we use an energy fracture criterion to determine the evolution of cracking as the attack progresses. We tested our model on numerous cases. These tests show that this description is well adapted to studying alkali-silica reaction. The identification of the parameters using laboratory experiments yielded good results as far as compression stresses are below 10 MPa. However, the fracture energies identified are greater than accepted values for concretes. We think that our model overestimates the anisotropy of the reaction, which is balanced by higher fracture energies in the identification

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.