Adhesion between polymers and concrete / Adhésion entre polymères et béton

The analysis of the quality of the adhesion of an epoxy material to concrete, or other materials, may be defined by the properties and thickness of a transition zone between the bulk adhesive and the pure adherend.Direct measurements of those properties and dimensions are very difficult without a strong interaction between the measurement technique and the obtained results. Mixed numerical experimental methods seems appropriate to obtain valuable information on the transition zone.A defined quality of adhesion on a test specimen can be compared with real adhesion by dynamic test methods.The influence of environmental factors on the quality of the adhesion are also measured on a test specimen and are the basis of a durability analysis of an adhesive joint taking into account classical dimensional analysis.

Polymer coatings on concrete surfaces repeatedly exhibit blisters, cracks or delaminations. Various processes had been proposed to explain the causes of such damage. However, the magnitude of stresses acting on the interface between coating and substrate is relatively unknown. This is particularly true for stresses caused by chemical and physical actions. In a theoretical and experimental research program an attempt is made to quantify such stresses. Two processes causing stresses are described, osmotic pressure and capillary pressure. Two test set-ups were developed to determine the magnitude of such stresses. The results so far show that osmotic processes and capillary suction can result in pressures up to 45 and 2 bar respectively acting on the interface between concrete and coating. But also smaller pressures may cause blisters or delaminations due to stress concentrations at local defects.

The influence of cellulose ether on the strength of mortar and on the anisotropy of concrete are discussed by obtaining relationships between cement-void ratio and compressive strength and by comparing two tensile strengths in the casting direction and direction perpendicular to the casting. — It may be stated that the strength of mortar is little influenced by both cellulose ether and/ or defoamer and the addition of cellulose ether improves bond strength between cement matrix and aggregate by decreasing defect under aggregate due to bleeding.

L’ouvrage a été realisé pour caractériser la propagation d’une fissure dans la zone de contact entre le béton armé de fibres métalliques (le bétonac) et le béton polymère. Les essais ont été faits sur des éprouvettes selon la specification ASTM E 813-81 et des éprouvettes úCB (une poutre double console) avec des fissures artificielles dans la zone de contact des materiaux. Le calcul a été effectué en utilisant la méthode des éléments fini. La technique expérimentale consiste à solliciter 1’éprouvette et à effectuer les mesures des déformations en utilisant l’enregistreur x-y et les mesures photoélastiques.

L’adhérence des solides est un sujet particulièrement interdisciplinaire, où la physique des surfaces, la chimie, la mécanique et la rhéologie sont liées d’une manière qui peut sembler inextricable. Le but de cet article est de donner une vue générale du sujet et d’éclaircir les principaux concepts. On rappelle quelques données de base sur les forces de liaisons, l’énergie superficielle et l’énergie d’adhésion des solides. Il est montré que la force d’adhérence pour séparer deux solides élastiques en contact se calcule par la mécanique de la rupture, et qu’elle dépend non seulement des forces d’adhésion mais aussi de la géométrie, des constantes d’élasticité et de la méthode de mesure. On examine le cas des solides viscoélastiques, pour lesquels la force d’adhérence dépend considérablement de la vitesse et de la température, de sorte qu’un joint collé peut avoir parfois une résistance plus élevée que celle du substrat.

The paper discusses types and conditions of adhesion forces of polymer modified concrete and plain concrete to steel occurring in moulds and in reinforced concretes. Particular attention was paid to hydroxyls -OH, present in the concrete and evoking forces of specific adhesion. The author reports the test results on adhesion and abhesion to steel of the cement and vinyl-maleic modified mortar.

The bonding of concrete to formwork influences the quality of the concrete surface. The theory of bonding is investigated by scientists and is described. The bond strength of the hardened concrete to the surface of the formwork depends on many parameters, from which the most important are the material of the formwork and the parting agents, the roughness of the surface, the type and quality of the concrete, the way and time of compaction and the curing conditions. The bond strength was evaluated — besides many other parameters — for customary formwork materials and new plastic materials.

Polymer concrete composites which are fast replacing conventional materials of construction possess several versatile properties like high strength, early setting time and high resistance to corrosive and erosive actions. However, polymers are temperature sensitive materials and consequently their mechanical properties are largely affected by variations in temperature. At the same time their creep strains also increase several times with the increase in temperature. Therefore, detailed investigations have to be conducted to study the quantum and pattern of variation of not only the important mechanical properties but also of creep of these materials in terms of temperature variation. The data obtained from these investigations will be of immense use for defining the permissible range of temperature to which the materials can be exposed under the operational conditions of the structure in which they are used. It will also help to theoratically predict the extent of creep likely to develop in the material at a given temperature in terms of the corresponding creep at room temperature.

The characteristics of epoxy resin mortars are essential influenced by the adhesion of epoxy resin to aggregates on the basis of quartz. From investigations can be concluded that epoxy resin mortars which are penetrated by chemicals (HCl; NaOH) show a low durability of the adhesion between epoxy resin and quartz and therefore they change their properties very rapidly.

La température exerce une influence marquée sur le comportement des plastiques thermodurcissables et notamment des résines époxydes. Cette influence se répercute sur le choix des méthodes d’essai ainsi que sur la fabrication et le stockage des éprouvettes. Trois méthodes d’essais sont appliquées à des éprouvettes fabriquées respectivement en laboratoire et sur chantier. Les résultats sont comparés statistiquement. Il en ressort que, si les éprouvettes sont fabriquées avec soin, elles donnent des résultats comparables. On propose donc des mesures en vue de réduire la dispersion des résultats. La détermination de la résistance initiale des adhésifs sur le chantier est non seulement essentielle pour la qualité de l’exécution des travaux, mais aussi d’un grand intérêt didactique pour les exécutants.

Dans l’exposé qui suit nous nous intéresserons à l’optimalisation des caractéristiques d’appui des turbogroupes et compresseurs sur leur support génie-civil. Ces appuis participent à la stabilité de la marche de la ligne d’arbre tournant, stabilité qui accroit notablement la sécuritCeilcoteé et la disponibilité des centrales de production d’énergie.

Porous concrete cylinders 15/15 an were made mainly with coarse aggregate, which resulted in a porosity of the specimens of about 40 Vol. %.The specimens were cured according to German standards. After 28 days one half of the specimens was injected in the mould with a epoxide material and the rest with a cenenteous material. Reference specimens were not injected.The compressive strength of the reference specimens was determined prior to injection and the compressive strengths of the injected specimens were determined half an hour, two hours and 28 days after injection. Porosities were determined at the same time using both density measurements and Hg-Porosimetry.

La présente communication met en évidence au moyen d’essais de fluage réalisés en laboratoire et d’analyses chimiques, les problèmes de durabilité des scellements chimiques à base de résines polyesters lorsqu’ils sont réalisés dans le béton en présence d’une humidité permanente.Les essais de fluage à +20°C montrent qu’il se produit un fluage important et évolutif qui conduit à terme à une diminution importante de la résistance à la traction des scellements réalisés dans le béton et conservés en milieu humide. Les essais d’extraction conduisent alors à une rupture par glissement des ancrages.Une étude comparative des variations de la fonction ester sur différents échantillons analysés montre qu’à partir des variations de densité optique et par application des lois de BEER et LAMBERT, on a pu mettre en évidence une forte diminution de la fonction ester sur les scellements conservés en milieu humide, ce qui traduit un phénomène de saponification des résines polyesters.

Quality variations of concrete containing cellulose ether in full-size models of structures relative to the depth and width were examined by strength, absorption and density of cores drilled from the models and pulse velocity and rebound number of each part of the models comparing with conventional concretes. Quality variations of concrete containing cellulose ether in the model structure were smaller than those of conventional concretes. It may be caused by the effect of cellulose ether on controlling segregation of concrete.Otherwise strengths of construction joints in concrete specimens were examined by splitting tests relating addition of cellulose ether. Strengths of construction joints were increased when the old concrete was containing cellulose ether. It may be caused by little laitance because of controlling bleeding.As the results of the experimental investigations it may be stated that the addition of cellulose ether improves heterogeneity characteristics of concrete in structures.

La mise en peinture des ouvrages de génie civil en béton est réalisée soit pour des problèmes d’environnement et d’esthétique, soit pour assurer une protection complémentaire du béton d’un ouvrage ancien venant d’être réparé. Les durées de vie recherchées pour la protection sont de 12 à 15 ans, tant sur les ponts que sur les tunnels. La présente communication traite de l’expérience acquise en France depuis 10 ans pour les systèmes de protection et pour les enduits de ragréages et donne les avantages et les inconvénients des choix réalisés. En particulier les limites de ces revêtements de faible épaisseur sont données avec la protection par peinture de corniches en béton particulièrement gélif et les déboires qui ont suivi.

Concrete slabs of bridges and motorway troughs under tarmac traffic layers are protected against the effects of water and thawing agents by various sealing systems. The results to date have not been sufficiently satisfactory. Modern systems with crack-bridging properties have been formulated paying particular attention to the adhesion between barrier coat and concrete. Adhesion is greatly influenced by water and moisture in the substrate. Rough estimates give an idea of the quantity of water present at the concrete/barrier coat interface. This has to be taken into account when formulating and applying modern non-bituminous systems.

The paper presents the analysies of the state of knowledge on the problem of cracking resistance of anticorrosion coatings made of glass fiber reinforced synthetic resins (mainly polyester and epoxy). This kind of coatings are most often used to protect the concrete substrate in the chemically active environment. The theoretical bases of relation between the coating and concrete substrate properties have been studied. Different models of the relation have been taken into account. The influence of some coating properties (such as thickness, the tensile strength, the modulus of elasticity) on the value of the limit crack width of the concrete substrate have been analysed. The basic features of the coating which determine its cracking resistance have been found. A review of numerous papers has been presented.

Protection effects of polymeric finishes on the carbonation of concrete and corrosion of reinforcement were experimentally examined by using accelerated carbonation testing(30°C, 60%R.H., CO₂; 5% for 8 months) and accelerated corrosion testing(50°C, 95%R.H. for 16 months) for test specimens of reinforced concrete with many kinds of polymeric finishes. In order to evaluate the effectiveness of polymeric finishes as repairing materials for partly-deteriorated reinforced concrete, and also to obtain basic data for improvement of the durability of reinforced concrete by polymeric finishes, experimental data were systematically analyzed by the least-square method using parabolic law(√t law) involving a constant term, which was theoreti-cally derived for the progress of deterioration of reinforced concrete based upon unsteady state dynamic analysis. It was found that polymeric finishes play the important roles in the retardation of carbonation of concrete and the suppresion of corrosion of reinforcement in neutralized concrete with no chloride ions included under ordinary atmospheric environmental conditions.

La présente communication rend compte des résultats des études des revêtements IKAS pour les structures en béton armé. On décrit les copositions et leur propriétés principales, on propose un modèle de calcul des compositions et des paramètres des revêtements anti-corrosion. Des applications pratiques les plus intéressantes sont présentées.

The use of glass fiber reinforced resin coatings for protection of concrete tanks for chemical aggressive industrial liquids depends on whether they are crack-resistant enough. During the work of the tank the width of the cracks can change. The appropriate equipment enabling the research into resin coatings crack-resistance has been built. It allows to test different coatings over changeable widths of cracks in the modelled surface with fixed frequency, number of changes and dimentions of the created chinks.

The paper presents preparation of a low shrinkage polyester mortar coating, its physico-mechanical properties and corrosion resistance in various acid media. The coating is made of polyester resin as binder and hollow micropellets in fly ash as powder material. It features extraordinary low shrinkage approaching zero, and low tensile modulus of elasticity. Applied on the surface of portland cement concrete, it forms a resin mortar coating that is highly adhesive, impermeable, waterproof as well as abrasion-, impact-, weathering- and chemical resistant. It has been successfully used in southen China under intense heat of summer when temperature on the ground is as high as 70–80 c as well as temperature of several degrees below zero. It has been used with success as a isolating for large-sized waste acid reservoirs.

Des informations sont données sur les matériaux et les procédés utilisés actuellement sur les ouvrages EDF pour l’étanchéité des parements amont de barrage ainsi que pour le traitement des fondations et les protections contre l’abrasion des eaux. L’expérience acquise sur quelques revêtements superficiels d’étanchéité permet d’estimer approximativement la pérennité de ces interventions.

The replacement and repair of deteriorated surfaces with gunite is one of the most common operations of facing maintenance for hydraulic works (dams, canals, etc.). However, a certain number of cracking and deteriorated phenomena occurred during these last years, mainly due to temperature and shrinkage problems, to a poor adhesion to the base and, generally, to an objective difficulty of quality control, has lead the Research Center on Hydraulics and Structures (CRIS) of the Italian Electricity Board (ENEL) to study any possible improvement for gunite. For this purpose, the possibility was considered of adding acrylic resins in water dispersion to the gunite, during spraying, and its effectiveness was tested through a series of experimental investigations. Besides a small experimental application on a dam facing, a set of specimens of gunite, with and without resins, was prepared on site, under normal operating conditions. Laboratory tests concerned the following properties: compression and bending strength, adhesion, water absorption, porosity and water permeability. The results obtained do not seem to indicate, however, in the specimens with resins, improvements in the physical-mechanical characteristics such as expected.

Les chaussées en béton hydraulique qui constituent les pistes, voies de circulation pour avions des aéroports d’Orly et de Roissy-Charles de Gaulle finissent, sous le trafic sévère qu’elles subissent, par présenter localement certains désordres. Dans le cadre des travaux d’entretien, les matériaux polymères de type époxydique sont couramment employés depuis une quinzaine d’années en technique de réparation ou, plus récemment, en technique de consolidation de ces chaussées.Ces techniques sont des injections, des réparations de surface, des collages de béton frais sur béton ancien et des scellements de dispositifs de transfert de charge. Leur comportement est pleinement satisfaisant. Le résultat, qui peut être en partie attribué à la sélection attentive des produits employés, reste toujours très dépendant de la qualification de la main d’oeuvre affectée à ces travaux et du soin apporté à leur exécution.

The long-term experience with the formulation of repair mortars for concrete, which are exposed to weather and trafic loads, has shown, that the adhesion of modified cement mortars can be explained as follows: Adhesion of cement mortars, which contain oligomeric additives only, is based on cristalline bonding of the cement paste to the old concrete. This bonding cannot be broken by the exposure to water.Adhesion of polymer cement mortars, formulated with thermoplastic polymer dispersions is based on physical interaction, the chemical adhesion is prohibited by the polymer cover on the cement particles.Adhesion of epoxy-modified cement mortars on old concrete is based on physical interaction too. But in contrary to the thermoplastic polymer dispersions the resistance of the epoxy-resin to saponification can be so high, that the bonding to the old concrete can be water resistant over a long period of time.

When diagnosing a faulty concrete structure, the cause of the fault or deterioration should be established so that the most appropriate solution to the problem can be selected. For example if corrosion of the reinforcement is the main cause of deterioration, then one might call for an impermeable or less permeable repair system which may be found among the resinous system. However one should always bear in mind the compatibility of the system with the old or deteriorated concrete structure.No matter what repair system is chosen one of the requirements of a repair system is the ability to provide an adequate bond between the repair and the old concrete. Ideally the bond strength should be such that the composite structure behaves as monolithial.The factors which in the authors’ view plays an influential role in creation of bond between the repair and old concrete, has been examined in this paper and some comparison is made between the different repair systems.

This paper describes briefly a new type of high molecular material—vinylester 3200 resin mortar, including the characteristics of its formulation, the varieties of performance and its applications in the field. Experiments show that the vinylester 3200 resin mortar has excellent resistance to cavitation-erosion, abrasion-erosion, chemical-corrosion and freeze-thaw cycling, with long-term durability to weathering and soaking in water, good deformability and strong adhesion to the surface of concrete and steel as well as low permeability. It is proved 3200 resin mortar is a new type of abrasion-erosion-resistant material for hydraulic structures and chemical-corrosion resistant material for construction after practical applications.

Le problème des réparations est abordé sous l’angle des critères de qualité auxquels doivent répondre les produits de réparation.Ces critères sont déterminants dans le choix d’une dispersion de polymères utilisés en addition aux mortiers de liants hydrauliques. Les dispersions de copolymères acryliques dont les particules sont de très petite taille, apportent aux mortiers des qualités d’adhérence élevée et une excellente protection contre la carbonatation et la corrosion des armatures en milieu agressif.

La tendance actuelle au sujet de la finition extérieure dans la construction est l’emploi de revêtements monocouches minces en vue d’éviter le décollement dû aux tensions internes. Cette réduction d’épaisseur simplifie les travaux et économise les matériaux. Toutefois, le revêtement épais améliorait la durabilité de la construction, apportait une excellente isolation thermique et protégeait la structure contre les facteurs agressifs. D’autre part, le mortier en monocouche épaisse est très efficace lors de la réparation de décollements,éclatements, écornures et d’autres creux apparaissent sur des surfaces extérieures particulièrement éxposées aux intempéries. Pour cette raison, nous avons élaboré une nouvelle technique de cimentage en monocouche de 10 à 50 mm d’épaisseur grâce à un nouveau mortier de ciment-polymère dont les agrégats principaux sont le sable siliceux, le sable de laitier granulé de haut-fourneau et le sable de microsphères creuses en verre. Nous avons constaté de plus, que pour la monocouche épaisse, la résistance d’adhésion de ce mortier est aussi nettement supérieure par rapport aux mortiers classiques.

Lorsqu’une réparation de surface est effectuée, le béton dégradé est éliminé et remplacé par un mortier de réparation qui se trouve en contact du béton et de l’acier mis à nu.L’étude a consisté à simuler des réparations comportant des aciers en contact en partie avec du ciment (béton durci non dégradé) et en partie avec du polymère ou du liant hydraulique mixte ciment-polymère. Après réparation et durcissement du mortier appliqué, les éprouvettes ont été placées en ambiance agressive, eau potable, eau pure, eau sulfatée, eau de mer, eau magnésienne, avec immersion totale ou semi-immersion alternée, et en atmosphère naturelle.La progression de la corrosion a été contrôlée par: mesures électrochimiquesexamens visuelsdétection des ions agressifs.Les résultats sont les suivants: immersions totales: aucune corrosion des acierssemi-immersion alternées:très forte corrosion des aciers en contact avec le mortier de polymère sans primaireforte corrosion des aciers en contact avec le mortier de polymère avec primairecorrosion nulle pour les aciers en contact avec les mortiers à liant hydraulique mixte quel que soit le milieu agressif, exception faite de l’eau de mer où l’on a noté une oxydation faible des aciers.

The beneficial effect of relatively thin tougher coating on the tensile strength and extensibility of concrete and other quasi-brittle materials was discovered by our ageing short-term static tests and explained by the energy absorption due to the deformation of the coating spanned over a critical crack. Afterwards, this approach was used in U.S.S.R. but another energy condition was considered, namely the improvement of the energy balance due to the debonding. Under this assumption, no improvement of mechanical properties of the brittle core can occur for the cases of the long-term static loading and of the repeated loading because the energy is consumed daring the whole loading process and is then not available at the moment of the sudden final failure. Nevertheless, our recent tests have confirmed our first statement, i.e. that the increase in tensile strength and in extensibility is similar like under short-term static loads. Therefore, the energy absorption due to the deformation of the coating prevails that-one due to the de-bonding. This conclusion is also in accordance with our theoretical results and will be used for the formulation of the new unified Czechoslovak-Soviet recommendation for so-called layered structures.

L’ouvrage présente condensé les suivants aspects: quelques résultats des recherches de laboratoire concernant l’adhérence béton de diverses classes-polymères, l’adhérence béton-béton aux polymères, résultats obtenus aux travaux effectués pour la réparation de divers éléments préfabriqués et monolithes en béton. Les observations sur le comportement en exploitation des éléments préfabriqués et monolithes en béton, réparés, pendant l0–25 années; quelques conclusions pour la prochaine activité.

Concrete bridge decks often show extensive damages caused by wear, de-icing salts and freeze-thaw cycles. The damaged concrete has to be removed and replaced by a new-cast concrete topping.The bonding between old and new concrete has been studied by tests with composite concrete beams. The beams were composed of old concrete with a stripped, rough interface against a new concrete topping.In one investigation composite concrete beams were loaded by a single load at the center of the beam. Both static and fatigue tests were carried out. The results show good bonding in both cases.In a second investigation the effect of differential shrinkage was studied. The composite concrete beams in the tests could resist the residual stresses caused by differential shrinkage without cracks along the rough interfaces or in any of the parts of the beams. The stress relief caused by the creep, which is simultaneous to the shrinkage, is the main cause of the resistance of the concrete beams to residual stresses caused by the differential shrinkage.

La réalisation des constructions en béton présentant une complète continuité est rare dans le bâtiment. Le plus souvent, le bétonnage est interrompu aux endroits déterminés de la construction, et la continuation du bétonnage représente un point potentiellement faible. Un tel point peut être amélioré si le béton déjà durci avant de la continuation du bétonnage est enduit d’une sorte de résine époxyde adéquate. Dans le travail on a présenté les données concernant les recherches expérimentales effectuées au moyen de modèles sous forme de cylindres et de prismes. Les recherches ont porté sur les cas des modèles bétonnés en continuité, ensuite des modèles où la continuation du bétonnage a eu lieu 24 heures ainsi que des modèles, comme dans le cas précédent, où l’on a appliqué l’enduit époxyde à l’endroit de la continuation. Les modèles on été exposés à la traction, au cisaillement et à la flexion jusqu’à la rupture. On a analysé les caractéristiques de la rupture pour les cas particuliers et on a présenté les valeurs et rapports des résistances obtenues.

The permanent forms of polymer impregnated concrete (PIC) panels have been developed to protect prestressed concrete beams from chloride ions.This paper discusses bond property between this form and placed concrete. First, PIC panels with highest bond property were selected with various surface configurations. Second, post-tensioned prestressed concrete beams using these panels were manufactured. The behavior of these beams was studied by an experimental analysis; prestressing, static flexure and dynamic flexure. PIC panels were found to include effective sectional area.

The bond between fresh and hardened concrete can be subjected to various stress states depending on the application and service conditions. Four test methods, reflecting different stress states at the bond between the fresh and hardened concrete, are evaluated. The four methods are a slant shear test, an indirect tension test and two different flexure tests. The slant shear test is shown to be consistent and the most sensitive test in showing the strength of the bond, and was used to evaluate the effect of the following parameters on that strength: (1)the water cement ratio of a portland cement mortar;(2)the thickness of the bond layer;(3)the effect of various curing conditions;(4)the effect of wetting the surface of the hardened concrete before application of the portland cement mortar bonding agent; and(5)the effect of delay between mixing a copolymer Polyvinyl acetate (PVA) bonding agent, and its application to hardened concrete.We conclude that copolymer PVA is a poor bonding agent over a wide range of curing conditions and that the thickness of a portland cement mortar layer has a strong influence on bond strength. The other factors did not affect strength significantly.

L’étanchéité de l’enceinte de confinement des centrales nucléaires PWR du Palier 1300 MW est assurée par une double paroi : interne en béton précontraint et externe en béton armé.Pour obtenir un débit de fuite de l’enceinte interne inférieur au debit spécifié en cas d’accident, les dispositions suivantes sont réalisées: confection et mise en oeuvre d’un béton étanche à l’airtraitement des discontinuités telles que reprises, fissures, traversées des fourreaux, par l’injection de produits appropriés.Ce sont, en effet, ces discontinuités qui sont généralement le siège des fuites.La sélection des produits d’injection doit tenir compte des particularités de ces fuites: les études ont porté entre autres sur: l’évolution de la viscosité, en fonction du tempsle pouvoir mouillant des produitsles caractéristiques mécaniques (résistance à la traction, dureté Shore A) des résines.C’est ainsi qu’une gamme importante de produits a été examinée, surtout en fonction de leurs possibilités d’emploi sur chantier.En parallèle, ont été menés des essais d’application in situ, afin de vérifier le comportement des produits sélectionnés.Nous disposons après cette étude, de deux types de solutions pour le traitement des singularités de bétonnage: des résines époxydiques super-fluidifiéesdes silicates de soude de diverses provenances.

L’étude de l’influence de l’eau sur la réticulation isotherme de quelques liants époxydiques utilisés en réparation par injection a permis de mettre en évidence les points suivants: la miscibilité initiale des systèmes d’époxydes avec l’eau dépend de la nature chimique des durcisseurs et de la teneur en diluant réactif du mélange;l’étude des cinétiques de réticulation isotherme montre que la température agit non seulement sur la vitesse de réticulation, mais également sur le taux de réticulation. La cinétique de réticulation isotherme en masse suit une loi de type Arrhénius;l’étude des cinétiques de retrait volumique isotherme a permis d’évaluer leur miscibilité finale avec l’eau et la modification de leur vitesse de réaction;la variation du module élastique en compression est abaissée de 16 % pour le système le moins miscible à l’eau à 70 % pour le plus miscible pour une teneur en eau de 6 %.

Lorsque se présente un cas d’injection de béton fissuré ou microporeux, on pense instantanément «époxyde». Or un époxyde, du fait de sa viscosité élevée, n’est pas forcément le produit idéal pour injecter un massif peu perméable. A titre d’exemple nous verrons dans ce texte comment on peut étendre le domaine d’utilisation des époxydes (par fluidification et par allongement du temps de polymérisation) et quels autres types de résines, plus fluides, peuvent être envisagés.

Cracked building elements are increasingly being repaired by the injection of reactive resins. The success of a repair not only depends on the choice of the right injection material but rather it is also influenced in a complex way by many practical construction conditions. This includes the non-positive injection of wet crack surfaces. At present very little information is available about the influence of processing and material-related parameters on the bond behaviour. The cause of premature bond failure must be sought in the microregions of the adhesive areas, wherefore the application of scanning electron microscopy is indispensable. The influence of different boundary conditions on the bond behaviour of the injected resin systems was investigated in several tests. In the first test unit with building elements, it could be shown that dry crack injection at a temperature generelly presents little difficulty. The investigation of 25 °C carbonated injected crack surfaces also presented positive results. However, the presence of water during the injection and the curing phase resulted in a reduction in the bond tensile strength. In cooperation with the chemical industry, the adhesive properties of some wet injected resins have been improved considerably.

On peut restituer une grande partie du monolithisme d’une structure en injectant dans les fissures un liant polymère adéquat. Seulement le matériau utilisé pour la réparation possède des propriétés physico-mécaniques tout à fait distinctes du béton. Sous l’effet des sollicitations extérieures couplées à la température on assiste à l’apparition d’autocontraintes dans les fissures.La présente recherche concerne l’étude de l’influence des variations de la température sur la stabilité de la réparation par injection d’une structure fissurée.Dans ce but on a étudié la rupture d’éprouvettes de béton 10 × 10 × 40 cm, fissurées artificiellement et injectées, après qu’elles aient subi des cycles à basse température (+ 20° C, −15° C) et des cycles à température élevée proche de celle rencontrée dans les ouvrages tunisiens (+ 20° C, + 60° C).Les premiers résultats montrent qu’il n’y a pas d’influence notable des cycles froids, sur l’adhérence du polymère injecté. Par contre le passage de 20° à 60° C montre qu’au bout de deux cycles, l’adhérence de la résine epoxyde au béton est modifié de telle sorte que la rupture devient du type adhésif au lieu d’avoir lieu dans le béton, comme dans le cas des éprouvettes conservées à 20°C.Des essais de traction directe, effectués à différentes températures, comprises dans la plage 20° C à 60° C, sur des éprouvettes de résines époxydes durcies, ont montré un comportement de ces matériaux variable avec la température.

Simple analytical models are presented which are used to examine the theoretical behaviour of an axially reinforced concrete prism under tension pre and post-repair by resin injection. The effect of repair on the steel strain at the crack and the crack movement has been derived in terms of the resin modulus and the original crack width. The load sustained post-repair before recracking has been shown to be dependent upon the load at which repair is carried out and on the previous load history of the member. The experimental work was conducted using axially reinforced concrete prisms loaded in tension and monitored for strain. Plain and ribbed reinforcements were used. A novel part of the test program was that the repair and resin curing period of some members was undertaken while they were held under load, rather than at zero load. Most members tested were able to support, following repair, substantial proportions of the original cracking load before recracking occurred, although for ribbed bars, the post-repair load increment is sensitive to the success in repairing secondary cracking.

Cracks in concrete usually have to be closed either to make the structure water tight again or to protect the reinforcement against corrosion. As many cracks are not stable in their width, a repair is only successful, when the injected material can change its volume according to the volume-change of the crack. The volume of gases can be changed to a great amount by applying small external forces. To achieve volume compressibility of.an injecting resin combined with watertightness, plastic micro-balloons or micro-spheres (average diameter 0,04 mm) are inserted into the resin. Using a rubberlike epoxy resin, volume deformations of more than 50% are possible. If the epoxy resin is stiff (modulus of elasticity about 2000 N/mm2) forces can be transmitted still allowing a volume change of 10 to 20%. The applied deformations are fully reversible.

High molecular weight methacrylate (HMWM) is a relatively new monomer that has many of the advantages of methyl methacrylate (MMA), namely low viscosity, potential for curing over a wide range of temperatures and good wetting characteristics. However, the HMWM has low odor and a high flash point which are signigicant improvements over MMA.HMWM has been used to produce polymer concrete for overlays and other specialty applications. It has very good mechanical and durability properties, and bonds very well to portland cement concrete.One of its most important uses, however, is to seal cracks and restore structural integrity of portland cement concrete. Due to its excellent wetting characteristics, it penetrates even very fine cracks. It has been used for a wide range of crack repair applications in the United States, particularly for bridges.

By means of suitable synthetic resin adhesives, storey-high slabs of reinforced autoclaved aerated concrete (AAC) can be joined to form transportable room size wall units within very short time. By means of the adhesive joints, the slabs are combined to form monolithic wall panels, which can be transported to the building site as soon as about 30 minutes after the glueing. Tests have been made with adhesives based on epoxide resins, polyurethane and polyester resins. All three kinds can be used in principle and the polyester adhesive has proved to cure faster than the others. The adhesives may also be used to glue AAC to reinforced normal-weight concrete and to steel. This permits lintels made of reinforced normal-weight concrete to be glued into the units over window and door openings. The safety in handling is improved in that steel rods extending horizontally at right angles through the surfaces defining the joints are fixed by nuts to the units. Said steel rods are intended only to prevent a fracture of the units in case of unforeseen shocks and of a possible failure of the adhesive joints as the units are handled and installed in the site.

In order to be able to predict the durability of adhesive-bonded (glued) joints made in concrete construction using epoxy resin adhesives, it is necessary to know the change undergone in the adhesion term under a variety of conditions. The first part of the present work thus deals with investigations of the performance and sustained load strength of adhesive-bonded joints under damp conditions and of the sustained load strength at increased temperatures, which were carried out by the author over a period of several years. On the basis of these results and of the results of investigations carried out by other authors a series of simple dimensioning equations are provided, taking the strength of the concrete into consideration. In addition to this, simple tests are suggested with which the suitability of epoxy resin mortars for adhesive-bonded joints in concrete construction can be checked.

Lors de l’assemblage par collage desvoussoirs préfabriqués dans les ponts en béton précontraint, la résine époxydique subit pendant sa réticulation des contraintes mécaniques importantes. L’objectif des essais entrepris est de répondre à un certain nombre de questions posées à l’occasion de la rédaction de recommandations sur l’assemblage des voussoirs. L’article décrit les résultats obtenus à l’issue de deux types d’essais, puis en tire quelques conclusions.Le premier type d’essai cherche à déterminer l’épaisseur résiduelle d’un joint de colle soumis à divers cycles de serrage. Celle-ci se trouve être comprise entre 0,4 et 0,7 mm, et il apparatt que le dosage initial de colle ainsi que les cycles de serrage ont peu d’influence sur l’épaisseur résiduelle du film decolle.Le second type d’essai vise à étudier la résistance en compression-cisaillement d’assemblages colis qui ont été soumis auparavant à des cycles de serrage pendant la réticulation de la colle. Si toutes les éprouvettes périssent par rupture en compression du béton, la présence d’un joint provoque une chute sensible de la résistance en compression de l’éprouvette.

Les recherches menées au LCPC en vue d’étudier l’adhérence des résines époxydes sur des surfaces de béton durci, sèches ou humides ont permis de constater que les polymères non chargés (résines pures) peuvent adhérer de façon satisfaisante au support béton à condition que celui-ci soit sec. En effet lorsque il y a présence d’eau (support humide) les résines pures présentent dans le collage du béton durci sur béton durci une rupture adhésive, alors que les mêmes produits convenablement chargés conduisent à une bonne adhérence puisqu’il y a rupture dans le béton.Par ailleurs les modes de ruptures adhésive, dans le béton ou cohésive sont fonction de la nature minéralogique de la charge, de sa granularité et de l’épaisseur du joint.De même l’adhérence sur support humide serait liée à l’absorption, plus ou moins élevée, de l’eau présente sur la surface du béton et mise en contact ave le polymère.

Le paramètre “module de rigidité” est très rarement pris en compte dans le choix de la colle d’assemblage acier-béton ou béton-béton. Plus exactement on estime que plus ce module est élevé meilleur sera l’assemblage. Contrairement à cette opinion courante, nous pensons qu’il est des cas où une minoration raisonnable du module de rigidité est souhaitable pour la tenue de l’assemblage. Ces cas nécessitant des colles “assouplies” sont ceux des ancrages de grande longueur et forte capacité.

Some experiments have been done in which the adhesion on the resin concrete phase boundary — steel bar was marked. Bare of epoxy resin and polyester rollers were stretched. There were several variants of steel bars of different level of corrosion and surface cleaning as well as different kinds of anticorrosion coating.None of the variants showed a considerable technique-wise reduction of adhesion. In some cases a significant increase of adhesion was observed.

The technique of strengthening reinforced concrete structures by means of epoxy bonded steel plates becomes more and more familiar in renovation industry. It shows to be a reliable and fast repair method, not only under normal laboratory conditions but also under atmospheric and sustained loading conditions. The creep effects in the epoxy joint are very limited, without affecting the mechanical strength of the connection. The preparation of the elements and the execution of the repairing operation turns out to be of great importance. At high temperatures, a weakening of the epoxy-joint appears which calls for insulating measures.

Adopting the technique of glueing flatsteel components to existing rc-structures for the purpose of modifying the loadbearing capacities of structural systems in case of changing demands has become a common method. Regulations of such techniques for the FRG are covered under Certificate No Z-26.1–1 of IfBt, Berlin since october, 1979. The method has to date been limited to predominantly static loads according to DIN 1055 P.3, thus excluding special cases of impact loads, frequent repetition of loads or action of unbalanced machinery or other dynamic live loads. It is obvious that a reasonable number of structures are exposed to dynamic load conditions. Adopting the glueing technique as an economic method of preserving existing structures is a future demand.The forementioned certificate will be reissued in the near future to allow for dynamic loads. The revisions are based on the encouraging results of fatigue tests with subsequent ultimate static bending of tee-beams in the EMPA-laboratories for material testing and research of Switzerland. Some eminent testing results will be described to prove the efficiency of the method.

Les polymères et d’abord les époxydes étaient utilisés a joindre l’acier au béton arme pour le renfcer. En renforçant les, constructions de béton ton arme il faut prendre en consideration les fissures qui se trouvent dans le beton. Cela peut provoquer une augmentation locale des contraintes de cisaillement dans l’assemblage par collage. Les resultats des essais indiquent que les contraintes de cisaillement formées dans l’assemblage par collage dépassent (dans certains cas) la résistance au cisaillement de cet assemblage.

Strengthening of concrete structures in situ by bonding steel plates to concrete surfaces using epoxy resins is now recognised to be an effective and convenient method of improving their performance under service loads or to increase their ultimate strength. The main advantages of the technique are that the operation can be carried out relatively quickly and simply even while the structure is in use. Although the technique has been widely used in various parts of the world, there is very little systematic information on the service load behaviour of plated beams, particularly in relation to cracking.In this paper comprehensive test data are presented on the effect of glued plates on the cracking behaviour of reinforced concrete beams strengthened with such plates. The variables studied in this project include plate thickness, glue thickness, layered plates and lapped plates. The structural behaviour of these beams was closely monitored during testing to destruction, and extensive crack measurements were made to evaluate the effectiveness of the glued plates on crack spacing and crack width.The paper will present a detailed analysis of the cracking data. It will be shown that maximum crack widths are substantially reduced in the plated beams compared to unplated beams. The test results are compared to existing crack width equations in design codes. New equations are developed to predict crack width in plated reinforced concrete beams.

En collant une armature extérieure on peut souvent obtenir un renforcement efficace des éléments en béton armé dans les cas de réparation due à différentes causes. On a présenté dans le travail les résultats des recherches expérimentales effectuées sur les poutrelles exposées â la flexion jusqu’à la rupture. On a examiné les cas suivants: poutrelles en béton non armé; poutrelles armées au moyen d’armature extérieure collée, grâce à une sorte de résine époxyde, à la surface inférieure tendue; poutrelles classiquement armées; poutrelles avec armatures classique et extérieure (combinaison d’armatures des deux cas précédents). On a également analysé les données sur l’apparition des fissures, sur l’importance et le caractére de la rupture pour les cas particuliers examinés.

The working joints of many span-wise built p/c-bridges are cracked. Thereby, the fatigue stresses in the prestressing steel at the joints, where all tendons were coupled, increase markedly. To prevent premature fatigue failure, strengthening of the joints became necessary.The injection of cracks has not proved to be a sufficient countermeasure for all bridges. The fatigue stresses can be reliably reduced by additional steel plates bonded to concrete with suitable epoxy resin adhesives. The first successful application of this strengthening method was carried out on an Autobahn-bridge near Dortmund in 1981. Its efficacy was proved by load tests. Other bridges followed. The use of fibre composite plates instead of steel plates is also tested. The rules for the dimensioning and bonding of the plates and for accelerated durability tests of bonded joints are presented.

Research into the bond and durability of polymer-mortared studs was carried out according to the UKA 3 technology method. The studs were also exposed to extreme weather conditions and chemical influences as well. In the pull-out-tests 18-years old bolts had a shear failure between the mortar and the steel stud. The shear strength after 8 1/2 years of weathering reached an average value of 14,5 N/mm2 which corresponds to the average value of bond strength reached after one day of curing.The bond specimens that were sustained under a steady load and cured in alkalic concentrated water for over a period of 8 1/2 years showed a larger slippage in the bond than those cured under dry condition, the strength, however, was the same.Moreover it was found that cracks of 0,3 mm in concrete caused a strength reduction of 50% for studs of 20 mm in diameter and 80% for studs of 10 mm in diameter.

Dans cet étude on a analize une jonction plaquée tout en considerant que les subjectiles sont élastiques et que l’adhésif est viscoélastique de façon lineâire. Après avoir formulé le probleme sous forme générale, en considerant deux modèles de fluage de l’adhésif, on a developpe’ des exemples specifiques pour differents épaisseurs. La distribution des contraintes et autres paramètres significatifs ont été calcules au moyen d’une methode discrète d’analyse. Les résultats montrent que la valeur maximale de la contrainte de cisaillement dans la jonction plaques diminue de façon differente selon le modèle de fluage considere et le moment où on applique la force.

The design of concrete strengthening by the application of steel plates bonded to the concrete surface requires a very good knowledge of the mechanical behavior of the strengthened structures. The paper deals with following aspects of the behavior of bonded steel plates: (a)Local behavior of a bonded steel plate in the vicinity of a crack. This study reveals local bending of the plate. The influence of the different parameters has been invistigated.(b)Study of assmbly failures. It is possible to predict the failure of repaired structures strengthened under normal force, bending moment and with regards to shearing force when using the concepts of brittle fracture mechanics. Some experimental determination of the energy release rate is presented.(c)Distribution of deformations between reiforced bars and bonded steel plates. Calculations carried out on a numerical model of reinforced concrete tie member show that the hypothesis of plane deformation is not verified. These partials results need to be confirmed by experience.

En france, les produits de réparation du beton sont qualifiés par le LCPC qui édite une liste d’aptitude nationale. La procédure de qualification, élaborée par des représentants des utilisateurs et des fabricants, est présentée dans cette communication sous l’aspect de son fonctionnement, son organisation et son contenu, en particulier en ce qui concerne les essais d’efficacité effectues pour les différents types de produits de réparation existant sur le marché.

Pour assurer la continuité entre les éléments d’une structure en béton et ceux à rapporter, l’utilisation des ancrages en acier est souvent en application. Selon le principe généralement admis dans la construction en béton armé, la rupture eventulle et accidentelle devrait être précédée des signes précurseurs de la défaillance: fissures, déformations,. C’est pourquoi il convient que le scellement soit dimensioné de façon à ce que l’arrachement soit précédé de la plastification de la barre (dépassement de sa limite élastique apparente ou conventionnelle) accompagné éventuellement d’un glissement limité. Les recherches du Comité Technique RILEM-CEB-FIP ont conduient, en outre, à l’établissement des Recommandations: RC 5: Essais d’adhérence, 1. Par flexion, 1978 (Bond test for reinforcing steel, 1. Beam test, 1978) et RC 6: Essai d’adhérence, 2. Par traction, 1978 (Bond test for reinforcing steel, 2. Pull - out test, 1978). Le texte qui suit présente une tentative de comparaison d’efficacité d’amarrage des barrés à adhérence améliorée dans le béton frais et des barres lisses fixées par l’adhérence ou mécaniquement dans le béton durci. En particulier sont examinés la répartition des contraintes de cisaillement le long d’ancrage adhésif d’une part et le mécanisme de rupture de l’ancrage à expansion d’autre part. Quelques remarques soulignent l’importance des soins à apprter lors de préparation de scellemnt des ancrages au mortier de résine ou encore au mortier à liant hydraulique modifié.

Structural joints are often subjected to complex multiaxial state of stresses. In design, however, the ultimate load carrying capacity is roughly estimated by limiting the simple tensile, compressive and shear stresses of substrate or adhesive materials.Adhesive materials have different properties from concrete. Generally their tensile to compressive strengths ratio is more favourable than for concrete. The evaluation of adhesive materials is done in laboratory tests under simplified states of stresses, different from the states in application.This paper presents an analysis of the state of stresses in certain laboratory tests applying the failure criteria for each part of the joint. The limitation of these tests in application is also pointed out.

Commercially available aqueous polymer dispersions of various types are compared with respect to their bonding properties when used to adhere repair mortars to cementitious substrates. Polymer dispersions tested include a number of acrylates and styrene-acrylates, a styrene butadiene, a vinyl acetate, an acrylate versatate and a vinyl acetate acrylate versatate. A composite bonding aid, an epoxy bonding system and the use of cement and polymer/cement slurries are also examined. Three different test methods are used to measure bond and a simple comparative test has been developed to monitor ‘grab’. The merits of these tests are discussed. The best all round performance including tolerance to site use has been found to be given by an acrylate dispersion.

New building materials for repair of concrete structures have to be investigated by qualification tests to estimate their long-term behaviour. This report deals with such tests for polymer cement concrete (PCC) composite repair systems hardening under dynamic loading followed by thermal cycling tests on the cured composite specimens. Test results showed that shrinkage of PCC and/or thermal stressing of the composite system especially in the bonding interface are decisive for durability of PCC layers on concrete, whereas dynamic loading of the fresh composite system seems to be of minor consequence.

A new type of exterior wall panels have been developed for a prefabricated house system. These panels are produced by bonding ceramic tiles by use of chloroprene adhesive, butyl rubber sheet, and polyurethane adhesive on cemented wood chip boards fixed to light gauge steel frames in a factory. Such panels are less dangerous for falling off of tiles against deformation of panels due to flexibility of an adhesive layer, however, it seems that bonding durability against weathering or creep behavior must be checked. In order to evaluate bonding durability of the panels, various experimental approaches were performed such as an accelerated weathering test, an ozone resistance test, a boiling test, and a creep rupture test. Among these test, the creep rupture test which was conducted at various temperature and loading in both dry and wet condition was successful in obtaining quantitative information regarding with service life time of creep rupture of the bonded tiles. The data obtained were analyzed by means of the Larson-Miller method (F.R. Larson and J. Miller, Trans. ASME, Vol. 74, 765 (1952)), and finally master curves in both dry and wet condition could be obtained for the objected bonding system. It seems that the Larson-Miller method is useful for evaluating bonding durability of such elastomeric adhesive systems.

The repair and maintenance sector of the construction industry has become a growing sector in recent years. In the market there are many repair systems which has made the choice of the appropriate system very difficult. As far as the repair is concerned, chieving a good bond between the repair and the original concrete is essential. To date a few methods of testing the bond strength between the repair and original concrete have been suggested but mainly these are tests which must be carried out under laboratory conditions. In addition there is the question of the applicability of laboratory test results to actual site conditions. This paper describes insitu testing methods which can be used to determine the tensile and shear bond strengths between the repair and original concrete. Comparisons have been made between these methods and a compression/shear method.

This paper deals with the adhesion or bond strength of polymer-modified mortars to ordinary cement mortar, which is tested by different methods, and the effects of polymer types and polymer-cement ratio on the adhesion. Polymer-modified mortars using a commercial styrene-butadiene rubber (SBR) latex, ethylene-vinyl acetate (EVA) emulsion and polyacrylic ester (PAE) emulsion are prepared with various polymer-cement ratios, and tested for adhesions in tension, flexure and compressive shear. Substrate used is a mortar with a ratio of cement to standard sand 1:2. The test results obtained are summarized as follows: (1)The adhesions in tension, flexure and direct compressive shear of the polymer-modified mortars increase with a raise in the polymer-cement ratio regardless of the types of polymers and specimens.(2)The adhesion in slant (indirect) compressive shear of the polymer-modified mortars reaches the maximum at a polymer-cement ratio of about 5%.(3)The failure mode distribution of the polymer-modified mortars remarkably depends on the test methods and polymer-cement ratio.(4)The adhesion test methods which can successfully reproduce service conditions in the practical applications of the polymer-modified mortars are recommended.

Perfect adhesion of polymer modified cement mortars (PCC-mortars) on concrete is of vital importance in applications such as repair, flooring, waterproofing or corrosion protection of concrete structures. Suitable adhesion test procedures have therefore to be developed. In this paper the complexity of adhesion testing is discussed. A program of adhesion tests, as used in our R + D laboratories for the development of new mortar products, is presented. It consists of three system tests: a preliminary test for qualitative evaluation of the adhesion and cohesion properties of the mortar on concrete; a test to determine the adhesive tensile strength and the durability of adhesion in low and high humidity environment; and an ageing test in which the adhesive tensile strength behaviour is investigated under cyclic temperature changes of the environment including freezing/thawing with deicing salts. The test performance of epoxy and styreneacrylate modified cement mortars is analysed.

Tests are reported to investigate the shear bond strength of epoxy resin adhesives to concrete and steel adherents. Two types of tests were carried out on composite steel-epoxy-concrete specimens — pull out tests, in which failure always occurred through the concrete — glue bond, and single and double lap tests to examine the epoxy shear adhesion to steel adherents. It was found that the distribution of the longitudinal forces and shear stresses along the joint was exponential for both types of tests. The shear bond strength of epoxy to concrete varied almost linearly with concrete strength. However, variations in the adhesive layer thickness, in the range 0.5 to 3.0 mm, had practically no effect on the strength of the pull out or double lap specimens. The results obtained show that both the pull out and double lap shear tests can be carried out with a good degree of accuracy and consistency.