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This experimental study aims to determine the effect of relative humidity on concrete expansion due to delayed ettringite formation (DEF), which still remains imperfectly known. Test methods were designed to trigger reaction in concrete specimens and determine how ambient RH affects expansion of the specimens. Saturated salts solutions were used to achieve distinct ambient RH conditions within containers. Also, chemical analysis was performed to determine and quantify the fractions of alkalis leaching out of the pore solutions of concretes. Results showed that the critical ambient RH value that corresponds to significant suppression of DEF could be greatly dependent on the alkalis fractions leached out. Finally, the consequences of swelling due to DEF on the concrete properties are assessed. After swelling, both of gas permeability and porosity was increased significantly and dynamic modulus was reduced by about 45%.

EURO-C 2018 - Computationnal Modelling of Concrete and Concrete Structures, BAD HOFGASTEIN, AUTRICHE, 26-/02/2018 - 01/03/2018; Internal swelling reactions (ISR) can affect long term duration of reinforced concrete (RC) structures by causing cracking and expansion of concrete material. These pathologies mainly consist in Alkali Aggregate Reaction (AAR) and/or Delayed Ettringite Formation (DEF). Thus, it is necessary to provide robust predictive numerical models able to re-assess the mechanical state of affected structures. A new numerical strategy is proposed in this paper to compute the evolution of the ISR reaction from intrinsic parameters to be identified for the reactive concrete. Based on Larive's model, evolution of the chemical strain is written in order to assume the irreversibility of the mechanisms and to take into account time history of the Relative Humidity and Temperature supported by the concrete specimen. An effective time is proposed to store history of the reactive concrete and to be able to compute evolution of the chemical strain.

Aging concrete structures affected by Internal Swelling Reactions (ISR) may be quite difficult to manage. Over the past years, several tools were developed to provide diagnostic and prognostic assessment of concrete structures, especially those affected by Alkali-Aggregate Reaction (AAR). Among those tools, the Stiffness Damage Test (SDT), Damage Rating Index (DRI) and Residual Expansion (RE) seem to be promising. However, the comprehensive and complementary character of the prior tools in assessing different mechanisms other than AAR was barely verified, which significantly reduces their use for engineering purposes. This paper presents the overall condition assessment of a concrete structural member affected by coupled AAR and Delayed Ettringite Formation (DEF) through the use of the above techniques. Results show that the three procedures were similarly capable of providing the current damage degree (i.e. quantitative diagnosis), enabling the estimation of the concrete expansion attained to date. Finally, although theoretically different, the test procedures seem to have a somehow complementary character, and could potentially be used together in the understanding of ISR progress, damage generation and future prognosis.

CONCRACK5 - Control of Cracking in Concrete Structures 5, TOKYO, JAPON, 24-/04/2017 - 26/04/2017; Proceedings of the JCI-RILEM international workshop on control of cracking of mass concrete and related issues concerning early age cracking of concrete (Concrack5).

The aim of the present recommendations is to limit the risk of disorders occurring due to an internal sulphate reaction. The latter is caused by the delayed formation of ettringite in a cementitious material and occurs in particular because of a significant heating of the concrete intervened several hours or several days after its casting. It causes an expansion of concretew hich in turn generates a cracking of the structures. This reaction can be encountered with two types of concrete: heat-treated concretes and concretes cast in place in so-called critical elements. These recommendations are concerned with civil engineering structures and buildings comprising elements of important size that are in contact with water or subjected to a wet environment. They set the level of prevention to be achieved according to the category of the structure (or to the part of the structure) and to the exposure conditions. For each of the four levels of prevention selected, associated precautions are applied and associated checks are carried out. They also contain provisions relating to the design and dimensioning of structures, the composition and manufacture of concrete, and its pouring.The present recommendations combine a performance approach and specifications of means, and are an update of the previous 2007 recommendations they are replacing, taking into account new knowledge gained since., Les présentes recommandations ont pour objectif de limiter le risque d'apparition de désordres liés à la réaction sulfatique interne. Cette dernière est provoquée par la formation différée d'ettringite dans un matériau cimentaire et se produit notamment en raison d'un échauffement important du béton intervenu plusieurs heures ou plusieurs jours après son coulage. Elle provoque un gonflement du béton qui engendre à son tour une fissuration des structures. Elle peut se rencontrer avec deux types de béton : les bétons traités thermiquement et les bétons coulés en place dans des pièces dites critiques. Ces recommandations concernent les ouvrages de génie civil et les bâtiments comportant des éléments de dimensions importantes en contact avec l'eau ou soumises à une ambiance humide. Elles fixent le niveau de prévention à atteindre en fonction de la catégorie de l'ouvrage (ou de la partie d'ouvrage) et des conditions d'exposition auxquelles il (ou elle) est soumis(e). À chacun des quatre niveaux de prévention retenus, sont associées des précautions à appliquer et des vérifications à effectuer. Elles présentent également des dispositions liées à la conception et au dimensionnement des ouvrages, à la formulation et à la fabrication du béton, ainsi qu'à sa mise en oeuvre. Les présentes recommandations combinent approche performantielle et prescriptions de moyens, et constituent une actualisation des précédentes recommandations de 2007 auxquelles elles se substituent, en tenant compte des nouvelles connaissances acquises depuis.

The conditions of development of Delayed Ettringite Formation (DEF) in concrete when submitted to excessive heating during hydration and setting have deserved recent research efforts and tend to be better understood. However, quantitative evidence of DEF risk for concrete submitted to similar heating when mature is still scarce. The experimental program described in this paper confirms the risk of DEF-induced expansion for concrete normally cured, then heated after 100 days of age, when further kept in saturated environment, both for a DEF-prone mix and for a concrete made with a low C3A, low SO3 and low-alkali content-cement., Les conditions de déclenchement de la Réaction Sulfatique Interne (RSI) dans les bétons exposés à une température éleÎe en cours de prise ont fait l'objet de récentes recherches et apparaissent mieux comprises aujourd'hui. Cependant, des travaux s'aÏrent nécessaires à la compréhension du risque de RSI sur les bétons matures. Le programme expérimental décrit dans cet article confirme le risque de RSI pour des bétons exposés à un échauffement après 100 jours d'hydratation dans des conditions classiques. Les expansions se développent pour des matériaux exposés à l'humidité pour un béton potentiellement réactif à la RSI mais également pour un béton contenant un ciment à faible teneur en C3A, en sulfates et en alcalins.

Aging concrete structures affected by internal swelling reactions (ISR) may be quite difficult to manage. Over the last few years, several tools were developed in order to provide diagnostic assessment of aging concrete structures, especially those affected by alkali-aggregate reaction (AAR). Among those tools, the Stiffness Damage Test (SDT), Damage Rating Index (DRI) and Residual Expansion (RE) seem to have a great potential. However, the comprehensive character of the tools in assessing different mechanisms other than AAR was barely verified, which reduces their use in engineering purposes. This paper presents the results of a study where the above three tools were used for assessing the condition of a concrete structural element damaged by ASR+DEF coupling. Results show that the three procedures were similarly capable of providing a diagnosis quantitative estimate of the expansion attained by the concrete. Finally, although theoretically different, the test procedures seem to have a somehow complementary character, and could potentially be used together in engineering practices., Les structures en béton atteintes de réactions de gonflement interne s'aÏrent délicates à gérer. Au cours des dernières années, divers outils ont été développés pour évaluer l'état des ouvrages, en particulier ceux affectés par la Réaction Alcali Granulat (RAG). Parmi ces outils, on peut citer le Stiffness Damage Test (SDT), le Damage Rating Index (DRI) et l'essai d'expansion résiduelle qui semblent prometteurs. Cependant, ces outils ont été testés de façon limitée sur des réactions autres que la RAG, limitant ainsi leur application dans le domaine de l'ingénierie. Cet article présente les résultats d'une étude mettant en oeuvre ces trois outils sur une poutre atteinte de RAG couplée à la Réaction Sulfatique Interne (RSI). Les résultats ont mis en évidence que les trois outils fournissent des résultats directement en lien avec l'expansion développée dans la structure. Enfin, bien que basés sur des concepts théoriques différents, ces procédures d'essai sont apparues complémentaires et se réÏlent prometteuses pour le domaine de l'ingénierie.

While the chemical and physical processes associated with alkali-aggregate reaction and delayed ettringite formation, otherwise known as internal swelling reaction mechanisms, have now been the subject of considerable research spanning several decades, the actual implications for affected structures are still open to debate. This may be partially attributed to the fact that parameters affecting structural response such as confinement effects, boundary conditions, anisotropy and loading conditions vary greatly among various structures. It is also worth noting, however, that the correlation between data obtained from material-level analyses and the in-situ performance of large-scale structures is still not well understood even at a fundamental level. This paper aims to synthesize our current knowledge of the structural implications of internal swelling mechanisms in concrete structures, in order to highlight major knowledge gaps and contribute towards a critical discussion of the importance of pursuing multi-scale testing regimes for the assessment of aging infrastructure., Les mécanismes physico-chimiques associés à la réaction alcali-granulat et à la réaction sulfatique interne (également dénommés génériquement Réactions de Gonflement Interne) ont fait l'objet d'un grand nombre de recherches au cours des dernières décennies. Les implications structurelles de ces pathologies sont en revanche moins bien connues. Ceci peut être attribué au fait que certains paramètres affectant le comportement structurel tel que les effets de confinement, les conditions d'appui, l'anisotropie ou les conditions de chargement varient grandement d'une structure à l'autre. Il convient également de noter que la corrélation entre les analyses à l'échelle du matériau et les performances des ouvrages in situ n'est pas encore maîtrisée pleinement. Cet article a pour objectif de synthétiser la connaissance relative aux implications structurelles des réactions de gonflement interne afin de mettre en évidence les connaissances à acquérir au travers d'une discussion critique sur l'importance de réaliser des essais multi-échelles sur des structures soumises à des pathologies.

CONCREEP 10, VIENNE, AUTRICHE, 21-/09/2015 - 23/09/2015; Delayed Ettringite formation (DEF) is an autogenous expansive reaction that can affect concrete. A long enough exposure to high enough temperature are the necessary conditions to develop DEF. The results of experimental laboratory investigations that aim to quantify the effect of thermal history on DEF characteristics (namely magnitude and kinetics of expansion) are presented. A threshold of temperature for the concrete at early age, a pessimum effect with the heating duration and a relation between thermal energy and swelling parameters (kinetics and magnitude) are highlighted.

Internal swelling reactions (ISR) (which mainly comprise alkali-silica reaction, alkali-carbonate reaction, delayed ettringite formation, etc) are pathologies that affect the long term durability of concrete structures. The reactions are apparently characterized by series of closely spaced, tight map cracks with wide cracks appearing at regular intervals and excessive tensile stresses in rebars. This phenomenon is alarming for affected structure managers as it deals with people safety and structures operation. Moreover, there is no easily implemented way to stop the reactions. Prediction of concrete expansion, structural degradation and assessment of efficiency andperiodicity of repair works are crucial issues. The aim of this work is to explore the applicability of some Non Destructive Techniques (NDT) of investigations (electric, seismic and acoustic methods) to differentiate the structure zones affected and not affected by the ISR for different exposure conditions. The results highlight that the coupling between some of those ND Methods can reduce the measurement uncertainty and eliminate the factors that may influence the characterisation of the structure parts affected by the ISR. Nevertheless, for the complete structure reassessment, it is desirable to also refer to global geometrical/topographical survey and to destructive analysis methods on some cored samples for chemical analysis, petrography and dimensional measurements.