Recycled concrete is among the rising eco-friendly construction materials which helps to reduce waste and the need for new natural resources. However, such concrete may present previous deterioration due to, for instance, alkali-silica reaction (ASR), which is an ongoing distress mechanism that may keep being developed in the recycled material. This work aims to evaluate the potential of further distress and crack development (i.e. initiation and propagation) of AAR-affected RCA concrete in recycled mixtures displaying distinct past damage degrees and reactive aggregate types. Therefore, concrete specimens incorporating two highly reactive aggregates (Springhill coarse aggregate and Texas sand) were manufactured in the laboratory and stored in conditions enabling ASR development. The specimens were continuously monitored over time and once they reached marginal (0.05%) and very high (0.30%) expansion levels, they were crushed into RCA particles and re-used to fabricate RCA concrete. The RCA specimens were then placed in the same previous conditions and the “secondary” ASR-induced development monitored over time. Results show that the overall damage in ASR-affected RCA concrete is quite different from affected conventional concrete, especially with regards to the severely damaged RCA particles, where ASR is induced by a reactive coarse aggregate, as the RCA particle itself may present several levels of damage simultaneously caused by past/ongoing ASR and newly formed ASR. Moreover, the influence of the original damage extent in such RCA concrete was captured by the slightly damaged RCA mixture eventually reaching the same damage level as the severely damaged mixture. Furthermore, the original extent of deterioration influence the “secondary” induced expansion and damage of RCA concrete since the higher the original damage level, the higher the cracks numbers and lengths observed in the RCA concrete for the same expansion level whereas wider cracks are generated by RCA having previously been subjected to slight damage thus indicating the difference in the distress mechanism as a function of original extent of damage. In addition, it has been found that distress on RCA containing a reactive sand generates and propagates from the residual mortar (RM) into the new mortar (NM) as opposed to RCA containing a reactive coarse aggregate, being generated and propagated from the original coarse aggregate (i.e. original virgin aggregate – OVA) into the NM. Likewise, RCA containing a reactive sand caused longer and higher number of cracks for the same “secondary” induced expansion than the RCA made of reactive coarse aggregate. Finally, novel qualitative and descriptive models are proposed in this research to explain ASR-induced distress generation and propagation on RCA mixtures made of reactive fine and coarse aggregates.

Les réactions de gonflements internes (RGI) sont des pathologies qui dégradent le béton de certains ouvrages tels que des barrages en étant à l'origine de gonflements. Electricité De France (EDF) doit assurer la sûreté des personnes et des biens situés à l'aval de ses structures. Ce travail a pour but d'améliorer la modélisation des phénomènes physiques liés à ces dégradations notamment l'interaction entre le produit gonflant et le squelette solide. La contrainte intraporeuse générée par la pression du produit peut créer un endommagement. Dans le modèle proposé, la fissuration peut avoir lieu à deux échelles : - Au niveau microscopique c'est le produit gonflant qui comble le volume libre autour du site de réaction avant de mettre en traction le matériau jusqu'à fissuration, ce qui provoque une baisse des caractéristiques du matériau (résistances en traction et en compression, module d'Young). Un critère de plasticité anisotrope et une loi d'écrouissage positif sont proposés pour modéliser ce phénomène. - Au niveau macroscopique, des gradients de gonflements peuvent se développer à l'intérieur d'ouvrages dont les états de contraintes et les conditions d'humidité et de température ne sont pas homogènes. Une fissuration localisée peut alors s'initier. Elle est la source de risques de dislocations des structures pouvant mener à leur ruine, de concentrations de contraintes dans les aciers structuraux, de chemins facilités pour les agents agressifs extérieurs et pour l'eau, composé essentiel au développement rapide de ces pathologies. La prise en compte des couplages hydro-poro-mécaniques est nécessaire à la simulation de ces phénomènes. Cette fissuration est modélisée par un critère plastique de Rankine anisotrope dont l'énergie dissipée par la fissuration est régularisée par la méthode d'Hillerborg. Après avoir présenté ce modèle, il est validé et appliqué à différentes échelles pour des états de contraintes et des conditions environnementales diverses, sur : - des éprouvettes soumises à des contraintes et des blocages multi-axiaux, - des poutres de laboratoire plus ou moins armées subissant des gradients d'humidité importants, - des barrages dans des conditions réelles construits dans les années 1950. Les résultats obtenus avec le modèle permettent de retrouver les déplacements, les contraintes et les résistances de ces structures après vieillissement. Pour les poutres atteintes de réaction alcali-silice, les résultats numériques obtenus montrent notamment une prise en compte réaliste des contraintes induites par la présence d'armatures, ce qui est confirmé par la validation du comportement à rupture. Néanmoins, des difficultés de calage subsistent pour les poutres subissant la réaction sulfatique interne. Elles sont issues des grandes amplitudes d'expansion et des couplages diffusion-fissuration qui rendent spécifique le comportement de ces structures par rapport à des structures subissant des expansions moins importantes. Ce modèle est un outil pour la requalification des ouvrages dans le but d'assurer leur sûreté. Il peut également servir de base de calcul à la simulation de diverses réhabilitations et travaux de confortements. / Internal swelling reactions (ISR) damage the concrete of structures such as dams. Electricité De France (EDF) must ensure the safety of the people and goods located below the dam. This work aims to improve the modeling of the physical phenomena related to these damages, especially the interaction between the swelling product and the solid skeleton. The intraporous stress generated by the product pressure can create cracking, which, in the proposed model, can occur at two scales: - At a microscopic scale, the swelling product fills the gaps around the reaction site, which induces cracking and a decrease of the materials' characteristics (tensile and compression strengths, Young's modulus). Numerically, an anisotropic plastic criteria and a hardening law allow modelling this phenomenon. - At a macroscopic level, swelling gradients can develop inside concrete structures whose stress states and climatic conditions (humidity and temperature) are not homogeneous. A localized cracking can begin. It is a source of structure dislocation risks and stress concentrations in structural reinforcement. It may ease the way in for outside aggressive agents and water, an essential component for these reactions. Hydro-poro-mechanical couplings need to be taken into account when simulating these phenomena. The cracking is modelled by a Rankine plastic criterion whose dissipated energy is regularized by the Hillerborg's method. After presenting the model, several stress states and environmental conditions are applied to the model in order to validate it on: - samples under multi-axial stresses and restraints, - plain and reinforced beams submitted to moisture gradients in laboratory, - 1950s dams in real conditions. The results of the model make it possible to reproduce the displacements, the stresses and residual strength of these structures after aging. For the beams submitted to alkali aggregate reaction, the numerical results show a relevant prediction of the stress induced by reinforcement, confirmed by the failure behaviour. Nevertheless, the model encounters calibration difficulties for beams affected by delayed ettringite formation. They come from large swelling amplitude and diffusion-cracking coupling which are inherent to these structure behaviours. This model is a tool for concrete structure requalification in order to ensure their safety. It can also be a basis for diverse rehabilitations and reinforcement works simulation.