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The Al2O3-SiC-C or ASC castables are used in the main runners of blast furnaces. Most of the papers published to date focus on laboratory corrosion tests because access to the post-mortem samples of ASC castables is difficult. However, investigation of post-mortem samples is crucial in reducing the wear of ASC castables. The main runner is divided into the turbulence, middle, and non-turbulence zones. The microstructures of post-mortem samples located in working linings of different zones were investigated by SEM/EDS technique. The thermodynamic simulations were carried out in different systems, such as slag/refractory and iron/refractory, using the FactSage software. The SEM/EDS results showed the formation of phases with low melting points, such as gehlenite and anorthite, together with spinel solid solutions in the matrix and calcium dialuminate near the alumina aggregates. The thermodynamic simulations showed that slag and iron tend to react with alumina and silicon carbide, respectively.

Production of energy from nuclear power plants generates high-level radioactive nuclear waste, harmful during dozens of 1000 years. Deep geological disposal of nuclear waste represents a reliable solutions for its safe isolation. Confinement of radioactive wastes relies on the multi-barrier concept in which isolation is provided by a series of engineered (canister, backfill) and natural (host rock) barriers. Few underground research laboratories have been built all over the world to test and validate storage solutions. The drilling of disposal drifts may generate cracks, fractures/strain localisation in shear bands within the rock surrounding the gallery especially in argillaceous rocks. These degradations affect the hydro-mechanical properties of the material, such as permeability, e.g., creating a preferential flow path for radionuclide migration. Hydraulic conductivity increase within this zone must remain limited to preserve the natural barrier. In addition, galleries are currently reinforced by different types of concrete supports such as shotcrete and/or prefab elements. Their purpose is twofold: avoiding partial collapse of the tunnel during drilling operations and limiting convergence of the surrounding rock. Properties of both concrete and rock mass are time dependent, due to shotcrete hydration and hydro-mechanical couplings within the host rock. By the use of a hydro-mechanical coupled finite-element code with a second-gradient regularization, this paper aims at investigating and predicting support and rock interactions (convergence and stress field). The effect of shotcrete hydration evolution, spraying time, and use of compressible wedges is studied to determine their relative influence.

ABSTRACTA three-dimensional rheological modelling is proposed for the long term concrete mechanical behaviour. Concrete is supposed to have a non-linear visco-elastic behaviour. The non-linearity used first allows conferring a realistic non asymptotic strain to the basic creep, based on a consolidation theory. Moreover, for the non-saturated concrete, a dependence of the capillary pressure effects on the stress state is postulated. It assumed that a damage state exists around microcavities in depression, this damage depends also on the applied stresses whose can led to a closing or opening of the micro-cracking and consequently to a best or to a worst transmission of capillary effects to the solid skeleton. This dependency is highlighted using a simple numerical analysis of a composite material including in an elastic matrix both cavities in depression and rigid inclusions. The linear dependence of capillary effect on the applied stress confers to the model the capability to simulate shrinkage and drying creep strains.

ABSTRACTThis paper presents a model predicting the early age cracking of structures. It is a promising tool to help industrials choose the materials and the construction techniques which reduce the cracking risk. The proposed model uses a multiphasic modelling of binder hydration predicting the hydration development of several anhydrous species (clinker, fly ash, silica fume…). The results of this first modelling are used as input data for a mechanical modelling of the non linear behaviour of concrete at early age (evolution of mechanical properties, creep, and damage).

ABSTRACTA rheological model with orthotropic short-time and long-time damage is developed in order to model leached concrete behaviour. Coupling with calcium leaching is obtained by affine attenuation of model parameters according to a microhardness profile measured on leached cement pastes. Calibration shows that most model parameters managing mechanical behaviour have the microhardness law as their attenuation law.

ABSTRACTA probabilistic approach of the corrosion risk of reinforcements embedded in a concrete beam due to the carbonation of the cover concrete is proposed, based on the computation of the Lind-Hasofer reliability index. The a priorimost influential parameters governing the carbonation of concrete have been accounted for namely: the diffusion coefficient of carbon dioxide in concrete, and the concrete cover depth. A comprehensive and efficient finite elements method has been achieved for modeling the penetration of carbon dioxide in concrete. The method takes into account the strong non-linearties in relation with this phenomenon: the non-constant diffusion coefficient of carbon dioxide in the cross-section of the beam, and the steep slope profile of the calcium content in concrete due to its transformation when calcite precipitates. The improved gradient algorithm given by Rackwitz/Fiessler has been used for searching the reliability index. In order to avoid an extensive number of finite elements computations in the gradient algorithm, a quadratic response surface method has been resorted to. The optimal cover thickness of a reinforced concrete beam has been determined thanks to this probabilistic approach.