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The development of alkali-activated materials for construction has grown over the past 20 years due to the reduction of environmental impact compared to cementitious materials. In case of materials with high calcium content (limestone) activated by soda solution (without silicate), it is possible, with an optimized formulation, to obtain mortars with compressive strength of 20MPa. The activation products are pirssonite and portlandite. However, due to their solubility, these materials lose much of their mechanical strength in high humidity environments. In order to resolve this problem, finely grinded glass, from recycling bottles, was added at different amounts. The impact of this addition was studied in terms of reaction process, fresh and hardened properties. The addition of grinded glass led to formation of new products, probably hydrated, which are responsible of a significant reduction of mortar porosity but the compressive strength, at 28 days, decreased overall 23% compared to mortars without grinded glass. However, the behavior in humidity environments was significantly improved and the compressive strength was maintained after a leaching test.

Binders based on the alkaline activation of raw materials is a subject of increasing importance for construction. This study focuses on a new non-hydraulic binder based on the alkali-activation of limestone by an aqueous solution of sodium hydroxide. An optimized mortar of about 20 MPa compressive strength, made with siliceous sand, was studied by XRD, FTIR and SEM-EDX analyses showing that crystalline pirssonite and portlandite are the reaction products responsible of the cohesive capacity of the binder. A methodology based on thermal gravimetric analysis was applied to quantify the products formed and the consumption of reagents with high reliability.

This paper presents new materials obtained by alkaline activation, which generally have a lower environmental impact than that based on hydraulic binders. Calcareous filler was alkali activated by sodium hydroxide solutions in mortars prepared with siliceous sand. The chemical, physical and mechanical properties were studied after 28 days curing. XRD showed that setting and hardening processes of the binder result from the crystallization of sodium/calcium carbonate hydrate (pirssonite) and calcium hydroxide (portlandite). Depending on the formulation parameters,the compressive strength reached, after 28 days, 20 MPa [2900 psi] while flexural strength reached 4 MPa [600 psi]. A methodology, based on thermal analysis results, was applied to quantify the formed products and to evaluate the reagents consumption extent. Calculated amounts had a high reliability and corroborated the initial composition of the mortars. These results open interesting possibilities to improve the performances of these new type materials, based on alkali-activated calcareous filler.

High temperatures due to fire are amongst the most critical situations to which concrete may be exposed. For safety purposes, it is important to understand and preview the consequences of fire on the structural integrity of concrete. Concerning high temperatures, the mechanical degradation suffered by a concrete structure is related both to energy and mass transport. Therefore, a realistic modeling of such a condition shall take into account not only a thermal analysis but also the complex physical–chemical reactions developed among the components of that heterogeneous material. This approach is adopted in the present study as an effort to better reproduce the consequences of fluid flow and chemical processes – cement hydration and dehydration – in the material. Numerical simulations of the hygro-thermal behavior of concrete–rock bilayers subjected to fire conditions are performed through a transient and nonlinear model. The adopted model was evaluated by comparisons with data from an experimental program concerning thermal tests on a set of concrete–rock bilayer specimens, aiming to reproduce real world situations observed in some structures, such as tunnels.

The inverse problem of 2D time-dependent heat source reconstruction is solved. The scientific objectives are the quantification of thermal effects associated to the mechanical deformation of materials during tensile tests. The experiment provides infrared measurements of the specimen’s surface temperature and the inverse algorithm aims at providing a volumic heat source that is free of errors due to heat diffusion. This algorithm is based on an analytical solution of the direct problem in the Laplace-Fourier domain. The solution proposed here is compared to a previously used method [1] based on an adjoint formulation and a regularization of Tikhonov type. This allows to check the validity of the results.

International audience; We follow the damage process of high-density polyethylene during tensile tests. We simultaneously track changes in the density and average orientation of cavities using incoherent light transport. At the same time, we measure the true strain with a video-extensometer and the heat with an infrared imager. We see that the damage process has two major separate steps. First, a globally isotropic nucleation and growth of cavities occurs up to a deformation of about 1.1. Then, at higher deformations, cavities stop growing. Instead, they progressively orient and elongate along the tensile axis. The transition between these two damage processes seems to be related to strong physical and geometrical constraints, also probed through a typical thermal signature.

International audience; This paper aims at presenting the complete metrological problem associated to the thermomechanicalcharacterization of materials. With this purpose in view, we first present a model based on irreversiblethermodynamics that allows straightforward formulation of the set of the required state laws. Then, the statelaw, which links both entropy and temperature variables, is used within an entropy balance. It leads to the heatequation allowing for the identification of the different contributions involved in the apparent ThermomechanicalHeat Source (THS). This THS is measured during the tensile experiment of a semicrystalline polymer,thanks to the monitoring of in-situ infrared temperature fields and the subsequent application of numericalreconstruction algorithms. Both stress-strain and THS-strain curves obtained experimentally over the samerepresentative elementary volume are used simultaneously to identify the parameters of the behavioral model.The results first showthat themodel is able to describe the measured THS. Secondly, they allowfor a clear analysisof various thermomechanical contributions (thermoelastic effect, total pure intrinsic dissipation, entropiccouplings contribution reflecting microstructure transformations), which can be very helpful in understandingmicroscopic deformation phenomena.

A combination of three optical techniques is presented for in situ monitoring of macroscopic and microscopic variables characterizing the deformation of polymers. A video extensometer allows for the monitoring of true stress and strain. An infrared imager along with an appropriate mathematical algorithm allows for the determination of the energies that are converted into heat during the whole test. This makes possible a quantification of thermomechanical couplings revealing structural effects at microscopic scales. Finally, incoherent steady light transport is used to produce images of backscattered intensities. A physical model enables the authors to follow damaging processes occurring at microscopic scales.