Thermomechanical couplings in the consolidation of an unsaturated clayey silty sand are investigated. The couplings are analysed through the influence of the temperature (relative to the total vertical stress) on the mechanical characteristics (relative to thermal) of the consolidation. They are evidenced by means of two types of tests (thermal consolidation and mechanical consolidation). The two types of tests lead to quantitative results comparable with regards to characteristic parameters of both types of consolidation. Some elements of interpretation are proposed to integrate all of the experimental results within a framework of thinking resorting to the thermoelastoplastic behaviour of the soil under study and to the thermal and mechanical hardening phenomena.Key words: unsaturated soils, consolidation, thermal, mechanical, coupling, hardening.

The following work is an experimental study of the behaviour of very early-age concrete. Six different concretes, four of them containing recycled coarse aggregates were studied for the first 2.5 hours. The studies were carried out in a ventilated tunnel in order to imitate severe desiccation conditions. In order to indirectly obtain the permeability coefficient, settlement, capillary depression and evaporation were measured for all six concretes. The initial permeability coefficient of each concrete is determined starting from initial bleeding rate. The use of recycled coarse aggregates leads to a high bleeding rate for high water to cement ratios. Permeability coefficients at air entry are then determined starting from capillary depression gradients. Recycled coarse aggregates do not seem to influence the air entry value which is highly dependent on the paste quality. At air entry, the permeability coefficient of recycled coarse aggregates concrete mixes is higher than that of natural aggregates concrete mixes. At high evaporation rates, in severe desiccation conditions, recycled coarse aggregates seem to reduce bleeding for mixture with low water cement ratios. Permeability coefficient is a key physical parameter to understand drying of fresh concrete.

International audienceThere is increased interest in the use of recycled aggregates in concrete formulation as part of strategy of waste recovery. The French National Program RECYBETON aims to move the scientific boundaries relative to the use of recycled aggregates into concrete. In that context, the objective of this study is to qualify and quantify the hydric transfers between the recycled coarse aggregates and cement paste during the mixing and the dormant period. Two families of concrete are tested: concretes for building and concretes for civil engineering structures with Water/Cement ratios equal to 0.6 and 0.45 respectively. The concrete mix design of the reference (natural aggregates) and recycled concrete have been calculated by the national program and specific initial slumps and 28 days compressive strengths are targeted. An original test is proposed in order to separate the fully and partially saturated recycled coarse aggregates from the fresh cement paste. It was observed that in our test conditions, absorption occurs quickly independent of the initial saturation degree of the recycled aggregates and the paste volume and the paste water content are stable at the end of mixing. To exacerbate desorption phenomena and to provoke early age cracking, a severe drying is applied on fresh concretes. In presence of a relative high speed of wind, water desorption of recycled aggregate is observed. A strong relationship between the time of initiation of the cracking and the total water content is established for recycled concrete: the time of ignition is an increasing function of the total water content. Recycled concretes tend to have wider cracks opening compare to reference concrete. The effect of transfer phenomena on other concrete properties such as slump and compressive strength is also discussed

This paper deals with thermo-hydromechanical behaviour of nonsaturated soils. The constitutive relationship presented herein allows for the prediction of the settlement or swell of an unsaturated soil under nonisothermal oedometric conditions. Mechanical, hydraulic, and thermal compression indexes are considered for stress, capillary pressure, and temperature variables, respectively. The implementation of the relationship in a prediction scheme requires preliminary characterization of these indexes. The stress–strain and water volume change relationships are first presented from semiempirical point of view for a nonsaturated soil element under nonisothermal conditions. These relationships allow for the expression of a thermo-hydromechanical constitutive law for nonsaturated soils and propose a relationship for the change in the soil water content. The thermal compression indexes are then determined for a clayey silty sand, first using a reverse method and then a direct method. This determination is made from experimental data recorded on a prototype involving heat storage in an aquifer. The values of these thermal compression indexes are finally compared with the laboratory values obtained in a thermal triaxial cell on samples of the same soil. Key words: nonsaturated soils, thermo-hydromechanical, oedometer tests, thermal compression indexes, characterization, reverse method, direct method.[Journal Translation]

The use of recycled aggregates in concrete mixtures is a part of waste recovery strategy. The French national project RECYBETON aims at developing scientific knowledge to facilitate the use of recycled aggregates into concrete. In this experimental study, two exposure conditions were combined to analyse the behaviour of fresh and hardening concrete in standard and severe drying conditions (8 m.s -1 wind speed). High evaporation rate promotes the development of plastic shrinkage and cracking of fresh concrete. The influence of recycled concrete aggregates proportion and initial water saturation rate were investigated. Two series of concrete mixtures were designed to reach two strength classes. The strains and weight loss of concrete samples were monitored until the stabilization of plastic shrinkage. The increase in evaporation rate accelerated the development and increased the maximum value of plastic shrinkage but did not significantly influence the shrinkageto-weight loss ratios. In severe conditions plastic shrinkage developed before initial setting thus reached higher magnitudes. The main mix-design parameter affecting the shrinkage-to-weight loss ratio and cracking was the total water-to-binder ratio. The total water content includes the water added and the water used to pre-saturate the aggregates. High evaporation rate triggered the release of water initially absorbed by recycled concrete aggregates.