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International audience; Water in calcium silicate hydrate (C-S-H) is one of the key parameters driving the macroscopic behavior of cement materials for which water vapor partial pressure has an impact on Young's modulus and the volumic properties. Several samples of C-S-H with a bulk Ca/Si ratio ranging between 0.6 and 1.6 were characterized to study their dehydration/hydration behavior under water-controlled conditions using 29 Si NMR, water adsorption volumetry, X-ray diffraction, and Fourier-transform near-infrared diffuse reflectance under various water pressures. Coherent with several previous studies, it was observed that an increase in the Ca/Si ratio is due to the progressive omission of Si bridging tetrahedra, with the resulting charge being compensated for by interlayer Ca, and that water conditioning influences the layer-to-layer distance and the achieved NMR spectral resolution. Water desorption experiments exhibit one step toward low relative pressure, accompanied by a decrease in the layer-to-layer distance. When sufficient energy is provided to the system (T ≥ 40°C under vacuum) to remove the interlayer water, the shrinkage/swelling is partially reversible in our experimental conditions. A change in layer-to-layer distance of less than 3 Å is measured in the C-S-H between the wet and dried states. When the bridging SiO 2 tetrahedra are omitted, interlayer Ca interacts with layer O and water interacts with the cations and potentially with the surfaces. This structural organization is interpreted as a mid-plane monolayer of water in the interlayer space, this latter accounting for about 30% of the volume of C-S-H particles.

International audience

Tracking metal pollution in surface water is a major environmental, public-health and economic issue. Knowledge of the behaviour of metals such as zinc (Zn), in stream sediments and water, is a key factor to improving river water quality. Because the isotopic compositions of Zn can be used as an environmental tracer for tracking the sources of man-made materials and its transport into water and soil, we have used Zn isotopes for studying the anthropogenic impact on a watershed. As a case study, we chose a small watershed in the Loire River basin, near Orleans (France). The Egoutier spring issues in a pristine area, but its water is affected a few kilometres downstream by liquid effluents from a wastewater treatment plant (WWTP) and farther down still by diffuse pollution from road traffic. We sampled the liquid effluents as well as water and sediments along an upstream to downstream transect. For liquid samples, we took “grab” samples and integrated samples using passive DGT (Diffusive Gradients in Thin films) samplers. The advantages of DGT are (1) to pre-concentrate in-situ the Zn dissolved in water—avoiding a time-consuming chemical preparation—and (2) to integrate the potential variations of Zn isotopic signature over time. The mobile fraction of sediments—that released by the leaching in 0.2N HCl—was also investigated. The δ66/64Zn values in water and sediments along the upstream/downstream profile clearly showed the anthropogenic input of WWTP effluents in the river, which was still visible several kilometres downstream in water. This dissolved anthropogenic contribution is easily transported along the transect and only slightly fixed by adsorption on sediments, probably due to their low clay-mineral content. For the farthest downstream sample, affected by road traffic, the pollution source is difficult to discern due to the similar δ66/64Zn values in WWTP effluents and in road-traffic particles. Here, the use of DGT has proved to be a major asset: during a rainfall event, road traffic particles were leached by rainwater, forming runoff with a relatively high Zn content that flowed into the river, and DGT monitoring showed it to be an adequate method for discerning discontinuous anthropogenic input into the river water.

International audience; The SOLSA project aims to develop an innovative on-line-on-mine-real-time expert system, combining sonic drilling, mineralogical and chemical characterization and data treatment. Ideally, this combination, highly demanded by mining and metallurgical companies, will speed up exploration, mining and processing. In order to evaluate the instrumental parameters for the SOLSA expert system, portable and laboratory analyses have been performed on four samples with contrasting lithologies: siliceous breccia, serpentinized harzburgite, sandstone and granite. More precisely, we evaluated the influence of the surface state of the sample on the signals obtained by portable X-Ray Fluorescence (pXRF) for chemistry and portable Infra-Red spectroscopy (pIR) for mineralogy. In addition, laboratory Raman spectroscopy, X-Ray Diffraction (XRD), XRF and ICP-OES laboratory analyses were performed to compare surface bulk mineralogical and chemical analyses. This presentation highlights (1) the importance of coupling chemical and mineralogical analytical technologies to obtain most complete information on samples, (2) the effect of the sample surface state on the XRF and IR signals from portable instruments. The last point is crucial for combined instrumental on-line sensor design and the calibration of the different instruments, especially in the case of pXRF.

International audience; The prediction of the long term trace element mobility in anthropogenic soils would be a way to anticipate land management and should help in reusing slightly contaminated materials. In the present study, iron (Fe) and zinc (Zn) status evolution was investigated in a 100-year old Technosol. The site of investigation is an old brownfield located in the Nord-Pas-de-Calais region (France) which has not been reshaped since the beginning of the last century. The whole soil profile was sampled as a function of depth, and trace elements mobility at each depth was determined by batch leaching test. A specific focus on Fe and Zn status was carried out by bulk analyses, such as selective dissolution, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Fe and Zn status in the profile samples was also studied using laterally resolved techniques such as μ-particle induced X-ray emission (μ-PIXE) and μ-Rutherford backscattering spectroscopy (μ-RBS). The results indicate that (i) Fe is mainly under Fe(III) form, except a minor contribution of Fe(II) in the deeper samples, (ii) some Fe species inherited from the past have been weathered and secondary minerals are constituted of metal-bearing sulphates and Fe (hydr)oxides, (iii) ferrihydrite is formed during pedogenesis (iv) 20 to 30% more Fe (hydr)oxides are present in the surface than in depth and (v) Zn has tetrahedral coordination and is sorbed to phases of increasing crystallinity when depth increases. Zn-bearing phases identified in the present study are: complex Fe, Mn, Zn sulphides, sulphates, organic matter, and ferrihydrite. Soil formation on such material does not induce a dramatic increase of Zn solubility since efficient scavengers are concomitantly formed in the system. However, Technosols are highly heterogeneous and widely differ from one place to another. The behavior examined in this study is not generic and will depend on the type of Technosol and on the secondary minerals formed as well as on the nature and amount of organic matter.

International audience; Within the framework of responsible mining, a SOLSA project (www.solsa-mining.eu) to develop an in-situ tool allowing a quick mineralogical identification of site drill cores has been recently launched. Its objective is to develop new or improved highly-efficient and cost-effective, sustainable exploration technologies. It combines and integrates non-destructive sensors: X-ray fluorescence, X-ray diffraction, infra-red and Raman spectroscopy and 3D imaging. The challenge is to address mixtures of hard and soft rocks, as encountered in a lateritic environment. This paper focuses on the determination of spectral characteristics of laterite drill-cores in the visible to short wave infrared spectral range. One of the most important prerequisites is to study the influence of the surface roughness effect on infra-red spectroscopy analyses. For this purpose, four different rock samples: breccia, sandstones, granite and peridotite, each at five surface states have been considered: as-drilled, as-sawn, polished at 6 µm, polished at 0.25 µm and crushed to powder. The reflectance spectra have been acquired with an ASD Fieldspec 3® spectroradiometer with a contact probe at a sampling surface of 1.76 cm 2 , allowing a spectral analysis at wavelengths from 350 up to 2500 nm. The powder spectrum of breccia presents a higher reflectance than the four other spectra from the same material but weak absorption features. The as-sawn sample presents the higher absorption depth, followed by as-drilled sample and the two polished samples (figure 1). At wavelength 2219 nanometers, a peak of absorption is present. The presence of clay minerals is assumed like illite/sericite with more or less smectite, due to the relatively deep water absorption around wavelength 1900 nanometers. Figure 1: Spectra of Breccia Breccia as-drilled Breccia as-sawn Breccia polished 6 µm Breccia polished 0.25 µm Breccia powder

International audience; Understanding calcium silicate hydrates (CSHs) is of paramount importance for understanding the behavior of cement materials because they control most of the properties of these man-made materials. The atomic scale water content and structure have a major influence on their properties, as is analogous with clay minerals, and we should assess these. Here, we used a multiple analytical approach to quantify water distribution in CSH samples and to determine the relative proportions of water sorbed on external and internal (interlayer) surfaces. Water vapor isotherms were used to explain the water distribution in the CSH microstructure. As with many layered compounds, CSHs have external and internal (interlayer) surfaces displaying multilayer adsorption of water molecules on external surfaces owing to the hydrophilic surfaces. Interlayer water was also quantified from water vapor isotherm, X-ray diffraction (XRD), and thermal gravimetric analyses (TGA) data, displaying nonreversible swelling/shrinkage behavior in response to drying/rewetting cycles. From this quantification and balance of water distribution, we were able to explain most of the widely dispersed data already published according to the various relative humidity (RH) conditions and measurement techniques. Stoichiometric formulas were proposed for the different CSH samples analyzed (0.6 < Ca/Si < 1.6), considering the interlayer water contribution.

International audience; The effects of duration (1-100 days) and temperature (20 and 50 °C) were assessed from batch tests for Ca-bentonite mixed with 10 wt.% lime. The pozzolanic processes were monitored over time by 29Si NMR (Cement Concr. Res. 42, 2012), TGA-DTA, XRD and chemical analysis. Modeling considered kinetics and thermodynamics of mineralogical transformations and cation exchange. Kinetic laws were dependent on pH and temperature (Arrhenius energy). Lime hydration occurs within hours, modifying the bentonite exchangeable population and increasing the pH. These alkaline conditions initiate the pozzolanic reactions in a second stage. The rate-limiting step is the dissolution kinetics of the bentonite minerals, i.e. a relatively fast and total consumption of cristobalite in parallel to a long-term slower dissolution of montmorillonite. First C-S-H and then C-A-S-H are formed consequently. Temperature speeds up the pozzolanic reaction kinetics by a factor 5 from 20 to 50 °C, corresponding to an apparent activation energy of 40-50 kJ/mol.