Salt weathering poses significant challenges to the durability and integrity of construction materials across various engineering applications. This study introduces a novel accelerated salt weathering protocol designed for standardised laboratory testing, aimed at evaluating the effects of salt crystallisation on natural rocks and construction materials. The protocol was validated using three distinct materials: Flysch rocks, Vosges sandstone, and high-performance concrete. The core protocol features continuous partial immersion of cylindrical-shaped samples in a 3 molal sodium sulphate solution at 32 °C. At the same time, room temperature is maintained at 20 °C, providing well-defined boundary conditions for easy reproducibility and potential numerical modelling. Non-destructive monitoring techniques, including time-lapse photography coupled with Digital Image Correlation (DIC) and acoustic emission (AE) analysis, were integrated into the core protocol. In addition, post-mortem X-ray tomography and optical microscopy were used to characterise salt-induced crack patterns further. The Flysch rock samples exhibited significant external deterioration, with DIC analysis highlighting the influence of material heterogeneity in damage susceptibility. AE analysis captured internal damage progression and identified the onset of salt-induced deterioration in the Vosges sandstone samples, which displayed consistent responses to the weathering test protocol. The concrete samples, pre-cracked by mechanical loading to mimic on-site coastal erosion conditions, exhibited salt-induced crack propagation and development of new salt-induced cracks when tested under the weathering protocol. These findings demonstrate the protocol’s effectiveness in evaluating salt-induced damage in construction materials, providing a reproducible framework that can be readily implemented in diverse testing environments to enhance durability assessment in engineering applications.

Salt crystallization poses a significant threat to cultural heritage. We focus on understanding salt weathering in antique Dutch tiles, a composite layered material composed of a clay body and a ceramic glaze. Physico-mechanical properties of those tiles were quantified. The role of salt nature and glaze configuration (intact and crazed) in the weathering process were visualized and compared during several wetting-drying cycles by using different techniques such as X-ray tomography, SEM imaging, and confocal profilometry. Physico-mechanical properties are found to be mostly alike for intact and crazed tiles. Both sodium chloride and sodium sulfate contamination lead to the accumulation of salt, but with different accumulation patterns. While sodium chloride precipitation can be found throughout the entire clay body, sodium sulfate precipitation accumulates near the interface between the glaze and the clay body at the corners where the evaporation is the highest. Subsequently, damage in the form of cracks crossing the clay body and the glaze leads to material detachment. Sodium sulfate is particularly damaging during the rewetting cycles prior to drying due to the formation of the hydrated phase mirabilite. Conservation treatments based on the use of liquid water should thus be avoided on sodium sulfate contaminated tiles.

A new free-energy functional is proposed for inhomogeneous associating fluids. The general formulation of Wertheim’s thermodynamic perturbation theory is considered as the starting point of the derivation. We apply the hypotheses of the statistical associating fluid theory in the classical density functional theory (DFT) framework to obtain a tractable expression of the free-energy functional for inhomogeneous associating fluids. Specific weighted functions are introduced in our framework to describe association interactions for a fluid under confinement. These weighted functions have a mathematical structure similar to the weighted densities of the fundamental-measure theory (i.e., they can be expressed as convolution products) such that they can be efficiently evaluated with Fourier transforms in a 3D space. The resulting free-energy functional can be employed to determine the microscopic structure of inhomogeneous associating fluids of arbitrary 3D geometry. The new model is first compared with Monte Carlo simulations and previous versions of DFT for a planar hard wall system in order to check its consistency in a 1D case. As an example of application in a 3D configuration, we then investigate the extreme confinement of an associating hard-sphere fluid inside an anisotropic open cavity with a shape that mimics a simplified model of zeolite. Both the density distribution and the corresponding molecular bonding profile are given, revealing complementary information to understand the structure of the associating fluid inside the cavity network. The impact of the degree of association on the preferential positions of the molecules inside the cavity is investigated as well as the competition between association and steric effect on adsorption.

The need to investigate mineral precipitation in heterogeneous sedimentary rock with complex pore network and mineral composition arises with problems like pore clogging by barite precipitation during sulfate-rich water injection in geological reservoirs, the durability of long term storage of nuclear waste or the damage induced by crystallisation. At the LFCR, we aim to reproduce geological objects in laboratory conditions. In this frame, we built a contra diffusive set up to precipitate a barite front in two sedimentary rock samples, a Lavoux oolitic limestone and a Vosges Sandstone with a fraction of clays. Two reservoirs filled respectively with BaCl2 and Na2SO4 dissolved in milli-Q water are in contact with a porous sample so that the ions diffuse through it. X-ray tomography shows that a barite front is precipitated in both samples at different positions depending on the diffusion of the different ions. SEM/EDS microanalysis on polish sections highlight both the barite front location and its connectivity. In the Lavoux limestone, a connected barite front is present. Fine barite aggregates preferentially precipitate in the smallest pores of the Lavoux sample, whilst the crystals precipitating in large macropores (>20 m) show a preferential orientation. We propose that the Gibbs free energy barrier for barite heterogeneous nucleation in the limestone is lower in contact with micrite in small pores than in contact with euhedral calcite in large pores. Finally, the Gibbs energy barrier for barite homogeneous nucleation in large pores is the highest. In the Vosges sandstone, the barite front is scattered with well-crystallized barite precipitating in large pores, and a more striking thin layer of barite is precipitated in the interfoliar space of chlorite-smectite complex. Consequently, we propose that smectite can concentrate barium by adsorption. Then because sulfate and sodium concentrations increase, ultimately barium is desorbed and barite precipitate.

Buildings close to the sea experience different kinds of decay processes related with the influence of marine aerosol. This sea spray is a chemically complex system formed by inorganic salts (sulfates, nitrates and mainly chlorides) and organic matter, together even with airborne particulate matter from the surrounding environment. Buildings close to the sea, erected using different materials such as bricks, plasters, limestones and sandstones, can experience many kinds of chemical reactions promoted by the impact of this sea spray, which favour the formation of salt crystallizations. In this work, a study of salts crystallizing in different kinds of building materials of a construction close to the Bay of Biscay (Villa Belza, Biarritz, France) has been studied in order to evaluate the state of conservation of the materials under study. The construction materials affected by salts were analyzed by means of X-ray Diffraction (XRD) and μ-Raman spectroscopy (μ-RS) for molecular analyses, Energy dispersive X-ray Fluorescence spectrometry (μ-ED-XRF) for elemental analyses and soluble salts tests by means of ion chromatography. These analyses revealed different levels of chlorides, nitrates and sulfates. Moreover, using this methodology, some specific chemical reactions that take place in the Villa Belza were understood. This knowledge can help to lay the foundations for possible future restoration works.

In this paper, the non-local density functional theory is used in combination with SAFT-VR, to investigate the pore pressure behaviour of water confined in various nanopores. Due to the efficiency and low computational cost of the method, many configurations and thermodynamic conditions are explored. In particular, capillary condensation and evaporation of water, their impact on the pore pressure, and the effect of surface activation are evaluated. Successive first-order phase transitions of ultra-confined water monolayer are also highlighted.

Raman spectroscopy and X-ray fluorescence spectrometry are powerful analytical techniques that allow for molecular and elemental analysis, respectively. Recent developments allowed for the miniaturization of equipment to an extent that in-situ experiments become available. There are many advantages in using portable instruments, but this requires sacrifices regarding the acquisition of the spectra and the quality of the analysis. How much information is lost with this exchange is not clear, neither how important this is for the use of these techniques as forensic tools. In this work, the damage of a façade of Villa Belza, a historic building in Biarritz, France, was evaluated using both portable and benchtop versions of X-ray fluorescence (XRF) and Raman spectroscopy and the approaches were compared. As the comparison of instruments designed for different conditions is not straightforward, the authors use a number of settings to discuss what would be a realistic juxtaposition of results and how this affects the diagnosis of the structure. Furthermore, some hand-held XRF spectrometers are not connected to appropriate software to proceed with the data treatment and the processing of such signals can be tedious or too time consuming. Thus this work also proposes an algorithm for the automatic identification and comparison of elements in the XRF spectra acquired on site. After discussing the trade-off involved with each technique and the respective effect in the limit of detection, the authors conclude that the extra information from benchtop instruments was negligible for this case study.