Decay processes in buildings close to the sea induced by marine aerosol: Salt depositions inside construction materials.

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.

Hopper Growth of Salt Crystals.

The growth of hopper crystals is observed for many substances, but the mechanism of their formation remains ill understood. Here we investigate their growth by performing evaporation experiments on small volumes of salt solutions. We show that sodium chloride crystals that grow very fast from a highly supersaturated solution form a peculiar form of hopper crystal consisting of a series of connected miniature versions of the original cubic crystal.

Comparison between traditional laboratory tests, permeability measurements and CT-based fluid flow modelling for cultural heritage applications.

In this paper, we examine the possibility to use on-site permeability measurements for cultural heritage applications as an alternative for traditional laboratory tests such as determination of the capillary absorption coefficient. These on-site measurements, performed with a portable air permeameter, were correlated with the pore network properties of eight sandstones and one granular limestone that are discussed in this paper. The network properties of the 9 materials tested in this study were obtained from micro-computed tomography (μCT) and compared to measurements and calculations of permeability and the capillary absorption rate of the stones under investigation, in order to find the correlation between pore network characteristics and fluid management characteristics of these sandstones.

Biogenic concrete protection driven by the formate oxidation by Methylocystis parvus OBBP.

The effectiveness of Microbiologically Induced Carbonate Precipitation (MICP) from the formate oxidation by Methylocystis parvus OBBP as an alternative process for concrete protection was investigated. MICP was induced on Autoclaved Aerated Concrete (AAC), the model material, by immersing the material in 10(9) M. parvus cells mL(-1) containing 5 g L(-1) of calcium formate.

Data-fusion of high resolution X-ray CT, SEM and EDS for 3D and pseudo-3D chemical and structural characterization of sandstone.

When dealing with the characterization of the structure and composition of natural stones, problems of representativeness and choice of analysis technique almost always occur. Since feature-sizes are typically spread over the nanometer to centimeter range, there is never one single technique that allows a rapid and complete characterization. Over the last few decades, high resolution X-ray CT (μ-CT) has become an invaluable tool for the 3D characterization of many materials, including natural stones.

A pore-scale study of fracture dynamics in rock using X-ray micro-CT under ambient freeze-thaw cycling.

Freeze-thaw cycling stresses many environments which include porous media such as soil, rock and concrete. Climate change can expose new regions and subject others to a changing freeze-thaw frequency. Therefore, understanding and predicting the effect of freeze-thaw cycles is important in environmental science, the built environment and cultural heritage preservation.

Metastability Limit for the Nucleation of NaCl Crystals in Confinement.

We study the spontaneous nucleation and growth of sodium chloride crystals induced by controlled evaporation in confined geometries (microcapillaries) spanning several orders of magnitude in volume. In all experiments, the nucleation happens reproducibly at a very high supersaturation S ∼ 1.6 and is independent of the size, shape, and surface properties of the microcapillary.