Bacterial spores respond to humidity similarly to hydrogels.

Bacterial spores have outstanding properties from the materials science perspective, which allow them to survive extreme environmental conditions. Recent work by [S. G.

Durable Self-Cleaning Coatings for Architectural Surfaces by Incorporation of TiO₂ Nano-Particles into Hydroxyapatite Films.

To prevent soiling of marble exposed outdoors, the use of TiO₂ nano-particles has been proposed in the literature by two main routes, both raising durability issues: (i) direct application to marble surface, with the risk of particle leaching by rainfall; (ii) particle incorporation into inorganic or organic coatings, with the risk of organic coating degradation catalyzed by TiO₂ photoactivity. Here, we investigated the combination of nano-TiO₂ and hydroxyapatite (HAP), previously developed for marble protection against dissolution in rain and mechanical consolidation. HAP-TiO₂ combination was investigated by two routes: (i) sequential application of HAP followed by nano-TiO₂ ("H+T"); (ii) simultaneous application by introducing nano-TiO₂ into the phosphate solution used to form HAP ("HT").

An Ideal Solid Solution Model for C-S-H.

A model for an ideal solid solution, developed by Nourtier-Mazauric et al. [Oil & Gas Sci. Tech.

Thermo-Mechanical Compatibility of Viscoelastic Mortars for Stone Repair.

The magnitude of the thermal stresses that originate in an acrylic-based repair material used for the reprofiling of natural sandstone is analyzed. This kind of artificial stone was developed in the late 1970s for its peculiar property of reversibility in an organic solvent. However, it displays a high thermal expansion coefficient, which can be a matter of concern for the durability either of the repair or of the underlying original stone.

Nucleation, growth and evolution of calcium phosphate films on calcite.

Marble, a stone composed of the mineral calcite, is subject to chemically induced weathering in nature due to its relatively high dissolution rate in acid rain. To protect monuments and sculpture from corrosion, we are investigating the application of thin layers of hydroxyapatite (HAP) onto marble. The motivation for using HAP is its low dissolution rate and crystal and lattice compatibility with calcite.

Chemo-mechanics of salt damage in stone.

Many porous materials are damaged by pressure exerted by salt crystals growing in their pores. This is a serious issue in conservation science, geomorphology, geotechnical engineering and concrete materials science. In all cases, a central question is whether crystallization pressure will cause damage.

Advances in understanding damage by salt crystallization.

The single most important cause of the deterioration of monuments in the Mediterranean basin, and elsewhere around the world, is the crystallization of salt within the pores of the stone. Considerable advances have been made in recent years in elucidating the fundamental mechanisms responsible for salt damage. As a result, new methods of treatment are being proposed that offer the possibility of attacking the cause of the problem, rather than simply treating the symptoms.

Transport of water in small pores.

Experimental measurements of the thermal expansion coefficient (alpha), permeability (k), and diffusivity (D) of water and 1 M solutions of NaCl and CaCl(2) are interpreted with the aid of molecular dynamics (MD) simulations of water in a 3 nm gap between glass plates. MD shows that there is a layer approximately 6 A thick near the glass surface that has alpha approximately 2.3 times higher and D about an order of magnitude lower than bulk water.

Thermal expansion of confined water.

Dilatometric measurement of the thermal expansion of water in porous silica shows that the expansion coefficient increases systematically as the pore size decreases below about 15 nm. This behavior is quantitatively reproduced by molecular dynamics (MD) simulations based on a new dissociative potential. According to MD, the structure of the water is modified within approximately 6 A of the pore wall, so that it resembles bulk water at a higher pressure.

Molecular mechanisms causing anomalously high thermal expansion of nanoconfined water.

Anomalously high thermal expansion is measured in water confined in nanoscale pores in amorphous silica and the molecular mechanisms are identified by molecular dynamics (MD) simulations using an accurate dissociative water potential. The experimentally measured coefficient of thermal expansion (CTE) of nanoconfined water increases as pore dimension decreases. The simulations match this behavior for water confined in 30 A and 70 A pores in silica.

Dangling bond deflection model: growth of gel network with loop structure.

It has been shown that the closed-loop structure in the model gel networks is responsible for their stiffness. However, the creation of loops has been underestimated in most of the existing kinetic aggregation models [e.g.