The crystallization process of soluble salts inside the natural and artificial porous materials partially immersed in different saline solutions has been studied, This procedure is used to simulate the conditions of exposure to salt weathering in which foundations and lower walls of building structures are within the zone of capillary rise of saline ground water.Crystallization pressures that can develop in the samples, which are a function of the pore size and salt-solution interfacial tension, have been calculated and are compared with experimental values of the materials tensile strength. since both these parameters allow the prediction of porous materials behaviour against salt weathering.

Blends of poly(ethylene terephthalate) (PET) and high-density polyethylene (HDPE) with and without a compatibilizing agent were studied. Both materials are widely used in the soft drink bottle industry. The compatibilizing agent was a copolymer of ethylene and methacrylic acid partially neutralized with zinc (Surlyn). The olefinic segment of Surlyn is compatible with HDPE, whereas the Surlyn carboxylic acid groups is affine with the PET carbonyl groups. The effectiveness of the compatibilizing agent was evaluated using different techniques, such as infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and mechanical properties.

In order to study the processes of salt weathering of monumental stones, several samples were partially immersed in sodium, potassium and magnesium sulphate solutions which ascended through their capillary network and, eventually, crystallized. This procedure pretends to simulate the conditions in which foundations and lower walls of building structures are, within the zone of capillary rise of saline groundwater. Mass transport and the rhythmic nature of crystallization fronts inside samples reminds the Liesegang phenomenon, so they have been considered as a form of dissipative structures. The saline deposits developed on the surface of the samples were effiorescences (mirabilite and epsomite), subeffiorescences (picromerite, aphthitalite and arcanite) and crusts (aphthitalite and arcanite). The most devastating effects resulted from massive crystallization inside the samples or from surface peeling due to the develop ment of subeffiorescences or crusts.

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