INSOLATION WEATHERING AND HYGRIC DILATATION: TWO COMPETITIVE FACTORS IN STONE DEGRADATION

Abstract

In the natural environment, temperature and moisture are very important parameters in stone degradation. Therefore, on 28 samples from different lithologies (magmatic, metamorphic and sedimentary rocks) thermal and hygric expansion measurements were performed in order to constrain their behaviour related to environmental changes. It was shown that marbles, even those that are dolomitic, are sensitive to temperature impacts. For rocks with clay minerals the effect of temperature may be responsible for shrinking. Finally the amount of residual strain, i.e. the formation of microcracks due to temperature action controls the rate of stone degradation. For most sedimentary rocks no residual strain after heating was observed. In contrast to most magmatic and metamorphic low-porosity rocks, sedimentary rocks contain swelling minerals (like smectite and even phyllosilicates), which are very sensitive to hygric attacks. The cycles of wetting and drying, i.e. the natural environmental effects, may significantly control the deterioration velocity caused by hygric expansion.