Length changes of sandstones caused by salt crystallization
Published:January 01, 2007
J. Ruedrich, M. Seidel, E. Rothert, S. Siegesmund, 2007. "Length changes of sandstones caused by salt crystallization", Building Stone Decay: From Diagnosis to Conservation, R. Přikryl, B. J. Smith
Download citation file:
Salt crystallization in the pore spaces of building stones can produce significant deterioration. The properties of the salt solution, the salt phases and the climatic conditions, as well as the rock fabric, significantly influence the state of rock weathering. To examine the influences of rock fabric and salt type on salt weathering, detailed investigations were performed on three sandstones. The fabric (mineralogical composition, grain size, etc.) and the petrophysical properties (porosity, pore-size distribution and hygric dilatation) of the sandstones were analysed and correlated with length changes during cyclic salt loading. The salt tests were carried out with two different salt types: (i) sodium sulphate and (ii) sodium chloride. The observed length changes differ for the investigated sandstones. Contractions of the samples, as well as a pronounced residual strain after the applied salt cycles, were observed. Specific deterioration features can be determined for the sandstones independent from the salt types used. However, the decay mechanisms, which lead to a significant deterioration, are different for sodium sulphate and sodium chloride. For sodium sulphate, a strong expansion occurs during the solution uptake cycles. This expansion can be attributed to hydration pressure during the transition from the water-free thenardite to the hydrate phase mirabilite. In contrast, the samples in the sodium chloride test show the main expansion in the drying stage. This can be related to the crystallization pressure caused by the growth of halite.
Figures & Tables
Building Stone Decay: From Diagnosis to Conservation
Stone buildings and monuments from the cultural centres of many of the world's urban areas. Frequently these areas are prone to high levels of atmospheric pollution that promote a variety of aggressive stone decay processes. Because of this, stone decay is now widely recognized as a severe threat to much of our cultural heritage. If this threat is to be successfully addressed it is essential that the symptoms of decay are clearly identified, that appropriate stone properties are accurately characterized and that decay processes are precisely identified. It is undoubtedly the case that successful conservation has to be underpinned by a comprehensive understanding of the causes of decay and the factors that control them. The accomplishment of these demanding goals requires an interdisciplinary approach based on co-operation between geologists, environmental scientists, chemists, material scientists, civil engineers, restorers and architects. In pursuit of this collaboration, this volume aims to strengthen the knowledge base dealing with the causes, consequences, prevention and solution of stone decay problems.