Construction stones - Nature and alteration mechanisms

It's written in stone... This expression alone expresses the extent to which, in the imagination, stone is a durable material par excellence. Its hardness and resistance give writings, laws and human thoughts the little piece of eternity they need. Stone is certainly a durable material. Paradoxically, stone is not supplied by nature. It is extracted and shaped from rock by human hands.

Extracting rock from its original environment subjects it to general decompression, a change in humidity, temperature and chemical equilibrium. As a result, the stone material undergoes a structural change, sometimes impossible to detect with the naked eye, which makes it more fragile. Secondly, the shaping of stone multiplies its surface contact with external agents, which contributes to accelerating its evolution.

Finally, the use of stone in buildings subjects it to new stresses and exposures. Blocks are subjected to new mechanical pressures and atmospheric erosion agents: rain, wind, temperature variations, frost, chemical pollution, micro-organisms...

At its interface with its environment, stone undergoes a number of physico-chemical reactions that alter its appearance, its surface and then its very structure, ultimately jeopardizing the entire structure. The deterioration of materials and the gradual destruction of structures are inevitable. Far from affecting only stone, this deterioration affects all building materials. Given these destructive processes, the development and application of materials are guided by the search for functional properties and performance. But beyond these qualities, it is necessary to ensure the durability of materials in their intended use. This means studying the evolution of their properties under the combined effects of the physical and chemical characteristics of their environment.

After a brief study of the various rocks used in construction and their different fields of application, this dossier will detail the weathering phenomena that affect stone in use.

It should be noted that the document [COR 404] "Building stones – Use, studies and diagnostics" is a useful complement to this article.