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Deterioration processes of granitic rock (SL) in different climatic environments

Deterioration processes of granitic materials are being studied in a continental climate (the Spanish Plateau), in a humid climate (French Bretagne) and under industrial pollution conditions (Porto Area, Portugal). A few representative monuments from each area are examined together with samples from the quarries from which the building materials originated.

In Bretagne, crystallization of salts and biological degradation are the 2 paramount factors for degradation. A study of the microflora, lichen development, action of nitrifying bacteria and fermenting sugar bacteria are being carried out.

In the Porto zone, the effect of industrial pollution is determined by comparative studies of monument weathering in areas with different climate and atmospheric contamination (Porto and Braga). The work implies rain water causes stone degradation by the dissolution of granite components and salt crystallization.

In Spain, 3 types of granite employed in historical buildings construction have been studied: one typical sain granite, one porous facies with smectite and another silicified granite, rich in opal. The agents responsible for degradation seem to be the strong thermal oscillations in this area, salt crystallization, especially in the lower parts of the buildings and dissolution of opal in areas with mortar influence.

The study of artificial ageing of the different types of granite has been carried out in simulation chambers, under controlled humidity and temperature conditions. The treatment of unaltered and altered materials in chambers is currently done with nidrofugating and consolidating products, determining in each case the changes in the material properties during and after the ageing and/or treatments process.

Reported by

Consejo Superior de Investigaciones Cientificas
Cordel de Merinas 40-52 Apartado 257
37008 Salamanca
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