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2006/3/13

Mixed mortars of calcium and cement in the restoration of buildings

The chemist Mikel Arandigoyen Vidaurre, of the Department of Chemistry and Soil Sciences of the University of Navarra, has proved the effectiveness of new formulas for the restoration of buildings. In his thesis, defended at the School of Sciences, he proposes a combination of calcium and cement, which is able to strengthen the qualities of both materials.

The restoration of architectural patrimony currently presents certain problems of compatibility. Cement-based mortar is useful for its quick setting, but it is very aggressive with stone. In addition, it has too much mechanical resistance and a high content of soluble salts, which can cause problems in the medium or long term.

Calcium-based mortar offers less resistance and has a slower setting time. Nevertheless, it has qualities that are better adapted to restoration. This material presents a zone of plastic deformation which permits it to absorb, without breaking, the deformations that are common in monuments.

A new method of tracking

Another difference between the two materials is based on the carbonation (the process which leads to the oxidation of iron). This is a phenomenon which is produced naturally and which provides mechanical resistance to calcium-based mortars, while it limits the useful life of reinforced concrete.

In his research, he has used a new method for tracking this process, by means of the evolution of weight. In function of the material studied, changes are produced at distinct rates and provoke diverse modifications in their microstructure.