Właściwości wapienia pińczowskiego wzmocnionego metodą "stabilnej krzemionki"

For some time conservators have been propagating a new method of reinforcing historic stone objects by means of the so-called stable silica. According to the explanations of the author (Dr Bąkowski) the method consists in the saturation of the stone with water glass and with the addition of special catalysts which bring about a production of insoluble crystal silica in pores. This transformation exerts a major effect upon a mechanical strength and resistance to aging. In order to evaluate the proposed method objectively the reinforced samples have been studied in detail. During laboratory testings the following determinations have been made: the content of reinforcing substances and their distribution in the structure of samples, ability of capillary drawing-up of water and water absorption, mechanical strength, content of soluble salts in water and their ability to produce efflorescences and bring about a sample destruction. Studies have been made to examine resistance to frost. Additionally, crystal mircrostructures in reinforced limestone have also been investigated. The results of the studies made have shown : — only a slight increase in the sample mass as a result of the reinforcing (3.7% rise), — considerable sealing of surface pores, — a lower water absorption (by 25—30%). It should be pointed out that this kind of increased resistance might also be obtained by saturating the samples with water glass without catalysts. A slight effect of desalting and long drying-up upon a mechanical strength has also been noted. The examination of the distribution of a reinforcing substance in the structure of the samples has shown that it is uneven, mainly in the zone close to the surface. The content of soluble salts in water is considerable and came to 1.96 per cent. This quantity was made of sulphates, chlorides, nitrates and sodium carbonates. Of interest is the fact that the quantities were found out after a two-stage desalting done by the author of the proposed method. The studies made show that strengthening substances found in the examined samples consist of amorphous Si02, silicates and an unidentified crystal phase with a reflex of 4,46A. On the basis of the studies carried out it may be staled that the method proposed has not shown the advantages ascribed to it and so cannot be employed in practice in the conservation of stone historic objects.