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Strukturalne wzmacnianie wapienia pińczowskiego

100%

Dobrowolski W., Sobkowiak D.

Ochrona Zabytków

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1976

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issue 2

75-83

EN

The aim of the research was to examine the possibilities and ways of application of S. Z. Lewin’s method in limestone reinforcement. The method constists in limestone impregnation with the solution of carbamide and barium hydroxide. As a result of the chemical reaction in limestone pores the insoluble barium carbonate is precipitated; it is to play the function of the reinforcement. ' At the first stage of the research work the experiments, as described by S. Z. Lewin, were carried out. They dealt with the cementation of powdered chalk in reinforcing solution. Results of these experiments, however, proved to be a failure: after the six-month period of impregnation the cementation of limestone powder did not occur. The second stage consisted in extending the scope of the research. It included the influence of temperature and duration upon the processes of barium carbonate precipitation and limestone powder cementation as well as the effects of the duration of impregnating solution action on mechanical and physical properties of limestone. Moreover, derivatographic and X-ray structural analyses of impregnated limestone were made. As a consequence of the above experiments it was stated that the efficiency of the process of barium carbonate precipitation in room temperature was very small ((about 26 per cent after 30 days). It increases proportionally to the growth of temperature, being sufficient at 95°C. The increase of limestone strength was not stated on the grounds of influence of duration of the solution action (up to 3 months) in room temperature. Absorbing and capillary capacities of limestone, however, decreased and this proved the partial seal of limestone pores caused by barium carbonate. The application of barium hydroxide solution (free of carbamide) brought similar results. In the latter case the chemical reaction of barium hydroxide with calcium carbonate took place. The above-mentioned results were confirmed by X-ray structural investigations. It should be stressed that the cementation of limestone powder and chalk did not occur although hardening solutions of raised temperature (up to 95°C) were being used. Because of negative results of the tests carried out we cannot apply S. Z. Lewin’s method in limestone hardening. This method seems to be sufficient only for protecting the stone against the destructive components of atmosphere (chiefly S 0 2). There are two possible explanations of this situation: in his publications S. Z. Lewin did not make the conditions of limestone hardening clear enough or he might have used some additional substances which caused crystalline barium carbonate to emerge. Crystalline barium carbonate is capable of making crystalline concretions with calcite. In this case both the cementation of limestone powder and thereby reinforcing of limestone should occur.

2

Strukturalne wzmacnianie wapienia pińczowskiego polimetakrylanem butylu

88%

Domasłowski W.

Ochrona Zabytków

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1976

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issue 4

285-294

EN

Research aimed at elucidating the causes of m igrations of thermoplastic resins — employed as solutions for reinforcement of porous stones — has been taken up. Solutions of butyl polymethacrylate have been used for the purpose, the limestone from the region of Pińczów being saturated with them in the tests concerned. The impact exerted by the degree of polymerization of resins, solvents and concentration on capillary ascent o f solutions, the degree of saturation of the stcnes, their drying capacity and finally on the process of migration of resins in the course of drying has been studied. The results of the investigations have made it possible to determine the paramétrés chesking the process o f migration of butyl polymethacrylate to the surface of Pińczów limestone. As has been ascertained, the main cause deciding about the course of migration is viscosity of solutions. Its degree may be adjusted by way of employing polymers with a higher degree of polymerization or by enhancing concentration of the solutions. The first route has been recognized as more efefctive since it provides for multiple repetition of the proceeding by means of diluted solutions what is of great significance from the viewpoint of conservation practice. Now as regards the solvents used, the best results have been obtained in the case of white spirit. Due to the specific phenomena accompanying its evaporation, solutions with a low degree of viscosity may be applied and the effect of structural reinforcement duly achieved. If aromatic hydrocarbons used as solvents, the viscosity of the solutions should amount to 10+15 cP. On the grounds of the results obtained an attempt has been made at elucidation of the phenomena of migration what enables selection of adequate paramétrés providing for structural reinforcement of the monuments built, or made, of porous materials.

3

Właściwości wapienia pińczowskiego wzmocnionego metodą "stabilnej krzemionki"

75%

Mirowski R.

Ochrona Zabytków

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1981

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issue 3-4

172-180

EN

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.

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3 Ochrona Zabytków

1 1981

2 1976

1 Dobrowolski W.

1 Domasłowski W.

1 Mirowski R.

1 Sobkowiak D.

Strukturalne wzmacnianie wapienia pińczowskiego

Strukturalne wzmacnianie wapienia pińczowskiego polimetakrylanem butylu

Właściwości wapienia pińczowskiego wzmocnionego metodą "stabilnej krzemionki"