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ON THE ISSUE OF THE EFFECTIVENESS OF THE USE OF GYPSUM SYSTEMS DURING RESTORATION WORK
The construction industry is developing every year. New production methods and technologies are emerging, new building materials are being developed and existing ones are being improved. One of the directions of the construction industry is the restoration of architectural monuments. There are many types of restoration mixtures, but the key difference between them is the binder on the basis of which the mixture is made. In this regard, the topic of the article is the question of what types of gypsum mixtures are used during restoration work and how effective they are.
Keywords: gypsum; dry mix; restoration; additives.
Currently, more and more attention is being paid to the restoration of cultural heritage sites, including buildings and structures. Therefore, an important task in conditions of restrictions is the development of the production of gypsum materials for repair and restoration work in order to preserve all decorative elements made of gypsum.
In the process of restoring architectural monuments, the historical values that existed in the buildings throughout their existence are preserved, despite the repairs and alterations carried out. For this purpose, a system of research, selection of materials and their combination is used, taking into account their properties. It is also important to justify the design decisions made and monitor the restoration process.
In recent years, an important task of the domestic industry has been the development and increase in the production of effective building materials based on gypsum binders for finishing, repair and restoration work. Many architectural elements inside the architectural monuments were made of gypsum materials, which have sufficient strength and aesthetic appeal, and are also an economically advantageous choice.
Materials for restoration must provide:
- high quality of work performed, durability during use and be environmentally friendly.
- they should not harm humans and the environment, as well as help reduce the average density, material consumption and cost of restoration work.
- have refractory properties;
- guarantee the cleanliness and attractiveness of the appearance.
Gypsum materials meet the above requirements. The presence of large reserves of natural gypsum and waste containing gypsum also plays an important role. At the same time, the production of gypsum binders is a fairly simple and low-energy process, that is, it requires low fuel and electricity costs. Therefore, gypsum can be considered an environmentally friendly material.
The strength and durability of gypsum stucco depends primarily on the chemical composition of the mixture used, which differs from the composition used in the past. In addition, the finished gypsum composition can be painted or treated with special strengthening agents. However, due to the effects of adverse factors such as high humidity, temperature fluctuations and vibrations, even the most durable stucco can collapse. When restoring, it is necessary to take into account the composition, quality and type of gypsum decoration.
In this regard, the development of modern building materials science is aimed at developing new and optimizing existing compositions based on building gypsum.
Bazhenov P.I., Meshcheryakov Yu.G. and other authors, together with S.V. Fedorov, studied the optimal compositions of self-hardening gypsum mixtures and worked to increase the water resistance of these systems. They also investigated the effect of amorphous silica, quartz and industrial waste on the technical characteristics of gypsum materials.
Bazhenov Yu.M. and his students achieved an improvement in the properties of gypsum stone by using a superplasticizer. In [1, 2] Volzhensky A.V., Ferronskaya A.V., Bazhenov Yu.M., Korovyakov V.F. and other authors studied the use of waterproof gypsum binders, including phosphogypsum, for GCP binders and expanded clay concrete, as well as to increase the durability and operational resistance of light concretes and their properties with by adding chemical additives .
Buryanov A.F. investigated the history of the use of gypsum from P.P. Budnikov to the present and proposed a technological line for the production of gypsum partitions. Together with co-authors V.B. Petropavlovsk, T.B. Novichenkova, V.V. Belov, A.F. Buryanov, A.P. Pustovgar, P.G. Vasilik, they developed low-energy gypsum materials and products, including hardening crystallization systems based on two-water gypsum, and also dealt with theoretical issues using industrial waste .
In their works  Yakovlev G.I., Pervushin G.N., Machyulaitis R., Fisher H.B., Buryanov A.F., Pustovgar A.P., Gordina A.F., Kerene Ya. and other researchers conducted extensive studies of aerated concrete, gypsum stone and other products based on anhydrite and gypsum systems modified with carbon nanostructures and nanodisperse modifying additives. They studied the effect of technogenic dispersed waste and complex modifiers on the structure and properties of gypsum compositions.
In his works, T.E. Khaev developed compositions and technological solutions for obtaining technically effective gypsum materials for restoration work [6, 7].
In their works  Meshcheryakov Yu.G., Fedorov S.V., Krivenko V.V., Buryanov A.F., Ovchinninsky D.V., Weinstein M.M. and others investigated the composition and properties of artificial marble. They have developed various formulations, including those based on polymer and mineral dyes. In ancient times, artificial marble was used for plastering large surfaces, while it did not have seams, as when using natural marble. Among the most common types of artificial marble were oselkovy and iron. With the ironing method, the surface was covered with a layer of wax and ironed with hot irons to give shine and protect against moisture. In the settlement method, grinding and polishing tools were used. Visually, artificial and natural marbles are difficult to distinguish from each other.
Moreva I.V. developed a number of methods for modifying low-grade gypsum binders and their components, which were the basis for designing rational compositions of gypsum compositions for various purposes and optimizing the technological parameters of their production.
In addition, there are many patents that provide ways to modify a gypsum mixture to improve its properties.
In the patent  a formulation of a gypsum mixture is proposed, including a binder based on semi-aqueous gypsum and hollow microspheres, characterized in that it contains hollow microspheres having a compressive strength equal to or higher than the strength of the gypsum binder.
In the patent  it is proposed to make a gypsum mixture of a binder based on semi-aqueous gypsum and hollow microspheres, and also contains hollow microspheres having a compressive strength equal to or higher than the strength of the binder, with the following content, wt.%: binder based on semi-aqueous gypsum 40-90, hollow microspheres 10-60, mixing water - until a test of the required density is obtained.
Thus, the article provides a review and scientific and technical analysis of the use of gypsum materials in the repair and restoration of architectural monuments. Methods have been identified to reduce the density of gypsum materials by using sawdust, foam glass granules from diatomite raw materials and other modifiers.
- Bazhenov Yu.M., Rozhkova K.N., Daeva V.A. Improving the properties of gypsum with the addition of a superplasticizer // Building materials. - 1979. -No. 11.-pp.19-21
- Volzhensky A.V., Stambulko V.I., Korovyakov V.F. GTSP binders based on phosphogypsum / Modern gypsum-containing materials and products. Riga: LatINTI. – 1977.- pp.49-50
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- Krivenko V.V., Ovchinninsky D.V., Weinstein M.M., Buryanov A.F., Goncharov Yu.A. Calcareous marble: ancient traditions and modern technologies // Building materials. - 2008. - No. 8. - pp.16-18.
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- Pat. RU 2 476 402 C2 GYPSUM MIXTURE. Pribytkov Evgenij Anatol'evich (RU) Application: 2011108190/03, 2011.03.02
- US Patent In 3838998, cl. 65-21, 1974.