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объекты Ростехнадзора
Protection against fragility of concrete and ferro-concrete designs
According to natural inspections, the analysis of design materials and to an expert estimation of experts, aggressive influence are exposed from 15 to 75% of building designs of buildings and constructions not only industrial and agricultural, power and transport objects, but also inhabited and public buildings.       

In 60-80 years the big scientific potential has been saved up, bases of the theory of corrosion of concrete and armature, ways of maintenance of corrosion firmness of ferro-concrete designs in excited environments are developed. And now these workings out widely use in building practice. For last decade the volume of researches in this direction was reduced, but practice demands the operative decision of urgent problems.

Considering the tendency of last years of use in the industry of building materials of production wastes (slags, harms, ash slag mixes, etc.), applications for manufacturing of concrete and ferro-concrete designs cementless knitting and knitting with the lowered maintenance clinker fund, it is necessary to solve questions of durability of these designs even at operation in normal atmospheric conditions.

The problem of economy of metal in building in this connection the tendency of replacement of armature of ferro-concrete designs on armature of class А500С which wide application in building demands studying of its corrosion firmness at influence of excited environments and use of nonconventional building materials is observed is not less important.

One of directions of development and concrete and ferro-concrete perfection is working out of new approaches and their realisation in the industry at reception knitting and the concrete of new generation providing reliability and durability of designs and constructions.

Increase of reliability and corrosion firmness of ferro-concrete designs in excited environments can be reached by creation of corrosion-resistant building materials of new generation with use of economic factory technologies and new kinds rebar the steels of high reliability providing 20-40% economy of metal. Quality and durability of buildings and constructions can be provided by application of corrosion-resistant designs. Creation of such designs demands development of some the important scientific directions.

1. Research of firmness of initial materials for manufacturing of ferro-concrete designs: armatures, steel communications, concrete on new knitting and nonconventional fillers, including with use of a waste of the industry. Follows:
- To study processes of corrosion of new materials in the most widespread excited environments, and also processes of internal corrosion of concrete at use of local raw materials with the raised maintenance of harmful impurity;
- To study processes of destruction of new kinds of armature at simultaneous influence on ferro-concrete designs of various power loadings and an excited environment, to estimate their danger corrosion cracking taking into account characteristics of a periodic profile and manufacturing techniques; to expand scopes of effective kinds of a steel;
- To develop and investigate new sheetings on armature and technology of their drawing; to study new kinds of protective materials for concrete on the basis of domestic raw materials; to develop criteria and methods of an estimation of their durability;
Increase of reliability and corrosion firmness of ferro-concrete designs in excited environments can be reached by creation of corrosion-resistant building materials of new generation with use of economic factory technologies and new kinds rebar the steels of high reliability providing 20-40%-s' economy of metal.
- To continue studying and working out of chemical ways of removal of products of corrosion from a surface of armature and ways of increase of corrosion firmness of concrete at repair of designs;
- To develop measures of maintenance of durability of ferro-concrete designs at simultaneous influence of an excited environment and mechanical loading;
- To develop concrete and ferro-concrete designs of high durability, corrosion firmness and firmness at the biological corrosion, made on economic technologies with use of a waste of the industry and agriculture.

2. Working out of settlement methods of the forecast of durability of the underground and elevated ferro-concrete designs working at influence of liquid and air-gas excited environments.

3. Creation and introduction of a quality monitoring of parametres of quality and durability of building production on manufacturers and their certified certification that allows to make building production competitive.

Result of these researches on a problem “durability” will be:
- Creation of new corrosion-resistant modular and monolithic designs with a guarantee of settlement service life of the basic bearing designs and the increased between-repairs period;
- Development of the theory of corrosion of concrete and ferro-concrete, perfection of norms of designing of designs of the raised durability and corrosion firmness with application of settlement methods of the forecast of durability.

Within the limits of the international organisation SIB RILEM it is developed and the system of designing of buildings and constructions taking into account demanded durability and service conditions operates. One of its important aspects is creation of the standard document defining design service life of a concrete building or a construction (for example, 10, 20, 50, 100 years). Presence of the set term of operation allows soundly to choose materials, products, to appoint primary or secondary protection, the between-repairs period, etc., that is the concept durability gets quantitative settlement value.

Presence of the set term of operation allows soundly to choose materials, products, to appoint primary or secondary protection, the between-repairs period, etc., that is the concept durability gets quantitative settlement value.

The scheme of designing of buildings and constructions on durability
The scheme of designing of buildings and constructions on durability


Observance of the principle resulted on the image of the scheme of designing of buildings and constructions on durability, will allow to avoid premature failure of designs, and, hence, to increase the between-repairs period, and in certain cases to provide maintenance-free operation of designs for all settlement term “lives” buildings or constructions.

Until recently in our country there was a system of designing of buildings and constructions, a choice of kinds of primary or their secondary protection under operating conditions designs taking into account properties of building materials and products; its requirements are stated in building norms and rules 2.03.11-85 and the management to it. Unfortunately, many of them are not considered neither at new building, nor at reconstruction or a reshaping of buildings. Quite often at designing, building and operation requirements of maintenance of durability are not observed.

The especially sharply above-named problems are shown at operation of engineering constructions: bridges and overpasses; underground pedestrian crossings and transitions over tracks; road coverings; municipal tunnels and channels; collectors of sewage; tunnels through passage with lines of an electrical supply, communication, networks of cold and hot water supply; channels of pipelines of hot water and steam; underground constructions of type of cellars; base designs, etc.

In overwhelming majority of cases principal causes of their damages – the corrosion processes developing as a result of adverse influence of environment. So, overpasses and city bridges, road coverings collapse from application opposite bare glacial reagents, allocation in atmosphere oxides nitrogen, sulphur and other gases which are thrown out by engines of motor transport, the industrial enterprises, from concrete defrosting. Emergency collapses of municipal tunnels, especially collectors of sewage, occur, first of all, as a result of gas corrosion of metal and ferro-concrete elements.

Recently defeat of designs mold mushrooms has extended that, according to health officers and ecologists, adversely affects on health of the person, especially children. Many problems deliver to builders efflorescence on brick and concrete designs of inhabited and civil buildings and constructions. Similar examples, unfortunately, it is possible to result much.

Today repair-regenerative and civil work are frequently carried out by the experts who are not owning necessary knowledge in the field of corrosion and protection against corrosion of building materials and designs. Result is destruction of products at times in one winter, and sometimes even before building delivery in operation. The reasons of it, as a rule, – bad quality of the concrete, incorrectly chosen combination knitting and a filler, use of the polluted, is reactionary-capable fillers and cements with the raised maintenance of the alkalis, the raised maintenance of water in concrete mixes, low frost resistance, high water absorption of concrete, etc. Anticorrosive services thus stay idle, and the system of an estimation of operational suitability of building designs in the conditions of operating manufactures is not ordered.

Durability problems are especially sharp at building in northern areas. The permafrost, low temperature, repeated freezing and thawing of concrete of designs promote fast destruction of ferro-concrete.

Requirements of reduction of weight of buildings, industriality installation, to architectural expressiveness naturally let pass to new kinds of designs. However with reduction of a thickness building designs become even more vulnerable for corrosion. Operational services are late with performance of preventive inspections of an estimation of a condition of designs both their timely repair and restoration. There can come time when owing to continuous destructions and failures the considerable part of a fixed capital of our country will fail.

Thus, it is necessary to note the actions necessary for a raising of quality of products and increase of durability of building designs, not demanding the big material inputs. Production estimation necessarily should be made taking into account parametres of quality and durability, its conformity to standards., First of all, with operation excited environments, and also at use of nonconventional materials in manufacture of building designs, it is necessary to carry out carrying out of examination of design decisions of ferro-concrete designs of buildings and constructions in common with the experts who are responsible for the given problem.

Considering reduction of building of the new industrial enterprises, the growing volume of a reshaping of the enterprises and reconstruction of buildings and constructions and repair accompanying it, it is necessary to estimate a condition of designs taking into account changing conditions of their operation, residual bearing ability of designs.

The scheme of an estimation of durability of a building at repair or reconstruction
The scheme of an estimation of durability of a building at repair or reconstruction


To provide durability of buildings and constructions without the big expenses it is possible if to put a durability problem in a rank basic at designing, calculation, manufacturing and operation of building designs. All is together taken will allow to reduce expenses in building branch, and unreasonable expenses on liquidation of corrosion losses to direct on development of a branch building science and its equipment by the modern equipment.


Sources:
1. Shestakov E. Ensure durability of concrete and ferro-concrete designs – a basis of preservation of a fixed capital of the country [http://kirovka.ru/realty/?parentid=41&article=499]
2. Zvezdov A.I. Concrete shrinkage-compensated for the erection of crack resistant design of long [http://www.hydrobeton.ru/?id=5&select=3&tid=2]

The author: Челябэнергопроект
Date: 07/22/2009

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