Natural stone in the exterior cladding of buildings and structures
High decorative qualities of natural stone, its ability to withstand long-term negative effects of the environment put him out of competition compared with other facing materials. Using stone materials for exterior cladding in architectural history of our country can be seen in buildings of Moscow and St. Petersburg, are the main centers of civil engineering in Russia.
Since the last quarter of the XVIII century and before the beginning of the First World War the focus of consumer facing stone was Petersburg. There used local platy limestone (Pudozhsky, Putilov, Volkhov and Tosnensky) Revelsky marble, granite from the Finland coast and Lake Ladoga, Estonian marbled limestone, colored German and Polish sandstones. Granite and local limestone used for the construction and cladding caps and stylobates large public buildings (the Academy of Fine Arts, the Academy of Science, Engineering Castle, the Main Staff, the Admiralty, the Kazan Cathedral, and so on. D.). Last quarter of the XVIII century it was initiated by the enormous town-planning value of the work facing granite embankments of the Neva and the walls of the fortress. At the same time the Marble Palace was built. One of the most prominent stone buildings of St. Petersburg in the first half of the XIX. - St. Isaac's Cathedral, where the lining of the stylobate and facilities 116 columns in large numbers was used polished granite. The walls of the cathedral dressed marble Ruskealskogo field. Granite lined most of the bridges over the Neva River in St. Petersburg. With the development of rail transport stone in the late XIX and early XX century increased use of imported decorative stone. In the short time (1896-1914) In St. Petersburg, built about 200 buildings where the facades used natural stone and there have been continuous facade of five-seven-storey buildings, mainly banks and public.
In Moscow before the end of the XIX century in the construction of the Moscow region was used only local white limestone and gray sandstones. Only with the development of railway transport stone in the late XIX century, here were imported Finnish granite and sandstone Polish. Since 1912 began to be used Shishimskogo marble deposits, which faced facade Museum of Fine Arts named after AS Pushkin. Since the 30s of this century, Moscow became the leading consumer facing stone.
During these years, imported marble from the Urals and Georgian fields and granite of Ukrainian field lined with numerous administrative, educational and residential buildings, bridges and embankments of the Moskva river, subway stations and other facilities. Laconic modern architectural forms, detailing restraint have led to the fact that the main element of the lining of steel flat plate, the mass production of which can be adjusted at high automated production lines, allowing the wide use of decorative tiles made of natural stone in modern architecture.
Facing stone plays an important role in the architectural composition of buildings. Standardisation, unification, typing - the main directions of modern architecture and construction practice, in some cases conflict with the desire of architects to create a unique, memorable image of buildings. Facing natural stone to a certain extent contribute to the individualization of the building were constructed from standard elements, due to the uniqueness of colors and textures of various types of stone from different fields.
Selection of types of stone for cladding and decorative works, surface textures and sizes facing products primarily determined by the composition of architectural structures. Centuries of experience architects has revealed certain principles of selection of rock and its treatment. These principles are derived from the architectonic structure, the material conditions of work in the various elements of buildings, structures and conditions of perception reasons of economy.
When selecting types of stone, the relevant architectonic structures, take into account the possibility of artistic expression in the lining of the various structural parts of the building. During Renaissance time, the most perfectly developed methods of selecting the stone and its invoices in accordance with the architectonic bearing wall. The wall was vertical divided on tiers. Facing lower tier expressed greater loading of this part of the wall, so the lining of the lower floors and caps used the strongest rocks - granite, diorite, gabbro, labradorite, and so on. N., And gave them the invoice chipping, while the upper floors stones less stable rocks - limestone, sandstone, dolomite, marble, giving them a more delicate texture, or plastered.
Currently, the selection principle remains the same breed stone wall when carrying and carried elements of buildings. Plinths, columns and stylobates veneer stronger species than the walls. But tectonics modern frame buildings, where curtain walls are similar burden in all parts of plants, determines otherwise than in the Renaissance, the expression of the work in its wall lining. The outer wall plane in modern buildings made uniform regardless of whether the wall is hung on the frame or based on the edge beam. Large undivided plane walls require a lot of homogeneous cladding material. Therefore, at present in the construction of our preference for relatively inexpensive types of stone: travertine, tuff, limestone, dolomite and white marble. Application labradorite, gabbro, and other expensive and durable species declined significantly compared with the construction in the previous periods. In construction there are examples abroad facing facades of large buildings completely with precious stones (building of the Ford Foundation in New York City, the building of the Supreme Court, in Tokyo, and others.).
The color and texture of various types of stone influence the perception of architectural structures. Buildings of the dark gabbro, granite, diorite and other similar breeds look the most monumental, sometimes even gloomy and inaccessible compared to structures of light limestone and travertine marble. Bright polished marble, translucent at the corners and fine details, could create the impression of lightness and airiness even, transparent structures, walls on a sunny day literally dissolve against the sky. Fine combination of rocks of different colors gives the building solemnity and elegance. This is a combination of different colors of marble panels on the facade of Florence Cathedral. Huge thanks to this building do not suppress their mass surrounding buildings. They are quite commensurate with the scale of the city. Only in the inner spaces of the buildings and the skyline of the city revealed its enormous size. The rich range of colors creates the impression of facing medley. The division in the form of individual panels, panels and tiers does not violate its unity.
In facing the Doge's Palace in Venice combines pink and white marble, forming on a blank stone wall geometry pattern, giving the architecture of the palace conviviality and ease. Selection of types of stone and color combinations can carry some meaning in the composition. So, a combination of light gray dolomite and black diabase, in the facing of the facades of the Leningradskogo crematorium mourning emphasizes the purpose of the structure. The facing of the Armenian brown-purple tuff of the Moscow theater "Yerevan" and colored marble Uzbek shop "Uzbekistan" in Donetsk indicates the desire to emphasize the architecture of these buildings is a national trend. The use of natural stone color allows you to create monochrome and polychrome architectural compositions. An example is a polychrome composition ST. Mark's in Venice. It used a variety of marble - white, black Egyptian, Verona red, gray Carrara, Spanish marble with yellow and brownish spots on blue-gray background, Phrygian white marble with purple and black veins; Istra yellowish limestone, red porphyry from Egypt, dark green porphyry; red, black and gray granite, breccias, and etc. There are about 50 varieties of stone from Egypt, Asia Minor, the islands of the Greek archipelago, Greece, Rome, Sicily, Spain and North Africa in this building.
Modern polychrome stone composition is much easier. Usually combinations include two or three colors and no more: the building of the French Embassy in Moscow used: red-orange tuff, white marble and black gabbro; in the embassy building in Moscow, Poland - white marble and gray-green syenite; on the facades of children's music school in Yerevan tuff used three colors.
In modern architecture often used monochrome compositions, where large undivided walls veneer same plane on the color of the stone. It requires a rigorous approach to the selection of tiles for uniformity of color and tone. Wilderness areas enclosing walls, tiled stone different in tone, overhanging tape glazing creates an unpleasant impression of masonry, hanging in the air (chess club in Yerevan). The administrative building, built by the project architect J. Pickard, the horizontal panel lined with colored marble with a pronounced texture, revealing a stone rock in Madrid. Panels of variegated marble tiles get pressure as a stone subconsciously always associated with weight. For horizontal hinged panels more logical use of flat tone linings.
For vertical panels of tiles tone selection may be less severe, but even here the uniformity of tone is preferred, since it emphasizes the solidity, massiveness of the building (the station in Vladimir, Institute of the Far East in Moscow).
Color combinations of stone veneers can be used to contrast the opposition and carried by the load-bearing elements of the building, when the last trim darker stone, for example, exposed columns of the first floor or con solo made by beams on which rest the overlying structure.
There are purely decorative techniques and combinations of color stone facings. For example, finishing large surfaces of external walls of the Museum of Art in Cleveland United States is an alternation of narrow horizontal strips of light and dark granite.
An important role in the composition plays impressive stonework. It enriches the plastic construction, causing light and shade, emphasizes the individual elements of the composition. Selection of surface texture is determined by how the element is treated stones - monolithic or dismembered. Invoices with a smooth topography can create a monolithic undifferentiated plane. Rough-fluted invoice always reveal the addition of the walls of the individual blocks. Architectural interpretation of facing a rough texture gives the impression of massive masonry, though constructive - it's just a waybill decorative layer. Using this texture, some architects would like to protest against the excessive utilitarianism preceding period architectural 60 get into another excess - architecture get emphasize on expressive nature. Buildings get closed volumes with small window openings, the surface of the walls - deliberately rough treatment. That is the Supreme Court building in Tokyo - a dull, almost without openings, lined with horizontal stripes of light granite with rough-crushed texture. Medieval dungeon architecture resembles the city hall in Tokyo. Volumes have its curved surface, a few windows in the form of narrow loopholes. A three-storey stylobate buildings, lined with red granite rusticated tiles, similar in size brick. The main entrance is designed as a high arch, a staircase leading to the lobby, starts right from the entrance arch, exterior doors and there are no people directly from the street enters the interior of the grand lobby, which has a medieval architecture is characteristic room with high arched windows stretching , the floor made of red granite, the walls are made of polished black granite, aluminum ribs reinforce the impression of the arch. The entrance to the basement garage is made in the form of an arch, only to have a shallow form. The thickness of the stone walls of windows framing emphasizes decision-loopholes and depth of the niche at the entrance, which has a small sculpture. The architecture of the building is grim, closed, but a very interesting interpretation of the stone building.
In modern Japanese architecture is also used coarse texture of the wall, resulting in the lining of her ragged chunks of stone, gravel and pebbles. Interesting for architects - historical-ethnographic museum in Takamattsu (architect T. Yamamoto). This is a complex composition, which serve as the basis for several deaf volume having the shape of a truncated pyramid. These volumes, lined with ragged, rough stones of small size, combined with the lower horizontal volume, made of concrete and glass. The whole composition is located on the top of a small cliff, which overlooks the bay. Relief of the rocks left almost untouched and organically merges with the buildings, retaining walls and steps smashed into the rock. The picturesque composition seems to be an organic element of the surrounding mountain landscape, rough-fluted stone texture of architectural volumes makes them a natural extension of the natural landforms.
If monolithic on architectural interpretation of the walls is used, as a rule, a single invoice processing throughout the plane, the tectonics of the wall with horizontal articulation of the plane determines the use of the lower parts of its rougher texture to identify the load or, on the contrary, the most subtle texture if the base is treated as a monolith the more that the fine texture allows for more decorative features reveal stone - its color and texture, the most accessible spectator in the lower parts of the building.
A variety of textures of the material contributes to a different perception and evaluation of the various parts of the building and the whole composition in general. Thus, a rough rustication stone facing slabs of the lower floors of the Renaissance Italian palazzo reinforces the impression of significance, inaccessibility, the massiveness of the buildings.
Sizes of tiles influence on the composition. The thickness and jointing method are selected in accordance with the invoice processing boards. For rough-fluted invoices are selected and wider seams that often emphasize the special treatment of contour plates. With mirror polished textures and seams are made minimal (up to 4 mm) to create the impression of solidity lined the walls. Plates from an artificial marble having a pattern such as breccia, can be separated from each other sufficiently large joints, which are filled with colored cement applied under the basic tone of rock or stone with cement and rock dust.
For more revealing seams in the lining of the building used a special treatment of the mating faces of the stone. With careful fitting stone squares together to process them frame. A thinner edging stone compared to the rough treatment of the facial field stone allows you to clearly read the size of the squares. It is also used rusticated treatment of joints, having a variety of configurations: rectangular, round, prismatic, grooved, chamfered. Rust can be performed at a sufficient thickness of the facing plates. Therefore rusticated pair typically used for plates big-hilly or having the texture of rock, but can be used for other invoices, except for polished, mirror-polished and for which it is not typical. Rustic surface creates a sense of a massive wall. Various configurations and create a certain depth Rust plastic surface, enhance the game of light and shade.
Using the methods of jointing, the combination of various sizes and textures of tiles and the method of their clutches, architects can achieve varying degrees of intensity of the feeling of the material, to give the building or facility, on the contrary, massive and heavy. For example, emphasis on vertical joints and flowers lining the pavilion at VDNH in Moscow gave a slender diminutive structure. Vertical joints visually facilitated massive, lined with stone elements included in the composition of buildings pension "Voronovo" near Moscow and in the city carrier Brezhnev. In contrast, heavy stone walls, resting on the ground, can be emphasized horizontal joints release liner, as is done in the building of greenhouses in Leningrad and the Supreme Court building in Tokyo.
In addition to facing facades of buildings entirely natural stone cladding is applied and the individual elements - plinths, stylobates, outdoor stairs, portals, entrances, separate planes of the walls. Such use of stone allows get interesting combinations of textures and colors of different building materials: stone, concrete, stone and plaster, stone and wood, and so on. N.
In Russian, there has long been the traditional architecture of a combination of parts made of white limestone masonry walls, especially in the elegant works of Moscow baroque XVII. This technique is used Shchusev in the building of the Kazan railway station in Moscow. In buildings of Russian classicism of stone made tower, stylobates and plinths. Here, the white stone combined with colored plaster walls.
The traditional Russian architecture, a combination of red brick and white stone details and is used in modern buildings. For facing the Palace of Culture Association "Stroiplastmass" Mytishchi used dark red brick Gzhel factory and travertine. The complex of buildings of the Moscow Institute of Electronic Technology in Zelenograd stands the entrance arch of white marble on a background of red brick wall. And the combination of the white stone with brick arches and the shape vaguely reminiscent of the ancient belfries, give us an idea of the deep connection of modern architecture with the previous Russian architecture.
In modern architecture, there are other combinations of various building materials with a stone. For example, stone wall cladding combined with concrete pavement in the compositions of the country house in Tuscany architect. Marino Rossi, "the house over the waterfall" architect. FL Wright, the museum Takamattsu architect. Kagawa. Here natural stone as it connects with the natural environment, artificial constructions made of concrete, making each of these buildings blends into the landscape. Concrete openwork lattice combined with marble facing of the walls in the composition of the hotel "Moscow" (Baku).
Amazing mix of pale stone and metal we can notice in following examples. The most spread nuance combination of white stone with details in gold anodized aluminum. With this decoration on the walls of the building there is the play of light. Stone gets golden highlighting due to glare from metal, which gives the building a festive character. This combination of materials used in the facades of the Kremlin Palace of Congresses, the Olympic sports complex on prospect Mira, the cinema "Star" in Moscow, the Palace of Culture "Ukraine" in Kiev Opera and Ballet Theater in Dnepropetrovsk, and so on. D. Good impression combination of metal window arrays black with white marble walls in the architecture of the office building in Mainz architect. Jacobson (Germany). Bright vertical wall surface seem fragile, almost dissolved in the blue sky background in comparison with the deliberately rough part of the grid.
The combination of natural stone glass gives a special strength of the composition, based on the sharp contrast of durable stone and fragile glass, for example, the house Centrosoyuz Moscow by Le Corbusier - large glazed glass windows and deaf plane wall of red-purple Artik tuff; House of Chamber Music. Komitas in Yerevan architect. S. Kyurkchyan - glazed wall of the main facade and the deaf volumes laconic geometric shapes of tuff browns; building swimming pools of the Olympic Sports Complex in Moscow - a heavy stone stylobate and curved glass wall; Ford Foundation building - high blind areas of polished granite walls and windows of the conservatory.
Used until recently had seemed incompatible combination of stone and ceramic veneers. Glazed ceramic tiles shining bright colors well-combined with white limestone. The softness of color tones and nobility of the texture of stone soften the coldness of glazed ceramics. The theater building of animals named Durov (Moscow) with white limestone combined facing convex dark blue glazed tiles. The building of the hotel "Youth" (Moscow) travertine softly padded bright colors purple and blue glazed tiles and red-brown granite.
Facing materials, depending on their application in various elements of the buildings represent a large range. This range includes: veneer for the exterior cladding of the field wall and cap for walls and partitions in the interior, plates and strips for flooring; different profile details: cornices, corbels, baseboards, trims, details of the portals, and specialized stones cordon plinth, columns and their bases; elements of stairs: Tread and whole steps, handrails; sill plates, balusters, stone and so on. These parts are made of different kinds of natural stone and have a very different size. The choice of stone for facing various building elements is determined by the aesthetic requirements for color, pattern and texture. In addition to the decorative properties there are a number of requirements that are taken into account, depending on the conditions of service of the stone. For exterior cladding such requirement is the ability to resist corrosion. For those parts of the building, which are most exposed to rain or mechanical influences (plinths, cornices, stairs, railings and τ d.), Used mainly silicate rock stones with a density greater than 2.5 g / cm3. Therefore, the base of the building is the most suitable granite, syenite, sandstone, gabbro, labradorite. It is applied in some cases; soft limestone facing of the plinth is irrational, since limestone quickly, often after only a few years of service loses its decorative qualities: color changes, the surface collapses, gets dirty, covered with stains and smudges.
To cap are mainly used plates 40-60 mm thick. Since sockets are often the only elements of the building, stones natural stone, it is advisable to seek local resources for their finishes. In Abakan, many buildings have caps, lined with slabs of dark brown siltstone shale mined in the vicinity of the city. This slate is very strong, thin slab of a thickness of 10-15 mm, and mounted only solution. A slab of slate having various sizes and irregular shapes, in combination with cement embroidered seams create pictorial effect. This inexpensive, but decorative trim is also used in Krasnoyarsk, and some southern cities of the USSR, where there are local shale.
For facing field wall fit many kinds of types of stone, with the exception of colored marble and plaster. The most often used limestone, gray and white marble, travertine, dolomite, sandstone, travertine. Facing wall plates have a thickness of 8, 10, 20 and 40 mm. Those most damaging effects of the building and grounds are subjected to stage outdoor stairs. For them, the most suitable material is the silica rock having a density greater than 2.5 g / cm3. Because most of these rocks for a long time to resist abrasion rocks with quartz in its composition. It - granite and quartzite. The most stages are used to medium- and fine-grained rocks: granite, gabbro, syenite, diorite, basalt, sandstone. From local breeds used dense limestone and sandstone. Under the terms of the service level you should have a rough surface. With this invoice poorly identified decorative stone-esteem, so pick up the stone steps based primarily on its abrasion resistance, strength and hardiness.
Such elements of buildings, as portals of doors, window frames, cornices and columns lately seldom made from a single piece of stone. They are now generally reinforced concrete lined with thin slabs of natural stone. As decorative as the highest requirements for columns and portals doors located in closest proximity to the observer; on the strength - to the cornices, portals and database columns are subjected more often than other elements of the building, exposed to atmospheric moisture and mechanical damage. For portals and bases of columns used granite, gabbro, labradorite and other high-silicate rocks, giving a thin wall texture. For the eaves, window frames and wall columns of trunks can be used, in addition, limestone, marble, sandstone, travertine.
The means of fixing natural stone in exterior installations selected depending on the size of tiles, as well as the material and construction of the building portions being lined. Thin tiles (6, 8 and 10 mm) are attached to the wall structure due to adhesion with the intermediate layer by the solution. Tile thickness of 20 mm or more, and are attached by adhesion to the layer by the solution, and at the same time using a variety of fasteners: Fix the spring, staples, dowels, twists, bolts, spikes, hinges, hooks, pins.
Wall panels, tiled natural stone factory
Lining of precast concrete panels held on the concrete products plant simultaneously with the manufacture of the basic structure. For such a lining can be used limestone, travertine, marble, dolomite, shell limestone. Facing plates, equipped dowels, placed face to a pre-coated plastic film forms the bottom. The back of the plates are cleaned and covered with a layer of sand and cement mortar grade no lower than 150 thickness of 15-20 mm. Reinforcement of the wall panel is placed on the latches to between it and the facing plates the protective layer solution. Then the fresh concrete mixture and goes further process of forming a wall panel. After steaming cladding panels eliminate defects and carry out its hydrophobization. Not recommended for use this way of facing boards with subtle textures, as polishing may be lost in the process of steaming panel.
When using thin plates (thickness 10 mm) fixing it to the concrete panels made without dowels only solution layer. This method is the most industrial as eliminates manual work drilling holes and installing dowels. Modern cutting technique allows to obtain a stone tile thickness of 6-10 mm. At the Moscow stone processing plant mastered cutting blocks of travertine limestone Shakhtakhtinskaya deposits of Azerbaijan in the plate thickness of 10 mm, which are used in concrete products Beskudnikovsky plant for the production of lightweight aggregate concrete panels with a decorative layer of travertine.
Prefabrication panels with the facing layer of natural stone IE started in the 50s with the construction of tall buildings in Moscow. In a high-rise building of the Ministry of Railways on Lermontov Square 9000 m2 surface of the walls were lined with large-panel method slabs of limestone. Experience in high-rise buildings has revealed the advantages of large-panel lining: reduced labor intensity in 4- 7 times, reducing the time of construction, the ability to perform tiling in the winter, the savings due to thinning of stone tiles and exceptions thickened reference series, good grouting solution due to vibration concreting.
In the last years, there are many buildings which walls are made of panels, tiled natural stone factory in Moscow.
Walls of brick or block veneer in two ways - simultaneously with the construction of the wall and finished wall. When laying the cladding together with masonry walls, they are tied to each other or bonder rows of boards or rocks at rigid connection, or anchoring in the flexible connections. Bonder series for rigid connection with a wall made of the same facing plates. They come in a masonry wall depth than 120 mm. If you do not use the hard compound plate thickness of 20 mm and a height of 300 mm. larger veneer is attached to the flexible connections. When installing stone slabs at the same time laying the basic and flexible connections facing layer on each floor based on a special concrete belt, which leaves a sedimentary seam.
To ready the brick veneer walls are attached to the solution and with the help of anchors. The basic masonry wall is performed with sutures, is not completely filled with a solution. To fix only solution is applied to the tile thickness of 10 mm and a height of not more than 140 mm. When attaching the only solution facing held not earlier than 6 months after the load on the wall reached 85% of the project.  Larger plates are secured to the finished wall with anchors.
For fixing of tiles on the walls, which are made of masonry brick, masonry sealed with steel hinges, which are welded to the horizontal and vertical bars of 10 mm in diameter with a pitch equal to half the length of the facing plates. Thus formed reinforcing mesh used for hanging the anchor, pre-installed in the facing plates. Such fixing of tiles and travertine Crimean limestone applied in the construction of buildings of the city telephone exchange in Moscow on the street. Chekhov.
If masonry walls made of ordinary brick, the mounting plates can be made directly to the hinge device without reinforcing mesh.
Before starting work on fixing of tiles of their exact size is selected so that in the process of lining seam lines obtained perpendicular, horizontal joints can be maintained less strict. Plates also necessary to select the uniformity of tone, color, texture. Most must be chosen carefully slabs with a pronounced pattern, especially striped.
Pairing with mirror tiles and glossy texture is carried out dry with careful grinding edges or seal roll lead. Seams are doing the minimum and fill them with putty. With less subtle textures joints filled with a solution and embroider. Solutions for joints can have a pigment additive color of the stone. The thickness of the seams between the cladding plates is assigned depending on the texture of the front surface. With mirror polished texture and thickness of the seam can be 1-2 mm, sanded and spot - 3 mm, lumpy and furrowed - 5 mm and texture rocks - 10-12 mm.
After finishing tiling eliminate the resulting defects when mounting plates and, if necessary, carry out hydrophobization of the surface of tiles.
Selection of types of stone cladding means of its fastening, placing in various parts of the building must now take into account the possible effects of aggressive environment on the natural stone. Vehicles with internal combustion engines and industrial waste gases determine the current availability of large cities in the atmosphere of sulfur and carbon corrosive gases, dust and soot. These impurities together with precipitation cause corrosion of facing stone, especially carbonate rocks - limestone and marble. Facing stones silicate rocks (granite, diabase, gabbro and sandstones, quartzites), far less than the carbonate rocks, corrosion, since they contain oxides of silicon in the form of mineral compounds, almost non-aggressive to the environment.
Corrosion appears in the form of stone flaking, peeling, blistering and breaking of rock, cracks, voids and splits, discoloration or staining of the stone surface in dark colors, the appearance of brown and greenish stains of organic origin. The speed of the destruction of the stone depends on the composition and structure of rock, climate (rainfall, temperature fluctuations, wind speed and direction), atmospheric concentrations of harmful gases, dust, soot, heat inversion of polluted air, the nature of development of the territory, constructive protection stone cladding from falling on her atmospheric and soil moisture.
There are five basic factors causing corrosion of facing stone: subzero temperatures, moisture (air and soil), sulfur dioxide, carbon gases, biogenic destroyers.
The combination of the impact of freezing temperatures and moisture causes the destruction of the stone lead to cracking, flaking and breakaway stone slabs. This is the most characteristic of the porous limestone. Water penetrating into the pores of the stone and its place of contact with a metal fastening parts in the winter turns to ice, particularly rapidly in contact with a thermally conductive than stone, metal. The ice takes up more space than water, causing cracking of the stone, the cracks gets additional moisture, in turn turns into ice and increasing the fracture. If, moreover, the metal fixing plates formed by the rules, then they start to corrode, rust has a larger volume than the metal, and also contributes to the splitting of the stone. As a result of combined effects of moisture, frost and rust occurs chipping corners of tiles.
Aggressive effects of sulfur gases in combination with atmospheric moisture results in the formation on the surface of tiles caverns, spots, incrustations and films. Sulfur gases, together with atmospheric moisture and precipitation form dilute solutions of sulfuric and sulfurous acids. These acids falling into shallow cavities and pores of the limestone or marble, result in the formation of gypsum - loose mass of sulfate-carbonate composition. It is replaced with plaster of the calcite in limestone and marble.
Carbonic gases emitted into the atmosphere by internal combustion engines cities, interacting with atmospheric moisture to form weak carbonic acid, which dissolves the carbonate rocks. Therefore spoiled polished and polished texture of tiles made of limestone and marble, it is corroded, loses sheen on the surface of the plates appear sinters of dissolved species. Sculpture, bas-relief carving and lose their shape, smoothed gutter. Such "swollen" bas-reliefs and sculptures of marbled limestone can be seen on buildings in London. Moreover, the upper part of the sculpture and architectural detail, is directly exposed to precipitation and constantly dissolving, - white, and the rest - from the dark dust and soot.
Inspection of buildings on Kalinin Prospect in Moscow in 1966-1967, lined. porous plates Crimean Inkerman limestone quarry showed that cladding of buildings located away from the continuously moving transport and in a relatively loose building has no visible signs of corrosion. Facing the other buildings located on the same side of the avenue, significantly affected by corrosion. This is due to the fact that the construction of this part of the prospectus dense, located close to the roadway, uneven; here the conditions for the stagnation of the air with a high concentration of harmful impurities and thermal inversion. The architectural design of the building does not provide elements that protect the veneer of precipitation. White cladding of the buildings for 10 years of service acquired sloppy appearance. To restore normal appearance of facing difficult, as it requires, firstly, mechanical cleaning, and secondly, grinding the entire surface, and with the existing air pollution all this will only give a short-term effect.
Much better preserved buildings facing on the opposite side of the avenue, where construction is more uniform height and no gaps between buildings. This type of construction is less than promotes the formation of eddies of air, washing the building and, consequently, decreases the degree of corrosion of stone cladding. In addition, the veneer of these buildings is protected from rain eaves.
Not subject to corrosion cladding buildings set apart, in good airing. An example is the building of the airport "Sheremetyevo", in 1952, faced with polished limestone slabs Inkerman. Facing the airport building is protected by the eaves and guttering.
Corrosion of carbonate rocks also causes the impact of biogenic destroyers, releasing humic acid: mosses, lichens, algae and single-celled etc. In addition, bacteria that use carbonate rocks as a nutrient medium. Biochemical aggression are most susceptible to limestone and marble in industrial cities, where the polluted atmosphere contributes to the accumulation of plaster, dust and soot in the pores and uneven stone. The circulation of carbon dioxide contributes to creating conditions for the development of bacteria and plants. The surface of the carbonaceous stone has always been in varying degrees of porosity. The porosity of the marbles is low - of a percent, in limestone, it reaches 30% or more. The pores formed habitat environment for various microorganisms are separated during the life of the organic acid on which the salt is then formed. Humus in the pores and cracks contributes to the accumulation of moisture and growth of higher plants, which enhances further the process of destruction of the stone.
To provide long-term service external facing of natural stone requires a set of measures for its proper installation and protection. These include: the choice of stone rocks considering water absorption, frost resistance, structure and mineral and chemical composition; choice of texture, taking into account the aggressiveness, the environment, careful mounting plates to the stones with designs using only fasteners of stainless steel.
Long-term preservation of the outer cladding may promote certain planning techniques when placing the stones in the urban environment of buildings, their location at a sufficient distance from sources of harmful emissions into the atmosphere in a ventilated area where there are no conditions for thermal inversions and stagnant air.
You must be constructive techniques to protect the exterior cladding, namely device cornices, canopies and other items to prevent a direct hit on the lining of precipitation; plinths device of sufficient height, preventing the rise of soil moisture on the walls and storm water.
External facing of carbonate rocks should be treated with hydrophobic solutions, preferably every 2-3 years pre-cleaning the surface of the stone.
Русская версия статьи: вентилируемые фасады