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Monolithic construction method
One of the most modern ways erecting monolithic walls and slabs is based on the use of formwork, which can also be used by individual developers when assembling semi-finished houses. For the simultaneous manufacture of reinforced concrete walls and monolithic reinforced concrete floors combined with them, tunnel sliding formwork is used.
Building construction, created using this method, have all the positive qualities of a monolithic frame and do not have the disadvantages characteristic of traditional types of formwork. Many of the benefits of this technology account for its rapid spread. In this case, labor costs are reduced, time and materials for formwork are saved. With the help of steel templates, high dimensional accuracy is achieved and a surface that does not need plastering is obtained (Fig. 1, 2).
The tunnels built one next to the other must be “dressed” with auxiliary, easily assembled prefabricated elements (without plaster). Such elements are staircases, prefabricated elevator shafts, sanitary blocks, stiffeners, enclosing facade structures, unplastered partitions. The Hungarian Peva system, for example, uses plastic window and door blocks.
The elements on the construction site are moved using tower cranes.
Rice. 1. Monolithic construction according to the Outinord system - an element of metal formwork
The main requirement for structures erected using tunnel formwork is to achieve the required strength by the time it is removed. The concrete must have good workability; the walls are concreted, filling the formwork with layers of mortar 30-50 cm thick. The concrete is compacted in layers, applying vibration with the capture of the previous layer. During heat treatment of concrete, it should not be allowed to heat up above 35-40 ° C.
Another method of monolithic construction, which should be mentioned, is called "no-fayns", i.e. "Without fines". This technology is applicable for residential construction where panel construction is not economically feasible due to long distances from the plant to the construction site, or where the requirements for buildings are not very high. The method is also suitable for the construction of individual houses.
The essence of the technology lies in the application monolithic concrete based on one fraction of aggregates. Concreting is carried out by pouring into the formwork without compaction and vibration. The formwork, which is installed at the height of the floor, consists of vertical sheets connected by special collapsible ties, which makes it easy to work with.
Rice. 2. Monolithic housing construction of the "Peva" system; 1 - reinforced concrete wall, 2 - external wall formwork element, 3 - internal formwork element, 4 - metal formwork lifting, 5 - stripping platform, 6 - tower crane hook
For the formation of a surface in contact with concrete on multi-layer glued wood sheets formwork with a thickness of 14 mm, a layer of plastic is applied. Vertical concrete walls covered with gypsum-cardboard dry plaster (Fig. 3).
Rice. 3. Construction method 1 - external sprayed plaster, 2 - monolithic concrete wall, 3 - pine plank, 4 - drywall plaster, 5 - wallpaper, 6 - base of the floor, 7 - magnesite screed, 8 - leveling cement mortar, 9 - reinforced concrete floor
Monolithic construction method
Despite the fact that the history of monolithic housing construction does not have much time (they began to seriously build housing from reinforced concrete only from the beginning of the twentieth century), it managed to acquire its own myths. It is interesting that most of the "legends about the monolith" are told, for some reason, in Russia, where the technology has been widely used for only a couple of decades. Let's try to disassemble the main "horror stories" about this advanced construction method and find their origins.
Myth number 1. Monolithic construction is expensive
This myth has a real foundation and goes back to Soviet times... Recall that then high-quality metal was a scarce and limited (that is, limited in free sale) commodity, and an extensive network of DSK (house-building factories), specializing in the manufacture of reinforced concrete panels, fully provided the planned flow-through construction of housing. Since quality was not in the first place then, it was not necessary to seriously talk about the massive introduction of a high-tech method in housing construction. On the other hand, the monolith was widely used in unique structures, such as dams or special-purpose buildings - suffice it to recall the Moscow Central Telegraph, Izvestia House, the building of the Ministries of Light Industry and Agriculture, the House of Soviets in Leningrad, Minsk and Kiev, created in the 1930s. Naturally, such uniqueness could not be cheap.
Today, the monolithic method has practically caught up with the panel in terms of mass and has caught up with it in terms of cost. The remaining difference in the price of an "elite" monolith and a "democratic" panel depends, first of all, not on construction costs, but on the price and quality of land: in the historical center or in a park zone, it is several times higher than prices somewhere on the outskirts or industrial zones ( fig. 1).
Rice. 1. Cost square meter in houses different types(thousand roubles.)
in Moscow and the Moscow region (according to the company "Azbuka housing").
Myth number 2. Monolithic construction is a long-term construction
Long construction stories monolithic structures also "born in the USSR" - unique buildings, due to the originality of architectural, planning and engineering solutions, will always be inferior in the speed of construction to mass objects. However, the availability and popularity of technology levels this difference.
Suffice it to recall from the Soviet times SNiP 1.04.03-85 "Standards for the duration of construction and groundwork in the construction of enterprises, buildings and structures" (by the way, they have not been canceled to this day). Even 30 years ago, the construction of, for example, a 12-storey building with an area of 8000 m2, according to the standard, required 8 months for a large panel, 9.5 months for a frame-panel method, and 10 months for a monolith. As you can see, the difference is small, but today it has practically disappeared.
“In fact,” says Andrey Kobets, Product Development Manager of SVEZA Group, the world leader in the production of birch plywood, “the speed of construction mainly depends on the culture of construction and technologies that ensure its quality. For example, the use of re-support racks in horizontal formwork allows increasing the rate of monolith erection up to 4-6 floors per month, which is not inferior to the panel (this technology, for example, was used to build the Hyatt Regency Sochi hotel). This can also include the use of film faced plywood with SVEZA Deck 350 markings. Marking significantly simplifies and speeds up cutting, and also facilitates the work of reinforcement workers. Accordingly, this leads to a reduction in labor and time. "
Myth number 3. Monolithic construction is not environmentally friendly
It's hard to say where this myth came from. By far the most environmentally friendly wood construction(and even then not a fact, given the various impregnations), but how many wooden houses in modern cities? It is often said that concrete walls "do not breathe", but any panel made of the same reinforced concrete can be blamed for this. Moreover, the risk of "running into" radio or chemically active cinder concrete exists rather in old "panels", and not in modern monolithic and monolithic-brick houses. The fact is that in the middle of the 20th century, waste (slag) of blast-furnace production was widely used in the production of lightweight concrete, which often had a noticeable radioactivity. Since there was no special control over this parameter, in the USSR there were whole "phoning" microdistricts, although the excess of the norms was insignificant.
Today, all houses, both brick, panel and monolithic, are examined upon acceptance, including for background values for radioactivity. For reference, according to SanPiN 2.1.2.1002-00, the equivalent dose rate of radiation inside buildings should not exceed the dose rate permissible for open areas by more than 0.3 μSv / h (33 μR / h). The natural background of radiation in Russia is 5-20 μR / hour (microroentgen per hour). Thus, values up to 50 μR / hour should be considered the norm. As shown by a recent massive study in St. Petersburg, in no type of residential buildings the internal background did not exceed 30 μR / h.
Myth number 4. Monolith is unaesthetic
It is believed that with all the architectural possibilities, the monolith requires a complex and expensive exterior finish - they say, "bare" concrete is ugly. Here again the origins go back to the USSR, when the "gray" industrial facilities were most often erected according to the monolithic method, and the few residential and administrative buildings were built in the style of constructivism, laconic and not inclined to embellishment.
Today's monolithic buildings allow you to achieve almost any layout and an amazingly diverse facade appearance, and this is not to mention the possibility of erecting buildings of unlimited height. It is also worth noting that the unfinished concrete surface covered with special compounds, the quality of which largely depends on the quality of the formwork panel, looks very aesthetically pleasing and, moreover, has become a fashionable architectural trend for a long time.
In Russia, this technology has recently been used to build the Hypercube Technopark in Skolkovo, where the offices of Siemens, IBM, Cisco and 16 other companies are located. “Unplastered walls are a sign of a certain approach,” tells about the peculiarities of the style interior decoration"Hypercube" Boris Bernasconi, project architect. "They symbolize an open space for communication, versatility, and the ability to transform in time."
Of course, this approach requires high quality materials and work - the so-called "architectural concrete", which does not need additional finishing... In this regard, the fashion for open walls came to Russia only recently. “Before the construction of the Hypercube in Russia, it was traditionally believed that obtaining high-quality architectural concrete is possible only with the help of plastic or fiber-reinforced concrete formwork,” says Vadim Mysyachkin, engineer of the department of special formwork systems at the PromStroyKontrakt Group of Companies. with the help of the PSK girder formwork with SVEZA film faced plywood, proves the opposite. With its help, an excellent result was achieved - after dismantling the mold, no additional concrete processing was required. "
Myth number 5. Monolith is too labor intensive
In general, this myth is directly related to the legend of the long-term construction. Modern technologies, including formwork systems, mixing units, high-quality binders, etc., are no more laborious than panel construction. Allowing at the same time to achieve the highest quality with the same efforts, both labor and logistics. Moreover, there are situations, for example, in dense urban development, when the monolith becomes the only possible way the construction of the object. Therefore, by the way, monolithic houses are so often built in historical centers - it is much more difficult to mount a panel in the absence of convenient access roads.
Myth number 6. The monolith is cold
In all likelihood, this myth was born from a simple analogy - "the concrete is cold, which means that the house from it will be like that." Monolithic houses, simply due to the absence of seams - this "Achilles' heel" of panel houses, are much more airtight. Not to mention that modern technologies insulation allows today to build "passive" houses, that is, buildings that practically do not radiate into environment heat.
Myth number 7. Monolith is not built in winter
Until relatively recently, in fact, they did not build. It's all about the composition of concretes, which "do not like" low temperatures due to disruption of hydration processes. Today this problem is solved, firstly, by special additives that can reduce the operating temperature range deeply "in the minus"; secondly, a variety of heating systems for both the mixture and the construction site itself.
Almost all construction companies erecting monolithic buildings work all year round. “From the point of view of using monolithic technology, winter construction today is not an exception to the rule, it is the norm,” says Pavel Demidov, head of the Stupinsky section of the industrial and construction company “Monolit”. - Monolithic objects are being built with the same frequency as in the summer, because everything depends not on the wishes of the company, but on the receipt of financing. In addition, we usually have a certain volume of orders for a year that we have to fulfill, regardless of the season. " Confirmation of this is the recently built stadium "Spartak" in Moscow, the construction of which went on despite the change of seasons.
Myth number 8. The monolith is poorly resistant to soil vibrations
An earthquake strong enough will destroy almost any building. However, the fact that most modern skyscrapers, including those in earthquake-prone areas, are built using monolithic technology, speaks for itself.
For example, most of the structures of the Sochi Olympics, erected in the Imereti lowland, where the seismic hazard is estimated at 8.4 points, are monolithic. The Bolshoi Ice Palace, which was built on a loose foundation, required a special approach related precisely to the pouring of the monolith. If instead they preferred the traditional way - the pile system, the piles would have to be driven to a depth of 70 m, and it would take about 3000 of them! Pouring a powerful concrete slab - more than 40 thousand cubic meters of concrete - made it possible to significantly simplify and speed up the work and ensure seismic resistance up to 9 points. That is, resistance to seismic shocks today is determined not by the construction method, but by measures for seismic isolation and damping, which are able to ensure the safety of buildings even in very seismically active areas.
Any change in conventional technology is usually accompanied by the emergence of rumors and prejudices. The emerging myths, although they may have some basis under them, have an indirect relationship to reality. The ongoing debate about the advantages and disadvantages of housing construction methods is a typical example of this. Therefore, an objective look at the origin of such "legends" will help innovations take their rightful place in our country.
Material provided by SVEZA
The technology of monolithic construction appeared quite a long time ago, but they began to be actively interested in it only in the 20th century, when more progressive methods were needed to increase the pace of urban planning. Despite the fact that in European countries the technology has taken root and justified itself, in the republics of the former Soviet Union it was practically not used. The refusal was due to high labor costs and long construction times.
When command-and-control methods of management disappeared into the past, the attitude towards monolithic construction in Russia changed. As in Europe, in our country, the commercial and residential real estate market has been replenished with buildings built using this technology, and has competed with brick and wood structures, as well as prefabricated building structures.
Monolithic construction technology
According to its structure, the building can be prefabricated monolithic or monolithic. In the first option, only the load-bearing parts of the building are performed using the monolithic technology. In this case, walls and partitions are made of bricks or reinforced concrete panels. When erecting completely monolithic structures, this technology is applied at all stages of construction. It involves the manufacture of all structural elements directly at the construction site: first, the formwork is prepared, and then it is filled with a concrete mixture.
A monolithic foundation is a very solid structure, since it is made in the form of a solid slab. Such a block minimizes ground pressure and is able to withstand maximum loads. Its insignificant shrinkage is also a valuable advantage, which has a good effect on the "behavior" of the floors.
But the advantages of monolithic construction will manifest themselves only in the case of full compliance with technological processes. Moreover, the work must be carried out sequentially, step by step:
- Preparatory
The site is being set up, the necessary Construction Materials... The standards provide for the use of concrete mixtures of grades 200 - 400.
- Formwork arrangement
Formwork panels are being mounted. Their configuration and dimensions must correspond to the construction plan. Finished structures are treated with a special solution. The next step is to install the reinforcement cage. According to the technology, it is performed with longitudinal or transverse load-bearing walls... Overlappings are arranged on load-bearing columns.
- Filling the formwork
From the factories, concrete mixtures are delivered to construction sites in concrete mixer trucks. With insignificant needs, the mixtures are prepared independently using concrete mixers. Cranes or special concrete pumps are used for pouring. During pouring, surface vibrators are also used: this allows the mixture to uniformly fill the entire formwork, practically eliminating the formation of voids. This ultimately affects the final strength of the concrete.
- Dismantling the formwork
The work is carried out after the final hardening of the concrete mixture. If you plan to use the formwork as an additional heat-insulating layer, it is made permanent. In this case, the material for its creation is polystyrene, which has good thermal insulation properties.
Depending on the scope of application, several types of formwork are used in construction: wall, under the foundation, for arranging floors, tunnel and for creating circular walls. Monolithic technology involves the use of two types of formwork:
- panel board, with the use of concrete mobile panels;
- tunnel, using ready-made structures of the required configuration.
Features of monolithic construction
Speaking about the features of monolithic construction, one should mention the pros and cons of the technology. But, shortcomings are the result of an unprofessional attitude to work. As for the advantages, the features of the technology will tell about them. Monolithic construction is different:
- rapid construction of buildings;
- extreme structural strength. This is especially important in seismically unstable regions;
- longer service life (in comparison with buildings constructed using other technologies);
- ease of use.
Notes (edit)
Using the technology of monolithic construction, the following was erected:
- the world's tallest TV tower (Toronto, 555 meters);
- part of the Ostankino TV tower. The total height is 537 meters, 380 of them were built using the described technology;
- buildings owned by Petronas (oil company, Kuala Lumpur);
- three of the eight Moscow skyscrapers.
Summing up the conversation about monolithic construction, we note that poor execution can ruin any idea. If all requirements are met, then this technology is the best choice!
