Monolithic reinforced concrete walls. Parameters for calculating concrete thickness. The device of monolithic walls
Skeletons with walls of cast concrete and reinforced concrete
Currently, it is becoming more widespread. monolithic technology construction of buildings. The structural material in this case is reinforced concrete based on heavy concrete. A mandatory element of such a constructive solution is the formwork - the form-structure that forms the surface of the skeleton of the building. In construction practice, mainly two types of formwork are used - movable and sliding. Repositionable formwork can be used both in the form of separate panels, and in the form of volumetric elements. For low-rise construction, it is advisable to use formwork in the form of separate panels, and of small size. Sliding formwork is used for the construction of vertical elements of buildings with a height of usually tens of meters and is inappropriate for use in the construction of low-rise buildings. There is another type of formwork - pneumatic (inflatable), which is used only for thin-walled curved structures (arches and domes), the use of which in low-rise construction is very limited. At the same time, the main criterion for using this or that type of formwork will be its turnover, so the main formwork during the construction of the skeletons of low-rise buildings will, of course, be the small-panel formwork, which allows the most mobile to obtain a variety of structural forms.
The lifting of aluminum panels intended for manual control is less susceptible to production shutdown due to mechanical failures in the lifting equipment. In addition, we must make sure that our formula provider provides all guarantees of safe working at heights; this is achieved, and only yes, there are safe transit solutions in armament zones, suitable platforms and watchdogs, all of them are fully compatible with the formwork. There are many formwork systems on the market today, but aluminum is undoubtedly the best option.
When erecting the skeletons of low-rise buildings, the use of lightweight concrete based on expanded clay, perlite, agloporite and other porous aggregates is more appropriate in the form of small blocks, rather than in the form of a solid monolithic building element, which is confirmed by practice.
Monolithic technology assumes that with its help only the supporting part of the skeleton is erected, which then needs to be supplemented with layers of insulation and decoration.
In addition to the above, they bring such advantages as flexibility in design, simple modulation of the panel, their durability contact surfaces and high adaptability; if we find a product with such characteristics and which also provides excellent technical support, we can achieve complete success in building any structure with this system.
The construction system consists of continuous structural walls of general concrete, formed in place, 10 cm thick, armed with welded metal screens located in the center of the walls. The basis is determined taking into account each implantation site of residential units.
For the erection of walls of various types of low-rise residential buildings - individual houses, cottages, villas, villas, etc., similar to them, the most appropriate is the use of light, manually assembled, removable shield formwork or small-sized fixed formwork.
Formwork of the first type includes panel formwork of modules based on durable waterproof five-layer plywood 21 mm thick, reinforced on both sides with a special cladding (laminate) and enclosed in metal frames from steel profiles based on galvanized or alloy steel. The frame of the panels can be made of aluminum profiles or using wooden panels.
The roof is formed by a wooden structure, with a ceramic tile roof. The construction system is intended for the construction of residential buildings up to five floors in a rural and urban atmosphere. The system consists of casting walls and massive slabs of reinforced concrete with centralized metal screens. The structure is designed for each specific building structure. The manufacturing process of the structural system allows the geometric control of the pieces and obtaining surfaces suitable for obtaining finishes.
Both of them are assembled with 100 mm mesh electric-welded steel screens and wires with a diameter of 4, 2 mm. System materials and components. The molds are made of plywood and plasticized sheets reinforced or structured with steel profiles fixed with screws through spindles that determine the distance between the faces of the molds.
Proven in practice, the maximum size of such a shield module is 2 640 x 750 mm with a mass of 61 kg, i.e. It can be mounted by two workers. Such shields are interconnected either using a bolt clamp, or special brackets. Such formwork allows it to be used for concreting both walls and columns, foundations and ceilings. The turnover of these shields is up to 300-400 times. Options for using such a formwork are shown in Fig. IV.25.
Ceramic plates are applied to the inner walls of the wetted areas, applied by adhesive to concrete. On the walls and ceilings of dry areas, a layer of thawing coating or plaster and paint is applied. The floor covering consists of ceramic tiles in wetted areas, and in dry rooms ceramic tiles or smooth cement finishes are used. The exterior walls are lined with light texture.
The company monitors production daily, given the importance of executive planning for the construction system. Productivity is collected and evaluated by the apartment. The better the performance information, the better the quality of programming and manpower management. The collection of these indicators is part of the control. These indicators feed future charts and return the work itself, helping to reprogram, as shown in the table.
Reinforcement of the reinforced concrete part of the structures of low-rise buildings is most often undertaken for structural reasons. At the same time, the calculated reinforcement of the lintels and vertical faces of all openings, as well as the angles and intersections of walls and, of course, ceilings, is mandatory. Reinforcement is recommended to be made by welded frames and nets.
Fund, baldrama and first plate. Execution is carried out in accordance with the structural design, leaving the perimeter of the plate 8 cm more than indicated in the design to accommodate the outer surface of the molds. Ground floor slab and marking layout.
From the central axis of the wall, 13 cm for each side are taken into account, at a distance of 26 cm, which corresponds to a wall thickness of 10 cm and 8 cm of each side to accommodate the faces of the forms. In the spaces of doors and windows, the metal screen is cut out, and the screen reinforcement is placed in the windows and doors in accordance with the structural design.
The minimum thickness of a monolithic reinforced concrete layer in the construction of low-rise buildings is 120 mm for walls and 150-160 mm for floors (from reinforcement conditions).
Concreting should be carried out only by moving plastic concrete mixtures manufactured centrally, which more reliably ensures their quality. The concrete grade used must not be lower than M300 (class B 25), based on the conditions that monolithic structures should be dismantled when concrete reaches a strength of about 10 MPa (100 kg / cm2). For M300 concrete, this strength occurs approximately three days after its laying under standard hardening conditions (temperature 15-18 ° C and humidity over 80%).
The use of a solvent based on mineral oil on the inner surfaces of molds. Lockout, electrical and hydraulic installations. The internal blocking of parts, the placement of pipelines, electrical boxes, sanitary pipes and the placement of hoses for the passage of the locking screws is made in accordance with the design. Pipes with a diameter of more than 40 mm are then placed in masonry shafts with an insert of a metal screen on the assembly between the shafts and concrete walls.
Placement of plastic pads on the screens. Gaskets are placed every 50 cm, both horizontally and vertically, to provide a specific coating defined in the design. Placement of templates in forms. Before closing the frames, door and window fittings are placed to guarantee a projected project span.
Using the so-called fixed formwork avoids waiting for the start time of formwork.
Fixed formwork is the second type of formwork in which the formwork remains in the concrete structure. This method is preferable when the repeated use of inventory formwork is excluded or when it is necessary to reduce the time of construction of the building.
Concreting of walls is carried out using buckets transported by cranes. The specified concrete does not require mechanical compaction, with the exception of special places, and it is dosed and mixed in work, in concrete mixers. The deformation is carried out at least 15 hours after concreting, after checking the compressive strength of concrete. The filling of the holes in the walls resulting from the passage of the spindles for fixing the forms is carried out with the introduction of cement mortar and medium sand before finishing these walls.
The start of services must be preceded by protection, which avoids the fall of people or materials. Work at heights of more than 2 m: you must use the type of seat belt. In any vertical transport situation, the maximum load supported by the equipment must be observed, and all necessary precautions must be taken to avoid material fall.
Several variants of this type of formwork are known, in which slabs made of fiberboard, arbolite, DSP (cement-bonded particle boards) or other materials in which cement is an integral part, or bulk formwork elements based on various types of cement concrete - heavy concrete, fine-grained concrete are known , expanded clay concrete, etc.
List of collective protective equipment required to perform maintenance. Quality control is carried out in work in accordance with the execution and verification procedures, checklists of materials and services, the executive design of the construction system, etc. The following items are checked.
System Description A monolithic concrete panel for buildings has a structural and closing function and consists of polystyrene foam panels coated with microcontainers reinforced with metal screens. They are structured with mild steel shields with galvanized wires with a diameter of 2, 1 mm and a mesh of 50 mm x 50 mm or 150 mm x 50 mm, located on both sides. The plates are interconnected by galvanized carbon steel connectors with a diameter of 2, 76 mm, electrically welded to the screens.
Some types of fixed formwork, which are advisable to use in low-rise construction, are presented in Fig. IV.26.
When using plates or thick sheets of the listed materials, it must be borne in mind that they perform not only the role of forming elements, but also the role of a heat-insulating casing. Therefore, in the outer walls, the outer side of the formwork will always be thicker than the inner one due to thicker sheets (plates), and in cases necessary for thermotechnical reasons even with the use of foam plates (PSB-S).
Microstructure is used for structural applications. The company recommends that the water-cement coefficient not exceed 0, 55. Implementation Soil preparation The foundation is prepared before work commences and includes cleaning services such as weeding, excavation and landfill. The final height of the top of the radiator is 18 cm above ground level.
The location of the work was carried out in accordance with the projects of urbanization and architecture, and the devices are located at a height of 50 cm above ground level and at a distance of 100 cm from future walls, aligned and secured to ensure the tension of the leveling wires. The contractor is responsible for verifying minimum returns and overall alignment before building walls.
Valves in such systems are installed in the same way as described above.
When using hollow volumetric concrete elements as permanent formwork, the voids contained in them should be used to create an additional heat-insulating layer or to place vertical reinforcement, if it is necessary for design or structural reasons. It is possible to fix an additional heat-insulating layer from the outside with the help of targeted anchors.
Depending on the type of terrain, other types of foundation may be adopted. It can be simple or double, depending on the design, which takes into account the tension and soil conditions at the implantation site. In front of their concrete are hydrosanitary, electrical, communication, safe and other systems that interfere with work with the radiator.
These steel rods can be placed together with foundation armor or placed later, punching the foundation and securing them with a grill or equivalent product depending on the location and design settings. Walls may have a structural or sealing function serving earthworks, residential buildings, commercial buildings, industrial enterprises, etc.
There is also a system of non-removable formwork based on polystyrene foam hollow elements, in which the supporting functions are performed by concreted middle parts of such elements, which are installed apart. In these systems, three types of elements are used: wall, lintel and special, necessary to ensure the support of the floor. This type of formwork is shown in Fig. IV.27.
The system is characterized by the formation of walls in place, considering all electrical and hydraulic installations, window and door frames already located after being removed from the mold. In recent years, Brazil has used lightweight foam or foamed cellular concrete in the manufacture of vertical fences as an alternative to reducing debris and waste in general.
Preparation and decoration of the foundation of Radier. Fixation of electrical and hydraulic services. Concrete foundation foundation. Detail of an electrical junction box. Disassembly of the mold after curing. Several stages of the assembly process. For forming walls, metal molds are used, the sizes of which correspond to each specific structure. The design process allows geometric control of the walls, covering reinforcements and obtaining surfaces to obtain the finish.
It should be noted that the polystyrene sheath of such a formwork requires protection both from the external and internal sides in the form of plaster or cladding.
Due to the monolithic connection of all elements, the supporting frame of the building is characterized by a high degree of rigidity and stability. Foundations under monolithic houses more often design tape from butobeton or from short bored piles with a monolithic grillage, the technology of which also includes elements cast concrete. For winter work, prefabricated foundation options are usually used. The basement of lightweight concrete walls is easier to carry out in the form of an additional coating of an atmosphere-resistant mortar or cladding with frost-resistant plates. The remaining surface of the external walls is protected by weather-resistant plaster with the addition of dyes or tiled with decorative tiles.
The production process is characterized by successive cycles of assembly and disassembly of molds for molding lightweight reinforced concrete walls. The system provides for the inlay of hydraulic and electrical installations with the installation of pipelines and junction boxes made before concreting the walls, in addition to the previous installation of devices for determining the spans of doors and windows.
Main components, elements and equipment
The system design provides for the assembly of fittings, hydraulic piping, pipelines and junction boxes before concreting walls. Preset patterns for door and window openings are also pre-installed. The frames are equipped with locking devices that determine the distance between them, thereby adjusting the wall thickness. They also support efforts during the pumping of concrete to deformation, avoiding unwanted movements.
Local building materials for the walls of low-rise residential buildings are various soil masses based on clay or lime-cement bonding. Such material does not have high strength and is usually used for the construction of walls of one-story houses. Soil and mud walls have a relatively high thermal conductivity, so they are used for construction in southern climatic zones.
To ensure a minimum 30 mm nominal reinforcement cover specified in the design, rigid plastic spacers located every 50 cm are used to hold the anchor assembly in its original position. The walls do not require a coating of a one-time mortar or plaster, only surface corrections and plug-ins of the holes remaining in the walls by means of metal locking devices made with a solution expandable.
At the same time, nodules of walls and slabs can be performed; It has a solution for concreting stairs in combination with walls and slabs; It has panels of various sizes, adapted to any project situation, individual. Does not use wood and finish: the end of improvisations; It has security features such as: work platforms and perimeter security; The panels also have a special device for configuration, issuing the use of tools after each cycle; To ensure alignment wall panels the design provides for the use of tubular equalizers, when necessary; Reinforcing triangles that tighten all corners of the panel. Thanks to the precise aluminum frame system, you get walls, beams, columns and a single-level concrete slab in one sink.
To reduce thermal conductivity and increase the strength of mud walls, a section of plant dry fibers is added to the clay mass. Such material is called adobe. Monolithic walls made of adobe have been used for at least 25 years with proper use. The manufacture of adobe does not require the use of cement and lime, and the walls of adobe provide a favorable microclimate of the premises. For the design of residential buildings from adobe, it is necessary to know the basic structural requirements for walls made of this material. The cornice part of the adobe walls should have a roof overhang of at least 45 cm, while admission of adobe outside the wall plane is not allowed, i.e. eaves overhang can be made only by removing the eaves boards of the roof (filly). The supporting part of the roof is designed only according to an undisturbed scheme, i.e. it is recommended to use a roof with hanging rafters. The use of a roof with lay-on rafters is possible provided that the wall beam (Mauerlat) is attached to the wooden joists, for example, with steel brackets (Fig. IV.28 b, 14).
In this case, the roof should have a slope that coincides with the direction of the floor beams. Mauerlat is made in the form of a flat wooden beam recessed into the wall material in the center of its cross section to evenly distribute the load from the roof. For the same purpose, floor beams rest on the wall in its center; a flat wooden beam is placed under their supporting part. In this case, the Mauerlat can be supported on the ends of the floor beams. Lintels above the openings are made of boards or wooden bars with crossbars. Between the jumper and the box of the opening leave a free gap, providing for the possibility of subsidence of the wall up to 10% of the height of the opening. The gap is filled with tarred tow. Spans of openings make no more than 2 m, and the width of the piers in the corners is at least 1.5 m. Unloading boards are installed at the bottom of the window openings, to which the windowsill and drain boards are attached. Unloading boards and Mauerlat are installed continuously around the entire perimeter of the walls, rigidly linking them in the corners. The base is made of weatherproof stone or other similar materials. The surface of the adobe wall is carefully protected from moisture.
There are two construction technologies monolithic walls at home. The difference in technology is the use of different formwork designs: removable formwork (the structure is removed after hardening concrete) and fixed formwork (dismantling is not provided).
The construction of monolithic walls with removable formwork
Basically, removable formwork is made of wood or metal, the formwork in this case is prefabricated. When using metal formwork, metal shields are taken. A more economical removable formwork is considered to be a formwork made of plywood or boards, which is knocked together right at the construction site. Removable formwork can be used repeatedly.
During installation, the formwork is exposed to the height of the concrete layer, which is poured once. From about 20 to 200 cm. The width of the formwork should correspond to the thickness of the future wall.
Construction of monolithic walls using removable formwork:
For concrete to acquire maximum strength, it will take up to five weeks. Then you can perform wall insulation and decorating the facades of the house.
If you are building with the technology of removable formwork, do not forget that the walls will be cold enough, due to the presence of metal parts of the frame in the walls. Walls necessarily require additional insulation.
Instead of concrete, mixtures with lower thermal conductivity can be used, for example, expanded clay concrete, perlite concrete, slag concrete, aerated concrete or foam concrete. In this case, the walls will be warmer, but less resistant to increased loads.
The construction of monolithic walls with fixed formwork
Fixed formwork is a panel or block of various materials. Blocks or panels are mounted in the formwork structure, then reinforced and poured with concrete mixture. After the concrete has dried, the formwork is not removed, it remains the functional part of the wall, and will fulfill the role of wall insulation.
At the moment, the most common type of fixed formwork at construction sites in the form of thermoblocks made of expanded polystyrene.
Construction of monolithic walls using fixed formwork:
Only concrete is used to fill fixed formwork, since the vapor permeability of polystyrene is lower than warm mixtures. Consequently, warm mixtures between polystyrene plates will accumulate condensation, which will lead to the formation of fungus and mold.
Kinds concrete solutions for monolithic construction
Monolithic construction allows the use of solutions with different vapor permeability and thermal conductivity:
- Concrete. Houses with these walls require additional insulation, since concrete has high thermal conductivity.
- Reinforced concrete. The material is even colder than concrete, since the reinforced frame acts as a "cold bridge."
- Expanded clay. The house will be warm enough. Indices of thermal conductivity and vapor permeability depend on the density of the mixture.
- Slag concrete. This is slag concrete. The material is less durable than expanded clay.
- Sawdust concrete. It is a mixture of cement, sand, sawdust and water. Walls made of such material will be environmentally friendly, durable and warm. This material requires waterproofing.
- Arbolite. This is a mix of cement and wood chips. The material is very durable and warm.
- Foam concrete. This is aerated concrete, which is made from a mixture of cement, sand, water and a foaming agent. The material differs from the rest in good indicators of thermal conductivity and vapor permeability.
