Columns are load-bearing engineering structures that provide vertical strength and rigidity to the structure. Depending on the level formed bearing capacity and manufacturing method, today several types of columns are being built: metal, prefabricated and monolithic. As one of the main methods of constructing a column structure, pouring columns with concrete is considered the most common.
The erection of columns helps reduce construction time.
Therefore, the most popular, cost-effective and often used for self-construction are monolithic columns. Advantages metal racks and monolithic columns are considered their very fast construction, which allows to reduce construction time.
Process Features
Metal columns are installed using special equipment.
At the extreme corners of the house (in places of least load), the columns can be made of steel square pipes with a total cross-section within 150 mm, which are connected to the base and ceiling surface using anchors.
The only disadvantage of using this type of columns is that there are not enough of them complex installation(using a crane). This is not always advisable when self-installation and concreting columns.
Small-sized ones can also act as columns. brick walls. On verandas and porches you can use columns made of rounded logs or wooden beam. On concrete base they are fixed by installing them in steel glasses pre-fixed with anchors, followed by concreting.
The most important column structures The house has columns located in the central part of the building.
Laying concrete in columns: a- up to 5 m; more than 5 m high; c- with dense reinforcement; d - diagram of formwork with a removable panel; 1 – formwork; 2- clamp; 3- tub; 4- vibrator with flexible shaft; 5 – receiving funnel; 6-link trunk; 7- mounted vibrator; 8, 9- pockets; 10-removable shield.
In most cases, columns of a certain (calculated) section with a metal reinforced frame are made here, which are cast from concrete using inventory formwork.
Pouring concrete columns is a responsible undertaking that requires certain knowledge and skills of the work performer. Ideally, pouring columns with concrete should be done in one step to avoid the appearance of intermediate cold joints.
In this case, it is important to ensure that the cold seam of the column has a strictly horizontal position. Otherwise, the column will be subject to destruction.
List of tools
To effectively pour concrete into columns, you will need the following set of tools and construction equipment:
A concrete pump is necessary when constructing columns.
- corner with right angle;
- wooden spacers with stakes;
- level (water level can be used);
- screws (using a screwdriver if possible) and nails;
- hammer (sledgehammer);
- metal wire;
- reinforced rods (or mesh);
- boards with maximum width (for creating formwork panels);
- external or internal vibrators (or concrete pump), which, if necessary, can be replaced with a metal rod;
- roulette;
- concrete mixer (or any equipment for mixing concrete mortar);
- anchor bolts;
- various types of clamps;
- metal rod.
Construction stages
Pouring columns with concrete implies the following construction stages:
Formwork for columns: shield, anchor, strut.
Reinforcement works
When arranging columns, installation of vertical reinforcement with an average diameter of 12 mm or more is usually used, consisting of 4 main bayonets (rods) placed in the shape of a square (at its main corners). For the convenience of installing reinforcement for columns with a height of more than 3 m, it is necessary to equip scaffolds with a flooring width of more than 1 m with fences within 0.8 m in height every 2 m in height. Frame bases of columns can be assembled in different ways.
With small sizes, volumes and weight, the frame of the columns can be installed in the future formwork box, which is done manually by turning finished design frame. If the diameter of the reinforcement is no more than 16-20 mm and it is quite heavy, then it would be more advisable to pre-assemble the base of the frame and then knit it in place, installing separate rods. When placing finished frame columns and its further strengthening using all kinds of supports and boards.
It is advisable not to stand on their rods during bonding (or welding) work on the installation of vertical column frames. The reinforcing bars are fastened together special clamps(metal wire) at a certain distance from each other, which is usually 40 cm.
Installation of formwork
In normal cases, a formwork box is assembled with the necessary internal dimensions(for example, 25x25 cm). It should be fastened very carefully. The formwork is installed on 4 sides of the prepared reinforced column.
Wooden spacers with stakes are installed on all sides of the column. At tall sizes Column formwork is mounted on 3 sides, and the remaining side is expanded during the concreting process. The formwork box (made of boards, plywood, etc.) must be leveled and secured with screws to hold the concrete solution inside. Using a corner, the conformity of right angles is checked.
Concreting
It has its own nuances. When casting columns, one of the main parameters is considered. For standard monolithic columns, concrete with a mobility value of P2-P3 is used, and when pouring columns of densely reinforced structures, it is advisable to use concrete with a mobility value of P4 or higher. This type of concrete mixture is also called cast concrete. This type concrete tolerates the process of laying into formwork quite well, even without the involvement of various vibrators and concrete pumps. When conducting
Composition of the process, preparation for concreting
When concreting, the mixture fills all the spaces between the reinforcement bars and forms protective layer the required thickness and is subjected to compaction of the corresponding specified density and grade of concrete.
Concreting consists of preparatory and testing operations, the laying process, which contains operations for receiving, distributing and compacting the concrete mixture, as well as auxiliary operations carried out during concreting.
Immediately before concreting, the formwork is cleaned with a jet of water or compressed air from debris and dirt. The surfaces of the wooden formwork are wetted. Slots in wooden formwork more than 3 mm wide are sealed to prevent laitance from leaking out. The surfaces of steel and plastic formwork are coated with a lubricant, such as waste oil, and reinforced concrete reinforced-cement or asbestos-cement formwork-cladding is washed with a stream of water. The fittings are cleaned of dirt and rust. At the same time, they carry out work on setting up mechanisms, machines and devices used in all interrelated concreting operations. The necessary equipment is installed at the workplace, fencing, safety and protective devices provided for by safety regulations. If necessary, install telephone, light or sound signaling communication between workplaces for supplying, receiving and laying concrete mixture.
Compaction of concrete mixture
The task of the process of compacting a concrete mixture is to limit the packing of particles of different shapes and sizes that make up a multicomponent conglomerate - a concrete mixture. The density of concrete compared to a concrete mixture with good compaction increases from 2.2 to 2.4...2.5 t/m3.
The concrete mixture is compacted by tamping, bayoneting and vibrating.
Rammers- manual or pneumatic - used when laying rigid mixtures in concrete and lightly reinforced structures, when vibrators cannot be used (for example, for fear of the impact of vibration on operating equipment).
For bayonet(pushing pieces of crushed stone hanging between reinforcement bars) when laying and vibrating mixtures with a cone draft of 4...8 cm in densely reinforced structures, screws made of reinforcing steel are used. Screws are also used to compact plastic mixtures that delaminate during vibratory laying with a cone draft of more than 8 cm.
Vibration- the main method of compacting concrete mixtures with a cone draft from 0 to 9 cm. The essence of the process is that with the help of vibrators installed on the surface or lowered into the layer of concrete mixture to be laid to a certain depth, the components of the mixture located nearby are involved in oscillatory horizontal and vertical movements developed by a vibrator with a certain inherent frequency and amplitude of oscillations
Vibration is a short process. After 30...100 s (depending on the vibration conditions), the settling of the concrete mixture stops and laitance and air bubbles appear on the surface of the compacted concrete, which indicates the end of the vibration effect. Further vibration may lead to separation of the mixture due to the sinking of large particles.
Construction of working seams
Structures are usually concreted with interruptions caused by work shifts, technological and organizational reasons. The place where, after a break, a fresh concrete mixture is laid adjacent to previously laid and already hardening concrete is called working seam.
In bending structures, working seams are located in places with the lowest shear force. In columns, seams are placed at the level of the top of the foundation, at the bottom of purlins, beams or crane consoles; in columns of beamless floors - at the bottom or top of the haunch, in frames between the post and the crossbar. In high beams monolithically connected to the slabs, the seam is made not reaching 20...30 mm to the level of the lower surface of the slab.
Concreting can be resumed after the concrete at the working joint reaches a strength of at least 1.5 MPa. This determines the duration of the breaks (18...24 hours at a temperature of +15 °C), as well as the location of the seams in accordance with the accepted installation rates. The surface of the working seam must be perpendicular to the axis of the element, and in walls and slabs - to their surface. To do this, you need to install limiter panels with slots for reinforcing bars , attaching them well to the formwork panels.
Rice. VII .24 . Construction of working seams:a B C -location of working seams when concreting columns,g, d- the same, ribbed floors;e- details of the construction seam; //-/, // - //,III -1 II - places of construction of working seams
Features of concreting structures
Columns without crossing clamps they are concreted in sections 5 m high. The concrete mixture is fed from above from a bucket through a funnel and compacted with deep vibrators. When concreting large columns, they are divided into tiers of concreting. The last tier in height is concreted after the concrete of the previous tier reaches a strength of 1.5 MPa and a working seam is installed (Fig. VII.24, A, b, V).
Columns with dense reinforcement and intersecting clamps , and also with cross-sectional sides of less than 0.4 m, they are concreted without interruptions to a height of no more than 2 m. The mixture with a cone draft of 6... ...8 cm is fed with link trunks through the holes - “pockets” (Fig. VI 1.25, V), arranged in the side walls of the formwork. It is recommended to lay a layer of plastic in the lower part of the column cement mortar 10...20 cm thick with a composition of 1: 2 (1: 3) to ensure better adhesion to previously laid concrete.
Walls, partitions and diaphragms more than 15 cm thick are concreted, feeding the concrete mixture from above through funnels and trunks continuously to a height of 3 m. The masonry is carried out in layers with a thickness equal to 0.5-0.8 the length of the working part of the vibrator tip. Walls less than 15 cm thick are concreted to a height of up to 1.5 m. For larger walls, for ease of reinforcement and laying the concrete mixture, formwork is installed on one side to the height of the tier, then reinforcement is mounted and the second side of the formwork is installed. The concrete mixture is fed from above or through pockets (Fig. VII. 25, e) and distribute it evenly (Fig. VI 1.25, d). It is recommended to concrete the walls of the tanks along the height and perimeter without interruptions. The concrete walls and bottom are joined in the places provided for by the project. Retaining walls can sometimes be concreted by supplying the mixture directly from a concrete truck (Fig. VII.25, av).
To concreting beams and floor slabs , monolithically connected to columns and walls, begin 2 hours after concreting vertical structures, so that the concrete placed in them has time to give the initial settlement. Beams and purlins with a height of less than 800 mm are concreted in layers of 35... ...40 cm simultaneously with the slabs. If the height of the beams is greater, they are concreted separately, arranging a working seam according to the height.
The concrete mixture in beams is compacted with deep vibrators with a flexible shaft, and in slabs with vibrating beams and surface vibrators. The worker sets the surface vibrator to its original position, turns on the engine and uses a hook to move the vibrator to the end of the grip, then moves it perpendicular to the track at a distance of 30...40 cm and moves it parallel to the traversed strip in the opposite direction, overlapping the previous strip by 3...5 cm The thickness of the layers of concrete mixture when laying it in slabs with double reinforcement should not exceed 120 mm, and in slabs with single reinforcement or concrete - 250 mm. The floor slabs are concreted in the direction of the secondary or main beams, feeding the mixture in the direction of the previously laid concrete.
Columns are increasingly used in the architecture of facades and interiors. It's not only beautiful decorative element, it is also a practical, utilitarian piece of construction.
It allows you to support floors or beams without taking up much usable area lower floor.
You can buy a ready-made column, but it is more convenient and cheaper to make it yourself. The easiest way is to lay it out of brick, but a monolith is much stronger and more reliable, and to make it you will have to make formwork.
Depending on the method of use, they are non-removable, disposable and reusable. They are made of metal, wood, plastic and even cardboard.
- Metal. Usually reusable. These are convenient ready-made shields that are easily and quickly assembled, provide the correct geometry, and are quickly dismantled.
- Wooden. Usually homemade, reusable. They are made from boards and bars. Cheaper, but with their help it is more difficult to ensure the correct shape, especially one other than a rectangle.
- Plastic. usually done round shapes. You can purchase ready-made ones, or you can make your own formwork from plastic pipes suitable diameter.
- Cardboard. are made of dense cardboard impregnated with special adhesives. The shape is only cylindrical, such formwork is exclusively disposable.
Ready-made formworks are offered by many manufacturers, but you can make them yourself if you take into account some of the features of this design.
Peculiarities
The column has a small width and thickness, but often has a significant height. This determines quite specific loads on the form.
The formwork experiences significant pressure in the lower part and very little in the upper part.
The elongation of the form in height makes the structure very unstable, it can easily collapse, so the formwork requires several supports.
Also, the form must have rigidity so as not to fold or bend under the weight of concrete.
It is assumed that the column will work under compression, so it is extremely important to avoid distortion of the structure. If the form is bent in an arc, then the support made in it can easily crack under load. The column can withstand bending loads very poorly.
It is very important to clearly maintain the vertical level. Even a slight deviation from the vertical creates an imbalance of loads that can lead to failure of the entire structure.
Self-assembly of the form
The easiest way to make wooden formwork for square or rectangular supports with your own hands. The sequence is:
To make the boards easier to remove later, they can be lined with oilcloth on the inside. To assemble the form, you need to choose smooth boards so that the pillars do not have bends or curvature.
Alternative options
You can also make your own mold from cardboard. But since only ordinary cardboard is available at home, to strengthen it you will need to use an additional metal reinforcing mesh or a wooden frame.
It is worth remembering that this is a disposable formwork for columns; after the concrete hardens, the cardboard will have to be torn off from it, like wallpaper from a wall.
The easiest way is to make formwork in a mesh frame. First it is taken steel mesh with square cells, not prone to stretching.
She rolls up into a cylinder required diameter, is securely fastened in this position with wire or welding.
Then folded cardboard is placed inside, which, after laying, straightens out and rests against the mesh. Finding sheets of cardboard for 2-3 meter poles is not easy, so you will have to use several sheets, fastening them overlapping each other with adhesive tape.
The structure turns out to be very unstable, so wooden supports are required.
Such disposable formwork is suitable for round columns; rectangular or square ones cannot be filled.
You can make permanent formwork from polystyrene foam with your own hands.
This option is used when facade works, it allows you to get very smooth surfaces, uniform with foam-insulated walls.
However, this permanent formwork low strength, so it also requires a supporting frame.
Price
Since everything is supposed to be done with your own hands, the price of the pole molds is determined by the cost of materials. If you make formwork from wood, then you will need to pay about 6-7 thousand rubles per cubic meter of pine.
Steel mesh will cost 20-25 rubles per square meter, thick cardboard - 200-250 rubles per roll. Polystyrene foam will cost 1000-1200 rubles per cubic meter.
When pouring columns with concrete, reinforcement work is carried out first.
We install reinforcing bars with a diameter of 12 mm in the shape of a square (in the corners). These rods are installed vertically, they are also called column rods. For ease of installation of the reinforcement frame, platforms with fences are installed every 2 m in height.
The frame is installed in several ways.
With relatively small masses and dimensions of the future column, the frame can be bent to the formwork body. If the frame turns out to be heavy (this is possible when using reinforcement with a diameter of 16 mm or more), then it is more effective to assemble only the base separately, and fasten it already at the pouring site. When ligating or welding, standing on the rods being welded is prohibited. When welding, it is most convenient to use a portable welding machine. Choose welding inverter Can . The reinforcements can be welded together with wire, at a distance of 40-50cm. For such purposes, you can use a special gun for tying reinforcement.
We install the formwork.
First, we assemble the formwork body. Special attention it is worth paying attention to its fastening. The formwork is secured during installation with everyone sides of the future column (for a standard column - from four).
We install wooden spacers on each side of the future column. If the column turns out to be high, then a slightly different method is used. The box body is mounted on three sides, and the latter is increased directly during concreting. During installation, the box is leveled and fastened with screws. Corners are mounted on the sides to maintain a right angle of 90 degrees.
Concreting process.
One of the most important parameters when pouring concrete into columns is the mobility of the concrete mixture. Mobility refers to the ability of concrete to be distributed under the pressure of its mass. To measure mobility, use a concrete cone. It is filled with concrete layer by layer. After which it is lifted and the mixture settles under its own weight. How much the cone will sag, such mobility can be assigned mobility. There are flexible and rigid concrete mixtures. Mobility is marked with the letter “P” and a number from 1 to 5.
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Draft |
Designation |
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From 10cm to 15cm | |
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From 16cm to 21cm | |
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More than 22cm |
When pouring columns, P2 or P3 concrete is used. And when large quantities reinforcement - P4 or P5 (cast concrete). It is excellent for pouring into formwork, without the use of an internal vibrator with a flexible shaft. As pouring progresses, mobility increases.
Pouring is done using a concrete pump or, as it is also called, a bell. To do this, remove the tray from the tub and install a funnel in its place. We install a tarpaulin sleeve on it with a clamp for pouring concrete. And we put its free end into the formwork.
Filling is done in layers. The layers go horizontally and STRICTLY in one direction. As the mixture is filled, it must be thoroughly compacted, removing excess air from the mixture. To do this, the mixture is pierced evenly throughout the entire volume using a metal rod. After this, you need to walk with a vibrator. Be sure to make sure it is grounded.
If it is not possible with a flexible shaft, then you can periodically tap the formwork with a hammer or rubber mallet. During the process, be sure to ensure that the formwork does not “go away” anywhere, and the reinforcement frame always remains strictly in the center.
Composition of the concrete mixture: 1 part M400 cement, 2 parts sand, 4 parts gravel or crushed stone (size from 20mm), and water. The amount of water is taken based on obtaining a homogeneous mass. When the column is poured, reinforcement is attached to it using anchors.
We remove the formwork.
When the concrete reaches full strength, the formwork is removed. Typically full strength concrete mixtures achieved between 20 and 25 calendar days subject to optimal conditions solidification.
In modern monolithic construction columns are used quite often. In many projects of multi-storey buildings they are not only decorative architectural elements, but also the main load-bearing structures the entire building. This allows you to build premises on the next floor without repeating the plan of the previous one. To ensure the strength and durability of such monolithic buildings, the formwork of the columns must be made reliably and efficiently.
Types of columns and formwork for their arrangement
By geometric shape All column sections are divided into:
- round (cylindrical);
- square or rectangular;
- multifaceted;
- curly.
The most widespread are the columns of the first two types. The last two categories are used mainly for restoration of buildings or decorative purposes.
Based on the number of cycles of use, formwork for arranging columns is divided into:
- disposable;
- reusable.
Depending on the material of manufacture, the formwork is:
- wooden;
- plastic;
- metal;
- cardboard;
- combined.
Formwork for cylindrical columns
Formwork for round columns can be either disposable or reusable.
Cardboard tubes are now often used as disposable formwork for round columns. In their production they use paper tape, a special adhesive composition And polymer material(to ensure waterproofness). This column formwork is produced with internal diameter from 150 to 1200 mm. Its installation is quite simple: the pipe is simply placed on the reinforcement frame, then support rings are installed, to which spacer struts are attached (to provide stability and vertical alignment). To quickly dismantle such products during their manufacture, a special metal wire is pressed along the entire length of the pipe, pulling which cuts the cardboard along its entire length, and then it is easily separated from the hardened concrete.
On a note! It is advisable to dismantle the cardboard pipe just before the end of construction. This will protect the support from technological damage.
Disposable formwork for columns made of cardboard has a number of undoubted advantages:
- low cost;
- ease of installation and dismantling;
- when using it, the surface concrete support turns out to be of high quality;
- light weight;
- high strength.
As non-removable elements round section use pipes (metal, asbestos-cement or plastic). This, after the concrete solution has hardened, remains an integral part of the column structure.
Attention! Using metal pipes their surface must be treated with an anti-corrosion compound.
Reusable round formwork consists of metal or plastic half-pipes, which are mounted around the column reinforcement frame using special quick-release fasteners. Plastic column formwork has less adhesion to concrete compared to metal formwork (this ensures ease of dismantling), but less strength.
Formwork for square and rectangular columns
This type of column is most widely used in both industrial and individual construction.
The most common type removable formwork for the arrangement of such columns - a large-panel formwork system. Universal panels (their dimensions: width – 0.4÷1.2 m, height – 1.0÷3.3 m) allow you to quickly install formwork for square columns(the cross-section of which is from 0.2⨯0.2 m to 1.0⨯1.0 m).
Longitudinal technological holes for fastening elements (pins) allow you to create formwork rectangular section. For one column you need: shields (4 pieces, assembled in a “mill”), kingpins with special tightening nuts (for a column about 3 meters high, as a rule, 16 sets are sufficient) and slopes (at least 2 two-level support ones).
The popularity of this system is due to:
- simplicity and high speed of installation and dismantling;
- the ability to form a column section in accordance with the requirements of the project;
- durability (from 80 to 200 concreting cycles, depending on the manufacturer and material of the panels).
Another common one in modern construction The type of formwork system for the construction of columns is beam-transom. The main elements of such a structure are formwork slabs, steel crossbars, beams of various sizes and fasteners. This type of formwork system can be easily adapted to create square, rectangular and even octagonal columns. Such steel formwork columns have the greatest strength and durability compared to other materials ( laminated chipboard, plastic or boards and plywood).
Self-production of formwork for the construction of columns
When making formwork for monolithic columns with your own hands, you can use several methods.
The simplest method (however quite labor-intensive) for making a formwork frame for columns of square or rectangular cross-section:
- Using boards (25 mm thick and a length equal to the height of the column), using nails and screws, we make a U-shaped structure with internal dimensions corresponding to the cross-section of the future column.
- We make a shield from the same boards, which will subsequently become the fourth side of the formwork frame.
- We install a U-shaped structure to reinforcement cage and attach a shield of boards to it.
- We level the formwork vertically using a level and secure it with stops made of boards or bars.
- To give the structure additional strength, we tighten it using additional bars and studs with nuts.
- Now you can start pouring the concrete mixture.
The video will help you understand the above-described technology for manufacturing formwork for square columns:
Another way to self-made is largely similar to the previous one. Instead of boards for making formwork (preferably moisture-resistant, 12 mm thick) and wooden blocks. We use reinforcing bars and quick-release spring locks (clips) as tightening elements. To align vertically, you can use telescopic stands rented.
On a note! It is advisable to use the above methods if it is necessary to produce a small number of columns (3÷4 pieces). Otherwise, the cost of materials and hardware for the manufacture of formwork will be quite high. If you need to build 10÷12 columns (for example, for a large glass terrace or verandas), then the formwork of columns on universal panels, rented (the cost of renting one set, which includes: 4 panels, 2 two-level telescopic slopes, a set of necessary fasteners, will be about 7,500 rubles per month). And since the column can be stripped within 48 hours after pouring the concrete solution, you can easily make required amount columns
In custody
The final choice of one or another type of formwork for the manufacture of columns depends on their number, section size and height. Of course, only high-tech professional formwork systems are used for the construction of bridge or overpass supports. And for the construction of several not very high columns during individual construction, you can completely get by with a form made from scrap materials. The main thing is that it strictly corresponds to the geometry of the future column and can withstand the pressure of the concrete solution without deformation.