When the columns are poured with concrete, reinforcement work is performed at the beginning.
We install reinforcing rods with a diameter of 12mm in the form of a square (at the corners). These rods are installed vertically, they are also called column rods. For the convenience of mounting the reinforcement cage, platforms with fences are installed every 2m of height.
Installation of the frame is carried out in several ways.
With relatively small masses and dimensions of the future column, the frame can be turned over 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 efficient to assemble only the base separately, and fasten it already at the pouring point. When carrying out bandaging or welding, it is forbidden to stand on the rods to be welded. When welding, it is most convenient to use a portable welding machine. You can choose a welding inverter. Reinforcement bars can be welded together with wire, at a distance of 40-50 cm. For such purposes, you can use a special rebar tying gun.
We install the formwork.
First, we assemble the formwork body. Particular attention should be paid to its fastening. The formwork is fixed during installation with of all sides of the future column (with a typical column - from four).
We mount wooden spacers on each side of the future column. If the column is high, then a slightly different method is used. The box body is mounted on three sides, and the latter is built up directly during concreting. During installation, the box is leveled and fastened with screws. On the sides, corners are mounted to maintain a right angle of 90 degrees.
Concreting process.
One of the most important parameters when pouring concrete into columns is the flowability of the concrete mix. Mobility refers to the ability of concrete to distribute itself under the pressure of its mass. A concrete cone is used to measure the mobility. It is filled with concrete in layers. Then it is lifted and the mixture settles under its own weight. How much the cone sags, such mobility can be assigned to mobility. Distinguish between mobile 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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10cm to 15cm | |
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16cm to 21cm | |
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More than 22cm |
When pouring the columns, concrete P2 or P3 is used. And with a large number of reinforcement - P4 or P5 (cast concrete). It is perfect for casting into formwork without using a flexible shaft vibrator. Mobility increases as the fill proceeds.
Filling is done using a concrete pump or or as it is also called a bell. For this, the tray is removed from the bucket, and a funnel is installed in its place. On it with a clamp we install a canvas sleeve for pouring concrete. And put its free end into the formwork.
Filling is done in layers. The layers run horizontally and STRICTLY in one direction. As it fills, the mixture must be carefully compacted by removing excess air from the mixture. To do this, the mixture is pierced evenly throughout the volume with a metal rod. After that, you need to walk with a vibrator. Be sure to make sure it is grounded.
If there is no possibility with a flexible shaft, then you can periodically tap on the formwork with a hammer or rubber mallet. In the process, be sure to make sure that the formwork does not "go away" anywhere, and the frame from the reinforcement always remains strictly in the center.
The composition of the concrete mixture: 1 part of M400 cement, 2 parts of sand, 4 parts of gravel or crushed stone (size from 20mm), and water. The amount of water is taken from the calculation of obtaining a homogeneous mass. When the column is poured, reinforcement is attached to it using anchors.
We remove the formwork.
When the concrete gains full strength, the formwork is removed. Typically, the full strength of concrete mixtures is achieved in the period from 20 to 25 calendar days, subject to the optimal setting conditions.
Columns are increasingly used in the architecture of facades and interiors. It is not only a beautiful decorative element, it is also a practical, utilitarian piece of construction.
It allows you to support ceilings or beams without taking up much of the usable area of \u200b\u200bthe lower floor.
The column can be bought ready-made, 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 for its manufacture you will have to make a formwork.
According to the method of use, they are non-removable, disposable and reusable. They are made of metal, wood, plastic and even cardboard.
- Metallic. Usually reusable. These are convenient ready-made shields that are easy and quick to assemble, provide the correct geometry, and are quickly dismantled.
- Wooden. Usually self-made, reusable. Get knocked out of planks and bars. Cheaper, but more difficult to provide the correct shape, especially one other than a rectangle.
- Plastic. usually round shapes are made. You can buy ready-made, or you can make a formwork from plastic pipes of a suitable diameter with your own hands.
- Cardboard. are made of dense cardboard impregnated with special adhesives. The form is only cylindrical, such formwork is exclusively disposable.
Ready-made formworks are offered by many manufacturers, however, they can be made independently, taking into account some of the features of this construct.
Features:
The column is small in width and thickness, but often has a significant height. This determines quite specific loads on the form.
The formwork is under significant pressure at the bottom and very little at the top.
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, not to bend under the weight of the concrete.
It is assumed that the column will work in compression, so it is extremely important to avoid distortion of the structure. If the form bends in an arc, then the support made in it can easily crack under load. The column withstands bending loads very poorly.
It is very important to maintain a clear vertical level. Even a slight deviation from the vertical creates an imbalance in the loads that can lead to failure of the entire structure.
Self-assembly of the form
The easiest way to make a wooden formwork for square or rectangular supports is with your own hands. The sequence is as follows:
To make the boards easier to remove later, they can be upholstered from the inside with oilcloth. To assemble the form, you need to choose flat boards so that the posts do not have bends, curvatures.
Alternative options
You can also make a form from cardboard yourself. 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 has hardened, the cardboard will have to be ripped off like wallpaper from the wall.
The easiest way is to make the formwork in a mesh frame. First, a square mesh steel mesh is taken that does not tend to stretch.
It rolls up into a cylinder of the required diameter, is securely fastened in this position by wire or welding.
Then rolled cardboard is placed inside, which, after laying, straightens and rests against the grid. Finding sheets of cardboard for 2-3 meter posts is not easy, so you will have to use several sheets, fastening them between the overlap with adhesive tape.
The design is very unstable, so wood supports are required.
Such disposable formwork is suitable for round columns, rectangular or square cannot be poured in any way.
You can do it yourself with a fixed formwork made of polystyrene foam.
This option is used for facade work, it allows you to get very flat surfaces, uniform with walls insulated with foam plastic.
However, this fixed formwork is not strong enough and therefore also requires a supporting frame.
The cost
Since everything is supposed to be done by hand, the price of the forms for the posts is determined by the cost of materials. If you make timber formwork, then you will need to pay about 6-7 thousand rubles for a cubic meter of pine.
Steel mesh will cost 20-25 rubles per square meter, thick cardboard - 200-250 rubles per roll. Polyfoam will cost 1000-1200 rubles per cubic meter.
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 supporting structures of 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 structures, the column formwork must be performed reliably and efficiently.
Varieties of columns and formwork for their arrangement
According to the geometric shape of the section, all columns 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 mainly used for building restoration or decorative purposes.
According to the number of cycles of use, the formwork for arranging the columns is divided into:
- disposable;
- reusable.
Depending on the material of manufacture, the formwork is:
- wooden;
- plastic;
- metal;
- cardboard;
- combined.
Cylindrical Column Formwork
Round column formwork can be either disposable or reusable.
Cardboard pipes are now quite often used as disposable formwork for round columns. In their manufacture, paper tape, a special adhesive and polymer material (to ensure water resistance) are used. This column formwork is available with an inner diameter of 150 to 1200 mm. Its installation is quite simple: the pipe is simply put on the reinforcing cage, then the support rings are installed, to which the spacer braces are attached (to give stability and vertical alignment). For quick dismantling of such products during their manufacture, a special metal wire is pressed along the entire length of the pipe, pulling on which the cardboard is cut 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 of the concrete support is obtained of high quality;
- light weight;
- high strength.
Pipes (metal, asbestos-cement or plastic) are used as non-removable elements of circular cross-section. After the concrete solution hardens, this remains an integral part of the column structure.
Attention! When 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 cage using special quick-release locks. The plastic formwork of the columns has less adhesion to concrete than metal (this provides 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 of removable formwork for arranging such columns is the large-panel formwork system. Universal panels (their dimensions: width - 0.4 ÷ 1.2 m, height - 1.0 ÷ 3.3 m) allow you to quickly mount the 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 fasteners (pins) allow you to create rectangular formwork. One column requires: shields (4 pieces, assembled into a "mill"), pivots 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 such a system is due to:
- simplicity and high speed of assembly and disassembly;
- the possibility of forming the section of the column in accordance with the requirements of the project;
- durability (from 80 to 200 concreting cycles, depending on the manufacturer and the material of the panels).
Another type of formwork system that is widespread in modern construction during the construction of columns is beam-transom. The main elements of this design are formwork plates, steel girders, beams of various sizes and fasteners. This type of formwork system can be easily adapted to create columns with square, rectangular and even octagonal cross-sections. Such steel column formwork has the greatest strength and durability compared to other materials (laminated chipboard, plastic or boards made of plywood and boards).
Self-production of formwork during the construction of columns
In the manufacture of formwork for monolithic columns with your own hands, you can use several methods.
The easiest way (but rather laborious) to make a formwork frame for columns of a square or rectangular cross-section:
- From planks (25 mm thick and equal to the height of the column), using nails and self-tapping screws, we make a U-shaped structure with internal dimensions corresponding to the section of the future column.
- We make a shield from the same boards, which will later be the fourth side of the formwork frame.
- We install the U-shaped structure to the reinforcing cage and attach a board made of boards to it.
- We align the formwork vertically using a level, and fix it with stops made of boards or bars.
- To give the structure additional strength, we tighten it with 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 the formwork of square columns:
Another method for self-manufacturing is in many ways similar to the previous one. Instead of boards for the manufacture of formwork (preferably moisture resistant, 12 mm thick) and wooden blocks. We use reinforcing bars and quick-clamping spring locks (clips) as tightening elements. For vertical alignment, you can use rented telescopic stands.
On a note! The above methods are advisable to apply if it is necessary to make 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 glazed terrace or veranda), then the column formwork 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 stripping of the column can be done within 48 hours after pouring the concrete solution, then for the paid month you can easily make the required number of 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 supports or flyovers. And for the construction of several not very high columns with 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.
Composition of the process, preparation for concreting
During concreting, the mixture fills all the gaps between the reinforcement rods, forms a protective layer of the required thickness and is compacted with the corresponding specified density and grade of concrete.
Concreting consists of preparatory and verification operations, the laying process, containing 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 from debris and dirt with a jet of water or compressed air. The surfaces of the wooden formwork are wetted. The slots in the wooden formwork with a width of more than 3 mm are sealed to prevent the flow of cement laitance. The surfaces of the steel and plastic formwork are coated with a lubricant, for example, waste oil, and the reinforced concrete reinforced cement or asbestos-cement formwork-facing is washed with a stream of water. The fittings are cleaned from dirt and rust. At the same time, they carry out work on setting up mechanisms, machines and devices used in all interconnected concreting operations. The necessary equipment is installed at the workplace, fences, safety and protective devices provided for by safety precautions are arranged. If necessary, equip a telephone, light or sound signaling connection between the workplaces for the supply, reception and placement of concrete mix.
Concrete compaction
The task of the process of compaction of a concrete mixture is the ultimate packing of particles of various shapes and sizes that make up a multicomponent conglomerate - concrete mixture. The density of concrete in comparison with the concrete mixture with its good compaction increases from 2.2 to 2.4 ... 2.5 t / m 3.
The concrete mix is \u200b\u200bcompacted by tamping, bayonetting and vibration.
Rammers- manual or pneumatic - used when laying rigid mixtures in concrete and low-reinforced structures, when vibrators cannot be used (for example, for fear of the effects of vibration on operating equipment).
For bayonet(pushing pieces of crushed stone hanging between the reinforcement rods) when laying and vibrating mixtures with a cone draft of 4 ... 8 cm in densely reinforced structures, reinforcing steel skins are used. Skewers are also used to seal plastic mixtures stratified during vibration laying with a cone draft of more than 8 cm.
Vibrating- the main method of compacting concrete mixtures with a cone settlement of 0 to 9 cm.The essence of the process is that with the help of vibrators installed on the surface or lowered into the concrete layer to be laid to a certain depth, the components of the mixture located near are involved in horizontal and vertical vibrational movements developed by the vibrator with a certain inherent frequency and amplitude of the
Vibrating is a short process. After 30 ... 100 s (depending on the vibration conditions), the settling of the concrete mixture stops and cement milk and air bubbles appear on the surface of the concrete being compacted, which indicates the end of the vibration effect. Further vibrations can lead to stratification 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, the fresh concrete mixture is laid close to the previously laid and already hardening concrete is called working seam.
In bent structures, the working seams are located in places with the lowest shear force. In the columns, the seams are arranged at the level of the top of the foundation, at the bottom of the girders, beams or crane consoles; in columns of flat slabs - 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 arranged, not reaching 20 ... 30 mm to the level of the lower surface of the slab.
It is possible to resume concreting 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 laying rates. The surface of the working joint should be perpendicular to the axis of the element, and in walls and slabs - to their surface. To do this, you need to install shields-limiters with slots for reinforcing bars. , well attaching them to the formwork panels.
Figure: Vii .24 ... Construction of working seams:a B C -arrangement of working seams when concreting columns,d, d- the same, ribbed floors;e- details of the working seam device; / - /, // - //,III -1 II - places of construction of working seams
Features of concreting structures
Columns without crossing clamps concreted in sections 5 m high. The concrete mixture is fed from the top of the bucket through a funnel and compacted with deep vibrators. When concreting columns of great height, a breakdown is made into concreting tiers. The last tier is concreted in height after the concrete reaches the previous tier with a strength of 1.5 MPa and the device of the working seam (Figure VII.24, and,b, in).
Columns with thick reinforcement and criss-cross clamps , and also with cross-sectional sides of less than 0.4 m, 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 holes - "pockets" (Fig. VI 1.25, in),arranged in the side walls of the formwork. It is recommended to lay a layer of plastic cement mortar 10 ... 20 cm thick with the composition 1: 2 (1: 3) in the lower part of the column in order to provide better adhesion to the previously laid concrete.
Walls, partitions and stiffening diaphragms with a thickness of more than 15 cm, they 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 of the length of the working part of the vibrator tip. Walls with a thickness of less than 15 cm are concreted up to 1.5 m in height.With a higher wall height, for the convenience of reinforcing 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 mix is \u200b\u200bfed from above or through pockets (fig. VII.25, e)and evenly distribute it (Fig.VI 1.25, e).The walls of the tanks are recommended to be concreted along the height and perimeter without interruption. The concrete walls and bottoms are joined in the places provided by the project. Retaining walls can sometimes be concreted by feeding the mixture directly from the concrete truck (Fig. VII.25, ab).
To concreting beams and floor slabs , monolithically connected with columns and walls, proceed 2 hours after concreting vertical structures, so that the concrete laid in them has time to give an initial draft. Beams and girders with a height of less than 800 mm are concreted in layers of 35 ... ... 40 cm simultaneously with the slabs. With a greater height of the beams, they are concreted separately, arranging a working seam in 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 moves the vibrator with a hook to the end of the grapple, 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 the concrete mixture when it is laid in slabs with double reinforcement should not exceed 120 mm, and in slabs with single reinforcement or concrete - 250 mm. Floor slabs are concreted in the direction of the secondary or main beams, feeding the mixture in the direction of the previously placed concrete.