- Date: 18-01-2018
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- Features of the preparatory work
- Concrete delivery from height
- Concreting of structures and elements
- Sealing plates with rare reinforcement
- Acceleration of concrete hardening
- How to prepare formwork?
- When to remove formwork?
- Materials and tools
Before you start laying concrete mix into the formwork, it is important to check the serviceability of the structure, fastening the formwork, inspect the scaffolding, lining, and joining.
Before laying concrete in the formwork, you need to check if there are any cracks in the structure.
When laying concrete in the formwork, there are a number of requirements that must be met.
Often gaps are found in the formwork, which must be repaired without fail. After inspection and repair, the concrete formwork must be cleaned of dirt, wood chips and other debris. It is important to thoroughly moisten the formwork with water. If this is not done, then the laid concrete will give moisture to the dry construction boards.
Scheme of conventional foundation formwork.
The reinforcement used must also be free of adhering soil if it was stored outdoors. Checks if plugs and anchor bolts are installed correctly. Make sure the quality of the binding. Concrete is laid quickly, without stops, any delays in this process are highly undesirable. Each subsequent concrete layer is laid and compacted before the previously laid layer begins to set. At the same time, it is known that during concreting, interruptions in work are difficult to avoid.
In this case, the working seams are left in place, the formwork design has the lowest voltage. For example, when concreting columns is performed, you can leave a working seam only at the beginning of the column. Sometimes it is located under the upper floor, under the run. When ribbed floors are concreted, the joints in the direction of the runs can be left in the middle of the run of the run, near the middle of the span of the slab, since there are no bent rods. Concrete formwork is always given maximum attention, the result of work depends on it.
Features of the preparatory work
If the floors are beamless, the seams should be arranged at the middle of the span. As for wall joints, they can be done directly at the ceiling. It is impossible to arrange inclined seams.
Any formwork for a strip foundation should be easily dismantled after concrete has hardened.
Sometimes it happens that the concrete mix still has to be laid on a layer that has long been set or is old. In this case, before starting work, the surface of the old concrete is thoroughly cleaned. For this, special wire steel brushes are used.
Often carrying out such work is large-scale, it is required to clean a significant surface. You can’t do anything at hand, therefore it is advisable to use grinders or special sandblasting machines.
During the preparatory work of this type, shells or other defects are often found in the old concrete layer. In this case, it is necessary to cut down the surface layer of the old concrete coating without affecting the reinforcement. If there are areas of exposed reinforcement, you need to clean it properly, eliminate rust and particles of the old concrete. The next step is to wet the old surface with cement milk. Only after these actions can we begin laying concrete, a new layer. Its brand should not be lower than that used previously for the old layer.
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During construction work, concrete often has to be fed from above, and such methods suggest that the height is significant. In the event that the height is more than 2 m, then the concrete should be lowered into the formwork using special trays having an inclined position. You can use the gutters with visors. If concrete is supplied from a height of 3 m, trunks with an inclined position are arranged. The angle of inclination is 30 °. If the concrete mixture enters the formwork, located in a radius of 15 m, then the feed is made by means of metal shakers.
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Scheme filling formwork.
Concrete mixture is compacted using vibrators. During this action, air is displaced, the bubbles are pushed out, and the volume of concrete becomes smaller. The vibrator should be immersed in concrete smoothly, with a slight slope. After the vibration of one section is completed, the vibrator is moved to another place. It is important that the vibrator compacts the entire area occupied by concrete so that voids called sinks do not appear in the concrete.
If vibration of the newly laid layer is required, the vibrator should be immersed in the concrete mixture so as not to reach the underlying layer. Otherwise, the structure of the mixture may be disturbed. Vibration should be carried out at a certain distance from the walls of the formwork. It is usually enough to leave 10 cm. If the concrete mix is normally compacted, cement milk forms on its surface and around the vibrator platform.
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The construction of a monolithic foundation using elements of wall formwork.
The process of concreting any structures always takes into account design features and a number of requirements. At a column height of more than 3 m, the concrete mixture is compacted in layers, tiers through windows located at the column height with intervals of 1.5 m. In this case, the concrete layer should not be more than 0.5 m. The layer is compacted with a vibrator for about 20 seconds. As a rule, columns are concreted at the same time as the beams that adjoin them and with floor slabs.
After concreting is completed, 2 hours are allowed for concrete sedimentation in the column. Next, adjacent elements begin to concrete. Partitions and walls with a thickness of up to 20 cm are concreted in tiers, the height of which can reach 1.5 m, then compacted. For concreting beams and girders, a layer of up to 50 cm is taken. After sufficient compaction of the concrete mixture, the lighthouse rails are removed. The recesses remaining after them require careful compaction with the concrete mixture and careful smoothing.
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Removable removable formwork.
If the surface of the slabs is more than 25 cm or they have rare reinforcement, then the seal is made in the same way as for densely reinforced foundations. The same goes for plates with a thickness of more than 25 cm with double reinforcement. After the vibration is completed, the upper surface of the foundation should be leveled with a vibrating bar, then smoothing with a wooden battens is performed. The floor is concreted with exposed beacons that determine its level. Given the lighthouses, a layer of concrete is applied, 20 mm higher than the height of the lighthouse. Compaction of the concrete mixture must be carried out until the moment when the cement milk begins to appear, and the concrete drops to the level noted by the beacons.
The best option is to lay concrete in strips (with a width of 1 m). If it is necessary to concrete thin-walled reinforced concrete structures saturated with reinforcement, such as tanks, arches, silos, the concrete laying process is provided continuously. Start from the bottom and further along the perimeter, in strips or layers not exceeding 0.5 m. For vibration, high-frequency shuttering vibrators are used.
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To speed up the process of hardening the concrete mixture, vacuum the concrete. From the freshly laid mixture, excess water and air are aspirated. For this, special vacuum chambers are used. Thanks to this technique, the hardening process of concrete can be accelerated by almost 50%. When the concrete gains the necessary strength, it needs to be freed from the formwork. One of the most common mistakes is premature formwork. In this case, there is a high risk of damage to the concrete structure.
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Scheme of formwork steps with an additional block.
Before laying concrete, the surface of the formwork should be coated with grease. If the formwork is made of wood, then a grease made from kerosene and petrolatum is used, the proportion by weight can be 3: 1 or 2: 1. When preparing such a lubricant, the petrolatum is heated to a droplet-liquid consistency. After that, kerosene and solar oils are added to it. If the surface of the structure does not require finishing, as is the case with the foundations of buildings or hydraulic structures, it is permissible to use used machine oil. Impregnation with phenolic-epoxy varnishes, phenolic resins, liquid bakelite resins can increase the turnover of wooden formwork.
When laying, the mobility and stiffness of the concrete mixture should be selected in accordance with the features of the fabricated structure. In particular, the working conditions, the initial data incorporated in the calculation of the formwork are taken into account. After the mixture is laid into the formwork, moisture mainly evaporates from the concrete surface, so the top layer of the structure may be dehydrated. In this regard, the water-cement ratio is unsecured, and the design strength is absent.
To prevent such a defect, the surface of the freshly laid concrete mixture must be protected from intense evaporation. The easiest way is to water, cover with plastic wrap, mats and other means. The state of constant humidity of concrete should be maintained up to 7 days after its laying.
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Side formwork of walls, beams, columns, foundations is removed in the case when the edges of the corners and the surface of the concrete structure during formwork remain unbroken. Such signs mean that the concrete mixture has acquired the necessary strength, you can continue to form. In the summer season, when the air temperature is within 20 ° C, you can start stripping in 2 days. If the weather is cooler, it will take at least 5 days. The stripping of arches and slabs, the span of which is up to 2 m, begins when concrete acquires at least 50% of its design strength. The stripping of beams and bottoms, the span of which is within 8 m, begins when concrete reaches 70% of its design strength.
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Scheme of installation of reinforcement from flat reinforcing frames and nets and formwork of strip foundations.
When laying concrete, it is important that there are no voids, so special attention is paid to leveling. This process can be greatly facilitated if the supply of concrete mix to any part of the concrete structure is ensured. When the mixture is stacked, it is very undesirable to throw it over. Such actions are permissible only in extreme cases. Moreover, you can not allow a double transfer of the mixture. The shape of the cone formed during unloading of the mixture is due to the stiffness and mobility of the concrete mixture. With increased stiffness, the slope of the cone is steep; with high mobility, the cone is more gentle. You can level out manually or use a small bulldozer.
Regardless of how the mixture is delivered to the place of installation, it is not recommended that it be delaminated. From the moment of unloading from the concrete mixer to the laying of the mixture in the formwork, a maximum of 40 minutes must pass. It is important to monitor the cleanliness of all equipment used. The mixture should have high ductility, easy to fit between reinforcement and formwork. If the concrete has acquired a semi-hardened state, then it is not suitable for laying.
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To lay concrete in the formwork you will need:
Stages of removing formwork from a column foundation.
- Formwork of the required size and shape.
- Concrete mix.
- Shovels shovels.
- Water source.
- Devices for leveling concrete mix laid in formwork.
- Special trays for conveying concrete from a height.
- Formwork lubricant.
- Polyethylene film (to protect the surface of the mixture from evaporation).
- Vibrators for compaction of concrete mix.
- Protective gloves, overalls.
It is best to mix the concrete mix as close to the formwork as possible. When working with concrete, it is imperative to wear protective gloves, since contact of the concrete with the skin can cause burns and irritation.
High-quality concrete laying
- How concrete is laid using formwork
- Practical recommendations
- How to compact concrete
Depending on the purpose and nature of the construction work, concrete can be laid in two main ways. In the first method, collapsible or non-collapsible formwork is used, and in the second method, the prepared concrete mixture is poured directly into the ground.
Concrete laying scheme.
Most of all, the second method is suitable for screeds or bulk floors made of concrete, a monolithic foundation of a strip type and garden paths, as well as for some other types of structures where walls or the soil act as a kind of formwork. Laying concrete mixture in the formwork is a more complex and responsible process, which requires certain skills.
How concrete is laid using formwork
When laying concrete in a formwork of a collapsible or non-collapsible type, a certain technology must be strictly observed, since in the opposite case, defects and errors may appear in finished concrete structures after some time. It is very important to prevent even the slightest delamination of the mixture.
Starting the installation process, it is necessary to thoroughly rinse all the materials used (in particular formwork and fittings) with water so that they do not leave any traces of dirt, debris, oils, bitumen and other elements. In addition, the fittings should not have the slightest signs of corrosion - if they are, they should certainly be eliminated.
There is a whole range of important measures that will help to lay concrete as efficiently and efficiently as possible. Unloading of the concrete mixture should be carried out near the place of the planned laying so that it does not have to be moved: this will prevent undesired delamination, insufficient compaction and pore formation. Layers of concrete should be laid exclusively in the horizontal direction, while each of them must be carefully compacted before proceeding with the construction of the subsequent layer. It is desirable that during the laying of concrete layers no breaks are allowed, otherwise undesirable seams may form that not only have an unpresentable appearance, but also lead to some weakening of the entire structure.
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Table of approximate correspondence of class and grade of concrete.
The thickness of the concrete layer can be different: it depends on the consistency of the mixture, the method of compaction, the shape and size of the element, which must be concreted and some other factors. The optimal concrete thickness for reinforced concrete structures is from 15 to 30 cm. And if it is necessary to concrete larger and larger massifs, the layer must be made thicker: from about 37 to 47 cm.
The entire space in the corners of the formwork, around the embedded parts and fittings should be carefully filled with a mixture of concrete. It is desirable that the upper part of the concrete layer be made of a more rigid and solid mixture: firstly, this will compensate for the increased amount of water that forms on the surface during compaction of the layer, and secondly, the concrete consistency will become more uniform.
If the concrete mixture is to be laid in a sufficiently deep trench or in some other place, which is characterized by regular seepage of water, it is advisable to carry out the concreting process in separate sections. To do this, first of all, it is necessary to thoroughly drain the small area, fill it with a high-quality cement mortar and immediately after that lay the concrete layer. Exactly the same way you should process the remaining areas. In addition, it is desirable to install pipes for drainage - this will significantly improve the situation.
In order for the concrete to be laid without unpleasant surprises, it is necessary to take care of the strength of the formwork used: it must ideally withstand the concrete mass, which is characterized by increased weight and fluidity. Thanks to the competent selection and use of metal reinforcement, it is possible not only to effectively strengthen concrete by bending and stretching, but also significantly reduce the consumption of this material.
There are two main ways that concrete is laid: using a construction mixer or a special tub, having a triangular shape and equipped with a valve.
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After the entire concrete mixture has been completely laid, it must be densified.
Determination of the readiness of the solution.
The best method for this is to use a special electric vibrator. As a result of its use, the density and strength of the concrete mixture is significantly increased. All rubble that is present in this mass is actively compacted, as a result of which air bubbles begin to rise.
Quite often used and manual methods of compaction.Compared to the previous one, they are less effective, but also cheaper. The main manual methods include ramming and baying - they are used for different types of concrete. For hard concrete, tamping is most suitable, while for plastic and cast ones, baying. Rigid concrete is rammed with a piece of timber or log, the weight of which can be from 15 to 30 kg. To use it more conveniently, it is recommended to attach special handles to it. And in order to protect this wooden product from undesirable crushing or soaking, its lower surface should be covered with metal plates. For plastic concrete, a thin long pipe or pin is used - it is immersed in the mixture to a certain depth, and then they begin to move intensively to the sides. Such actions must be done over the entire surface of the concrete mixture.
If it is necessary to compact larger areas, it is recommended to use special vibration platforms that are characterized by increased productivity. After processing, the concrete must be covered with burlap for some time and do not forget to periodically saturate it with moisture.
On this web page, we suggest that you familiarize yourself with the basic rules and techniques for laying concrete mix.
Good to know: Schemes of typical foundations of low-rise housing construction
The concrete mixture must be laid in ways that ensure the monolithic and uniformity of concrete, adhesion to reinforcement and embedded parts, and filling the construction space with concrete.
Please note that Starco LLC has the ability to perform concrete work at your facility.
Concrete laying in the structure to be concreted is carried out only after checking the technical condition of the formwork, reinforcement, embedded elements.
- If laying in wooden formwork is carried out, then immediately before laying concrete, its sides and base are abundantly moistened with water, the cracks are caulked. This is done so that the formwork boards cannot absorb water from the mixture, which will lead to a decrease in the water-hard ratio in the concrete mix, and as a result, to a decrease in its workability and ductility. The height of the concrete mixture falling into the formwork should not exceed two meters.
- Concrete is laid in horizontal layers having a height of up to 50 cm. Moreover, the layers are laid in the same direction and should have a relatively equal height. The concreting process must go on continuously. In this case, the laying of the next layer is done before the setting of the previous one begins.
On large casting massifs, it is sometimes difficult to fill in the next concrete layer before setting the mixture. Then apply the step-by-step method of laying with the simultaneous laying of two or three layers, while the length of the "step" should be at least 3 meters.
The device of working seams
If necessary, breaks in concrete structures, use the so-called working seams.
Working seam - the transition plane between the hardened (old) and the new (freshly laid) concrete layer, formed due to a temporary break in laying. The working seam is formed when subsequent layers of the mixture are laid on the hardened previous layers.
The working seam is a weakened place of the structure, so they should be arranged in places where the joints of concrete can not significantly affect the strength of the structure.
The plane of the working seam should be perpendicular to the axis of the pouring element, and in the walls and plates - their planes.
To bond different layers in the working seam, the surface of a previously laid concrete layer must be carefully prepared:
- the edge of the set concrete layer is cleaned of cement film and the coarse aggregate is exposed, using wire brushes, blown with air and washed with water.
- they carefully treat the surface of the concrete around the reinforcement, the reinforcing bars are cleaned of the solution.
- Before concreting, the cleaned joint surface is covered with a cement mortar of the same composition (hardness, density) as the concrete mixture to be laid.
In order for the design to be monolithic and uniform in composition, the mixture must be compacted after laying. One of the most common compaction methods is vibrating concrete.
Good to know: DIY concrete
During transportation and laying process, the concrete mixture is in a loose state, the particles of the mixture are relatively loose and there are cavities filled with air between them.
The purpose of vibrations is to provide the declared density and uniformity of the mass of concrete.
In the process of vibration, the particles of the concrete mixture come into oscillatory motion, the concrete, as it were, liquefies, its fluidity and mobility increase. As a result, the mixture is distributed more uniformly and completely in the formwork.
The concrete mix is vibrated using vibrators:
- internal (deep) - the mixture vibrates through the body of the vibrator immersed directly in the mixture. The radius of the working vibration is an average of 50 cm, the vibration time of one section of the mixture is 20-40 seconds.
- Surface-vibrators are installed directly on the concrete platform, and transmit vibrations through the platform. The depth of vibration is up to 40 cm, the vibration time of one section is 30-60 seconds.
- External vibrators - vibrators are mounted directly on the formwork and transmit vibration through its sides, the vibration time is 50-90 sec.
Attention! With excessive vibration time, delamination of the concrete mixture is possible.
Visually, the end of the vibrating time can be established upon detection of the termination of the subsidence of the concrete mixture, the acquisition of homogeneous concrete, a flat horizontal surface, with the appearance of "cement milk".
We read further on the foundation arrangement:
|To the begining|
Concrete Laying Guide
Concrete laying is carried out in a way that can ensure the monolithicity of concrete masonry, uniformity of concrete, design physicomechanical indicators, proper adhesion to reinforcement and embedded parts and complete filling of the concrete of the sunken construction space.
Vibration sealing avoids possible voids in concrete, thereby increasing its strength characteristics.
Laying can be carried out in one of three methods used: casting, with sealing and pressure laying.
Regardless of the method chosen, the rule of applying cement layers must be observed until the lower layer dries. Observance of this condition eliminates the need for working joints along the height of the structure.
Concrete laying in the case of small structures (thin-walled, columns, walls, beams, etc.) is carried out without interruptions to exclude working seams. The concrete mix is laid in massive foundation slabs in horizontal layers over the entire area.
Delivery to the place of its installation is carried out using a concrete truck.
It is best to compare everything using a table.
Filing method: Features of the method: 1. Concrete pump.
Concrete pump is a very convenient device with which the solution is supplied to the most inaccessible places, as well as to a height. However, this method is not universal, that is, it does not “work” in all cases. Since the temperature of the concrete mixture during laying must be above zero (otherwise the water in the composition of the mass will simply freeze), then the work of the concrete pump is possible only if the outdoor temperature is not lower than -15 degrees.
It is worth noting that this installation requires a certain free area, and in addition, its rental price is not at all low. 2. Manually.
Manual feed is, of course, the most time-consuming and slow, but it has its advantages.
Firstly, by feeding small portions there is better control over the mixture. That is, pieces of clay, soil and other organics are visible, which can always be managed to remove.
Secondly, the mixture is more compacted, which significantly increases the strength and durability of the future design or product. 3. A special mixer. The mixer is a truck with a tank rotating above, in which the solution is located. The advantage of this feeding method is that it is possible to quickly fill in rather large volumes without loss of quality - the solution is constantly (or periodically) mixed in such a technique.
As for the shortcomings, one can highlight. The "sleeve" of the feed is not very long, which means that the mixture cannot be fed over long distances.
These are the main ways to supply concrete to the place of laying.
Mixer pouring concrete
Please note that it is quite possible to apply combined methods of supplying concrete mass. For example, from the same mixer, you can pour concrete into one desired point on the floor, and then pull the mixture apart with shovels and buckets over the entire plane. It will turn out faster than completely by hand and much cheaper than the services of a concrete pump.
In principle, now we can proceed to consider how the solution is actually poured.
Proper mix placement
It is worth noting that the installation will not be carried out in any one specific way. We will simply consider how exactly it is necessary to fill in the solution correctly in a particular case, and you will determine the method of its supply for yourself - the most convenient.
We will do just that simply because it is impossible to guess the technical features of each object, which means that it is simply impossible to recommend a specific way of filing.
So, let's start pouring concrete with our own hands.
Tile foundation filling
Foundations - this is a very important design, the quality of which depends on the condition of the building and its life. In particular, the foundation requires at least the following basic qualities:
Property: Why this quality is needed: 1. Compressive and tensile strength.
Here, in fact, everything is simple. If the concrete structure is weak, then the foundation will simply not withstand the load and will gradually crack. To make it really durable, you need to use high-strength cement and be able to properly prepare the mixture (that is, maintain the recommended proportions). 2. Resistance to changes in temperature and humidity. This quality depends on two points - on how well the general waterproofing and thermal insulation of the structure are made and, again, on how strong the concrete is. If no voids were formed during pouring and the mixture was made good, then the strength should be at its best.
We will now consider how to fill the foundation so that in the end the monolith turns out to be really strong and durable.
Brief step-by-step instruction:
- At the bottom of a dug trench, we pour a layer of sand, and then we ram it.
Sand cushion under the foundation
- We lay the roofing material on the bottom, and also fasten it to the inner sides of the walls of the trench. It turns out that we are creating a waterproofing layer, thanks to which the concrete "milk" will not be absorbed into the soil, but will remain in the mixture. Due to this, the mixture will dry gradually, without sudden changes in the level of humidity in its structure.
- We make a frame of reinforcement - this design will give the foundation additional strength and protect it from deformation during various loads.
- Knead the solution and start pouring it into the space of the trench. You can also use a mixer in this case - pour the mixture directly from the tank into the pit.
Please note that for pouring foundations you need to use only crushed stone, because this stone is inert and not afraid of moisture. It is important to understand that crushed stone is also different, which means that you need to check with the seller the level of its strength. Indeed, the quality of the hardened concrete largely depends on the hardness of the stone, agree.
It would seem that the instruction is simple, but there are a couple of nuances.
Firstly, if pouring is not carried out at one time, then the mixture only needs to be laid in horizontal rows. If you fill the trenches with vertical fragments, then the so-called "strength difference" can form along the connection lines - after all, the mixture does not always work out to make exactly the same in composition as the previous one.
The mixture in the trench
Simply put, the junction of the “today and yesterday” concrete is better to do horizontally and not vertically, because in the first case, the design will be more durable.
Secondly, thoroughly tamper the whole filled mixture. This is done in order to exclude the formation of hollow sections in the foundation structure. If they are, then in these places cracks will begin to appear, into which water will penetrate. Water will freeze in winter and gradually begin to tear apart concrete.
The consequences are easy to imagine.
Such is the foundation pouring technology.
In principle, the casting of monolithic walls is approximately the same.
Tip: do not forget to foresee in advance where niches for laying pipes, for example, will be located in concrete. But if you still forgot about the preparations for laying such communications and already poured the solution, then do not be discouraged. Because there is such a service as diamond drilling of holes in concrete with a punch and other special tools.
And this means that even in a ready-made foundation, you can cut through anything and anywhere.
Master drills a hole in concrete
We now turn to the device of the concrete floor.
Why exactly the "draft"? Because the finish layer is not filled with concrete, but with a cement-sand mixture without fillers like crushed stone or expanded clay.
What is a rough floor in general - in fact, it is a layer of durable concrete, due to which the main thickness of the general base layer is filled. And already from above the finishing cement-sand screed is poured.
And so that this screed does not crack and does not deform the rough floor should be made as firmly as possible. The better the concrete substrate is, the longer the finish will last.
The rough base is poured in approximately the following way:
- Concrete is mixed from sand, cement, water and stone (crushed stone or expanded clay). In this case, the density of the mixture should not be too liquid, but not too thick - the consistency should resemble fresh honey. Density is easy to check - liquid concrete, when tilting the shovel, quickly drains from it, and torn lines quickly appear in an excessively dry solution.
- A layer of sand is poured over the entire surface of the working base. It is needed in order to level all the differences of the plane and make it as even as possible. The smoother the surface, the less concrete will be used when pouring.
Important! The sand must be compacted, since under it there may be voids that will manifest themselves only under load. That is, simply put, as soon as you fill the concrete and it begins to set, then in some places the sand will sag and at these points the concrete will seem to freeze in the air. The consequences are easy to imagine.
- A film or ruberoid is spread on top of the sand. Thanks to such a waterproofing layer, concrete will dry normally during installation due to the fact that water will not leave the mixture.
- If the floor is made on soil or on a layer of loose soil, then it is necessary to mount on the plane a grid of reinforcement with a mesh size of about 60 to 60 cm. The rods are interconnected by ordinary steel wire.
- On the film, guiding beacons for the floor are installed - horizontally.
- The farthest point of the room is selected and laying of the working mixture begins with it. Concrete is laid very simply - it is poured out of buckets or stretched throughout the room and leveled with shovels (if the solution was supplied from a mixer). Well, if there are beacons, then the whole concrete mass is “pulled together” along them using the rule.
What is important to consider:
- A mass of concrete must be rammed.
- If the floor is poured, then only crushed stone should be used - expanded clay is not suitable.
- After the initial hardening, the floor should be watered every couple of days so that no cracks appear in the concrete.
The rules are simple, and the technology itself on the device of the floor, too. No more work is needed.
Unless only if the floors are already flooded, and you just remembered about laying communications, then you will have to “get acquainted” with such work as cutting reinforced concrete with diamond wheels using a grinder.
The principle of cutting concrete products with diamond wheels
Consider filling another design.
The blind area is arranged around the perimeter of the building and protects the foundation from moisture and (to some extent) from the penetration of cold air.
It is done quite simply, but there are still some difficulties during the pouring of concrete.
The instruction here will be something like this:
- First, a trench is rummaged around the perimeter of the house. Its depth, as a rule, is about 15-20 cm.
- At the bottom of the trench, gravel is poured with an even layer.
- On top of the rubble are streaks of ruberoid. It is desirable to use film-based material, since it is quite strong.
Now, over the plane of the roofing material, you need to mount the frame from the reinforcement. With its presence, the concrete tape around the perimeter will turn out to be as strong as possible. Как на сжатие, так и на растяжение.
Подготовка к укладке бетона в опалубку отмостки
Делается это примерно таким образом – в стене сверлятся отверстия, в которые вставляются прутья арматуры (металл должен располагаться перпендикулярно линии отмостки).
Two parallel lines of the same metal are attached to these rods. One of the lines should run along the wall, and the second along the outer edge of the future blind area.
If such a frame is made, then it is possible to install the formwork and pour concrete. The formwork is a board placed on the edge, which is installed along the outer edge of the entire trench.
The difficulty here is that the concrete must be tamped when laying on the roofing material. But so that this same roofing material in no case breaks! If this happens, the waterproofing layer will be broken and, accordingly, the effectiveness of the blind area will significantly decrease.
Laying concrete in the trench blind areas
We give a very simple advice: it is best in this situation to ram concrete with an ordinary chopper. Due to the small size, the metal nozzle easily penetrates between the bars of the reinforcement and if you work carefully, the roofing material will remain intact.
In principle, that’s all. Our review of concrete supply methods and pouring technology is completed.
It turns out that laying concrete mixture is really not so simple as it might seem at first glance. There really are many nuances on which the final quality of a product or construction made of concrete depends. Therefore, we hope that you will fully take into account all the information provided and be able to put the acquired knowledge into practice.
Well, if you want to know even more tips on this topic, we recommend that you watch an additional video in this article.
Features of the preparation of concrete composition
The composition of concrete includes Portland cement, sand, gravel, water. Cement consumption per 1 m3 is standardized by GOST, the number of components is indicated in kilograms. Sometimes it is better to apply proportions using the ratio of the components. The proportion of cement and sand and gravel should be 1: 8.
Cement. The main component of the concrete mix. His brand should be higher than the brand of the material obtained. Additives reduce initial strength.
Sand. The workability of the solution depends on it. It should be homogeneous, without impurities.
Rubble. Gravel or expanded clay is also used, medium-sized, 10–80 mm in size, without chemical impurities. Sand and crushed stone must be pre-washed from dust, fine fractions.
Water. It is important to accurately determine the amount of water. This affects the strength of the composition after hardening, excess fluid reduces the strength of the product.
In the production of concrete work in winter, cement of the M300 grade and more is chosen, they harden faster. Apply additives that increase the frost resistance of the resulting material. The preparation of the mixture can be carried out at modern automatic plants. Here the automated dosing of the components takes place, everything is thoroughly mixed, a homogeneous mass is obtained. The material is produced in continuous mixers. The rotating drum mixes the materials thoroughly, the finished mass enters the vehicles in a continuous stream.
If the construction site is located far from the concrete production site, it can be prepared in mobile mixers-mixers. The dry composition is mixed while the car is moving. The mixture dissolves 15 minutes before the object. To obtain a small volume of mortar, concrete mixers, various tools for mixing (perforators, drills with nozzles) are used.
Transporting the finished mixture
To transport the mixture from the preparation site to the construction site, various types of trucks are used. Their choice depends on the range of transportation, composition, the required volume. These vehicles include:
- Concrete mixer trucks.
- Concrete trucks.
- Auto solvent transporters.
Concrete mixer trucks are used to quickly transport plastic materials up to a distance of 70 km. They can prepare the solution in the process of movement from a dry finished composition. The machines are equipped with equipment that allows you to maintain product quality during its transportation.
The duration of transportation of the finished concrete composition depends on the temperature at the outlet of the mixer. The higher the temperature, the less time is allowed for its delivery. Transportation of dry components is not limited by time. Adding water, stirring begins 30 minutes before arrival at the construction site.
Sometimes trucks are used to transport concrete mortar. This is not a very convenient means of transportation. It is difficult to protect the material from freezing, drying, leakage. It takes a long time to clean the car body after transportation.
To move concrete within the construction site, concrete pumps, concrete pumps are used. They move the composition through pipelines, while maintaining its quality characteristics, minimizing losses. Pipes are convenient to use when working in confined spaces, places of limited access.
Before starting work on pouring concrete, they prepare the construction site: they remove the garbage, put the marking of the future design, start installing the formwork. The material for this is wooden blocks, boards, moisture-proof plywood, metal or plastic. The formwork is removable, which is dismantled after hardening of concrete, it is used for repeated work. Elements of a fixed system remain in the body of the finished structure.
The dimensions inside the formwork have design values with small tolerances (2 mm per one meter of the length of the structure). The inner walls should be smooth and clean, carefully fitted, tight. To easily remove the formwork after use, they are laid with polyethylene, lubricated with a soap-oil solution. To ensure rigidity, the fence is pulled together with bolts or studs in increments of 100-200 cm, spacers are installed outside.
The formwork is dismantled after 8-10 days, when the strength of the material reaches 80% of the brand value. For load-bearing walls and foundations, it is removed after reaching 100% strength. This also applies to long structures over 8 meters.
An important part of concrete work is the reinforcement of metal frames and nets. The rods are welded at right angles to a specific diameter. The laying pitch is selected from 100 to 400 mm. The pitch and diameter of the bar are determined by calculation depending on the load, grade of cement and element size.
Frames are connected by several grids into a three-dimensional structure by connecting rods. The connection is made by welding, clamps, knitting wire. The protective layer of concrete above the reinforcement is 20-30 cm below and above the element. To reinforce 1 m3 of concrete structure, 70–120 kg of reinforcement is required.
When the preparation is completed, the reinforcing elements are installed, you can begin to pour concrete. To do this, use pumps, vibratory chutes, various superchargers. You can use cars and buckets. Intermediate overload of the solution should be minimal.
The concrete mix is laid in horizontal layers, with a thickness of not more than 50 cm. The direction of pouring of each layer should match. The laying process should be continuous, the next layer is applied before the previous one sets. The height of the fall of the solution into the formwork is not more than 2 m.
Each layer needs to be leveled and condensed. To seal the mixture using vibrators that remove air from it, contribute to uniform distribution and uniformity. Each section is subjected to vibration for at least 40 seconds, then the vibrator is rearranged by 50 cm, overlapping the exposure zones. Vibration units must not touch the formwork and reinforcing elements. Compaction of the mixture is stopped when the surface is covered with cement milk, its shrinkage ceases, air bubbles cease to appear.
Concrete Care and Surface Treatment
After laying the concrete, it is necessary to maintain the temperature and humidity conditions for its correct hardening, which requires protection from the sun, rain, wind and cold. To create such conditions, the structures are covered with a polymer film or tarpaulin.
Humidification of the concrete surface is carried out as necessary, all the time of hardening, keeping it moist. Structures must be protected from loads until 25% of the material strength is achieved.
To get the initial flat surface, the freshly laid mixture is aligned with the rule. Cement milk is removed by moving the iron in different directions. Using special trowels after 4 days of hardening makes the surface perfectly smooth. They rub screed materials into the top layer. After such work with concrete, its surface is dustless, various colors are possible.
This technology is good in that the finished coating can be obtained together with concrete laying, which speeds up the completion of the construction process. High-strength decorative concrete is ground. This treatment is used to obtain mosaic surfaces of floors and walls. Small shells on the surface are wiped with cement mortar, previously moistened with water.