Supporting the slabs on gas silicate blocks. Floor slabs. Reinforced concrete hollow slabs
Based on the material used, the slabs are divided into:
- reinforced concrete;
- aerated concrete.
Reinforced concrete hollow slabs
This is the most popular and affordable type of slab.
Previously, the use of massive reinforced concrete floors was unavailable in the construction of a private house due to their high cost and heavy weight, requiring the use of special equipment for delivery and lifting. Now such problems do not arise, but crane or manipulator have become commonplace in low-rise construction.
Hollow core slabs made of reinforced concrete have additional relief in the form of through chamber openings, and they themselves are made from heavy grades of concrete using reinforcement, which provides the necessary rigidity and strength. Such an overlap has a number of undeniable advantages:
- Lightweight design compared to monolithic slab; voids significantly reduce the weight of the product, which means they can be safely used in buildings made of aerated concrete up to 3 floors inclusive.
- High strength, which is ensured internal cavities, reinforcement and high-quality concrete. Load bearing capacity slabs of this type from 800 kg/m2.
- Simplified installation and the ability to mount on bases of any shape. The size of the slab can be 6 or 9 meters, which significantly expands the possibilities for planning.
- Internal cavities can be used to accommodate communications and wiring.
- Good sound insulation.
The installation of reinforced concrete floors will be required along the entire perimeter. It can be made monolithic using formwork and reinforcement with a thickness of 10 mm. The width of the belt is at least 150 mm - the distance over which the slab will rest. This reduces the load on the walls and eliminates local stresses caused by pressure top floor and the stove itself.
Marking
According to the configuration of the cavities, the slabs are divided into:
- PC – with round voids, rests on 2 sides;
- PKT – with round cavities, rests on 3 sides;
- PKK - with round voids, laid on 4 walls;
- PKT – with round cavities, installation on 2 end and 1 long side;
- PG – with pear-shaped voids; thickness – 260 mm; support on 2 ends;
- PB – made without formwork, using continuous molding; its thickness is 260 mm, hole diameter is 159 mm; The product is placed on 2 end sides.
Based on the size of the cavities and thickness, the slabs are divided into the following types:
solid single-layer:
- 1P - slabs 120 mm thick.
- 2P - slabs 160 mm thick;
multi-hollow:
- 1pc - slabs 220 mm thick with round voids with a diameter of 159 mm.
- 2PK - slabs 220 mm thick with round voids with a diameter of 140 mm.
- PB - slabs 220 mm thick without formwork molding.
Slabs of types 2P and 2PK are made only from heavy concrete. 
Dimensions
The size of the hollow core slab is indicated in its markings.
For example, PC 90.15-8. This is a round-hollow slab 90 decimeters long and 15 inches wide. The permissible load on the floor is 8 MPa (800 kgf/m2).
Below the spoiler are given standard sizes slabs To view, click on the “Table” heading.
|
Slab type |
Coordination dimensions of the slab, mm |
|
| 1pc | From 2400 to 6600 inclusive. at intervals of 300, 7200, 7500 | 1000, 1200, 1500, 1800, 2400, 3000, 3600 |
| 1pc | 1000, 1200, 1500 | |
| 1PKT | From 3600 to 6600 inclusive. at intervals of 300, 7200, 7500 | |
| 1PKK | From 2400 to 3600 inclusive. at intervals of 300 | From 4800 to 6600 inclusive. at intervals of 300, 7200 |
| 4pcs | From 2400 to 6600 inclusive. at intervals of 300, 7200, 9000 | 1000, 1200, 1500 |
| 5pcs | 6000, 9000, 12000 | 1000, 1200, 1500 |
| 6pcs | 12000 | 1000, 1200, 1500 |
| 7pcs | From 3600 to 6300 inclusive. at intervals of 3000 | 1000, 1200, 1500, 1800 |
| PG | 6000, 9000, 12000 | 1000, 1200, 1500 |
You will find more information in the article about.
Support depth
It is important not to exceed the maximum support depth. Otherwise, the slab will act as a lever and, under heavy loads, the wall may rise slightly above the slab. It is not noticeable to the eye, but is critical for the structure. Under loads from installed furniture, equipment and constructed internal interior partitions Cracks may appear in the walls due to stresses.
The length of support (the depth of insertion of slabs into the walls) should not exceed:
- For brick walls— 160 mm;
- when supporting floor slabs on aerated concrete blocks class B3.5-B7.5 - 200 mm;
- when resting on a concrete reinforced belt - 120 mm.
The minimum support length is also standardized. It should not be less than:
- 80 mm - for brick walls;
- 100 mm - for walls made of cellular concrete blocks;
- 65 mm - when resting on dense concrete class B10 and higher.
Installing a floor made of reinforced concrete structures will necessarily require the use of a crane or manipulator with a large lifting capacity. The weight of a standard 6-meter slab reaches 2 tons. In addition, installation will require certain skills. So the alignment is carried out along the seams on the smooth side of the ceiling, after which the slabs are fastened with anchors, and the joints are poured cement mortar. Mineral wool and polystyrene foam can be used as insulation. 
Aerated concrete slab floors
Not only are partitions made from foamed concrete, but also interfloor partitions. This material has good strength, low thermal conductivity, it is easy to process and easy to use. Aerated concrete slab can withstand loads from 300 to 600 kg/m2, and the maximum weight does not exceed 750 kg. The precision with which such an overlap is made allows installation in a short time and does not require additional preparation for subsequent finishing. These are the lightest floor slabs for aerated concrete walls.
Now on the market you can find two types of such structures:
- Manufactured from concrete by autoclave injection molding, equipped with special elements"groove-toe" type, which simplifies installation. With this method, the density can correspond to the concrete grade D500. This option is most in demand in low-rise construction.
- Standard panels, reinforced with reinforcing elements, can be used in any monolithic construction. They are easy to process, inexpensive, and well suited for non-standard solutions.
Maximum size aerated concrete slabs does not exceed 5980 by 625 mm, and the thickness can range from 150 to 300 mm. Minimum length 2980 mm, pitch 300 mm. Such a variety of sizes and low weight makes it possible to close the space between floors or any complex shape easily and with minimal losses.
The edges of the slab must rest against the wall of the house by at least 10 cm, so the layout must be done taking into account this size.
The disadvantages of such an overlap arise from the features of the cellular concrete , therefore, the choice must be approached carefully and after careful calculations of the load-bearing load and operating conditions.
- Aerated concrete is a very fragile material that is practically devoid of elasticity. To avoid cracks in walls and ceilings, it is necessary to take care of a high-quality monolithic or well-buried foundation that excludes any movement of the soil.
- This material perfectly absorbs moisture, and this will require additional waterproofing with a special primer in rooms such as the bathroom and toilet. The reinforcement in aerated concrete must be processed in accordance with the requirements of SN 277-80, which guarantees a service life of the floors of at least 25 years.
- A load-bearing capacity of less than 600 kg/m2 is insufficient to accommodate heavy furniture and equipment and a large number of people. Screed, flooring, heated floor systems reduce the already low load capacity.
- Additional reinforced concrete beams, laid across a distance across the width of the slab.
Comparative Cost
When constructing interfloor structures, the issue of price plays an important role. If we compare all the varieties with each other, we get the following sequence. The cheapest will be a reinforced concrete hollow slab with cost per square meter at 1200 rubles. In second place will be a monolithic product - 2000 - 2500 rubles per square meter. The cost can vary greatly depending on the thickness and manufacturing technology.
The most expensive flooring is a slab of foamed concrete - from 3,000 rubles per square. The high cost is explained by the complex manufacturing technology and the small width of the slab.
Also, the cost of slab flooring must include the costs of transportation and lifting, which in some cases may be equal to their value.
In the process of building walls made of aerated concrete or foam concrete, there comes a time when you need to take care of installation of interfloor ceilings, which can be made of a concrete slab or wooden beams.
Unlike houses built of brick, during installation interfloor ceilings on walls made of gas or foam concrete blocks, it is necessary to additionally provide distribution and reinforcing belts.
In this article we will consider the installation of wooden and reinforced concrete interfloor ceilings when building a house from wall blocks.
Installation of interfloor ceilings from a monolithic slab
Many private developers, when building a house from aerated concrete or other similar blocks, use reinforced concrete slabs.
These are very reliable and durable foundations, but at the same time they have a lot of weight, which must be taken into account when erecting walls from building blocks.
In order to ensure that the weight of the slab is distributed evenly and does not violate the integrity of the walls, when laying slab floors, an additional structure must be made in the form of a distribution concrete or brick belt.
Options for installing a monolithic reinforced concrete slab are shown in the figure.
In the first version, the slab rests on a concrete strip measuring 150x250 mm, located along the entire perimeter of the wall. The tape is reinforced with rods with a diameter of 10 mm and filled with concrete grade M200.
It is also necessary to leave a temperature gap of 1-2 cm between the wall and the end of the reinforced concrete slab.
To remove cold bridges, the slab and reinforcing belt are additionally insulated using extruded polystyrene foam boards, 50 mm thick.
Second option It is a masonry of red burnt brick laid in 3 rows. This is the most popular version of the distribution belt device. In this case, there is no need to construct formwork and make a reinforcement frame from rods.
But before laying the bricks, they strengthen the wall blocks with reinforcement. To do this, grooves are cut, reinforcing bars are placed in them and filled with cement mortar.
Brickwork is also strengthened using masonry mesh, laid between the rows.
The monolithic reinforced concrete slab should extend 13-14 cm deep into the wall. This is quite enough for the stability and rigidity of the structure.
Wooden interfloor ceilings
Wooden construction is the most preferable option when building houses from light wall blocks. Wooden interfloor ceilings are much lighter than concrete ones, which means they put less pressure on the wall, and therefore the design will be simpler.
In addition, the price of wooden logs, taking into account delivery and labor, is significantly less than the cost of reinforced concrete slab floors. There is no need to hire an expensive crane and everything can be done without the use of machinery.
In one of the articles (link) we already talked about the construction of floors using wooden beams. In it we provided the calculation of floor beams and floor construction according to wooden joists. Perhaps this information will be useful to you. But let's return to our topic.
As we already wrote, installation wooden floors more simple. It is enough to make a belt from reinforcement, as is the case with concrete slabs, on which beams can be laid.
Before installation, wooden logs must be coated with antifungal compounds, and the ends that will lie on the wall must be wrapped in roofing felt or other similar material.
You also need to cut down the end part of the beam at an angle of 60 0 and lay the insulation
Between the end and the wall, it is necessary to leave a gap of 2 cm for possible thermal expansion.
Wooden logs should be laid into the wall to a depth of 15 cm.
In conclusion, we offer you a video that will be useful in the further installation of wooden floors.
Correct, competent installation floors – a guarantee of reliable, long-term operation of buildings. For buildings made of blocks (“lightweight concrete”), additional support is required - an armored belt. Reinforcement of walls made of gas silicate blocks is a special additional building, mandatory when installing floors.
The production of reinforced belts for houses made of cellular concrete, the installation of floor slabs is regulated by SNiP. Here are the brands and characteristics of the slabs, required parameters leaning on the walls, what and what kind of armored belt is made of. Compliance with these standards is directly related to the structural stability of building structures.
How to support the floor
The main purposes of floors include division internal space buildings on floors, overlapping spans, to perceive and transfer the load of its own weight, interior, people to walls (supports). This Basic structure, using reinforced concrete slabs. They are divided by:
- manufacturing (multi-hollow, prefabricated monolithic);
- structures (beam, beamless);
- location (attic, interfloor, floor);
- material (heavy, cellular concrete)
- sizes.
Commonly used slabs for gas silicate walls, these are hollow reinforced concrete floor slabs. The device of additional lightening (through holes), reinforcement in combination with heavy grades of concrete, give the structure strength with the necessary rigidity and relatively low weight. Tables with characteristics of hollow-core structures of reinforced concrete floor slabs:
"Note. To reduce freezing of the slab, it is necessary to seal the holes in the hollow slabs (the edges rest on outer wall). It’s more convenient to do this on the ground in advance.”
Installation of floor slabs on gas silicate blocks carried out using specially manufactured seismic belts. This monolithic structures made of reinforced concrete. Installed on load-bearing walls ah, repeating the perimeter of the structure.
When supporting the slabs on interior walls, which are necessarily built with support on the foundation, the belt further strengthens the structure. This is achieved by distributing the load over the floor area. Laying of floor slabs on gas silicate blocks takes into account the following requirements:
- installation only on armored belt;
- symmetry of installation;
- aligning the ends along the line;
- deviation along the plane of the slabs – up to 5 mm;
- the connection of the plates to the belt is carried out by welding and is made mechanically strong;
- Anti-seismic belts are poured along the width of the walls.
For external walls, foam blocks with a density of at least D 500 are used, the width of the belt is 500 mm (can be reduced by 100-150 mm), thickness is 200-400 mm. Concrete grade B 15, not lower.
Before installing floor slabs on gas silicate blocks, reinforcement is made 15-20 cm thick. The belt is filled with concrete using formwork or special U-shaped blocks, installing building boxes along the perimeter of the load-bearing walls (including internal non-load-bearing partitions). The support of the slabs on the external walls is 25 cm, with the usual one - 12 cm.
Install the slabs using a tap on a freshly prepared solution (2 cm layer). It is made thick (before setting, without additional dilution with water) so that it does not squeeze out of the seam. Before this, the surfaces of the load-bearing walls are leveled, then the ceiling will be smooth, without differences. Covering two spans at once with one slab entails an incorrect load. Under unfavorable conditions, it will crack anywhere. By making a cut on top of the slab (with a grinder to the depth of the disk) above the middle partition, this can be avoided. The crack will go at the site of the incision. And this is no longer so important.
"Important. Mostly hollow core slabs designed to support two sides. It is not recommended to place the long side on the wall. To support it on the third side, check the slab reinforcement scheme with the manufacturer.”
Normalized support depth values
The parameters (depth) of slabs entering walls made of “lightweight concrete” (gas silicate, aerated concrete, foam concrete, etc.) depend on:
- thickness of the wall material of the load-bearing structure;
- for what purposes is the building being built (housing, production, administrative premises);
- span sizes;
- weight, size of floors;
- type and magnitude of load (static or dynamic, point or distributed);
- construction area (seismicity).
These factors are taken into account in calculations made for the reliability of buildings. Active regulations, determine the depth of support of the slabs on the blocks by:
- Ends – 25 cm.
- Contour, at least 4 cm.
- On both sides (span up to 4.2 m - at least 5 cm, over 4.2 m - 7 cm).
The final dimensions are determined during the design of the building by engineering calculations. When the permissible dimensions are reduced, the edge of the masonry is destroyed. And if it is exceeded - pinching (weight load from a higher wall). The result is cracking and destruction of the walls.
Why do you need an armored belt?
A structure made of gas silicate blocks cannot withstand high loads(shrinkage of the building, settlement of the soil underneath, daily temperature changes, seasonal changes). As a result, the material cracks and collapses. To avoid various kinds deformations, monolithic reinforced concrete belts are installed. The armored belt takes these loads upon itself, distributes them evenly, ensuring the reliability of the structure.
It is also capable of evenly distributing vertical loads. Giving the structure rigidity, it prevents movement of the floor slabs (porous blocks expand with the movement of moisture and steam). For what else did it get the name - unloading. Another purpose of the armored belt is to protect the edges of the upper blocks from destruction (installation of interfloor ceilings). Remove point loads of wooden beams during roof construction. Considering these qualities, an armored belt is simply necessary when supporting the floor slabs of the second (subsequent, roof) floors in a house made of gas silicate blocks.
Belt manufacturing process
To begin, prepare the necessary tools:
- for formwork (hammer, screwdriver, nails, screws);
- welding machine;
- buckets, spatula.
The surface of the gas silicate blocks is prepared and the formwork is installed. It can be made from any material with low hygroscopicity:
- Steel.
- Aluminum.
- Tree.
- Plywood.
- Plastic.
- Combined material.
You can make the formwork yourself or order ready-made panels.
Reinforcement is placed in the prepared place (4 rods, 12 mm in diameter), or finished frame. The rods are connected in the shape of a “ladder” (the step of the jumpers is 5-7 cm). The minimum number of rods that can be used is 2 pcs. The corners of the frame are welded or connected with wire. If a large load is expected, a frame of a volumetric structure is used. The frame is installed on bricks, pieces of blocks (whatever touches the wall) are filled with concrete.
Since the armored belt is a bridge of cold, it must be insulated. This will help avoid destruction of aerated concrete blocks when moisture enters and freezes. If you plan to only plaster and not insulate aerated concrete blocks, the armored belt is made taking into account the insulation layer (less in thickness). But don't forget minimum dimensions slab laying depths.
"By the way. Laying layers of bricks on the walls, along with reinforcement mesh or just mesh, is not an armored belt, and is not acceptable.”
After the installation of the floors is completed, anchoring is carried out. The anchors are welded to the hinges on the slabs and to the mounting hinges on the mills (they are tensioned beforehand). You can also use a concrete ring anchor. It runs like reinforced belt in the same plane with the slab (not under it), along the entire perimeter. Then it is filled with concrete. All voids on the slabs must also be sealed.
From all of the above, the question of whether floor slabs can be supported on gas silicate blocks sounds affirmative. Required condition For this purpose, it is necessary to construct a monolithic reinforced concrete belt. This will ensure the reliability of the structure being built, and if all dimensions are observed, it will prevent the house from collapsing.
Currently, in our country, the most popular are three methods of constructing floors in a house. This is the installation of floor slabs, the installation of a monolithic reinforced concrete floor and the installation of floors using wooden (less often metal) beams. We will definitely talk about all these methods and more. And the first technology we will consider is the installation of ready-made floor slabs.
First, a little about the floor slabs themselves. Depending on their shape, all slabs can be divided into flat and ribbed. Flat ones, in turn, are divided into solid and hollow. We are now interested in empty ones, because... It is this type of slab that is used mainly in low-rise construction.
Hollow core slabs, in turn, are also classified according to various parameters, such as the shape and size of the voids, the thickness of the slabs, the manufacturing technology of the slabs, and the method of reinforcement.
I will not delve into the topic of classification. It is better to look for this information on the websites of manufacturers of reinforced concrete products (reinforced concrete products). We'd better talk directly about installation.
The very first point that you need to pay attention to even at the stage of designing your future home is the opportunity to purchase in your area exactly the slabs of the sizes that are included in the project. Each manufacturer has its own specific range of products and it is always limited. This is really important and I am surprised that very often developers forget about this recommendation and then they have to either cut one or more slabs or do it on the floor monolithic site. We'll talk more about this below.
Storing floor slabs at a construction site.
Of course, it’s great if you have the opportunity to lay floor slabs immediately when they are delivered directly from the car that brought them. But most often this does not happen. Or the driver insists that you unload the slabs as quickly as possible, because... he is in a hurry for the next order, or the slabs are not laid on the machine in the order you need, or you simply bought them in advance and are not going to lay them yet. In all these cases, the slabs will need to be stored on your site.
Try to choose a flat surface for this. Never place slabs directly on the ground. Be sure to put something under the edges of the slab, for example, scraps of wooden beams. There should be only two pads, at a distance of approximately 25-40 cm from the edges. Pads cannot be placed under the middle of the slab.
The slabs can be stored in stacks up to 2.5 meters high. Make the shims for the first slab higher, so that if they are possibly pressed into the ground when laying subsequent slabs, the first slab should never touch the ground, otherwise it could easily break. It is enough to make all subsequent linings even from an inch (2.5 cm). They must be stacked strictly one above the other.
Preparation for installation of floor slabs.
Preparation begins at the moment when the masons cast out the last rows of masonry. The slabs will lie flat and without differences if the upper rows of load-bearing walls are level and in the same horizontal plane.
To achieve this, there must be marks in all corners of the room being covered horizontal level. They are installed during the construction of walls using a level, or laser level, or hydraulic level. And when the last row of masonry is done, the distance from the marks to the top of the walls is controlled with a tape measure. It should be the same in all corners. From my experience I can tell you for sure that some masons neglect this, especially when they do backfill masonry at the same time as the face masonry, which is done “under the rod”.
The top row of load-bearing walls must be bonded. That is, if you look from the inside of the covered room, then on the load-bearing walls (on which the floor slabs rest) in the very top row of the masonry, only the pokes should be visible.
If the slabs are placed on a load-bearing partition 1.5 bricks thick (that is, the slabs rest on it on both sides), then the top row of such a partition is laid out in one of two ways:
Before laying floor slabs on walls made of various blocks (foam concrete, gas silicate, slag, etc.), it is necessary to make a reinforced concrete belt (usually about 15-20 cm thick). Such a belt is made either by pouring concrete into the formwork, or using special U-shaped blocks along the entire perimeter of the house box, i.e. not only on load-bearing walls, but also on non-load-bearing ones.
When installing hollow core slabs, the holes in them must be sealed. It is much more convenient to do this in advance, while the slabs are still on the ground. In general, SNiP prescribes that voids must be sealed on the side of the slab that rests on the outer wall (to reduce the likelihood of freezing of the slab), and on the side that rests on the internal partition, only starting from the third floor from the top of the house and below (to increase strength). That is, if, say, the house has basement floor, overlap between the 1st and 2nd floors and attic floor above the 2nd floor, it is mandatory to fill the voids on the side of load-bearing partitions only in the basement floor.
I will say that we always seal holes when laying slabs. Moreover, in Lately Increasingly, round-hollow slabs come from factories with holes already filled. It's comfortable. If the holes are not sealed, we insert a one-and-a-half brick (you can even use half) into them and fill the remaining cracks with mortar.
Also, before installing the slabs, it is necessary to prepare the site for the crane in advance. It’s good if in the place where the crane will stand the soil is, as they say, compacted. It's worse when the soil is bulky. If you have a basement, you should not place the faucet too close to the house, in order to avoid what is shown in the figure below:
In such cases, it is better to order a truck crane with a longer boom. Also, sometimes in the place where the faucet will stand, you first have to put several road slabs(usually used ones are found somewhere). Often this has to be done in the fall in rainy and slushy weather, when the area is so “broken” that the crane simply gets stuck on it.
Laying floor slabs.
Three people are enough to install the floor slabs. One hooks the slabs, two lay them down. If you want, you can do it together, although not always. It happens that when covering, for example, the second floor, the installers and the crane operator do not see each other. Then, at the top, in addition to the 2 people directly laying the slab, there must be another person who will give commands to the crane operator.
Laying begins from the wall on a layer of mortar no more than 2 cm. The mortar should be thick enough so that the slab does not squeeze it completely out of the seam. After the crane operator places the slab on the walls, he first leaves the slings taut. At the same time, using a crowbar, if necessary, it is not difficult to move the slab a little. If the upper surfaces of the load-bearing walls were made smooth, then the slabs will lie evenly, without differences, as they say, “from the first approach.”
Regarding the amount of support of the slabs on the walls, I will give an extract from the document “A manual for the design of residential buildings. Vol. 3 (to SNiP 2.08.01-85) 6. COLORS:
Paragraph 6.16.: The depth of support of prefabricated slabs on walls, depending on the nature of their support, is recommended to be no less than, mm: when supported along the contour, as well as two long and one short sides - 40; when supported on two sides and the span of slabs is 4.2 m or less, as well as on two short and one long sides - 50; when supported on two sides and the span of the slabs is more than 4.2 m - 70.
When assigning the depth of support for floor slabs, you should also take into account the requirements of SNiP 2.03.01-84 for anchoring reinforcement on supports.
In our practice, we try to make the support no less than 12 cm, fortunately now it is possible to purchase exactly the slabs that are needed. The step of their lengths is 10 cm.
I often hear debates about whether it is possible to support hollow-core floor slabs on three sides (two short and one long) and how far the long side of the slab can be placed on the wall. From what is written above, it follows that it is possible to support the slabs this way. But it is not so. If you read the specified SNiP, it says that slabs that rest on three sides have a different reinforcement pattern than those that rest on only two sides.
The vast majority of hollow core slabs that are currently produced by concrete factories are designed specifically to be supported on two short sides, so it is not recommended to place them on the wall with their long side. Under a certain load, this can lead to cracking of the slab. The reinforcement scheme and, therefore, the possibility of supporting the slab on a third side must be clarified with the manufacturer.
Another mistake associated with improper loading of the slab is covering two spans at once (see figure below):
Under certain unfavorable conditions, the slab may crack, and the location of the crack is completely unpredictable. If you still use such a scheme, use a grinder to make a cut (to the depth of the disk) on the upper surface of the slab strictly above the middle partition. Thus, if something happens, the crack will pass precisely along this cut, which, in principle, is no longer scary.
Of course, it’s good if we manage to cover ourselves exclusively with whole slabs. But circumstances are different and yet sometimes some slab (or even more than one) has to be cut lengthwise or crosswise. To do this you will need a grinder with a diamond disc for concrete, a sledgehammer, a crowbar and not the weakest guy at a construction site.
To make work easier, it is better to place the slab on a lining. Moreover, this lining is placed exactly under the cut line. At a certain moment, the slab will simply break along this line from its own weight.
First of all, we make a cut on the upper surface of the slab with a grinder along the cut line. Then, striking with a sledgehammer from above, we cut a strip along the top of the slab. It is quite easy to penetrate concrete in void areas. Next, we use a crowbar to break through the lower part of the slab (also through the voids). When cutting a slab lengthwise (we always cut along the hole in the slab), it breaks quite quickly. When chopping across, if the slab does not break after breaking the lower part with a crowbar, a sledgehammer is used to strike the vertical partitions of the slab from the side until the victory is achieved.
During the cutting process, we cut the reinforcement that comes across. You can use a grinder, but it’s safer to weld or cutting torch, especially when the reinforcement in the slab is prestressed. The grinder disc can bite. To prevent this from happening, do not cut the reinforcement completely, leave a couple of millimeters and then tear it apart with a blow from the same sledgehammer.
Several times in our practice we had the opportunity to cut slabs lengthwise. But we have never used, so to speak, “stumps” less than 60 cm wide (less than 3 holes remain), and I do not advise you to. In general, when deciding to cut a slab, full responsibility for possible consequences You take full responsibility for this, because not a single manufacturer will officially tell you that cutting a slab is possible.
Let's now see what can be done if you still don't have enough slabs to completely cover the room:
Method 1- we place the first or last (maybe both) slabs without bringing the long side to the wall. We fill the remaining gap with bricks or blocks, hanging them no more than half from the wall (see figure):
Method 2— we make the so-called “monolithic section”. Plywood formwork is placed underneath the slabs, a reinforcement frame is made (see figure below) and the area between the slabs is filled with concrete.
Anchoring of floor slabs.
After all the slabs have been laid, they are anchored. In general, if the construction of a house is carried out according to a project, then it must contain an anchoring scheme. When there is no project, we usually use the circuit shown in the figure:
The anchor is made by bending the end into a loop, which clings to the mounting loop of the slab. Before welding the anchors to each other and to the mounting loops, they must be tensioned as much as possible.
After anchoring, we immediately seal all mounting eyes in the slabs and rustications (seams between the slabs) with mortar. Try not to delay this so as not to get rusted construction garbage, and water did not pour into the eyelets during rain and snow. If you suspect that water has gotten into the slabs (for example, you bought slabs with voids already filled in, and rainwater could have gotten in even while being stored at the factory), it is better to release it. To do this, after installation, simply drill one small hole in the slabs from below with a hammer drill, into the voids where the mounting lugs are located.
It is especially dangerous to find water in voids in winter time when the house is not yet heated (or not completed at all) and the slabs freeze below zero. Water saturates the bottom layer of concrete, and with repeated freezing-thawing cycles, the slab simply begins to collapse.
Another way to secure the slabs is to construct a so-called concrete ring anchor. This is a kind of the same monolithic reinforced belt, only it is not made under the slabs, but in the same plane with them, also around the entire perimeter of the house. More often this method is used on foam concrete and other blocks.
Let me make a reservation right away that we have never used it because it is much more labor intensive. I think a ring anchor is justified in more earthquake-prone regions than our Nizhny Novgorod region.
At the end of the article, I suggest watching a short video that talks about choosing floor slabs:
Comments:
The question of how to install floor slabs becomes relevant during the construction of any room. At first glance, it may seem that installation is quite simple, but there are some nuances that need to be taken into account when constructing and constructing a building.
Floor slabs are reinforced concrete products intended for arranging interfloor floors.
To understand how to lay slabs, you need to know the technology and rules for laying floor slabs. Divide reinforced concrete structures can be done as follows:
- round-hollow ceilings;
- tent (ribbed);
- long ribbed.
Some prefer to use monolithic reinforced concrete slabs in construction, but this option is more expensive. The most common types used for floors are reinforced concrete round-hollow ones. They have good thermal conductivity and sound insulation.
Floor slab installation technology
For installation you need:
- round hollow-core reinforced concrete slabs;
- truck crane;
- cement mortar (cement, water, sand);
- Master OK;
- grinder or autogen;
- sledgehammers;
- level;
- scrap;
- steel brush;
- tow;
- gypsum mortar;
- lime-gypsum mortar;
- thermal insulation material;
- welding machine.
This is not to say that installing floor slabs is an easy process; on the contrary, it is considered quite labor-intensive and risky.
Any foundation is not level and smooth, therefore, before installing reinforced concrete floor slabs, it would be correct and advisable to make the foundation level, for example, lay a brick row on a concrete base. You can check how smooth the surface is using a level. Floor slabs can only be laid on the most flat surface possible; the future service life of the entire building depends on this.
It is necessary to take care of the strength of the foundation, because due to heaving of the soil, its deformation can occur, and regardless of how responsibly the builders approach the installation and how they lay the floor slabs, the building will sag over time.
You can secure the foundation with a regular reinforced mesh, onto which you can then apply concrete mortar and floor slabs are installed. The cement must be at least grade 100. The height of the cement layer must be at least 20 cm.
Before installing reinforced concrete floor slabs, you need to prepare them.
If there are flaws, protrusions or chips on the surface, they must be eliminated.
To understand how to lay slabs, before installing and assembling reinforced concrete floor structures, you need to calculate the width so that they occupy the entire perimeter and there are no uncovered parts left. The calculation scheme is quite simple.
Before the installation process, a substrate is laid out from concrete mixture. Laying floor slabs is only possible with the help of a truck crane, since their weight is quite large. Having hooked the reinforced concrete slabs onto the hinges, they are lifted and placed in the right place. Moreover, it will not be possible to carry out installation alone; this process requires a team of 3-5 people. When installing, you need to ensure that each slab lies flat, all elements should be as close to each other as possible. Due to the fact that the cement footing does not harden immediately, the slabs will still be mobile for some time, and installation inaccuracies can be corrected by straightening them with a crowbar.
Floor slabs should only be laid on capital walls future premises. Installation of internal partitions and walls is carried out after installing the floor slabs, and they should rest 12 cm on the wall. Adjacent slabs must be secured to each other with mounting loops. For installation, it is better to use a cement-sand mortar; it must be liquid, the sand must be thoroughly sifted, otherwise even if small debris gets in, it can lead to deformation of the floor and ceiling.
After the floor slabs have been installed, there are seams between them that must be sealed. All seams must be cleaned using a steel brush. The gaps between the elements of the reinforced concrete structure are filled with tow, previously soaked in gypsum mortar. The tow layer must be compacted. When the gypsum mixture dries, its volume increases, thus pressing the tow as much as possible against the walls. After this, the cracks are covered with lime-gypsum mortar.
The existing ends also need to be sealed so that the slabs do not freeze during the cold season.
For this you can use mineral wool, concrete mortar or backfill brick.
In any construction process, force majeure situations may arise, for example, slabs may burst if unloading rules are violated or they were stored incorrectly.
But throw it away so expensive construction material inappropriate. They can be installed on 3 main walls. Or install them attic space, in this place the load is minimal.
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Laying floor slabs: important points
To ensure the accuracy of the design, you need to draw a diagram with all dimensions, this way you will be able to avoid gaps and shortages of slabs. If there are still large gaps, they can be filled with cinder blocks, and small gaps and cracks can be filled with concrete mortar.
When installing hollow core slabs, you need to ensure that they fit smooth side down. They should be located as close to each other as possible - even the smallest gaps should be avoided. They need to be laid, adjusting to each other along the bottom edge.
When installing floor slabs on a foundation, it is very important to know that they should be installed only on 2 walls, and with the short sides and not the long sides. This installation method is needed in order to prevent possible deformation and displacement if the foundation “sags.”
The point is that in such cases the entire weight of the structure moves to the third, long side, and cracks or gaps may appear on the short sides, and this cannot be allowed. Also, we should not forget that the short sides of reinforced concrete blanks should not be installed completely on the walls - by 11-15 cm. This will help reduce heat loss in further exploitation any room.
You should immediately think about where the communications will go in order to leave gaps for them between the floor slabs.
After installing reinforced concrete structures, it is imperative to tie them together reinforcing bars for the strength and strength of the future premises. Rods with a diameter of 9-12 mm are suitable for this; you can use wire rod of class A1 (when loads arise, it will stretch and not break). The rods are welded at one end to the loop, and at the other end to the loop of the adjacent floor blank. It is impossible to connect several reinforced concrete slabs at once - only two slabs are connected to each other. The slabs are secured with anchors on the outside.
It is imperative to pay attention to the rules for transporting, unloading and storing reinforced concrete structures and materials so that they do not undergo deformation. Between reinforced concrete slabs it is necessary to place at the same distance and in the same places wooden beams, otherwise they may burst under load.
In some cases, when reinforced concrete slabs for a long time are in the cold, they can freeze, then due to the moisture that will be in reinforced concrete structures, fungus can form and mold can appear. To avoid this, you need to make small holes in each workpiece at a distance of 25 cm from each other and blow into them polyurethane foam. Thus, reinforced concrete structures will not absorb moisture.
