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For the construction of large-panel buildings various types are used hollow core slabs. This building material is made of silicate, lightweight or heavy concrete and has longitudinal voids. This manufacturing technology provides the material with excellent soundproofing properties and light weight. Long service life and good strength characteristics are due to the use of stressed reinforcement or steel ropes.

The essence of the technology is that products are molded on a heated metal floor and reinforced with prestressed wire or rope strands.

The molding machine moves along the rails, leaving a continuous band of reinforced concrete behind it, then the solid slab is heated and cut with a diamond blade into segments of the required length.

Floor slabs produced by formworkless molding have undeniable advantages over hollow core slabs:
- mechanical tension of the reinforcing wire or rope strands, controlled separately for each reinforcing element, ensures the achievement of the same prestress value and, accordingly, the same building deflection of the slabs.
- vibroforming plates automated system guarantees strict adherence to the specified geometric parameters.
- Both surfaces of the plate are vibrocompacted, which ensures the quality of the ceiling surface that meets all modern standards.
- cross-cutting at an angle of up to 60+-0.5 degrees is possible, which makes it possible to produce plates with oblique cuts for non-standard architectural projects.

Hollow floor slabs are widely used due to their low cost and excellent quality characteristics.

Place an order for the products of the ROSATOMSNAB reinforced concrete plant: floor slabs for channels and trays, concrete with delivery,

Floor slabs are reinforced concrete products that are used in private and professional construction to separate the floors of underground or above-ground boxes of residential buildings, public, industrial buildings with a foundation with a high bearing capacity. They are made from high-strength concrete and high-quality conventional or prestressed steel reinforcement.

Hollow slabs are elements rectangular shape, inside them are through round air chambers. Due to such a device, they are relatively light in weight, which helps to reduce the overall load on the foundation and walls. To move with the help of equipment on one side there are steel mounting loops.

Plate characteristics

Advantages:

• strength, durability;
• water resistance;
• fire resistance up to 180 min;
• simple quick installation;
• possibility of use as load-bearing walls;
• permissible load up to 1.5 tons per sq. m in relation to vertically directed loads.

Advantages of hollow concrete products in comparison with solid ones:

• increased sound and heat insulation characteristics due to the air inside;
• through voids it is easier to conduct communications, this helps to reduce the cost of finishing work;
• application in seismic zones;
• high bearing capacity;
• easier transportation, installation;
• increased useful volume of premises;
• the ability to load the ceiling immediately after installation, without tightening it with concrete;
• relatively low price, concrete consumption for the production of hollow core slab is 50% lower, reinforcement is required 30% less.

When buying, you must carefully inspect the product. Defects in the presence of which it is unsuitable for use:

• cracks with a width of more than 0.3 mm;
• there are areas with exposed reinforcement;
• does not match the size;
• surface slope more than 8 mm;
• sinks and washouts with a diameter of more than 15 mm;
• chips on the ribs with a depth of 1 cm and a length of 5 cm;
• insufficient thickness of the concrete layer between the rods and the walls.

The weight of hollow core floor slabs is not less than 700 kg. For transportation, they are stacked in stacks up to 2.5 m high, laying wooden bars between them. It can be transported in a horizontal, vertical and inclined position, provided that it is securely fixed. A crane is required for unloading. If there is a need for long-term storage, then the elements are stacked in piles no more than 2.5 m high, again placing wooden spacers. From above, cover each stack with waterproofing material - the easiest way is with ordinary plastic wrap.

Marking

At the end are:

• marking;
• date of manufacture;
• weight;
• OTK stamp.

The standard consists of several letters indicating the series, and three groups of numbers, which determine the dimensions and bearing capacity. The first and second groups are represented by two digits indicating the length and width in decimeters, rounded up to the nearest whole number. The last group consists of one digit, which indicates the calculated evenly distributed load in kPa, also rounded. Example: PK 23-5-8 - a slab with round voids 2280 long, 490 mm wide, bearing capacity 7.85 kPa (800 kgf / m3).

The designation of some products at the end complements the code of Latin letters and numbers, indicating the type of rods. Example: PK 80-15-12.5АтV - the frame is made of prestressed reinforcement of АтV class.

Additionally, the following can be indicated: the type of concrete (t - heavy), the presence of sealing inserts at the holes (a), the production method (e - extrusion molding method) are indicated. Example: PK 26-15-12.5ta.

Types and marking

Varieties (series):

• PC - standard thickness 22 cm with through cylindrical cavities, made of reinforced concrete of a class not lower than B15;
• PB - a product obtained by a formless method in conveyor forms, with a special reinforcement method, due to which it can be cut along and across without loss of strength, the surface is more even, which simplifies the finishing of floors or ceilings;
• PNO - a lightweight slab made without formwork, differs from PB in a smaller thickness - 16 cm;
• HB - internal flooring made of B40 class reinforced concrete with single-row prestressed reinforcement;
• NVK - class B40 with two-row prestressed reinforcement, thickness - 265 mm;
• NVKU - the same as NVK, but made of B45 reinforced concrete;
• 4NVK - with four-row reinforcement, thickness - 400 mm.

Prestressed (prestressed) reinforcement in the production of precast concrete is subjected to compressive stress at the points where the framework is expected to experience the greatest tension before pouring concrete. After such treatment, strength, resistance to cracking increase, and steel consumption decreases. The characteristics indicate: “prestressed plate” or “with prestressed reinforcement”.

Standard sizes

The length of plates with a thickness of 22 cm (PK, PB, NV series) and 16 (PNO series): from 980 to 8980 mm (in the marking indicate, respectively, from 10 to 90). The step between adjacent dimensions is 10-20 cm. The width of full-size products can be 990 (10), 1190 (12), 1490 (15) mm. In order to avoid the need for cutting, additional elements are used. Their width: 500 (5), 600 (6), 800 (8), 900 (9), 940 (9) mm.

PB can have a length of up to 12 m. If this parameter is more than 9 m, then either the thickness must be more than 22 cm, or the bearing capacity will be lower. The NVK, NVKU, 4NVK series can have a length and width that is not included in the standard grid.

If it is necessary to use structures of non-standard dimensions, they can be ordered according to individual drawings. But this significantly increases the cost of concrete products.

Price

The larger the product, the higher its price. Specifications affecting prices:

• mode of production;
• type of reinforcement;
• the number of reinforcing bars in the frame - minimum, average, maximum;
• concrete strength class;
• mass of concrete.

Prices for reinforced concrete floors PC (optional):

brand	Price per piece, rubles
24-10-8	2400
24-12-8	2800
24-15-8	3400
25-10-8	2600
25-12-8	3100
25-15-8	3600
35-10-8	3600
35-12-8	4300
35-15-8	5100
50-10-8	4900
50-12-8	5900
50-15-8	7400
70-10-8	8800
70-12-8	9700
70-15-8	11700
90-10-8	17400
90-12-8	17400
90-15-8	20700

Approximate price for PB, PNO:

The cost of hollow core slabs NV, NVK, NVKU, 4NVK with a width of 1190 mm:

brand	Reinforcement	Price per linear meter
HB	minimum	1600
	the average	1800
	maximum	1900
NVK	minimum	1750
	the average	1850
	maximum	1950
NVKU	minimum	2150
	the average	2250
	maximum	2500
4NVK	minimum	2650
	the average	2800
	maximum	2900

Many manufacturers offer discounts of up to 20% for large quantities. Hollow core slabs are used for private or industrial multi-storey construction. This type of reinforced concrete has a relatively low weight at a high bearing capacity. There are several varieties of them. They differ in the method of manufacture, type, number of rows of reinforcement, and other characteristics. Big choice standard sizes makes it possible to choose the right product for any buildings. If necessary, manufacturers produce reinforced concrete products of non-standard dimensions with an extra charge. Restrictions - compliance with the requirements for the minimum value of the allowable design load.

If you have at least once encountered the construction process or repaired an apartment, then you should be aware of what hollow-core floor slabs are. Their importance is difficult to overestimate. Design features, its main characteristics and markings are taken into account in the process of work. This knowledge allows us to determine what is the limit of useful and decorative loads that the plate can withstand.

Dimensions and weight

The size and type of the product affect its final price. In length, the described slabs can be equal to the limit from 1.18 to 9.7 m. As for the width, it is limited to a value from 0.99 to 3.5 m.

The most popular are those products whose length is 6 m, while their width usually reaches 1.5 m maximum. The minimum value is 1.2 m. Getting acquainted with the dimensions of hollow core slabs, you can understand that their thickness remains unchanged and is equal to 22 cm. Given the impressive weight of such structures, a mounting crane is usually used to install them, its capacity should be 5 tons.

Types of loads on a reinforced concrete structure

Any overlap in the structure has three parts, among them:

• top;
• lower;
• structural.

The first is where the residential floor is located above. This includes flooring, insulation materials and screeds. The lower part is the surface of non-residential premises. It includes hanging elements and ceiling finishes. As for the structural part, it combines the above and keeps them in the air.

Hollow core slabs play the role of a structural part. A constant static load is exerted on it by finishing materials used in the design of the ceiling and floor. This refers to elements suspended from the ceiling and installed on top of it, namely:

• punching bags;
• dropped ceilings;
• chandeliers;
• partitions;
• baths.

In addition, you can also highlight the dynamic load. It is provided by objects moving on the surface. In this case, one should take into account not only the mass of a person, but also domestic animals, which today are quite exotic (tigers, lynxes, etc.).

Distributed and point types of loads

The above types of loads can be applied to hollow core slabs. Point, for example, is a punching bag of impressive size, suspended from the ceiling. As for the suspension system, it interacts with the suspensions through the frame at regular intervals and exerts a distributed load.

These two types of load can act in combination. In this case, the calculation will be more complicated. If you install a bath that holds 500 liters, then two types of load should be taken into account. The filled container exerts a distributed effect on the surface of the support between the points of contact. There is also a point load, which turns out to be each leg individually.

Calculation of allowable loads

The load on hollow core slabs can be calculated by you. These manipulations are carried out in order to find out how much the product can endure. After that, it is necessary to determine what the overlap will bear. This should include partitions, materials at the base of insulating layers, parquet flooring and cement screeds.

The total weight of the load must be divided by the number of plates. Supports for the roof and load-bearing supports should be located at the ends. The internal parts are reinforced in such a way that the load is on the ends. The central part of the slab is not able to take the weight of serious structures. This is true even if there are main walls or supporting columns below. Now you can calculate the load on the hollow slab. To do this, you need to know its weight. If we take a product marked PK-60-15-8, then it can be argued that its weight is 2850 kg. It is manufactured according to state standards 9561-91.

First of all, it is necessary to determine what is the area of ​​​​the bearing surface of the product, it is 9 m 2. To do this, 6 must be multiplied by 1.5. Now you can find out how many kilograms of load this surface can bear. Why the area must be multiplied by the allowable load by one square meter. As a result, it will be possible to get 7200 kg (9 m 2 times 800 kg per m 2). From here it is necessary to subtract the mass of the plate itself and then it will be possible to obtain 4350 kg.

After that, you need to calculate how many kilograms the floor insulation, floor coverings and screed will add. Usually, they try to use such a volume of mortar and thermal insulation in their work that the materials together do not weigh more than 150 kg / m 2. With 9 m 2 of surface, a hollow slab will carry 1350 kg. This value can be obtained by multiplying by 150 kg/m 2 . This number should be subtracted from the previously obtained figure (4350 kg). Which in the end will allow you to get 3000 kg. Recalculating this value per square meter, you get 333 kg / m 2.

According to sanitary norms and rules, a weight of 150 kg / m 2 must be allocated to static and dynamic loads. The remaining 183 kg/m2 can be used to install decorative elements and partitions. If the weight of the latter exceeds the calculated value, then it is recommended to prefer a lighter floor covering.

State standards and technical requirements

Hollow-core slabs are necessarily used for large-panel buildings for various purposes. They are manufactured according to the above state standard and can be based on the following materials:

• lightweight concrete;
• silicate concrete;
• heavy concrete.

The manufacturing technology, which provides for the presence of voids, provides structures with excellent soundproofing properties and low weight. They are ready to serve long time and have good strength characteristics, which are due to the use of steel ropes and reinforcement.

During installation, such products are located on load-bearing structures. Round voids may have a diameter within 159 mm. The dimensions of hollow core slabs are one of the factors by which products are classified. The length can reach 9.2 m. As for the width, the minimum is 1 m, and the maximum is 1.8 m.

The class of concrete used corresponds to B22.5. The density is equal to the limit from 2000 to 2400 kg/m 3 . The state standards also spell out the brand of concrete, taking into account frost resistance, it looks like this: F200. Hollow slabs (GOST 9561-91) are made of concrete with a strength of 261.9 kg/cm2.

Hollow core grades

Reinforced concrete products cast in a factory are subject to marking. It is coded information. Plates are designated by two capital letters PC. This abbreviation stands next to the number that indicates the length of the product in decimeters. Next come the numbers indicating the width. The last indicator indicates how much weight in kilograms 1 dm 2 can withstand, taking into account its own weight.

For example, a reinforced concrete hollow slab PK 12-10-8 is a product with a length of 12 dm, which is 1.18 m. The width of such a slab is 0.99 m (about 10 dm). The maximum load per 1 dm 2 is 8 kg, which is equal to 800 kg per square meter. In general, this value is the same for almost all hollow core slabs. As an exception, there are products that can withstand up to 1250 kg per square meter. You can recognize such plates by marking, at the end of which there are numbers 10 or 12.5.

The cost of plates

Interfloor hollow core slabs are manufactured using conventional or prestressed reinforcement. Panels, in addition to bearing capacity, must also meet the requirements of sound insulation. For this product, holes are provided, which may have a round or other cross section. Such structures belong to the third category of crack resistance.

In addition to these characteristics, you may also be interested in the cost. You will have to pay 3469 rubles for a hollow slab, the weight of which is 0.49 tons. In this case, we are talking about a product with the following dimensions: 1680x990x220 mm. If the weight of the plate increases to 0.65 tons, and the dimensions become equal to 1680x1490x220 mm, then you will have to pay 4351 rubles. The thickness of the hollow slab remains unchanged, which cannot be said about the other parameters. For example, you can purchase a product with dimensions equal to 1880x990x220 mm for 3473 rubles.

For reference

If the floor slab is manufactured at the factory, then state standards are used in the process. They guarantee the high quality of the product and the conformity of the hardening time and temperature conditions. The full-bodied variety of the plate is distinguished by its impressive weight, respectively, the high cost. This explains the fact that such products are most often used in the construction of important buildings.

Finally

Floor slabs have found their popularity and have become widespread in construction. residential buildings and are lighter than solid boards, and they are cheaper. But in matters of reliability and durability they are not inferior. The location of the voids and their number do not affect the bearing properties of the slab. In addition, they allow you to achieve higher sound and heat insulation properties of the structure.

But no matter how light they are considered, when installing them, you can’t do without the appropriate lifting equipment. This allows you to increase the accuracy of installation and complete construction in a shorter time. These products are also good because they are made in a factory, which means they pass quality control.

Anyone who has dealt with the construction of a house at least once knows how important hollow reinforced concrete slabs or floor panels are. Hollow-core concrete floor slabs, in fact, make up about 90% of the total weight of the house. Floor slabs (PC) can vary greatly in weight and size, depending on the specific purpose for which they are used.

Structural features of hollow core slabs

As you might guess, reinforced concrete floor slabs (PC) are hollow inside, which is why they are marked as multi-hollow when sold. But the holes inside such plates, contrary to misconception, can have not only oval, but also round, square and other shapes.

Hollow core slab support scheme

However, in most cases, floor slabs (PC) have precisely cylindrical hollow circles inside.

Interestingly, floor slabs (PC) can be both unreinforced and reinforced. Reinforced concrete slabs floors (PC) will be exactly reinforced.

Such floor slabs (PC), although they have a much greater weight, which ultimately increases both the load on the building and the cost of construction, however, have a large margin of safety. Installation of floor slabs, namely the installation method itself, depends on what support the slabs will be placed on, because support is also an important criterion.

For example, if the support of the slab is not sufficiently stable, then this can lead to unpleasant consequences, which, of course, must be avoided.

Scheme of laying a hollow core slab on the second floor

Characteristics of hollow core slabs

The size

Its final cost also depends on the size of the hollow PC; in addition to such parameters as width and length, weight is also important.

PC sizes vary as follows:

• along the length, the size of the PC ranges from 1180 to 9700 millimeters;
• in width, the size of the PC ranges from 990 to 3500 millimeters.

The most popular and in demand are multi-hollow panel slabs, which are 6000 mm long and 1500 mm wide. The height or thickness of the panel is also important (height would be more correct, but builders tend to say "thickness").

So, the thickness that multi-hollow panels can have is always a constant value - 220 mm. Of great importance, of course, is the weight of the floor panel. Concrete plates ceilings must be lifted by a crane, the lifting capacity of which is at least 4-5 tons.

comparison table coordination dimensions of hollow core slabs

The length and weight of the panels are essential for construction, length is even less important than weight.

Weight

As for such an important parameter as weight, everything here is very clear from the first time: the range of products manufactured in Russia ranges from 960 kilograms to 4.82 tons. Weight is the main criterion by which the method by which the panels will be installed is determined.

Typically, cranes are used, as noted above, with a lifting capacity of at least 5 tons (of course, cranes must lift weight with some margin).

The weight of panels of the same marking may differ, but only slightly: after all, if we consider the weight with an accuracy of one gram, anything can affect it.

Comparative characteristics main brands of hollow core slabs

If, for example, a product has been exposed to rain, then it will a priori be slightly heavier than the product that has not been exposed to rain.

Types of loads

To begin with, it should be noted that any overlap implies the presence of the following 3 parts:

1. The upper part, with the floor where people live. Accordingly, the panel will be loaded with flooring, a variety of insulation elements and, of course, concrete screeds- the main component of the load;
2. The lower part, with the presence of a ceiling, its decoration, lighting fixtures. By the way, you should not be skeptical about the presence of lighting devices. Firstly, the same LED lamps require partial destruction of the plate with a perforator for cable laying. Secondly, if you take large rooms, with columns and halls, huge crystal chandeliers can hang there, which will give a greater load than any other fixture or type of decoration. This must also be taken into account;
3. Structural. It combines both the upper and lower parts at once, as if supporting them in the air.

A hollow core slab is a structural slab that supports both the top and bottom of the ceiling in the air!

By the way, do not discount the dynamic load. It, as you might guess, is created by the people themselves, as well as the things they move. All this affects the properties and states of the panel.

Diagram of a hollow core slab with holes

For example, if you transport a heavy piano once in a small two-story house from one place to another - this is normal, then daily movement will create much more Negative influence. It is unlikely to fall, but there may be serious problems with ventilation later.

According to the type of load distribution, they are further divided into 2 groups:

• distributed;
• point.

To understand the difference between these two types, it is worth giving an example. The same huge crystal chandelier that weighs one tone is a point load. But stretch ceiling with a frame over the entire surface of the slab - this is already a distributed load.

Installation of a technological line for the production of hollow core slabs

But there is also a combined load that combines point and distributed. For example, a bath filled to the top. By itself, the bath is on legs, and its pressure on the legs is a kind of distributed load. But the legs standing on the floor are already a point load.

Its cost directly depends on the weight of the hollow slab.

It's tricky, but it can be dealt with. And it is necessary! After all, the calculation for floors and hollow core slabs during construction will still need to be done.

Hollow core grades

As a matter of fact, hollow-core slabs do not even have marks as such. We are talking about marking, which reflects some parameters. It suffices to give a small example.

Scheme of laying a hollow core slab on a crossbar

Let's say the panel has the following marking: PK 15-13-10 PK - means a hollow slab; all digital designations indicate any technical parameters.

15 would mean the panel is approximately 15 decimeters (1.5 meters) long. Why about? It's just that the length can be 1.498 meters, and on the marking they have the right to round this figure to 1.5 meters (15 decimeters). The number 12 means that the product has a width of 10 decimeters. The last digit (in this case, 10) is the most important number.

This is the load that the material can withstand (maximum allowable). In our case, the maximum load will be 10 kilograms per 1 dm². Usually builders consider the load per square meter, here it will be 1000 kilograms per 1 m². In general, everything is not so difficult.

The panel brand always looks like PC-XX-XX, if sellers offer other options, then you should be wary.

Load calculation

Limit exposure calculation

The calculation of the limiting impact is a prerequisite for the design of a building. The dimensions and other parameters of the panels are determined by the good old Soviet GOST under the number 9561-91.

The device of a hollow slab with a reinforced screed

In order to determine the load that will be exerted on the product, it is necessary to indicate on the drawing of the future structure the weight of absolutely all elements that will “press” on the floor. Their total weight will be the maximum load.

First of all, it is necessary to take into account the weight of the following elements:

• cement-sand screeds;
• gypsum concrete partitions;
• weight floor covering or panels;
• thermal insulation materials.

Subsequently, all the indicators obtained are summarized and divided by the number of panels that will be present in the house. From here, you can get the maximum, ultimate load on each specific product.

Calculation of the optimal load

It is clear that the maximum allowable level is a critical indicator, which in no case should be brought up to. Therefore, it is best to calculate exactly the optimal indicator. For example, a panel weighs 3000 kg. It is needed for an area of ​​​​10 m².

It is necessary to divide 3000 by 10. As a result, it turns out that the maximum allowable load value will be 300 kilograms per 1 m². This is a small indicator, but you also need to take into account the weight of the product itself, for which the load was also calculated (for example, its value is 800 kilograms per 1 m²). From 800 you need to subtract 300, as a result, you get 500 kilograms per 1 m².

Now you need to roughly estimate how much all the loading elements and objects will weigh. Let this indicator be equal to 200 kilograms per 1 m². From the previous indicator (500kg / m²), you need to subtract the received one (200kg / m²). The result is an indicator of 300 m². But that's not all.

Diagram of a hollow core slab with waterproofing

Now from this indicator it is necessary to subtract the weight of the furniture, finishing materials, the weight of people who will constantly be in the room or in the house. "Live weight" and all the elements, their load, let it be 150 kg / m². Subtract 150 from 300. As a result of all, the optimally acceptable indicator will be obtained, the designation of which will be 150 kg / m². This will be the optimal load.

Advantages of hollow core slabs

Among the advantages of these products are the following:

• relatively small load on the perimeter of the entire building, in contrast to the same full-bodied products;
• high strength indicators, despite the fact that the bottom panels are hollow;
• reliability;
• the draft at home will be much less intense than when using full-bodied products (in fact, this advantage comes from the relatively low weight);
• relatively low cost.

In general, hollow core panels are one of the most important building materials. Today it is produced by only a few factories throughout vast Russia. The main thing, as noted above, is not to be deceived when buying.

Scheme of the arrangement of reinforcing blocks in a hollow core slab

Sometimes (this is rare, but still) sellers try to sell low-quality panels, the so-called lightweight ones. For example, they may be marked, which shows that the product is designed for a load of 500 kilograms per square meter, but in reality this parameter is several times lower.

It's not even fraud, it's a criminal offense that should be punished to the fullest extent of the law. After all, if you buy a panel designed for a smaller load, there is a serious risk of collapse of buildings. Such a situation can be observed not only in the provinces, but even in Moscow or St. Petersburg.

In general, when buying such products, you need to be extremely careful. It is important to remember that any design error can even have tragic consequences.

Video

You can watch a video where experts talk in detail about the features various kinds hollow slabs.

CENTRAL INSTITUTE FOR REGULATORY STUDIES
AND SCIENTIFIC AND TECHNICAL INFORMATION "ORGTRANSSTROY"
MINISTRIES OF TRANSPORT CONSTRUCTION

OPERATING TECHNOLOGICAL CHARTS

MANUFACTURE OF REINFORCED CONCRETE
PRE-STRESSED
FLOOR SLABS ON
FLOW-UNIT TECHNOLOGY

Moscow 1977

Operational flow charts were developed by the Department of Technology Improvement at Industrial Enterprises and Nature Protection of the Institute "Orgtransstroy" (executors V.V. Yudin) with the participation of the Tula Research Institute (executor Ya.B. Bryzzhev), Rostov Research Institute (executor Yu.M. Popov) and Kuibyshevskaya NIS (performer V.I. Khudyakov) of the Ministry of Transport Construction.

Editor V.T. Mikhailov

I. General instructions

Technological operational maps were developed on the basis of a study of the production of work in the manufacture of hollow core slabs of the II-04 series at the Orenburg, Ryazan and Beslan ZhBK plants of the Glavstroyprom Ministry of Transport Construction using the flow-aggregate technology.

The cards are intended for workers, foremen and engineering and technical workers.

Floor slabs are manufactured according to drawings developed by the Moscow Institute of Standard and Experimental Design MITEP. Technological cards can be used in the manufacture of similar floor slabs of the bonded version of the II-04 series, developed by the Central Research Institute for the Experimental Design of Educational Buildings in conjunction with the Research Institute for Concrete and Reinforced Concrete of the Gosstroy of the USSR - Research Institute of ZhB. The working drawings were approved by order No. 173 of August 13, 1973 of the State Committee for Civil Engineering and Architecture under the Gosstroy of the USSR and entered into force on October 1, 1973.

Technological maps are based on the technology for manufacturing floor slabs of the PK8-58-12 type. The same maps can also be used in the manufacture of other types of hollow core slabs of the II-04 series.

Technical characteristics of floor slab PK8-58-12

Concrete grade - 200

Concrete volume - 0.8 m 3

Steel consumption - 39.2 kg

Plate weight - 2 t

Overall dimensions (fig.):

length ( l) - 5760 mm

width ( v) - 1190 mm

height (h) - 220 mm

Limit deviations from the design dimensions of floor slabs are taken in accordance with GOST 13015-75 "Reinforced concrete and concrete products"

length Δ 1 ± 8 mm

in width Δ 2 ± 5 mm

height Δ 3 ± 5 mm

Deviations from the nominal dimensions of the holes in the product should not exceed± 5 mm.

Deviations from the straightness of the real profile of the surface of the product in any section over a length of 2 m, characterized by the largest distance from the points of the real profile to the adjacent straight line, should not exceed:

The number of sinks of acceptable sizes on any section of the front concrete surface with an area0.04 m 2 (200 × 200 mm) should not exceed - 5.

Grease and rust stains are not allowed on the front surfaces of the products.

The quality of smooth concrete surfaces must comply with the approved product standard.

The standard of the product is agreed by the manufacturer with the consumer, the design organization that binds the design of the building or structure, and the state architectural and construction control authorities.

Cracks are not allowed in the concrete of the product supplied to the consumer, with the exception of shrinkage and other surface technological cracks, the width of which should not exceed 0.1 mm.

The cubic strength of concrete by the time the products are shipped from the factory should be at least 100% of the design strength in winter conditions, and at least 70% in warm weather, and in this case the manufacturer must guarantee that 100% strength is achieved at 28 days of age.

As a coarse aggregate, fractionated crushed stone is used that meets the requirements of GOST 10268-70.

As a fine aggregate, sand is used that meets the requirements of GOST 10268-70.

Unstressed reinforcement for floor slabs is made of steel grades A-1, B-1 in the form of welded meshes and frames. Relaxed reinforcement and embedded parts must meet the requirements of GOST 10922-75.

Prestressed longitudinal working reinforcement is provided by the project for the usual version of class A- IV , and for the connection version of class A- V.

The reinforcement is electrothermally stretched on the pallet stops with subsequent transfer of tension forces to the concrete after it has hardened.

Embedded parts and mounting loops are centrally received by the manufacturer.

Flat frames and reinforcing meshes are made in the reinforcing shop in special templates by contact-spot welding on welding machines.

The use of electric arc welding instead of contact-spot welding is prohibited.

For the manufacture of floor slabs, concrete grades 200 and 250 are provided for by the project.

The concrete mixture must meet the requirements of GOST 7473-61.

The following materials are used as lubricants:

emulsol - 10%

soda ash - 0.4 - 0.8%

water - 89.6 - 89.2%

Other types of lubricant may be used in accordance with the instructions for use.

Thermal and moisture treatment of floor slabs is carried out in a pit-type steaming chamber. The mode of heat and moisture treatment is adopted in accordance with the instructions of the "Guidelines for the heat treatment of concrete and reinforced concrete products", M., NIIZhB - VNIIZhelezobeton, 1974.

To obtain 70% of the strength of concrete from the design grade, the following mode of heat and moisture treatment is recommended:

exposure of products in the chamber at a temperature of 20 - 30 ° C- 2 h;

uniform rise in temperature from 20 - 30 to 75 - 80 °C- 2 h;

isothermal heating at a temperature of 75 - 80 °C- 4 h;

temperature drop from 75 - 80 to 30 °C- 2 h;

exposure of products after steaming - 2 hours.

The full cycle of heat and moisture treatment of products under the specified mode lasts 12 hours.

The relative humidity in the chamber should be around 100%.

Depending on the type of cement, composition concrete mix and tempering strength, the mode of heat and moisture treatment is subject to adjustment by the laboratory of the plant.

The quality of the floor slabs is controlled according to the working drawings, and the quality of the raw materials is controlled according to the current standards.

In the absence of a factory passport for cement, it is completelytested in accordance with GOST 310-60.

Each batch of crushed stone and sand must have a passport. At the manufacturing plant, a control check of the quality of aggregates is carried out in accordance with the requirements of GOST 8269-64.

When preparing a concrete mix, the following should be checked:

correct weighing of the components;

mobility (at least twice per shift, as well as with each change in the moisture content of aggregates);

mixing time (at least once per shift).

The quality of products manufacturing is controlled by marking them, compliance with tolerances, acceptance rules, storage and transportation conditions, test methods and other technical requirements in accordance with GOST 13015-75.

Technological maps provide for the manufacture of floor slabs in two parts:

Rice. 2 . Workplace organization scheme:

1 - cleaning and lubrication post; 2 - racks for reinforcing meshes; 3 - rack for reinforcing bars; 4 - electric heating installation; 5 - container for lubrication; 6 - pallets; 7 - a cabinet for a spray rod; 8 - tool cabinet; 9 - racks for nets; 10 - racks for frames; 11 - racks for hinges; 12 - control panel; 13 - vibration platform; 14 - molding machine; 15 - concrete paver; 16 - concrete distributor; 17 - overpass; 18 - tool box; 19 - vibration weight; 20 - post exposure products; 21 - steaming chambers; 22 - electric welding transformer; 23 - cabinet for welding machines; 24 - tool box; 25 - stripping post

From the operator's control panel, the void formers are introduced and the side walls are shifted. Then both workers install vertical flat reinforcing cages, overhead meshes, mounting loops and protective layer clamps. After that, the molds from the concrete paver are filled with the concrete mixture with its leveling. After laying the concrete mixture in the form, it is compacted on a vibrating platform using a vibroweight.

After that, the operator from the control panel displays the void formers and the longitudinal sides of the formwork.

Then both workers proceed to finish the freshly molded product and place the pallet with the product into the curing chamber.

The second link performs operations in the following order: fitter 3rd category. prepares rebar on the S-370 machine, after which he switches to the CM-516A machine for bending meshes and bends the meshes S-5, electric welder 4 category. on a single-point welding machine MTP-200 welds frames and lower reinforcing meshes, then he switches to a multi-point welding machine MTMS and welds S-24 meshes.

Production of reinforcing prestressed rods and mounting loopsnot provided for in the cards, since the plant receives them centrally.

The work of the overhead crane operator is paid by the time, so he is not part of the team.

II. Safety regulations, industrial sanitation

In the manufacture of floor slabs, the "Safety and Industrial Sanitation Rules for the Production of Concrete and Reinforced Concrete Products" must be observed, M., Orgtransstroy, 1974.

To create favorable working conditions in the workshop, it is necessary: ​​to clean the workplaces during the work process and by the end of the shift, to place the used tools and devices on special racks in the posts area.

The form lubricant must be stored near the formwork posts; when carrying and using the lubricant, it must not be allowed to fall on the floor.

The temperature in the workshop should be maintained at 16 - 18 ° C with a relative humidity of at least 60 and not more than 80%.

Workers must be provided with overalls in accordance with norms.

In accordance with sanitary standards noise level should be no more than 90 dB. The administration is obliged to carry out measures to reduce noise in the production room.

Floor slabs with round voids are stored in a stack no more than 2.5 m high.

Sling plates for mounting loops with an automatic traverse.

The manufacture of floor slabs is allowed for persons at least 18 years of age who have passed a medical examination, training according to the established program and have studied the safety and signaling rules.

Workers involved in the manufacture of floor slabs should study the standard instructions for labor protection by profession: Typical instruction on Safety for Fitters”, M., Orgtransstroy, 1977, “Typical safety instructions for steamers and autoclaves”, M., Orgtransstroy, 1963, “Typical safety instructions for a welder working on resistance welding machines, and for electric welders of automatic and semi-automatic arc welding”, M., Orgtransstroy, 1971, as well as SNiP III-A.11-70, "Safety in construction" section 5 "Electric welding work".