Introduction.

The production of precast concrete requires all-round intensification technological processes, in particular, reducing the duration and energy consumption about heat treatment.

The hardening time of concrete in structures and products, as is known, at pr and changes in heat treatment are significantly reduced compared to hard and eat in regular temperature conditions, but far exceed the duration of other manufacturing operations reinforced concrete products. In the general production cycle, heat treatment is 80 ... 85% in time, and its hundred and the bridge is a significant part of the total cost of products and designs to tions. Heat treatment also determines the quality of the structure of the cement stone in concrete.

Over 90% of precast concrete is subjected to steaming. For those r moprocessing 1 m 3 prefabricated reinforced concrete products is spent from 120 kg of steam.

The duration and energy intensity of the heat treatment of prefabricated iron e reinforced concrete are determined not only by the accepted method and mode of intensification of the concrete hardening process, but also by a number of other factors– mineralogical with about the rate, activity and consumption of cement, the composition of concrete, the type and amount of chemicals introduced into the concrete mixture.

In this course project, the process of production of glands is considered about concrete floor slabs, the heat treatment of which is carried out in a polygon about the body camera

The appointment of heat treatment modes is made on the basis of standards a literature, taking into account the type and class of concrete, cement activity, thickness and ny products, methods of raising heat, and other factors. To check the proi mode h the calculation of product temperatures throughout the entire process of thermal processing was carried out and boots.

The thermotechnical calculation of the installation is based on physical processes and is a calculation heat balance. The balance consists of expenditure and income parts, and most fully reflects the heat phenomena occurring in the installation. b change.

Based on all calculations designed heating network and technologist and cial lines for the production of products, taking into account the specified production conditions and design capacity. Measures for safety precautions, protection of tr y yes, prot and fire engineering.

1. 
   Short description technological process from sa.

For the manufacture of reinforced concrete floor slabs, a form is used to about which is fed to the vibrating table.

The manufacturing technology of reinforced concrete slabs includes the following stages:

• mold lubrication
• laying the reinforcing cage and assembling the mold
• innings concrete mix from paver to fo r mu
• compaction of the concrete mix.
• transportation of the form using a conveyor and a lift-descent into a polygonal chamber
• heat treatment of the product according to the specified mode
• submission of the product to the post from the deck
• removing the plate from the mold
• inspection and acceptance of QCD
• transfer of the product to the warehouse

The freshly molded board is subjected to heat treatment by supplying steam to the steaming chamber. In order to prevent erosion of concrete by a jet of steam coming under pressure, perforated nozzles are placed on the supply pipes. With this method of heat treatment, decompaction does not occur b e tones.

1. 
   Characteristics of the product and form.

In this course project, a floor slab 1200-60-200 is adopted as a building product. Such slabs are manufactured in accordance with GOST 26434-85 "Reinforced concrete floor slabs", and according to the standard they have a about the value of 2P60.12.

Plates must have the following characteristics and mi:

• must be strong and crack-resistant, and when testing their load e to endure n troll loads
• materials used for the preparation of concrete must meet about meet the requirements existing standards and specifications for these materials.
• must meet the requirements of GOST 13015.0:
• the value of the tempering strength of concrete panels as a percentage of brand b e compressive strength tone should be equal to 70%
• Plates follow and to prepare from heavy concrete in accordance with GOST 26434 class for compressive strength a tie not lower than B15

To feed the product into the chamber, the form trolley CSM - 151 is used

The maximum range is 120m.

Travel speed 32 m/min

Track width 820 mm

Dimensions 7.49 - 2.5 - 1.4 m

Weight 2.5t

Plate size	Coordination dimensions of the plate, mm		Plate weight (reference), t
		Length		Width
2P60.12	6000	1200
2P60.24			2400
2P60.30			3000
2P60.36			3600

1. 
   The composition of the concrete mix.

According to GOST 26434-85 "Reinforced concrete floors" slabs should and h to prepare from heavy concrete for compressive strength B15.

To ensure this requirement, the concrete mix BSGT P1 V22.5 is used, prepared from the following components o nents (per 1 m 3 of the mixture):

• cement brand M500 - 353kg
• sand  p \u003d 2630 kg / m3

fractions: 2.5 - 5 10%

1,25 - 2,5 25%

0,63 - 1,25 25%

0,315 - 0,63 20%

0,14 - 0,315 15%

Less than 0.14 5%

710 kg

• granite crushed stone r sh \u003d 2670 kg / m 3

fractions: 10 - 20 70%

20 - 30 30%

1157 kg

• water - 180 kg

Density of the concrete mixture r bs \u003d 2400 kg / m 3

For the production of one slab, 1 m 3 concrete and 25 kg of steel for the frame.

1. 
   Choice and substantiation of the mode of thermal and boots.

For the production of the product, we assign the following plow mode:

1. Pre-exposure 2 h a sa;
2. Rise in temperature 3 hours;
3. Isothermal exposure 5 hours;
4. Cooling time 2 hours.

Total: 1 2 hours

To calculate the temperatures, we use the criterial dependencies t e conductivity under non-stationary conditions of heat transfer. Concrete Consideration and as an inert body without taking into account the heat released during hydration e menta.

The qualitative characteristic of the rate of change in body temperature in an unsteady regime is taken into account by the criteria co m Fourier complex:

where

 - duration of heating (cooling), h;

R - determining the size of the product, m;

a - coefficient of thermal diffusivity, m 2 /h;

where

 - coefficient of thermal conductivity of the material, W / (mº C), for hardening bet about on  \u003d 2.5 W / (m º C);

ρ - concrete density, kg/m 3 ,

c is the heat capacity of the material, kJ / (kgº C),

KJ / (kg º C),

where

with c, p, sh, v, m - mass heat capacities of cement, sand, crushed stone, water, reinforcement metal, respectively, kJ / (kgº C),

G c, p, u, v, m - weight of cement, sand, crushed stone, water, reinforcement metal, respectively, kg.

	cement	sand	rubble	water	steel
s, kJ / (kg º C)	0,84	0,84	0,89	4,19	0,48
G kg.			1157

KJ / (kg º C),

According to the formula:

M 2 /h

According to the formula, taking into account R = 0.1 m. and τ = 1.0 h. we have:

The dependence of the rate of heat propagation in the product on the intensity about sti of external heat transfer are taken into account by the criterion co m complex Bio:

where

α- heat transfer coefficient from the medium to the surface of the workpiece W / (m 2 º C);

for α 1 =70, α 2 =80, α 3 =85, α 4 =90 we have the following values e niya Bi :

; ; ; .

When calculating the temperature of the material at point x, a criterion dependence of the type is used:

where

 - dimensionless temperature;

t s - the average temperature of the environment for the corresponding calculated temperature e riod, º C

t n - product temperature at the beginning of the calculation period,º C.

The surface temperature is

Temperature at the center of the product

Values ​​of dimensionless temperatures p and  c determine from the tables based on the values ​​calculated above Fo and Bi :

 c1 =0.75;  c2 =0.73;  c3 =0.72;  c4 =0.71;  p1 =0.31;  p2 = 0.29;  p3 =0.27;  p4 = 0.25.

The average temperature of the product for the billing period is determined by fo p mule

, ºС

According to the formulas, we calculate the temperatures in the center, on the surface, as well as the average temperatures of concrete at 1, 2 and 3 hours of the temperature rise mode at ry and for 5 hours of isothermal exposure and enter them in the table and tsu.

	Rise in temperature			Isothermal exposure
Q c	0,75	0,73	0,72	0,71	0,71	0,71	0,71	0,71
Q p	0,31	0,29	0,27	0, 25	0, 25	0, 25	0, 25	0, 25
t p	22,48	40,24	61,36	75,34	78,83	79,71	79,93	79,98
t c	17,71	25,75	37,91	44,91	55,08	62,31	67,44	71,08
t b cf	19,3	30,58	45,73	55,05	62,99	68,11	71,60	74,05

For clarity of the process of heating concrete and steam-air medium, we plot the temperature change during e me

With such a thermal calculation of temperatures, the temperature of the products is obtained without taking into account the heat of hydration. In real conditions, the temperature of concrete by the end of isothermal exposure can be reduced by 5 ... 10º C in relation to z a given by the regime.

1. 
   Determination of the required number of thermal units, their sizes and layout e niya.

Plant hourly output ed/h

where

N0 - annual productivity of the line, m 3 ;

5th edition - average volume of the product, 6 * 12 * 0.2 = 1.44 m 3

M is the number of working days in a year;

K is the number of shifts;

Z - duration of the work shift, h.

Length L k \u003d L 1 + L 2 + L 3

where L 1 , L 2 , L 3 – lengths of temperature rise, isothermal holding and cooling zones well denia, respectively, m

L to \u003d 63.83 + 106.38 + 42.55 \u003d 212.76m

Since the length of the camera should not exceed 127m, then we accept two cameras with

L to \u003d 212.76 / 2 \u003d 106.38m

Where l f - length of the form - trolleys, m

L1 - gap between the forms - trolleys along the length, m

Camera Height

n i - the number of tiers in the chamber

h f - height of the trolley form, m

a- free gap between the forms - trolleys in height, m

h1 - the distance from the bottom of the form - the trolley to the floor of the chamber, is determined by the height of the rail track from the floor of the chamber and the height of the rail, m

h2 - distance from the upper surface of the product to the ceiling, m

Chamber width with a passage in the middle

V \u003d b f +2 b 1 \u003d 1.4 + 0.6 \u003d 2m

b 1 - allowable gap between the walls of the chamber and the form - trolley, m

When arranging a passage from the side, the width B increases by 0.6 m.

B= 2 + 0.6 = 2.6m

Heat of exotherm:

The amount of heat of hydration released by 1 kg of cement:

M - brand of cement

the number of degree - hours from the beginning of the process, deg / hour

W / c - water-cement ratio

a is a coefficient.

Determine the number of degree-hours for the period of temperature rise:

We define specific heat hydration for the lifting period:

The total amount of heat of hydration released by the cement in the chamber:

We determine the increase in the average temperature of products due to the heat of the hydrate a tion of cement:

Conclusion: due to the exotherm of cement, we provide heating of concrete to a given temperature and this mode of heat treatment.

1. 
   Compilation and calculation of cheers in the thermal balance of the installation.

The heat balance of continuous installations is drawn up separately. about sti for each zone (temperature rise and isothermal exposure), while the calculation is made on the average hourly productivity of the installation.:

KJ

where

Q \u003d g r * i p – hourly heat consumption required for heat treatment of the product, kJ/h

β - coefficient taking into account fixed losses those n lots;

N r – Hourly productivity of the plant,

Q b - the amount of heat consumed for heating concrete, kJ;

Q f - the amount of heat spent on heating the metal of the mold, kJ;

Q sweat - the amount of heat lost by the installation to the environment, kJ;

Q to - losses with condensate, kJ.

Heat for concrete heating. The amount of heat spent on heating the mass of the product, we determine by the formula:

KJ

where c b - weighted average heat capacity of the concrete mass of the product, kJ / (kgº C);

G b - weight of the product, kg;

t n , t to - average concrete temperatures at the beginning and end of the respective period,º C.

Calculate this value for periods of thermal b work:

temperature rise:

KJ

isothermal exposure:

KJ

Heat for mold heating.The amount of heat spent on heating the meta l la forms are defined by the expression:

KJ

where c m - heat capacity of the mold material, kJ/(kgº C);

G f - mass of the mold, kg;

t to - the final temperature of the concrete surface of the product in the corresponding period o de, º C;

t n - the initial temperature of the metal of the mold, equal to the period of temperature rise– air temperature in the workshop or on the street, and during the period of isothermal holding– temperature of the concrete surface of the product at the end of the temperature rise period and tours, º C.

Calculate this indicator for periods of heat treatment t ki

temperature rise:

KJ

isothermal exposure

KJ

Heat for heating chamber structures. Heat on heating fence Yu The overall design of the heat treatment plant is calculated by the formula:

KJ

where with i - mass heat capacity of the corresponding layer of the structure considered and vaulted fence.

G i - mass of the considered layer, kg

t to i is the average final temperature of the material of the considered layer of the structure,ºС;

t n i - the initial temperature of the material of the considered layer of the structureº C.

Heat transfer resistance of the building envelope:

Heat loss for heating the walls of the structure when the temperature rises.

Estimated weight of each element of the wall structure:

G 1 \u003d 58509 kg / m 3

G 2 \u003d 1170.18 kg / m 3

G 3 \u003d 4212.65 kg / m

Heat loss for heating the walls of the structure during isothermal exposure

Heat loss for heating the top of the structure when the temperature rises:

calculation of temperature on each layer of the fence:

Estimated weight of each element of the top structure:

G 1 \u003d 69147 kg / m 3

G 2 \u003d 1382.94 kg / m 3

G 3 \u003d 4978.58 kg / m

Heat loss for heating the top of the structure during isothermal exposure

Heat transfer resistance floor fence Yu cabbage soup designs:

Heat loss for heating the floor of the structure when the temperature rises.

calculation of temperature on each layer of the fence:

Estimated weight of each element of the floor structure:

G 1 \u003d 110635.2 kg / m 3

G 2 \u003d 22127.04 kg / m 3

Heat loss for heating the floor of the structure during isothermal exposure

Calculate the heat loss to the environment using the following formula

Heat loss when the temperature rises:

Calculate the heat loss to the ground using the following formula

Loss of heat when the temperature rises

Heat loss during isothermal exposure:

We substitute the obtained values ​​into the heat balance equation and express h a total coolant flow rate for the lifting zone and isothermal soaking:

Temperature rise:

Isothermal exposure:

Heat lost with condensate.Heat lost with condensate, pa with is read according to the formula

kJ/h

from to - heat capacity of condensate (for water with k \u003d 4.19), kJ / kg º C;

t to - condensate temperature. (70 degrees)

Heat lost by evaporation of water:

r - heat of phase transition, (2232.2 kJ / kg)

1. 
   Determination of hourly and specific consumption of heat and coolant by periods (zones) and boots.

Hourly flow rate of the coolant for periods of temperature rise and isothe R mic exposure is determined by the formulas

kg/h

kg/h

where  Q I ,  Q II , - total heat consumption, taking into account the coefficient of unaccounted losses for periods of temperature rise and isothermal holding, respectively t ly, kJ.

I , II - duration of each period, h.

Using formulas (18) and (19), we calculate the hourly steam consumption

kg/h,

kg/h

Specific coolant consumption per 1 m 3 concrete is calculated according to the expression e niyu

kg/m 3

where

N r - hourly productivity of UND for concrete, m 3 .

N n - weekly productivity of the plant, m 3 .

kg / m 3

Specific heat consumption per 1 m 3 concrete

KJ

KJ / m 3

1. 
   Pipeline calculation.

The diameter of the pipes leaving the installations is calculated from the pho p mule

The average density of the coolant in the area:

Average coolant density:

Pipeline diameter for temperature rise zone:

Pipeline diameter for isothermal holding zone:

Diameter taking into account temperature rise and isothermal exposure:

Accept temperature rise pipe 40

We accept a pipe for isothermal holding 50

We accept a pipe for raising the temperature and isothermal holding 60

Max Diameter 70mm

1. 
   Suggestions for saving energy resources and improving the quality and s deli .

Heat treatment of concrete and reinforced concrete products should be carried out about be carried out taking into account the laws of heat and mass transfer, the parameters of the concrete mix and the method of heat and moisture treatment.

Reducing the consumption of energy resources in the designed process for the production of reinforced concrete floor slabs can be carried out by increasing the thermal resistance of the enclosing structure- product forms.

It is also possible to reduce the consumption of energy resources by improving the quality and accuracy of the use of instrumentation and shut-off and control valves.

Most effective ways accelerate the hardening of concrete are chemical additives– hardening accelerators and complex additives containing superplasticizer and hardening accelerator.

To reduce the production cycle and improve the quality of concrete, it is possible to apply such methods and modes of heat treatment as, for example, preliminary steam and electric heating of the components of the concrete mixture or with a my concrete mix followed by a short h the action of heat.

The use of preliminary steam and electric heating of the concrete mixture can significantly reduce the time of heat treatment. The time of pre-exposure and temperature rise is almost completely excluded from the general cycle, the duration of about thermal heating.

1. 
   Measures for safety, labor protection and against about fire engineering.

Labor protection must be carried out in full compliance with the "Rules for safety and industrial sanitation at the enterprises of the construction industry n nosti".

It should be emphasized that workers entering enterprises must be allowed with to work only after training them in safe working methods and instructing a Ms. on safety. Additional briefings should be held quarterly and annually— immediate safety training t at the workplace with those.

At operating enterprises, it is necessary to protect the moving parts of all m e khanisms and engines, as well as electrical installations, priya m ki, hatches, platforms, etc.

Electric motors, as well as various types of electrical equipment, must be grounded. Appropriate devices and installations must be provided a new lifting and transport mechanisms for the safe maintenance of repair a bot.

In the area where the installation work is being carried out, no other work is being carried out. Cleaning of structural elements to be installed from dirt and ice about until they rise. It is forbidden to lift prefabricated reinforced concrete structures that do not have mounting loops or marks that ensure their correct slinging and installation.

The applied methods of slinging structural elements and equipment provide e they are fed to the installation site in a position close to the design one. There are no people on the elements of structures and equipment that are on weight. eleme n you of the mounted structures or equipment during movement are kept from rotation and swinging by flexible t heavy.

During the production of installation (dismantling) works in the conditions of an operating enterprise, operated electrical networks and other existing engineering systems with topics in the work area are usually turned off and short-circuited. Equipment and pipelines are exempted from explosive, combustible and harmful in e.

In the production of installation work to secure the technological and mo n equipment and pipelines, as well as technological e skies and building construction in agreement with the persons responsible for their correct operation.

When sliding structures and equipment with winches, the load capacity of the brake h winches should be equal to the carrying capacity of traction winches, unless other requirements are established by the project. Unpacking and depreservation of the equipment to be installed about ing is carried out in the areas allocated in accordance with the project for the production of works, and is carried out on special racks or linings with a height of not m e her 100mm. When depreserving the equipment, it is not allowed to use materials with s in and fire hazardous properties.

Pre-assembly and additional fabrication of structures and equipment to be installed (threading pipes, bending pipes, fitting joints, etc.) b ne) should be carried out, as a rule, in places specially designed for this.

In the process of performing assembly operations, matching holes and checking their coincidence in mounted parts is carried out using special equipment. It is not allowed to check the coincidence of the holes in the mounted parts with your fingers.

When installing equipment, the possibility of spontaneous b nogo or accidental inclusion.

When moving the equipment, the distance between it and the protruding parts of the mounted equipment or other structures must be horizontally at least 1 m, p tickal - 0.5 m.

When installing equipment using jacks, measures must be taken to exclude the possibility of distortion or overturning. and niya jacks.

1. 
   List of used literature at the rye

1. Voznesensky A.A.Thermal installations in the production of building materials and fishing and products. - Moscow: Stroyizdat, 1964.
2. Nesterov L.V., Orlovich A.I.Guidelines for the course project on di with Zipline "Heat engineering and heat engineering equipment". - Minsk: BSPA, 1997.
3. SNB 2.04.01.-97. Construction heat engineering. - Minsk: Ministry of Architects at ry and construction of the Republic of Belarus, 1997.
4. GOST 26434-85. Reinforced concrete floors. - M .: Publishing house of the stand R tov, 1984.
5. Koksharev V.N., Kucherenko A.A.Thermal installations. - Kyiv: graduate School, 1990.-335 p.
6. Peregudov V.V., Horny M.I.,Thermal processes and installations in the technology of building products and parts. – M.: Stroyizdat, 1983. – 416 p.

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Floor slabs - reinforced concrete products that are used in private and professional construction to separate the floors of underground or above-ground boxes 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-core slabs are rectangular-shaped elements, inside of which there 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 from 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 22 cm thick with through cavities of a cylindrical shape, 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 pricing:

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

Prices 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 with 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.

Floor slabs are an inexpensive, convenient and indispensable, in many cases, building material. With their laying, you can complete the construction of the garage, separate the basement from the main body of the building, bring out the floors or use it as part of the overall roof structure. Like another similar construction material made of reinforced concrete, used in various areas of construction and laying underground gas pipelines, floor slabs have several varieties of their own. They differ in several parameters that have their own characteristics.

The use of floor slabs in installation work

The extensive scope of floor slabs is quite understandable - this great material for standard construction, for high-speed construction of retail space, structures industrial enterprises and other objects. Occasionally they are also used for private households, for example, for laying on a foundation over a basement or basement level. They are excellent for quick construction of block, stone and brick buildings, for large-panel installation, as well as for the base under quick assembly houses made of wood.

There are also non-standard varieties of floor slabs, for example, tented ones - they are often cast to cover the entire size of the room in the form of a dome or a pyramidal shape. However, their cost can be several times higher than the cost of standard plates, and the dimensions depend on the architectural project.

The main advantages of building materials

1. Thanks to the system of crossed beams and reinforcement with concrete filling, such reinforced concrete structures are able to withstand quite an impressive load.

2. Today, slabs are made from high-strength concrete according to the latest technologies- to obtain high quality material. For example, they have found wide use in the area of ​​seismic activity.

3. Hollow building material has excellent thermal insulation properties, it is frost-resistant and promotes fire safety.

4. When properly installed, a standardized building material provides waterproofing to the building and performs other insulating tasks. For example, it prevents the penetration of noise, steam, gas into other parts of the building.

5. Floor slabs are able to provide absolute horizontal surfaces, especially with proper adjustment of the supports.

6. The material is strong and durable, does not require additional maintenance and facilitates finishing top coats becoming the basis.

7. Some hollow varieties contain porous materials for additional frost resistance or resistance to temperature changes.

Varieties of floor slabs

Universal building material is produced different sizes, but they all have one thing in common - their shape. Plates are produced in 2 types - full-bodied and hollow.

1. Solid monolithic floor slab has no internal voids, used on the lower floors and in construction production areas. This building material has 3 subspecies:

• beamless slabs, monolithic smooth material for ceilings;
• coffered slabs, which resemble a cellular grid of identical beams with a small layer of concrete, used for industrial construction;
• ribbed floor slabs withstand the greatest load, for example, at the base in high-rise construction.

Manufacturing monolithic slab overlapping is a fairly simple process, which is often carried out at the installation site. The rebar frame is loaded into a horizontal formwork, after which it is poured with concrete. The dimensions of these plates may vary.

Main technical parameters and product marking

An important factor for calculations in architecture and installation is compliance with the requirements for standardization of the production of floor slabs. They must comply with GOST not only in terms of dimensions, but also in terms of strength, crack resistance, rigidity and other parameters in order to withstand the design load.

According to GOST, floor slabs have different sizes, but they always have their own standards. It is convenient for the design of buildings and their installation.

The letters are the brand of the product, 2 digits are the length measured in decimeters, the following digits are the width also in decimeters, the last digit in the marking indicates its total design load, without taking into account the weight of the floor slab itself, that is, its bearing capacity in the floor structure. For example, when marking PK 53-12-8t, this means that the plate is round-hollow, that is, the parallel holes in it have a cylindrical shape. Its dimensions, length and width are indicated in decimeters, and t means that it is made of dense M200 concrete.

The standard thickness of a reinforced concrete floor slab is about 220 mm, but there is a lighter version, 16 mm. This building material also has an important indicator - the third category of crack resistance, that is, cracks are permissible in their operation, but this cannot affect the main bearing characteristics buildings. Some slabs are produced with additional reinforcement class AtV. It is believed that the largest bearing capacity is monolithic floors, when pouring these plates, a professional flooring of the N brand is used.

Marking also suggests other characteristics:

• 1PK - multi-hollow 220 mm, with a diameter of rounded voids 159 mm;
• 2PK - multi-hollow slabs of 220 mm, with a diameter of rounded voids of 140 mm;
• 1P - 1-layer solid plate, outlet 120 mm;
• 2P - solid plate 160 mm;
• PB - multi-hollow formation slab without formwork for 220 mm.

When marking 1P in millimeters, the standard dimensions for floor slabs are:

• 3000x4800, 3000x5400, 3000x6000 and 3000x6600;
• 3600x4800, 3600x5400, 3600x6000 and 3600x6600.

When marking 2P in millimeters, the standard dimensions for floor slabs are:

• 2400x6000,
• 3000x4800, 3000x 5400, 3000x 6000;
• 3600x2400, 3600x3000, 3600x3600, 3600x4800, 3600x5400 and 3600x6000;
• 6000x1200, 6000x2400, 6000x3000 t 6000x3600.

Such size options provide the most accurate fit on objects of individual planning of any configuration. voids may have different shape and the spacing between them.

Features of hollow core slabs and marking

The hollow slab has parallel holes inside, round, oval or square. In fact, most voids are cylindrical in shape. There are reinforced and non-reinforced slabs. Although the reinforcement will make the products heavier, they have the greatest margin of safety, therefore they are used in the lower part of the structures.

Each marking of the floor slab speaks not only about its main characteristics, but also takes into account the features for choosing in a particular installation site.

• PB - slab with rounded voids 159 mm in diameter, laser cut to any length during continuous forming. Standard: length 6-12 m, width 1, 1.2 and 1.8 m, thickness 260 mm. Mounted on both ends on the wall;
• PG - plate with oval voids for mounting on both ends, thickness standard 260 mm;
• 1PK - a plate with rounded voids with a diameter of 159 mm, thickness 220 mm, mounting on both ends;
• 2PK - a plate with rounded voids of a smaller diameter, 140 mm, thickness standard 260 mm, mounting on 2 ends;
• 2PKT - slab with voids 140 mm in diameter, but 220 mm thick, installation supported on 3 sides;
• 2PKK - a slab with the same parameters (220 mm 140 mm), supported by 4 walls;

• 3PK - a plate 220 mm thick with rounded voids 127 mm, supported by 2 ends;
• 3PKT - a plate with the same parameters and support on 3 sides, where 2 are end and one is open long;
• 3PKK - slab with voids 127 mm, thickness 220 mm, mounting with support on 4 sides;
• 4PK - a plate with voids with a diameter of 159 mm, a thickness of 260 mm, for installation along 2 ends;
• 5PK - plate 260 mm thick with holes 180 mm, mounting with support on both ends;
• 6PK - a plate with rounded voids 203 mm, thickness 300 mm, support along 2 ends;
• 7PK - plate thickness 160 mm with a void diameter of 114 mm, mounting supported on 2 ends;
• 1PKT - a slab with the same parameters as the previous one, but it is laid on the walls with support on 3 sides;
• 1PKK - a plate with the same parameters, installation on 4 sides.

According to the type of reinforcement of the HB slab, I have the following varieties:

• in HB slabs, B40 grade concrete and one-yard reinforcement are used;
• in NVK - concrete of the same grade and two-yard reinforcement;
• in NVKU - two-yard reinforcement, concrete grade B45 is used.

Basic technical parameters of floor slabs

1. Concrete is used in reinforced concrete products, which has a compressive strength index of the order of B22.5.

2. Concrete grade for slabs used in harsh climates - F200, taking into account the frost resistance margin.

3. Concrete density index - about 2000-2400 kg/m3.

4. The strength index of concrete must meet the parameters of 261.9 kg / cm2.

5. Grade of concrete for laying slabs at the bottom, taking into account moisture resistance - W4.

6. The length of the floor slabs varies according to the standard - within 2.1-9.2 m.

7. Product width standards - about 1m, 1.2m, 1.5m, 1.8m.

8. NV and PB slabs are also made from 0.55 m wide.

Floor slabs as a foundation

Domestic housing construction widely uses a slab type of foundation laying. For this, monolithic, ribbed and hollow concrete products are suitable, it all depends on the number of storeys and the total load of the building. Such a foundation has little pressure on the ground, so the building is easier to tolerate seasonal fluctuations in the soil. The installation of such a foundation is the least laborious and is suitable for the quick installation of prefabricated houses - in 1 season.

Before laying, the pit is leveled and the bottom is filled with crushed stone, gravel or sand for laying floor slabs. In a low-rise building, a foundation with hollow slabs will be reliable, cheaper, such slabs provide better sound and heat insulation. The seams between the slabs must be covered so that the prefabricated foundation structure is the most solid. For such a design, plates with a thickness of 100-120 mm are suitable, and for a more solid structure, plates of 200-250 mm with stiffeners are needed. In their voids it is also very convenient to lay various communications.

Storage and transportation of floor slabs

From the correct storage and transportation of floor slabs in the future will depend on the quality of the construction, respectively, and the safety of the entire facility. Plates are transported only by special transport, which guarantees their integrity, and it also ensures competent unloading and storage. Slabs of the same size are stored in piles, carefully stacked on top of each other, but not higher than 2.5 m. It is advisable to lay spacers of about 30 mm between them. Stacks can be covered with a protective film - from the destructive effects of precipitation and aggressive external environment. Stored for years outdoors and with significant temperature differences, floor slabs should not, they become damp and lose their properties.

Features of laying floor slabs

Any types of reinforced concrete products are quite heavy, including floor slabs. But this is their only drawback during installation, which in itself is quite convenient. The main requirement for laying is a horizontal and even plane of the support on which the slabs will be mounted. When the wall is foam concrete, brick or laid from crumbly shell rock, then an additional concrete armored belt is needed.

Another point is the area of ​​​​support for floor slabs during installation. Best Option when it is at least 120 mm on each end side. The mortar to be laid under the slabs is used semi-dry. When using floor slabs with voids, it is important to observe such conditions where the temperature regime and general level humidity will not be higher than normal. Anchoring, or a bunch of plates, is done by welding - to connect the plates to each other using a 12 mm rod. Open voids with high-quality laying should be sealed at the edges mineral insulation and closed cement mixture. This prevents the plates from freezing in frosty times.

Floor slabs - this type of reinforced concrete products will be discussed in this article.

All modern designs buildings in their own way production process are divided into two large groups:

• buildings from monolithic concrete
• precast concrete buildings and structures

Comparison of floor slabs and monolith

Each of these groups has advantages and disadvantages. Monolithic structures of buildings and structures have the main and indisputable advantage - you can make almost any conceivable and unthinkable form, embodying the architect's creative visions. Another equally important advantage is that monolithic structures are more durable, due to the fact that the steel frame of the reinforcement passes through all the structures of the building as a single whole. At the same time, the amount of concrete and the thickness of the bearing supports can be reduced, which can also affect the budget in a positive way.

Precast concrete buildings have their own advantages. First of all, these are the terms of the construction of the structure - all parts of the future building are brought to the construction site already ready-made, and the monolith gains strength after 28 days, although at large construction sites the next floor is already being erected in 1.5-2 weeks, after the previous floor has been poured. Plus, thanks to a standardized and automated production process, all products receive quality standards within established regulatory limits.

It is also worth noting that the costs for the work of people and equipment during the construction of buildings from precast concrete are significantly lower. For example, if when pouring a floor slab with a monolith at an estimated cost of concrete of 3,000 rubles per 1 cubic meter of concrete, the work of builders will cost about 3 thousand rubles per 1 cubic meter of poured concrete, the work includes the cost of knitting or welding the reinforcing cage, installation of formwork and pouring concrete. The total price is about 6 thousand rubles per 1 cubic meter of the finished product.

With a floor area of ​​100 square meters, pouring a floor slab 20 cm thick will cost 100 x 0.2 x 6000 = 120,000 thousand rubles. But don't forget about metal frame. Let's take for calculation reinforcement 10 mm, mesh (cell pitch) 20cm. for our volume, about 100 bars of reinforcement are needed (the length of the bar is 11.7 meters), this is for one level of the grid, for two, respectively, 200. This is about 1.5 tons of metal, with a metal price of 32 thousand per ton, the price is 48 thousand rubles. You can also throw 2 thousand on the knitting wire and plugs (linings so that the reinforcing mesh does not touch the formwork - concrete after pouring should protect the steel reinforcement from the action environment). Total 170 thousand rubles.

At the same time, to cover this space with hollow core slabs, 12 floor slabs. The overall dimensions of the slabs for the calculation are taken 6300 x 1500 (Floor slabs PK 63-15), by area it turns out that 11 slabs are needed, but it usually happens that the slabs are stacked in two equal rows (for example, if the house is 12m X 8.5m) , and the protruding remains of the plates are usually sawn off with a diamond wheel for a grinder or beaten off with a crowbar in the direction of the longitudinal hole of the plate. Because it is not always possible to make a house according to the project, with dimensions adjusted to the dimensions of the plates. Although if we are talking about high-rise building, then in this case all dimensions are consistent with the standard dimensions of factory reinforced concrete products.

So, 12 plates, the cost of a PK-63-15 plate is about 10,000 thousand rubles, delivery around the city is about 4.5 thousand per flight, a maximum of 4 plates in the back (we are talking about new and not used plates). 3 flights is 13.5 thousand rubles plus the cost of the plates is 120 thousand rubles.

Laying 12 slabs is a maximum of 3 hours of work, the cost of renting a crane is 1.5 thousand rubles per hour, at least 3 hours is a total of 4.5 thousand. Payment to workers for a stove is a maximum of 500 rubles (although 2 helpers of 500 rubles a day, under strict guidance, can work wonders). Total 6 thousand. In total it turns out 144 thousand rubles. This example shows a difference of 26 thousand rubles, although for the real case you need to calculate separately. But there will always be a small savings on finished reinforced concrete if we compare good-quality workers pouring a monolith and new reinforced concrete structures.

Areas of application for floor slabs

Floor slabs have received a very wide application, and this is perhaps the most used type of reinforced concrete products. They are used to cover spans up to 9 meters, although the most common type of slabs are 6300mm long slabs. Basements, basement floors, interfloor ceilings - these plates are used everywhere. In multi-storey construction, slabs have also received wide use, especially in the Soviet period where the speed of construction was important - it was necessary to provide housing big number citizens.

Currently, floor slabs are also often used in country cottages.

In the industrial construction of plant shops, U-shaped (when viewed in section) slabs are most often used, which are marked as PKZH slabs. These are lightweight structures designed to create roofs of industrial buildings and structures that are inherently unable to carry such loads as hollow, especially for industrial equipment. Their main purpose is the roof of the building.

The most common size is 6000 x 3000mm. Because of oversized of these plates, a trawl is used for transportation - a long platform attached to a tractor. Also, to transport oversized cargo, you need to take care of a pass for oversized special vehicles at the local traffic police in advance, they will give official permission and a clear route so as not to load the main streets of the city.

Floor slab laying

Floor slabs are laid on the bearing walls of the building. Structurally, they should be based on bearing wall not less than 12 cm, although during unreliable construction there were cases when builders laid a slab resting on 2 cm, but this is absolutely not worth doing. SNiP accurately indicates the value of 12 cm. The slabs are laid dry or on the mortar, and when laying the slab on the mortar, it is easier to level it after laying. It is also necessary to observe the technological seam between the plates with a size of 5-20 cm, which, after laying, is filled with mortar.

Before installing the plate, it must be carefully inspected. Boards that have cracks with an opening of more than 1 mm along the entire length of the board are not allowed to be used. When using such a floor slab under load, the reinforcement may come out of the concrete and the slab has a chance to break. At the same time, small shrinkage cracks of not more than 1 mm in opening width are allowed by Sneap.

Floor slab production technology

Floor slabs, like most other reinforced concrete structures, are obtained by molding a concrete mass. The metal form is a pallet and opening sides, one of the sides on the short side of the form has holes for the entry of poissons - pipes that create voids in the slabs. The voids serve to lighten the mass of the finished slab and save concrete.

In the production shop, the whole process looks like this. The form rises to the vibrating table. The electromagnet turns on and the form sticks to the vibrating table.

A worker places a pre-welded lower reinforcement cage (a lower cage made of thicker reinforcement) into the mold. Poissons enter the form from the side, filling part of the space. The upper reinforcing mesh is placed on top. A concrete paver drives up to the beam crane and fills the form of the slab with mortar.

Also on the crane beam, the form is covered with a metal cover. The vibrating table is turned on and the mold begins to vibrate so that the concrete is compacted. After the cover is removed, and then the poissons leave the mold. In the compacted concrete, voids form, and the form is then sent for drying to the steaming chamber, where it stays for about a day, for the speedy setting of the concrete. Well, a day later, ready-made floor slabs are stored at the warehouse site.

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, they are usually installed assembly crane, 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 bottom is the surface 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 applied to it Decoration 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 multiply the area by permissible load for 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 standards and regulations, 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

For large-panel buildings for various purposes hollow slabs must be used. 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 fittings.

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). 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 sizes: 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. Thickness 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 will be manufactured at the factory, then in the process, state standards. They guarantee high quality products and compliance with 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 thermal insulation properties buildings.

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.