Pile axis deviation tolerances. Control when installing monolithic grillages

A survey of the quality of the work performed on the installation of a strip monolithic reinforced concrete foundation of a single-apartment, residential building under construction was carried out and the reasons for the appearance of cracks in the monolithic concrete foundation were determined.

During the inspection, a selective control of concrete strength was carried out by a mechanical non-destructive method in accordance with GOST 22690 and an ultrasonic method in accordance with GOST 17624-87 using an ultrasonic device "Beton-12". In the places where cracks appeared, 2 pits were made, at the location of the cracks, soil samples were taken from under the base of the foundation. Soundings were made in the zone of cracks. At the time of the survey, the work on the construction of the reinforced concrete foundation was fully completed. No installation work was carried out on the above-ground part. There is no load on the foundation. Photographs were taken at the site.

1. Determination of the quality of the work performed, geometric values \u200b\u200band deviations of the foundation

Scheme of measuring the deviation values \u200b\u200bwhen checking the quality of the work performed by the CM on the installation of a monolithic foundation

When carrying out instrumental measurements with measuring equipment, deviations made during the device were recorded. strip foundation more permissible values \u200b\u200bin SNiP 3.03.01-87. During the examination, the following deviations were recorded:

1. The foundation is made with a deviation from the design alignment axes up to 60 mm.
2. When carrying out control measurements, it was found that the deviations of the geometric parameters of the foundation exceed the maximum established values \u200b\u200bin SNiP 3.03.01-87 "BEARING AND GUARDING STRUCTURES": local unevenness of the foundation surface up to 70mm, deviation from the vertical up to 80mm.
3. Due to the deviation of the foundation from the design axes, there are places with a concrete cover less than 5 mm thick. In accordance with the classifier of defects "CLASSIFIER OF THE MAIN KINDS OF DEFECTS IN THE CONSTRUCTION AND BUILDING MATERIALS INDUSTRY" the defect is significant- a defect, in the presence of which the operational characteristics of construction products and their durability are significantly deteriorated. The defect must be eliminated before it can be hidden by subsequent work.
4. During the laying, the concrete was not sufficiently vibrated, after pouring the concrete was not cared for (observance of the temperature and humidity conditions during concrete hardening), as evidenced by hairline cracks of sh.r. 0.1mm, pores, craters).

2. Inspection of the foundation for cracks

Location of cracks in the foundation.

2.1. Description of the structure at the probe location in the G / 1 axes (in the crack zone)

In a wall 160mm thick, transverse reinforcement is made with a step of 200mm, from reinforcement dm. 8mm. Vertical fittings dm. 12mm, with a step of 200mm. The wall rests on the base of the foundation at elev. -1.890 (node \u200b\u200b3 of art. P sheet 15). The examination revealed the absence of ligation of reinforcing bars dm. 12mm lintel reinforcement cage 200mm wide with 160mm thick wall cladding reinforcement cage.

There is no ligation of transverse reinforcement dm in the cladding wall 160mm thick. 6mm with vertical reinforcement dm 12mm.

In a wall 400mm thick, the step corresponds to the design value of 200mm. The dressing was not performed in some places.

2.2 Description of the structure at the probe location in the G / 4 axes (in the crack zone)

At the junction of the foundation strips in the G / 4 axes, the presence of uncleaned formwork and wooden beams was found. Reinforcing cross bars dm. The 8mm reinforcing cage of the foundation strips in the G4 / 6 axes are not tied to the rods of the foundation strip in the A / I - 4 axes. Only the lower rows are connected using "L" shaped reinforcing bars. As a result, the joint of the foundation tapes along the D / 4 axis is weakened.

2.3 Holes in axes G / 1, G / 4

2.3.1 Under the base of the building foundation, sand bed, during the examination, no concrete preparation was found, which should be 100 mm thick, made of concrete B15. (Stage P, sheet 5). Hidden compaction certificate sand pillow was not provided.

During the survey, a discrepancy was found between the work performed on the reinforcement device and the project. During the examination, the following deviations were revealed:

1. Reinforcement of the foundation was carried out in violation of SNiP 3.03.01 - 87 "Bearing and enclosing structures" section 2 of Table 9 and the project.
2. The wall for cladding with a thickness of 160 mm is made with support on the base of the foundation, which is a deviation from the project (KZh-1, item R sheet 3).
3. Not found concrete preparation with a thickness of 100mm, provided for by the project (KZh1 st. R sheet5).
4. During visual inspection, shells and pores are observed on the surface of the concrete structure. During installation, the concrete is not sufficiently vibrated. Concrete work was performed in violation of SNiP 3.03.01 - 87 "Bearing and enclosing structures" Section 2.
5. Due to the lack of access, it is not possible to carry out instrumental control of the foundation sole.

3. Determination of the strength of in-situ concrete foundation.

Table # 1

trials Age of concrete	Design name.		Indications sclerometer-OMSh-1 value h rebound	value	Indication U.z prbor	value	Strength kgf / cm2 Concrete grade and strength class
More than 28 days	foundation						(84% of the design strength М350 В25)
	foundation						(51% of the design strength М350 В25)
	foundation						(58% of the design strength М350 В25)

Conclusion based on the results of a survey of the quality of work performed on the construction of a monolithic foundation:

1. The foundation was made in violation of the design and norms of SNiP 3.03.01-87 "BEARING AND FENCING STRUCTURES".
2. It is necessary to take measures to correct the admitted defects before starting to perform subsequent work.
3. The reason for the appearance of cracks in the foundation is poorly performed reinforcement work in violation of SNiP 3.03.01 - 87 "Supporting and enclosing structures" Section 2 Table 9.
4. The foundation was made with a deviation from the design, the work on the foundation was carried out in violation of SNiP 3.03.01 - 87 "Bearing and enclosing structures" Section 2.
5. The strength of concrete foundations aged more than 28 days, in axes 1/7-A, Zh / A-1, is 84% \u200b\u200bof the design strength. The strength of concrete foundations in axes A / E-1 and 3/7-B and 7 / B-G at the age of 10 to 21 days is 51-58% of the design strength.
6. During visual inspection, shells and pores are observed on the surface of the concrete structure. There are vertical shrinkage hairline cracks in the foundation with an opening width of 0.1-0.2mm.
7. When laying, the concrete is not sufficiently vibrated; after pouring, the concrete is not cared for (compliance with the temperature and humidity conditions during concrete hardening).

AND)Align the foundation by additional concreting with M300 sand concrete in sections of the structure that have irregularities and deviations from the alignment axes.

When leveling a concrete surface, take the following measures:

• Carry out the device of additional reinforcement. Drill reinforcing rods Ø8 A-III with a length of 10 cm into the existing foundation with a step of 200x200. to a depth of 7cm.
• Surface preparation. Before concreting, prepare the surface of the existing foundation (clean, dust off, prime with cement milk).
• At the age of 28 days, check the strength of the concrete.

B) Carry out measures to strengthen the foundation in the crack zone, namely, to strengthen or restore the reinforcement at the corners of the foundation and at the junctions or to take it into the cage underground part foundation (at the discretion of the designer). These measures must be taken to increase the rigidity of the foundation, which in the future will perceive the load from the ground part of the building.

Table 10

Parameter	Parameter value
1. Accuracy of formwork manufacturing:
inventory	According to working drawings and technical conditions - not lower than H14; h14; ± ---------- according to GOST 25346-82 and GOST 25347-82; for shaping elements - h14	Technical inspection, registration
pneumatic	According to technical conditions
2. Defectiveness level	No more than 1.5% at normal control level	Measuring according to GOST 18242-72
3. Accuracy of installation of inventory formwork:	± _____ in accordance with GOST 25346-82 and GOST 25347-82
including:
unique and special structures	Defined by the project
low-turnover and (or) non-inventory during the construction of structures, the surface of which is not subject to accuracy requirements	By agreement with the customer may be lower
for structures ready for painting without putty	Differences in surfaces, including butt ones, no more than 2 mm
for structures ready for wallpapering	The same, no more than 1 mm
4. Installation accuracy and surface quality permanent formwork- facing	Determined by the quality of the cladding surface	Measuring, all elements, work log
5. Accuracy of installation of fixed formwork, which performs the function of external reinforcement	Defined by the project
6. Formwork turnover	GOST 23478-79
7. Deflection of the assembled formwork:		Registration, work log
vertical surfaces	1/400 span	Controlled at factory
slabs	1/500 span	tests and at the construction site
8. Minimum strength of unloaded concrete monolithic structures when stripping surfaces:		Measuring in accordance with GOST 10180-78, GOST 18105-86, work log
vertical from the condition of maintaining the shape
horizontal and inclined in flight:
	70% of the design
	80% of the design
9. Minimum strength of concrete during stripping of loaded structures, including from overlying concrete (concrete mix)	Determined by the PM and agreed with the design organization

RECEPTION OF CONCRETE AND REINFORCED CONCRETE STRUCTURES

OR PARTS OF STRUCTURES

2.111. When accepting finished concrete and reinforced concrete structures or parts of structures should be checked:

compliance of structures with working drawings;

the quality of concrete for strength, and, if necessary, for frost resistance, water resistance and other indicators specified in the project;

the quality of materials used in the construction, semi-finished products and products.

2.112. Acceptance of finished concrete and reinforced concrete structures or parts of structures should be drawn up in accordance with the established procedure by an inspection certificate hidden works or an act of acceptance of critical structures.

2.113. Requirements for finished concrete and reinforced concrete structures or parts of structures are given in table. eleven.

Table 11

Parameter	Limit deviations	Control (method, volume, type of registration)
1. Deviation of lines of intersection planes from the vertical or design slope for the entire height of structures for:
foundations		Measuring,
walls and columns supporting monolithic coverings and ceilings		each structural element, work log
walls and columns supporting prefabricated beam structures
walls of buildings and structures erected in sliding formwork, in the absence of intermediate floors	1/500 of the height of the structure, but not more	Measuring, all walls and lines of their intersection, work log
walls of buildings and structures erected in sliding formwork, in the presence of intermediate floors	1/1000 of the height of the structure, but not more than 50 mm
2. Deviation of horizontal planes for the entire length of the area to be verified		Measuring, at least 5 measurements for every 50 100 m, work log
3. Local unevenness of the concrete surface when checking with a two-meter rail, except for supporting surfaces
4. Length or span of elements
5. Size of the cross-section of elements
6. Marks of surfaces and embedded products that serve as supports for steel or precast reinforced concrete columns and other prefabricated elements		Measuring, each reference element, actuator circuit
7. The slope of the supporting surfaces of foundations when supporting steel columns without grout		The same, every foundation, executive scheme
8. Location anchor bolts:
in plan within the contour of the support		The same, everyone
		foundation bolt,
in height		executive scheme
9. The difference in elevation at the junction of two adjacent surfaces		The same, each joint, executive scheme

3. INSTALLATION OF PRECAUTED CONCRETE CONCRETE

AND CONCRETE STRUCTURES

GENERAL INSTRUCTIONS

3.1. Preliminary storage of structures in on-site warehouses is allowed only with appropriate justification. The on-site warehouse should be located in the area of \u200b\u200bthe assembly crane.

3.2. Installation of structures of each overlying floor (tier) of a multi-storey building should be carried out after the design fixing of all mounting elements and the concrete (mortar) reaching the monolithic joints of the supporting structures of the strength specified in the PPR.

3.3. In cases where the strength and stability of structures during the assembly process are ensured by welding the mounting joints, it is allowed, with the appropriate indication in the project, to mount structures of several floors (tiers) of buildings without monolithing the joints. At the same time, the project must provide the necessary instructions on the procedure for assembling structures, welding joints and embedding joints.

3.4. In cases where permanent connections do not ensure the stability of structures during their assembly, it is necessary to use temporary assembly connections. The design and number of ties, as well as the order of their installation and removal, should be indicated in the PPR.

3.5. The grades of the solutions used in the installation of structures for the device of the bed must be indicated in the project. The fluidity of the solution should be 5-7 cm at the immersion depth of a standard cone, except for cases specifically stipulated in the project.

3.6. The use of a solution, the setting process of which has already begun, as well as the restoration of its plasticity by adding water is not allowed.

3.7. Limit deviations from alignment of landmarks when installing prefabricated elements, as well as deviations of completed installation structures from the design position should not exceed the values \u200b\u200bgiven in table. 12.

Table 12

Parameter	Limit deviations, mm	Control (method, volume, type of registration)
1. Deviation from the alignment of the installation guidelines of the foundation blocks and foundation nozzles with the risks of alignment axes
2. Deviation of the marks of the supporting surface of the bottom of the foundation glasses from the design ones:
before the device of the leveling layer along the bottom of the glass
after the device of the leveling layer along the bottom of the glass
3. Deviation from alignment of landmarks (lines of geometric axes, faces) in the lower section of installed elements with reference landmarks (risks of geometric axes or edges of underlying elements, risks of alignment axes):
columns, panels and large blocks load-bearing walls, volumetric blocks
curtain wall panels		Measuring, each element, work log
girders, purlins, beams, crane beams, roof trusses, roof beams and trusses
4. Deviation of the axes of the columns of one-story buildings in the upper section from the vertical with the length of the columns, m:		Measuring, each element, geodetic executive scheme
| 8 | 16
| 16 | 25
5. Deviation from alignment of landmarks (lines of geometric axes) in the upper section of the columns of multi-storey buildings with risks of alignment axes with the length of the columns, m:
| 8 | 16
| 16 | 25
6. The difference in top marks
columns or their support sites (brackets, consoles) of one-story buildings and structures with the length of the columns, m:
| 8 | 16
| 16 | 25
7. The difference in the marks of the top of the columns of each tier of a multi-storey building and structure, as well as the top wall panels frame buildings within the verified area with:
contact installation
installation of beacons
8. Deviation from alignment of landmarks (lines of geometric axes, faces) in the upper section of installed elements (girders, purlins, beams, trusses, roof trusses and beams) on a support with setting landmarks (risks of geometric axes or faces of downstream elements, risks of alignment axes ) at the height of the element on the support, m:		Measuring, each element, work log
st. 1 to 1.6
| 1,6 | 2,5
| 2,5 | 4
9. Deviation from symmetry (half of the difference in the depth of support of the ends of the element) when installing girders, girders, beams, crane beams, trusses, trusses (beams), floor slabs and floors in the direction of the span to be covered with the length of the element, m:
| 8 | 16
| 16 | 25
10. The distance between the axes of the upper chords of trusses and beams in the middle of the span
11. Deviation from the vertical of the top of the planes:
load-bearing wall panels and volumetric blocks		Measuring, each element, geodetic executive scheme
large blocks of load-bearing walls
partitions, curtain wall panels		Measuring, each element, work log
12. The difference in the marks of the front surfaces of two adjacent unstressed floor panels (slabs) in the seam with the length of the slabs, m:
| 8 | 16
13. The difference between the elevations of the upper flanges of the crane beams and rails:		Measuring, on each support, geodesic
on two adjacent columns along a row with a distance between columns l, m:		executive scheme
on columns
in span
14. Deviation in height of the threshold of the doorway of the volumetric element of the elevator shaft relative to the landing site		Measuring, each element, geodetic executive scheme
15. Deviation from the perpendicularity of the inner surface of the walls of the elevator shaft relative to the horizontal plane (pit floor)		Measuring, each element, geodetic executive scheme

The designation adopted in table. 12: n is the ordinal number of the tier of columns or the number of panels installed in height.

Note. The depth of support of horizontal elements on bearing structures must be at least as specified in the project.

This fact indicates a violation of the requirements of SNiP 3.03.01-87 LOADING AND GUARDING STRUCTURES, table 11, according to which the maximum deviations of the location of the anchor bolts in the plan within the contour are 5 mm.

SNiP 3.03.01-87 LOADING AND GUARDING STRUCTURES RECEPTION OF CONCRETE AND REINFORCED CONCRETE STRUCTURES OR PARTS OF STRUCTURES

2.113. Requirements for finished concrete and reinforced concrete structures or parts of structures are given in table. eleven.

Table 11

Parameter	Limit deviations	Control (method, volume, type of registration)
1. Deviation of lines of intersection planes from the vertical or design slope for the entire height of structures for:
foundations		Measuring,
walls and columns supporting monolithic coverings and ceilings		each structural element, work log
walls and columns supporting prefabricated beam structures
walls of buildings and structures erected in sliding formwork, in the absence of intermediate floors	1/500 of the height of the structure, but not more	Measuring, all walls and lines of their intersection, work log
walls of buildings and structures erected in sliding formwork, in the presence of intermediate floors	1/1000 of the height of the structure, but not more than 50 mm
2. Deviation of horizontal planes for the entire length of the area to be verified		Measuring, at least 5 measurements for every 50 100 m, work log
3. Local unevenness of the concrete surface when checking with a two-meter rail, except for supporting surfaces
4. Length or span of elements		Measuring, each element, work log
5. Size of the cross-section of elements
6. Marks of surfaces and embedded products that serve as supports for steel or precast reinforced concrete columns and other prefabricated elements		Measuring, each reference element, actuator circuit
7. The slope of the supporting surfaces of foundations when supporting steel columns without grout		The same, every foundation, executive scheme
8. Location of anchor bolts:
in plan within the contour of the support		The same, everyone
		foundation bolt,
in height		executive scheme
9. The difference in elevation at the junction of two adjacent surfaces		The same, each joint, executive scheme

Expert opinion - according to the expert opinion, the elimination of these violations of the requirements of regulatory and technical documents is not possible without dismantling the monolithic structures, since during installation supporting elements on the anchor, the arrangement of columns in compliance with the geometric parameters in accordance with the project is impossible. In the case of this arrangement of columns, there will be a redistribution of loads on the foundations.

Construction control

Scope of operations and controls

Preparatory work	Check:		General work log, act of acceptance of previously performed work, passports (certificates)
	- availability of certificates for previously performed work;	Visual
	- correct installation and reliability of fastening the formwork, supporting scaffolding, fastenings and scaffolding;	Technical inspection
	- readiness of all mechanisms and devices that ensure production concrete works;	Visual
	- cleanliness of the pile heads, the previously laid concrete layer and the inner surface of the formwork;	Also
	- the presence of grease on the inner surface of the formwork;	Also
	- the state of fittings and embedded parts, their compliance with the design;	Technical inspection, measuring
	- a leader of the design elevation of the top of the concreting on the inner surface of the formwork.	Measuring

Concrete placement, concrete hardening, stripping	To control:		General work log
	- the quality of the concrete mix;	Laboratory
	- the state of the formwork;	Technical inspection
	- the height of the dumping of the concrete mixture, the thickness of the layers to be laid, the step of rearranging the deep vibrators, the depth of their immersion, the duration of vibration, the correctness of the working seams;	Measuring, 2 times per shift
	- temperature and humidity conditions of concrete hardening;	Measuring, in places of certain PPR
	- the actual strength of the concrete and the timing of formwork.	Measuring at least once for the entire volume of stripping

Acceptance of completed works	Check:		Acceptance certificate of work performed, executive geodetic scheme
	- the actual strength of the concrete;	Laboratory
	- the quality of the grillage surface, the geometric dimensions of the grillage, compliance with the design position of the entire structure;	Visual, measuring, every structural element
	- the quality of the materials used in the construction.	Visual

Control and measuring tool: plumb bob, tape measure, metal ruler, level, theodolite, two-meter rail, tacheometer.

Operational control is carried out: foreman (foreman), construction laboratory engineer, surveyor - in the process of performing work. Acceptance control is carried out: quality service workers, foreman (foreman), surveyor, representatives of the customer's technical supervision.

Note: the operational control of the surveyor during the concreting process is possible only for the purpose of monitoring deformations, the formwork adjustment at this moment is unacceptable, because affects the change in the continuity of the concrete mixture and the formation of voids in it.

Technical requirements and limit deviations

SNiP 3.02.01-87 " Earthworks, foundations and foundations. ", Table 18 (excerpts from the table) or SP 45.13330.2012" Earthworks, foundations and foundations. ", Table 12.1 (excerpts from the table),

SNiP 3.03.01-87 "Bearing and enclosing structures", table. 11 or SP 70.13330.2012 "Bearing and enclosing structures", tab. 5.12

5. Size of the cross-section of the grillage	+6 mm; -3 mm	Also
(from the joint venture) at the size< 200 мм	+6 mm
(from the joint venture) with a size \u003d 400 mm	+11 mm; -3 mm
(from the joint venture) with a size\u003e 2000 mm	+25 mm; -9 mm
(from SP) intermediate dimensions are interpolated

SP 70.13330.2012 "Bearing and enclosing structures", Table X.1 - Classes concrete surfaces

A3

2

4,5

7

9,5

A4

3

7,5

10,5

14

A6

5

10

12

15

Requirements for the quality of materials

GOST R 52085-2003 "Formwork. General specifications." (excerpts)

6.2.5 Round timber should be used for timber bearing and supporting elements conifers I - II grade according to GOST 9463 "Round timber of coniferous species. Technical conditions", table. 2 (excerpts from the table),

coniferous sawn timber of I - II grade according to GOST 8486 "Softwood sawn timber. Technical conditions".

6.2.6 Faced (laminated) birch plywood shall be used for the formwork deck of the 1st and 2nd classes; for the 2nd class, combined veneered plywood can also be used; for the 3rd class - softwood sawn timber in accordance with GOST 8486 "Softwood sawn timber. Technical conditions" and hardwood according to GOST 2695 "Hardwood sawn timber. Technical conditions" not lower than grade II, chipboards according to GOST 10632 "Chipboards. Specifications ", fiberboards according to GOST 4598" Fiber boards. Specifications ", bakelized plywood according to GOST 11539" Bakelized plywood. Specifications ", FSF plywood according to GOST 3916.1" General purpose plywood with outer layers of hardwood veneer. Specifications ", GOST 3916.2" General purpose plywood with outer layers of coniferous veneer. Specifications "and other materials.

Note - the grades of timber and sawn timber are determined depending on the number and size of wood defects (knots, rot, etc.) according to the above-mentioned GOSTs.

GOST 23478-79 "Formwork for the construction of monolithic concrete and reinforced concrete structures. Classification and general technical requirements"(GOST is not valid in the Russian Federation)

4.14 Deck boards should have a width of no more than 150 mm, the moisture content of the wood used for the deck should be no more than 18%, for supporting elements - no more than 22%.

4.20 The elements of the formwork must fit tightly to each other during assembly. Slots in butt joints should not be more than 2 mm.

GOST 10922-2012 "Reinforcement and embedded products, their welded, knitted and mechanical joints for reinforced concrete structures. General specifications", p. 5.3, table. 1 (excerpts from the table)

5.6 On the elements of reinforcement products and embedded parts, there should be no peeling rust and scale, as well as traces of oil, bitumen and other contaminants.

GOST 23279-85 "Welded reinforcing meshes for reinforced concrete structures and products. Specifications"

3.15 Maximum deviations from the straightness of the mesh rods should not exceed 6 mm per 1 m of the mesh length.

GOST 7473-2010 "Concrete mixtures. Specifications."

8.2 Prior to the start of delivery of concrete mix of a given quality, the consumer has the right to demand from the manufacturer (supplier) information on the quality of the materials used and the nominal composition of the concrete mix, as well as the results of preliminary tests of the concrete mix of this nominal composition and concrete for all indicators specified in the supply contract. This information is presented in the cards for the selection of the concrete composition.

8.4 When supplying ready-mixed concrete of a given quality, the manufacturer (supplier) must provide the consumer in a printed and certified form with the following accompanying documentation:

• for each batch of concrete mix - a document on the quality of the concrete mix and a test report for determining the standardized indicators of the quality of concrete;
• for each load of concrete mix - consignment note;
• additionally (if specified in the supply contract), the manufacturer must provide the consumer with information in accordance with 8.2.

8.5 When supplying ready-mixed concrete of a given composition, the manufacturer must provide the consumer in a printed and certified form with the following accompanying documentation:

• for each load of concrete mix - a waybill and a document on the quality of the concrete mix;
• for each batch of concrete mix - copies of passports for the materials used;
• additionally (if specified in the supply contract), the manufacturer must provide the consumer with protocols for determining the quality indicators of the concrete mix and concrete.

Work instructions

SNiP 3.03.01-87 "Bearing and enclosing structures" pp. 2.8 - 2.13, 2.100, 2.109, 2.110 or SP 70.13330.2012 "Bearing and Fencing Structures" p. 5.3.1 - 5.3.15, 5.17.1, 5.17.4-5.17.8

Before concreting, the base must be cleaned of debris, dirt, oils, snow, ice, cement film, after which the cleaned surfaces must be rinsed with water and dried with a stream of air. Reinforcement, correct installation and fastening of the formwork must be accepted according to the act. Reinforcement of the grillage should be carried out according to the project. Installation and acceptance of the formwork, stripping must be carried out according to PPR. Concrete mixtures should be placed in the structure in layers of the same thickness. When compacting the concrete mixture, it is not allowed to rest the vibrators on the reinforcement, embedded products, formwork fastening elements. The depth of immersion of the deep vibrator into the concrete mixture should ensure its deepening into the previously laid layer by 5 - 10 cm, the permutation step should not exceed one and a half radius of its action. The height of free throwing of the concrete mixture into the formwork should not exceed 3 m. Laying the next layer of the concrete mixture is allowed before the beginning of the setting of the concrete of the previous layer. The upper level of the laid concrete mix must be 50 - 70 mm below the top of the formwork panels. The thickness of the layers of the concrete mixture to be laid should not exceed 1.25 of the length of the working part of the vibrator. The surface of the working joints, which are made during the laying of the concrete mixture at intervals, must be perpendicular to the axis of the grillage within the middle third of the span. The resumption of concreting is allowed to be performed when the concrete reaches a strength of at least 1.5 MPa. Measures for the care of concrete, control over their implementation and the timing of demoulding should be established by the PPR. The minimum concrete strength when removing the grillage must be at least 70% of the design.

To the main