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Testing of concrete GOST 22690. Determination of strength by mechanical methods of non-destructive testing. Technique for linking the calibration dependence

V.A.Klevtsov, Doctor of Engineering. Sciences (topic leader); M.G. Korevitskaya, Ph.D. tech. sciences; Yu.K.Matveev; V.N. Artamonova; N.S. Vostrova; A.A.Grebenik; G.V.Sizov, Ph.D. tech. sciences; D.A.Korshunov, Ph.D. tech. sciences; M.V.Sidorenko, Ph.D. tech. sciences; Yu.I.Kurash, Ph.D. tech. sciences; A.M. Leshchinsky, Ph.D. tech. sciences; V.R. Abramovsky; V.A. Dorf, Ph.D. tech. sciences; E.G. Sorkin, Ph.D. tech. sciences; V.L.Chernyakhovsky, Ph.D. tech. sciences; I.O. Krol, Ph.D. tech. sciences; S.Ya. Khomutchenko; Y.E. Ganin; O.Yu. Sammal, Ph.D. tech. sciences; A.A.Rulkov, Ph.D. tech. sciences; P.L. Talberg; A.I.Markov, Ph.D. tech. sciences; R.O.Krasnovsky, Ph.D. tech. sciences; L.S. Pavlov, Ph.D. tech. sciences; M.Yu. Leshchinsky, Ph.D. tech. sciences; G.A. Tselykovsky; I.E.Shkolnik, Ph.D. tech. sciences; T.Yu.Lapenis, G.I. Weingarten, Ph.D. tech. sciences; N.B. Zhukovskaya; S.P. Abramova; I.N. Nagornyak

This standard applies to heavy and lightweight concrete and establishes methods for determining compressive strength in structures by elastic rebound, impact impulse, plastic deformation, tearing, rib spalling, and tearing with shearing.

The dimensions of the imprint on the concrete (diameter, depth, etc.) or the ratio of the diameters of the imprints on the concrete and the standard sample when the indenter hits or the indenter is pressed into the concrete surface;

The value of the stress required for local destruction of concrete when tearing off something glued to it metal disk, equal to the tearing force divided by the area of projection of the concrete tearing surface onto the plane of the disk;

1.3. Mechanical methods non-destructive testing used to determine the strength of concrete of all types of standardized strength, controlled according to GOST 18105, as well as to determine the strength of concrete during inspection and rejection of structures.

1.4. Tests are carried out at positive concrete temperatures. When examining structures, it is allowed to determine the strength at a negative temperature, but not lower than minus 10 °C, provided that at the time of freezing the structure was at least one week at a positive temperature and relative humidity air no more than 75%.

1.5. The compliance of the actual concrete strength values obtained using the methods given in this standard with the established requirements is assessed according to GOST 18105.

2.1. The strength of concrete is determined using instruments designed to determine indirect characteristics that have passed metrological certification according to GOST 8.326* and meet the requirements given in Table 2.

Name of device characteristics	Characteristics of instruments for the method
	elastic rebound	shock pulse	plastic deformation	separation	chipping ribs	separation with chipping
Hardness of the striker, striker or indenter HRCе, not less
Roughness of the contact part of the striker or indenter, µm, no more
Diameter of striker or indenter, mm, not less
Thickness of disk indenter edges, mm, not less	10
Conical indenter angle	30-60°
Indentation diameter, % of indenter diameter	20-70
Perpendicularity tolerance when applying a load at a height of 100 mm, mm
Impact energy, J, not less	0,02
Rate of load increase, kN/s	1,5*	0,5-1,5	0,5-1,5	1,5-3,0
Load measurement error from measured load, %, no more	5*

2.2. A tool for measuring the diameter or depth of indentations (angular scale according to GOST 427, calipers according to GOST 166, etc.), used for the plastic deformation method, must provide measurements with an error of no more than ±0.1 mm, and a tool for measuring indentation depth (indicator clock type according to GOST 577, etc.) - with an error of no more than ±0.01 mm.

It is also possible to use other anchor devices, the embedment depth of which must be no less than the maximum size of the coarse concrete aggregate of the structure being tested.

2.5. For the tear-off method, steel disks with a diameter of at least 40 mm, a thickness of at least 6 mm and at least 0.1 diameter, with a roughness parameter of the glued surface of at least 20 microns according to GOST 2789 should be used. The adhesive for gluing the disk must provide strength at which

3.1. To determine the strength of concrete in structures, a calibration relationship is first established between the strength of concrete and an indirect characteristic of strength (in the form of a graph, table or formula).

For the tear-off method with shearing, in the case of using anchor devices in accordance with Appendix 2, and for the rib shearing method, in the case of using devices in accordance with Appendix 3, it is allowed to use the calibration dependencies given in Appendices 5 and 6, respectively.

Compressive strength of concrete is the main indicator that characterizes concrete.

There are two systems for expressing this indicator:

Compressive strength of concrete is the main indicator that characterizes concrete. This is what non-destructive testing of concrete strength in monolithic structures. There are two systems for expressing this indicator:

Concrete class, B - this is the so-called cube strength (i.e. a compressible sample in the shape of a cube), showing the withstand pressure in MPa. The probability of destruction during concrete strength testing does not exceed 5 units out of 100 tested samples. It is designated by the Latin letter B and a number indicating the strength in MPa. According to SNiP 2.03.01–84 “Concrete and reinforced concrete structures”.
Concrete grade, M - this is the compressive strength of concrete, kgf/cm². It is designated by the Latin letter M and numbers from 50 to 1000. The maximum deviation that allows for monitoring and assessing the strength of concrete according to GOST 26633–91 “Heavy and fine-grained concrete is 13.5%.

The concrete grade and class are determined 28 days from the date of pouring, if normal conditions, or the calculation is carried out taking into account the coefficient (after 7–14 days the material acquires 60–80% of brand strength, after 28 days approximately 100%, after 90 days -130%.). The ultrasonic method of non-destructive testing of concrete is carried out, as a rule, at the intermediate and design age of a reinforced concrete structure.

The strength of concrete is influenced by a number of factors: cement activity, cement content, ratio of water to cement by mass, quality of aggregates, quality of mixing and degree of compaction, age and curing conditions of concrete, repeated vibration. The rate of hardening of concrete is greatly influenced by the temperature and humidity of the environment. An environment with a temperature of 15–20°C and an air humidity of 90–100% is considered conditionally normal. With increasing cement content in concrete, its strength increases to a certain limit. Then it grows slightly, but other properties of concrete deteriorate: shrinkage and creep increase. Therefore, it is not recommended to add more than 600 kg of cement per 1 m³ of concrete.

Compliance of concrete grade (M) with class (B) and compressive strength

Concrete grade, M	Concrete class, B	Strength, MPa	Strength, kg/cm 2

Chip-off method occupies a special place among non-destructive methods for determining the strength of concrete. Considered a non-destructive method, the peeling method is essentially a destructive method, since the strength of concrete is assessed by the force required to destroy a small volume of concrete, which allows the most accurate assessment of its actual strength. Therefore, this method is used not only to determine the strength of concrete of unknown composition, but can also serve to construct calibration dependencies for other non-destructive testing methods. This method is applied to heavy concrete and structural concrete with light aggregates in monolithic and prefabricated concrete and reinforced concrete products, structures and structures and establishes a method for testing concrete and determining its compressive strength by local destruction of concrete when tearing out a special anchor device from it. Such ultrasonic method for testing concrete strength allows you to determine the compressive strength of concrete in the strength range from 5.0 to 100.0 MPa. When developing the standard, materials from GOST 22690–88 were used.

One of the most common and effective ways Non-destructive testing for determining the strength of concrete is measured with a sclerometer, or as it is also called, a Schmidt hammer.

Methods for determining the strength of concrete: equipment used

Using the devices presented below, you can test concrete non-destructively. This makes it possible to more accurately predict the physical characteristics of finished products. reinforced concrete structures, which means minimizing losses construction organization and protect the customer from all sorts of troubles.

Among other things, such concrete quality control allows for inspections of concrete whose temperature has dropped below 0ºC. Traditional methods concrete quality control in laboratory conditions cannot boast of such convenience: previously it was necessary to take a sample and check it at room temperature in laboratory conditions. Interesting modern solution also because contractors may not resort to the services of specialized organizations at each stage construction work. In turn, specialists can independently come to the site and conduct an examination of the quality of concrete in accordance with GOST standards. The equipment is quite compact and mobile, and preparing the results takes a minimum of time.

Equipment used

Schmidt hammer Original Schmidt type N

Testing concrete products using a Schmidt hammer Original Schmidt is the most common measurement method worldwide that does not destroy concrete in accordance with GOST 22690-2015

For each specific type of testing of concrete products, Proceq offers the appropriate hammer model.

Schmidt hammer models available for testing concrete products type Original Schmidt with different impact energies for testing materials of various types and sizes.

Our N, NR, L and LR hammers are specifically designed for assessing the quality and compressive strength of concrete products with a range of 10 to 70 N/mm2 (1,450 to 10,152 psi).

Models with built-in paper recorders (LR and NR) are capable of automatically recording rebound values on a paper tape.

Type Approval Certificate SI Brochure Schmidt Hammers

POS-50MG4 "Skol" is intended for non-destructive testing of concrete strength by methods of edge chipping, tearing with chipping and tearing of steel disks in accordance with GOST 22690-2015.

Measuring the strength of concrete using such equipment is allowed both on projects under construction and finished buildings. The device is indispensable in construction industry, in the work of public utilities and restoration bureaus, which periodically check the integrity of buildings. The model received a non-volatile memory in which the last two hundred measurement results are stored. They are marked with the concrete grade and the exact date of the analysis, allowing specialists to easily track the dynamics of changes in key indicators.

The goals, basic principles and basic procedure for carrying out work on interstate standardization are established by GOST 1.0-92 “Interstate standardization system. Basic provisions" and GOST 1.2-2009 "Interstate standardization system. Interstate standards, rules and recommendations for interstate standardization. Rules for development, adoption, application, updating and cancellation"

1 DEVELOPED by the structural unit of JSC "Scientific Research Center "Construction" Scientific Research, Design and Technological Institute of Concrete and Reinforced Concrete named after. A.A. Gvozdeva (NIIZhB)

2 INTRODUCED by the Technical Committee for Standardization TC 465 “Construction”

3 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (protocol dated June 18, 2015 No. 47)

Short name of the country according to MK (ISO 3166) 004-97	Code of the country according to MK (ISO 3166) 004-97	Abbreviated name of the national authority on standardization
Armenia		Ministry of Economy of the Republic of Armenia
Belarus		State Standard of the Republic of Belarus
Kazakhstan		Gosstandart of the Republic of Kazakhstan
Kyrgyzstan		Kyrgyzstandard
Moldova		Moldova-Standard
Russia		Rosstandart
Tajikistan		Tajikstandard

4 By Order of the Federal Agency for Technical Regulation and Metrology dated September 25, 2015 No. 1378-st, the interstate standard GOST 22690-2015 was put into effect as a national standard of the Russian Federation on April 1, 2016.

5 This standard takes into account the main regulatory provisions regarding the requirements for mechanical methods of non-destructive testing of concrete strength of the following European regional standards:

EN 12504-2:2001 Testing concrete in structures - Part2: Non-destructive testing - Determination of rebound number;

EN 12504-3:2005 Testing concrete in structures - Determination of pull-outforce.

Level of conformity - nonequivalent (NEQ)

Information about changes to this standard is published in the annual information index " National standards", and the text of changes and amendments is in the monthly information index "National Standards". In case of revision (replacement) or cancellation of this standard, the corresponding notice will be published in the monthly information index “National Standards”. Relevant information, notices and texts are also posted in information system common use- on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet

GOST 22690-2015

Concrete
Determination of strength by mechanical methods of nondestructive testing

Date of introduction - 2016-04-01

1 area of use

This standard applies to structural heavy, fine-grained, lightweight and prestressing concrete of monolithic, prefabricated and prefabricated concrete and reinforced concrete products, structures and structures (hereinafter referred to as structures) and establishes mechanical methods for determining the compressive strength of concrete in structures by elastic rebound, impact impulse , plastic deformation, tearing, rib chipping and tearing with chipping.

2 Normative references

This standard uses normative references to the following interstate standards:

Note - Standard test schemes are applicable over a limited range of concrete strengths (see annexes And ). For cases not related to standard test schemes, calibration dependencies should be established according to general rules.

4.6 The test method should be selected taking into account the data given in the table and additional restrictions established by the manufacturers of specific measuring instruments. The use of methods outside the ranges of concrete strength recommended in the table is permitted with scientific and technical justification based on the results of research using measuring instruments that have passed metrological certification for an extended range of concrete strength.

Table 1

Method name	Limit values of concrete strength, MPa
Elastic rebound and plastic deformation	5 - 50
Impact impulse	5 - 150
Breakaway	5 - 60
Rib chipping	10 - 70
Separation with chipping	5 - 100

4.7 Determination of the strength of heavy concrete of design classes B60 and above or with average compressive strength of concrete Rm≥ 70 MPa in monolithic structures must be carried out taking into account the provisions of GOST 31914.

4.8 The strength of concrete is determined in areas of structures that do not have visible damage (detachment of the protective layer, cracks, cavities, etc.).

4.9 The age of the concrete of the controlled structures and its sections should not differ from the age of the concrete of the structures (sections, samples) tested to establish the calibration dependence by more than 25%. Exceptions are strength control and the construction of a calibration relationship for concrete whose age exceeds two months. In this case, the difference in the age of individual structures (sites, samples) is not regulated.

4.10 Tests are carried out at positive concrete temperatures. It is allowed to carry out tests at a negative temperature of concrete, but not lower than minus 10 ° C, when establishing or linking a calibration dependence taking into account the requirements. The temperature of the concrete during testing must correspond to the temperature specified by the operating conditions of the devices.

Calibration dependencies established at concrete temperatures below 0 °C are not allowed to be used at positive temperatures.

4.11 If it is necessary to test concrete structures after heat treatment at surface temperature T≥ 40 °C (to control the tempering, transfer and formwork strength of concrete) the calibration dependence is established after determining the strength of concrete in the structure by an indirect non-destructive method at temperature t = (T± 10) °C, and testing concrete by direct non-destructive method or testing samples - after cooling at normal temperature.

5 Measuring instruments, equipment and tools

5.1 Measuring instruments and instruments for mechanical testing intended to determine the strength of concrete must be certified and verified in the prescribed manner and must comply with the requirements of the application.

5.2 The readings of instruments calibrated in units of concrete strength should be considered as an indirect indicator of the strength of concrete. These devices should be used only after establishing the calibration relationship “device reading - concrete strength” or linking the relationship established in the device in accordance with.

5.3 A tool for measuring the diameter of indentations (calipers according to GOST 166), used for the plastic deformation method, must provide measurement with an error of no more than 0.1 mm, a tool for measuring the depth of an indentation (dial indicator according to GOST 577, etc.) - with an error no more than 0.01 mm.

5.4 Standard testing schemes for the peel-off and rib shear method provide for the use of anchor devices and grips in accordance with the applications and.

5.5 For the peeling method, anchor devices should be used, the embedment depth of which should be no less than the maximum size of the coarse concrete aggregate of the structure being tested.

5.6 For the tear-off method, steel disks with a diameter of at least 40 mm, a thickness of at least 6 mm and a diameter of at least 0.1, with a roughness of the adhesive surface of at least Ra= 20 microns according to GOST 2789. The adhesive for gluing the disc must ensure adhesion strength to the concrete, at which destruction occurs along the concrete.

6 Preparation for testing

6.1.1 Preparation for testing includes checking the instruments used in accordance with the instructions for their operation and establishing calibration relationships between the strength of concrete and an indirect characteristic of strength.

6.1.2 The calibration dependence is established based on the following data:

The results of parallel tests of the same sections of structures using one of the indirect methods and the direct non-destructive method for determining the strength of concrete;

The results of testing sections of structures using one of the indirect non-destructive methods for determining the strength of concrete and testing core samples selected from the same sections of the structure and tested in accordance with GOST 28570;

Results of testing standard concrete samples using one of the indirect non-destructive methods for determining the strength of concrete and mechanical tests in accordance with GOST 10180.

6.1.3 For indirect non-destructive methods for determining the strength of concrete, a calibration dependence is established for each type of standardized strength specified in for concrete of the same nominal composition.

It is allowed to build one calibration relationship for concrete of the same type with one type of coarse aggregate, with a single production technology, differing in nominal composition and value of standardized strength, subject to compliance with the requirements.

6.1.4 The permissible difference in the age of concrete of individual structures (sections, samples) when establishing a calibration dependence on the age of concrete of the controlled structure is taken according to .

6.1.5 For direct non-destructive methods, it is allowed to use the dependencies given in the appendices for all types of standardized strength of concrete.

6.1.6 The calibration dependence must have a standard (residual) deviation S T . H. M , not exceeding 15% of the average value of the concrete strength of the sections or samples used in constructing the relationship, and the correlation coefficient (index) of not less than 0.7.

Recommended to use linear dependence type R = a + bK(Where R- concrete strength, K- indirect indicator). The methodology for establishing, evaluating parameters and determining the conditions for using a linear calibration relationship is given in the Appendix.

6.1.7 When constructing a calibration dependence of the deviation of unit values of concrete strength R i f from the average value of the concrete strength of the sections or samples used to construct the calibration dependence must be within the limits:

From 0.5 to 1.5 of the average concrete strength at ≤ 20 MPa;

From 0.6 to 1.4 average concrete strength at 20 MPa< ≤ 50 МПа;

From 0.7 to 1.3 average concrete strength at 50 MPa< ≤ 80 МПа;

From 0.8 to 1.2 of the average concrete strength at > 80 MPa.

6.1.8 Correction of the established relationship for concrete at intermediate and design ages should be carried out at least once a month, taking into account additionally obtained test results. The number of samples or areas of additional testing when making adjustments must be at least three. The adjustment method is given in the Appendix.

6.1.9 It is allowed to use indirect non-destructive methods for determining the strength of concrete, using calibration dependencies established for concrete that differs from the test in composition, age, hardening conditions, humidity, with reference in accordance with the methodology in the Appendix.

6.1.10 Without reference to specific conditions of the application, calibration dependencies established for concrete different from the one being tested can only be used to obtain approximate strength values. It is not allowed to use indicative strength values without reference to specific conditions to assess the strength class of concrete.

Then select areas in the quantity provided for, where the maximum, minimum and intermediate values of the indirect indicator are obtained.

After testing by the indirect non-destructive method, sections are tested by the direct non-destructive method or samples are taken for testing according to GOST 28570.

6.2.4 To determine the strength at a negative temperature of concrete, the areas selected for constructing or linking the calibration dependence are first tested by an indirect non-destructive method, and then samples are taken for subsequent testing at a positive temperature or heated external sources heat ( infrared emitters, heat guns etc.) to a depth of 50 mm to a temperature not lower than 0 °C and tested using a direct non-destructive method. The temperature of heated concrete is monitored at the depth of installation of the anchor device in a prepared hole or along the surface of a chip in a non-contact manner using a pyrometer in accordance with GOST 28243.

Rejection of test results used to construct a calibration curve at a negative temperature is allowed only if the deviations are associated with a violation of the test procedure. In this case, the rejected result must be replaced by the results of repeated testing in the same area of the structure.

6.3.1 When constructing a calibration dependence based on control samples, the dependence is established using single values of the indirect indicator and the strength of concrete of standard cube samples.

The average value of indirect indicators for a series of samples or for one sample (if the calibration dependence is established for individual samples) is taken as a single value of an indirect indicator. The strength of concrete in a series according to GOST 10180 or one sample (calibration dependence for individual samples) is taken as a single value of concrete strength. Mechanical tests of samples in accordance with GOST 10180 are carried out immediately after testing by the indirect non-destructive method.

6.3.2 When constructing a calibration curve based on the results of testing cube samples, use at least 15 series of cube samples in accordance with GOST 10180 or at least 30 individual cube samples. Samples are made in accordance with the requirements of GOST 10180 in different shifts, for at least 3 days, from concrete of the same nominal composition, using the same technology, under the same hardening regime as the structure to be controlled.

The unit values of the concrete strength of the cube samples used to construct the calibration relationship must correspond to the deviations expected in production, and at the same time be within the ranges established in.

6.3.3 The calibration dependence for the methods of elastic rebound, shock impulse, plastic deformation, rib separation and spalling is established based on the results of tests of manufactured cube samples, first by a non-destructive method, and then by a destructive method according to GOST 10180.

When establishing the calibration dependence for the peeling method, main and control samples are made according to. An indirect characteristic is determined on the main samples, control samples are tested according to GOST 10180. The main and control samples must be made of the same concrete and harden under the same conditions.

6.3.4 Sample sizes should be selected in accordance with the largest aggregate size in concrete mixture according to GOST 10180, but not less than:

100×100×100 mm for the rebound, shock impulse, plastic deformation methods, as well as for the peeling method (control samples);

200×200×200 mm for the method of chopping the edge of the structure;

300×300×300 mm, but with an edge size of at least six installation depths of the anchor device for the peeling method (main samples).

6.3.5 To determine indirect strength characteristics, tests are carried out in accordance with the requirements of the section on the lateral (in the direction of concreting) faces of cube samples.

The total number of measurements on each sample for the method of elastic rebound, shock impulse, plastic deformation upon impact must be no less than the established number of tests in the area according to the table, and the distance between the impact points must be at least 30 mm (15 mm for the shock impulse method). For the method of plastic deformation during indentation, the number of tests on each face must be at least two, and the distance between test sites must be at least twice the diameter of the indents.

When establishing a calibration relationship for the rib shearing method, one test is carried out on each side rib.

When establishing the calibration dependence for the peel-off method, one test is carried out on each side face of the main sample.

6.3.6 When tested by the method of elastic rebound, shock impulse, or plastic deformation upon impact, samples must be clamped in a press with a force of at least (30 ± 5) kN and no more than 10% of the expected value of the breaking load.

6.3.7 Specimens tested by the tearing method are installed on the press so that the surfaces on which the tearing was carried out do not adhere to the support plates of the press. Test results according to GOST 10180 increase by 5%.

7 Testing

7.1.1 The number and location of controlled sections in structures must comply with the requirements of GOST 18105 and be indicated in project documentation on the structure or installed taking into account:

Control tasks (definition actual class concrete, stripping or tempering strength, identification of areas of reduced strength, etc.);

Type of structure (columns, beams, slabs, etc.);

Placement of grips and concreting order;

Reinforcement of structures.

The rules for assigning the number of test sites for monolithic and prefabricated structures when monitoring the strength of concrete are given in the Appendix. When determining the strength of concrete of the structures being surveyed, the number and location of sections should be taken according to the survey program.

7.1.2 Tests are carried out on a section of the structure with an area of 100 to 900 cm2.

7.1.3 The total number of measurements in each section, the distance between the measurement locations in the section and from the edge of the structure, the thickness of the structures in the measurement section must be no less than the values given in the table depending on the test method.

Table 2 - Requirements for test areas

Method name	Total number measurements Location on	Minimum distance between measurement locations on the site, mm	Minimum edge distance structures to place measurements, mm	Minimum thickness structures, mm
Elastic rebound
Impact impulse
Plastic deformation
Rib chipping
Breakaway		2 diameters disk
Separation with chipping at working depth of anchor embeddingh:
≥ 40mm
< 40мм

7.1.4 The deviation of individual measurement results at each section from the arithmetic mean value of the measurement results for a given section should not exceed 10%. Measurement results that do not satisfy the specified condition are not taken into account when calculating the arithmetic mean value of the indirect indicator for a given area. The total number of measurements at each site when calculating the arithmetic mean must comply with the requirements of the table.

7.1.5 The strength of concrete in the controlled section of the structure is determined by the average value of the indirect indicator according to the calibration relationship established in accordance with the requirements of section, provided that the calculated value of the indirect indicator is within the established (or linked) relationship (between the smallest and highest values strength).

7.1.6 The surface roughness of a section of concrete structures when tested by rebound, shock impulse, and plastic deformation methods must correspond to the surface roughness of sections of a structure (or cubes) tested when establishing the calibration relationship. If necessary, it is allowed to clean the surfaces of the structure.

When using the indentation plastic deformation method, if the zero reading is removed after applying the initial load, there are no requirements for the surface roughness of the concrete structure.

7.2.1 Tests are carried out in the following sequence:

It is recommended that the position of the device when testing the structure relative to the horizontal be the same as when establishing the calibration dependence. In a different position of the device, it is necessary to make corrections to the indicators in accordance with the operating instructions for the device;

7.3.1 Tests are carried out in the following sequence:

The device is positioned so that the force is applied perpendicular to the surface under test in accordance with the operating instructions for the device;

When using a spherical indenter to facilitate measurements of the diameters of prints, the test can be carried out through sheets of carbon and white paper (in this case, tests to establish the calibration dependence are carried out using the same paper);

The values of the indirect characteristic are recorded in accordance with the operating instructions for the device;

The average value of the indirect characteristic on the section of the structure is calculated.

7.4.1 Tests are carried out in the following sequence:

The device is positioned so that the force is applied perpendicular to the surface under test in accordance with the operating instructions for the device;

It is recommended to take the position of the device when testing the structure relative to the horizontal the same as during testing when establishing the calibration dependence. In a different position of the device, it is necessary to make corrections to the readings in accordance with the operating instructions for the device;

Record the value of the indirect characteristic in accordance with the operating instructions for the device;

The average value of the indirect characteristic on the section of the structure is calculated.

7.5.1 When testing by the pull-out method, the sections should be located in the zone of lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.

7.5.2 The test is carried out in the following sequence:

At the place where the disc is glued, remove surface layer concrete 0.5 - 1 mm deep and clean the surface from dust;

The disc is glued to the concrete by pressing the disc and removing excess glue outside the disc;

The device is connected to the disk;

The load is gradually increased at a speed of (1 ± 0.3) kN/s;

The projection area of the separation surface on the plane of the disk is measured with an error of ± 0.5 cm 2 ;

The value of the conditional stress in concrete during tearing is determined as the ratio of the maximum tearing force to the projected area of the tearing surface.

7.5.3 The test results are not taken into account if the reinforcement was exposed during concrete separation or the projection area of the separation surface was less than 80% of the disk area.

7.6.1 When testing by the peel-off method, the sections should be located in the zone of lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.

7.6.2 Tests are carried out in the following sequence:

If the anchor device was not installed before concreting, then a hole is made in the concrete, the size of which is selected in accordance with the operating instructions for the device, depending on the type of anchor device;

The anchor device is fixed into the hole to the depth specified in the operating instructions for the device, depending on the type of anchor device;

The device is connected to an anchor device;

The load is increased at a speed of 1.5 - 3.0 kN/s;

Record the reading of the force meter of the device R 0 and the amount of anchor slip Δ h(the difference between the actual tear-out depth and the embedding depth of the anchor device) with an accuracy of at least 0.1 mm.

7.6.3 Measured pullout force value R 0 is multiplied by the correction factor γ, determined by the formula

Where h- working depth of the anchor device, mm;

Δ h- the amount of anchor slippage, mm.

7.6.4 If the largest and smallest sizes the torn out part of concrete from the anchor device to the limits of destruction on the surface of the structure differs by more than two times, and also if the depth of the torn out differs from the depth of embedding of the anchor device by more than 5% (Δ h > 0,05h, γ > 1.1), then the test results can be taken into account only for an approximate assessment of the strength of concrete.

Note - Approximate values of concrete strength are not allowed to be used to assess the strength class of concrete and construct calibration dependencies.

7.6.5 The test results are not taken into account if the depth of the pullout differs from the depth of embedding of the anchor device by more than 10% (Δ h > 0,1h) or the reinforcement was exposed at a distance from the anchor device less than the depth of its embedding.

7.7.1 When tested by the rib shearing method, there should be no cracks, concrete edges, sagging or cavities in the test area with a height (depth) of more than 5 mm. The sections should be located in the zone of least stress caused by the operational load or the compression force of the prestressed reinforcement.

7.7.2 The test is carried out in the following sequence:

The device is fixed to the structure, a load is applied at a speed of no more than (1 ± 0.3) kN/s;

Record the reading of the force meter of the device;

Measure the actual chipping depth;

The average value of the shearing force is determined.

7.7.3 The test results are not taken into account if the reinforcement was exposed during concrete chipping or the actual chipping depth differed from the specified depth by more than 2 mm.

8 Processing and presentation of results

8.1 The test results are presented in a table in which they indicate:

Type of design;

Design class of concrete;

Age of concrete;

The strength of the concrete of each controlled area according to;

Average strength of concrete structure;

Areas of the structure or parts thereof, subject to compliance.

The form of the table for presenting test results is given in the Appendix.

8.2 Processing and assessment of compliance with established requirements of the actual strength of concrete obtained using the methods given in this standard is carried out in accordance with GOST 18105.

Note - Statistical assessment of the class of concrete based on test results is carried out according to GOST 18105 (schemes “A”, “B” or “C”) in cases where the strength of concrete is determined by a calibration relationship constructed in accordance with section . When using previously installed dependencies by linking them (by application ) statistical control is not allowed, and concrete class assessment is carried out only according to the “D” scheme GOST 18105.

8.3 The results of determining the strength of concrete using mechanical non-destructive testing methods are documented in a conclusion (protocol), which provides the following data:

About the tested structures, indicating the design class, the date of concreting and testing, or the age of the concrete at the time of testing;

About the methods used to control the strength of concrete;

About types of devices with serial numbers, information about verification of devices;

About the accepted calibration dependencies (dependence equation, dependency parameters, compliance with the conditions for applying the calibration dependency);

Used to construct a calibration relationship or its reference (date and results of tests using non-destructive indirect and direct or destructive methods, correction factors);

On the number of sections for determining the strength of concrete in structures, indicating their location;

Test results;

Methodology, results of processing and evaluation of the data obtained.

Appendix A
(required)
Standard test scheme for the peel-off test

A.1 The standard test scheme for the peel-off method involves testing subject to the requirements -.

A.2 The standard test scheme is applicable in the following cases:

Tests heavy concrete compressive strength from 5 to 100 MPa;

Tests lightweight concrete compressive strength from 5 to 40 MPa;

The maximum fraction of coarse concrete aggregate is not more than the working depth of embedding anchor devices.

A.3 The supports of the loading device must be evenly adjacent to the concrete surface at a distance of at least 2 h from the axis of the anchor device, where h- working depth of the anchor device. The test diagram is shown in the figure.

1 2 - support for the loading device;
3 - grip of the loading device; 4 - transition elements, rods; 5 - anchor device;
6 - pulled out concrete (tearout cone); 7 - test structure

Figure A.1 - Scheme of the peel-off test

A.4 The standard testing scheme for the peel-off method provides for the use of three types of anchor devices (see figure). Type I anchor device is installed in the structure during concreting. Anchor devices of types II and III are installed in holes previously prepared in the structure.

1 - working rod; 2 - working rod with expansion cone; 3 - segmented grooved cheeks;
4 - support rod; 5 - working rod with a hollow expansion cone; 6 - leveling washer

Figure A.2 - Types of anchor devices for standard test scheme

A.5 Parameters of anchor devices and their permissible ranges of measured concrete strength at standard scheme tests are listed in the table. For lightweight concrete, the standard test scheme uses only anchor devices with an embedment depth of 48 mm.

Table A.1 - Parameters of anchor devices for standard test scheme

Anchor type devices	Anchor diameter devicesd, mm	Depth of embedding anchor devices, mm		Acceptable for anchor device strength measurement range for concrete compression, MPa
Anchor type devices	Anchor diameter devicesd, mm	working h	full h"	heavy	lung
				45 - 75
				10 - 50	10 - 40
				40 - 100
				5 - 100	5 - 40
				10 - 50

A.6 The designs of anchors of types II and III must ensure preliminary (before applying the load) compression of the walls of the hole at the working embedment depth h and post-test slip monitoring.

Appendix B
(required)
Standard rib splitting test scheme

B.1 The standard testing scheme by the rib shearing method provides for testing subject to the requirements -.

B.2 The standard test scheme is applicable in the following cases:

The maximum fraction of coarse concrete aggregate is no more than 40 mm;

Testing of heavy concrete with compressive strength from 10 to 70 MPa on granite and limestone crushed stone.

B.3 For testing, a device is used, consisting of a force exciter with a force measuring unit and a gripper with a bracket for local chipping of the structure edge. The test diagram is shown in the figure.

1 - a device with a loading device and a force meter; 2 - support frame;
3 - chipped concrete; 4 - test structure; 5 - grip with bracket

Figure B.1 - Scheme of testing using the rib shearing method

B.4 In case of local chipping of a rib, the following parameters must be ensured:

Shearing depth a= (20 ± 2) mm;

Cleaving Width b= (30 ± 0.5) mm;

The angle between the direction of the load and the normal to the loaded surface of the structure β = (18 ± 1)°.

Appendix B
(recommended)
Calibration dependence for the peel-off method

When testing by the peel-off method according to the standard scheme according to the appendix, the cubic compressive strength of concrete R, MPa, can be calculated using the calibration dependence using the formula

R = m 1 m 2 P,

Where m 1 - coefficient taking into account the maximum size of coarse aggregate in the tear-out zone, taken equal to 1 when the aggregate size is less than 50 mm;

m 2 - proportionality coefficient for the transition from tearing force in kilonewtons to concrete strength in megapascals;

R- pullout force of the anchor device, kN.

When testing heavy concrete with a strength of 5 MPa or more and light concrete with a strength from 5 to 40 MPa, the values of the proportionality coefficient m 2 is taken according to the table.

Table B.1

Anchor type devices	Range measurable concrete strength compression, MPa	Anchor diameter devicesd, mm	Anchor embedment depth devices, mm	Coefficient valuem 2 for concrete
Anchor type devices	Range measurable concrete strength compression, MPa	Anchor diameter devicesd, mm	Anchor embedment depth devices, mm	heavy	lung
	45 - 75
	10 - 50
	40 - 75
	5 - 75
	10 - 50

Odds m 2 when testing heavy concrete with an average strength above 70 MPa should be taken according to GOST 31914.

Appendix D
(recommended)
Calibration dependence for the rib shearing method
with standard test scheme

When testing by the rib shearing method according to the standard scheme according to the appendix, the cubic compressive strength of concrete on granite and crushed limestone R, MPa, can be calculated using the calibration dependence using the formula

R = 0,058m(30R + R 2),

Where m- coefficient taking into account maximum size coarse aggregate and taken equal to:

1.0 - with aggregate size less than 20 mm;

1.05 - with aggregate size from 20 to 30 mm;

1.1 - with aggregate size from 30 to 40 mm;

R- shearing force, kN.

Appendix D
(required)
Requirements for instruments for mechanical testing

Table E.1

Name of device characteristics

Characteristics of instruments for the method

elastic
rebound

percussion
impulse

plastic
deformation

separation

chipping
ribs

separation from
chipping

Hardness of the striker, striker or indenter HRCе, not less

Roughness of the contact part of the striker or indenter, µm, no more

Diameter of striker or indenter, mm, not less

Thickness of disk indenter edges, mm, not less

Conical indenter angle

30° - 60°

Indentation diameter, % of indenter diameter

20 - 70

Perpendicularity tolerance when applying a load at a height of 100 mm, mm

Impact energy, J, not less

0,02

Rate of load increase, kN/s The equation for the relationship “indirect characteristic - strength” is taken to be linear according to the formula

E.2 Rejection of test results

After constructing the calibration dependence using formula (), it is adjusted by rejecting individual test results that do not satisfy the condition:

where the average value of concrete strength according to the calibration dependence is calculated using the formula

here are the meanings R i H, R i f, , N- see explanations for formulas (), ().

E.4 Correction of the calibration dependence

Correction of the established calibration dependence, taking into account additionally obtained test results, must be carried out at least once a month.

When adjusting the calibration dependence, at least three new results obtained at the minimum, maximum and intermediate values of the indirect indicator are added to the existing test results.

As data is accumulated to construct a calibration relationship, the results of previous tests, starting with the very first, are rejected so that total number results did not exceed 20. After adding new results and rejecting old ones, the minimum and maximum values of the indirect characteristic, the calibration dependence and its parameters are set again using the formulas () - ().

E.5 Conditions for using the calibration dependence

The use of a calibration relationship to determine the strength of concrete according to this standard is allowed only for values of the indirect characteristic falling in the range from H min to N max.

If the correlation coefficient r < 0,7 или значение , then monitoring and assessing strength based on the obtained dependence are not allowed.

Appendix G
(required)
Technique for linking the calibration dependence

G.1 The strength of concrete, determined using a calibration relationship established for concrete different from the test, is multiplied by the coincidence coefficient K With. Meaning K c is calculated using the formula

Where R OS i- concrete strength in i- section, determined by the tear-off method with chipping or testing of cores according to GOST 28570;

R kosv i- concrete strength in i- section, determined by any indirect method using the calibration dependence used;

n- number of test sites.

G.2 When calculating the coincidence coefficient, the following conditions must be met:

Number of test sites taken into account when calculating the coincidence coefficient, n ≥ 3;

Each private value R OS i /R kosv i should be no less than 0.7 and no more than 1.3:

1 by 4 m length of linear structures;

1 by 4 m2 area of flat structures.

Appendix K
(recommended)
Test results presentation table form

Name of structures (batch of designs), design strength class concrete, concreting date or age of concrete tested designs	Designation 1)	Plot number according to the scheme or location in axes 2)	Strength of concrete, MPa		Strength class concrete 5)
			section 3)	average 4)






1) Brand, symbol and (or) the location of the structure in the axes, zones of the structure, or part of a monolithic and prefabricated monolithic structure (capture), for which the concrete strength class is determined. 2) The total number and location of plots in accordance with . 3) The strength of the concrete of the site in accordance with . 4) Average strength of concrete of a structure, structure zone or part of a monolithic and prefabricated monolithic structure with the number of sections that meet the requirements . 5) Actual strength class of concrete of a structure or part of a monolithic and prefabricated monolithic structure in accordance with paragraphs 7.3 - 7.5 GOST 18105 depending on the selected control scheme. Note - Presentation in the column “Concrete strength class” of estimated class values or values of the required concrete strength for each section separately (assessment of the strength class for one section) is not acceptable.

Key words: structural heavy and light concrete, monolithic and prefabricated concrete and reinforced concrete products, structures and structures, mechanical methods for determining compressive strength, elastic rebound, shock impulse, plastic deformation, tearing, rib spalling, tearing with chipping

INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION

INTERSTATE

STANDARD

CONCRETE

Determination of strength by mechanical methods of non-destructive testing

(EN 12504-2:2001, NEQ)

(EN 12504-3:2005, NEQ)

Official publication

Stand Rtinform 2016

Preface

The goals, basic principles and basic procedure for carrying out work on interstate standardization are established by GOST 1.0-92 “Interstate standardization system. Basic provisions" and GOST 1.2-2009 "Interstate standardization system. Interstate standards. rules and recommendations for interstate standardization. Rules for development, adoption, application, updating and cancellation"

Standard information

1 DEVELOPED by the structural division of JSC “SRC “Construction” Scientific Research. Design and Engineering and Technological Institute of Concrete and Reinforced Concrete named after. A.A. Gvozdeva (NIIZhB)

2 INTRODUCED by the Technical Committee for Standardization TC 465 “Construction”

3 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (protocol dated June 18, 2015 No. 47)

5 8 this standard takes into account the main regulatory provisions regarding the requirements for mechanical methods of non-destructive testing of concrete strength of the following European regional standards:

EN 12504-2:2001 Testing concrete in structures - Part 2: Non-destructive testing - Determination of rebound number;

EN 12504-3:2005 Testing concrete in structures - Determination of pull-out force.

Level of conformity - nonequivalent (NEQ)

6 83AMEN GOST 22690-88

Information about changes to this standard is published in the annual information index “National Standards”, and the text of changes and amendments is published in the monthly information index “National Standards”. In case of revision (replacement) or cancellation of this standard, the corresponding notice will be published in the monthly information index *National Standards." Relevant information, notifications and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet

In the Russian Federation, this standard cannot be reproduced in whole or in part. replicated and distributed as an official publication without permission from the Federal Agency for Technical Regulation and Metrology

Appendix A (normative) Standard peel-off test design. . . 10

INTERSTATE STANDARD

Determination of strength mechanical methods non-destructive testing

Determination of strength by mechanical methods of nondestructive testing

Date of introduction - 2016-04-01

1 area of use

This standard applies to structural heavy, fine-grained, lightweight and pre-cast concrete, precast concrete and reinforced concrete products. structures and structures (hereinafter referred to as structures) and establishes mechanical methods for determining the compressive strength of concrete in structures by elastic rebound, impact impulse, plastic deformation, separation, rib spalling and spalling.

8 of this standard uses regulatory references to the following interstate standards:

GOST 166-89 (ISO 3599-76) Calipers. Specifications

GOST 577-68 Hourly indicators with 0.01 mm division. Specifications

GOST 2789-73 Surface roughness. Parameters and characteristics

GOST 10180-2012 Concrete. Methods for determining strength using control samples

GOST 18105-2010 Concrete. Rules for monitoring and assessing strength

GOST 28243-96 Pyrometers. General technical requirements

GOST 28570-90 Concrete. Methods for determining strength using samples taken from structures

GOST 31914-2012 High-strength, heavy and fine-grained concrete for monolithic structures. Rules for quality control and assessment

Note - When using this standard, it is advisable to check the validity of the reference standards in a public information system - not the official website of the Federal Agency for Technical Regulation and Metrology on the Internet or using the annual information index “National Standards”, which was published as of January 1 of the current year, and on issues of the monthly information index “National Standards” for the current year. If the reference standard is replaced (changed), then when using this standard you should be guided by the replacing (changed) standard. If the reference standard is canceled without replacement, then the provision in which a reference is made to it is applied in the part that does not affect this reference.

3 Terms and definitions

8 of this standard uses terms in accordance with GOST 18105, as well as the following terms with corresponding definitions:

Official publication

destructive methods for determining the strength of concrete: Determination of the strength of concrete using control samples made from a concrete mixture in accordance with GOST 10180 or selected from structures in accordance with GOST 28570.

[GOST 18105-2010. Article 3.1.18]

3.2 non-destructive mechanical methods for determining the strength of concrete: Determination of the strength of concrete directly in the structure under local mechanical impact on concrete (impact, tearing, chipping, indentation, tearing with chipping, elastic rebound).

3.3 indirect non-destructive methods for determining the strength of concrete: Determination of the strength of concrete using pre-established calibration dependencies.

3.4 direct (standard) non-destructive methods for determining the strength of concrete: Methods that provide standard test schemes (tearing with shearing and rib shearing) and allowing the use of known calibration dependencies without reference and adjustment

3.5 calibration relationship: Graphical or analytical relationship between an indirect characteristic of strength and the compressive strength of concrete, determined by one of the destructive or direct non-destructive methods.

3.6 indirect characteristics of strength (indirect indicator): The amount of force applied during local destruction of concrete, the magnitude of rebound, impact energy, indent size or other instrument reading when measuring the strength of concrete by non-destructive mechanical methods.

4 General provisions

4.1 Non-destructive mechanical methods are used to determine the compressive strength of concrete at the intermediate and design ages established by the design documentation and at an age exceeding the design when inspecting structures.

4.2 Non-destructive mechanical methods for determining the strength of concrete established by this standard are divided according to the type of mechanical impact or determined indirect characteristic into the method:

Elastic rebound;

Plastic deformation;

> shock pulse:

Separation with chipping:

Chipping of ribs.

4.3 Non-destructive mechanical methods for determining the strength of concrete are based on the connection between the strength of concrete and indirect strength characteristics:

The elastic rebound method is based on the connection between the strength of concrete and the rebound value of the striker from the concrete surface (or the striker pressed against it);

The method of plastic deformation based on the relationship between the strength of concrete and the dimensions of the imprint on the concrete of the structure (diameter, depth, etc.) or the ratio of the diameter of the imprint on concrete and a standard metal sample upon impact of the indenter or pressing of the indenter into the surface of the concrete;

Impact impulse method on the connection between the strength of concrete and impact energy and its changes at the moment of impact of the striker with the concrete surface;

Method of tearing off the bond of the tension required for local destruction of concrete when tearing off a metal disk glued to it, equal to the tearing force divided by the area of projection of the concrete tearing surface onto the plane of the disk;

The method of separation with shearing is based on the connection between the strength of concrete and the value of the force of local destruction of concrete when an anchor device is dug out of it;

The method of chipping an edge in relation to the strength of concrete with the value of the force required to chip off a section of concrete on the edge of a structure.

4.4 V general case Non-destructive mechanical methods for determining the strength of concrete are indirect non-destructive methods for determining strength. The strength of concrete in structures is determined by experimentally established calibration dependencies.

4.5 The peeling method when testing in accordance with the standard scheme in Appendix A and the rib shearing method when testing in accordance with the standard scheme in Appendix B are direct non-destructive methods for determining the strength of concrete. For direct non-destructive methods, it is allowed to use the calibration dependencies established in Appendices b and D.

Note - Standard test schemes are applicable in a limited range of concrete strength (see Appendices A and B). For cases not related to standard test schemes, grading dependencies should be established according to general rules.

4.6 The test method should be selected taking into account the data given in Table 1 and additional restrictions established by the manufacturers of specific measuring instruments. The use of methods outside the concrete strength ranges recommended in Table 1 is permitted with scientific and technical justification based on the results of research using measuring instruments that have passed metrological certification for an extended range of concrete strength.

Table 1

4.7 Determination of the strength of heavy concrete of design classes B60 and higher or with an average compressive strength of concrete R m i 70 MPa in monolithic structures must be carried out taking into account the provisions of GOST 31914.

4.8 The strength of concrete is determined in areas of structures that do not have visible damage (detachment of the protective layer, cracks, cavities, etc.).

4.10 Tests are carried out at positive concrete temperatures. It is allowed to carry out tests at a negative temperature of concrete, but not lower than minus 10 "C, when establishing or linking a calibration dependence taking into account the requirements of 6.2.4. The temperature of concrete during testing must correspond to the temperature provided for by the operating conditions of the devices.

Calibration dependencies established at concrete temperatures below O * C are not allowed to be used at positive temperatures.

4.11 If it is necessary to test concrete structures after heat treatment at a surface temperature T up to 40 * C (to control the tempering, transfer and formwork strength of concrete), the calibration dependence is established after determining the strength of concrete in the structure by an indirect non-destructive method at a temperature (i (T ± 10) *C, and testing concrete by direct non-destructive method or testing samples - after cooling at normal temperature.

5 Measuring instruments, equipment and tools

5.2 The readings of instruments calibrated in units of concrete strength should be considered as an indirect indicator of the strength of concrete. These devices should only be used after

establishing a calibration relationship “device reading - concrete strength” or linking the relationship established in the device in accordance with 6.1.9.

5.3 A tool for measuring the diameter of indentations (calipers according to GOST 166), used for the plastic deformation method, must provide measurement with an error of no more than 0.1 mm. a tool for measuring the depth of an imprint (a dial indicator according to GOST 577, etc.) - with an error of no more than 0.01 mm.

5.4 Standard testing schemes for the peel-off and rib shear method provide for the use of anchor devices and grips in accordance with Appendices A and B.

5.5 For the chipping method, anchor devices should be used. the depth of embedment of which must be no less than the maximum size of the coarse concrete aggregate of the structure being tested.

5.6 For the tear-off method, steel disks with a diameter of at least 40 mm should be used. thickness of at least 6 mm and at least 0.1 diameter, with roughness parameters of the bonded surface of at least Ra = 20 microns according to GOST 2789. The adhesive for gluing the disc must provide adhesion strength to concrete, at which destruction occurs along the concrete.

6 Preparation for testing

6.1 Procedure for preparing for testing

6.1.2 The calibration dependence is established based on the following data:

The results of parallel tests of the same sections of structures using one of the indirect methods and the direct non-destructive method for determining the strength of concrete;

Results of testing standard concrete samples using one of the indirect non-destructive methods for determining the strength of concrete and mechanical tests according to GOST 10180.

It is allowed to construct one calibration relationship for concrete of the same type with one type of coarse aggregate, with a single production technology, differing in nominal composition and value of standardized strength, subject to the requirements of 6.1.7

6.1.4 The permissible difference in the age of concrete of individual structures (sections, samples) when establishing the calibration dependence on the age of concrete of the controlled structure is taken according to 4.9.

6.1.5 For direct non-destructive methods according to 4.5, it is allowed to use the dependencies given in Appendices C and D for all types of standardized strength of concrete.

6.1.6 The calibration dependence must have a standard (residual) deviation S T n m not exceeding 15% of the average concrete strength of the sections or samples used in constructing the dependence, and a correlation coefficient (index) of at least 0.7.

It is recommended to use a linear relationship of the form R* a*bK (where R is the strength of concrete. K is an indirect indicator). The methodology for establishing, assessing parameters and determining the conditions for using a linear calibration relationship is given in Appendix E.

6.1.7 When constructing a calibration dependence of the deviation of single values of concrete strength R^ from the average value of concrete strength of sections or samples I f. used to construct the calibration dependence must be within the limits:

> from 0.5 to 1.5 of the average concrete strength R f at R f £ 20 MPa;

From 0.6 to 1.4 of the average concrete strength R, f at 20 MPa< Я ф £50 МПа;

From 0.7 to 1.3 of the average concrete strength R f at 50 MPa<Я Ф £80 МПа;

From 0.8 to 1.2 of the average concrete strength R f at R f > 80 MPa.

6.1.10 Without reference to specific conditions in Appendix G, calibration dependencies established for concrete different from the one being tested can only be used to obtain approximate strength values. It is not allowed to use indicative strength values without reference to specific conditions to assess the strength class of concrete.

6.2 Construction of a calibration dependence based on the results of concrete strength tests

in designs

6.2.1 When constructing a calibration dependence based on the results of testing the strength of concrete in structures, the dependence is established based on single values of the indirect indicator and the strength of concrete in the same sections of structures.

The average value of the indirect indicator in the area is taken as a single value of the indirect indicator. The unit strength of concrete is taken as the strength of the concrete of the site, determined by direct non-destructive method or testing of selected samples.

6.2.2 The minimum number of unit values for constructing a calibration relationship based on the results of testing the strength of concrete in structures is 12.

6.2.3 When constructing a calibration relationship based on the results of testing the strength of concrete in structures not subject to testing or their zones, measurements are first carried out using an indirect non-destructive method in accordance with the requirements of Section 7.

Then select areas in the quantity provided for in 6.2.2, where the maximum was obtained. minimum and intermediate values of the indirect indicator.

After testing by the indirect non-destructive method, sections are tested by the direct non-destructive method or samples are taken for testing in accordance with GOST 26570.

6.2.4 To determine the strength at a negative temperature of concrete, the areas selected for constructing or linking the calibration dependence are first tested by an indirect non-destructive method, and then samples are taken for subsequent testing at a positive temperature or heated by external heat sources (infrared emitters, heat guns and etc.) to a depth of 50 mm to a temperature not lower than 0 * C and tested using a direct non-destructive method. The temperature of heated concrete is monitored at the depth of installation of the anchor device in a prepared hole or along the surface of a chip in a non-contact manner using a pyrometer in accordance with GOST 28243.

6.3 Construction of a calibration curve based on control samples

The unit values of the concrete strength of the cube samples used to construct the calibration relationship must correspond to the deviations expected in production, while being within the ranges established in 6.1.7.

When establishing the calibration dependence for the peeling method, main and control samples are made according to 6.3.4. An indirect characteristic is determined on the main samples. control samples are tested according to GOST 10180. The main and control samples must be made of the same concrete and harden under the same conditions.

6.3.4 The dimensions of the samples should be selected in accordance with the largest aggregate size in the concrete mixture in accordance with GOST 10180, but not less than:

100* 100* 100 mm for rebound, shock impulse, plastic deformation methods. as well as for the peeling method (control samples);

200 * 200 * 200 mm for the rib chopping method:

300 * 300 * 300 mm. but with a rib size of at least six installation depths of the anchor device for the tear-off method with chipping (main samples).

6.3.5 To determine indirect strength characteristics, tests are carried out in accordance with the requirements of Section 7 on the lateral (in the direction of concreting) faces of cube samples.

The total number of measurements on each sample for the method of elastic rebound, shock impulse, plastic deformation upon impact must be no less than the established number of tests in the area according to Table 2. and the distance between the impact points must be at least 30 mm (15 mm for the shock impulse method). For the method of plastic deformation during indentation, the number of tests on each face must be at least two, and the distance between test sites must be at least twice the diameter of the indents.

When establishing a calibration relationship for the rib shearing method, one test is carried out on each side rib.

When establishing the calibration dependence for the peeling method, one test is carried out on each side face of the main sample.

6.3.7 Samples tested by the tear-off method are installed on the press like this. so that the surfaces on which the tearing was carried out do not touch the support plates of the press. Test results according to GOST 10180 increase by 5%.

7 Testing

7.1 General requirements

7.1.1 The number and location of controlled sections in structures must comply with the requirements of GOST 18105 and are indicated in the design documentation for the structure or installed taking into account:

Control tasks (determining the actual class of concrete, stripping or tempering strength, identifying areas of reduced strength, etc.);

Type of structure (columns, beams, slabs, etc.);

Placement of grips and concreting order:

Reinforcement of structures.

The rules for assigning the number of test sites for monolithic and prefabricated structures when monitoring the strength of concrete are given in Appendix I. When determining the strength of concrete of the structures being inspected, the number and location of sites must be taken according to the inspection program.

7.1.2 Tests are carried out on a section of the structure with an area of 100 to 900 cm2.

7.1.3 The total number of measurements in each area, the distance between the measurement locations in the area and from the edge of the structure, the thickness of the structures in the measurement area must be no less than the values given in Table 2 depending on the test method.

Table 2 - Requirements for test areas

Method name	Total number of measurements per plot	Minimum distance between measurement points on the site, mm	Minimum distance from the edge of the structure to the measurement point, mm	Minimum thickness structures, mm
Elastic REBOUND
Impact impulse
Plastic deformation
Rib digging
		2 disc diameters
Detachment with chipping at working depth of anchor embedding L: *40mm< 40мм

7.1.5 The strength of concrete in a controlled section of the structure is determined by the average value of the indirect indicator using a calibration relationship established in accordance with the requirements of section 6, provided that the calculated value of the indirect indicator is within the limits of the established (or linked) relationship (between the smallest and largest values strength).

7.1.6 The surface roughness of a section of concrete structures when tested by rebound, shock impulse, and plastic deformation methods must correspond to the surface roughness of sections of a structure (or cubes) tested when establishing the calibration relationship. IN necessary cases It is allowed to clean the surfaces of the structure.

When using the indentation plastic deformation method, if the zero reading is removed after applying the initial load, there are no requirements for the surface roughness of the concrete structure.

7.2 Rebound method

7.2.1 Tests are carried out in the following sequence:

It is recommended to take the same position of the device when testing the structure relative to the horizontal. as when establishing a calibration dependence. In a different position of the device, it is necessary to make adjustments to the indicators in accordance with the operating instructions for the device:

7.3 Plastic deformation method

7.3.1 Tests are carried out in the following sequence:

The device is positioned so that the force is applied perpendicular to the surface under test in accordance with the operating instructions for the device;

When using a spherical indemator to facilitate measurements of the diameters of prints, the test can be carried out through sheets of carbon and white paper (in this case, tests to establish the calibration dependence are carried out using the same paper);

The values of the indirect characteristic are recorded in accordance with the operating instructions for the device;

The average value of the indirect characteristic on the section of the structure is calculated.

7.4 Shock pulse method

7.4.1 Tests are carried out in the following sequence:

The device is positioned like this. so that the force is applied perpendicular to the surface under test in accordance with the operating instructions for the device:

Record the value of the indirect characteristic in accordance with the operating instructions for the device;

The average value of the indirect characteristic on the section of the structure is calculated.

7.5 Tear-off method

7.5.1 When testing by the pull-out method, the sections should be located in the zone of lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.

7.5.2 The test is carried out in the following sequence:

In the place where the disc is glued, remove the surface layer of concrete 0.5-1 mm deep and clean the surface of dust;

The disc is glued to the concrete by pressing the disc and removing excess glue outside the disc;

The laboratory is connected to the disk;

The load is gradually increased at a rate of (1 ±0.3) kN/s;

Record the reading of the force meter of the device;

The projection area of the separation surface on the disk plane is measured with an error of iO.Scm 2 ;

The value of the conditional stress in concrete during tearing is determined as the ratio of the maximum tearing force to the projection area of the tearing surface.

7.5.3 The test results are not taken into account if the reinforcement was exposed during concrete separation or the projection area of the separation surface was less than 80% of the disk area.

7.6 Chip-off method

7.6.1 When testing by the peel-off method, the sections must be located in the zone of lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.

7.6.2 Tests are carried out in the following sequence:

The anchor device is fixed into the hole to the depth specified in the operating instructions for the device, depending on the type of anchor device;

The device is connected with a connection device;

The load is increased at a speed of 1.5-3.0 kN/s:

Record the reading of the force meter of the device P 0 and the amount of slippage of the LP anchor (the difference between the actual depth of the pullout and the depth of embedding of the anchor device) with an accuracy of no less than 0.1 mm.

7.6.3 The measured value of the pullout force P 4 is multiplied by the correction factor y. determined by the formula

where L is the working depth of the anchor device, mm;

DP - the amount of anchor slippage, mm.

7.6.4 If the largest and smallest dimensions of the torn-out part of concrete from the anchor device to the limits of destruction along the surface of the structure differ by more than two times, and also if the depth of the torn-out differs from the depth of embedding of the anchor device by more than 5% (DL > 0.05ft, y > 1.1), then the test results can be taken into account only for an approximate assessment of the strength of concrete.

Note - Approximate values of concrete strength are not allowed to be used to assess the strength class of concrete and construct calibration dependencies.

7.6.5 The test results are not taken into account if the depth of the pullout differs from the depth of embedding of the anchor device by more than 10% (dL > 0.1 A) or the reinforcement was exposed at a distance from the anchor device less than the depth of its embedding.

7.7 Rib splitting method

7.7.2 The test is carried out in the following sequence:

The device is secured to the structure. apply a load at a speed of not more than (1 ±0.3) kN/s;

Record the reading of the force meter of the device;

Measure the actual chipping depth;

The average value of the shearing force is determined.

7.7.3 The test results are not taken into account if the reinforcement was exposed when the concrete was chipped or the actual spalling depth differed from the specified depth by more than 2 mm.

8 Processing and presentation of results

8.1 The test results are presented in a table in which they indicate:

Type of design;

Design class of concrete;

Age of concrete;

The strength of concrete of each controlled area according to 7.1.5;

Average strength of concrete structure;

Areas of the structure or parts thereof, subject to the requirements of 7.1.1.

The form of the table for presenting test results is given in Appendix K.

Note - Statistical assessment of the class of concrete based on test results is carried out according to GOST 18105 (schemes “A”, “B” or “C”) in cases where the strength of concrete is determined by the calibration dependence constructed in in accordance with section 6. When using previously established dependencies by linking them (according to Appendix G), statistical control is not allowed, and concrete class assessment is carried out only according to scheme “G” of GOST 18105.

8.3 The results of determining the strength of concrete using mechanical non-destructive testing methods are documented in a conclusion (protocol), which provides the following data:

About the tested structures, indicating the design class, the date of concreting and testing, or the age of the concrete at the time of testing;

About the methods used to control the strength of concrete;

About types of devices with serial numbers, information about verification of devices;

About the accepted calibration dependencies (dependence equation, dependency parameters, compliance with the conditions for applying the calibration dependency);

Used to construct a calibration relationship or its reference (date and results of tests using non-destructive indirect and direct or destructive methods, correction factors);

On the number of sections for determining the strength of concrete in structures, indicating their location;

Test results;

Methodology, results of processing and evaluation of the data obtained.

Standard test scheme for the peel-off test

A.1 The standard test scheme for the peel-off method requires testing to be carried out in accordance with the requirements of A.2-A.6.

A.2 The standard test scheme is applicable in the following cases:

Tests of heavy concrete with compressive strength from S to 100 MPa:

Tests of lightweight concrete with compressive strength from S to 40 MPa:

The maximum fraction of coarse concrete aggregate is not more than the working depth of embedding anchor devices.

A.3 The supports of the loading device must be evenly adjacent to the concrete surface at a distance of at least 2h from the axis of the anchor device, where L is the working depth of the anchor device. The test scheme is shown in Figure A.1.

1 - device with a loading device and a force meter; 2 - support of the loading device: 3 - grip of the loading device: 4 - transition elements, rods, S - anchor device. 6 - concrete being pulled out (cone tearing): 7 - structure under test

Figure A.1 - Scheme of the peel-off test

A.4 The standard test scheme for the peel-off test involves the use of three types of anchor devices (see Figure A.2). Type I anchor device is installed in the structure during concreting. Anchor devices of types II and ill are installed in pre-prepared holes in the structure.

1 - working rod: 2 - working rod with a different cone: 3 - segmented grooved chips: 4 - support rod: 5 - working rod with a ripe expansion cone: b - leveling washer

Figure A.2 - Types of anchor devices for standard test scheme

A.5 The parameters of anchor devices and their permissible ranges of measured concrete strength under a standard test scheme are indicated in Table A.1. For lightweight concrete, the standard test scheme uses only anchor devices with an embedment depth of 48 mm.

Table A.1 - Parameters of anchor devices for standard test scheme

Type of anchor device	Diameter of anchor device tf. mm	Depth of embedding anchor devices, mm		The permissible range for measuring the compressive strength of concrete for the anchor device. MPa
Type of anchor device	Diameter of anchor device tf. mm	working h	plumper L"	heavy

A.b The designs of anchors of types II and III must ensure preliminary (before applying the load) compression of the hole walls at the working depth of embedding l and control of slippage after testing.

Standard rib splitting test scheme

B.1 The standard testing scheme using the rib shearing method provides for testing in compliance with the requirements B.2-B.4.

B.2 The standard test scheme is applicable in the following cases:

The maximum fraction of coarse concrete aggregate is no more than 40 mm:

Testing of heavy concrete with compressive strength from 10 to 70 MPa on granite and limestone crushed stone. B.Z To carry out tests, use a device consisting of a force exciter with a force measuring unit

crossbar and gripper with a bracket for local chipping of the rib of the structure. The test scheme is shown in Figure B.1.

1 - device with a loading device and a sipometer. 2 - support frame: 3 - concrete to be chipped: 4 - test

design^ - grip with bracket

Figure B.1 - Scheme of testing using the rib shearing method

B.4 In case of local chipping of a rib, the following parameters must be ensured:

Shearing depth a ■ (20 a 2) mm.

Cleaving width 0 "(30 and 0.5) mm;

The angle between the direction of the load and the normal to the loaded surface of the structure p" (18 a 1)*.

Calibration dependence for the peel-off method with a standard test scheme

When testing by the pull-out method with shearing according to the standard scheme in accordance with Appendix A, the cubic strength of concrete is not compressive R. MPa. it is allowed to calculate the grvduiroak dependence according to the formula

I*P)|P>^. (IN 1)

where t, is a coefficient that takes into account the maximum size of coarse aggregate in the breakout zone and is taken equal to 1 when the aggregate size is less than 50 mm:

t 2 - proportionality coefficient for the transition from pullout force in kilonewtons to concrete strength in megapascals:

P is the pullout force of the anchor device. kN.

When testing heavy concrete with a strength of 5 MPa or more and light concrete with a strength of 5 to 40 MPa, the values of the proportionality coefficient t 2 are taken according to Table B.1.

Table 8.1

Type of anchor device	Range of measured compressive strength of concrete. MPa	Diameter of anchor device d. neither	Depth of embedding of anchor device, mm	The value of the coefficient w^ for concrete
Type of anchor device	Range of measured compressive strength of concrete. MPa	Diameter of anchor device d. neither	Depth of embedding of anchor device, mm	heavy

Coefficients t 3 when testing heavy concrete with an average strength above 70 MPa should be taken according to GOST 31914.

Calibration dependence for the rib shearing method with a standard test scheme

When testing the rib shearing method according to the standard scheme in accordance with Appendix B, the cubic compressive strength of concrete on granite and crushed limestone R. MLA. can be calculated using the calibration dependence using the formula

R - 0.058m (30P + PJ). (D.1)

where t is a coefficient that takes into account the maximum size of coarse aggregate and is taken equal to:

1.0 - with aggregate size less than 20 mm:

1.05 - with aggregate size from 20 to 30 mm:

1.1 - with filler size from 30 to 40 mm:

P - shearing force. kN.

Appendix D (mandatory)

Requirements for instruments for mechanical testing

Table E.1

Name of device characteristics

Characteristics of instruments for the method

elastic

percussion

impulse

plastic

deformation

open with skapya* and it

Hardness of the striker, striker or indenter НЯСе. no less

Roughness of the contact part of the striker or indenter. µm. no more

Diameter of the impactor or indenter. mm. no less

Thickness of the edges of the disk indenter. mm. no less

Conical indenter angle

Indentation diameter, % of indenter diameter

Perpendicularity tolerance when applying a load at a height of 100 mm. mm

Energy impact. J. no less

Rate of load increase. kN/s

Load measurement error, h. no more

5 here RjN - see explanation to formula (£.3).

After rejection, the calibration dependence is established again using formulas (£.1) - (E.S) based on the remaining test results. Rejection of the remaining test results is repeated, considering the fulfillment of condition (E.6) when using a new (corrected) calibration dependence.

Partial concrete strength values must satisfy the requirements of 6.1.7.

£.3 Parameters of calibration dependence

For the accepted calibration dependence, determine:

The minimum and maximum values of the indirect characteristic N gave.

Standard deviation^ n m of the constructed calibration dependence according to formula (E.7);

Correlation coefficient of the calibration dependence g according to the formula

where the average value of concrete strength according to the calibration dependence is calculated using the formula

here are the values of R (H. I f.Y f. N - see explanations for formulas (E.E). (E.b).

E.4 Correction of the calibration dependence

Correction of the established calibration dependence, taking into account additionally obtained test results, must be carried out at least once a month.

When adjusting the calibration dependence, at least three new results obtained at the minimum, maximum and intermediate values of the indirect indicator are added to the existing test results.

As data is accumulated to build a calibration relationship, the results of previous tests. starting with the very first ones, they are rejected so that the total number of results does not exceed 20. After adding new results and rejecting old ones, the minimum and maximum values of the indirect characteristic, the calibration dependence and its parameters are set again according to formulas (E.1)-(E.9).

E.S Conditions for using the calibration dependence

If the correlation coefficient r< 0.7 или значение 5 тнм "Я ф >0.15. then monitoring and assessing strength based on the obtained dependence are not allowed.

Technique for linking the calibration dependence

G.1 The value of concrete strength, determined using a calibration relationship established for concrete different from the one being tested, is multiplied by the coincidence coefficient K c. The value is calculated using the formula

where is the strength of concrete in t-th section, determined by the tear-off method or core testing

according to GOST 26570;

I msa, - the strength of concrete in<-м участке, опредепяемвя пюбым косвенным методом по используемой градуировочной зависимости: л - число участков испытаний.

G.2 When calculating the coincidence coefficient, the following conditions must be met:

Number of test sites taken into account when calculating the coincidence coefficient, n i 3;

Each partial value I k,/I (0ca ^should be no less than 0.7 and no more than 1.3:

Each particular value of I^. , should differ from the average value by no more than 15%:

The Yade values do not satisfy the conditions (G.2). (J.Z). should not be taken into account when calculating

coincidence coefficient K s.

Designation of the number of test sites for prefabricated and monolithic structures

I.1 In accordance with GOST 18105, when monitoring the strength of concrete of prefabricated structures (tempered or pre-cast), the number of controlled structures of each type is taken at least 100 and at least 10 structures from the batch. If a batch consists of 12 structures or less, a complete inspection is carried out. In this case, the number of sections must be at least:

1 not 4 m length of linear structures:

1 by 4 m2 area of flat structures.

I.2 In accordance with GOST 18105, when monitoring the strength of concrete of monolithic structures at an intermediate age, at least one structure of each type (column, wall, ceiling, crossbar, etc.) from the controlled batch is controlled using non-airborne methods.

I.Z In accordance with GOST 18105, when monitoring the strength of concrete of monolithic structures at design age, continuous non-destructive testing of the strength of concrete of all structures of the controlled batch is carried out. In this case, the number of test sites must be at least:

3 for each grip for flat structures (wall, ceiling, foundation slab);

1 per 4 m length (or 3 per grip) for each linear horizontal structure (beam, crossbars);

6 per structure - for linear vertical structures (column, pylon).

The total number of measurement sections for calculating the characteristics of the uniformity of concrete strength of a batch of structures must be at least 20.

I.4 The number of single measurements of concrete strength by mechanical methods of non-destructive testing at each site (the number of measurements at the site) is taken according to Table 2.

Test results presentation table form

Most structures (batch of structures), design concrete strength class, date concreting or age of concrete of tested structures	Designation"	1# section w* according to diagram and location on axes 21	Strength of concrete. MPa		Concrete strength class*’
			plot 9"	average 4’






” Mark, symbol and (or) location of the structure in the axes, zone of the structure, or part of a monolithic and prefabricated monolithic structure (capture), for which the strength class of concrete is determined. 11 The total number and location of sites in accordance with 7.1.1. 11 Strength of concrete of the site in accordance with 7.1.5. 41 Average strength of concrete of a structure, structure zone or part of a monolithic and prefabricated monolithic structure with the number of sections that meet the requirements of 7.1.1. *"The actual strength class of concrete of a structure or part of a monolithic and prefabricated monolithic structure in accordance with paragraphs 7.3-7.5 of GOST 16105, depending on the selected control scheme. Note - Presentation in the column “Concrete strength class” of estimated class values or values of the required concrete strength for each section separately (assessment of the strength class for one section) is not acceptable.

UDC 691.32.620.17:006.354 MKS 91.100.10 NEQ

Key words: structural heavy and lightweight concrete, monolithic and prefabricated concrete and reinforced concrete products, structures and structures, mechanical methods for determining compressive strength, elastic rebound, shock impulse, plastic deformation, tearing, rib spalling, tearing with chipping

Editor T.T. Martynova Technical editor 8.N. Prusakova Proofreader M 8. Vuchia Computer layout I.A. Napajkina

Delivered to set 12/29/201S. Signed and printed 02/06/2016. Format 60 "64^. Arial typeface. Uel. oven l. 2.7V. Uch.-iad. l. 2.36. Tira" 60 eke. Zach. 263.

Published and printed by FSUE “STANDARTINFORM”, $12399 Moscow. Grenade Lane.. 4.

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Testing of concrete GOST 22690. Determination of strength by mechanical methods of non-destructive testing. Technique for linking the calibration dependence

Compressive strength of concrete is the main indicator that characterizes concrete.

There are two systems for expressing this indicator:

Compliance of concrete grade (M) with class (B) and compressive strength

Methods for determining the strength of concrete: equipment used

Equipment used

1 area of ​​use

2 Normative references

5 Measuring instruments, equipment and tools

6 Preparation for testing

7 Testing

8 Processing and presentation of results

Appendix A (required) Standard test scheme for the peel-off test

Appendix B (required) Standard rib splitting test scheme

Appendix B (recommended) Calibration dependence for the peel-off method

Appendix D (recommended) Calibration dependence for the rib shearing method with standard test scheme

Appendix D (required) Requirements for instruments for mechanical testing

Appendix G (required) Technique for linking the calibration dependence

Appendix K (recommended) Test results presentation table form

CONCRETE

Determination of strength by mechanical methods of non-destructive testing

1 area of use

Appendix A
(required)
Standard test scheme for the peel-off test

Appendix B
(required)
Standard rib splitting test scheme

Appendix B
(recommended)
Calibration dependence for the peel-off method

Appendix D
(recommended)
Calibration dependence for the rib shearing method
with standard test scheme

Appendix D
(required)
Requirements for instruments for mechanical testing

Appendix G
(required)
Technique for linking the calibration dependence

Appendix K
(recommended)
Test results presentation table form