Determination of strength by mechanical methods of non-destructive testing. Determination of strength by mechanical methods of non-destructive testing E.2 Rejection of test results

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; Ya.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 International Standard applies to heavy and lightweight concrete and specifies methods for determining the compressive strength of structures in terms of rebound, impact impulse, plastic deformation, peeling, rib shearing, and shearing shear.

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

The value of the stress required for local destruction of concrete when a metal disk glued to it is torn off, equal to the tear force divided by the projection area of ​​the concrete torn-off surface onto the disk plane;

1.3. Mechanical methods of non-destructive testing are used to determine the strength of concrete of all types of normalized strength, controlled in accordance with GOST 18105, as well as to determine the strength of concrete during examination and rejection of structures.

1.4. Tests are carried out at a positive temperature of concrete. When examining structures, it is allowed to determine the strength at a negative temperature, but not lower than minus 10 ° C, provided that by the time of freezing the structure has been at a positive temperature for at least one week and the relative humidity of the air is not more than 75%.

1.5. The assessment of the conformity of the values ​​of the actual strength of concrete, obtained using the methods given in this standard to the established requirements, is carried out in accordance with GOST 18105.

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

2.2. A tool for measuring the diameter or depth of indentations (angular scale in accordance with GOST 427, a caliper in accordance with 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 the indentation depth (indicator clock type according to GOST 577, etc.) - with an error of not more than ± 0.01 mm.

It is also allowed to use other anchor devices, the insertion depth of which should not be less than the maximum size of the coarse concrete aggregate of the structure being tested.

2.5. For the tear-off method, steel discs 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 in accordance with GOST 2789, should be used. The adhesive for gluing the disc 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 shearing method of the rib, in the case of using devices in accordance with Appendix 3, it is allowed to use the calibration dependences given in Appendixes 5 and 6, respectively.

STATE STANDARDS OF THE UNION OF THE SSR

CONCRETE HEAVY

METHODS FOR DETERMINING STRENGTH WITHOUT DESTRUCTION BY MECHANICAL DEVICES

Official edition

USSR STATE COMMITTEE ON STANDARDS Moscow

UDC 691.32:620.17:006.354 Group Zh19

STATE STANDARD OF THE UNION OF THE SSR

CONCRETE HEAVY

General requirements for methods for determining the strength without destruction by mechanical action devices

Concrete. General requirements for methods of nondestructive strength determination by the mechanical devices

By the Decree of the State Committee of the Council of Ministers of the USSR for Construction of August 22, 1977 No. 128, the deadline for the introduction was established

from 01.07. 1978

Non-compliance with the standard is punishable by law

1. This standard applies to heavy concrete and establishes general requirements for methods for determining its compressive strength in products and structures with mechanical action devices for rebound, plastic deformation, chipping of the rib of the structure and separation.

Determination of the strength of concrete by the method of separation with shearing - according to GOST 21243-75.

2. The strength of concrete is determined by previously established experimental calibration dependencies between the strength of concrete samples tested in accordance with GOST 10180-78, and indirect characteristics of the strength of concrete (rebound value, imprint size, shearing force of the structure rib, conditional stress at separation) h established by non-destructive tests of those the same samples.

3. To build a calibration dependence, cube samples are used that meet the requirements of GOST 10180-78 and have dimensions, cm:

15X15X15 - for rebound and plastic deformation methods;

20X20X20 - for methods of shearing the rib of the structure and separation.

Official publication Reprint prohibited

Reissue. November 1981

© Standards Publishing, 1982

Op. 10 GOST 22690.0-77

FORM OF THE JOURNAL FOR DETERMINING THE STRENGTH OF CONCRETE IN STRUCTURES

1. Test object_______

2. Test date _

3. Name of the structure (for prefabricated structures - brand, a series of working drawings)_ „_

4. Type of concrete and its design strength _

5. Test method, instrument, test parameters (impact energy, indenter size or disk area, standard material, etc.).

6. Test results (see table)

Page 2 GOST 22690.0-77

The calibration dependence for controlling the strength of concrete of the same brand is established based on the results of testing at least 20 series, each of which consists of three twin samples. The specimens shall have the same composition, duration and curing conditions as the concrete used for the manufacture of the controlled structures. Samples are made within two weeks (at least) in different shifts. To obtain a calibration dependence in a wider range of strength changes, up to 40% of samples should be prepared with a deviation in the cement-water ratio of up to ±0.4. The rejection of abnormal test results of samples is carried out according to mandatory Appendix 1.

4. When controlling the strength of concrete in erected structures, at least 20 cube samples are cut out from different sections, while the test result of one sample is equated to the test result of a series of samples.

It is allowed to establish a calibration dependence by testing cubes with a side of at least 7.07 cm or cores with a diameter of at least 7.14 cm. In this case, the following test procedure should be followed. Non-destructive tests are carried out at the construction site, then a sample is cut out and tested for compression. The boundaries of the non-destructive testing zones and the sample cuts should be at a distance of no more than 100 mm from each other.

5. The calibration dependence should be set at least twice a year, as well as when changing the materials used for the preparation of concrete, and the technology for manufacturing structures.

The method for calculating the equation of the calibration dependence is given in the recommended appendix 2, and an example of its construction is given in reference appendix 3.

6. The estimation of the error of the calibration dependence is carried out according to GOST 17624-78.

7. Experts of specialized research organizations can conduct an approximate assessment of the strength of concrete using a calibration dependence established for concrete that differs from the tested one (in composition, age and hardening conditions), with its refinement based on the results of testing at least three cut samples or three tests by tear-off method with shearing according to GOST 21243-75.

8. Instruments used to determine the strength of concrete must undergo departmental verification at least once every two years, as well as after each repair or replacement of parts. The verification results must be documented.

9. Sites for testing concrete should be selected on the surfaces of the structure that were in contact during manufacture with metal, planed wood or other smooth formwork. EU-

GOST 22690.0-77 Page 3

If the surface of the structure has a finish, it must be removed before testing.

10. Strength should be determined at a positive temperature of concrete.

11. The strength of concrete in the construction site is determined by the average value of the indirect characteristic of the strength of concrete in this area, using the established calibration dependence, taking into account the rejection of abnormal results, produced according to the mandatory Appendix 1.

Test results should be recorded in a log, the form of which is given in the recommended Appendix 4.

12. Control and assessment of the compressive strength of concrete and its uniformity in structures - according to GOST 18105.0-80-GOST 18105.2-80.

Page 4 GOST 22690.0-77

ANNEX 1 Mandatory

RULES FOR REJECTION OF ABNORMAL TEST RESULTS

1. The rejection of abnormal test results (A*) is carried out when the number of results is at least 3 according to the formula (1):

a) for the result of a test on a press of one sample in a series;

b) for a single non-destructive test result in one sample;

c) for a single test result by a non-destructive method in a section of the structure.

2. The test result is considered abnormal and is not taken into account in the calculation,

if the value of T, determined by the formula (1), exceeds the allowable value of Tk, given in table. one. _

where A is the average strength of concrete in a series of samples, the average result of a non-destructive test of one sample or section of the structure;

5 - standard deviation, determined when calculating the calibration dependence according to formula (2).

Table 1

T value and

where d is the coefficient taken according to the table. 2;

Xi max and Xi min - maximum and minimum test results in a series of samples or in a separate sample;

N is the number of series (case a) or the number of individual samples (case b) used in the construction of the calibration dependence.

When evaluating the abnormality of individual test results in sections of structures, the value of S is taken equal to that calculated for individual samples when constructing a calibration dependence.

table 2

The value of the coefficient d

GOST 22690.0-77 Page 5

METHOD OF CALCULATION OF THE EQUATION OF THE CALIBRATION DEPENDENCE "INDIRECT CHARACTERISTIC - STRENGTH"

The equation of dependence "indirect characteristic - strength" is taken:

with a range of fluctuations in the strength of concrete up to 200 kgf / cm 2 - linear:

with a range of fluctuations in the strength of concrete over 200 kgf / cm 2 exponential:

R- b 0 - / b, n. (2)

Coefficients about 0 ; ai b x is calculated by the formulas.

#0 - R-(i\‘ //,* (3)

"='-H?-z-: (4)

2 (Hi-77)(In Ri-UiR)

The average values ​​of strength R and indirect characteristics R, necessary to determine these coefficients, are calculated by the formulas:

*= Chg:< 7 >

In /?-=*"" s - ; (nine)

The values ​​Ri and Hi are, respectively, the values ​​of strengths and indirect characteristics for individual series of three samples (or one sample), and N is the number of series (or individual samples) used to build the calibration dependence.

It is allowed to use the equation of the form (1) (or graphical construction) of the calibration dependence in cases where the error and the efficiency coefficient of the dependence, determined in accordance with GOST 17624-78, are within the permissible limits.

The estimation of the error of the calibration dependence is carried out according to GOST

Page 6 GOST 22690.0-77

APPENDIX $ Reference

EXAMPLES OF CONSTRUCTION OF THE CALIBRATION DEPENDENCE AND SELECTING OF ABNORMAL TEST RESULTS

Building a calibration dependence

The strength of concrete of the design grade M250 is controlled by the rebound method using the KM device. To build the relationship between the rebound value (R) and the compressive strength of the control samples on the press (/?), 29 series of samples were tested (A r * = 29). The average results for each series are given in table. !.

Table 1

Since the concrete strength measurement range 330-169 "=" 170 kgf / cm * is less than 200 kgf / cm *, then, in accordance with the methodology set out in the recommended Appendix 2, the equation of the desired dependence is assumed to be linear: * = Oo + a g I. The coefficients of the equation are calculated by substituting the table data in_formults (3) and (4) of the recommended application 2.

I * 252.9 kgf / cm 3; h "18.24; "36.76; co--417.79.

The calibration dependence "rebound value - strength" is expressed by the equation # "36.76 R-413.

The dependency graph is shown in the drawing.

GOST 22690.0-77 Page one

Dependence "Indirect characteristic (rebound value) - strength"

R, kgf / cm 1

Calculation of standard deviations for strength in a series of 3 samples and for the rebound value in 5 measurements on one sample.

When constructing a calibration dependence (see example I), 29 series of 3 samples were tested. In each sample, the rebound value was determined at 5 points. A selection from the table of test results is given in table. 2.

table 2

Page, 8 GOST 22690.0-77

Continuation

The root mean square deviation of the strength of concrete in a series of samples, determined by the formula (2) and table. 2 will be

S- --- - = 18 kix/cm l .

The same formula is used to calculate the standard deviation of the rebound height on the KM device in samples

4,1+2,9+2,5+3,3+2,1+1,9+...

JTsh--"" 5<е *’

In the second series (see example 2), the strength of the third sample differs significantly from the average in the series. To check the abnormality of this result, according to the formula (1) of mandatory Appendix 1, calculate the value

GOST 22690.0-77 Page nine

which is less than the value determined according to the table T to -1.74 for three samples in the series. Therefore, the result of 252 kgf/cm 2 should not be excluded when determining the strength of concrete in the second series of samples.

In the first sample of the first series (see example 2) the result is 16.0 cases. significantly different from the sample mean. To check the abnormality of this result, according to the formula (1) of mandatory Appendix 1, calculate the value

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 action on concrete (impact, separation, chipping, indentation, separation with chipping, elastic rebound).

3.3 indirect non-erosion methods for determining the strength of concrete: Determination of the strength of concrete according to pre-established calibration dependencies.

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

3.5 calibration dependence: Graphical or analytical dependence between the indirect strength characteristic 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 amount of rebound, impact energy, imprint size or other indication of the device 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 age established by the design documentation and at an age exceeding the design age when examining 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 action or determined indirect characteristic per method:

Elastic rebound;

plastic deformation;

> shock impulse:

Breakaway with chipping:

Rib chipping.

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

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

The method of plastic deformation in relation to the strength of concrete with 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 when the indenter is struck or the indenter is pressed into the concrete surface;

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

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

Method of detachment with shearing on the connection of the strength of concrete with the value of the force of local destruction of concrete when the anchor device is excavated from it;

Rib shearing method on the relationship of concrete strength with the value of the force required to shear a section of concrete on a structure edge.

4.4 In general, 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 tear-off method with shearing during testing in accordance with the standard scheme in Appendix A and the method of rib shearing during 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 dependences established in Appendixes b and D.

Note - Standard test schemes are applicable for a limited range of concrete strength (see Annexes A and B). 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 Table 1 and additional restrictions established by manufacturers of specific measuring instruments. The use of methods outside the concrete strength ranges recommended in Table 1 is allowed with scientific and technical justification based on the results of studies using measuring instruments that have passed metrological certification for an extended concrete strength range.

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 sections of structures that do not have visible damage (peeling of the protective layer, cracks, cavities, etc.).

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

4.10 Tests are carried out at a positive temperature of concrete. It is allowed to conduct 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 the concrete during testing must correspond to the temperature provided for by the operating conditions of the devices.

Calibration dependencies established at a concrete temperature 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 a surface temperature of T to 40 * C (to control the tempering, transfer and stripping 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 (t (T ± 10) *C, and testing of concrete by a direct non-destructive method or testing of samples - after cooling at normal temperature.

5 Measuring instruments, equipment and tools

5.1 Measuring instruments and devices for mechanical testing, designed to determine the strength of concrete, must be certified and verified in the prescribed manner and must comply with the requirements of Appendix D.

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

establishing a calibration dependence "instrument reading - concrete strength" or linking the dependence established in the device in accordance with 6.1.9.

5.3 A tool for measuring the diameter of indentations (caliper according to GOST 166) used for the plastic deformation method should 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 schemes for testing the method of separation with shearing and spalling of the rib provide for the use of anchor devices and grips in accordance with Annexes A and B.

5.5 For the chipping method, anchor devices should be used. the embedment depth of which shall not be less than the maximum size of the coarse concrete aggregate of the structure being tested.

5.6 For the pull-off method, steel discs with a diameter of at least 40 mm should be used. not less than 6 mm thick and not less than 0.1 diameter, with the roughness parameters of the bonded surface not less than Ra = 20 µm according to GOST 2789. The adhesive for gluing the disc must provide adhesion to concrete, at which destruction occurs along concrete.

6 Test preparation

6.1 Procedure for preparing for testing

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

6.1.2 The calibration dependence is established on the basis of the following data:

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

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

The results of testing standard concrete samples by 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, the calibration dependence is established for each type of normalized strength specified in 4.1 for concretes of the same nominal composition.

It is allowed to build one calibration dependence for concrete of the same type with one type of coarse aggregate, with a single production technology, differing in nominal composition and normalized strength value, 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 a calibration dependence on the age of concrete of a 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 normalized concrete strength.

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 the construction of the dependence, and the 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, estimating parameters and determining the conditions for applying a linear calibration dependence is given in Appendix E.

6.1.7 When constructing the calibration dependence of the deviation of individual values ​​of concrete strength R^ from the average value of the concrete strength of sections or samples R f. used to build the calibration dependence should be within:

> from 0.5 to 1.5 average concrete strength Rf at Rf £20 MPa;

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

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

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

6.1.8 Correction of the established dependence for concretes of intermediate and design age should be carried out at least once a month, taking into account additionally obtained test results. The number of samples or areas of additional tests during the adjustment should be at least three. The correction method is given in Appendix E.

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 tested one in composition, age, hardening conditions, moisture content, with reference in accordance with the method according to the assumption Zh.

6.1.10 Without reference to specific conditions according to Appendix G, the calibration dependences established for concrete that differs from the tested one can only be used to obtain approximate strength values. It is not allowed to use approximate 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 by single values ​​of the indirect indicator and concrete strength of the same sections of structures.

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

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

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

Then, sections are selected in the number provided for in 6.2.2, on which the maximum is obtained. minimum and intermediate values ​​of the indirect indicator.

After testing by an indirect non-destructive method, the sections are tested by a 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 sections selected for constructing or linking the calibration dependence are first tested by an indirect non-erosion 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 by a direct non-destructive method. The temperature control of the heated concrete is carried out at the installation depth of the anchor device in the prepared hole or along the chip surface in a non-contact way using a pyrometer according to GOST 28243.

Rejection of the test results used to build the calibration dependence 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 should be replaced by the results of a repeated test in the same area of ​​the structure.

6.3 Construction of a calibration dependence on control samples

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

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

6.3.2 When constructing a calibration dependence based on the results of testing sample cubes, at least 15 series of sample cubes according to GOST 10180 or at least 30 individual sample cubes are used. 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, according to the same technology, with the same hardening mode as the structure to be controlled.

The unit values ​​of the concrete strength of the sample cubes used to build the calibration dependence must correspond to the deviations expected in production, while being within the ranges established in 6.1.7.

6.3.3 The calibration dependence for the methods of elastic rebound, shock impulse, plastic deformation, separation and chipping of the rib is established on the basis of the results of testing the manufactured sample cubes, first by the non-destructive method, and then by the destructive method in accordance with GOST 10180.

When establishing a calibration dependence for the tear-off method with shearing, the main and control samples are made according to 6.3.4. An indirect characteristic is determined on the main samples. control samples are tested in accordance with GOST 10180. The main and control samples must be made from 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 method of separation with chipping (control samples);

200*200*200mm for design rib chipping method:

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

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

The total number of measurements on each sample for the method of elastic rebound, shock impulse, plastic deformation upon impact must be at least 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 indentation plastic deformation method, the number of tests on each face must be at least two, and the distance between the test points must be at least two indent diameters.

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

When establishing the calibration dependence for the method of separation with shearing, 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, plastic deformation upon impact, the specimens shall be clamped in the press with a force of not less than (30 ± 5) kN and not more than 10% of the expected value of the breaking load.

6.3.7 The specimens tested by the pull-off method are mounted on the press as follows. so that the surfaces on which the pull-out was carried out do not adjoin to the base plates of the press. The test results according to GOST 10180 are increased 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 be indicated in the design documentation for structures or be set taking into account:

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

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

Placement of grips and pouring order:

Structural reinforcement.

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

7.1.2 Tests are carried out on a construction site with an area of ​​100 to 900 cm2.

7.1.3 The total number of measurements in each area, the distance between the measurement points in the area and from the edge of the structure, the thickness of the structures in the measurement area should not be less than the values ​​given in Table 2, depending on the test method.

Table 2 - Requirements for test sites

7.1.4 The deviation of individual measurement results in each section from the arithmetic mean of the measurement results for this section should not exceed 10%. The results of measurements that do not meet the specified condition are not taken into account when calculating the arithmetic mean of the indirect indicator for this area. The total number of measurements in each section when calculating the arithmetic mean must comply with the requirements of Table 2.

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 dependence established in accordance with the requirements of Section 6. provided that the calculated value of the indirect indicator is within the established (or tied) dependence (between the smallest and largest values strength).

7.1.6 The surface roughness of the structure concrete section when tested by the methods of rebound, impact impulse, plastic deformation should correspond to the surface roughness of the structure sections (or cubes) tested when establishing the calibration dependence. 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 taken after the application of the initial load, there are no requirements for the roughness of the concrete surface of the structure.

7.2 Rebound method

7.2.1 Tests are carried out in the following sequence:

The position of the device when testing the structure relative to the horizontal is recommended to be taken the same. as well as when establishing the calibration dependence. In a different position of the device, it is necessary to make a correction for the indicators in accordance with the instruction manual 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 instructions for use of the device;

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

Fix the values ​​of the indirect characteristic in accordance with the instruction manual for the device;

Calculate the average value of the indirect characteristic on the construction site.

7.4 Shock pulse method

7.4.1 Tests are carried out in the following sequence:

The device is placed like this. so that the force is applied perpendicular to the surface under test * in accordance with the instructions for use of the device:

The position of the device when testing the structure relative to the horizontal is recommended to be taken the same as when testing when establishing the calibration dependence. In a different position of the device, it is necessary to make a correction for the readings in accordance with the instruction manual for the device;

The value of the indirect characteristic is fixed in accordance with the instruction manual for the device;

Calculate the average value of the indirect characteristic on the construction site.

7.5 Pull-off method

7.5.1 When testing by the pull-off method, the sections should be located in the zone of the 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 disk is glued, a surface layer of concrete with a depth of 0.5-1 mm is removed and the surface is cleaned of dust;

The disk is glued to the concrete by pressing the disk and removing excess adhesive outside the disk;

The ribs are connected to the disk;

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

Record the reading of the force meter of the device;

Measure the projection area of ​​the separation surface on the plane of the disk with an error of iO.Scm 2 ;

The value of the conditional stress in the concrete at separation is determined as the slope of the maximum separation force to the area of ​​the projection of the separation surface.

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

7.6 Pull-off method with shear

7.6.1 When testing by the pull-off method with shearing, the sections should be located in the zone of the 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 device operating instructions, depending on the type of anchor device;

An anchor device is fixed in the hole to the depth provided for in the instruction manual for the device, depending on the type of anchor device;

The device is connected with a sunker device;

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

The reading of the force meter of the P 0 device and the amount of slippage of the anchor LP (the difference between the actual depth of the pull-out and the depth of the anchor device) are recorded with an accuracy of not less than 0.1 mm.

7.6.3 The measured value of the pull-out 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 - anchor slippage, mm.

7.6.4 If the largest and smallest dimensions of the torn out part of the concrete from the anchor device to the boundaries 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 the anchor device by more than 5% (DL > 0.05ft, y > 1.1), then the test results can only be taken into account for an approximate assessment of the strength of concrete.

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

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

7.7 Rib chipping method

7.7.1 When testing by the rib shearing method, there should be no cracks, concrete rims, sags or shells with a height (depth) of more than 5 mm in the test area. The sections should be located in the zone of the least stresses 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 fastened to the structure. apply a load at a speed of no more than (1 ± 0.3) kN/s;

Record the reading of the instrument's force meter;

Measure the actual depth of chipping;

Determine the average value of the chipping force.

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

8 Processing and presentation of results

8.1 The test results are presented in a table indicating:

Type of construction;

Design class of concrete;

Age of concrete;

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

The average strength of the concrete structure;

Zones of the structure or its parts subject to the requirements of 7.1.1.

The form of the test results presentation table is given in Annex K.

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

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

8.3 The results of determining the strength of concrete by mechanical methods of non-destructive testing are drawn up in a conclusion (protocol), in which the following data are given:

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

On the methods used to control the strength of concrete;

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

On the accepted calibration dependences (dependence equation, dependence parameters, compliance with the conditions for applying the calibration dependence);

Used to build a calibration dependence or its binding (date and results of tests by non-destructive indirect and direct or destructive methods, correction factors);

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

Test results;

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

Standard Shear-Pull Test Design

A.1 The standard shear-pull test scheme provides for tests subject to the requirements of A.2 to 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 anchor devices.

A.3 The supports of the loading device must evenly adjoin 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 - a device with a loading device and a measuring force; 2 - support of the loading device: 3 - grip of the loading device: 4 - transition elements, rods, S - anchor device. 6 - torn-out concrete (tear cone): 7 - tested structure

Figure A.1 — Schematic of the pull-out and shear test

A.4 The standard shearing test scheme provides for the use of three types of anchor devices (see Figure A.2). Anchor device type I is installed in the structure during concreting. Anchor devices of types II and ill are installed in holes previously prepared in the structure.

1 - working rod: 2 - working rod with frames of a different cone: 3 - segmented corrugated sheets: 4 - support rod: 5 - working rod with a ripe expanding cone: b - leveling washer

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

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

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

A.b Anchor designs of types II and III must provide preliminary (before applying the load) compression of the hole walls at the working depth of embedding l and slip control after the test.

Standard Rib Shearing Test Arrangement

B.1 The standard scheme of testing by the rib shearing method provides for testing subject to the requirements of B.2-B.4.

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

The maximum fraction of coarse concrete aggregate is not more than 40 mm:

Tests of heavy concrete with compressive strength from 10 to 70 MPa on crushed granite and limestone. B.3 For testing, a device is used, consisting of a power exciter with a force-measuring unit

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

1 - device with a loading device and a sipo-meter. 2 - support frame: 3 - chipped concrete: 4 - tested

construction^ - grip with bracket

Figure B.1 - Schematic of the rib shear test

B.4 In case of local shearing of the rib, the following parameters should be provided:

Depth of chipping 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 pull-off method with shearing in the standard test scheme

When carrying out tests by the method of separation with squealing 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 according to the gravity dependence according to the formula

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

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

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

P is the pull-out 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 factor m2 are taken from Table B.1.

Table 8.1

The coefficients m 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 performing the test by chipping the ribs according to the standard scheme in accordance with Appendix B, the cubic compressive strength of concrete on granite and lime rubble R. Mla. it is allowed to calculate according to the calibration dependence according to the formula

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

where m 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 - aggregate size from 30 to 40 mm:

P - chipping force. kN.

Annex D (mandatory)

Requirements for instruments for mechanical testing

Table E.1

Excerpts from GOST 22690 DETERMINATION OF STRENGTH BY MECHANICAL METHODS OF NON-DESTRUCTIVE TESTING

TESTING

4.1. Tests are carried out on a construction site with an area of ​​100 to 600 cm 2 .

4.2. The strength of concrete in the controlled section of the structure is determined by the calibration dependence established in accordance with the requirements of Sec. 3, provided that the measured values ​​of the indirect indicator are within the limits between the smallest and the largest values ​​of the indirect indicator in the samples tested when constructing the calibration dependence.

4.3. The number and location of controlled sections during testing of structures must comply with the requirements of GOST 18105-86 or indicated in the standards and (or) specifications for prefabricated or in working drawings for monolithic structures and (or) in technological maps for control. When determining the strength of the examined structures, the number and location of sections should be taken according to the survey program.

4.4. The number of tests on one site, the distance between the test sites on the site and from the edge of the structure, the thickness of the structure on the test site should not be less than the values ​​\u200b\u200bgiven in Table. 3.

Table 3mm

4.5. The surface roughness of the concrete section of the structure when tested by the methods of rebound, shock impulse, plastic deformation should correspond to the surface roughness of the cubes tested when establishing the calibration dependence. In necessary cases, cleaning of the surface of the structure is allowed. When testing by the method of plastic deformation during indentation, if the zero reading is taken after the application of the initial load, no requirements are imposed on the surface roughness of the concrete structures.

4.6. Rebound method

4.6.1. When testing by the method of elastic rebound, the distance from the test points to the reinforcement must be at least 50 mm.

4.6.2. The test is 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 instruction manual for the device; the position of the device when testing a structure relative to the horizontal is recommended to be taken the same as when testing samples to establish a calibration dependence; in a different position, it is necessary to make a correction for the readings in accordance with the instruction manual for the device; fix the value of the indirect characteristic in accordance with the instruction manual for the device; calculate the average value of the indirect characteristic on the construction site.

4.7. Plastic deformation method.

4.7.1. When testing by the plastic deformation method, the distance from the test points to the reinforcement must be at least 50 mm.

4.7.2. The test is 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 instruction manual for the device; with a spherical indenter, the test is allowed to be carried out to facilitate measurements of the diameters of prints through sheets of carbon and white paper (in this case, samples to establish the calibration dependence are tested using the same paper); fix the values ​​of the indirect characteristics in accordance with the instruction manual for the device; calculate the average value of the indirect characteristic on the construction site. 4.8. shock pulse method

4.8.1. When testing by the shock impulse method, the distance of the test points to the reinforcement must be at least 50 mm.

4.8.2. Tests are carried out in the following sequence: the device is positioned so that the force is applied perpendicular to the test surface in accordance with the instructions for use of the device; the position of the device when testing a structure relative to the horizontal is recommended to be taken the same as when testing samples to establish a calibration dependence; in a different position, it is necessary to make a correction for the readings in accordance with the instruction manual for the device; fix the value of the indirect characteristic in accordance with the instruction manual for the device; calculate the average value of the indirect characteristic on the construction site.

4.9. Pull-off method

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

4.9.2. The test is carried out in the following sequence: at the place where the disk is glued, the surface layer of concrete is removed with a depth of 0.5 - 1 mm and the surface is cleaned of dust; the disc is glued to the concrete so that the adhesive layer on the surface of the concrete does not extend beyond the disc; the device is connected to the disk; the load is gradually increased with a speed of (1 P 0.3) kN / s; fix the reading of the force meter of the device; measure the projection area of ​​the separation surface on the plane of the disc with an error of P0.5 cm 2 ; determine the value of the conditional stress in concrete at separation. The test results are not taken into account if reinforcement was found during the detachment of concrete or the projection area of ​​the detachment surface was less than 80% of the disk area.

4.10. Breakaway method with shearing 4.10.1. In the shear-pull test, the sections shall be located in the zone of least stress caused by the service load or compression force of the prestressed reinforcement.

4.10.2. The tests are carried out in the following sequence: if the anchor device was not installed before concreting, then a hole is drilled or punched in the concrete, the size of which is selected in accordance with the instruction manual for the device, depending on the type of anchor device; an anchor device is fixed in the hole to the depth provided for in the operating instructions for the device, depending on the type of anchor device; the device is connected to the anchor device; the load is increased at a rate of 1.5 - 3.0 kN / s; fix the reading of the force meter of the device and the pull-out depth with an accuracy of at least 1 mm. If the largest and smallest dimensions of the torn-out part of the concrete from the anchor device to the boundaries 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 insertion depth of the anchor devices by more than 5%, then the test results can only be taken into account for an approximate assessment strength of concrete.

4.11. Rib chipping method

4.11.1. When testing by the rib shearing method, there should be no cracks, concrete surroundings, sags or shells with a height (depth) of more than 5 mm in the test area. The sections should be located in the zone of the least stresses caused by the operational load or the compression force of the prestressed reinforcement.

4.11.2. The test is carried out in the following sequence: the device is fixed to the structure, a load is applied at a speed of not more than (1 P 0.3) kN / s; fix the reading of the force meter of the device; measure the actual depth of chipping; determine the average value of the chipping force. The test results are not taken into account if the reinforcement was exposed during concrete shearing and the actual shearing depth differed from the specified one (see Appendix 3) by more than 2 mm.