Determination of strength by mechanical methods of non-destructive testing. Determination of strength by mechanical methods of non-destructive testing Concrete testing GOST 22690

1 area of \u200b\u200buse

2 Normative references

3 Terms and definitions

4 General

5 Measuring instruments, apparatus and instrument

6 Test preparation

7 Testing

8 Processing and presentation of results

Standard Shear Pull Test Scheme

Standard rib shear test setup

Calibration dependence for the shear-off method with a standard test setup

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

Requirements for instruments for mechanical testing

Method for establishing, correcting and evaluating the parameters of calibration dependences

Calibration dependence binding method

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

Test results presentation table

The compressive strength of concrete is the main indicator that characterizes concrete.

There are two systems for expressing this indicator:

Conformity of concrete grade (M) to class (B) and compressive strength

Methods for determining the strength of concrete: equipment used

Equipment used

Table 2 - Requirements for test sites

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

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

TESTING

4.1. The tests are carried out on a construction site with an area of \u200b\u200b100 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 \u200b\u200bof the indirect indicator are in the range between the smallest and largest values \u200b\u200bof the indirect indicator in the samples tested in the construction of the calibration dependence.

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

4.4. The number of tests in one section, the distance between the test sites at the site and from the edge of the structure, the thickness of the structure at the test site must be not less than the values \u200b\u200bgiven in table. 3.

Table 3 mm

4.5. The roughness of the surface of the concrete section of the structure when tested by the methods of rebound, shock impulse, plastic deformation must correspond to the roughness of the surface of the cubes tested when establishing the calibration dependence. If necessary, cleaning the surface of the structure is allowed. When testing by plastic deformation at indentation, if the zero reading is removed after applying an initial load, there are no requirements for the roughness of the concrete surface of the structures.

4.6. Rebound Method

4.6.1. When testing by the method of elastic rebound, the distance from the test sites to the reinforcement should 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 test surface 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 the same as when testing samples to establish a calibration dependence; in a different position, it is necessary to correct for the readings in accordance with the instructions for use of 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 at the construction site.

4.7. Plastic deformation method.

4.7.1. When testing by plastic deformation, the distance from the test sites 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 test surface in accordance with the instructions for use of 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, the samples for establishing the calibration dependence are tested using the same paper); fix the values \u200b\u200bof the indirect characteristic in accordance with the instruction manual for the device; calculate the average value of the indirect characteristic at the construction site. 4.8. Shock pulse method

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

4.8.2. The 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 the structure relative to the horizontal is recommended to be the same as when testing samples to establish a calibration dependence; in a different position, it is necessary to correct for the readings in accordance with the instructions for use of 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 at the construction site.

4.9. Tear-off method

4.9.1. In the pull-off test, the sections shall be located in the zone of lowest stresses caused by the service load or the compression force of the prestressed reinforcement.

4.9.2. The test is carried out in the following sequence: at the place of gluing the disc, remove the surface layer of concrete 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 concrete surface does not go beyond the disc; the device is connected to the disk; the load is gradually increased at a rate of (1 P 0.3) kN / s; fix the reading of the force meter of the device; measure the projection area of \u200b\u200bthe separation surface on the plane of the disk 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 concrete tearing or the projected area of \u200b\u200bthe tearing surface was less than 80% of the disc area.

4.10. Chipping-off method 4.10.1. In the shear pull test, the sections shall be located in the zone of lowest stresses caused by the service load or the 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 instructions for use of the device, depending on the type of anchor device; an anchor device is fixed in the borehole to a depth specified in the instruction manual for the device, depending on the type of anchor device; the device is connected to the 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 and the depth of the cutout 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 tear-out depth differs from the embedment depth of the anchor devices by more than 5%, then the test results may be taken into account only for a rough estimate concrete strength.

4.11. Rib cleaving method

4.11.1. When testing by spalling ribs, there should be no cracks, concrete gaps, sagging or cavities with a height (depth) of more than 5 mm in the test area. The sections should be located in the zone of least stress 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, the load is applied at a speed not exceeding (1 P 0.3) kN / s; fix the reading of the force meter of the device; measure the actual shearing depth; determine the average value of the shear force. The test results are not taken into account if the reinforcement was exposed during spalling of concrete and the actual spalling depth differed from the specified one (see Appendix 3) by more than 2 mm.

Put into effect by order of the Federal Agency for Technical Regulation and Metrology of September 25, 2015 N 1378-st

Interstate standard GOST 22690-2015

"CONCRETES. DETERMINATION OF STRENGTH BY MECHANICAL METHODS OF NON-DESTRUCTIVE CONTROL"

Concretes. Determination of strength by mechanical methods of nondestructive testing

Instead of GOST 22690-88

Foreword

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, renewal and cancellation "

Information about the standard

1 Developed by the Structural subdivision of JSC "Research Center" Construction "Research, Design and Engineering Institute of Concrete and Reinforced Concrete named after A.A.Gvozdev (NIIZhB)

2 Introduced by the Technical Committee for Standardization TK 465 "Construction"

3 Adopted by the Interstate Council for Standardization, Metrology and Certification (minutes of June 18, 2015 N 47)

Short name of the country according to MK (ISO 3166) 004-97	Country code according to MK (ISO 3166) 004-97	Abbreviated name of the national standardization body
		Ministry of Economy of the Republic of Armenia
Belarus		Gosstandart of the Republic of Belarus
Kazakhstan		Gosstandart of the Republic of Kazakhstan
Kyrgyzstan		Kyrgyzstandard
		Moldova-Standard
		Rosstandart
Tajikistan		Tajikstandart

4 By order of the Federal Agency for Technical Regulation and Metrology dated September 25, 2015 N 1378-st, the interstate standard GOST 22690-2015 was put into effect as a national standard of the Russian Federation from April 1, 2016.

5 This standard takes into account the main regulatory provisions regarding the requirements for mechanical methods for 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. Part 3: Determination of pull-out force.

Compliance - Non-Equivalent (NEQ)

6 Replaces GOST 22690-88

This standard applies to structural heavy, fine-grained, light and stress concretes of monolithic, precast and precast-monolithic 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, shock impulse , plastic deformation, pull-off, rib chipping and shear-off.

This standard uses normative references to the following interstate standards:

GOST 166-89 (ISO 3599-76) Calipers. Technical conditions

GOST 577-68 Dial indicators with a graduation of 0.01 mm. Technical conditions

GOST 2789-73 Surface roughness. Parameters and characteristics

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

GOST 18105-2010 Concrete. Rules for control and assessment of strength

GOST 28243-96 Pyrometers. General technical requirements

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

GOST 31914-2012 High-strength heavy and fine-grained concrete for monolithic structures. Quality control and assessment rules

Note - When using this standard, it is advisable to check the validity of reference standards in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet or according to the annual information index "National Standards", which was published as of January 1 of the current year, and by releases of the monthly information index "National Standards" for the current year. If the reference standard is replaced (changed), then when using this standard, the replacing (modified) standard should be followed. If the reference standard is canceled without replacement, then the provision in which the reference to it is given applies to the extent that this reference is not affected.

In this standard, the terms according to GOST 18105 are used, as well as the following terms with the corresponding definitions;

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

3.3 indirect non-destructive 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 for standard test schemes (pull-off with shearing and shearing of ribs) and allowing the use of known calibration dependencies without reference and correction.

3.5 calibration dependence: Graphic or analytical dependence between the 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 magnitude of the applied force during local destruction of concrete, the magnitude of the rebound, the impact energy, the size of the indentation or other indication of the device when measuring the strength of concrete by non-destructive mechanical methods.

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 age when inspecting structures.

4.2 Non-destructive mechanical methods for determining the strength of concrete, established by this standard, are subdivided according to the type of mechanical effect or determined indirect characteristics by the method:

Elastic rebound;

Plastic deformation;

Shock impulse;

Chipping off;

Rib chipping.

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

Method of elastic rebound based on the relationship 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 indentation on the concrete of the structure (diameter, depth, etc.) or the ratio of the diameter of the indentation on concrete and a standard metal sample when the indenter is hit or the indenter is pressed into the concrete surface;

Shock impulse method based on the relationship between the strength of concrete and the impact energy and its changes at the moment the striker hits the concrete surface;

The method of separation on the bond of the stress required for local destruction of concrete when tearing off a metal disk glued to it, equal to the separation force divided by the area of \u200b\u200bthe projection of the surface of concrete separation on the plane of the disk;

The method of separation with chipping on the connection between the strength of concrete and the value of the force of local destruction of concrete when the anchor device is pulled out of it;

The method of chipping a rib on the connection between the strength of concrete and the value of the force required to chip a section of concrete on the rib of the structure.

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

4.5 The method of shearing and spalling when tested in accordance with the standard scheme of annex A and the method of chipping a rib when testing in accordance with the standard scheme of annex 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 G.

NOTE Standard test schemes are applicable over a limited range of concrete strength (see annexes A and B). For cases not related to standard test schemes, calibration dependences 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 ranges of concrete strength recommended in Table 1 is allowed with a 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 The determination of the strength of heavy concrete of design classes B60 and above or with an average compressive strength of concrete R m ≥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 (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 the calibration dependence by more than 25%. Exceptions are strength control and construction of a calibration dependence for concrete that is more than two months old. In this case, the difference in the age of individual structures (sections, samples) is not regulated.

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

Calibration dependences established at a concrete temperature below 0 ° С are not allowed to be used at positive temperatures.

4.11 If it is necessary to test concrete of structures after heat treatment at a surface temperature T≥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 \u003d (T ± 10) ° С, and concrete testing by direct non-destructive method or specimen testing - after cooling down at normal temperature.

5.1 Measuring instruments and instruments 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 Instrument readings, graded in units of concrete strength, should be considered as an indirect indicator of concrete strength. The indicated devices should be used only after establishing the calibration dependence "device reading - concrete strength" or binding the dependence set in the device in accordance with 6.1.9.

5.3 A tool for measuring the diameter of indentations (caliper in accordance with GOST 166), used for the method of plastic deformation, must ensure measurement with an error of not more than 0.1 mm, a tool for measuring the depth of an indentation (dial indicator in accordance with GOST 577, etc.) - with an error no more than 0.01 mm.

5.4 Standard test procedures for shear prying and rib chipping involve the use of anchoring devices and grips in accordance with Appendices A and B.

5.5 For the shear-off method, anchor devices should be used, the embedment depth of which should not be less than the maximum size of the coarse concrete aggregate of the structure under test.

5.6 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 the parameters of the bonded surface roughness of at least Ra \u003d 20 μm in accordance with GOST 2789 should be used. The adhesive for gluing the disc must ensure adhesion strength with concrete, in which destruction occurs along the concrete.

6.1 Procedure for preparation for testing

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

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

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

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;

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 rated strength specified in 4.1 for concretes of the same nominal composition.

It is allowed to build one calibration dependence for concretes of the same type with one type of coarse aggregate, with a single production technology, differing in the nominal composition and the value of the rated strength, subject to the requirements of 6.1.

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 dependences given in Appendices C and D for all types of normalized concrete strength.

6.1.6 The calibration dependence should 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 the construction of the dependence, and the correlation coefficient (index) not less than 0.7

It is recommended to use a linear relationship of the form R \u003d a + b K (where R is the strength of concrete, K is an indirect indicator). The procedure for establishing, evaluating the parameters and determining the conditions for using a linear calibration dependence is given in Appendix E.

6.1.7 When constructing a calibration dependence, the deviation of the unit values \u200b\u200bof concrete strength R i f from the average value of concrete strength of the sections or samples R̅ f used to construct the calibration dependence should be within:

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

From 0, 6 to 1, 4 average value of concrete strength R̅ f at 20 MPa< R̅ ф ≤ 50 МПа;

From 0, 7 to 1, 3 average value of concrete strength R̅ f at 50 MPa< R̅ ф ≤ 80 МПа;

From 0, 8 to 1, 2 average values \u200b\u200bof concrete strength R̅ f at R̅ f\u003e 80 MPa.

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

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

6.1.10 Without reference to specific conditions according to Appendix G, the calibration dependences established for concrete that differs from the tested one may be used only to obtain approximate strength values. It is not allowed to use approximate strength values \u200b\u200bwithout reference to specific conditions to assess the strength class of concrete.

6.2 Construction of a calibration dependence based on the results of testing the strength of concrete in structures

6.2.1 When constructing a calibration dependence according to the results of testing the strength of concrete in structures, the dependence is established according to the unit values \u200b\u200bof the indirect indicator and the strength of concrete of the same sections of structures.

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

6.2.2 The minimum number of single values \u200b\u200bfor 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 concrete strength tests in structures that are not subject to testing, or in their zones, measurements are first carried out by an indirect non-destructive method in accordance with the requirements of Section 7.

Then select the plots in the quantity provided for in 6.2.2, on which the maximum, minimum and intermediate values \u200b\u200bof the indirect indicator are obtained.

After testing by the indirect non-destructive method, the areas are tested by the direct non-destructive method or samples are taken for testing in accordance with GOST 28570.

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

The rejection of the test results used to construct the calibration dependence at negative temperatures 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 \u200b\u200bthe structure.

6.3 Construction of calibration dependence on control samples

6.3.1 When constructing a calibration dependence for control samples, the dependence is established according to the unit values \u200b\u200bof the indirect indicator and the strength of concrete of standard sample cubes.

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

6.3.2 When constructing a calibration dependence based on the test results of cube samples, at least 15 series of cube samples according to GOST 10180 or at least 30 separate cube samples 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, using the same technology, with the same hardening mode as the structure to be controlled.

The unit values \u200b\u200bof the concrete strength of the cube samples used to construct the calibration dependence must correspond to the deviations expected in production, while being within the ranges specified in 6.1.7.

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

When establishing the calibration dependence for the method of separation with spalling, make the main and control samples according to 6.3.4. The indirect characteristic is determined on the main samples, the control samples are tested in accordance with 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:

100 x 100 x 100 mm for rebound, shock impulse, plastic deformation methods, as well as for the shear-off method (control samples);

200 x 200 x 200 mm for the method of chipping the rib of the structure;

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

6.3.5 To determine the 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 specimens.

The total number of measurements on each sample for the method of elastic rebound, shock pulse, plastic deformation upon impact must be at least the specified number of tests in the area according to Table 2, and the distance between the places of impacts must be at least 30 mm (15 mm for the shock pulse method). For the method of plastic deformation by indentation, the number of tests on each face should be at least two, and the distance between test sites should be at least two diameters of indentations.

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

When establishing the calibration dependence for the shear-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, plastic deformation upon impact, the samples shall be clamped in a press with a force of at least (30 ± 5) kN and not more than 10% of the expected value of the breaking load.

6.3.7 Samples tested by the pull-off method are installed on the press so that the surfaces on which the pull-out was carried out do not adjoin the press base plates. The test results according to GOST 10180 increase by 5%.

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 the structure or be installed 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 concreting order;

Reinforcement of structures.

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

7.1.2 The tests shall be carried out on a section of the structure with an area of \u200b\u200b100 to 900 cm 2.

7.1.3 The total number of measurements in each section, the distance between the measurement points in the section and from the edge of the structure, the thickness of the structures in the measurement section should be not less than the values \u200b\u200bgiven in Table 2, depending on the test method.

Method name	Total number of measurements on the site	The minimum distance between the places of measurements on the site, mm	The minimum distance from the edge of the structure to the place of measurement, mm	Minimum structure thickness, mm
Elastic rebound
Impact impulse
Plastic deformation
Chipping a rib
		2 disc diameters
Tear-off with spalling at working anchor embedment depth h: ≥ 40 mm

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%. Measurement results that do not satisfy the specified condition are not taken into account when calculating the arithmetic mean of the indirect indicator for a given area. The total number of measurements in each section when calculating the arithmetic mean must meet 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) relationship (between the smallest and largest values strength).

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

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

7.2 Rebound Method

7.2.1 The 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 when establishing the calibration dependence. In a different position of the device, it is necessary to correct for the indicators in accordance with the instructions for use of the device;

7.3 Method of plastic deformation

7.3.1 The 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;

When using a spherical indenter to facilitate measurements of indentation diameters, the test may 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 \u200b\u200bof the indirect characteristic are recorded in accordance with the instructions for use of the device;

Calculate the average value of the indirect characteristic at the site of the structure.

7.4 Shock pulse method

7.4.1 The 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;

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

The value of the indirect characteristic is recorded in accordance with the instructions for use of the device;

Calculate the average value of the indirect characteristic at the site of the structure.

7.5 Pull-off method

7.5.1 In the pull-off test, the sections shall be located in the zone of lowest stresses caused by the service load or the compression force of the prestressed reinforcement.

7.5.2 The test is carried out in the following sequence:

At the place of gluing the disc, remove the surface layer of concrete with a depth of 0.5 - 1 mm and clean the surface of dust;

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

The device is connected to a disk;

The load is gradually increased at a rate of (1 ± 0, 3) kN / s;

Measure the area of \u200b\u200bthe projection of the separation surface on the plane of the disk with an error of ± 0.5 cm 2;

The value of the conditional stress in concrete during separation is determined as the ratio of the maximum separation force to the projection area of \u200b\u200bthe separation surface.

7.5.3 The test results are not taken into account if, when concrete was torn off, reinforcement was exposed or the projected area of \u200b\u200bthe tearing surface was less than 80% of the disc area.

7.6 Pull-off method with chipping

7.6.1 When tested by the shear pull method, the sections shall be located in the zone of lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.

7.6.2 The 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;

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

The device is connected to an anchor device;

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

The reading of the force meter of the device P 0 and the value of the anchor slip Δh (the difference between the actual tear-out depth and the embedment depth of the anchor device) are recorded with an accuracy of at least 0.1 mm.

7.6.3 The measured value of the pull-out force P 0 is multiplied by the correction factor γ, determined by the formula

where h is the working depth of the anchoring device, mm;

Δh - anchor slip value, mm.

7.6.4 If the largest and smallest dimensions of the torn out part of concrete from the anchor device to the destruction boundaries along the surface of the structure differ by more than two times, and also if the tear-out depth differs from the embedment depth of the anchor device by more than 5% (Δh\u003e 0.05h , γ\u003e 1, 1), then the test results can be taken into account only for an approximate assessment of the strength of concrete.

Note - Approximate values \u200b\u200bof concrete strength are not allowed to be used for assessing the concrete strength class and building calibration dependencies.

7.6.5 The test results are not taken into account if the tear-out depth differs from the embedment depth of the anchor device by more than 10% (Δh\u003e 0, 1h) or reinforcement was exposed at a distance from the anchor device less than the embedment depth.

7.7 Rib chipping method

7.7.1 When testing the rib shear method, there should be no cracks, concrete gaps, sagging or cavities more than 5 mm in height (depth) in the test area. 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 on the structure, the load is applied at a rate of no more than (1 ± 0, 3) kN / s;

The readings of the force meter of the device are recorded;

Measure the actual shear depth;

Determine the average shear force.

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

8.1 The test results are presented in a table, which indicates:

Type of construction;

Concrete design class;

Concrete age;

Strength of concrete of each inspected area according to 7.1.5;

Average concrete strength of the structure;

Zones of a structure or its part subject to the requirements of 7.1.1.

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

8.2 Processing and assessment of compliance with the established requirements of the actual concrete strength values \u200b\u200bobtained using the methods given in this standard is carried out in accordance with GOST 18105.

Note - The statistical assessment of the class of concrete based on 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 constructed 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 scheme "G" GOST 18105.

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

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

On the methods used to control the strength of concrete;

On the types of devices with serial numbers, information on instrument checks;

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

Used to construct 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 data obtained.

Appendix A
(required)

A.1 The standard shear peel test scheme provides for tests to be carried out in accordance with A.2 to A.6.

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

Tests of heavy concrete with compressive strength from 5 to 100 MPa;

Tests of lightweight concrete with compressive strength from 5 to 40 MPa;

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

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

1 - device with a loading device and a force meter; 2 - support of the loading device; 3 - capture of the loading device; 4 - transition elements, rods; 5 - anchor device; 6 - pulled out concrete (tear-off cone); 7 - tested structure

"Figure A.1 - Schematic of a peel-off shear test"

A.4 Three types of anchor devices (see Figure A.2) are provided by the standard shear-pull test setup. The Type I anchor device is installed in the structure during concreting. Anchoring devices of types II and III are installed in holes previously prepared in the structure.

1 - working rod: 2 - working rod with expanding cone; 3 - segmented corrugated cheeks; 4 - support rod; 5 - working rod with a hollow expanding cone; 6 - leveling washer

"Figure A.2 - Types of anchor devices for a standard test setup"

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

Anchor device type	Embedment depth of anchor devices, mm	Permissible range for the anchor device for measuring the compressive strength of concrete, MPa
Anchor device type	working h	heavy

А.6 Designs of anchors of types II and III should provide preliminary (before loading) compression of the hole walls at the working depth h and control of slippage after testing.

Appendix B
(required)

B.1 The standard test scheme by the shearing of ribs method provides for testing in compliance with the requirements of B.2 - B.4.

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

Maximum fraction of coarse concrete aggregate no more than 40 mm;

Tests 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 power exciter with a force measuring unit and a gripper with a bracket for local chipping of the rib of the structure. The test scheme is shown in Figure B.1.

1 - the device is a loading device and a force measuring device; 2 - support frame; 3 - chipped concrete; 4 - tested structure. 5 - grip with a bracket

"Figure B.1 - Schematic of the rib shear test"

B.4 During local spalling of the rib, the following parameters should be provided:

Chipping depth a \u003d (20 ± 2) mm;

Cleaving width b \u003d (30 ± 0.5) mm;

The angle between the direction of the load and the normal to the loaded surface of the structure β \u003d (18 ± 1) °.

When carrying out tests by the method of separation with spalling according to the standard scheme according to Appendix A, the cubic compressive strength of concrete R, MPa, it is allowed to calculate using the calibration dependence according to the formula

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

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

P - 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 \u200b\u200bof the proportionality coefficient m 2 are taken according to Table B.1.

Table B.1

Anchor device type	Range of measured concrete compressive strength, MPa	Anchor device diameter d, mm	Embedment depth of anchor device, mm	The value of the coefficient m 2 for concrete
Anchor device type	Range of measured concrete compressive strength, MPa	Anchor device diameter d, mm	Embedment depth of anchor device, mm	heavy

Coefficients m 2 when testing heavy concrete with an average strength above 70 MPa should be taken in accordance with GOST 31914.

When performing the test by spalling ribs according to the standard scheme according to Appendix B, the cubic compressive strength of concrete on granite and limestone crushed stone R, MPa, is allowed to be calculated using the calibration dependence according to the formula

R \u003d 0.058m (30P + P 2),

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

1, 0 - when the aggregate size is less than 20 mm;

1, 05 - with aggregate size from 20 to 30 mm;

1, 1 - with aggregate size from 30 to 40 mm;

P - shearing force, kN.

Appendix D
(required)

Table E.1

Name of device characteristics	Characteristics of instruments for the method
Name of device characteristics	elastic rebound	shock pulse	plastic deformation	chipping ribs	shearing off
Striker, striker or indenter hardness HRCэ, not less
Roughness of the contact part of the striker or indenter, μm, no more
Diameter of striker or indenter, mm, not less
The thickness of the edges of the disk indenter, mm, not less
Tapered indenter angle
Indentation diameter,% of indenter diameter
Perpendicularity tolerance when a load is applied at a height of 100 mm, mm
Impact energy, J, not less
Load increase rate, kN / s
Load measurement error,%, no more
* When pressing the indenter into the concrete surface.

E.1 Equation of calibration dependence

The equation of dependence "indirect characteristic - strength" is taken linear by the formula

E.2 Rejection of test results

After constructing the calibration dependence according to the formula (E.1), it is corrected by rejecting single test results that do not satisfy the condition:

where R i n - the strength of concrete in the i-th section, determined by the considered calibration dependence;

S - residual standard deviation, calculated by the formula

here R i f, N - see the explication to the formula (E.3).

After rejection, the calibration dependence is established again according to formulas (E.1) - (E.5) according to the remaining test results. The rejection of the remaining test results is repeated considering the fulfillment of condition (E.6) using a new (corrected) calibration dependence.

Particular values \u200b\u200bof concrete strength must meet the requirements of 6.1.7.

E.3 Parameters of the calibration dependence

For the adopted calibration dependence, determine:

The minimum and maximum values \u200b\u200bof the indirect characteristic H min, H max;

Standard deviation S T. H. M of the constructed calibration dependence according to the formula (E.7);

The correlation coefficient of the calibration dependence r according to the formula

where the average value of concrete strength according to the calibration dependence R̅ n is calculated by the formula

here the values \u200b\u200bof R i n, R i f, R̅ f, N - see the explications to formulas (E.3), (E.6).

E.4 Correction of the calibration dependence

Correction of the established calibration dependence, taking into account the additionally obtained test results, should 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 \u200b\u200bof the indirect indicator are added to the existing test results.

As data accumulates to build a calibration dependence, the results of previous tests, starting with the very first ones, 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 \u200b\u200bof the indirect characteristic, the calibration dependence and its parameters are set again using the formulas (E.1) - (E.9).

F.5 Conditions for the application of the calibration dependence

The use of a calibration dependence for determining the strength of concrete according to this standard is allowed only for values \u200b\u200bof an indirect characteristic falling within the range from H min to H max.

If the correlation coefficient r< 0, 7 или значение S T . H . M / R̅ ф > 0, 15, then control and assessment of strength according to the obtained dependence are not allowed.

Appendix G
(required)

G.1 The value of concrete strength, determined using the calibration dependence established for concrete that differs from the tested one, is multiplied by the coincidence coefficient K s. The K s value is calculated by the formula

where R os i - the strength of concrete in the i-th section, determined by the method of separation with chipping or testing of cores according to GOST 28570;

R indirect i - strength of concrete in the i-th area, determined by any indirect method according to the used calibration dependence;

n is the number of test sites.

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

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

Each particular value R os i / R indirect i must be at least 0, 7 and no more than 1, 3:

;

Each particular value R os i / R indirect i must differ from the average value by no more than 15%:

The values \u200b\u200bof R os i / R indirect i that do not satisfy the conditions (Zh.2), (Zh.3) should not be taken into account when calculating the coincidence coefficient K s.

I.1 In accordance with GOST 18105, when controlling the strength of concrete of prefabricated structures (tempering or transfer), the number of controlled structures of each type is taken at least 10% and at least 12 structures from a batch. If a batch consists of 12 designs or less, a continuous inspection is carried out. In this case, the number of sections must be at least:

1 x 4 m length of linear structures;

1 by 4 m 2 of the area of \u200b\u200bflat structures.

I.2 In accordance with GOST 18105, when controlling 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 by non-destructive methods.

I.3 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 gripper for flat structures (wall, floor, foundation slab);

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

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

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

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

Name of structures (batch of structures), design class of concrete strength, date of concreting or age of concrete of tested structures	Description (1)	N area according to the scheme or location in the axes (2)	Concrete strength, MPa		Concrete strength class (5)
			plot (3)	medium (4)






(1) The mark, symbol and (or) location of the structure in the axes, structure zone, or part of a monolithic and precast-monolithic structure (grip), for which the concrete strength class is determined. (2) Total number and location of sites in accordance with 7.1.1. (3) Strength of concrete of the site in accordance with 7.1.5. (4) Average strength of concrete of a structure, structure zone or part of a monolithic and precast-monolithic structure with the number of sections meeting the requirements of 7.1.1. (5) The actual strength class of concrete of a structure or part of a monolithic and precast-monolithic structure in accordance with clauses 7.3 - 7.5 of GOST 18105, depending on the selected control scheme. Note - The presentation in the column "Concrete strength class" of the estimated values \u200b\u200bof the class or values \u200b\u200bof the required concrete strength for each section separately (assessment of the strength class for one section) is not permissible.

The compressive strength of concrete is the main indicator that characterizes concrete. It is on him that the non-destructive testing of concrete strength in monolithic structures is oriented. There are two systems for expressing this indicator:

Concrete class, B is the so-called cubic strength (i.e. a compressible cube-shaped specimen), indicating the withstanding pressure in MPa. The fraction of the probability of failure during the strength test of concrete does not exceed 5 units out of 100 tested samples. It is designated by the Latin letter B and a number indicating strength in MPa. According to SNiP 2.03.01–84 "Concrete and reinforced concrete structures".
Concrete grade, M is the ultimate compressive strength of concrete, kgf / cm². It is denoted by the Latin letter M and numbers from 50 to 1000. The maximum deviation that allows the control and assessment of concrete strength in accordance with GOST 26633-91 “Heavy and fine-grained concrete is 13.5%.

The concrete grade and class are determined after 28 days from the day of pouring, under normal conditions, or the calculation is carried out taking into account the coefficient (after 7-14 days the material acquires 60-80% of the brand strength, after 28 days about 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: the activity of the cement, the content of cement, the ratio of water to cement by weight, the quality of aggregates, the quality of mixing and the degree of compaction, the age and conditions of concrete hardening, and repeated vibration. The speed of concrete hardening 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 an increase in the content of cement in concrete, its strength increases up to a certain limit. Then it grows slightly, while 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.

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

Chipping-off methodoccupies a special place among non-destructive methods for determining the strength of concrete. Considered a non-destructive method, the shear-off method is inherently a destructive method, since the strength of concrete is assessed by the force required to break a small volume of concrete, which makes it possible to most accurately assess its actual strength. Therefore, this method is used not only to determine the strength of concrete of unknown composition, but can also serve to build calibration dependences for other non-destructive testing methods. This method is applied to heavy concretes and structural concretes on lightweight 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 a special anchor device is pulled out of it. Such ultrasonic method for testing concrete strength allows to determine the compressive strength for 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 methods of non-destructive testing for determining the strength of concrete is measuring with a sclerometer, or as it is also called, the Schmidt hammer.

The devices below can be used to carry out non-destructive testing of concrete. This allows you to more accurately predict the physical characteristics of finished reinforced concrete structures, which means - to minimize losses to the construction organization and protect the customer from all kinds of troubles.

Among other things, such quality control of concrete allows for inspections of concrete, the temperature of which has dropped below 0 ° C. Traditional methods of concrete quality control in laboratory conditions cannot boast of such convenience: earlier it was necessary to take a sample and check it at room temperature in laboratory conditions. An interesting modern solution is also the fact that contractors may not resort to the services of specialized organizations at every stage of 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 rather compact and mobile, and preparation of results takes a minimum of time.

Serial numbers 1

Sample numbers /

Test point numbers for

Rj t kts / cm 3

f U max ** min “

16.9 17.5 18.8 19.0 18.2 Comp. 18.1

Schmidt hammer Original Schmidt type N

Testing of concrete products by means of the Schmidt hammer Original Schmidt is the most widespread measurement technique worldwide that does not destroy concrete in accordance with GOST 22690-2015

For each specific test on concrete products, Proceq offers the appropriate hammer model.

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

Our hammers types N, NR, L and LR are specially designed to evaluate the quality and compressive strength of concrete products ranging from 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 \u200b\u200bon paper tape.

Type Approval Certificate SI Brochure Schmidt Hammers

POS-50MG4 "Skol" is intended for non-destructive testing of concrete strength by spalling ribs, tearing off with spalling and tearing off steel discs in accordance with GOST 22690-2015.

Measuring the strength of concrete using such equipment is allowed both on projects under construction and on finished buildings. The device is indispensable in the construction industry, in the work of utilities and restoration bureaus that 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.

STATE STANDARDS OF THE UNION OF SSR

HEAVY CONCRETE

METHODS FOR DETERMINING STRENGTH WITHOUT FRACTURE BY INSTRUMENTS OF MECHANICAL ACTION

Official edition

USSR STATE COMMITTEE ON STANDARDS Moscow

UDC 691.32: 620.17: 006.354 Group Ж19

STATE STANDARD OF THE UNION OF SSR

HEAVY CONCRETE

General Requirements for Methods for Determining Strength without Destruction by Mechanical 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 Affairs dated August 22, 1977 No. 128, the date for the introduction of

from 01.07. 1978 year

Failure to comply with the standard is punishable by law

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

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

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

3. To build the calibration dependence, cubes 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 chipping the rib of the structure and tearing off.

Official edition Reprinting prohibited

Reissue. November 1981

Op. 10 GOST 22690.0-77

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

1. Test object ________

2. Test date _

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

4. The type of concrete and its design strength _

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

6. Test results (see table)

P. 2 GOST 22690.0-77

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

4. When controlling the strength of concrete in erected structures, at least 20 cubic specimens are cut out from various sections, and the result of testing one specimen is equated to the result of testing a series of specimens.

It is allowed to establish the 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 areas and the sample cut should be no more than 100 mm apart from each other.

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

The procedure for calculating the equation of the calibration dependence is given in the recommended Appendix 2, and an example of its construction is in the Reference Appendix 3.

6. Evaluation of the calibration dependence error is carried out in accordance with GOST 17624-78.

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

8. Devices 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 in an act.

9. Areas for testing concrete should be selected on structural surfaces that were in contact during manufacture with metal, planed wood or other smooth formwork. Ес-

GOST 22690.0-77 pp. 3

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

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

11. The strength of concrete in a section of the structure is determined by the average value of the indirect characteristic of the strength of concrete in this section, using the established calibration dependence, taking into account the rejection of abnormal results, made in accordance with mandatory Appendix 1.

The test results should be recorded in a log, the form of which is given in the recommended annex 4.

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

P. 4 GOST 22690.0-77

APPENDIX 1 Mandatory

RULES FOR DISCLAIMING ABNORMAL TEST RESULTS

1. 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 press test of one sample in a series;

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

c) for a single non-destructive test result on 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 formula (1), exceeds the permissible value of Tc given in table. 1. _

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

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

Table 1

The value of T and

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

Xi shah and Xi min are the 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 to construct the calibration dependence.

When assessing 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 pp. five

PROCEDURE FOR CALCULATING THE EQUATION OF THE GRADING DEPENDENCE "INDIRECT CHARACTERISTIC - STRENGTH"

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

with a range of fluctuations in concrete strength 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)

Odds about 0; ah b x are calculated by the formulas.

# 0 - R- (i \\ '//, * (3)

"\u003d‘ -CH? -Z-: (4)

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




B n \u003d c ^ - b "".

The average values \u200b\u200bof strength R and indirect characteristics I, necessary to determine these coefficients, are calculated by the formulas:

* \u003d Chg:< 7 >

In /? - \u003d * "" s -; (nine)

The Ri and Hi values \u200b\u200bare, respectively, the 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 construct the calibration dependence.

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

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

P. 6 GOST 22690.0-77

APPENDIX $ Reference

EXAMPLES OF CONSTRUCTING THE GRADING DEPENDENCE AND DISCLOSING ANOMALOUS 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 plot the relationship between the rebound value (R) and the compressive strength of the control samples, 29 series of specimens were tested on a press (R) (A r * \u003d 29). The average results for each series are shown in table. !.

Table 1

Series number	H, division	Serine number	W, division	R, kgf / cm "

Since the measurement range of concrete strength 330-169 "\u003d" 170 kgf / cm * is less than 200 kgf / cm *, then, in accordance with the methodology described in the recommended Appendix 2, the equation of the sought dependence is assumed to be linear: * \u003d Oo + ag Y. Equation coefficients calculated by substituting the data of the table in_foriults (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 Ya-413.

The dependency graph is shown in the drawing.

GOST 22690.0-77 pp. 1

Dependence "Indirect characteristic (rebound value) - strength"

R, kgf / cm 1

Calculation of root-mean-square deviations in strength in a series of 3 samples and in rebound value in 5 measurements on one sample.

When plotting the 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

Series numbers 1	Sample numbers; \|	Test point numbers for	/? , KGOSL1 *

Page 8 GOST 22690.0-77

Continuation

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

S- --- - \u003d 18 kix / cm l.

Using the same formula, calculate the standard deviation of the rebound height on the KM device in the samples

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

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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, using the formula (1) of mandatory Appendix 1, calculate the value

GOST 22690.0-77 pp. nine

which is less than the value determined from the table T to -1.74 for three samples in a 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 differs from the sample mean. To check the abnormality of this result, using the formula (1) of mandatory Appendix 1, calculate the value

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