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, acceptance, application, updating and cancellation "
1 DEVELOPED by the structural division of JSC "Research Center" Construction "Research, Design and Technological Institute of Concrete and Reinforced Concrete named after A.A. Gvozdeva (NIIZHB)
2 INTRODUCED by the Technical Committee for Standardization TC 465 "Construction"
3 ACCEPTED by the Interstate Council for Standardization, Metrology and Certification (Minutes dated June 18, 2015 No. 47)
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Country short name |
Code of the country |
Abbreviated name of the national authority |
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Armenia |
Ministry of Economy of the Republic of Armenia |
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Belarus |
State Standard of the Republic of Belarus |
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Kazakhstan |
Gosstandart of the Republic of Kazakhstan |
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Kyrgyzstan |
Kyrgyzstandard |
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Moldova |
Moldova-Standard |
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Russia |
Rosstandart |
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Tajikistan |
Tajikstandart |
4 By order of the Federal Agency for Technical Regulation and Metrology dated September 25, 2015 No. 1378-st, the interstate standard GOST 22690-2015 was put into effect as a national standard of the Russian Federation 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 - Part2: Non-destructive testing - Determination of rebound number.
EN 12504-3: 2005 Testing concrete in structures - Determination of pull-outforce.
Degree of Compliance - Non-Equivalent (NEQ)
Information about changes to this standard is published in the annual information index "National Standards", and the text of changes and amendments is published in the monthly information index "National Standards". In case of revision (replacement) or cancellation of this standard, a corresponding notice will be published in the monthly information index "National Standards". Relevant information, notice and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet
GOST 22690-2015
Concretes
Determination of strength by mechanical methods of nondestructive testing
Date of introduction - 2016-04-01
1 area of use
This standard applies to structural heavy, fine-grained, 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.
2 Normative references
This standard uses normative references to the following interstate standards:
Note - Standard test schemes are applicable over a limited range of concrete strength (see appendices and ). For cases not related to standard test schemes, calibration dependencies should be established according to general rules.
4.6 The test method should be selected taking into account the data given in the table and additional restrictions established by the manufacturers of specific measuring instruments. The use of methods outside the ranges of concrete strength recommended in the table is 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
|
Method name |
Limiting values of concrete strength, MPa |
|
Rebound and plastic deformation |
5 - 50 |
|
Impact impulse |
5 - 150 |
|
Detachment |
5 - 60 |
|
Chipping a rib |
10 - 70 |
|
Shearing off |
5 - 100 |
4.7 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 the concrete of the controlled structures and its sections should not differ from the age of the concrete of the structures (sections, samples) tested to establish the calibration dependence by more than 25%. Exceptions are strength control and 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 ° C, when establishing or linking a calibration dependence, taking into account the requirements. The concrete temperature during testing must correspond to the temperature specified 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 necessary, testing of concrete structures after heat treatment at surface temperature T≥ 40 ° С (to control the tempering, transfer and stripping strength of concrete), the calibration dependence is established after determining the strength of concrete in a structure by an indirect non-destructive method at a temperature t = (T± 10) ° С, and concrete testing by direct non-destructive method or specimen testing - after cooling at normal temperature.
5 Measuring instruments, apparatus and instrument
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 for the application.
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 "meter reading - concrete strength" or binding the dependence set in the device in accordance with.
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 gauge in accordance with GOST 577, etc.) - with an error no more than 0.01 mm.
5.4 The Routine Pull-Out and Ribbed Pull Test Schemes provide for the use of anchoring devices and grips in accordance with Appendices and.
5.5 For the shear-off method, anchoring 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 of a diameter should be used, with the roughness parameters of the glued surface at least Ra= 20 microns according to GOST 2789. The adhesive for gluing the disc must ensure the strength of adhesion to concrete, at which destruction occurs along the concrete.
6 Test preparation
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 using 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 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 unified production technology, differing in the nominal composition and the value of the normalized strength, subject to the requirements.
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.
6.1.5 For direct non-destructive methods, it is allowed to use the dependencies given in the appendices and for all types of rated 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 plots 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 dependence of the form R = a + bK(where R- the strength of concrete, K- an indirect indicator). The procedure for establishing, evaluating the parameters and determining the conditions for using a linear calibration dependence is given in the appendix.
6.1.7 When constructing the calibration dependence of the deviation of the unit values of concrete strength R i f from the average value of the concrete strength of the sections or samples used to construct the calibration dependence, should be within:
From 0.5 to 1.5 average values of concrete strength at ≤ 20 MPa;
From 0.6 to 1.4 average value of concrete strength at 20 MPa< ≤ 50 МПа;
From 0.7 to 1.3 average value of concrete strength at 50 MPa< ≤ 80 МПа;
From 0.8 to 1.2 average value of concrete strength at> 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 technique is given in the appendix.
6.1.9 It is allowed to apply indirect non-destructive methods for determining the strength of concrete, using the calibration dependences established for concrete that differs from the tested concrete in composition, age, hardening conditions, moisture, with reference in accordance with the procedure for the application.
6.1.10 Without reference to specific conditions for the application, the calibration dependencies established for concrete that differ from the tested one may only be used to obtain approximate strength values. It is not allowed to use approximate strength values without reference to specific conditions for assessing the strength class of concrete.
Then, the plots are selected in the amount provided for, on which the maximum, minimum and intermediate values of 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 constructing 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 ° C and are tested by a direct non-destructive method. 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 the structure.
6.3.1 When constructing a calibration dependence for control samples, the dependence is established according to the unit values of the indirect indicator and the strength of concrete of standard sample cubes.
For a unit 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 unit value of concrete strength, the strength of concrete in a series according to GOST 10180 or one sample (calibration dependence for individual samples) is taken. 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 in accordance with 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 of 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 established in.
6.3.3 The calibration dependence for the methods of elastic rebound, shock pulse, plastic deformation, separation and spalling of the rib is established on the basis of the test results of the manufactured cube specimens, 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, the main and control samples are made according to. 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 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 × 100 × 100 mm for rebound, shock impulse, plastic deformation methods, as well as for the shear-off method (control samples);
200 × 200 × 200 mm for the method of chipping the rib of the structure;
300 × 300 × 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 the section on the lateral (in the direction of concreting) faces of the 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 per section according to the table, 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 support plates of the press. The test results in accordance with GOST 10180 increase by 5%.
7 Testing
7.1.1 The number and location of controlled sections in structures must comply with the requirements of GOST 18105 and be indicated in the design documentation for the structure or be installed taking into account:
Control tasks (determination of the actual class of concrete, stripping or tempering strength, identification of 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 the appendix. When determining the concrete strength of the structures under study, the number and location of the sections 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 100 to 900 cm 2.
7.1.3 The total number of measurements at each site, the distance between the measurement sites at the site and from the edge of the structure, the thickness of the structures at the site of measurements should be not less than the values given in the table, depending on the test method.
Table 2 - Requirements for test sites
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Method name |
Total number |
Minimum |
Minimum |
Minimum |
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Bouncing rebound |
||||
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Impact impulse |
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Plastic deformation |
||||
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Chipping a rib |
||||
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Detachment |
2 diameters |
|||
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Tear-off with spalling at working depth of anchor embedmenth: |
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≥ 40mm |
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|
< 40мм |
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 the table.
7.1.5 The strength of concrete in the controlled section of the structure is determined by the average value of the indirect indicator according to the calibration dependence established in accordance with the requirements of the section, provided that the calculated value of the indirect indicator is within the established (or tied) relationship (between the lowest and highest strength values ).
7.1.6 The roughness of the surface of a section of concrete of structures when tested by the methods of rebound, shock impulse, 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.
7.2.1 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;
7.3.1 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 can be carried out through sheets of carbon and white paper (in this case, tests to establish the calibration dependence are carried out using the same paper);
The values of the indirect characteristic are recorded in accordance with the instructions for use of the device;
Calculate the average value of the indirect characteristic at the site of the structure.
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 that the position of the device during the test of the structure relative to the horizontal be taken the same as during the test 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.
7.5.1 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 where the disc is glued, 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 adhesive 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 projection area 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 the 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 the tearing surface was less than 80% of the disc area.
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 into 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 speed of 1.5 - 3.0 kN / s;
Record the reading of the force meter of the device R 0 and the amount of slip of the anchor Δ h(difference between the actual tear-out depth and the embedment depth of the anchor device) with an accuracy of at least 0.1 mm.
7.6.3 Measured value of the pull-out force R 0 is multiplied by the correction factor γ, determined by the formula
where h- working depth of the anchor device embedment, mm;
Δ h- the amount of slip of the anchor, 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 more than twice, and also if the tear-out depth differs from the embedment depth of the anchor device by more than 5% (Δ h > 0,05h, γ> 1.1), then the test results can be taken into account only for an approximate assessment of the strength of concrete.
Note - Approximate values of concrete strength are not allowed to be used for assessing concrete strength class and building calibration dependencies.
7.6.5 The test results are disregarded if the tear-out depth differs from the embedment depth of the anchor device by more than 10% (Δ h > 0,1h) or the reinforcement was exposed at a distance from the anchor device that is less than the depth of its embedding.
7.7.1 When testing the rib shear method, 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 the lowest 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 fixed to 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 shearing depth;
Determine the average shear force.
7.7.3 The test results are not taken into account if the reinforcement was exposed during spalling of concrete or the actual spalling 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, which indicates:
Type of construction;
Concrete design class;
Concrete age;
The strength of the concrete of each controlled area by;
Average concrete strength of the structure;
Areas of a structure or part of it if the requirements are met.
The form of the test results presentation table is given in the appendix.
8.2 The processing and assessment of compliance with the established requirements of the actual concrete strength values obtained 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 according to GOST 18105 (schemes "A", "B" or "C") in cases where the strength of concrete is determined by the calibration dependence, built in accordance with section ... When using previously installed dependencies by binding them (by application ) statistical control is not allowed, and the assessment of the class of concrete 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 types of devices with serial numbers, information on instrument checks;
About the adopted 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 reference (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 with an indication of their location;
Test results;
Methodology, results of processing and evaluation of the data obtained.
Appendix A
(required)
Standard Shear Pull Test Arrangement
A.1 The standard shear peel test scheme provides for tests to be performed while meeting the requirements of -.
A.2 The standard test setup is applicable in the following cases:
Testing of heavy concrete with compressive strength from 5 to 100 MPa;
Testing 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 should adhere evenly to the concrete surface at a distance of at least 2 h from the axis of the anchor device, where h- the working depth of the embedment of the anchor device. The test scheme is shown in the figure.
1
2
- support of the loading device;
3
- capture of the loading device; 4
- transitional elements, rods; 5
- anchor device;
6
- concrete pulled out (tear-off cone); 7
- tested structure
Figure A.1 - Schematic of a shear peel test
A.4 Three types of anchor devices are used in the standard shear-pull test setup (see figure). 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
- segmental grooved 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 permissible ranges of the measured concrete strength for them under the standard test scheme are indicated in the table. For lightweight concrete, in the standard test scheme, only anchoring devices with an embedment depth of 48 mm are used.
Table A.1 - Parameters of anchor devices for the standard test scheme
|
Anchor type |
Anchor diameter |
Embedment depth of anchor devices, |
Permissible for anchor device |
||
|
working h |
complete h " |
heavy |
lung |
||
|
45 - 75 |
|||||
|
10 - 50 |
10 - 40 |
||||
|
40 - 100 |
|||||
|
5 - 100 |
5 - 40 |
||||
|
10 - 50 |
|||||
A.6 Designs of anchors of types II and III should provide preliminary (before the application of the load) compression of the hole walls at the working depth of embedment. h and post-test slip control.
Appendix B
(required)
Standard rib shear test setup
B.1 The standard scheme for testing the rib shear method provides for testing in compliance with the requirements -.
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 granite and limestone crushed stone.
B.3 For the tests, a device is used, consisting of a power exciter with a force-measuring unit and a gripper with a bracket for local cleavage of the rib of the structure. The test scheme is shown in the figure.
1
- a device with a loading device and a force measuring device; 2
- support frame;
3
- chipped concrete; 4
- tested structure; 5
- gripper with a bracket
Figure B.1 - Schematic of the rib shear test
B.4 In case of local spalling of the rib, the following parameters should be provided:
Cleavage depth a= (20 ± 2) mm;
Cleavage width b= (30 ± 0.5) mm;
The angle between the direction of action of the load and the normal to the loaded surface of the structure β = (18 ± 1) °.
Appendix B
(recommended)
Calibration dependence for the chipping-off method
When carrying out tests by the method of pull-off with spalling according to the standard scheme according to the appendix, the cubic compressive strength of concrete R, MPa, it is allowed to calculate according to the calibration dependence according to the formula
|
R = m 1 m 2 P, |
where m 1 - coefficient taking into account the maximum size of the coarse aggregate in the tear-out zone, taken equal to 1 with the aggregate size less than 50 mm;
m 2 - coefficient of proportionality for the transition from the force pulling out kilonewtons to the strength of concrete in megapascals;
R- 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 coefficient m 2 are taken according to the table.
Table B.1
|
Anchor type |
Range |
Anchor diameter |
Embedment depth of anchor |
Coefficient valuem 2 for concrete |
|
|
heavy |
lung |
||||
|
45 - 75 |
|||||
|
10 - 50 |
|||||
|
40 - 75 |
|||||
|
5 - 75 |
|||||
|
10 - 50 |
|||||
Odds m 2 when testing heavy concrete with an average strength above 70 MPa, it should be taken in accordance with GOST 31914.
Appendix D
(recommended)
Calibration Constraint for the Rib Cleaving Method
with standard test setup
When performing the test by spalling ribs according to the standard scheme according to the appendix, the cubic compressive strength of concrete on granite and limestone crushed stone R, MPa, it is allowed to calculate according to the calibration dependence according to the formula
|
R = 0,058m(30R + R 2), |
where m- coefficient taking into account the maximum size of the coarse aggregate and 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 - for aggregate size from 30 to 40 mm;
R- shearing force, kN.
Appendix D
(required)
Requirements for instruments for mechanical testing
Table E.1
|
The name of the characteristics of the devices |
Characteristics of instruments for the method |
|||||||||||||||||||||||||||||||||||||
|
elastic |
percussion |
plastic |
detachment |
chipping |
separation from |
|||||||||||||||||||||||||||||||||
|
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 |
||||||||||||||||||||||||||||||||||||||
|
Conical indenter angle |
30 ° - 60 ° |
|||||||||||||||||||||||||||||||||||||
|
Imprint diameter,% of indenter diameter |
20 - 70 |
|||||||||||||||||||||||||||||||||||||
|
Perpendicularity tolerance when a load is applied at a height of 100 mm, mm |
||||||||||||||||||||||||||||||||||||||
|
Impact energy, J, not less |
0,02 |
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Load increase rate, kN / s 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 (), it is corrected by rejecting single test results that do not satisfy the condition: where the average value of concrete strength according to the calibration dependence is calculated by the formula here the values R i H, R i f,, N- see explications to formulas (), (). 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 of the indirect indicator are added to the existing test results. As data accumulates to build a calibration dependence, the results of previous tests, starting from 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 of the indirect characteristic, the calibration dependence and its parameters are set again according to the formulas () - (). 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 of an indirect characteristic falling in the range from H min to N max. If the correlation coefficient r < 0,7 или значение Appendix G
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where R wasps i- concrete strength in i-th section, determined by the method of separation with spalling or testing of cores in accordance with GOST 28570;
R indirect i- concrete strength in i-th section, determined by any indirect method according to the used calibration dependence;
n- 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 data point R wasps i /R indirect i must be at least 0.7 and no more than 1.3:
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1 x 4 m length of linear structures; 1 by 4 m 2 of the area of flat structures. Appendix K
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Designation of structures |
Designation 1) |
No. of plot according to the scheme |
Concrete strength, MPa |
Strength class |
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section 3) |
average 4) |
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1) The brand, symbol and (or) location of the structure in the axes, the zone of the structure, or part of a monolithic and precast-monolithic structure (capture), for which the concrete strength class is determined. 2) The total number and location of sites in accordance with . 3) The strength of the concrete of the site in accordance with . 4) Average strength of concrete of a structure, structure zone or part of a monolithic and precast-monolithic structure with a number of sections that meet the requirements . 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 GOST 18105 depending on the selected control scheme. Note - The presentation in the column "Concrete strength class" of the estimated values of the class or the values of the required concrete strength for each section separately (assessment of the strength class for one section) is not permissible. |
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Key words: structural heavy and light concrete, monolithic and prefabricated concrete and reinforced concrete products, structures and structures, mechanical methods for determining compressive strength, rebound, shock impulse, plastic deformation, separation, rib shearing, shearing off with shearing
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 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 in the range between the smallest and largest values of the indirect indicator in the samples tested when constructing 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 examined structures, 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 given 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 the 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; it is recommended that the position of the device during the test of the structure relative to the horizontal be taken the same as when testing the samples to establish the 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 of the device; calculate the average value of the indirect characteristic at the site of the structure.
4.7. Plastic deformation method.
4.7.1. When testing by the method of plastic deformation, the distance from the test sites to the reinforcement should 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 of the indirect characteristic in accordance with the instructions for use of the device; calculate the average value of the indirect characteristic at the site of the structure. 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; it is recommended that the position of the device during the test of the structure relative to the horizontal be taken the same as when testing the samples to establish the 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 of the device; calculate the average value of the indirect characteristic at the site of the structure.
4.9. Tear-off method
4.9.1. When tested by the pull-off method, 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 where the disc is glued, 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 layer of glue 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 readings 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 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 the tearing surface was less than 80% of the disc area.
4.10. Pull-off method with spalling 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 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 devices by more than 5%, then the test results may be taken into account only for an approximate assessment. concrete strength.
4.11. Rib cleaving method
4.11.1. When testing the rib shear method, 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 the lowest 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, 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 shearing 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 Technological Institute of Concrete and Reinforced Concrete named after A.A.Gvozdev (NIIZhB)
2 Introduced by the Technical Committee for Standardization TC 465 "Construction"
3 Adopted by the Interstate Council for Standardization, Metrology and Certification (minutes of June 18, 2015 N 47)
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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 |
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Ministry of Economy of the Republic of Armenia |
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Belarus |
State Standard of the Republic of Belarus |
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Kazakhstan |
Gosstandart of the Republic of Kazakhstan |
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Kyrgyzstan |
Kyrgyzstandard |
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Moldova-Standard |
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Rosstandart |
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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.
Degree of Compliance - Non-Equivalent (NEQ)
6 Replaces GOST 22690-88
1 area of use
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.
2 Normative references
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 the 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 concretes 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 the editions 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 not affecting this reference.
3 Terms and definitions
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, resilient 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 (separation 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 strength characteristics (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 General
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 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:
The 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 upon impact of an indenter or indentation of an indenter into the concrete surface;
Impact impulse method based on the relationship between the strength of concrete and the impact energy and its changes at the moment the striker collides with 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 the 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 the 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 dependencies should be established according to general rules.
4.6 The test method should be selected taking into account the data given in Table 1 and additional restrictions established by the manufacturers of specific measuring instruments. The use of methods outside the 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 sections of structures that do not have visible damage (peeling of the protective layer, cracks, cavities, etc.).
4.9 The age of the concrete of the controlled structures and its sections should not differ from the age of the concrete of the structures (sections, samples) tested to establish the calibration dependence by more than 25%. Exceptions are strength control and 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 linking a calibration dependence, taking into account the requirements of 6.2.4. The concrete temperature during testing must correspond to the temperature specified 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 of structures after heat treatment at a surface temperature of 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 of t = (T ± 10) ° С, and concrete testing by direct non-destructive method or specimen testing - after cooling down at normal temperature.
5 Measuring instruments, apparatus and instrument
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 the establishment of the calibration dependence "the reading of the device - the strength of concrete" or the binding of the dependence established in the device in accordance with 6.1.9.
5.3 A tool for measuring the diameter of indentations (vernier 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 gauge in accordance with GOST 577, etc.) - with an error no more than 0.01 mm.
5.4 Standard test procedures for shear-off and rib-chipping tests provide for the use of anchoring devices and grips in accordance with Appendices A and B.
5.5 For the shear-off method, anchoring 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 = 20 microns 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 Test preparation
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 using 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 unified 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 dependencies 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 plots or samples used in plotting the dependence, and the correlation coefficient (index) is not less than 0.7.
It is recommended to use a linear relationship of the form R = 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 of the concrete strength R i ph from the average value of the concrete strength of the sections or specimens R̅ ph 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 of the average value of concrete strength R̅ f at 50 MPa< R̅ ф ≤ 80 МПа;
From 0.8 to 1.2 of the average value of concrete strength R̅ f at R̅ f> 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 only be used to obtain approximate strength values. It is not allowed to use approximate strength values without reference to specific conditions for assessing 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 of 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 direct non-destructive method or by testing of selected samples, is taken.
6.2.2 The minimum number of single values for plotting 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 amount specified in 6.2.2, on which the maximum, minimum and intermediate values of 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 constructing 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 ° C and are tested by a direct non-destructive method. 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 the 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 of the indirect indicator and the strength of concrete of standard sample cubes.
For a unit 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 unit value of concrete strength, the strength of concrete in a series according to GOST 10180 or one sample (calibration dependence for individual samples) is taken. 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 in accordance with 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 of 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 established in 6.1.7.
6.3.3 The calibration dependence for the methods of elastic rebound, shock pulse, plastic deformation, separation and spalling of the rib is established on the basis of the test results of the manufactured cube specimens, 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. An 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 the 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 support plates of the press. The test results in accordance with GOST 10180 increase by 5%.
7 Testing
7.1 General requirements
7.1.1 The number and location of controlled sections in structures must comply with the requirements of GOST 18105 and be indicated in the design documentation for the structure or be installed taking into account:
Control tasks (determination of the actual class of concrete, stripping or tempering strength, identification of 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 monitoring concrete strength 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 100 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 given in Table 2, depending on the test method.
Table 2 - Requirements for test sites
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Method name |
Total number of measurements on the site |
Minimum distance between 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 |
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Bouncing rebound | ||||
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Impact impulse | ||||
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Plastic deformation | ||||
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Chipping a rib | ||||
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2 disc diameters | ||||
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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 lowest and highest values strength).
7.1.6 The roughness of the surface of a section of concrete of structures when tested by the methods of rebound, shock impulse, 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 can be carried out through sheets of carbon and white paper (in this case, tests to establish the calibration dependence are carried out using the same paper);
The values of the indirect characteristic are recorded in accordance with the 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 that the position of the device during the test of the structure relative to the horizontal be taken the same as during the test 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 where the disc is glued, the surface layer of concrete with a depth of 0.5 - 1 mm is removed and the surface is cleaned of dust;
The disc is adhered to the concrete by pressing the disc and removing excess adhesive 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 projection area 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 the 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 the 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 into 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 anchor device embedment, 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 structure surface 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> 0.05h , γ> 1, 1), then the test results can be taken into account only for an approximate assessment of the strength of concrete.
Note - Approximate values of concrete strength are not allowed to be used to assess the strength class of concrete and build 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> 0.1h) or the reinforcement was exposed at a distance from the anchor device less than the embedment depth.
7.7 Rib shear method
7.7.1 When testing the rib shear method, 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 the lowest 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 fixed to 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 shearing depth;
Determine the average shear force.
7.7.3 The test results are not taken into account if the reinforcement was exposed during spalling of concrete or the actual spalling 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, which indicates:
Type of construction;
Concrete design class;
Concrete age;
Strength of concrete of each controlled 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 The processing and assessment of compliance with the established requirements of the actual concrete strength values obtained 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 class of concrete 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 types of devices with serial numbers, information on instrument checks;
About the adopted 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 reference (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 with an indication of their location;
Test results;
Methodology, results of processing and evaluation of the data obtained.
Appendix A
(required)
Standard Shear Pull Test Arrangement
A.1 The standard shear peel test arrangement is based on the test carried out in accordance with A.2 to A.6.
A.2 The standard test setup is applicable in the following cases:
Testing of heavy concrete with compressive strength from 5 to 100 MPa;
Testing 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 measuring device; 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 for in 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 permissible 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.
Table A.1 - Parameters of anchor devices for the standard test scheme
|
Anchor device type |
Embedment depth of anchor devices, mm |
Permissible range for the anchor device for measuring the compressive strength of concrete, MPa |
|||
|
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 the test.
Appendix B
(required)
Standard rib shear test setup
B.1 The standard test scheme using the shear ribbing 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:
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 granite and limestone crushed stone.
B.3 For the tests, a device is used, consisting of a power exciter with a force-measuring unit and a gripper with a bracket for local cleavage 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 - gripper with a bracket
"Figure B.1 - Schematic of the rib shear test"
B.4 In case of local spalling of the rib, the following parameters should be provided:
Chipping depth a = (20 ± 2) mm;
Chipping width b = (30 ± 0.5) mm;
The angle between the direction of action of the load and the normal to the loaded surface of the structure β = (18 ± 1) °.
Calibration dependence for the shear-off method with a standard test setup
When testing by the method of pull-off with spalling according to the standard scheme in accordance with Appendix A, the cubic compressive strength of concrete R, MPa, is allowed to be calculated 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 tear-out zone and is taken equal to 1 when the aggregate size is less than 50 mm;
m 2 is the proportionality coefficient for the transition from the pull-out force in kilonewtons to the concrete strength 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 coefficient m 2 are taken according to Table B.1.
Table B.1
|
Anchor device type |
Measured concrete compressive strength range, MPa |
Anchor device diameter d, mm |
Embedment depth of anchor device, mm |
The value of the coefficient m 2 for concrete |
|
|
heavy | |||||
Coefficients m 2 when testing heavy concrete with an average strength above 70 MPa should be taken in accordance with GOST 31914.
Calibration dependence for the rib shearing method with a standard test scheme
When performing the test by spalling ribs according to the standard scheme in accordance with Appendix B, the cube 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 = 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)
Requirements for instruments for mechanical testing
Table E.1
|
The name of the characteristics of the devices |
Characteristics of instruments for the method |
|||||
|
elastic rebound |
shock impulse |
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 | ||||||
|
Conical indenter angle | ||||||
|
Imprint 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. |
||||||
Methods for establishing, correcting and evaluating the parameters of calibration dependences
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), its correction is carried out 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 of 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 of the indirect characteristic H min, H max;
Standard deviation S T. H. M of the built 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 of 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 of 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 of the indirect characteristic, the calibration dependence and its parameters are set again according to 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 in accordance with this standard is allowed only for values of 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)
Calibration dependence binding method
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 is 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 section, 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 of R os i / R indirect i, which do not satisfy the conditions (Zh.2), (Zh.3), should not be taken into account when calculating the coincidence coefficient K s.
Assignment of the number of test sites for prefabricated and monolithic structures
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 structures 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 flat 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, crossbars);
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.
Form of the table of presentation of test results
|
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 brand, symbol and (or) location of the structure in the axes, the zone of the structure, or part of a monolithic and precast-monolithic structure (grip), for which the strength class of concrete is determined. (2) The total number and location of sites in accordance with 7.1.1. (3) Strength of the 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 of the class or the values of the required concrete strength for each section separately (assessment of the strength class for one section) is not permissible. |
|||||
V.A.Klevtsov, Dr. Sciences (topic leader); M.G. Korevitskaya, Cand. tech. sciences; YK Matveev; V.N. Artamonov; N.S.Vostrova; A.A. Grebenik; G.V. Sizov, Cand. tech. sciences; D.A. Korshunov, Cand. tech. sciences; M.V. Sidorenko, Cand. tech. sciences; Yu.I. Kurash, Cand. tech. sciences; A.M. Leshchinsky, Cand. tech. sciences; V.R. Abramovsky; V. A. Dorf, Cand. tech. sciences; E.G. Sorkin, Cand. tech. sciences; V.L. Chernyakhovsky, Cand. tech. sciences; I.O. Krol, Cand. tech. sciences; S.Ya. Khomutchenko; Ya.E. Ganin; O.Yu.Sammal, Cand. tech. sciences; A.A. Rulkov, Cand. tech. sciences; P.L. Thalberg; A.I. Markov, Cand. tech. sciences; R.O. Krasnovsky, Cand. tech. sciences; L.S. Pavlov, Cand. tech. sciences; M.Yu. Leshchinsky, Cand. tech. sciences; G.A. Tselykovsky; I.E. Shkolnik, Cand. tech. sciences; T.Yu. Lapenis, G.I. Weingarten, Cand. 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 by rebound, shock impulse, plastic deformation, shear, rib shear and shear-chipping.
The dimensions of the indentation on concrete (diameter, depth, etc.) or the ratio of the diameters of the indentations on the concrete and the standard specimen when the indenter is hit or the indenter is pressed into the concrete surface;
The value of the stress required for local destruction of concrete upon tearing off a metal disk glued to it, equal to the pull-off force divided by the projection area of the concrete tear-off surface onto the plane of the disc;
1.3. Mechanical methods of non-destructive testing are used to determine the strength of concrete of all types of rated strength, controlled in accordance with GOST 18105, as well as to determine the strength of concrete during inspection and rejection of structures.
1.4. The tests are carried out at a positive concrete temperature. 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 for at least one week at a positive temperature and a relative humidity of no more than 75%.
1.5. The assessment of the conformity of the values of the actual concrete strength 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.
| The name of the characteristics of the devices | Characteristics of instruments for the method | |||||
| elastic rebound | shock impulse | plastic deformation | detachment | 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 | 10 | |||||
| Conical indenter angle | 30-60 ° | |||||
| Indentation diameter,% of the indenter diameter | 20-70 | |||||
| Squareness tolerance when a load is applied at a height of 100 mm, mm |
||||||
| Impact energy, J, not less | 0,02 | |||||
| Load increase rate, kN / s | 1,5* | 0,5-1,5 | 0,5-1,5 | 1,5-3,0 | ||
| Load measurement error from measured load,%, no more | 5* | |||||
2.2. A tool for measuring the diameter or depth of indentations (angular scale in accordance with GOST 427, a caliper in accordance with GOST 166, etc.) used for the method of plastic deformation should provide measurements with an error of no more than ± 0.1 mm, and the instrument for measuring the depth of an indentation (indicator watch type according to GOST 577, etc.) - with an error of no more than ± 0.01 mm.
It is also allowed to use other anchoring devices, the embedment depth of which must not be less than the maximum size of the coarse concrete aggregate of the test structure.
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 of a diameter, with a roughness parameter of the glued surface of at least 20 microns in accordance with GOST 2789 should be used.
3.1. To determine the strength of concrete in structures, a calibration relationship is preliminarily established between the strength of concrete and an indirect characteristic of strength (in the form of a graph, table or formula).
For the method of separation with shearing, in the case of using anchor devices in accordance with Appendix 2, and for the method of shearing of the rib, in the case of using devices in accordance with Appendix 3, it is allowed to use the calibration dependences given in Appendices 5 and 6, respectively.
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 the 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 for 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 - in accordance with GOST 21243-75.
2. The strength of concrete is determined according to the previously established experimentally calibration relationships between the strength of concrete samples 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 the established non-destructive tests of those the same samples.
3. To construct 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 the methods of chipping the rib of the structure and tearing off.
Official edition Reprinting prohibited
Reissue. November 1981
© Standards Publishing House, 1982
Op. 10 GOST 22690.0-77
FORM OF THE JOURNAL FOR DETERMINING THE STRENGTH OF CONCRETE IN CONSTRUCTIONS
1. Test object ________
2. Test date _
3. The name of the structure (for prefabricated structures - brand, series of working drawings) _ „_
4. 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 changes, 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 test areas and the sample cut 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 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 error of the calibration dependence 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 one (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 results of the verification 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, then 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. 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 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 the formula (1), exceeds the permissible value of Tk, 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. 5
METHOD 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 the strength of concrete up to 200 kgf / cm 2 - linear:
with a range of fluctuations in concrete strength over 200 kgf / cm 2 exponential:
R- b 0 - / b, n. (2)
Coefficients about 0; ah b x are calculated by the formulas.
# 0 - R- (i \ '//, * (3)
"=‘ -CH? -Z-: (4)
2 (Hi-77) (In Ri-UiR)
| B n = c ^ - b "". |
The average values of strength R and indirect characteristics I, necessary to determine these coefficients, are calculated by the formulas:
* = Chg:< 7 >
In /? - = * "" s -; (nine)
The Ri and Hi values are, 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 assessment of the error of the calibration dependence is carried out in accordance with 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 the 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 * = 29). The average results for each series are shown in table. !.
Table 1
| Batch number |
H, division |
Serine number |
W, division |
R, kgf / cm " |
|
Since the measurement range of concrete strength 330-169 "=" 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: * = 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 dependence 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 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
| Series numbers 1 |
Sample numbers; | |
Test point numbers for |
/? , KGOSL1 * |
|||
Page 8 GOST 22690.0-77
Continuation
| 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 |
||||||
The standard 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.
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+...
YTSh-- "" 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, 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 average of the sample. To check the abnormality of this result, using the formula (1) of Mandatory Appendix 1, calculate the value
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