Determination of the strength of concrete by the method of elastic rebound. Determination of concrete strength by elastic rebound method GOST 22690 updated
The compressive strength of concrete is the main indicator that characterizes concrete.
There are two systems for expressing this indicator:
The compressive strength of concrete is the main indicator that characterizes concrete. It is on it that the non-destructive testing of the strength of concrete is oriented in monolithic structures. There are two systems for expressing this indicator:
- Concrete class, B is the so-called cubic strength (i.e., a compressible cube-shaped sample), showing the withstand pressure in MPa. The share of the probability of destruction during the concrete strength test does not exceed 5 units out of 100 tested samples. It is denoted by the Latin letter B and a number showing the strength in MPa. According to SNiP 2.03.01-84 "Concrete and reinforced concrete structures".
- Concrete grade, M - this is the compressive strength of concrete, kgf / cm². It is denoted by the Latin letter M and numbers from 50 to 1000. The maximum deviation that allows the control and assessment of the strength of concrete according to GOST 26633–91 “Concrete heavy and fine-grained is 13.5%.
The brand of concrete and the class are determined after 28 days from the date of pouring, under normal conditions, or the calculation is carried out taking into account the coefficient (after 7–14 days, the material acquires 60–80% of brand strength, after 28 days approximately 100%, after 90 days -130% .). The ultrasonic method of non-destructive testing of concrete is carried out, as a rule, at the intermediate and design age of the reinforced concrete structure.
The strength of concrete is affected by a number of factors: cement activity, cement content, water to cement ratio by weight, quality of aggregates, quality of mixing and degree of compaction, age and curing conditions of concrete, re-vibration. The rate of hardening of concrete is greatly influenced by the temperature and humidity of the environment. Conditionally normal is an environment with a temperature of 15–20 ° C and an air humidity of 90–100%. With an increase in the content of cement in concrete, its strength increases to a certain limit. Then it grows slightly, while other properties of concrete deteriorate: shrinkage and creep increase. Therefore, it is not recommended to introduce more than 600 kg of cement per 1 m³ of concrete.
Conformity of concrete grade (M) to class (B) and compressive strength
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Concrete brand, M |
Concrete class, B |
Strength, MPa |
Strength, kg / cm 2 |
Breakaway Method ranks among non-destructive methods for determining the strength of concrete special place. Considering non-destructive method, the shearing method is inherently a destructive method, since the strength of concrete is estimated by the force required to break a small volume of concrete, which allows the most accurate assessment of its actual strength. Therefore, this method is used not only to determine the strength of concrete of unknown composition, but can also be used to build calibration dependencies for other non-destructive testing methods. This method is applied to heavy concrete and structural concrete on light aggregates in monolithic and prefabricated concrete and reinforced concrete products, structures and structures and establishes a method for testing concrete and determining its compressive strength by local destruction of concrete when a special anchor device is pulled out of it. Such ultrasonic method of concrete strength control allows you to determine the compressive strength for concrete in the strength range from 5.0 to 100.0 MPa. When developing the standard, materials GOST 22690–88 were used.
One of the most common and effective ways non-destructive testing for determining the strength of concrete is a measurement with a sclerometer, or as it is also called, a Schmidt hammer.
Methods for determining the strength of concrete: equipment used
With the help of the devices presented below, it is possible to carry out non-destructive testing of concrete. This allows more accurate prediction physical characteristics ready-made reinforced concrete structures, which means minimizing the losses of the construction organization and protecting the customer from all sorts of troubles.
Among other things, this quality control of concrete allows testing of concrete, the temperature of which has dropped below 0ºС. Traditional Methods quality control of concrete in the laboratory cannot boast of such convenience: previously it was necessary to take a sample and check it during room temperature in laboratory conditions. Interesting modern solution also by the fact that contractors may not resort to the services of specialized organizations at each stage construction works. In turn, specialists can independently come to the site and conduct an examination of the quality of concrete in accordance with GOST standards. The equipment is quite compact and mobile, and the preparation of results takes a minimum of time.
Used equipment
Schmidt hammer Original Schmidt type N
Testing of concrete products using the Schmidt hammer Original Schmidt is the most common worldwide measurement technique that does not destroy concrete in accordance with GOST 22690-2015
Proceq offers the appropriate hammer model for each concrete testing application.
Schmidt hammer models are available for testing concrete products of the Original Schmidt type with different impact energies for testing materials of various types and sizes.
Our N, NR, L and LR type hammers are specifically designed to assess the quality and compressive strength of concrete products with a range of 10 to 70 N/mm2 (1,450 to 10,152 psi).
Models with built-in paper recorders (LR and NR) are capable of automatically recording rebound values on paper tape.
SI Type Approval Certificate Brochure Schmidt Hammers
POS-50MG4 "Skol" is designed for non-destructive testing of concrete strength by methods of rib chipping, tearing with chipping and tearing of steel disks according to GOST 22690-2015.
Measuring the strength of concrete using such equipment is allowed both on projects under construction and on finished buildings. The device is indispensable in the construction industry, in the work of public utilities and restoration bureaus, which periodically check the integrity of buildings. Model received non-volatile memory, which stores the last two hundred measurements. They are marked with the brand of concrete and the exact date of the analysis, allowing specialists to easily track the dynamics of changes in key indicators.
V.A. Klevtsov, Doctor of Engineering sciences (topic leader); M.G. Korevitskaya, Ph.D. tech. sciences; Yu.K.Matveev; V.N. Artamonova; N.S. Vostrova; A.A. Grebenik; G.V. Sizov, Ph.D. tech. sciences; D.A. Korshunov, Ph.D. tech. sciences; M.V. Sidorenko, Ph.D. tech. sciences; Yu.I.Kurash, Ph.D. tech. sciences; A.M. Leshchinsky, Ph.D. tech. sciences; V.R. Abramovsky; V.A.Dorf, Ph.D. tech. sciences; E.G. Sorkin, Ph.D. tech. sciences; V.L. Chernyakhovsky, Ph.D. tech. sciences; I.O. Krol, Ph.D. tech. sciences; S.Ya.Khomutchenko; Ya.E.Ganin; O.Yu.Sammal, Ph.D. tech. sciences; A.A. Rulkov, Ph.D. tech. sciences; P.L. Talberg; A.I.Markov, Ph.D. tech. sciences; R.O. Krasnovsky, Ph.D. tech. sciences; L.S. Pavlov, Ph.D. tech. sciences; M.Yu. Leshchinsky, Ph.D. tech. sciences; G.A. Tselykovsky; I.E. Shkolnik, Ph.D. tech. sciences; T.Yu.Lapenis, G.I. Weingarten, Ph.D. tech. sciences; N.B. Zhukovskaya; S.P. Abramova; I.N. Nagornyak
This International Standard is applicable to heavy and lightweight concrete and specifies methods for determining the compressive strength of structures in terms of rebound, impact impulse, plastic deformation, peeling, rib shearing, and shearing with shearing.
Dimensions of the imprint on concrete (diameter, depth, etc.) or the ratio of the diameters of imprints on concrete and a standard sample when the indenter is struck or the indenter is pressed into the concrete surface;
The value of the stress required for the local destruction of concrete when a metal disk glued to it is torn off, equal to the tear force divided by the area of the projection of the concrete torn-off surface onto the disk plane;
1.3. Mechanical methods of non-destructive testing are used to determine the strength of concrete of all types of normalized strength, controlled in accordance with GOST 18105, as well as to determine the strength of concrete during examination and rejection of structures.
1.4. Tests are carried out at a positive temperature of concrete. When examining structures, it is allowed to determine the strength at negative temperature, but not lower than minus 10 °C, provided that by the time of freezing, the structure had been at a positive temperature for at least one week and the relative humidity of the air was not more than 75%.
1.5. The assessment of the conformity of the values of the actual strength of concrete, obtained using the methods given in this standard to the established requirements, is carried out in accordance with GOST 18105.
2.1. The strength of concrete is determined using instruments designed to determine indirect characteristics that have passed metrological certification in accordance with GOST 8.326* and meet the requirements given in Table 2.
| Name of characteristics of devices | Characteristics of devices for the method | |||||
| elastic rebound | shock impulse | plastic deformation | separation | chipping ribs | breakaway with chipping | |
| Hardness of striker, striker or indenter HRCe, not less than | ||||||
| Roughness of the contact part of the striker or indenter, µm, not more than | ||||||
| Impactor or indenter diameter, mm, not less than | ||||||
| Thickness of disk indenter edges, mm, not less than | 10 | |||||
| Conical indenter angle | 30-60° | |||||
| Indentation diameter, % of indenter diameter | 20-70 | |||||
| Perpendicularity tolerance when applying a load at a height of 100 mm, mm |
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| Impact energy, J, not less than | 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 the 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 plastic deformation method must provide measurements with an error of no more than ±0.1 mm, and a tool for measuring the indentation depth (indicator clock type according to GOST 577, etc.) - with an error of not more than ± 0.01 mm.
It is also allowed to use other anchor devices, the insertion depth of which should not be less than the maximum size of the coarse concrete aggregate of the structure being tested.
2.5. For the tear-off method, steel discs with a diameter of at least 40 mm, a thickness of at least 6 mm and at least 0.1 diameter, with a roughness parameter of the glued surface of at least 20 microns in accordance with GOST 2789, should be used. The adhesive for gluing the disc must provide strength at which
3.1. To determine the strength of concrete in structures, a calibration relationship is first established between the strength of concrete and an indirect characteristic of strength (in the form of a graph, table or formula).
For the shearing method, in case of using anchor devices in accordance with Appendix 2, and for the rib shearing method, in case of using devices in accordance with Appendix 3, it is allowed to use the calibration dependences given in Appendixes 5 and 6, respectively.
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 the development, adoption, application, updating and cancellation "
1 DEVELOPED by the Structural Subdivision of JSC "NIC "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 No. 47)
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Short country name |
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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 |
State Standard of the Republic of Kazakhstan |
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Kyrgyzstan |
Kyrgyzstandart |
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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 the 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 the strength of concrete 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-outforce
Degree of conformity - 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 - 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, notification 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
Introduction date - 2016-04-01
1 area of use
This standard applies to structural heavy, fine-grained, light and tension concrete of monolithic, prefabricated 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, separation, rib shearing and separation with shearing.
2 Normative references
This standard uses normative references to the following interstate standards:
Note - Standard test schemes are applicable in a limited range of concrete strengths (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 manufacturers of specific measuring instruments. The use of methods outside the concrete strength ranges recommended in the table is allowed with scientific and technical justification based on the results of studies using measuring instruments that have passed metrological certification for an extended concrete strength range.
Table 1
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Method name |
Limit values of concrete strength, MPa |
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Elastic rebound and plastic deformation |
5 - 50 |
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shock impulse |
5 - 150 |
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Separation |
5 - 60 |
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Rib chipping |
10 - 70 |
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Breakaway with chipping |
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 sections of structures that do not have visible damage (peeling of the protective layer, cracks, cavities, etc.).
4.9 The age of concrete of controlled structures and its sections should not differ from the age of concrete of structures (sections, samples) tested to establish calibration dependence, by more than 25%. The exceptions are the control of strength and the construction of a calibration dependence for concrete whose age exceeds two months. In this case, the age difference individual structures(plots, samples) is not regulated.
4.10 Tests are carried out at a positive temperature of concrete. It is allowed to conduct tests at a negative temperature of concrete, but not lower than minus 10 ° C, when establishing or linking the calibration dependence, taking into account the requirements. The temperature of the concrete during testing must correspond to the temperature provided for by the operating conditions of the devices.
Calibration dependencies established at a concrete temperature below 0 °C are not allowed to be used at positive temperatures.
4.11 If it is necessary to test concrete structures after heat treatment at surface temperature T≥ 40 °C (to control the tempering, transfer and stripping strength of concrete) the calibration dependence is established after determining the strength of concrete in the structure by an indirect non-destructive method at a temperature t = (T± 10) °C, and testing of concrete by a direct non-destructive method or testing of samples - after cooling at normal temperature.
5 Measuring instruments, equipment and tools
5.1 Measuring instruments and devices for mechanical testing, designed to determine the strength of concrete, must be certified and verified in in due course and must meet the application requirements.
5.2 Readings of instruments calibrated in units of concrete strength should be considered as an indirect indicator of concrete strength. These devices should be used only after establishing the calibration dependence "instrument reading - concrete strength" or linking the dependence set in the device in accordance with.
5.3 A tool for measuring the diameter of indentations (caliper according to GOST 166) used for the plastic deformation method must provide measurement with an error of not more than 0.1 mm, a tool for measuring the depth of an indentation (caliper type according to GOST 577, etc.) - with an error no more than 0.01 mm.
5.4 Standard schemes for testing the method of tearing with shearing and chipping of the rib provide for the use of anchor devices and grips in accordance with the applications and.
5.5 For the shear pull method, anchor devices should be used, the insertion depth of which should not be less than the maximum size of the coarse concrete aggregate of the structure being tested.
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 a roughness of the bonded surface of at least Ra\u003d 20 microns according to GOST 2789. Adhesive for gluing the disk must provide the strength of adhesion to concrete, at which the 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 calibration dependencies between the concrete strength and the indirect strength characteristic.
6.1.2 The calibration dependence is established on the basis of the following data:
The results of parallel tests of the same sections of structures by one of the indirect methods and the direct non-destructive method for determining the strength of concrete;
The results of testing sections of structures by one of the indirect non-destructive methods for determining the strength of concrete and testing core samples taken from the same sections of the structure and tested in accordance with GOST 28570;
The results of testing standard concrete samples by one of the indirect non-destructive methods for determining the strength of concrete and mechanical tests in accordance with GOST 10180.
6.1.3 For indirect non-destructive methods for determining the strength of concrete, the calibration dependence is established for each type of normalized strength specified in for concretes of the same nominal composition.
It is allowed to build one calibration dependence for concrete of the same type with one type of coarse aggregate, with a single production technology, differing in nominal composition and normalized strength value, subject to the requirements.
6.1.4 The allowable difference in the age of concrete of individual structures (sections, samples) when establishing a calibration dependence on the age of concrete of a controlled structure is taken according to .
6.1.5 For direct non-destructive methods, it is allowed to use the dependencies given in the appendices and for all types of standardized concrete strength.
6.1.6 The calibration dependence must have a standard (residual) deviation S T . H. M, not exceeding 15% of the average strength of concrete sections or samples used in the construction of the dependence, and the correlation coefficient (index) is not less than 0.7.
It is recommended to use a linear dependence of the form R = a + bK(where R- concrete strength, K is an indirect indicator). The methodology for establishing, estimating parameters and determining the conditions for applying a linear calibration dependence is given in the Appendix.
6.1.7 When constructing the calibration dependence of the deviation of individual values of concrete strength R i f from the average value of the concrete strength of the sections or samples used to build the calibration dependence should be within:
From 0.5 to 1.5 average concrete strength at ≤ 20 MPa;
From 0.6 to 1.4 average concrete strength at 20 MPa< ≤ 50 МПа;
From 0.7 to 1.3 average concrete strength at 50 MPa< ≤ 80 МПа;
From 0.8 to 1.2 average concrete strength at > 80 MPa.
6.1.8 Correction of the established dependence for concretes of intermediate and design age should be carried out at least once a month, taking into account additionally obtained test results. The number of samples or areas of additional tests during the adjustment should be at least three. The correction procedure is given in the appendix.
6.1.9 It is allowed to use indirect non-destructive methods for determining the strength of concrete, using calibration dependencies established for concrete that differs from the tested one in composition, age, hardening conditions, humidity, with reference in accordance with the application procedure.
6.1.10 Without reference to specific conditions for the application, the calibration dependencies established for concrete that differs from the test one can only be used to obtain approximate strength values. It is not allowed to use approximate strength values without reference to specific conditions to assess the strength class of concrete.
Then, sites are selected in the amount provided for, on which the maximum, minimum and intermediate values of the indirect indicator are obtained.
After testing by an indirect non-destructive method, the sections are tested by a direct non-destructive method or samples are taken for testing in accordance with GOST 28570.
6.2.4 To determine the strength at a negative temperature of concrete, the sections selected for building or linking the calibration dependence are first tested by an indirect non-destructive method, and then samples are taken for subsequent testing at a positive temperature or heated by external heat sources (infrared emitters, heat guns etc.) to a depth of 50 mm to a temperature not lower than 0 °C and tested by a direct non-destructive method. The temperature control of the heated concrete is carried out at the installation depth of the anchor device in the prepared hole or along the chip surface in a non-contact way using a pyrometer according to GOST 28243.
Rejection of the test results used to build the calibration dependence at a negative temperature is allowed only if the deviations are associated with a violation of the test procedure. In this case, the rejected result should be replaced by the results of a repeated test in the same area of the structure.
6.3.1 When constructing a calibration dependence on control samples, the dependence is established by single values of the indirect indicator and concrete strength of standard cube samples.
For a single value of the indirect indicator, the average value of the indirect indicators for a series of samples or for one sample (if the calibration dependence is established for individual samples) is taken. For a single value of the strength of concrete, the strength of concrete in a series according to GOST 10180 or one sample (calibration dependence for individual samples) is taken. Mechanical Tests samples according to 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 results of testing sample cubes, at least 15 series of sample cubes according to GOST 10180 or at least 30 individual sample cubes are used. Samples are made in accordance with the requirements of GOST 10180 in different shifts, for at least 3 days, from concrete of the same nominal composition, according to the same technology, with the same hardening mode as the structure to be controlled.
The unit values of the concrete strength of the sample cubes used to build the calibration dependence must correspond to the deviations expected in production, while being within the ranges established in.
6.3.3 The calibration dependence for the methods of elastic rebound, shock impulse, plastic deformation, separation and chipping of the rib is established on the basis of the results of testing the manufactured sample cubes, first by the non-destructive method, and then by the destructive method in accordance with GOST 10180.
When establishing a calibration dependence for the method of separation with shearing, 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 from the same concrete and cured under the same conditions.
6.3.4 The dimensions of the samples should be selected in accordance with the largest aggregate size in concrete mix according to GOST 10180, but not less than:
100×100×100 mm for the methods of rebound, impact impulse, plastic deformation, as well as for the method of separation with chipping (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 anchor device installation depths for the pull-off method with shearing (basic samples).
6.3.5 To determine the indirect characteristics of strength, tests are carried out according to the requirements of the section on the side (in the direction of concreting) faces of the sample cubes.
The total number of measurements on each sample for the method of elastic rebound, shock impulse, plastic deformation upon impact must be at least the established number of tests on the site according to the table, and the distance between the impact points must be at least 30 mm (15 mm for the shock impulse method). For the indentation plastic deformation method, the number of tests on each face must be at least two, and the distance between the test points must be at least two indent diameters.
When establishing a calibration dependence for the rib shearing method, one test is carried out on each side rib.
When establishing the calibration dependence for the method of separation with shearing, one test is carried out on each side face of the main sample.
6.3.6 When tested by the method of elastic rebound, shock impulse, plastic deformation upon impact, the specimens shall be clamped in a press with a force of not less than (30 ± 5) kN and not more than 10% of the expected value of the breaking load.
6.3.7 The samples tested by the pull-off method are installed on the press so that the surfaces on which the pull-out was carried out do not adjoin the press base plates. The test results according to GOST 10180 are increased by 5%.
7 Testing
7.1.1 The number and location of controlled sections in structures must comply with the requirements of GOST 18105 and be indicated in project documentation on the structure or installed taking into account:
Control tasks (definition actual class concrete, stripping or tempering strength, identification of areas of reduced strength, etc.);
Type of construction (columns, beams, slabs, etc.);
Placement of grips and order of concreting;
Structural reinforcement.
The rules for assigning the number of test sites for monolithic and prefabricated structures in the control of concrete strength are given in the appendix. When determining the strength of concrete of the examined structures, the number and location of sections should be taken according to the program of the survey.
7.1.2 Tests are 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 not be less than the values \u200b\u200bgiven 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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elastic rebound |
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shock impulse |
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Plastic deformation |
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Rib chipping |
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Separation |
2 diameters |
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Breakaway with shearing at the working depth of the anchorh: |
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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%. The results of measurements that do not meet the specified condition are not taken into account when calculating the arithmetic mean of the indirect indicator for this area. The total number of measurements in each section when calculating the arithmetic mean must comply with the requirements of 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 section, provided that the calculated value of the indirect indicator is within the established (or tied) dependence (between the lowest and highest strength values ).
7.1.6 The surface roughness of the structure concrete section when tested by the methods of rebound, impact impulse, plastic deformation should correspond to the surface roughness of the structure sections (or cubes) tested when establishing the calibration dependence. In necessary cases, it is allowed to clean the surfaces of the structure.
When using the indentation plastic deformation method, if the zero reading is taken after the application of the initial load, there are no requirements for the roughness of the concrete surface of the structure.
7.2.1 Tests are carried out in the following sequence:
The position of the device when testing the structure relative to the horizontal is recommended to be taken the same as when establishing the calibration dependence. In a different position of the device, it is necessary to make a correction for the indicators in accordance with the instruction manual for the device;
7.3.1 Tests are carried out in the following sequence:
The device is positioned so that the force is applied perpendicular to the surface under test in accordance with the instructions for use of the device;
When using a spherical indenter, to facilitate measurements of the 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);
Fix the values of the indirect characteristic in accordance with the instruction manual for the device;
Calculate the average value of the indirect characteristic on the construction site.
7.4.1 Tests are carried out in the following sequence:
The device is positioned so that the force is applied perpendicular to the surface under test in accordance with the instructions for use of the device;
The position of the device when testing the structure relative to the horizontal is recommended to be taken the same as when testing when establishing the calibration dependence. In a different position of the device, it is necessary to make a correction for the readings in accordance with the instruction manual for the device;
The value of the indirect characteristic is fixed in accordance with the instruction manual for the device;
Calculate the average value of the indirect characteristic on the construction site.
7.5.1 When testing by the pull-off method, the sections should be located in the zone of the lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.
7.5.2 The test is carried out in the following sequence:
At the place where the disk is glued, the surface layer of concrete is removed with a depth of 0.5 - 1 mm and the surface is cleaned of dust;
The disk is glued to the concrete by pressing the disk and removing excess adhesive outside the disk;
The device is connected to the disk;
The load is smoothly increased at a rate of (1 ± 0.3) kN/s;
The area of the projection of the separation surface on the plane of the disk is measured with an error of ± 0.5 cm 2;
The value of the conditional stress in concrete at separation is determined as the ratio of the maximum force of separation to the projection area of the separation surface.
7.5.3 The test results are not taken into account if the reinforcement was exposed during the detachment of concrete or the projection area of the detachment surface was less than 80% of the disk area.
7.6.1 When testing by the pull-off method with shearing, the sections should be located in the zone of the lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.
7.6.2 Tests are carried out in the following sequence:
If the anchor device was not installed before concreting, then a hole is made in the concrete, the size of which is chosen in accordance with the device operating instructions, depending on the type of anchor device;
An anchor device is fixed in the hole to the depth provided for in the instruction manual for the device, depending on the type of anchor device;
The device is connected to the anchor device;
The load is increased at a rate of 1.5 - 3.0 kN / s;
Fix the reading of the force meter of the device R 0 and anchor slippage Δ h(difference between the actual depth of the pull-out and the depth of the anchoring device) with an accuracy of at least 0.1 mm.
7.6.3 Measured pull-out force R 0 is multiplied by the correction factor γ, determined by the formula
where h- working depth of the anchor device, mm;
Δ h- anchor slippage, mm.
7.6.4 If the largest and smallest dimensions of the torn-out part of the concrete from the anchor device to the boundaries of destruction on the surface of the structure differ by more than two times, and also, if the depth of the torn-out differs from the depth of embedding of the anchor device by more than 5% (Δ h > 0,05h, γ > 1.1), then the test results can only be taken into account for an approximate assessment of the strength of concrete.
Note - Approximate values of the strength of concrete are not allowed to be used to assess the class of concrete in terms of strength and build calibration dependencies.
7.6.5 The test results are not taken into account if the pull-out depth differs from the depth of the anchoring device by more than 10% (Δ h > 0,1h) or the reinforcement was exposed at a distance from the anchor device, less than the depth of its embedding.
7.7.1 When testing by the rib shearing method, there should be no cracks, concrete rims, sags or shells with a height (depth) of more than 5 mm in the test area. The sections should be located in the zone of the least stresses caused by the operational load or the compression force of the prestressed reinforcement.
7.7.2 The test is carried out in the following sequence:
The device is fixed on the structure, load is applied at a speed of not more than (1 ± 0.3) kN / s;
Record the reading of the force meter of the device;
Measure the actual depth of chipping;
Determine the average value of the chipping force.
7.7.3 The test results are not taken into account if the reinforcement was exposed during concrete shearing or the actual shearing depth differed from the specified one by more than 2 mm.
8 Processing and presentation of results
8.1 The test results are presented in a table indicating:
Type of construction;
Design class of concrete;
Age of concrete;
The strength of the concrete of each controlled area according to ;
The average strength of the concrete structure;
Zones of the structure or its parts, subject to the requirements.
The form of the test results presentation table is given in the appendix.
8.2 Processing and assessment of compliance with the established requirements of the values of the actual strength of concrete, obtained using the methods given in this standard, is carried out in accordance with GOST 18105.
Note - Statistical evaluation concrete class according to 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 constructed in accordance with section . When using previously installed dependencies by linking them (by application ) statistical control is not allowed, and the assessment of the concrete class is carried out only according to the "G" scheme GOST 18105.
8.3 The results of determining the strength of concrete by mechanical methods of non-destructive testing are drawn up in a conclusion (protocol), in which the following data are given:
About the tested structures indicating the design class, the date of concreting and testing, or the age of concrete at the time of testing;
On the methods used to control the strength of concrete;
About the types of devices with serial numbers, information about the verification of devices;
On the accepted calibration dependences (dependence equation, dependence parameters, compliance with the conditions for applying the calibration dependence);
Used to build a calibration dependence or its binding (date and results of tests by non-destructive indirect and direct or destructive methods, correction factors);
On the number of sites for determining the strength of concrete in structures, indicating their location;
Test results;
Methodology, results of processing and evaluation of the obtained data.
Annex A
(mandatory)
Standard Shear-Pull Test Design
A.1 The standard shearing test scheme provides for tests subject to the requirements - .
A.2 The standard test scheme is applicable in the following cases:
Tests of heavy concrete with compressive strength from 5 to 100 MPa;
Tests of lightweight concrete with compressive strength from 5 to 40 MPa;
The maximum fraction of coarse concrete aggregate is not more than the working depth of anchor devices.
A.3 The supports of the loading device should evenly adjoin the concrete surface at a distance of at least 2 h from the axis of the anchor device, where h- working depth of the anchor device. The test scheme is shown in the figure.
1
2
- support of the loading device;
3
- capture of the loading device; 4
- transitional elements, traction; 5
- anchor device;
6
- tear-out concrete (separation cone); 7
- test design
Figure A.1 — Schematic of the pull-out and shear test
A.4 The standard shearing test scheme provides for the use of three types of anchor devices (see Figure ). Anchor device type I is installed in the structure during concreting. Anchor devices of types II and III are installed in holes previously prepared in the structure.
1
- working rod; 2
- working rod with expanding cone; 3
- segmented corrugated cheeks;
4
- support rod; 5
- working rod with a hollow expansion cone; 6
- leveling washer
Figure A.2 — Types of anchor devices for a standard test scheme
A.5 The parameters of anchor devices and the ranges of measured concrete strength for them under the standard test scheme are indicated in the table. For lightweight concrete, in the standard test scheme, only anchor devices with a embedment depth of 48 mm are used.
Table A.1 - Parameters of anchor devices for a standard test scheme
|
Anchor type |
Anchor diameter |
Depth of embedding of anchor devices, |
Acceptable for anchor device |
||
|
working h |
complete h" |
severe |
lung |
||
|
45 - 75 |
|||||
|
10 - 50 |
10 - 40 |
||||
|
40 - 100 |
|||||
|
5 - 100 |
5 - 40 |
||||
|
10 - 50 |
|||||
A.6 Anchor designs of types II and III should provide preliminary (before applying the load) compression of the hole walls at the working depth of embedding h and slip control after testing.
Annex B
(mandatory)
Standard Rib Shearing Test Arrangement
B.1 The standard rib shearing test scheme provides for testing subject to the requirements -.
B.2 The standard test scheme is applicable in the following cases:
The maximum fraction of coarse concrete aggregate is not more than 40 mm;
Tests of heavy concrete with compressive strength from 10 to 70 MPa on crushed granite and limestone.
B.3 For testing, a device is used, consisting of a power exciter with a force measuring unit and a gripper with a bracket for local shearing of the structure rib. The test scheme is shown in the figure.
1
- a device with a loading device and a force meter; 2
- support frame;
3
- chipped concrete; 4
- test design; 5
- grip with bracket
Figure B.1 - Schematic of the rib shear test
B.4 In case of local shearing of the rib, the following parameters should be provided:
chipping depth a= (20 ± 2) mm;
Cleave Width b= (30 ± 0.5) mm;
The angle between the direction of the load and the normal to the loaded surface of the structure β = (18 ± 1)°.
Annex B
(recommended)
Calibration dependence for the method of separation with shearing
When carrying out tests by the method of separation with shearing 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 coarse aggregate in the pull-out zone, taken equal to 1 with aggregate size less than 50 mm;
m 2 - coefficient of proportionality for the transition from pulling out force in 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 |
Anchor embedment depth |
Coefficient valuem 2 for concrete |
|
|
severe |
lung |
||||
|
45 - 75 |
|||||
|
10 - 50 |
|||||
|
40 - 75 |
|||||
|
5 - 75 |
|||||
|
10 - 50 |
|||||
Odds m 2 when testing heavy concrete with an average strength above 70 MPa should be taken according to GOST 31914.
Annex D
(recommended)
Calibration dependence for the rib shearing method
with a standard test scheme
When performing a rib shearing test according to the standard scheme according to the appendix, the cubic compressive strength of concrete on granite and lime 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 coarse aggregate and taken equal to:
1.0 - with aggregate size less than 20 mm;
1.05 - with aggregate size from 20 to 30 mm;
1.1 - with aggregate size from 30 to 40 mm;
R- chipping force, kN.
Annex D
(mandatory)
Requirements for instruments for mechanical testing
Table E.1
|
Name of characteristics of devices |
Characteristics of devices for the method |
|||||||||||||||||||||||||||||||||||||
|
elastic |
shock |
plastic |
separation |
chipping |
separation from |
|||||||||||||||||||||||||||||||||
|
Hardness of striker, striker or indenter HRCe, not less than |
||||||||||||||||||||||||||||||||||||||
|
Roughness of the contact part of the striker or indenter, µm, not more than |
||||||||||||||||||||||||||||||||||||||
|
Impactor or indenter diameter, mm, not less than |
||||||||||||||||||||||||||||||||||||||
|
Thickness of disk indenter edges, mm, not less than |
||||||||||||||||||||||||||||||||||||||
|
Conical indenter angle |
30° - 60° |
|||||||||||||||||||||||||||||||||||||
|
Indentation diameter, % of indenter diameter |
20 - 70 |
|||||||||||||||||||||||||||||||||||||
|
Perpendicularity tolerance when applying a load at a height of 100 mm, mm |
||||||||||||||||||||||||||||||||||||||
|
Impact energy, J, not less than |
0,02 |
|||||||||||||||||||||||||||||||||||||
|
Load increase rate, kN/s The equation of dependence "indirect characteristic - strength" is assumed to be linear according to 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 values R i H R i f, , N- see explanations for formulas (), (). E.4 Correction of the calibration dependence Adjustment of the established calibration dependence, taking into account 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 indirect indicator. As data is accumulated 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 value indirect characteristic, the calibration dependence and its parameters are set again according to the formulas () - (). E.5 Conditions for applying the calibration dependence The use of a calibration dependence to determine the strength of concrete according to this standard is allowed only for values of an indirect characteristic falling in the range from H min up to H max. If the correlation coefficient r < 0,7 или значение Annex G
| ||||||||||||||||||||||||||||||||||||||
|
|
where R os i- strength of concrete i-th section, determined by the method of separation with chipping or testing of cores in accordance with GOST 28570;
R cosv i- strength of concrete i-th section, determined by any indirect method according to the calibration dependence used;
n- number of test sites.
G.2 When calculating the coefficient of coincidence, the following conditions must be met:
The number of test sites taken into account when calculating the coefficient of coincidence, n ≥ 3;
Each private value R os i /R cosv i must be at least 0.7 and not more than 1.3:
|
1 per 4 m length of linear structures; 1 by 4 m 2 area of flat structures. Annex K
| |||||||||||||||||||||||||||||||||
|
Name of structures |
Designation 1) |
Site number according to the scheme |
Strength of concrete, MPa |
Strength class |
|
|
plot 3) |
medium 4 ) |
||||
|
1) brand, symbol and (or) the location of the structure in the axes, the zone of the structure, or part of the monolithic and precast-monolithic structure (grip), for which the concrete strength class is determined. 2) The total number and location of plots in accordance with . 3) The strength of the concrete area in accordance with . 4) The average strength of the concrete of a structure, a zone of a structure or a part of a monolithic and prefabricated monolithic construction with the number of sites 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 paragraphs 7.3 - 7.5 GOST 18105 depending on the selected control scheme. Note - Presentation in the column "Concrete strength class" of the estimated values of the class or values of the required concrete strength for each section separately (estimation of the strength class for one section) is not allowed. |
|||||
Key words: structural heavy and light concretes, monolithic and prefabricated concrete and reinforced concrete products, structures and structures, mechanical methods for determining compressive strength, elastic rebound, shock impulse, plastic deformation, separation, rib shearing, separation with shearing
INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION
INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION
INTERSTATE
STANDARD
CONCRETE
Determination of strength by mechanical methods of non-destructive testing
(EN 12504-2:2001, NEQ)
(EN 12504-3:2005, NEQ)
Official edition
Stand rtinform 2016
Foreword
The goals, basic principles and basic procedure for carrying out work on the interstate camp, darting 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 the development, adoption, application, updating and cancellation "
About the standard
1 DEVELOPED by the Structural Subdivision of JSC "NIC "Construction" Research. Design and Technological Institute of Concrete and Reinforced Concrete. 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 No. 47)
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 Russian Federation since April 1, 2016
5 8 this standard takes into account the main regulatory provisions regarding the requirements for mechanical methods of non-destructive testing of the strength of concrete 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 conformity - non-equivalent (NEQ)
6 83AMEN GOST 22690-88
Information about changes to this standard is published in the annual information index "National Standards", and the text of changes and amendments - 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, notification 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
© Standartinform. 2016
In the Russian Federation, this standard may not be fully or partially reproduced. replicated and distributed as an official publication without the permission of the Federal Agency for Technical Regulation and Metrology
Annex A (normative) Standard scheme for the pull-and-shear test. . . 10
INTERSTATE STANDARD
Determination of strength mechanical methods non-destructive testing
Determination of strength by mechanical methods of nondestructive testing
Introduction date - 2016-04-01
1 area of use
This standard applies to structural heavy, fine-grained, light and tension concrete 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, separation, chipping of the rib and tearing with chipping.
8 of this standard, normative references to the following interstate standards are used:
GOST 166-89 (ISO 3599-76) Calipers. Specifications
GOST 577-68 Clock-type indicators with a division stage of 0.01 mm. Specifications
GOST 2789-73 Surface roughness. Parameters and characteristics
GOST 10180-2012 Concrete. Methods for determining the strength of control samples
GOST 18105-2010 Concrete. Strength control and assessment rules
GOST 28243-96 Pyrometers. General technical requirements
GOST 28570-90 Concrete. Methods for determining strength from samples taken from structures
GOST 31914-2012 High-strength heavy and fine-grained concrete for monolithic structures. Rules for quality control and assessment
Note - When using this standard, it is advisable to check the validity of reference standards in the public information system - not 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 on issues of the monthly information index "National Standards" for this year. If the reference standard is replaced (modified), then when using this standard, you should be guided by the replacing (modified) standard. If the referenced standard is canceled without replacement, the provision in which the reference to it is given applies to the extent that this reference is not affected.
3 Terms and definitions
8 of this standard, the terms are used in accordance with GOST 18105. as well as the following terms with the corresponding definitions:
Official edition
destructive methods for determining the strength of concrete: Determination of the strength of concrete according to control samples made from a concrete mix according to GOST 10180 or selected from structures according to GOST 28570.
[GOST 18105-2010. article 3.1.18]
3.2 non-destructive mechanical methods for determining the strength of concrete: Determination of the strength of concrete directly in the structure under local mechanical action on concrete (impact, separation, chipping, indentation, separation with chipping, elastic rebound).
3.3 indirect non-erosion methods for determining the strength of concrete: Determination of the strength of concrete according to pre-established calibration dependencies.
3.4 direct (standard) non-destructive methods for determining concrete strength
3.5 calibration dependence: Graphical or analytical dependence between the indirect strength characteristic and the compressive strength of concrete, determined by one of the destructive or direct non-destructive methods.
3.6 indirect characteristics of strength (indirect indicator): The amount of force applied during local destruction of concrete, the amount of rebound, impact energy, imprint size or other indication of the device when measuring the strength of concrete by non-destructive mechanical methods.
4 General provisions
4.1 Non-destructive mechanical methods are used to determine the compressive strength of concrete at the intermediate and design age established by the design documentation and at an age exceeding the design age when examining structures.
4.2 Non-destructive mechanical methods for determining the strength of concrete, established by this standard, are divided according to the type of mechanical action or indirect characteristic determined by the method:
Elastic rebound;
plastic deformation;
> shock impulse:
Breakaway with chipping:
Rib chipping.
4.3 Non-erosion mechanical methods for determining the strength of concrete are based on the relationship between the strength of concrete and indirect strength characteristics:
The method of elastic rebound on the relationship between the strength of concrete and the value of the rebound of the striker from the surface of the concrete (or the striker pressed against it);
The method of plastic deformation in relation to the strength of concrete with the dimensions of the imprint on the concrete of the structure (diameter, depth, etc.) or the ratio of the diameter of the imprint on concrete and a standard metal sample when the indenter is struck or the indenter is pressed into the concrete surface;
Impact impulse method on the relationship between the strength of concrete and the energy of impact and its changes at the moment of impact of the striker with the concrete surface;
The method of tearing off the stress bond required for local destruction of concrete when a metal disk glued to it is pulled off, equal to the tearing force divided by the area of the projection of the concrete tearing surface onto the plane of the disk;
Method of detachment with shearing on the connection of the strength of concrete with the value of the force of local destruction of concrete when the anchor device is excavated from it;
Rib shearing method on the relationship of concrete strength with the value of the force required to shear a section of concrete on a structure edge.
4.4 In general, non-destructive mechanical methods for determining the strength of concrete are indirect non-destructive methods for determining strength. The strength of concrete in structures is determined by experimentally established calibration dependencies.
4.5 The tear-off method with shearing during testing in accordance with the standard scheme in Appendix A and the method of rib shearing during testing in accordance with the standard scheme in Appendix B are direct non-destructive methods for determining the strength of concrete. For direct non-destructive methods, it is allowed to use the calibration dependences established in Appendixes b and D.
Note - Standard test schemes are applicable for a limited range of concrete strength (see Annexes A and B). For cases not related to standard test schemes, calibration dependencies should be established according to general rules.
4.6 The test method should be selected taking into account the data given in Table 1. and additional restrictions established by manufacturers of specific measuring instruments. The use of methods outside the concrete strength ranges recommended in Table 1 is allowed with scientific and technical justification based on the results of studies using measuring instruments that have passed metrological certification for an extended concrete strength range.
Table 1
4.7 Determination of the strength of heavy concrete of design classes B60 and above or with an average compressive strength of concrete R m i 70 MPa in monolithic structures must be carried out taking into account the provisions of GOST 31914.
4.8 The strength of concrete is determined in sections of structures that do not have visible damage (peeling of the protective layer, cracks, cavities, etc.).
4.9 The age of concrete of controlled structures and its sections should not differ from the age of concrete of structures (sections, samples) tested to establish a calibration dependence by more than 25%. The exceptions are the control of strength and the construction of a calibration dependence for concrete whose age exceeds two months. In this case, the difference in the age of individual structures (sections, samples) is not regulated.
4.10 Tests are carried out at a positive temperature of concrete. It is allowed to conduct tests at a negative temperature of concrete, but not lower than minus 10 "C, when establishing or linking a calibration dependence taking into account the requirements of 6.2.4. The temperature of the concrete during testing must correspond to the temperature provided for by the operating conditions of the devices.
Calibration dependencies established at a concrete temperature below 0 * C are not allowed to be used at positive temperatures.
4.11 If it is necessary to test concrete structures after heat treatment at a surface temperature of T to 40 * C (to control the tempering, transfer and stripping strength of concrete), the calibration dependence is established after determining the strength of concrete in the structure by an indirect non-destructive method at a temperature (t (T ± 10) *C, and testing of concrete by a direct non-destructive method or testing of samples - after cooling at normal temperature.
5 Measuring instruments, equipment and tools
5.1 Measuring instruments and devices for mechanical testing, designed to determine the strength of concrete, must be certified and verified in the prescribed manner and must comply with the requirements of Appendix D.
5.2 Readings of instruments calibrated in units of concrete strength should be considered as an indirect indicator of concrete strength. These devices should only be used after
establishing a calibration dependence "instrument reading - concrete strength" or linking the dependence established in the device in accordance with 6.1.9.
5.3 A tool for measuring the diameter of indentations (caliper according to GOST 166) used for the plastic deformation method should provide measurement with an error of no more than 0.1 mm. a tool for measuring the depth of an imprint (a dial indicator according to GOST 577, etc.) - with an error of no more than 0.01 mm.
5.4 Standard schemes for testing the method of separation with shearing and spalling of the rib provide for the use of anchor devices and grips in accordance with Annexes A and B.
5.5 For the chipping method, anchor devices should be used. the embedment depth of which shall not be less than the maximum size of the coarse concrete aggregate of the structure being tested.
5.6 For the pull-off method, steel discs with a diameter of at least 40 mm should be used. not less than 6 mm thick and not less than 0.1 diameter, with the roughness parameters of the glued surface not less than Ra = 20 µm according to GOST 2789. The adhesive for gluing the disc must provide adhesion strength to concrete, at which destruction occurs along concrete.
6 Test preparation
6.1 Procedure for preparing for testing
6.1.1 Preparation for testing includes checking the devices used in accordance with the instructions for their operation and establishing calibration dependencies between the concrete strength and the indirect strength characteristic.
6.1.2 The calibration dependence is established on the basis of the following data:
The results of parallel tests of the same sections of structures by one of the indirect methods and the direct non-destructive method for determining the strength of concrete;
The results of testing sections of structures by one of the indirect non-destructive methods for determining the strength of concrete and testing core samples taken from the same sections of the structure and tested in accordance with GOST 28570:
The results of testing standard concrete samples by one of the indirect non-destructive methods for determining the strength of concrete and mechanical tests in accordance with GOST 10180.
6.1.3 For indirect non-destructive methods for determining the strength of concrete, the calibration dependence is established for each type of normalized strength specified in 4.1 for concretes of the same nominal composition.
It is allowed to build one calibration dependence for concrete of the same type with one type of coarse aggregate, with a single production technology, differing in nominal composition and normalized strength value, subject to the requirements of 6.1.7
6.1.4 Permissible difference in the age of concrete of individual structures (sections, samples) when establishing a calibration dependence on the age of concrete of a controlled structure is taken according to 4.9.
6.1.5 For direct non-destructive methods according to 4.5, it is allowed to use the dependencies given in Appendices C and D for all types of normalized concrete strength.
6.1.6 The calibration dependence should have a standard (residual) deviation S T n m not exceeding 15% of the average concrete strength of the sections or samples used in the construction of the dependence, and the correlation coefficient (index) of at least 0.7.
It is recommended to use a linear relationship of the form R * a * bK (where R is the strength of concrete. K is an indirect indicator). The methodology for establishing, estimating parameters and determining the conditions for applying a linear calibration dependence is given in Appendix E.
6.1.7 When constructing the calibration dependence of the deviation of individual values of concrete strength R^ from the average value of the concrete strength of sections or samples R f. used to build the calibration dependence should be within:
> from 0.5 to 1.5 average concrete strength Rf at Rf £20 MPa;
From 0.6 to 1.4 average concrete strength R, f at 20 MPa< Я ф £50 МПа;
From 0.7 to 1.3 average concrete strength R f at 50 MPa<Я Ф £80 МПа;
From 0.8 to 1.2 the average value of concrete strength R f at R f > 80 MPa.
6.1.8 Correction of the established dependence for concretes of intermediate and design age should be carried out at least once a month, taking into account additionally obtained test results. The number of samples or areas of additional tests during the adjustment should be at least three. The correction method is given in Appendix E.
6.1.9 It is allowed to use indirect non-destructive methods for determining the strength of concrete, using calibration dependencies established for concrete that differs from the tested one in composition, age, hardening conditions, humidity, with reference in accordance with the method according to the assumption Zh.
6.1.10 Without reference to specific conditions according to Appendix G, the calibration dependencies established for concrete that differs from the tested one can only be used to obtain approximate strength values. It is not allowed to use approximate strength values without reference to specific conditions to assess the strength class of concrete.
6.2 Construction of a calibration dependence based on the results of concrete strength tests
in designs
6.2.1 When constructing a calibration dependence based on the results of testing the strength of concrete in structures, the dependence is established by single values of the indirect indicator and concrete strength of the same sections of structures.
For a single value of the indirect indicator, the average value of the indirect indicator in the area is taken. For a single value of the strength of concrete, the strength of the concrete of the site, determined by a direct non-destructive method or testing of selected samples, is taken.
6.2.2 The minimum number of single values for constructing a calibration dependence based on the results of testing the strength of concrete in structures is 12.
6.2.3 When constructing a calibration dependence based on the results of testing the strength of concrete in structures that are not subject to testing, structures or their zones, preliminary measurements are carried out by an indirect non-destructive method in accordance with the requirements of Section 7.
Then, sections are selected in the number provided for in 6.2.2, on which the maximum is obtained. minimum and intermediate values of the indirect indicator.
After testing by an indirect non-destructive method, the sections are tested by a direct non-destructive method or samples are taken for testing in accordance with GOST 26570.
6.2.4 To determine the strength at a negative temperature of concrete, the sections selected for constructing or linking the calibration dependence are first tested by an indirect non-erosion method, and then samples are taken for subsequent testing at a positive temperature or warmed up by external heat sources (infrared emitters, heat guns and etc.) to a depth of 50 mm to a temperature not lower than 0 * C and tested by a direct non-destructive method. The temperature control of the heated concrete is carried out at the 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 according to GOST 28243.
Rejection of the test results used to build the calibration dependence at a negative temperature is allowed only if the deviations are associated with a violation of the test procedure. In this case, the rejected result should be replaced by the results of a repeated test in the same area of the structure.
6.3 Construction of a calibration dependence on control samples
6.3.1 When constructing a calibration dependence on control samples, the dependence is established by single values of the indirect indicator and concrete strength of standard cube samples.
For a single value of the indirect indicator, the average value of the indirect indicators for a series of samples or for one sample (if the calibration dependence is established for individual samples) is taken. For a single value of the strength of concrete, the strength of concrete in a series according to GOST 10180 or one sample (calibration dependence for individual samples) is taken. Mechanical testing of samples according to GOST 10180 is carried out immediately after testing by an indirect non-destructive method.
6.3.2 When constructing a calibration dependence based on the results of testing sample cubes, at least 15 series of sample cubes according to GOST 10180 or at least 30 individual sample cubes are used. Samples are made in accordance with the requirements of GOST 10180 in different shifts, for at least 3 days, from concrete of the same nominal composition, according to the same technology, with the same hardening mode as the structure to be controlled.
The unit values of the concrete strength of the sample cubes used to build the calibration dependence must correspond to the deviations expected in production, while being within the ranges established in 6.1.7.
6.3.3 The calibration dependence for the methods of elastic rebound, shock impulse, plastic deformation, separation and chipping of the rib is established on the basis of the results of testing the manufactured sample cubes, first by the non-destructive method, and then by the destructive method in accordance with GOST 10180.
When establishing a calibration dependence for the tear-off method with shearing, the main and control samples are made according to 6.3.4. An indirect characteristic is determined on the main samples. control samples are tested in accordance with GOST 10180. The main and control samples must be made from the same concrete and harden under the same conditions.
6.3.4 The dimensions of the samples should be selected in accordance with the largest aggregate size in the concrete mixture in accordance with GOST 10180. but not less than:
100* 100* 100 mm for rebound, shock impulse, plastic deformation methods. as well as for the method of separation with chipping (control samples);
200*200*200mm for design rib chipping method:
300*300*300mm. but with a rib size of at least six anchor device installation depths for the pull-off method with shearing (basic samples).
6.3.5 To determine the indirect strength characteristics, tests are carried out in accordance with the requirements of Section 7 on the side (in the direction of concreting) faces of the sample cubes.
The total number of measurements on each sample for the method of elastic rebound, shock pulse, plastic deformation upon impact must be at least the established number of tests on the site according to Table 2. and the distance between the impact points - at least 30 mm (15 mm for the shock pulse method). For the indentation plastic deformation method, the number of tests on each face must be at least two, and the distance between the test points must be at least two indent diameters.
When establishing a calibration dependence for the rib shearing method, one test is carried out on each side rib.
When establishing the calibration dependence for the method of separation with shearing, one test is carried out on each side face of the main sample.
6.3.6 When tested by the method of elastic rebound, shock impulse, plastic deformation upon impact, the specimens shall be clamped in a press with a force of not less than (30 ± 5) kN and not more than 10% of the expected value of the breaking load.
6.3.7 The specimens tested by the pull-off method are mounted on the press as follows. so that the surfaces on which the pull-out was carried out do not adjoin to the base plates of the press. The test results according to GOST 10180 are increased by 5%.
7 Testing
7.1 General requirements
7.1.1 The number and location of controlled sections in structures must comply with the requirements of GOST 18105 and be indicated in the design documentation for structures or be set taking into account:
Control tasks (determining the actual class of concrete, stripping or tempering strength, identifying areas of reduced strength, etc.);
Type of construction (columns, beams, slabs, etc.);
Placement of grips and pouring order:
Structural reinforcement.
The rules for assigning the number of test sites for monolithic and prefabricated structures in the control of concrete strength are given in Appendix I. When determining the strength of concrete of the structures being examined, the number and location of the sites should be taken according to the survey program.
7.1.2 Tests are carried out on a construction site with an area of 100 to 900 cm2.
7.1.3 The total number of measurements in each area, the distance between the measurement points in the area and from the edge of the structure, the thickness of the structures in the measurement area should not be less than the values given in Table 2, depending on the test method.
Table 2 - Requirements for test sites
|
Method name |
Total number of measurements per plot |
Minimum distance between measurement points on the site, mm |
Minimum distance from the edge of the structure to the measurement point, mm |
Minimum Thickness structures, mm |
|
Elastic Bounce | ||||
|
shock impulse | ||||
|
Plastic deformation | ||||
|
Rib digging | ||||
|
2 disc diameters | ||||
|
Detachment with chipping at the working depth of the anchor L: * 40mm< 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%. The results of measurements that do not meet the specified condition are not taken into account when calculating the arithmetic mean of the indirect indicator for this area. The total number of measurements in each section when calculating the arithmetic mean must comply with the requirements of Table 2.
7.1.5 The strength of concrete in the controlled section of the structure is determined by the average value of the indirect indicator according to the calibration dependence established in accordance with the requirements of Section 6. provided that the calculated value of the indirect indicator is within the established (or tied) dependence (between the smallest and largest values strength).
7.1.6 The surface roughness of the structure concrete section when tested by the methods of rebound, impact impulse, plastic deformation should correspond to the surface roughness of the structure sections (or cubes) tested when establishing the calibration dependence. In necessary cases, it is allowed to clean the surfaces of the structure.
When using the indentation plastic deformation method, if the zero reading is taken after the application of the initial load, there are no requirements for the roughness of the concrete surface of the structure.
7.2 Rebound method
7.2.1 Tests are carried out in the following sequence:
The position of the device when testing the structure relative to the horizontal is recommended to be taken the same. as well as when establishing the calibration dependence. In a different position of the device, it is necessary to make a correction for the indicators in accordance with the instruction manual for the device:
7.3 Plastic deformation method
7.3.1 Tests are carried out in the following sequence:
The device is positioned so that the force is applied perpendicular to the surface under test in accordance with the instructions for use of the device;
When using a spherical indemtor to facilitate measurements of the diameters of prints, the test can be carried out through sheets of carbon paper and white paper (in this case, tests to establish the calibration dependence should be carried out using the same paper);
Fix the values of the indirect characteristic in accordance with the instruction manual for the device;
Calculate the average value of the indirect characteristic on the construction site.
7.4 Shock pulse method
7.4.1 Tests are carried out in the following sequence:
The device is placed like this. so that the force is applied perpendicular to the surface under test * in accordance with the instructions for use of the device:
The position of the device when testing the structure relative to the horizontal is recommended to be taken the same as when testing when establishing the calibration dependence. In a different position of the device, it is necessary to make a correction for the readings in accordance with the instruction manual for the device;
The value of the indirect characteristic is fixed in accordance with the instruction manual for the device;
Calculate the average value of the indirect characteristic on the construction site.
7.5 Pull-off method
7.5.1 When testing by the pull-off method, the sections should be located in the zone of the lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.
7.5.2 The test is carried out in the following sequence:
At the place where the disk is glued, a surface layer of concrete with a depth of 0.5-1 mm is removed and the surface is cleaned of dust;
The disk is glued to the concrete by pressing the disk and removing excess adhesive outside the disk;
The ribs are connected to the disk;
The load is smoothly increased with a speed of (1 ± 0.3) kN / s;
Record the reading of the force meter of the device;
Measure the projection area of the separation surface on the plane of the disk with an error of iO.Scm 2 ;
The value of the conditional stress in the concrete at separation is determined as the slope of the maximum separation force to the area of the projection of the separation surface.
7.5.3 The test results are not taken into account if the reinforcement was exposed during the detachment of concrete or the projection area of the detachment surface was less than 80% of the disk area.
7.6 Pull-off method with shear
7.6.1 When testing by the pull-off method with shearing, the sections should be located in the zone of the lowest stresses caused by the operational load or the compression force of the prestressed reinforcement.
7.6.2 Tests are carried out in the following sequence:
If the anchor device was not installed before concreting, then a hole is made in the concrete, the size of which is chosen in accordance with the device operating instructions, depending on the type of anchor device;
An anchor device is fixed in the hole to the depth provided for in the instruction manual for the device, depending on the type of anchor device;
The device is connected with a sunker device;
The load is increased at a rate of 1.5-3.0 kN / s:
The reading of the force meter of the P 0 device and the amount of slippage of the anchor LP (the difference between the actual depth of the pull-out and the depth of the anchor device) are recorded with an accuracy of not less than 0.1 mm.
7.6.3 The measured value of the pull-out force P 4 is multiplied by the correction factor y. determined by the formula
where L is the working depth of the anchor device, mm;
DP - anchor slippage, mm.
7.6.4 If the largest and smallest dimensions of the torn out part of the concrete from the anchor device to the boundaries of destruction along the surface of the structure differ by more than two times, and also if the depth of the torn out differs from the insertion depth of the anchor device by more than 5% (DL > 0.05ft, y > 1.1), then the test results can only be taken into account for an approximate assessment of the strength of concrete.
Note - Approximate values of the strength of concrete are not allowed to be used to assess the class of concrete in terms of strength and build calibration dependencies.
7.6.5 The results of the test are not taken into account if the pull-out depth differs from the depth of anchoring of the anchor device by more than 10% (dL > 0.1 A) or if the reinforcement was exposed at a distance from the anchor device less than the depth of its insertion.
7.7 Rib chipping method
7.7.1 When testing by the rib shearing method, there should be no cracks, concrete rims, sags or shells with a height (depth) of more than 5 mm in the test area. The sections should be located in the zone of the least stresses caused by the operational load or the compression force of the prestressed reinforcement.
7.7.2 The test is carried out in the following sequence:
The device is fastened to the structure. apply a load at a speed of no more than (1 ± 0.3) kN/s;
Record the reading of the instrument's force meter;
Measure the actual depth of chipping;
Determine the average value of the chipping force.
7.7.3 The test results are not taken into account if the reinforcement was exposed when concrete was chipped or the actual chipping depth differed from the specified one by more than 2 mm.
8 Processing and presentation of results
8.1 The test results are presented in a table indicating:
Type of construction;
Design class of concrete;
Age of concrete;
The strength of the concrete of each controlled area according to 7.1.5;
The average strength of the concrete structure;
Zones of the structure or its parts subject to the requirements of 7.1.1.
The form of the test results presentation table is given in Annex K.
8.2 Processing and assessment of compliance with the established requirements of the values of the actual strength of concrete, obtained using the methods given in this standard, is carried out according to GOST 18105.
Note in h in n and in - Statistical assessment of the concrete class according to the test results is carried out in accordance with GOST 18105 (schemes "A", "B" or "C") in cases where the strength of concrete is determined by the calibration dependence built in in accordance with section 6. When using previously established dependencies by linking them (according to Appendix G), statistical control is not allowed, and the assessment of the concrete class is carried out only according to the “G” scheme of GOST 18105.
8.3 The results of determining the strength of concrete by mechanical methods of non-destructive testing are drawn up in a conclusion (protocol), in which the following data are given:
About the tested structures indicating the design class, the date of concreting and testing, or the age of concrete at the time of testing;
On the methods used to control the strength of concrete;
About the types of devices with serial numbers, information about the verification of devices;
On the accepted calibration dependences (dependence equation, dependence parameters, compliance with the conditions for applying the calibration dependence);
Used to build a calibration dependence or its binding (date and results of tests by non-destructive indirect and direct or destructive methods, correction factors);
On the number of sites for determining the strength of concrete in structures, indicating their location;
Test results;
Methodology, results of processing and evaluation of the obtained data.
Standard Shear-Pull Test Design
A.1 The standard shear-pull test scheme provides for tests subject to the requirements of A.2 to A.6.
A.2 The standard test scheme is applicable in the following cases:
Tests of heavy concrete with compressive strength from S to 100 MPa:
Tests of lightweight concrete with compressive strength from S to 40 MPa:
The maximum fraction of coarse concrete aggregate is not more than the working depth of anchor devices.
A.3 The supports of the loading device must evenly adjoin the concrete surface at a distance of at least 2h from the axis of the anchor device, where L is the working depth of the anchor device. The test scheme is shown in Figure A.1.
1 - a device with a loading device and a measuring force; 2 - support of the loading device: 3 - grip of the loading device: 4 - transition elements, rods, S - anchor device. 6 - torn-out concrete (tear cone): 7 - tested structure
Figure A.1 — Schematic of the pull-out and shear test
A.4 The standard shearing test scheme provides for the use of three types of anchor devices (see Figure A.2). Anchor device type I is installed in the structure during concreting. Anchor devices of types II and ill are installed in holes previously prepared in the structure.
1 - working rod: 2 - working rod with frames of a different cone: 3 - segmented corrugated sheets: 4 - support rod: 5 - working rod with a ripe expanding cone: b - leveling washer
Figure A.2 — Types of anchor devices for a standard test scheme
A.5 The parameters of anchor devices and the permissible ranges of measured concrete strength for them under the standard test scheme are indicated in Table A.1. For lightweight concrete, in the standard test scheme, only anchor devices with a embedment depth of 48 mm are used.
Table A.1 - Parameters of anchor devices for a standard test scheme
|
Type of anchor device |
Anchor device diameter tf. mm |
Embedment depth of anchor devices, mm |
Permissible range of concrete compressive strength measurements for the anchor device. MPa |
||
|
working hours h |
fattening L" |
severe | |||
A.b Anchor designs of types II and III must provide preliminary (before applying the load) compression of the hole walls at the working depth of embedding l and slip control after the test.
Standard Rib Shearing Test Arrangement
B.1 The standard scheme of testing by the rib shearing method provides for testing subject to the requirements of B.2-B.4.
B.2 The standard test scheme is applicable in the following cases:
The maximum fraction of coarse concrete aggregate is not more than 40 mm:
Tests of heavy concrete with compressive strength from 10 to 70 MPa on crushed granite and limestone. B.3 For testing, a device is used, consisting of a power exciter with a force-measuring unit
crossbar and gripper with a bracket for local shearing of the structure rib. The test scheme is shown in Figure B.1.
1 - device with a loading device and a sipo-meter. 2 - support frame: 3 - chipped concrete: 4 - tested
construction^ - grip with bracket
Figure B.1 - Schematic of the rib shear test
B.4 In case of local shearing of the rib, the following parameters should be provided:
Depth of chipping a ■ (20 a 2) mm.
Cleaving width 0 "(30 and 0.5) mm;
The angle between the direction of the load and the normal to the loaded surface of the structure p "(18 a 1) *.
Calibration dependence for the pull-off method with shearing in the standard test scheme
When carrying out tests by the method of separation with squealing according to the standard scheme in accordance with Appendix A, the cubic strength of concrete is not compressive R. MPa. it is allowed to calculate according to the gravity dependence according to the formula
R*P)|P>^. (IN 1)
where m, is a coefficient that takes into account the maximum size of coarse aggregate in the pull-out zone and is taken equal to 1 when the aggregate size is less than 50 mm:
t 2 - coefficient of proportionality for the transition from the pull-out force in kilonewtons to the strength of concrete in megapascals:
P is the pull-out force of the anchor device. kN.
When testing heavy concrete with a strength of 5 MPa or more and light concrete with a strength of 5 to 40 MPa, the values of the proportionality factor m2 are taken from Table B.1.
Table 8.1
|
Type of anchor device |
Range of measured concrete compressive strength. MPa |
Anchor device diameter d. neither |
Depth of embedding of the anchor device, mm |
The value of the coefficient w^ for concrete |
|
|
severe | |||||
The coefficients m 3 when testing heavy concrete with an average strength above 70 MPa should be taken according to GOST 31914.
Calibration dependence for the rib shearing method with a standard test scheme
When performing the test by chipping the ribs according to the standard scheme in accordance with Appendix B, the cubic compressive strength of concrete on granite and lime rubble R. Mla. it is allowed to calculate according to the calibration dependence according to the formula
R - 0.058m (30R + PJ). (D.1)
where m is a coefficient that takes into account the maximum size of coarse aggregate and is taken equal to:
1.0 - with aggregate size less than 20 mm:
1.05 - with aggregate size from 20 to 30 mm:
1.1 - aggregate size from 30 to 40 mm:
P - chipping force. kN.
Annex D (mandatory)
Requirements for instruments for mechanical testing
Table E.1
|
Name of characteristics of devices |
Characteristics of devices for the method |
|||||||||||||||||||||||||||||||||||||
|
elastic |
shock momentum |
plastic deformations |
otryaa with skapyaa * and it |
|||||||||||||||||||||||||||||||||||
|
The hardness of the striker, striker or indenter of the NYaSe. at least | ||||||||||||||||||||||||||||||||||||||
|
The roughness of the contact part of the striker or indenter. µm. no more | ||||||||||||||||||||||||||||||||||||||
|
Impactor or indenter diameter. mm. at least | ||||||||||||||||||||||||||||||||||||||
|
The thickness of the edges of the disk indenter. mm. at least | ||||||||||||||||||||||||||||||||||||||
|
Conical indenter angle | ||||||||||||||||||||||||||||||||||||||
|
Indentation diameter, % of indenter diameter | ||||||||||||||||||||||||||||||||||||||
|
Tolerance of perpendicularity when applying a load not at a height of 100 mm. mm | ||||||||||||||||||||||||||||||||||||||
|
Impact energy. J. no less | ||||||||||||||||||||||||||||||||||||||
|
Load increase rate. kN/s | ||||||||||||||||||||||||||||||||||||||
|
Load measurement error, H. no more |
5 here RjN - see the explication to the formula (£.3). After rejection, the calibration dependence is established again according to the formulas (£.1) - (E.S) according to the remaining test results. The rejection of the remaining test results is repeated, considering the fulfillment of condition (E.6) when using a new (corrected) calibration dependence. Particular values of concrete strength must meet the requirements of 6.1.7. £.3 Parameters of the calibration dependence For the accepted calibration dependence, determine: The minimum and maximum values of the indirect characteristic H gave. Root-mean-square deviation ^ n m of the constructed calibration dependence according to the formula (E.7); Correlation coefficient of the calibration dependence r according to the formula
where the average value of concrete strength according to the calibration dependence is calculated according to the form
here are the values of R (H. I f.Ya f. N - see the explications to the formulas (E.E.). (E.b). E.4 Correction of the calibration dependence Adjustment of the established calibration dependence, taking into account 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. With the accumulation of data to build a calibration dependence, the results of previous tests. starting from the very first, they are rejected so that the total number of results does not exceed 20. After adding new results and rejecting old ones, the minimum and maximum values of the indirect characteristic, the calibration dependence and its parameters are set again according to formulas (E.1) - (E.9). E.S Conditions for applying the calibration dependence The use of a calibration dependence to determine the strength of concrete according to this standard is allowed only for values of an indirect characteristic falling in the range from N tl to n tad. If the correlation coefficient r< 0.7 или значение 5 тнм "Я ф >0.15. then the control and evaluation of the strength according to the obtained dependence is not allowed. The method of binding the calibration dependence G.1 The value of the strength of concrete, determined using the calibration dependence established for concrete that differs from the test, is multiplied by the coefficient of coincidence K s. The value is calculated according to the form where is the strength of concrete in t-th section, determined by chipping or core testing according to GOST 26570; I msa, - concrete's strength<-м участке, опредепяемвя пюбым косвенным методом по используемой градуировочной зависимости: л - число участков испытаний. G.2 When calculating the coefficient of coincidence, the following conditions must be met: The number of test sites taken into account when calculating the coefficient of coincidence, n i 3; Each private value R k, / R (0ca ^ should be at least 0.7 and not more than 1.3: Each particular value R^. , should differ from the average value by no more than 15%: The Yade values do not satisfy the conditions (G.2). (G.Z). should not be taken into account when calculating coefficient of coincidence K with. Assignment of the number of test sites for prefabricated and monolithic structures I.1 In accordance with GOST 18105, when testing the strength of concrete of prefabricated structures (tempering or transferring), the number of controlled structures of each type is taken at least JC and at least ^ structures from the batch. If the batch consists of 12 structures or less, complete control is carried out. In this case, the number of sections must be at least: 1 not 4 m length linear structures: 1 by 4 m 2 area of flat structures. I.2 In accordance with GOST 18105, when testing 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-erosion methods. I.Z In accordance with GOST 18105, when controlling the strength of concrete of monolithic structures at the design age, continuous nerve-breaking control of the strength of concrete of all structures of the controlled batch is carried out. In this case, the number of test sites must be at least: 3 for each grip for flat structures (wall, floor, foundation slab); 1 per 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 of a batch of structures should be at least 20. I.4 The number of single measurements of the strength of concrete by mechanical methods of nerve-destructive testing in each section (the number of measurements in the section) is taken according to table 2. Test result presentation table form
UDC 691.32.620.17:006.354 MKS 91.100.10 NEQ Key words: structural heavy and light concretes, monolithic and prefabricated concrete and reinforced concrete products, structures and structures, mechanical methods for determining compressive strength, elastic rebound, impact impulse, plastic deformation, separation, rib shearing, shearing separation Editor T.T. Martynova Technical editor 8.N. Prusakova Proofreader M 8. Vuchiaya Computer Layout I.A. Napaykina Handed over to the set 12/29/201S. Signed and stamped 06.02.2016. Format 60 «64^. Arial headset. Uel. oven l. 2.7V. Uch.-iad. l. 2.36. Tira” 60 eq. Zach. 263. Published and printed by FSUE STANDARTINFORM, $12399 Moscow. Garnet lane.. 4. | |||||||||||||||||||||||||||||||||||||
STATE STANDARDS OF THE UNION OF THE SSR
CONCRETE HEAVY
METHODS FOR DETERMINING STRENGTH WITHOUT DESTRUCTION BY MECHANICAL DEVICES
Official edition
USSR STATE COMMITTEE ON STANDARDS Moscow
UDC 691.32:620.17:006.354 Group Zh19
STATE STANDARD OF THE UNION OF THE SSR
CONCRETE HEAVY
General requirements for methods for determining the strength without destruction by mechanical action devices
Concrete. General requirements for methods of nondestructive strength determination by the mechanical devices
By the Decree of the State Committee of the Council of Ministers of the USSR for Construction of August 22, 1977 No. 128, the deadline for the introduction was established
from 01.07. 1978
Non-compliance with the standard is punishable by law
1. This standard applies to heavy concrete and establishes general requirements for methods for determining its compressive strength in products and structures with mechanical action devices for rebound, plastic deformation, chipping of the rib of the structure and separation.
Determination of the strength of concrete by the method of separation with shearing - according to GOST 21243-75.
2. The strength of concrete is determined by previously established experimental calibration dependencies between the strength of concrete samples tested in accordance with GOST 10180-78, and indirect characteristics of the strength of concrete (rebound value, imprint size, shearing force of the structure rib, conditional stress at separation) h established by non-destructive tests of those the same samples.
3. To build a calibration dependence, cube samples are used that meet the requirements of GOST 10180-78 and have dimensions, cm:
15X15X15 - for rebound and plastic deformation methods;
20X20X20 - for methods of shearing the rib of the structure and separation.
Official publication Reprint prohibited
Reissue. November 1981
© Standards Publishing, 1982
Op. 10 GOST 22690.0-77
FORM OF THE JOURNAL FOR DETERMINING THE STRENGTH OF CONCRETE IN STRUCTURES
1. Test object_______
2. Test date _
3. Name of the structure (for prefabricated structures - brand, a series of working drawings)_ „_
4. Type of concrete and its design strength _
5. Test method, instrument, test parameters (impact energy, indenter size or disk area, standard material, etc.).
6. Test results (see table)
Page 2 GOST 22690.0-77
The calibration dependence for controlling the strength of concrete of the same brand is established based on the results of testing at least 20 series, each of which consists of three twin samples. The specimens shall have the same composition, duration and curing conditions as the concrete used for the manufacture of the controlled structures. Samples are made within two weeks (at least) in different shifts. To obtain a calibration dependence in a wider range of strength changes, up to 40% of samples should be prepared with a deviation in the cement-water ratio of up to ±0.4. The rejection of abnormal test results of samples is carried out according to mandatory Appendix 1.
4. When controlling the strength of concrete in erected structures, at least 20 cube samples are cut out from different sections, while the test result of one sample is equated to the test result of a series of samples.
It is allowed to establish a calibration dependence by testing cubes with a side of at least 7.07 cm or cores with a diameter of at least 7.14 cm. In this case, the following test procedure should be followed. Non-destructive tests are carried out at the construction site, then a sample is cut out and tested for compression. The boundaries of the non-destructive testing zones and the sample cuts should be at a distance of no more than 100 mm from each other.
5. The calibration dependence should be set at least twice a year, as well as when changing the materials used for the preparation of concrete, and the technology for manufacturing structures.
The method for calculating the equation of the calibration dependence is given in the recommended appendix 2, and an example of its construction is given in reference appendix 3.
6. The estimation of the error of the calibration dependence is carried out according to GOST 17624-78.
7. Experts from specialized research organizations can conduct an approximate assessment of the strength of concrete using a calibration dependence established for concrete that differs from the tested one (in composition, age and hardening conditions), with its refinement based on the results of testing at least three cut samples or three tests by tear-off method with shearing according to GOST 21243-75.
8. Instruments used to determine the strength of concrete must undergo departmental verification at least once every two years, as well as after each repair or replacement of parts. The verification results must be documented.
9. Sites for testing concrete should be selected on the surfaces of the structure that were in contact during manufacture with metal, planed wood or other smooth formwork. EU-
GOST 22690.0-77 Page 3
If the surface of the structure has a finish, it must be removed before testing.
10. Strength should be determined at a positive temperature of concrete.
11. The strength of concrete in the construction site is determined by the average value of the indirect characteristic of the strength of concrete in this area, using the established calibration dependence, taking into account the rejection of abnormal results, produced according to the mandatory Appendix 1.
Test results should be recorded in a log, the form of which is given in the recommended Appendix 4.
12. Control and assessment of the compressive strength of concrete and its uniformity in structures - according to GOST 18105.0-80-GOST 18105.2-80.
Page 4 GOST 22690.0-77
ANNEX 1 Mandatory
RULES FOR REJECTION OF ABNORMAL TEST RESULTS
1. The rejection of abnormal test results (A*) is carried out when the number of results is at least 3 according to the formula (1):
a) for the result of a test on a press of one sample in a series;
b) for a single non-destructive test result in one sample;
c) for a single test result by a non-destructive method in a section of the structure.
2. The test result is considered abnormal and is not taken into account in the calculation,
if the value of T, determined by the formula (1), exceeds the allowable value of Tk, given in table. one. _
where A is the average strength of concrete in a series of samples, the average result of a non-destructive test of one sample or section of the structure;
5 - average standard deviation, determined when calculating the calibration dependence according to formula (2).
Table 1
T value and
where d is the coefficient taken according to the table. 2;
Xi max and Xi min - maximum and minimum test results in a series of samples or in a separate sample;
N is the number of series (case a) or the number of individual samples (case b) used in the construction of the calibration dependence.
When evaluating the abnormality of individual test results in sections of structures, the value of S is taken equal to that calculated for individual samples when constructing a calibration dependence.
table 2
The value of the coefficient d
GOST 22690.0-77 Page five
METHOD OF CALCULATION OF THE EQUATION OF THE CALIBRATION DEPENDENCE "INDIRECT CHARACTERISTIC - STRENGTH"
The equation of dependence "indirect characteristic - strength" is taken:
with a range of fluctuations in the strength of concrete up to 200 kgf / cm 2 - linear:
with a range of fluctuations in the strength of concrete over 200 kgf / cm 2 exponential:
R- b 0 - / b, n. (2)
Coefficients about 0 ; ai b x is calculated by the formulas.
#0 - R-(i\‘ //,* (3)
"='-H?-z-: (4)
2 (Hi-77)(In Ri-UiR)
| b n \u003d c ^ - b "". |
The average values of strength R and indirect characteristics R, necessary to determine these coefficients, are calculated by the formulas:
*= Chg:< 7 >
In /?-=*"" s - ; (nine)
The values Ri and Hi are, respectively, the values of strengths and indirect characteristics for individual series of three samples (or one sample), and N is the number of series (or individual samples) used to build the calibration dependence.
It is allowed to use the equation of the form (1) (or graphical construction) of the calibration dependence in cases where the error and the efficiency coefficient of the dependence, determined in accordance with GOST 17624-78, are within the permissible limits.
The estimation of the error of the calibration dependence is carried out according to GOST
Page 6 GOST 22690.0-77
APPENDIX $ Reference
EXAMPLES OF CONSTRUCTION OF THE CALIBRATION DEPENDENCE AND SELECTING OF ABNORMAL TEST RESULTS
Building a calibration dependence
The strength of concrete of the design grade M250 is controlled by the rebound method using the KM device. To build the relationship between the rebound value (R) and the compressive strength of the control samples on the press (/?), 29 series of samples were tested (A r * = 29). The average results for each series are given in table. !.
Table 1
| Series number |
H, division |
Serine number |
W, division |
R, kgf/cm" |
|
Since the concrete strength measurement range 330-169 "=" 170 kgf / cm * is less than 200 kgf / cm *, then, in accordance with the method set forth in the recommended Appendix 2, the equation of the desired dependence is assumed to be linear: * = Oo + a g I. The coefficients of the equation are calculated by substituting the table data in_formults (3) and (4) of the recommended application 2.
I * 252.9 kgf / cm 3; h "18.24; "36.76; co--417.79.
The calibration dependence "rebound value - strength" is expressed by the equation # "36.76 R-413.
The dependency graph is shown in the drawing.
GOST 22690.0-77 Page one
Dependence "Indirect characteristic (rebound value) - strength"
R, kgf / cm 1
Calculation of standard deviations for strength in a series of 3 samples and for the rebound value in 5 measurements on one sample.
When constructing a calibration dependence (see example I), 29 series of 3 samples were tested. In each sample, the rebound value was determined at 5 points. A selection from the table of test results is given in table. 2.
table 2
| Series numbers 1 |
Sample numbers; | |
Test point numbers for |
/? , KGOSL1* |
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Page, 8 GOST 22690.0-77
Continuation
| Series numbers 1 |
Sample numbers / |
Test point numbers for |
Rj t kts / cm 3 |
f U max** min" |
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| 16.9 17.5 18.8 19.0 18.2 Avg. 18.1 |
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The root mean square deviation of the strength of concrete in a series of samples, determined by the formula (2) and table. 2 will be
S- --- - = 18 kix/cm l .
The same formula is used to calculate the standard deviation of the rebound height on the KM device in samples
4,1+2,9+2,5+3,3+2,1+1,9+...
JTsh--"" 5<е *’
In the second series (see example 2), the strength of the third sample differs significantly from the average in the series. To check the abnormality of this result, according to the formula (1) of mandatory Appendix 1, calculate the value
GOST 22690.0-77 Page nine
which is less than the value determined according to the table T to -1.74 for three samples in the series. Therefore, the result of 252 kgf/cm 2 should not be excluded when determining the strength of concrete in the second series of samples.
In the first sample of the first series (see example 2) the result is 16.0 cases. significantly different from the sample mean. To check the abnormality of this result, according to the formula (1) of mandatory Appendix 1, calculate the value
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