GBJ 81-1985 Test methods for mechanical properties of concrete GBJ81-85
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Engineering Construction Standard Full-text Information System
National Standard of the People's Republic of China
Test Method for Mechanical Properties of Ordinary Concrete
GBJ81—85
1985 Beijing
Engineering Construction Standard Full-text Information System
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National Standard of the People's Republic of China
Test Method for Mechanical Properties of Ordinary Concrete
Editor Department: Ministry of Urban and Rural Construction and Environmental Protection
Approving Department: State Planning Commission of the People's Republic of China Committee Implementation date: July 1, 1986
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
Notice on the release of three national standards including "Test Methods for Performance of Ordinary Concrete Mixtures"
According to the requirements of the former National Construction Committee (78) Jianfa Shezi No. 562, the three standards including "Test Methods for Performance of Ordinary Concrete Mixtures" jointly compiled by the Ministry of Urban and Rural Construction and the China Academy of Building Research and relevant units have been reviewed by relevant departments. The three standards including "Test Methods for Performance of Ordinary Concrete Mixtures" GBJ80-85, "Test Methods for Mechanical Properties of Ordinary Concrete" GBJ81-85 and "Test Methods for Long-term Performance and Durability of Ordinary Concrete" GBJ82-85 are now approved as national standards and will be implemented from July 1, 1986.
The three standards are managed by the Ministry of Urban and Rural Construction, and the specific interpretation and other work is the responsibility of the China Academy of Building Research. The publication and distribution is organized by the Institute of Basic Construction Standards and Norms of our Commission.
State Planning Commission
November 25, 1985
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Engineering Construction Standard Full Text Information System
Preparation Instructions
This standard is prepared by the China Academy of Building Research in conjunction with relevant units in accordance with the requirements of the Notice No. 562 of the former State Construction Commission (78) Jianfashe. During the preparation process, a large amount of investigation, research and experimental demonstration work was carried out, and international standards and other relevant domestic and foreign standards were collected and referenced. After repeated discussions and revisions, the standard was formed. During the preparation process, the opinions of relevant units across the country were solicited many times, and finally it was reviewed and finalized with relevant departments.
This standard is the test method for mechanical properties of the basic properties of ordinary concrete. The content includes five methods: cube compressive strength, axial compressive strength, static compressive elastic modulus, splitting tensile strength and flexural strength. Since the test of mechanical properties of ordinary concrete involves a wide range, the text itself will continue to develop with the improvement of instruments and equipment and the improvement of testing technology. Therefore, it is hoped that all units will pay attention to accumulating information and summarizing experience in the process of implementing this standard. If you find that there is a need for modification or supplement, please send your opinions and relevant information to the Concrete Research Institute of China Academy of Building Research for reference in future modifications. Urban and Rural Construction and Environmental Protection Department
July 1985
Engineering Construction Standard Full Text Information System
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Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Preparation and maintenance of test pieces
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Cube compressive strength test
Axial compression strength test Strength test
Static compression elastic modulus test
Split tensile strength test
Flexural strength test
Appendix Explanation of terms used in this specificationbzxz.net
Additional explanation
Engineering Construction Standard Full-text Information System
Engineering Construction Standard Full-text Information System
Chapter 1 General
Article 1.0.1 This standard is specially formulated in order to have a unified concrete mechanical properties test method when determining the concrete design characteristic value, inspecting or controlling the quality of cast-in-place concrete engineering or prefabricated components.
Article 1.0.2 This standard applies to the basic performance test of ordinary concrete used in industrial and civil buildings and general structures. Engineering Construction Standard Full-text Information System
Engineering Construction Standard Full-text Information System
Chapter 2 Preparation and maintenance of test specimens
Article 2.0.1 The concrete mechanical properties test should be carried out on three specimens as a group. The mixture used in each group of test specimens shall be taken from the same pan of concrete or the same truck according to different requirements, or mixed separately in the laboratory by machine or manually. The grouping and sampling principles of test specimens used to inspect the quality of cast-in-place concrete engineering or prefabricated components shall be implemented in accordance with the current "Specifications for Construction and Acceptance of Reinforced Concrete Engineering" and other relevant regulations. Article 2.0.2 When making test specimens of concrete mixed in the laboratory, the amount of materials used shall be measured by weight, and the weighing accuracy shall be: cement, water and admixtures are all ±0.5%; aggregate is ±1%.
Article 2.0.3 All test specimens shall be made immediately after sampling. When determining the design characteristic value and grade of concrete or conducting material performance research, the molding method of the test specimen shall be determined according to the consistency of the concrete. Concrete with a drop of no more than 70 mm should be compacted by a vibrating table, and concrete with a drop of more than 70 mm should be compacted manually by a tamping rod. For concrete used to inspect the quality of cast-in-place concrete engineering and prefabricated components, the molding method of the test specimen shall be the same as the method used in actual construction.
Prismatic and small beam specimens should be formed horizontally. For concrete specimens formed by special methods such as centrifugal method, grouting method, vacuum operation method and injection method, the production of specimens should be carried out in accordance with the relevant regulations. Article 2.0.4 The test mold used to make the specimen is made of cast iron or steel, which should have sufficient rigidity and be easy to disassemble and assemble. The inner surface of the test mold should be machined, and its unevenness should not exceed 0.05 mm per 100 mm. The non-verticality of adjacent surfaces after assembly should not exceed ±0.5 degrees.
Before making the specimen, the test mold should be cleaned and a layer of mineral grease or other release agent should be applied to its inner wall.
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Article 2.0.5 When using a vibration table for molding, the concrete mixture should be loaded into the test mold at one time. When loading, a spatula should be used to slightly insert and tamp along the inner wall of the test mold and make the concrete mixture higher than the upper mouth of the test mold. When vibrating, the test mold should be prevented from jumping freely on the vibration table. The vibration should continue until the concrete surface is slurried, and the excess concrete should be scraped off and smoothed with a spatula. The vibration frequency of the laboratory vibration table should be 50 ± 3 Hz, and the amplitude should be about 0.5 mm when unloaded.
Article 2.0.6 When manually inserting and tamping, the concrete mixture should be loaded into the test mold in two layers, and the thickness of each layer should be roughly equal. The steel rod used for inserting and tamping is 600 mm long and 16 mm in diameter, and the end should be rounded. The insertion and removal should be carried out evenly from the edge to the center in a spiral direction. When inserting the bottom layer, the tamping rod should reach the surface of the test mold. When inserting the upper layer, the tamping rod should penetrate the lower layer to a depth of 20 to 30 mm. The tamping rod should be kept vertical and not tilted during insertion. At the same time, a spatula should be inserted several times along the inner wall of the test mold. The number of insertions and tamping for each layer should be determined according to the cross-section of the test piece. Generally, it should not be less than 12 times per 100 square centimeters of cross-sectional area. After the insertion and tamping, scrape off the excess concrete and smooth it with a spatula. Article 2.0.7 Depending on the purpose of the test, the test piece can be cured with standard conditions or cured under the same conditions as the component.
Standard curing should be used when determining the characteristic value, grade or material performance research of concrete.
When testing the strength of concrete in cast-in-place concrete engineering or prefabricated components, the test piece should be cured under the same conditions.
The test piece is generally cured to 28 days of age (calculated from the time of molding) for testing. However, it can also be cured to the required age as required (such as to determine the mechanical properties when demolding, lifting, applying prestress or bearing construction loads, etc.). Article 2.0.8 The test pieces using standard curing should be covered with a surface after molding to prevent moisture evaporation, and should be left to stand for one to two nights at a temperature of 20 ± 5 ° C, and then numbered and demolded.
After demolding, the test pieces should be immediately placed in a standard curing room with a temperature of 20 ± 3 ° C and a humidity of more than 90% for curing. In the standard curing room, the test pieces should be placed on a rack, with each other Engineering Construction Standard Full Text Information System
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The interval is 10 to 20 mm, and water should be avoided to directly flush the specimen. When there is no standard curing room, the concrete specimen can be cured in stagnant water at a temperature of 20 ± 3 ° C. The pH value of water should not be less than 7. The specimens cured under the same conditions should be covered after forming. The demolding time of the specimen can be the same as the demolding time of the actual component. After demolding, the specimen still needs to be maintained under the same conditions. Civil Engineering Construction Standard Full Text Information System
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Chapter 3 Cube Compressive Strength Test
Section 3.0.1. This method is applicable to the determination of the compressive strength of concrete cube specimens.
Article 3.0.2 The size of the concrete specimen shall be selected according to the maximum particle size of the aggregate in the concrete in accordance with Table 3.0.2.
Selection table of concrete cube specimen size
Specimen size (mm)
100×100×100
150×150×150
200×200×200
Maximum particle size of aggregate
(mm)
Article 3.0.3 The accuracy (relative error of indication) of the testing machine used in the concrete cube compressive strength test shall be at least ±2%, and its range shall be such that the expected failure load value of the specimen shall not be less than 20% of the full range, nor greater than 80% of the full range. Steel pads can be placed between the upper and lower pressure plates of the testing machine and the test piece, and both pressure-bearing surfaces of the steel pads should be machined.
The size of the pressure plate or pad in contact with the test piece should be larger than the pressure-bearing surface of the test piece, and its unevenness should not exceed 0.02 mm per 100 mm. Article 3.0.4 After the test piece is taken out from the curing site, the test should be carried out as soon as possible to avoid significant changes in the temperature and humidity inside the test piece. The concrete cube compressive strength test should be carried out according to the following steps
1. First, wipe the test piece clean, measure the size, and check its appearance. The test piece size is measured accurately to 1 mm, and the pressure-bearing area of the test piece is calculated accordingly. If the difference between the actual measured size and the nominal size does not exceed 1 mm, it can be calculated according to the nominal size. The unevenness of the pressure-bearing surface of the test piece should not exceed 0.05 mm per 100 mm, and the non-perpendicularity between the pressure-bearing surface and the adjacent surface should not exceed ±1 degree. Place the test piece on the lower pressure plate of the testing machine, and the pressure-bearing surface of the test piece should be perpendicular to the top surface during molding. The center of the test piece should be aligned with the center of the lower pressure plate of the testing machine. Start the testing machine, and when the upper pressure plate is close to the test piece, adjust the ball seat to make the contact balanced. The concrete specimens shall be loaded continuously and evenly, and the loading speed shall be: when the concrete strength grade is lower than C30 (equivalent to the original No. 300), take 0.3-0.5 MPa (3-5 kgf/cm2) per second; when the concrete strength grade is higher than or equal to C30 (equivalent to the original No. 300), take 0.5-0.8 MPa (5-8 kgf/cm2) per second. When the specimen is close to failure and begins to deform rapidly, stop adjusting the throttle of the testing machine until the specimen is destroyed. Then record the failure load. Article 3.0.5 The compressive strength of concrete cube specimens shall be calculated according to the following formula: f
Where: fec-compressive strength of concrete cube specimen (MPa); P-failure load (N)
A-bearing area of specimen (square millimeter)
....(3. 0. 5)
The concrete cube compressive strength calculation should be accurate to 0.1 MPa (1 kg/cm2).
The arithmetic mean of the three test pieces is taken as the compressive strength value of the group of test pieces. If the difference between the maximum or minimum of the three measured values and the middle value exceeds 15% of the middle value, the maximum and minimum values are discarded and the middle value is taken as the compressive strength value of the group of test pieces. If the difference between two measured values and the middle value exceeds 15% of the middle value, the test results of the group of test pieces are invalid. Take 150×150×1 The compressive strength of the 50 mm specimen is the standard value. The strength values measured with specimens of other sizes should be multiplied by the size conversion factor, which is 1.05 for 200×200×200 mm specimens and 0.95 for 100×100×100 mm specimens. Engineering Construction Standards Full-text Information System
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Chapter 4
Axial Compressive Strength Test
Article 4.0.1 This method is applicable to the determination of the axial compressive strength of concrete prism specimens. Compressive strength.
Article 4.0.2 The axial compressive strength test of concrete shall use a 150×150×300 mm prism as the standard specimen.
If necessary, non-standard prism specimens may be used, but their aspect ratio shall be within the range of 2 to 3.
The maximum aggregate particle size allowed in the specimen shall not be greater than the value specified in Table 4.0.2. Prism Specimen Size Selection Table
Minimum side length of specimen (mm)
Maximum aggregate particle size (mm)
Article 4.0.3 Concrete The testing machine used for the axial compressive strength test of concrete should meet the requirements set forth in Article 3.0.3.
Article 4.0.4 The test piece should be tested promptly after being taken out of the curing site to avoid significant changes in the temperature and humidity inside the test piece. The axial compressive strength test of concrete should be carried out in the following steps
1. First wipe the test piece clean, measure the size, and check its appearance. The test piece size is measured to an accuracy of 1 mm, and the pressure-bearing area of the test piece is calculated accordingly. If the difference between the measured size and the nominal size does not exceed 1 mm, it can be calculated according to the nominal size. The unevenness of the pressure-bearing surface of the test piece should not exceed 0.05 mm per 100 mm, and the full-text information system of the pressure-bearing engineering construction standard
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Chapter 4
Axial compressive strength test
Article 4.0.1 This method is applicable to the determination of the axial compressive strength of concrete prism specimens.
Article 4.0.2 The 150×150×300 mm prism shall be used as the standard specimen for the axial compressive strength test of concrete.
If necessary, non-standard prism specimens may be used, but their aspect ratio shall be within the range of 2 to 3.
The maximum aggregate size allowed for the specimen shall not be greater than the value specified in Table 4.0.2. Prism specimen size selection table
Minimum side length of specimen (mm)
Maximum aggregate size (mm)
Article 4.0.3 The testing machine used for the axial compressive strength test of concrete shall meet the requirements set forth in Article 3.0.3.
Article 4.0.4 The test piece should be tested promptly after being taken out of the curing site to avoid significant changes in the temperature and humidity inside the test piece. The axial compressive strength test of concrete should be carried out according to the following steps
1. First, wipe the test piece clean, measure the size, and check its appearance. The test piece size is measured to an accuracy of 1 mm, and the pressure-bearing area of the test piece is calculated accordingly. If the difference between the measured size and the nominal size does not exceed 1 mm, it can be calculated according to the nominal size. The unevenness of the pressure-bearing surface of the test piece should not exceed 0.05 mm per 100 mm, and the pressure-bearing engineering construction standard full-text information system
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Chapter 4
Axial compressive strength test
Article 4.0.1 This method is applicable to the determination of the axial compressive strength of concrete prism specimens.
Article 4.0.2 The 150×150×300 mm prism shall be used as the standard specimen for the axial compressive strength test of concrete.
If necessary, non-standard prism specimens may be used, but their aspect ratio shall be within the range of 2 to 3.
The maximum aggregate size allowed for the specimen shall not be greater than the value specified in Table 4.0.2. Prism specimen size selection table
Minimum side length of specimen (mm)
Maximum aggregate size (mm)
Article 4.0.3 The testing machine used for the axial compressive strength test of concrete shall meet the requirements set forth in Article 3.0.3.
Article 4.0.4 The test piece should be tested promptly after being taken out of the curing site to avoid significant changes in the temperature and humidity inside the test piece. The axial compressive strength test of concrete should be carried out according to the following steps
1. First, wipe the test piece clean, measure the size, and check its appearance. The test piece size is measured to an accuracy of 1 mm, and the pressure-bearing area of the test piece is calculated accordingly. If the difference between the measured size and the nominal size does not exceed 1 mm, it can be calculated according to the nominal size. The unevenness of the pressure-bearing surface of the test piece should not exceed 0.05 mm per 100 mm, and the pressure-bearing engineering construction standard full-text information system
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