JGJ 15-1983 Test method for early estimation of concrete strength JGJ15-83
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Engineering Construction Standard Full-text Information System
Ministry of Urban and Rural Construction and Environmental Protection of the People's Republic of China Standard Test Method for Early Estimation of Concrete Strength
JGJ15-83
1983Beijing
Engineering Construction Standard Full-text Information System
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Ministry of Urban and Rural Construction and Environmental Protection of the People's Republic of China Standard Test Method for Early Estimation of Concrete Strength
JGJ15-83
Editor Department: China Academy of Building Research Approving department: Ministry of Urban and Rural Construction and Environmental Protection Trial date: September 1, 1983
Engineering Construction Standards Full Text Information System
Engineering Construction Standards Full Text Information System
(83) Chengkezi No. 223
According to the arrangement of the former State Construction Engineering Administration, the China Academy of Building Research is responsible for the compilation of the "Early Estimation of Concrete Strength Test Method" with the participation of relevant scientific research, production and construction units and colleges and universities across the country. After review and approval by our department, it is approved as a departmental standard with the code and number JGJ15-83, and will be implemented on September 1, 1983.
If any unit finds that there is a need for modification or supplementation in the process of using this standard, please send your opinions or materials to the Structural Research Institute of the China Academy of Building Research.
Ministry of Urban and Rural Construction and Environmental Protection
April 14, 1983
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Preparation Instructions
The "Early Estimation of Concrete Strength Test Method" was prepared by our institute in conjunction with the Science and Technology Department of Beijing Construction Engineering Bureau, the Research Institute of China Construction Fourth Engineering Bureau, Xi'an Institute of Metallurgy and Architecture, the Research Institute of China Construction Third Engineering Bureau, Hebei No. 1 Construction Engineering Company, Guangxi No. 5 District Construction Engineering Company, Beijing No. 1 Building Component Factory, Shanghai No. 1 Concrete Products Factory, Shenyang Construction Engineering Research Institute, Shanxi No. 1 Construction Engineering Company Processing Plant and China Construction Sixth Engineering Bureau Fourth Company and other units.
Before the preparation of this standard, a special cooperation group of relevant units across the country was organized to conduct systematic experimental research on various early estimation of concrete strength test methods, which provided the necessary scientific basis for the preparation of this standard. In addition to absorbing the above scientific research results, this standard also draws on similar foreign standards, and has carried out pilot applications, solicited opinions from relevant units across the country, and finally finalized by a special review meeting.
This standard is divided into four chapters and two appendices. The main contents include scope of application, accelerated curing equipment, accelerated curing test methods (boiling water method, hot water method, warm water method), establishment of concrete strength relationship and strength estimation, etc. If you find that there is a need for modification or supplementation during the implementation of this standard, please send your opinions and relevant materials to our Institute of Building Structures. China Academy of Building Research
January 1983
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Chapter 1
Chapter 2
Chapter 3
Chapter 4
Accelerated Curing Equipment·
Accelerated Curing Test Method
(4)
Establishment of concrete strength relationship and estimation of strength·..(6) Method of establishing concrete strength relationship·Example of early estimation of concrete strength
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(10)
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Basic symbols
Estimated value of strength of concrete specimens with standard curing; measured value of strength of concrete specimens with accelerated curing; correlation coefficient of regression equation;
Residual standard deviation of regression equation;
Standard deviation of conversion relationship;
Measured value of strength of concrete specimens with standard curing; Average value of strength of n groups of concrete specimens with standard curing; Average value of strength of n groups of concrete specimens with accelerated curing; Number of pairs of specimens.
Engineering Construction Standard Full Text Information System
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Chapter 1 General Provisions
Article 1.1 The test method specified in this standard is to use the strength of accelerated curing concrete specimens to estimate the strength of concrete cured for 28 days (or other ages) at an early stage. The estimated concrete strength is applicable to quality control in concrete production and the design and adjustment of concrete mix proportions. This standard is applicable to ordinary concrete mixed with various silicate cements that meet the national standards.
Note: This standard is applicable to ordinary concrete mixed with calcium lignin sulfonate. When other types of admixtures are added, they must be determined by tests.
Article 1.2 This standard includes three accelerated curing test methods: boiling water method, 80℃ hot water method and 55℃ warm water method. When used, they can be selected according to specific conditions.
When using early estimated concrete strength test methods other than those specified in this standard, the requirements of Article 4.4 of this standard must be met. Article 1.3 The size and molding method of concrete specimens, the test method of the fall, workability, and compressive strength of the mixture, as well as the conversion coefficient of the strength of specimens of different sizes, shall be implemented in accordance with the relevant standards. Engineering Construction Standard Full Text Information System
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Chapter 2 Accelerated Curing Equipment
Article 2.1 Accelerated Curing Box The shape and size of the accelerated curing box shall be determined according to the size, quantity and placement of the specimens in the box. There should be at least 5 cm of space between the specimen and the box wall and between each specimen, and the bottom of the specimen should be no less than 10 cm from the heat source. During the entire curing period, the water level in the box should be kept 5 cm above the top surface of the specimen (Figure 2-1). Figure 2-1 Schematic diagram of accelerated curing box
1-The curing box is composed of double-layer metal plates filled with insulation materials: 2-Thermal resistor or contact thermometer connected to the automatic temperature control system, 3 Ordinary thermometer, 4 Bracket for placing the test piece; 5-Tubular electric heating element, 6-Test piece a>5cm, b10cm
The accelerated curing box should be able to ensure that the water temperature in the box is maintained within 2℃ of the specified temperature. The heat source should be able to ensure that the water temperature in the box is restored to the specified temperature within 15 minutes after the test piece is placed in the water tank. When the accelerated curing box has an automatic temperature control device, a thermometer or other temperature measuring device independent of the temperature automatic control system should also be used to calibrate the water temperature. Note: When used for the boiling water method, the accelerated curing box does not need an automatic temperature control device. Article 2.2 When the test mold is used for accelerated curing, the test mold should have a sealing device to ensure that the mortar moisture does not leak and affect the composition of the concrete. During the test, a special sealed test mold can be used, or a rubber pad can be covered on the ordinary test mold, a steel plate can be added, and the clamp can be used to clamp the test mold to make it sealed (Figure 2-2). 2
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Figure 2-2 Test mold sealing device
Schematic diagram
1-Steel plate, thickness 6~8mm, length
width depends on the size of the test mold; 2-Rubber
pad, thickness 35mm, length and width slightly
larger than the outer edge size of the test mold, 3-Pull rod,
06~8mm, 4 Test mold
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Chapter 3 Accelerated Curing Test Method
Article 3.1 Boiling Water Method
After the specimen is formed and plastered, the surface is immediately covered with a rubber pad or plastic cloth and placed in a standard curing room or a room with a room temperature of 20±5℃ for standing. From adding water to mixing, taking to forming, standing and demoulding, a total of 24 hours ± 15 minutes. Sample
Immerse the demoulding specimen in boiling water in the accelerated curing box. The water temperature in the box should return to the boiling point within 15 minutes after the specimen is immersed. The water in the box should remain boiling during the entire curing period.
During the entire curing period, the temperature of the curing water must be continuously or regularly measured and recorded.
The specimen is cured in boiling water for 4 hours ± 5 minutes. Take out the specimen and let it stand at room temperature for 1 hour ± 10 minutes to cool it. When the specimen age is 29 hours ± 15 minutes, a compression test is carried out according to the method specified in the relevant standards to measure its accelerated curing strength.
Note: ±, when the early strength of the concrete is too low and it is not suitable to demould for accelerated curing, the specimen should be cured with the mold.
2. In order to prevent excessive evaporation of water in the boiling water tank, when a temperature control device is installed, it is allowed to control the water temperature at 1~2℃ below the boiling point.
Section 3.2. 80℃ hot water method
After the specimen is formed and plastered, the test mold is immediately sealed. From adding water to mix, sampling, to forming and standing, it takes a total of 1 hour ± 10 minutes. Then, the test mold with the information (hereinafter referred to as the time from adding water to mix, sampling, forming... to the standing time after accelerated curing) is immersed in 80℃ hot water in the curing box. The water temperature in the box should be restored to 80±2℃ within 15 minutes after the specimen is immersed. During the entire curing period, the water temperature in the box should be maintained at 80±2℃.
The curing water temperature must be continuously or regularly measured and recorded during the entire curing period.
The specimen is cured in 80±2℃ hot water for 5 hours±5 minutes, the molded specimen is taken out, demoulded, and allowed to stand at room temperature to cool for a total of 1 hour±10 minutes. Then, when the specimen age is 7 hours±15 minutes, a compression test is carried out according to the method specified in the relevant standards to measure its accelerated curing strength. Article 3.3 55℃ warm water method
After the specimen is formed and plastered, the test mold is immediately sealed. From adding water to mix, sampling, to the end of forming and standing, a total of 1 hour±10 minutes. Then the specimen with the test mold is immersed in 55℃ warm water in the curing box. The water temperature in the box should be restored to 55±2℃ within 15 minutes after the specimen is immersed. During the entire curing period, the water temperature in the box should be maintained at 552℃.
During the entire curing period, the curing water temperature must be continuously or regularly measured and recorded
The specimen is cured in 55±2℃ warm water for 23 hours±15 minutes. Take out the molded specimen, demould it, and let it stand at room temperature to cool for a total of 1 hour ± 10 minutes. Then, when the specimen age is 25 hours ± 15 minutes, carry out a compression test according to the method specified in the relevant standards to measure its accelerated curing strength. Engineering Construction Standard Full-text Information System
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Chapter 4 Concrete Strength Relationship
Establishment and Estimation of Strength
Article 4.1 When using the accelerated curing wet concrete specimen strength to estimate the standard curing strength of 28 days (or other age), a special test should be conducted to establish the strength relationship between the two.
Article 4.2 When preparing concrete of different grades, the linear regression method is used to establish the strength relationship:
R=A+BR
(4-1)
When preparing concrete of a single grade, the conversion coefficient method can be used to establish the strength relationship:
Where:
(4-2)
R--the estimated value of the strength of the concrete specimen after standard curing for 28 days (or other ages) (kg/cm2); bZxz.net
R--the measured value of the strength of the concrete specimen after accelerated curing (kg/cm2)
A, B, K--coefficients, calculated according to the provisions of Appendix 1. Article 4.3 When conducting special tests to establish the concrete strength relationship, the same raw materials as the project should be used to make the specimens. The slump or working degree of the sample mixture should be similar to that used in the project. Two groups of specimens should be formed into a pair of concrete specimens. One group should be subjected to accelerated maintenance according to the provisions of this standard and the accelerated differential strength should be measured; the other group should be subjected to standard maintenance according to the relevant standards and the 28-day engineering 6 construction standard full text information system
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