CECS : 21-2000 Technical specification for ultrasonic detection of concrete defects CECS21:2000

CECS: 21-2000 Technical Specification for Ultrasonic Detection of Concrete Defects CECS21:2000 CECS:21-2000 Standard download decompression password: www.bzxz.net

CECS 21:2000bzxZ.net
Standard of China Association for Engineering Construction Standardization
Technical specification for inspection ofconcrete defects by ultrasonic method2000
Standard of China Association for Engineering Construction Standardization
Technical specification for inspection ofconcrete defects by ultrasonic methodCECS 21:2000
Editing unit: Shaanxi Institute of Architectural Science Research and Design Tongji University, Shanghai
Approving unit: China Association for Engineering Construction Standardization Implementation date: January 1, 2001
This standard is formulated in accordance with the requirements of the letter No. 08 of China Association for Engineering Construction Standardization (98) on issuing the plan for the compilation of the first batch of recommended standards in 1998. This regulation is revised on the basis of the Technical Regulation for Ultrasonic Testing of Concrete Defects CECS 21:90, absorbing the latest achievements of ultrasonic testing instruments and new experiences of ultrasonic testing technology at home and abroad, and combining with the actual needs of concrete quality control and testing in my country's construction projects.
The main contents of this regulation include the scope of application of ultrasonic testing of concrete defects, the technical requirements of testing equipment, acoustic parameter measurement methods, detection and judgment methods of concrete crack depth, concrete non-dense area, the combination quality of new and old concrete, and the detection and judgment methods of cast-in-place and steel tube concrete defects.
This regulation mainly makes comprehensive revisions to the two chapters of "Ultrasonic Testing Equipment" and "Acoustic Parameter Measurement": the original two chapters of "Shallow Crack Detection" and "Deep Crack Detection" are merged into one chapter of "Crack Depth Detection"; the chapter of "Homogeneity Detection" is deleted; the methods of determining the depth of horizontal cracks, judging abnormal data of concrete density detection, and data processing of surface damage layer detection are supplemented and improved; and the detection of cast-in-place piles and steel tube concrete defects is added. The association standard "Technical Specification for Ultrasonic Detection of Concrete Defects" is now approved, numbered CECS21:2000. It is recommended for use by engineering construction design, construction, and user units. This specification is managed by the Concrete Structure Committee of the China Engineering Construction Standardization Association and interpreted by the Shaanxi Provincial Building Science Research and Design Institute (No. 272, North Section of Huancheng West Road, Xi'an, Shaanxi Province. Postal Code: 710082). If you find any need for modification and supplementation during use, please send your opinions and information directly to the interpretation unit.
Shanghai Tongji University
Participating units: Structural Research Institute of China Academy of Building Research, Ministry of Water Resources and Electric Power, Nanjing Hydraulic Research Institute, Beijing Construction Engineering Quality Inspection Center, Third Inspection Institute, Chongqing Construction Science Research Institute
Main drafters: Zhang Zhitai
Li Naiping/Li Weidu
Zhang Renyu
Luo Qixian?Pu Cunting
Lin Weizheng
Lin Wenxiu
China Association for Engineering Construction Standardization
November 10, 2000
Terms and symbols
Main symbols
Ultrasound Wave detection equipment
Technical requirements for ultrasonic detectors·
Technical requirements for transducers…
Calibration of ultrasonic detectors·
Acoustic parameter measurement
General provisions·
Acoustic parameter measurement
Crack depth detection
General provisions·
Single-sided flat measurement method
Double-sided oblique measurement method
Drilling measurement method
Uncompacted area and cavity detection
General provisions
Test method
Data processing and judgment
Concrete joint surface quality detection| |tt||-General provisions
Test methods
Data processing and judgment
Surface damage layer detection·
Test methods
Data processing and judgment
Ground pile concrete defect detection
-General provisions
Buried ultrasonic detection tube
Preparation before detection,
Detection methods
Data processing and judgment
Steel tube concrete defect detection
Appendix A
Appendix B
Appendix C
General provisions
Detection methods·| |tt||Data processing and judgment··
Measurement of air sound velocity for acoustic time measurement Initial reading of radial vibration transducer acoustic time (too) Method for estimating the size of voids
Terms used in this specification
1 General
1.0.1 This specification is formulated to unify the detection procedures and test judgment methods for ultrasonic detection of concrete defects and to improve the reliability of the detection results. 1.0.2 This specification is applicable to ultrasonic detection of concrete defects. 1.0.3 Defect detection refers to the detection of the location and range of the voids and uncompacted areas inside the concrete, the depth of the cracks, the thickness of the surface damage layer, the quality of the concrete bonding surface poured at different times, and the defects in cast-in-place piles and steel tube concrete. 1.0.4 Ultrasonic method (ultrasonic pulse method) refers to the use of ultrasonic detectors with waveform display function to measure the acoustic parameters such as the propagation speed of ultrasonic pulse waves in concrete (referred to as sound speed), the amplitude of the first wave (referred to as amplitude) and the main frequency of the received signal (referred to as main frequency), and judge the defects in concrete based on these parameters and their relative changes. 1.0.5 When defect detection is carried out in accordance with this regulation, it shall also comply with the provisions of the relevant national mandatory standards in force.
2 Terms and symbols
2.1 Terms
2.1.1 Ultrasonic method The ultrasonic method referred to in this regulation is a method of using a low-frequency ultrasonic detector with waveform display and a sound wave transducer with a frequency of 20 to 250kHz to measure the acoustic parameters such as the sound speed, amplitude and main frequency of concrete, and analyze and judge the defects of concrete based on these parameters and their relative changes.
2.1.2 Concrete defects are the loose areas, voids, cracks or inclusions of mud, sand and other debris that destroy the continuity and integrity of concrete and reduce the strength and durability of concrete to a certain extent. 2.1.3 Velocity of sound
The distance that the ultrasonic pulse wave propagates in concrete per unit time. 2.1.4 Amplitude
The amplitude of the first wave signal received by the receiving transducer and displayed by the ultrasonic instrument after the ultrasonic pulse wave passes through the concrete.
2.1.5 Attenuation
When the ultrasonic pulse wave propagates in concrete, as the propagation distance increases, the sound pressure caused by factors such as scattering, absorption and sound beam diffusion weakens. 2.1.6 Main frequency
The frequency value with the largest amplitude in the amplitude distribution of each frequency component of the received ultrasonic pulse wave.
2.2 Main symbols
A-the amplitude of the first wave of the received signal at the measuring point i; hc-the depth of the concrete crack;
hf-the thickness of the concrete damaged layer;
d,-the diameter of the drilled acoustic testing hole or the inner diameter of the pre-prepared acoustic testing pipe; d2-the outer diameter of the pre-buried acoustic testing pipe;
f-the main frequency of the received signal at the measuring point i;
l;-the ultrasonic test distance of the measuring point i;
{'-the distance between the inner edges of the transmitting and receiving transducers during flat measurement; mx, s-the average value and standard deviation of a certain acoustic parameter x of concrete respectively; m,, S,一 are the average value and standard deviation of the concrete sound velocity; T is the Celsius temperature of air;
T is the first wave period of measuring point i;
t; the measured sound time value of measuring point i;
tci is the concrete sound time value of measuring point i;
t. The initial reading of the sound time;
t is the measured sound time value of measuring point i during the horizontal measurement across the seam; t. The initial reading of the sound time tested in the borehole or pre-buried pipe; th is the sound time value of bypassing the cavity;
is the standard value of the air sound velocity;
is the measured value of the air sound velocity;
is the sound velocity of the damaged layer concrete;
v is the sound velocity of the undamaged concrete;
uu is the sound velocity in the measured water;
X is a certain acoustic parameter value of measuring point i;
X is the judgment value of the abnormal situation of the acoustic parameter. 3
Ultrasonic testing equipment
Technical requirements for ultrasonic detectors
3.1.1Ultrasonic detectors for dry concrete are divided into the following two categories. 1Analog type: The received signal is a continuous analog quantity, and the acoustic parameters can be measured and read by the time domain waveform signal;
2Digital type: The received signal is converted into a discrete digital quantity, and has the intelligent functions of collecting and storing digital signals, measuring and reading acoustic parameters, and processing digital signals. 3.1.2Ultrasonic detectors should comply with the requirements of the current relevant national standards and be used within the validity period of the statutory metrological verification.
The ultrasonic detector should meet the following requirements: 1
An oscilloscope device with clear waveform and stable display; 2
The minimum division of the sound time is 0.1us;
An attenuation system with a minimum division of 1dB; 4
The frequency response range of the receiving amplifier is 10~500kHz, the total gain is not less than 80dB, and the receiving sensitivity (when the signal-to-noise ratio is 3:1) is not more than 50uV; 5
The power supply voltage fluctuation range can work normally when it is within the nominal value ±10%; 6
The continuous normal working time is not less than 4h.
For analog ultrasonic detectors, the following requirements should also be met: It has two sound time reading functions: manual cursor and automatic shaping; 1
The digital display is stable. The sound time is adjusted in the range of 20~30 us, and the digital change is not more than ±0.2 us for 1h.
3.1.5 The digital ultrasonic detector should also meet the following requirements: 1. It has manual cursor reading and automatic reading modes. When automatically reading, under the same test conditions, the difference in sound time reading every 5 minutes within 1 hour should not be greater than ±2 sampling points;
2 The waveform display amplitude resolution should not be less than 1/256, and it can display and store 4
4kbytes;
3 In the automatic reading mode, there should be a cursor on the displayed waveform to indicate the reading position of sound time and amplitude:
4 It is advisable to have an amplitude spectrum analysis function (FFT function). 3.2 Technical requirements for transducers
3.2.1 Commonly used transducers have two types: thickness vibration mode and radial vibration mode: they can be selected according to different test needs.
3.2.2 The frequency of the thickness vibration transducer should be 20~250kHZ. The frequency of the radial vibration transducer should be 20-60kHz, and the diameter should not be greater than 32mm. When the received signal is weak, a receiving transducer with a preamplifier should be selected. 3.2.3 The difference between the measured main frequency of the transducer and the nominal frequency should not exceed ±10%. For transducers used in water, their water tightness should not leak under a water pressure of 1MPa. 3.3 Verification of ultrasonic detectors
3.3.1 The ultrasonic instrument sound time measurement test should measure the measured value v of the air sound velocity according to the "time-distance" method (see Appendix A), and compare it with the air sound velocity standard calculated according to formula (3.3.1). The relative error between the two should not exceed ±0.5%. v=331.41+0.00367.Tk
In the formula,
331.4 is the sound velocity of air at 0℃ (m/s); vc is the sound velocity of air at a temperature of Tk degrees (m/s); Tk is the temperature of the measured air (℃).
3.3.2 Measurement test of ultrasonic wave amplitude. The amplitude of the first wave displayed on the screen can be adjusted to a certain height, and then the attenuation of the instrument attenuation system can be increased or decreased by 6B. At this time, the height of the screen wave amplitude should be reduced by half or increased by one time. 5
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