What is Pulse echo testing?
Pulse echo testing is a non-destructive test technique used to identify information such as element thickness and defect location by mapping concrete structures using ultrasonic waves.
How does Pulse echo testing work?
Pulse echo testing in concrete uses ultrasonic waves to detect internal defects and measure geometrical information about concrete elements by measuring the time for echoes to return from anomalies or boundaries within the material.”
What is Pulse echo testing used for?
Deterioration process | Defects | Control of repairs |
To correlate the deterioration process with internal concrete voids | Thickness measurement | In-situ quality control of concrete(voids) |
How do I carry out Pulse echo testing?
While specific standards dedicated exclusively to pulse echo testing in concrete do not exist, methodologies related to ultrasonic testing, often encompass principles applicable to pulse echo techniques.
Instead, BS EN 12504-4 and ASTM C1383 standards which provide guidelines for measuring ultrasonic pulse velocity, not pulse echo, in concrete are commonly used.
These standards, focusing on setup, procedure, and analysis, are also relevant to pulse echo testing due to the similarities between the tests. Figure 3 shows a schematic of the test set up and expected return signals.
The procedures proposed in these standards as shown below give general guidance but for specific pulse echo methods, consult manufacturer guidelines and relevant standards, as practices can vary by equipment and testing objectives.
Ensure the concrete surface is clean and accessible.
Calibrate the pulse echo equipment according to the manufacturer's instructions.
Choose the appropriate transducer frequency based on the expected depth of investigation and resolution required.
Set up the pulse echo device, adjusting settings like gain and damping as needed.
Place the transducer on the concrete surface.
Use a couplant (e.g., gel or water) to ensure good acoustic contact between the transducer and the concrete.
Trigger the device to send ultrasonic pulses into the concrete.
Record the time it takes for echoes to return from internal anomalies or the back wall.
The recorded signals must then be analysed to identify defects by interpreting the time-domain signal or analysing the frequency spectrum in order to estimate the location and size of detected features. Figure 4 illustrates a concrete element with small sub surface defects and shows the results of the Pulse echo test after software analysis. From this display the number, location and size of defects can be easily identified and suitable repair strategies implemented.
What equipment and expertise are required for Pulse echo testing?
Systems for pulse echo testing of concrete are available from several manufacturers such as Proceq, James Instruments, and ELE International, each offering unique features tailored for concrete assessment and providing comprehensive solutions and support for their systems, ensuring accurate assessments of concrete integrity.
These systems however also require expertise in sonic test principles and data interpretation to accurately identify and analyse defects, thickness, and homogeneity within concrete structures. Professionals typically need a background in civil engineering or a related field with specialized training in non-destructive evaluation techniques which may limit the adoption of these methods in rural or non-urban environments
What are the advantages of Pulse echo testing?
Can be carried out by a single operator.
Rapid data acquisition with large areas covered quickly.
No defects left by the test.
Effective for identifying voids, cracks, element thickness and composition.
What are the disadvantages of Pulse echo testing?
Unable to detect near surface anomalies consistently.
Complex signals can be difficult to correctly interpret.
Accuracy of results can be affected by presence of rebar etc.
Skilled operators are required for data analysis.
How accurate is Pulse echo testing?
The accuracy of Pulse echo testing can be affected by challenges related to signal complexity and requires parallel, smooth, debris free, concrete surfaces for maximum accuracy. This method accurately identifies the types and size of defects underneath the concrete surface, with length resolution of 1-5 cm and thickness resolution of 0-3 cm. This allows accurate evaluation of internal concrete, ensuring reliable assessments of structural integrity.
Recent research has shown that Pulse echo test accuracy can be further enhanced by machine learning, which through more complex and efficient data analysis helps overcome challenges related to signal complexity and allows accurate testing of members with complex geometry or surface features.
What are the limits of Pulse echo testing?
This test requires parallel, debris free concrete surfaces for accurate testing and therefore may not be suitable for use in all structures.
Data analysis for elements with complex geometry can become extremely difficult with the signals produced by echoes from defects becoming hard to identify against a complex background of sound waves bouncing back from the elements changing geometry.
Ancillary information
Maturity of test: < 5 years
Qualification & interpretation : Specialised lab
Service disruption: No
Preliminary works: Yes
Time consumption Medium (one day)
Cost Medium
Access to element 2 faces
References and further information