What is Acoustic emission testing of concrete?
Acoustic emission testing uses the release of ultrasonic stress waves to identify defects in materials. Small sensors are mounted onto the structural element to be monitored and convert stress waves from crack formation, elongation and widening into electrical signals allowing and detection of active damage, in real time, inside concrete elements.
How does Acoustic emission testing work?
Acoustic emission (AE) is the occurrence of sound and ultrasound radiation in materials that undergo fracture processes and crack propagation. These acoustic waves are recorded by an AE system during monitoring and can be used in a passive way.
AE can be used to identify the occurrence and location of damage within the monitoring period, e.g., the occurrence of a crack in concrete. The system consists of a series of sensors (mainly piezoelectric) placed at defined locations on the surface of structural element being inspected.
What is Acoustic emission testing used for?
Deterioration process | Defects | Control of repairs |
To correlate the deterioration process | - |
How do I carry out Acoustic emission testing?
BS ISO 16837:2019 and ASTM E3100-17 provide similar, comprehensive frameworks for conducting AE tests on concrete structures using the basic process outlined below.
Identify the areas to be monitored and ensure the surface is clean and accessible for sensor attachment.
Attach sensors at predetermined locations to ensure comprehensive coverage.
Connect sensors and calibrate the system.
Carry out a baseline measurement.
Begin continuous or periodic monitoring of return sound waves compared with the established baseline to identify any changes from active defects.
Analyse the data to identify patterns and use software to pinpoint exact defect locations.
What equipment and expertise are required for Acoustic emission testing?
Many commercially available acoustic emission test devices are available in the UK from suppliers such as Physical Acoustics or Innerspec, however, the expertise required to analyse the data may limit the widespread availability of this test method.
What are the advantages of Acoustic emission testing?
Allows real time, early detection of damage reducing the risk of severe failures.
Capable of accurately assessing faults within intricate structures.
Accurate defect localisation.
Enables remote monitoring of structures while in use, eliminating the need to halt operations for testing.
Pinpoints the exact location of damage for efficient repairs.
Leaves no defects.
What are the disadvantages of Acoustic emission testing?
Can be ineffective for detecting issues within thick materials due to sound wave limitations.
Requires skilled analysis for accurate results interpretation.
Significant setup and maintenance costs.
Background noise can interfere with the test and affect result accuracy.
How accurate is Acoustic emission testing?
Using expert data analysis internal defects can be located with an accuracy in the 0-1cm range.
What are the limits of Acoustic emission testing?
The accuracy of Acoustic Emission testing hinges on the capability to capture the high-frequency sound waves emitted by micro-cracks or other stress-related changes within the concrete and as such can only identify active flaws such as crack propagation.
Accuracy of results can be significantly limited by the effects of element configuration, the distance between sensors or background noise, excluding its usage in many environments with high noise levels. For accurate results these effects must be accounted for and expert analysis used to interpret the raw data which may not be easily available.
Acoustic emission is unlikely to be effective when used on extremely thick elements due to the limits of sound wave transfer through relatively insulative materials such as concrete.
Ancillary information
Maturity of test: >10 years
Qualification & interpretation : Inspector and specialist
Service disruption: No
Preliminary works: Yes
Time consumption Medium (one day)
Cost Medium
Access to element 1 face
References and further information