What is Impact echo testing?
Impact echo is an advanced non-destructive test technique used to identify geometrical information and locate internal defects in concrete members based on accurate measurement of the surface motion resulting from a mechanical impact.
How does Impact echo testing work?
Impact echo tests use stress waves generated by mechanical impacts to probe the structure of concrete elements and analyse the echo patterns returned to identify the presence and location of internal defects.
What is Impact echo testing used for?
Deterioration process | Defects | Control of repairs |
To correlate the deterioration process | In-situ quality control of concrete(voids), mainly in piles |
How do I carry out Impact echo testing?
The procedure to carry out Impact echo tests as specified in standards such as ASTM C1383-15 (2022) is described in the list below and the process and schematics are illustrated in figure 2.
Ensure the concrete surface is clean and accessible.
Position the impact echo device on the surface.
Use a small hammer or the device's built-in impactor to create stress waves in the concrete.
Record the echo patterns produced by the stress waves as they reflect off internal features or flaws.
Use software to analyse the echo patterns to identify flaws like cracks, voids, or delamination based on wave velocity and return time.
Use this data to assess the condition of the concrete, identifying areas that may require repair or further investigation.
What equipment and expertise are required for Impact echo testing?
In the UK, there are several brands and suppliers of impact echo testing systems such Impact Echo Instruments or Proceq and various models are differentiated based on specific requirements such as the type of concrete structure to be tested, the depth of analysis required and level of portability.
The expertise required to analyse the results from impact echo tests is significant and could limit test availability due to lack of operatives with the specific training required, especially in rural or non-urban areas.
What are the advantages of Impact echo testing?
Leaves no damage.
Simple, repeatable, and relatively rapid test.
Suitable for a wide range of concrete structures.
Can accurately detect a wide range of different defects.
What are the disadvantages Impact echo testing?
Accuracy of results can significantly depend on the operator's skill and experience.
Complex structures may produce echo patterns that are difficult to interpret accurately without extensive experience.
Proper equipment calibration is crucial for accurate measurements, and any deviation can lead to incorrect conclusions about the concrete's condition.
How accurate is Impact echo testing?
Impact echo (IE) testing, in its most commonly used form without the integration of advanced methodologies like semi-supervised learning or finite element simulations, has demonstrated varying degrees of accuracy depending on the specific conditions and applications.
In practice, the accuracy of IE testing for detecting flaws and assessing concrete integrity can be high, when conditions are ideal, such as applications with clear boundaries, uniform material properties, and minimal interference from rebar or other embedded objects.
In real-world scenarios, IE testing faces challenges like inaccuracies due to complex conditions, such as the scattering of stress waves by reinforcing bars and alterations in wave speed by environmental factors.
Recent advancements aim to enhance IE testing's accuracy. Studies show that semi-supervised learning (SSL) increases accuracy by 7-8% over traditional methods, particularly for detecting delamination, by leveraging dynamic behaviour analysis (Young-Geun, Y. et al 2022). Another approach addresses IE's sensitivity to edges by combining cross-sectional vibration modes with IE, significantly improving detection accuracy near concrete edges through field tests and simulations (Yunlin, L et al 2023).
What are the limits of Impact echo testing?
Impact echo (IE) testing's effectiveness is limited by structural geometry and material properties, requiring parallel and smooth surfaces for accurate wave reflection and sensor stability.
Its applicability is also constrained by material thickness, influenced by velocity, damping, and shock magnitude. Additionally, environmental factors like moisture and temperature can affect sound speed, altering accuracy. Reinforcing bars close together may further complicate wave interpretation.
Despite these challenges, IE testing remains a key non-destructive evaluation method, with ongoing advancements seeking to mitigate these limitations.
Ancillary information
Maturity of test: >10 years
Qualification & interpretation : Inspector and specialist
Service disruption: No
Preliminary works: Yes
Time consumption Low (< one hour)
Cost Medium
Access to element 1 face
References and further information