Ultrasonic pulse echo testing has been proven to be complementary to other NDT techniques. The leading products by Proceq help to identify defects that are not detectable e.g. with radar or eddy current tests. In particular, deep scanning of walls and linings, finding of deep and second or third layer rebars and tendon duct analysis deliver unrivalled results compared to other techniques. However, the case studies presented in this paper also highlight some of the issues that need to be looked at in order to increase the value of on site pulse echo testing. Scanning speed has been one key issue that has been partially addressed through the introduction of real time B-scan imaging incl. an immediate onboard feature to create panoramic scan images out of individual scans. It has also been recognized that 3D imaging and variable slicing of the scan data help a great deal in visualizing the structural features. A few recent advancements have been laid out in this paper, however, the authors realize that further steps are needed to fully explore the power of this NDT technology. One further step in this is use artificial intelligence positioning systems and improved image stitching to expedite and ease on-site usage of the system. Also an onboard data interpretation system is underway and ready for release to the markets, which can be particular helpful when the initial test reports are already created on-site. Finally, an on-site 3D analysis will be introduced into the next generation of instruments as well to bring ultrasonic pulse echo testing of concrete structures to the next level.

1. A practice-driven approach to the
development of the ultrasonic pulse echo
technique applied to concrete structural
assessment
15th Asia-Pacific Conference for Non-Destructive Testing (APCNDT2017)
Singapore, November 14, 2017
D. Corbett, F. Gattiker, S. Vonk, A. Taffe, L. Raj*
Proceq SA, Proceq Asia Pte Ltd., HTW Berlin
© Proceq 2017-2018 1

2. 1
Overview
Large-scale scanning
Research on cover depth
Tendon duct analysis
Tendon duct analysis
© Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 2
2
3
4 Conclusions4

3. 1
Overview
Large-scale scanning
Research on cover depth
Tendon duct analysis
Tendon duct analysis
© Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 3
2
3
44 Conclusions

4. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 4
One major drawback of pulse echo testing is the
total effort required for large-scale scanning
• Large-scale project
(shopping mall)
• Repeated scanning of
column & beam structures

5. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 5
The task was to detect grouting defects in
couplers that could weaken the structure
Horizontal scanning with Pundit 200PE
single-channel pulse echo instrument
Horizontal test
of coupler
assembly
Vertical
direction of
each coupler
test

6. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 6
Pulse echo works well to detect voids, but
requires numerous measurements
Typical vertical scan
• Voids in the coupler section
• At depth: 10 cm
• Length: 30 cm
• 32 individual measurements

7. 460
scans
32 measurements
per scan× 13’800 individual
measurements=
© Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 7
There is a clear need to improve scanning speed and reduce total effort.
The effort involved in collecting data for one
section on-site is considerable
84
columns
4 scans
per column× + 40
beams
3 scans
per beam× 460
scans=

8. Single-channel transducer 8-channel array transducer
© Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 8
A practical solution to improve scanning speed is
to switch to an array
Image built up in small increments
on the display device
B-scan presented in real time directly
on the display device

9. Single-channel transducer 8-channel array transducer
© Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 9
Switching to an array reduces the scanning effort
by a factor of 15
64 measurements → 2 minutes 37 seconds
13’800 individual measurements per section
4 measurements → approx. 10 seconds
920 individual measurements per section

10. 1
Overview
Large-scale scanning
Research on cover depth
Tendon duct analysis
Conclusions
© Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 10
2
3
4 Conclusions4

11. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 11
Research on pulse echo showed discrepancies in
measured cover depth above reinforcing steel
• Pulse velocity calibrated against known
back wall depth
• Individual rebars and a hollow pipe are
clearly visible
• Discrepancies of cover depth of about
10% were noted
• Research carried out at University of Applied
Sciences Rapperswil in Switzerland
• Pulse echo could be used to determine concrete
cover in fiber-reinforced concrete
Proceq Pundit 250 Array with multichannel technology,
real-time B-scan with image stabilizer

12. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 12
Dedicated test blocks to investigate detection
capabilities of latest array transducers
• Ongoing investigations /
research project
• University of Applied
Sciences in Berlin
30 × 20 × 150 cm | Ø 16 mm reinforcing bars at increasing cover depth (5 zones)

13. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 13
Image-stitched panorama B-scan of test block
reveals cover discrepancies
Scan with Pundit 250 Array
transducer (8 channels)
• 21 cm wide scan,
18 cm overlap (stitching)
• Data analysis with
Proceq PL-Link software
Zone 1 2 3 4 5
Actual cover [cm] 1.2 3.0 5.0 7.0 9.0
Detected cover [cm] 4.0 4.4 6.8 8.7 9.5

14. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 14
Resolution at shallow depths improved
significantly by reducing pulse velocity

15. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 15
Depth estimation depended on pulse velocity, but
reasons are unclear
• Unclear whether / why:
 Pulse velocity varies
throughout test block
 Pulse velocity lower
near the surface
• Root cause currently
being investigated
0
4
8
12
16
20
RB1 (1.2 cm) RB2 (3.0 cm) RB3 (5.0 cm) RB4 (7.0 cm) RB5 (9.0 cm) Back wall (20 cm)
Depthestimation[cm]
Depth estimation depending on pulse velocity c [m/s]
2200
2400
2600
2700

16. 1
Overview
Large-scale scanning
Research on cover depth
Tendon duct analysis
Tendon duct analysis
© Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 16
2
3
4 Conclusions4

17. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 17
Routine destructive maintenance revealed
grouting defects in tendon ducts
Brent Cross Flyover
(London)

18. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 18
Can grouting duct failures be analyzed using
pulse echo technology?
Duct with
known void
Healthy
duct
Tendon ducts located
with GPR and openings

19. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 19
Comparison of B-scans shows that pulse echo
can detect the presence of voids
Data collected with
Proceq Pundit 250 Array
DUCTDUCT
BACK WALL
BACK WALL
Very strong echo Weak echo
with secondary echo
Duct with known void Healthy duct

20. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 20
A post-processed C-scan comparison obviously
differentiates healthy and unhealthy ducts
C-scan generated from B-
scans across the duct
• Raw data export
• External software
Duct with known void Healthy duct
B-scans
On-board C-scan feature would
accelerate on-site analysis

21. 1
Overview
Large-scale scanning
Research on cover depth
Tendon duct analysis
Tendon duct analysis
© Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 21
2
3
4 Conclusions4

22. © Proceq 2017-2018 Practice-driven approach for the development of ultrasonic pulse echo for concrete structural assessment 22
Technological
progress
Contribution to
NDT inspections
Key drivers of
improvement
Taking a look at challenging applications drives
us to constantly improve pulse echo technology
• Real-time on-board B-scan imaging
• C-scanning functionality desirable
• Detects grouting defects
• Complementary to GPR, Eddy Current
• Speed of on-site testing
• Ease of data interpretation
• Calibration accuracy
• Position/stitching accuracy
Proceq Pundit 250 Array / Pundit Live Array Pro