INSPECTING AND PRESERVING INFRASTRUCTURE THROUGH

ROBOTIC EXPLORATION

3D Microwave “Camera” for Concrete Delamination and Steel

Corrosion DetectionM. Dvorsky, S. Barker, M.T. Ghasr and R. Zoughi

Applied Microwave Nondestructive Testing Laboratory (amntl)Electrical and Computer Engineering Department

Missouri University of Science and Technology (S&T)August 2018

Objectives & Rationale• Use microwave imaging technique, based on

synthetic aperture radar methods, to detect:delamination, and successive corrosion of reinforcing steel bars in

concrete members.• Microwave signals penetrate inside of

dielectric materials.• Sensitivity to material property variation.• Ability to collect scanned data and create

relatively high-resolution images of interior of objects.

- & mm-Wave Spectra

1000 mm 1 mm10 mm

300 MHz 300 GHz30 GHz

-Waves mm-Waves

Q-Band33-50.5

V-Band50-75

W-Band75-110

Ka-Band26.5-40

D-Band110-170

X-Band8.2-12.4

Ku-Band12-18

K-Band18-26.5

Why - & mm-Wave NDT&E• Limitation associated with “standard”

techniques.• These signals penetrate into dielectric

materials, and composites. • Sensitive to dielectric property variation:

abrupt (boundaries) local (inclusions)gradual (gradient in material change).

• Polarization, frequency, measurement parameter (near-field vs. far-field) & probe type diversity-degrees of freedom.

• Sensitive to conductor surface properties.

Why - & mm-Wave NDT&E• Coherent properties – magnitude & phase.• Large available bandwidth.• Life-cycle inspection possibilities.• Electromagnetic modeling (analytical,

numerical and empirical).• On-line and real-time inspection.• Operation in industrial environments.• Little to no need for operator expertise.• Relatively inexpensive.

Synthetic Aperture Focusing

Probe RealAntenna

Flaw or Target

Composite under Inspection

Synthesized Antenna Length

Direction of Motion or Scan

R1 R2 R3 R4 R5

AntennaBeamwidth

h

SAR 2D Measurement

h

Aperture

Sample Under Test

∆x

∆y

7

Mortar Sample – Metal Thinning

12” x 12” x 5”(305 mm x 305 mm x 127 mm)

Mortar Sample – Metal Thinning

~100 mm

~25 mm

~125 mm

Shallow

Deep

~125 mm

Imaging Results

Prespective View

Side View

Imaging Results

(2.6)

X-band Ku-band K-band

Mortar Sample – CorrosionGrinded Area Filled with Rust @ One as Reference

50 mm

75 mm

12” x 7.5” x 5”(305 mm x 190 mm x 125 mm)

Imaging ResultsImage Slices

X-band Ku-band K-band

x (mm)

y (m

m)

0 50 100 150 200 250 3000

50

100

150

200

250

1

2

3

4

5

6

7

8

Concrete Samples: 1” Cover Un-Corroded Corroded

J-Band (5.85-8.2 GHz)

S16

Slide 14

DBS16 consider making the row sizes consistent in the table.

Consider rewriting bullet 2

consider swapping bullets 2 and 3pdsc003, 2/5/2013

Concrete Samples: 1” Cover Un-Corroded Corroded

Ku-Band (12.4-18 GHz)x (mm)

y (m

m)

0 50 100 150 200 250 3000

50

100

150

200

250

0.5

1

1.5

2

2.5

S16

Slide 15

DBS16 consider making the row sizes consistent in the table.

Consider rewriting bullet 2

consider swapping bullets 2 and 3pdsc003, 2/5/2013

Concrete Samples

J-Band (5.85-8.2 GHz)

Size & Uniform Corrosion

J-Band (5.85-8.2 GHz)

Non-Corroded Corroded

8”-Thick Concrete Slab

SAR 3D Image

SAR 2D Image Slices

60 mm 100 mm

50 mm

Pedestrian Bridge

Initial Results

Depth of ~50 mm

Summary & Future Activities• Potential for using microwave signals for

imaging of delamination and rebar corrosion is high.

• Successive corrosion of concrete samples will indicate possibility of detecting level of damage.

• New samples with delamination will be prepared and tested.

• Optimal frequency range will be determined.• Testing of the pedestrian bridge will continue.• Will initiate array design for 1D imaging.

Acknowledgement• This project was partially funded by the

INSPIRE University Transportation Center (UTC). Financial support for INSPIRE UTC projects is

provided by the U.S. Department of Transportation, Office of the Assistant Secretary for Research and Technology (USDOT/OST-R) under Grant No. 69A3551747126 through INSPIRE University Transportation Center (http://inspire-utc.mst.edu) at Missouri University of Science and Technology. The views, opinions, findings and conclusions reflected in this publication are solely those of the authors and do not represent the official policy or position of the USDOT/OST-R, or any State or other entity.