NDT ON CONCRETE STRUCTURES UNDER LOAD TESTS

Hazard: Extreme Loads

STUDENT: TODDRICK BROWN AIDICO’S MENTOR: JOSÉ VICENTE FUENTE

National Science Foundation: Hosted Institution: University:

Outline

OBJECTIVES: - The main purpose is to show the NDT applicability to characterize and explore the concrete structures. -The characterization involves NDT parameters, extracted for the tests, related with some properties of the concrete. In this action, we focused in load tests process and how to follow the NDT waves (ultrasonic & electromagnetic) in the load status. - The NDT exploration uses the ability to detect and locate inner defects (look inside). We focused on concrete cube (real scaled) placed in AIDICO’s facilities.

CONTENTS: - Introduction - Ultrasonic Background & Equipments - Ground Penetration Radar Background & Equipments - Experimental Results on Concrete Cube - Experimental Results for Load Test - Conclusions

NDT vs CONCRETE INTRODUCTION BOND TEST

CRACK METER

REINFORCED SURVEY

CRACK SCOPE

SONIC TEST

CORROSION TEST

MOISTURE TEST

ULTRASONIC TEST

CARBONATION LIQUIDS

MAGNETIC & EM SURVEY

Internal Defective locations in concrete

Available evaluation for Non-Destructive Testing on concrete

GPR

Applied NDT on Concrete

Characterization

Imaging

Ultrasonic for NDT on Concrete

ULTRASONIC TEST BACKGROUND:

- The UT techniques is based on the elastic/mechanical waves and the parameters that characterize the propagation.

- The propagation velocity is usually the desired parameter.

- Use a frequency contain of 30 – 150 kHz for concrete.

-There are some information test but should verified by alternative/destructive methods.

Ultrasonic for NDT on Concrete

ULTRASONIC TEST BACKGROUND:

4300 4400 4500 4600 4700 4800 4900 5000 51000

5

10

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25

Velocidades in-situ (m/s)

FUNCION GAUSSIANA DE AJUSTE PARA Vp IN-SITU

Vp_histog_2 vs. X_histog_2

fit 1

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40

50

60

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90

Velocidades en testigos

Resis

tencia

s a

com

pre

sió

n (

MP

a)

AJUSTE DE RC y VELOCIDADES EN TESTIGOS

Rc_testigos vs. Vp_testigos

Ajuste Potencial

Pred bnds (fit 2)

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45

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Velocidad in situ (m/s)

Rc (M

Pa)

AJUSTE DE RC Y VP INSITU

Rc_para_Vp_insitu vs. Vp_insitu_paratestigos

Ajuste Potencial

Pred bnds (fit 3)

8 2.47

2

( ) 5.4 10 ( / )

0.73

pRc MPa V m s

r

7 2.219

2

( ) 4.7 10 ( / )

0.84

pRc MPa V m s

r

Imaging Tests / Methods

The MIRA is an ultrasonic tomography device for diagnostics of concrete structures, detecting and evaluate internal reinforced concrete defects such as honeycombs and voids.

Information on MIRA

The ultrasonic testing is one of the most advanced techniques available in non-destructive testing concrete, especially for large structures.

Information on MIRA (cont.)

An array of 10 channels of 4 transducers resulting in scanning aperture of 400 mm by 50 mm.

It utilizes 40 transmitting and receiving probes measuring within less than 3 seconds.

Scans results in a 2D depth. Also known as the b-scan

Imaging Tests / Methods

Information on MIRA (cont.)

Methods

Ground Penetration Radar (GPR) is a geophysical prospecting method for non-destructive studies that is uses high frequency electromagnetic waves to image the subsurface structure.

The wave velocity depends on the changes in the dielectric constant of the medium

Has one of the highest resolutions in subsurface imaging

GPR for NDT on Concrete

Methods

The GPR shows images of the scanned subsurface area on the SIR 3000 of large and small concrete element structures.

Its a series of pulses over a single area that make up an scan. Its called a radar gram.

The strength, or amplitude, of the reflections are determined by the dielectric constants and the two materials

GPR for NDT on Concrete

Methods

Radar energy emits in an cone shape.

The two-way travel time for energy at the leading edge of the cone is longer than for energy directly beneath the antenna.

GPR for NDT on Concrete

When moved over a target, the distance between them decreases until the antenna is over the target & increases as its moved away.

Information on GPR (cont.)

Electromagnetic waves are radiated from the transmitter into the structure.

Buried objects/boundaries causes part of the waves to bounce back to the receiver.

Concrete Cube in AIDICO The GPR and MIRA

z

x

y (0,0,0)

Cara CCara D

Cara BCara A

z

x

y (0,0,0)

Cara CCara D

Cara BCara A

Cara CCara D

Cara BCara A

Cara CCara D

Cara BCara A

z

x

y

The GPR and MIRA works good together in NDT and gather information and results more effectively. Collects vertical and horizontal resolutions, penetration depth and more.

Results of MIRA Concrete cube

Results of GPR Concrete cube

Experimental Results for Loading Tests

Load Machine Flexural Test

EN 83509: 2004 GPR antenna

Ultrasonic transducer

Experimental Results for Loading Tests (cont.)

BSCANs of the FPP1 Probe during the loading flexural test

Time of load test (s)

Tim

e o

f F

light

of

each A

-Scan (

s)

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0.02

0.04

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0.08

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0.18

0.2

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4350

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4500

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4600

4650Velocity Evolution on FPP1 durting the load flexural test

Time of load test (s) A-Scan each 5 s

Velo

citie

s o

f P

-wave (

m/s

)

FPP1: Polypropilene Fiber reinforced concrete Z1 Z2 Z3

Z1 Z2 Z3

Experimental Results for Loading Tests (cont.)

Tiime of load test (s) A-Scans each 5s

Tim

e o

f F

lisht

A-S

cans (

s)

BSCANs Evolution of the FPP2 Probe during the load flexural test

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Time of load Test (s) A-Scan each 5 s

velo

city o

f P

-Wave (

m/s

)

Velocity Evolution of FFP2 during the load flexural test

FPP2

Z1 Z3

Z1 Z3

Experimental Results for Loading Tests

FPP3

Tiime on th Load Test (s) A-Scans each 5 s

Tim

e o

f F

light

(s)

A-S

can

BSCANs Evolution of the FPP3 Probe during the load flexural test

50 100 150 200 250 300 350 400

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

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4800

Time on load test (s)

Velo

city o

f P

-wave (

m/s

)

Velocity Profile of FPP3 during the load test

Z1 Z2

Z2 Z1

GENERAL CONCLUSIONS

The right combination of NDT can provide useful information. NDT are most qualitative for inspection elements and should be added to other complementary destructive test

In other topics/sectors, NDT are most confident and reliable than construction. There is a lack of knowledge on that point.

The technical advance can provide new equipments and methodologies to reduce this gap.

Conclusions

GRACIAS POR SU ATENCIÓN THANK YOU FOR YOUR ATTENTION

SPECIFIC CONCLUSIONS

Ultrasonic Velocity does not give us the current stress/strain status along the

load process, at least in a flexural test.

Ultrasonic Test gives us information about the cracking process (crack growthing)

GPR can be used for rebar concrete reconstruction but cannot detect lower spheres

MIRA detects worse the geometry but can be detect lower targets.