NDT Labx - Transport3-CIVE1182

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Brenton Hale

s3166367


Non
-
Destructive Test


CIVE1173



Asset Management

Sujeeva Setunge


28
th

April 28, 2010



Introduction

The half
-
cell potential measurement is a non
-
destructive
electrochemical test commonly used to assess the severity
of corrosion in reinforced concrete.

Corrosion of steel reinforcement is a wide spread issue
affecting a multitude of infrastructure assets. The ability to
test for corrosion without compromising th
e integrity of the
asset is a valuable tool and the first step of rehabilitation.

Using this rapid, cost
-
effective, non
-
destructive survey allows
the collection of key information used to gauge the remaining
service life and aid in the repair of the concre
te.

The test consists of a voltmeter, the electrode and the test
item. In the case of our experiment we tested 6 separate
reinforced bars across two individual concrete sections. The
reinforcement was connected to an insulated cable within the
slab that w
as then linked to the voltmeter.

Using this set up we then proceeded to attain the voltage
potentials at 50mm spacing along the reinforcement.

Table of Contents

Non
-
destructive Tests

Half
-
Cell


Steel Potential



Results



Discussion



Accuracy of Results

Ultrasonic Pulse Velocity



Results



Discussion



Accuracy of Results

Cover Meter

Test



Results



Discussion



Accuracy of results

Half
-
Cell


Steel Potential Measurements

Brenton Hale

S3166367





Reinforcing Steel Bar used in
concrete.



28
th

April 2010


Results


Slab 1

(mV)

S2B2W1

S2B25W4

S2B21W3

1

-
170

-
198

-
190

2

-
172

-
200

-
192

3

-
168

-
201

-
194

4

-
168

-
200

-
197

5

-
171

-
203

-
199

6

-
171

-
202

-
200

7

-
177

-
202

-
194

8

-
176

-
202

-
194

9

-
174

-
202

-
195

10

-
171

-
202

-
196

11

-
169

-
209

-
208

Condition

Chance
of
corrosion

Moderate
chance
of
corrosion

Moderate
chance of
corrosion

Slab 2

(mV)

S1B17W1

S1B12W4

S1B8W7

1

-
32

-
48

-
51

2

-
40

-
42

-
49

3

-
50

-
62

-
53

4

-
47

-
59

-
48

5

-
46

-
49

-
45

6

-
60

-
56

-
51

7

-
62

-
53

-
59

8

-
53

-
64

-
60

9

-
54

-
53

-
56

10

-
66

-
57

-
53

11

-
60

-
52

-
52

Condition

Minimal
chance of
corrosion

Minimal
chance of
corrosion

Minimal
chance of
corrosion

Discussion

The results of the Half
-
cell test have shown a range of potentials from
-
32mV to
-
209mV. These test results indicate a higher possible corrosion
when a
higher negative potential is recoded.


Half
-
cell potential reading

Corrosion activity

less negative than
-
0.200 V

90% probability of no corrosion

between
-
0.200 V and
-
0.350 V

an increasing probability of corrosion

more negative than
-
0.350 V

90%
probability of corrosion


Slab two showed the least possibility of being affected by corrosion due
to the lower negative potential values. Slab one had much greater
negative potential values which is associated with a higher possibility of
corrosion.


Brenton Hale

S3166367




Accuracy of Results

Results can be affected by ma
ny factors such as:



Oxygen concentration



Carbonation



Chloride ion concentration



Epoxy coating and galvanised rebar



Dense concrete covers



Organic coatings and sealers



Cathodic protection systems and stray current

Situation

Half
-
cell

potential shift

Corrosio
n

of steel
reinforcement

Decrease in oxygen concentration

to negative

may not increase

Carbonation / decrease in pH

to negative

increase

Increase in chloride concentration

to negative

increase

Anodic corrosion inhibitor

to positive

decrease

Cathodic
corrosion inhibitor

to negative

decrease

Mixed corrosion inhibitor

to positive or negative

decrease

Epoxy
-
coated rebar

to positive

not related

Galvanized rebar

to negative

not related

Dense concrete cover

to negative

not related

Concrete resistance

to

positive

not related

Dry concrete

to positive

not related

Reference electrode position

to positive

not related

Coatings and sealers

to positive

not related

Stray current

Fluctuating between positive
and
negative

not related


28
th

April 2010



I do not believe that the results obtained by our testing were excessively inaccurate.
Many of the factors above were not present in our test situation and pose no ability to
affect the results. The testing methods used may have been less accurate that a
professional but were undertaken with the supervision of the lab technician.


The results seemed congruent with one another and there were no surprising spike in the
potential difference across the same reinforced bar section. The greatest variation was in

the reinforced member S1B17W1 which had a variation of
-
32mV to
-
66mV. This
difference is not great enough to question the test results and I remain confident that the
recorded values were accurate.

.

Brenton Hale

S3166367





Introduction

The method consists of measuring the time of travel of an
ultrasonic pulse passing through the concrete being tested.
Comparatively higher velocity
is obtained when concrete
quality is good in terms of density, uniformity, homogeneity
etc.


UPV



Ultrasonic Pulse Velocity Measurements

Brenton Hale

S3166367


28
th

April 2010


Results


Block 1

G7
-
S
-
1











Dimension 1

Dimension 2




0.2

m

0.12

m

top













Time

44

μs

42.6

μs



Distance

0.2

m

0.12

m



Velocity

4550

m/s

2820

m/s

middle













Time

48

μs

38.6

μs



Distance

0.2

m

0.12

m



Velocity

4170

m/s

3110

m/s

bottom













Time

56.6

μs

97.6

μs



Distance

0.2

m

0.12

m



Velocity

3530

m/s

1230

m/s

Block 2

AASS
-
0.75











Dimension 1

Dimension 2




0.2

m

0.12

m

top













Time

55.4

μs

33.8

μs



Distance

0.2

m

0.12

m



Velocity

3680

m/s

3550

m/s

middle













Time

53.4

μs

33.7

μs



Distance

0.2

m

0.12

m



Velocity

3760

m/s

3560

m/s

bottom













Time

56.2

μs

38.6

μs



Distance

0.2

m

0.12

m



Velocity

3560

m/s

3110

m/s

Block 3

AND1 S30











Dimension 1

Dimension 2




0.2

m

0.12

m

top













Time

43.5

μs

30.3

μs



Distance

0.2

m

0.12

m



Velocity

4600

m/s

3960

m/s

middle













Time

44.2

μs

31.6

μs



Distance

0.2

m

0.12

m



Velocity

4530

m/s

3800

m/s

bottom













Time

47.4

μs

30.4

μs



Distance

0.2

m

0.12

m



Velocity

4220

m/s

3950

m/s

* all block dimensions were 200mm x 200mm x 120mm

* equipment

calibrated to 20.5μs @ 130mm

Discussion

The results of the UPV test showed varying results with an overall
range of 1230m/s to 4600m/s. As the table shows, the higher the
velocity is the greater the quality of the concrete is.


This being the case we

see that block three, AND1 S30, had the
greatest velocity which indicates the block is of the best quality in
our test group.


Block one, G7
-
S
-
1, shows the lowest velocity which indicates the
concrete is weaker than the other test subjects and more likely

to
fail. It was interesting to see however that the 200mm length
recoded a relatively high velocity in comparison to the 120mm
length.






Block two, AASS
-
0.75, recorded steady velocity values in both
directions and whilst the values were not as high as

block three,
AND1 S30, it still rated highly on the above table.


Brenton Hale

S3166367




Accuracy of Results

The equipment was calibrated to the sample cylinder before the test to ensure greater accuracy. This would help

in the recording of
precise data but as this technique required good contact with the surface of the concrete I believe the results will always v
ary
depending on how much Vaseline is used and the overall contact of the measurement tools.


Block one showed

a great variation in the 120mm length recordings which brings into question the test results. However the test
instructions were followed to the book and with the help of the lab technicians I feel that the results were accurate under t
he
conditions.


28
th

April 2010


Brenton Hale

S3166367


3 Valley Drive
,
Beaconsfield Upper
,
VIC

3808

|
ph

59 444 343

|
mb

0400 990 609

S3166367@student.rmit.edu.au

Brenton Hale

S3166367


Cover Meter


Detection and measurement of Cover
to

Reinforcing
Bars

The sheet attached shows the layout of the reinforcing bars within the concrete section. These
locations were found using the Profometer 5+ cover meter.


The
system works by utilizing the eddy current principle with pulse induction. This allows the cover
meter to detect where a reinforcing bar in and at what depth.


Results

See next page.


Discussion

In block one, two reinforcing bars were located at depths of
46mm and 18mm. They spanned
105mm and 170mm respectively and were spaced 215mm apart.


In block two, five reinforcing bars were located forming a mesh pattern. This made it difficult to
identify each individual bar as they often crossed under other bars.


The cover meter worked well in identifying the bars locations and the depths which they resided. It
was important to select the correct bar size as it had a significant impact on the results. The user
manual for the Profometer 5+ suggests that the default

bar size if 16mm is selected if the user is
unsure of the reinforcement type. Using the 16mm setting we obtained fairly accurate locations of
the bars however the depths may well be slightly inaccurate.


Accuracy of results

The results obtained were consi
stent with other groups in the class and did not concern the lab
technicians. The technology used does however induce a current in the bar to obtain the
information required and it is quite possible that the bar retained some of this current from previous
tests. This residual current would alter the results obtained by our tests.


The difficulties in obtaining the locations of the bars were the alignment of the unit itself and the
crossing of bars also. This made it more complicated to follow a single bar
and record its location
accurately