to find the rebar corrosion in concrete

1. Half Cell Potential
Measurement Testing (HCPM)
 The Objectives of Concrete Testing
 Principle of Measurement &
Equipment (HCPM)
 Nondestructive Vs Destructive Test
 Comparison with Other Tests
 Tips of Prevention for Corrosion
 Discussion

2. The Objectives of The
Concrete Testing

3. Useful of Concrete Testing
 Prediction of in-place concrete strength (relative
strength comparison, unless correlated with laboratory
strength tests, for example, core compressive strength
tests);
 Location and extent of delaminations due to
reinforcement corrosion;
 Location, size, and distribution of reinforcement bars;
 Location and extent of concrete cracking;
 Severity, location, and extent of fire and frost damage;
 Location and extent of void honeycombing;
 Determination of concrete thicknesses; and
 Evaluation of reinforcement corrosion activity and rate.

4. Concrete Condition Assessment
 Testing data helps Engineer on assessing a
building structure condition
 Testing data helps Owner to monitor and control
their building structure condition
 Testing data helps Engineer to design suitable
solutions on mitigating defects.
 Testing data helps Owner to budget their building
maintenance cost, insurance…etc.
 Testing data provide a good trend record on
building management

5. Example (1) – A Building Ceiling

6. Example (2) – Car Park

7. Principle of Measurement
& Equipment

8. What kind of parameter is useful for concrete
assessment?
•Temperature
•Humidity
•PH value
•Potential difference
•Polarization resistance
•Current density data
HCPM method uses potential difference.
Useful Parameters

9. Corrosion in Concrete
 Anode
Reaction
Fe – 2e  Fe2+
 Cathode Reaction
2H2O + O2 + 4e 
4OH-
•H2O •H2O
•O2 •O2
•Cl-
•Cl-
•OH- •OH-
•Cathode •Cathode
•Anode
•e- •e-
•Fe2+
•rust•rust
•Cl-
•Cl-
•Cl-
•Cl-
•Cl- •Cl-
•Cl-

10. Concrete Resistivity
Testing Mechanism
•I
•~
•V
•S •S •S
•Voltmeter
•Ammeter
•Alternating
•Current Supply
•Electrodes
•Current Flow Lines
•Equipotential Surface

11. Corrosion Values
 In ASTM C876 to determine possibility of corrosion
for a Copper-Copper Sulfate Reference Electrode
mV Range Probability of Corrosion
0 to -200 > 90% No Corrosion
-200 to -350 Uncertain Corrosion Activity
Less than -350 > 90% Corrosive Activity

12. Tips for using Half-cell
1. Concrete cover less than 75mm
2. Temperature range: 0 - 49℃
3. Steel does not have metallic coating
4. Condition required experience corrosion
engineer or specialist:
a) Concrete is saturated in water
b) Carbonated at the depth of reinforcing steel
c) Steel is coated
d) Contains chloride or bromide

13. Instrument
•Wire Port to rebar
•Cell Holder
•Meter
•Meter Set

14. Nondestructive Test (NDT)
Vs Destructive Test (DT)

15. Nondestructive Test Vs
Destructive Test
 Destructive Testing (DT) involves the physical
destruction of a components. A variety of testing
methods can be employed to evaluate the
component's characteristics, it always refer to a
sampling inspections.
 Destructive Testing (NDT) involves inspection of
a components by subjecting them to the required
service conditions to determine suitability. They
will not break or alter the structure or
appearance of the friction of a component.

16. Destructive Test for Concrete
 Tensile Test
 Impact / Compression Test
 Hardness Test
 Fracture Test
 Bend Test
 Core Sample Test

17. Comparsion of Testing Method
•Non-destructive Test
 On-site
 Simple & faster
 No damage to
installation
 Cost effective
 Require usually hand-
held equipment
 Easy space allocation
 Usually outdoor and
weather dependent
Destructive Test
 Workshop or Laboratory
 Heavy & time consuming
 Rebuilt the testing point
 Higher cost
 Require elaborate
equipment
 Difficult to some
locations
 Indoor and weather
independent

18. Comparison with Other
Tests

19. Comparison to Other Tests
• Rebound Hammer ASTM C805
• Penetrating Probe ASTM C803
• Ultrasonic Wave Velocity
 Through transmission testing
ASTM C597
 Impact Echo testing ASTM C1383
• Pullout Test ASTM C900

20. Rebound Hammer ASTM C805

21. Rebound Number Correlations

22. Penetrating Probe ASTM C803

23. Penetrating Probe ASTM C803

24. Penetrating Probe Correlations

25. Ultrasonic Wave Evaluation

26. Ultrasonic
Pulse
Velocity
ASTM
C597

27. Comparsion Table

28. Tips of Prevention for
Corrosion in Concrete

29. Corrosion may be prevented or
controlled by:
 materials selection
 reducing the temperature
 applying physical barriers
 adding inhibitors
 cathodic protection
• using metals that form a protective oxide
layer
• Painting/coating

30. Example of Applying Physical Barriers
Now aday Special coating such as epoxy or silicate are used
History of Development of Physical Barriers

31. Example of adding inhibitors
Spray-applied reactive penetrants combine with alkalis
within the concrete, reducing the pH and permeability
to moisture vapor

32. Discussion