CONCRETE CONSTRUCTION (ECM725-OLD) 4. Method Statement For Cover Meter If we refer to the case study, the structure needs to be monitored and tested to know the level of damage the structure bear and why the damage occurs. One of the propose method is by using cover meter. This method gives us the depth of the cover, whether it’s complying with design or the structure is wrongly constructed. This instrument is use to locate rebar’s and measure the exact concrete cover, that is the measurement from centre of main bar to the outside surface of the concrete as shown in Figure 4.1. The cover meter works by using the eddy current principle with pulse induction as the measuring method. With this, drilling can be avoided as option to locate the bars.
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MOS for Resistivity Half Cell Potential, Crack Width, Cover Meter
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CONCRETE CONSTRUCTION (ECM725-OLD)
4. Method Statement For Cover Meter
If we refer to the case study, the structure needs to be monitored and tested to know
the level of damage the structure bear and why the damage occurs. One of the propose
method is by using cover meter. This method gives us the depth of the cover, whether it’s
complying with design or the structure is wrongly constructed.
This instrument is use to locate rebar’s and measure the exact concrete cover, that is
the measurement from centre of main bar to the outside surface of the concrete as shown
in Figure 4.1. The cover meter works by using the eddy current principle with pulse
induction as the measuring method. With this, drilling can be avoided as option to locate
the bars.
Figure 4.1 Concrete cover = d
CONCRETE CONSTRUCTION (ECM725-OLD)
a. Equipment
The cover meter test device contains 2 major parts, as shown in Figure 4.2.
1. Reader
2. Detector
Figure 4.2. Cover Meter apparatus
This equipment has certain features that give the engineers the ability to investigate
the structural damage and the method to mitigate the problem. This equipment features:
The cover meter allows the detection of rebar’s
Measurement of the concrete cover depth and the diameter of the reinforcement
The device can give correction for the influence of neighboring bars.
The device can stored thousand of cover values and statistical analysis
b. Methodology
The location surrounding the damage structure are marked into several line, about
2-3 inches between each other and the radius of marked area are justified by the
engineers
The reader turns on, the detector are place down at marked line and data collection
can be start immediately
Data collection can be use as reference for further analysis
c. Standards
CONCRETE CONSTRUCTION (ECM725-OLD)
BS 1881 part 204 DIN 1045
SN 505 262 DGZfP B2 (recommendation)
d. Conclusion
The cover meter is an easy, effective, accurate and economic way to find out the
cause of structural damage. Data collected can be use to justify the causes of the damage
occurs, whether the cover is low so that the carbonation or chlorides easily enter the
structure or the concrete covers are too thick that causes weakness and cracks to the cover
itself. From the data collected, analysis can be done to justify the condition. Figure 4.3
shows the relationship between the concrete cover thickness and time.
Figure 4.3 Reduction of the initiation time of corrosion sue to
reduction of thickness of the concrete covers
5. Method Statement For Half Cell Potential
CONCRETE CONSTRUCTION (ECM725-OLD)
Other methods of determine the damage of the structure is by using half cell potential
test. This test is another non destructive test which can measure the corrosive activity in
the concrete. The test is simple and the result is dependable. Generally, the half cell
potential test gives the condition of steel embedded in the concrete with regards to the
corrosion activity. Using this method, the electrical potential difference between the real
structure and reference electrode is then measured.
a. Equipment
The equipment consists:
Reference electrode
Positive and negative connection
High impedance digital voltmeter
Figure 5.1 General diagrams of Half Cell Potential apparatus