Civil Engineering Reference
In-Depth Information
Mechanical and other damage
The data shown in
Table 14.2
(p. 239) are for types of damage excluding
cases where corrosion also occurred.
It is evident from
Table 14.2
that repairs to mechanical damage were
relatively successful. The poor performance of freeze-thaw repairs may be
due to continuing damage to poor quality concrete which was used in the
first place.
14.5.4 Modes of repair failure
The modes of repair failure are shown in
Figure 14.11.
The most common
are continued corrosion, cracking and debonding. Other less common
modes included deteriorated concrete, spalling, efflorescence, discoloured
coating, wear and breakdown of CP. The modes of CP breakdown included:
•
Failures of management (accidentally switching off)
•
Electric failures (short circuit, overheating, failed control)
•
Deterioration with age and weathering.
Failures of CP systems are generally less costly than others because
they can often be rectified by simple measures such as switching on again,
correcting an electrical circuit or replacing a control box. Also, the benefits
of CP continue for some time after current ceases to flow so that there is
enough time to repair the system before corrosion is re-established.
Failure modes of patches (the most common method of repair), were:
•
Cracking, 40 per cent
•
Debonding, 30 per cent
•
Continued deterioration (corrosion, AAR, leakage), 30 per cent.
35
30
25
20
15
10
5
0
Continued
corrosion
Cracking
Debonding
Continued
AAR
Continued
leakage
Other
Figure 14.11
Modes of repair failure.
