Civil Engineering Reference
In-Depth Information
overloading, leakage of water-retaining structures and deflection caused by
progressive creep.
Faulty construction is also included in this group except when it has led
to corrosion or AAR. It is usually detected immediately after completion of
the structure but seven of the cases were not identified until much later. In
most of the reports faulty construction involved cracking but it was not clear
whether it had been present since the structure was built or had developed
later as a consequence of some other fault.
Altogether there were 78 case histories of mechanical and other damage.
The distribution of the types of damage is shown in
Figure 14.5.
14.4 The repairs
In general the repairs were designed and carried out with the objective of
achieving durability for the remaining life of the structure but the more
realistic expectation was somewhat less. There was only one case where it
was stated that the repair was a 'holding action' to last a short time until the
structure could be replaced. In practice temporary repairs may be carried out
for a variety of reasons and it is not unusual for them have to remain much
longer than intended.
The most common types of repair were: patching, coating, crack injection,
restoration of strength (replacement of excessively corroded reinforcement
bars, added prestress), sprayed concrete, and electro-chemical methods (CP,
realkalisation, chloride extraction). Other less common methods included:
application of corrosion inhibitors, bonded plating, wrapping with carbon
fibre reinforced plastic (CFRP), and added cover concrete. In 60 per cent
of the case histories more than one method was used, for example patching
plus coating.
30
25
20
15
10
5
0
Frost
Cracking
Faulty
construction
Wear
Other
