Civil Engineering Reference
In-Depth Information
A survey of performance of repairs, by the US Corps of Engineers
(Emmons, 2006) reported that only 50 per cent of repairs to their structures
were classified as good, 25 per cent were considered fair or poor, and 25 per
cent had failed. Unfortunately no other information was provided.
The owners and managers of concrete structures have varying requirements
but all need to have reliable knowledge of the durability and performance of
any repairs that are undertaken. For industrial installations having high risk
to the general public, such as nuclear plant, it is essential for the structures to
be of wholly durable concrete having long life and no conceivable possibility
of failure. At the other end of the spectrum there are commercial structures
where requirements are short term and 'quick fixes' are acceptable provided
they are safe. National authorities such as highway agencies have high
expectations of repairs and invariably require construction and maintenance
to be carried out to their own standards. Some require the repairs to be
supervised and inspected by their own in-house staff.
The appearance of repairs can be contentious. In some cases structural
integrity is all-important and unsightly repairs are acceptable within reason
and provided they meet requirements of integrity and durability. In others,
the repairs are required to be seamless and comparatively minor differences
in material, texture or colour can be unacceptable. This applies to some of
the older structures that have become classed as having historic importance
(Tilly, 2002a).
Against this background an EU-funded project, CONREPNET, was
carried out with the objective of developing the concept of performance-
based rehabilitation of reinforced concrete structures. The outcome of this
project is described in two publications (Matthews et al., 2007, Tilly and
Jacobs, 2007). The first step in this project was to collect and evaluate case
histories containing data relating to the performance of concrete repairs.
This involved the evaluation of repair performance and identification of the
modes and causes of premature failures.
This chapter addresses reasons for the disappointing performance of
concrete repairs and ways to improve the situation.
14.2 Case histories
Case histories of concrete repairs were mainly supplied by members of the
CONREPNET project, and UK data for cathodic protection installations
were supplied by consultants. Others were obtained from the literature and
first-hand experiences of the author. The suppliers were from all sides of
industry and included consultants (23 cases), repairers (64 cases), academic
institutions (83 cases) and owners of structures (60 cases).
The data were from Finland, Denmark, Sweden, Czech Republic,
Germany, France, Belgium, the Netherlands, Spain, Greece and the UK,
shown in
Figure 14.1
by geographical area, and are representative of a wide
range of European climates and conditions.
