3.4.4 Definition of limit state criteria.
A number of service life models for reinforced concrete
structures exist. Many of these adopt the twostage
service life model first proposed by Tuutti
(1982), in which the deterioration is split into two
distinct phases, namely the initiation period and the
propagation period, as shown in Figure 3.
Most service life models assume that the end of
the initiation period denotes the end of service life.
However, since a concrete structure does not immediately
lose its strength or functionality at the onset
of the propagation period, a more sensible approach
would make use of a detailed maintenance strategy
for corrosion-damaged structures. The definition of a
suitable maintenance strategy depends on knowledge
of the following aspects:
- influence of steel reinforcement corrosion on the
load-bearing capacity of structural members
- performance (and durability) of materials and
systems for repair and protection of corrosiondamaged
structures.
Both of the above aspects still need further research
to be fully understood in the context of service-life
modeling. Two research projects are currently being
undertaken at the University of Cape Town, addressing
the above 2 aspects. Aspects relating to the structural
capacity of corrosion-damaged reinforced beams
are discussed by Malumbela et al (2008).