Durability and service life 7
slightly different and a real strength is reached instead of a design strength.
For the specific case of concrete structures, the concrete cover, the compaction of the concrete, and the curing of the concrete are of major importance
for the final durability characteristics of the completed structure. When
coatings have to be applied, the real performance of this coating is also
very important, as it typically has to provide some protection. The quality
control on the construction site and the actions to avoid construction errors
are important issues during the construction stage.
After completion of the structure, a certain structural response will be
reached. This response could be experimentally verified, e.g. trial loading
of a bridge. When design and construction have been properly done, the
initial structural response should be better than the structural requirements on which the design was based. From that point on, the environment starts to have an influence on the structure. Due to mechanical,
physical, and chemical loading, the structure will start to degrade. Within
this process, the atmospheric conditions (temperature and humidity) and
the presence of potentially aggressive substances largely influence the
degradation rate.
Regular inspection or continuous monitoring will reveal relevant information on the evolution of the structural response of the ageing structure.
Depending on the outcome of the comparison with the structural requirements, maintenance or repair actions could be defined in order to reach the
target service life. When the structural response is no longer in agreement
with the structural requirements, the end of service life is reached.
1.3 strategIes anD cost
Although it is the intention to further focus on technical requirements, it
is certainly good to know that technical choices have economical consequences. This will be illustrated in this section by considering the example
of reinforcement corrosion in concrete structures. While the scientific background concerning reinforcement corrosion will be explained in Chapter 5,
we illustrate some cost strategies for the case of reinforcement corrosion
by considering the generally accepted Tuutti model as shown in Figure 1.6.
The vertical axis shows the evolution of corrosion, considering an induction period (horizontal line) and a propagation period (inclined line). After
a certain time period, the corrosion level reaches a critical corrosion level,
defining the end of service life.
Four different strategies can be followed in order to reach a target service life.
Strategy A is the strategy of good practice, involving an adequate design
and high quality execution. Within this strategy, an appropriate durability
slightly different and a real strength is reached instead of a design strength.
For the specific case of concrete structures, the concrete cover, the compaction of the concrete, and the curing of the concrete are of major importance
for the final durability characteristics of the completed structure. When
coatings have to be applied, the real performance of this coating is also
very important, as it typically has to provide some protection. The quality
control on the construction site and the actions to avoid construction errors
are important issues during the construction stage.
After completion of the structure, a certain structural response will be
reached. This response could be experimentally verified, e.g. trial loading
of a bridge. When design and construction have been properly done, the
initial structural response should be better than the structural requirements on which the design was based. From that point on, the environment starts to have an influence on the structure. Due to mechanical,
physical, and chemical loading, the structure will start to degrade. Within
this process, the atmospheric conditions (temperature and humidity) and
the presence of potentially aggressive substances largely influence the
degradation rate.
Regular inspection or continuous monitoring will reveal relevant information on the evolution of the structural response of the ageing structure.
Depending on the outcome of the comparison with the structural requirements, maintenance or repair actions could be defined in order to reach the
target service life. When the structural response is no longer in agreement
with the structural requirements, the end of service life is reached.
1.3 strategIes anD cost
Although it is the intention to further focus on technical requirements, it
is certainly good to know that technical choices have economical consequences. This will be illustrated in this section by considering the example
of reinforcement corrosion in concrete structures. While the scientific background concerning reinforcement corrosion will be explained in Chapter 5,
we illustrate some cost strategies for the case of reinforcement corrosion
by considering the generally accepted Tuutti model as shown in Figure 1.6.
The vertical axis shows the evolution of corrosion, considering an induction period (horizontal line) and a propagation period (inclined line). After
a certain time period, the corrosion level reaches a critical corrosion level,
defining the end of service life.
Four different strategies can be followed in order to reach a target service life.
Strategy A is the strategy of good practice, involving an adequate design
and high quality execution. Within this strategy, an appropriate durability