8 Damage to concrete structures
level of the structure is reached by carefully considering all influencing
factors as previously described.
Strategy B relies on maintenance. It is accepted that the initiation of
corrosion progresses somewhat further by penetration of carbon dioxide
into the concrete cover. Once a certain carbonation depth is reached, some
maintenance will be done by the application of coatings, or by increasing
the concrete cover thickness by applying an extra mortar layer.
Strategy C accepts that the carbonation depth reaches the reinforcement, so that the corrosion process actually can start degrading the
reinforcement. As a consequence of the expansive formation of corrosion products, cracks can be initiated in the concrete cover. Within this
strategy, repair activities will be needed, possibly combined with further
maintenance.
Following strategy D, no action is taken until severe damage has occurred
to the concrete structure, including spalling of concrete cover due to expansive action of the corrosion products. The reinforcement bars are severely
corroded, over larger areas. At this stage, important and expensive renovation and rehabilitation actions are needed, involving partial or full replacement of structural elements.
The costs involved with the different strategies are shown in a relative
way in Figure 1.6. Shifting the strategy one level implies a multiplication of
the total costs by a factor of five. In this way, it is illustrated that the same
service life can be obtained by a relatively small initial investment following
the good practice, or by a relatively high investment by relying on repair
and rehabilitation.
Time
Good practice
Maintenance
Repair and maintenance
Renovation
€ 1,€ 5,€ 25,€ 125,A
B
C
D
Corrosion
Service Life
D
Critical corrosion value
Cost
C
B
A
Figure 1.6 Cost strategies.
level of the structure is reached by carefully considering all influencing
factors as previously described.
Strategy B relies on maintenance. It is accepted that the initiation of
corrosion progresses somewhat further by penetration of carbon dioxide
into the concrete cover. Once a certain carbonation depth is reached, some
maintenance will be done by the application of coatings, or by increasing
the concrete cover thickness by applying an extra mortar layer.
Strategy C accepts that the carbonation depth reaches the reinforcement, so that the corrosion process actually can start degrading the
reinforcement. As a consequence of the expansive formation of corrosion products, cracks can be initiated in the concrete cover. Within this
strategy, repair activities will be needed, possibly combined with further
maintenance.
Following strategy D, no action is taken until severe damage has occurred
to the concrete structure, including spalling of concrete cover due to expansive action of the corrosion products. The reinforcement bars are severely
corroded, over larger areas. At this stage, important and expensive renovation and rehabilitation actions are needed, involving partial or full replacement of structural elements.
The costs involved with the different strategies are shown in a relative
way in Figure 1.6. Shifting the strategy one level implies a multiplication of
the total costs by a factor of five. In this way, it is illustrated that the same
service life can be obtained by a relatively small initial investment following
the good practice, or by a relatively high investment by relying on repair
and rehabilitation.
Time
Good practice
Maintenance
Repair and maintenance
Renovation
€ 1,€ 5,€ 25,€ 125,A
B
C
D
Corrosion
Service Life
D
Critical corrosion value
Cost
C
B
A
Figure 1.6 Cost strategies.