4 Damage to concrete structures
and more polluted, giving rise to an increased degradation risk to
(concrete) structures.
• More advanced design methods, e.g. ultimate limit state design methods instead of elastic design, and advanced developments on the materials level, such as the implementation of modern plasticizers, have led
to more slender concrete structures. As a consequence, the structures
might be somewhat more sensitive to degradation mechanisms compared to over-designed structures.
Nowadays, the attention given to durability (and sustainability) is at a
much higher level than a few decades ago. This textbook aims to further
transfer the knowledge on the possible degradation mechanisms of concrete
structures. However, first some general information is given on durability
and service life of structures in general.
1.2 DurabIlIty anD servIce lIfe
Structures in general, and concrete structures in particular are designed to fulfil requirements related to strength and function during a certain time period,
without incurring unexpected costs for maintenance or repair. This time
period is called the service life of the structure, and it is mainly determined
by the structure’s durability. The durability is the property of the material or
the structure to withstand serious degradation mechanisms, making sure that
the decline of the initial properties is kept within acceptable quality limits. In
other words, the durability of a structure is the capacity to resist degradation,
making sure that the required service life can be reached.
After successful completion of a structure, the initial quality is higher
than the minimal required level as shown in Figure 1.4. With time, due to
the ‘ageing’ of the structure, the quality of the structure decreases. In normal conditions, the decreasing quality reaches the minimal required level
only at the end of the target service life. In the case of aggressive environment, the rate of quality loss can be very high, possibly leading to an accelerated crossing of the minimal required level, meaning that the target service
life is not reached. In this case, repair actions can be necessary to reach
the target service life. The effect of repair is visible in Figure 1.4 by a sudden increase in quality of the structure. Distinction can be made between
corrective repair in order to rehabilitate the structure after an unforeseen
accelerated degradation, or preventive repair anticipating predicted future
damage. In principle, for every important structure a specific maintenance
and repair strategy should be defined and linked with an adequate inspection and monitoring strategy.
Reaching the end of service life does not necessarily mean that the
structure will collapse or will have to be demolished. It rather means that
and more polluted, giving rise to an increased degradation risk to
(concrete) structures.
• More advanced design methods, e.g. ultimate limit state design methods instead of elastic design, and advanced developments on the materials level, such as the implementation of modern plasticizers, have led
to more slender concrete structures. As a consequence, the structures
might be somewhat more sensitive to degradation mechanisms compared to over-designed structures.
Nowadays, the attention given to durability (and sustainability) is at a
much higher level than a few decades ago. This textbook aims to further
transfer the knowledge on the possible degradation mechanisms of concrete
structures. However, first some general information is given on durability
and service life of structures in general.
1.2 DurabIlIty anD servIce lIfe
Structures in general, and concrete structures in particular are designed to fulfil requirements related to strength and function during a certain time period,
without incurring unexpected costs for maintenance or repair. This time
period is called the service life of the structure, and it is mainly determined
by the structure’s durability. The durability is the property of the material or
the structure to withstand serious degradation mechanisms, making sure that
the decline of the initial properties is kept within acceptable quality limits. In
other words, the durability of a structure is the capacity to resist degradation,
making sure that the required service life can be reached.
After successful completion of a structure, the initial quality is higher
than the minimal required level as shown in Figure 1.4. With time, due to
the ‘ageing’ of the structure, the quality of the structure decreases. In normal conditions, the decreasing quality reaches the minimal required level
only at the end of the target service life. In the case of aggressive environment, the rate of quality loss can be very high, possibly leading to an accelerated crossing of the minimal required level, meaning that the target service
life is not reached. In this case, repair actions can be necessary to reach
the target service life. The effect of repair is visible in Figure 1.4 by a sudden increase in quality of the structure. Distinction can be made between
corrective repair in order to rehabilitate the structure after an unforeseen
accelerated degradation, or preventive repair anticipating predicted future
damage. In principle, for every important structure a specific maintenance
and repair strategy should be defined and linked with an adequate inspection and monitoring strategy.
Reaching the end of service life does not necessarily mean that the
structure will collapse or will have to be demolished. It rather means that