80 Damage to concrete structures
For a lower degree of hydration, the pore structure will be coarse and more
evaporable water will still be available, leading to higher shrinkage values.
The duration of the curing period thus is important for the drying shrinkage strains occurring as soon as curing is ended. This is not always well
implemented in design codes.
It can also be mentioned that a lower curing temperature seems to
lead to larger ultimate drying shrinkage strain (Bisschop 2001). This
probably is related to the effect of temperature on the hydration process
and thus on the value of the degree of hydration at the end of the curing
period.
4.3.3 Mitigation
Considering the influencing parameters as mentioned in the previous section, some measures can be listed in order to reduce drying shrinkage
strains in concrete elements:
• In order to reduce drying shrinkage strains, the water/cement ratio
of the concrete has to be limited. However, as explained in the section on autogenous shrinkage, a strong reduction of the water/cement
ratio will significantly increase autogenous shrinkage values.
• The paste volume of the concrete should be limited, which means that
the aggregate content should be increased. This should be considered
in view of other requirements, such as workability. In case of selfcompacting concrete, a higher paste volume and lower aggregate content is quite common, influencing shrinkage behaviour (De Schutter
et al. 2008). This does not mean however that self-compacting concrete always shows higher shrinkage strains.
• Curing of the fresh concrete should be carefully done and maintained
long enough. Insufficient curing will lead to a lower degree of hydration and to higher drying shrinkage values.
• A good casting scheme can also contribute to a lower risk of drying
shrinkage cracking. As shrinkage stresses are mainly caused by external restraint of shrinkage deformation, an optimized casting sequence,
reducing external restraint, can be very helpful. Constructive measures like joints, reducing the length of linear elements, or the size of
individual floor slabs, have to be duly investigated.
4.3.4 example
Drying shrinkage cracking quite often occurs in concrete slabs on grade
(often in combination with plastic shrinkage cracking). The size of the individual slabs is important, with larger sizes leading to increased cracking
risk. Joints have to be provided or saw cuts have to be made shortly after
For a lower degree of hydration, the pore structure will be coarse and more
evaporable water will still be available, leading to higher shrinkage values.
The duration of the curing period thus is important for the drying shrinkage strains occurring as soon as curing is ended. This is not always well
implemented in design codes.
It can also be mentioned that a lower curing temperature seems to
lead to larger ultimate drying shrinkage strain (Bisschop 2001). This
probably is related to the effect of temperature on the hydration process
and thus on the value of the degree of hydration at the end of the curing
period.
4.3.3 Mitigation
Considering the influencing parameters as mentioned in the previous section, some measures can be listed in order to reduce drying shrinkage
strains in concrete elements:
• In order to reduce drying shrinkage strains, the water/cement ratio
of the concrete has to be limited. However, as explained in the section on autogenous shrinkage, a strong reduction of the water/cement
ratio will significantly increase autogenous shrinkage values.
• The paste volume of the concrete should be limited, which means that
the aggregate content should be increased. This should be considered
in view of other requirements, such as workability. In case of selfcompacting concrete, a higher paste volume and lower aggregate content is quite common, influencing shrinkage behaviour (De Schutter
et al. 2008). This does not mean however that self-compacting concrete always shows higher shrinkage strains.
• Curing of the fresh concrete should be carefully done and maintained
long enough. Insufficient curing will lead to a lower degree of hydration and to higher drying shrinkage values.
• A good casting scheme can also contribute to a lower risk of drying
shrinkage cracking. As shrinkage stresses are mainly caused by external restraint of shrinkage deformation, an optimized casting sequence,
reducing external restraint, can be very helpful. Constructive measures like joints, reducing the length of linear elements, or the size of
individual floor slabs, have to be duly investigated.
4.3.4 example
Drying shrinkage cracking quite often occurs in concrete slabs on grade
(often in combination with plastic shrinkage cracking). The size of the individual slabs is important, with larger sizes leading to increased cracking
risk. Joints have to be provided or saw cuts have to be made shortly after