Concrete shrinkage is a volume change that can occur either autogenously or induced, leading to cracks and affecting the material's long-term strength and durability. Different types of shrinkage include plastic, drying, autogenous, and carbonation shrinkage, each with distinct causes and characteristics. Plastic shrinkage cracks may occur soon after placement due to drying, while drying shrinkage results from moisture loss after setting, potentially leading to tensile stress and cracking.

1. SHRINKAGE OF CONCRETE
• Concrete is subjected to changes in volume either
autogenous or induced. Volume change is one of the
most detrimental properties of concrete, whichaffects the
long –term strength and durability. it causes unsightly
cracks in concrete and called concrete shrinkage.
• Types of shrinkage
• Plastic shrinkage in concrete
• Drying shrinkage in concrete
• Autogenous shrinkage in concrete
• Carbonation shrinkage in concrete

2. SHRINKAGE OF CONCRETE

3. PLASTIC SHRINKAGE
• Cracks appear in the surface of fresh concrete
soon after concrete soon after it is placed and
while it is plastic. These cracks appear mostly
on horizontal surfaces.
• Plastic shrinkage cracking is more likely to
occur when high evaporastion rates causes
the concrete surface to dry out before it has
set

4. PLASTIC SHIRNKAGE

5. DRYING SHRINKAGE
• Shrinkage is defined as the contracting of a
hardened concrete mixture due to the loss of
capillary water. This shrinkage causes an
increases in tensile stress, which may lead to
cracking, internal warping, and external
deflection, before the concrete is subjected to
any kind of loading.

6. DRYING SHRINKAGE

7. Plastic settlement cracks
• Cracks caused when the settlement of fresh concrete is restrained
by reinforcement or formwork. Plastic settlement cracks can form
in young concrete, within the first few hours after placing. As
water moves upward through the mixture, the denser
constituents move downward. This downward movement may be
obstructed by the top layer of reinforcement or by the shuttering.
• The plastic concrete may arch over the top of individual
reinforcing bars, bringing the surface into tension. Cracks may
develop at regular spacing and usually follow the line of the
uppermost bars, giving a series of parallel cracks; there may also
be shorter cracks at right angles over the bars running in the
opposite direction.

8. • It is sometimes possible for plastic settlement cracks to form
on a vertical face where reinforcement has restricted the free
flow of concrete within the formwork. In such cases it is
possible that the cracks are formed between the lines of the
reinforcement.
• The concrete can also be supported by the shuttering, causing
restraint to the concrete in connected members. This typically
happens at mushroom-heads on columns but can also occur at
other locations, such as under spacer blocks. Cracks at
mushroom heads of columns are generally horizontal. They
are also typically 1 mm wide and can cross the full section.