17.5 Examples of Concrete
Cracks
Examples
of concrete cracks and causes are shown in Figure 17.6 and Table 17.1,
respectively
(A)
Table 17.1 
Crowfoot Crack: this crack is
often either parallel with pavement or making certain angle with Expansion
Joint. Occurrence of crowfoot crack is attributable to expansion of material
used to fill up the Expansion Joint, which develops toward the edge of
pavement. Or water/other chemical substances permeate through Expansion Joint
or Contraction Joint.
Crowfoot Crack: this crack is
often either parallel with pavement or making certain angle with Expansion
Joint. Occurrence of crowfoot crack is attributable to expansion of material
used to fill up the Expansion Joint, which develops toward the edge of
pavement. Or water/other chemical substances permeate through Expansion Joint
or Contraction Joint.
(B)
Corner Break: the characteristic of this
corner crack is similar to triangle, which its dimension in each side is
greater than 45 cm. For the reason that cracks initiate is due to the pavement
has to withstand to excessive loads fatiguingly and impulsively.
(C)
Diagonal Crack: this crack is formed
diagonally to the pavement due to disproportion of bearing capacity of
subgrade, which brings different settlement throughout the terrain or affected
by change of soil volume.
(D)
Spalls: this crack can be found on every
type of joints or interconnection of two joints. Because of incompatibility in
material selection and designing of contraction joint or water/other chemical
substances are subject to permeability above the joint.
(E)
Transverse Crack: owing to length of
pavement is large and no contraction joint provided for such length, this
results crack to occur in transverse direction to the pavement.
(F)
Transverse Crack: this type of crack
occurs in transverse direction to the pavement, which approximately located at
120 – 150 cm. away from contraction joint. As a result of reduction in soil
bearing capacity, it is attributable to weathering of existing soil by mean of
water. This incident is called “Pumping Phenomenon”, which water will push out
soil through leakage of that water permeate in. Thus, existing soil can no
longer be bearable and eventually induces cracks.
(G)
Longitudinal Crack: this type of crack
occurs along the length of pavement due to the pavement has large width with no
joint cutting through the middle.
(H)
Plastic Shrinkage Crack: feature of this
particular crack is known as crazing, which resulted from rapid loss of water
of fresh concrete due to prior curing is insufficient, fast evaporation above
the surface or existing soil/aggregate is completely dried out, which water
will be promptly used up.
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