17.6 Cracks of Steel
Reinforced-Pavement
A. 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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