The document discusses various types of failures that can occur in flexible pavements, including alligator cracking, rutting, shear failure cracking, longitudinal cracking, frost heaving, lack of binding between layers, reflection cracking, bleeding, and pumping. It describes the primary causes of these failures as being relative movement between pavement layers, repeated heavy wheel loads, and swelling/shrinkage of subgrade layers from moisture variation. Specific failures like rutting and shear cracking are also explained in more detail.

1. Inadequate stability
Loss of binding action
Loss of base course material
Inadequate wearing course

2.  Typical failure encountered in flexible
pavements are as follow.
◦ 1.Alligator cracking or Map cracking (Fatigue)
◦ 2.Consolidation of pavement layers (Rutting)
◦ 3.Shear failure cracking
◦ 4.Longitudinal cracking
◦ 5.Frost heaving
◦ 6.Lack of binding to the lower course
◦ 7.Reflection cracking
◦ 8.Formation of waves and corrugation
◦ 9.Bleeding
◦ 10.Pumping
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3. ◦ Followings are the primary causes
of this type of failure.
 Relative movement of pavement
layer material
 Repeated application of heavy
wheel loads
 Swelling or shrinkage of
subgrade or other layers due to
moisture variation
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4. ◦ Formation of ruts falls in
this type of failure.
◦ A rut is a depression or
groove worn into a road
by the travel of wheels.
◦ This type of failure is
caused due to following
reasons.
 • Repeated
application of load along
the same wheel path
resulting longitudinal
ruts.
 • Wearing of the
surface course along the
wheel path resulting
shallow ruts.
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5. ◦ Shear failure causes
upheaval of pavement
material by forming a
fracture or cracking.
◦ Followings are the primary
causes of shear failure
cracking.
 • Excessive wheel
loading
 • Low shearing
resistance of pavement
mixture
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6. ◦ This types of cracks extents to
the full thickness of pavement.
◦ The following are the primary
causes of longitudinal cracking.
 Differential volume changes in
subgrade soil
 Settlement of fill materials
 Sliding of side slopes
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7.  Frost heaving causes
upheaval of localized
portion of a
pavement. The extent
of frost heaving
depends upon the
ground water table
and climatic
condition.
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8.  When there is lack of
binding between surface
course and underlying
layer, some portion of
surface course looses up
materials creating
patches and potholes.
 Slippage cracking is one
form of this type of
failure.
 Lack of prime coat or
tack coat in between two
layers is the primary
reason behind this type
of failure.
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9.  This type of failure
occurs, when
bituminous surface
course is laid over
the existing cement
concrete pavement
with some cracks.
This crack is
reflected in the same
pattern on
bituminous surface.
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10.  Excess bituminous
binder occurring on
the pavement surface
causes bleeding.
Bleeding causes a
shiny, glass-like,
reflective surface that
may be tacky to the
touch. Usually found in
the wheel paths.
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11.  Seeping or
ejection of water
and fines from
beneath the
pavement through
cracks is called
pumping
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12. DEFICIENCY OF PVT MATERIALS
USE OF SOFT AGG,POOR WORKMANSHIP IN JOINT
CONSTRUCTION ,POOR SURFACE FINISHING ,IMPROPER &
INSUFFICIENTCURING
STRUCTURAL INADEUENCY
INADEQUATE PVT THICKNESS, INADEQUATE SUBGRADE
SUPPORT,INCORRECTSPACING OF JOINTS

13. Scaling of c.c
Shrinkage cracks
Spalling of joints
Warping of joints
Mud pumping

14. It is overall deterioration of cement concrete slab
It is mainly attributed due to deficiency in mix or presence of chemical
impurities
Due to excessive vibration during compaction
This gives rough surface and not good apperance

15.  Shrinkage cracking
During curing of C.C pvt and immediately after construction shrinkage is
normally develop
These are in longitudinal as well as in transverse direction

16.  Joint spalling
Break down of slab near edges of joints
It occurs due to incompressible material below concrete slab

17.  Mud pumping
Slurry ejects out from joints and cracks of C.C pvt causes down word
movement of slab under heavy wheel loads
Occurs due to infiltration of water through the joints or cracks of pvt
Soil surry comes out due to movement of vehicles
It depend –slab deflction, type of subgrade of soil, amount of water

18.  Warping cracks
In hot weather concrete bends when joints are not designed properly
This results in dvp of excessive stress due to warping & cracking at edges in
irregular pattern
No structural defetcs due to warping if long-transverse rft if propelly provided