Kandhal Lecture 9 On Bituminous Pavement Distresses - Causes and Cures (Handouts)
Kandhal Lecture 9 On Bituminous Pavement Distresses - Causes and Cures (Handouts)
Kandhal Lecture 9 On Bituminous Pavement Distresses - Causes and Cures (Handouts)
Kandhal 2
1
Load Associated (Fatigue)
Cracking
Also called alligator or map cracking
Loads too heavy for the pavement structure
Too many repetitions of load more than design
Inadequate support (pavement layers/subgrade)
Poor drainage
Very stiff binder in surface course
Occurs in wheel path, potholes develop in
advanced stage
Non-Load Associated
(Thermal) Cracking
Transverse cracks occur at regular intervals
Asphalt binder too stiff at low service
temperatures
Rapid chilling of the road surface
Highly temperature susceptible asphalt binder
Subgrade type (more on sandy)
Age of the pavement
2
Longitudinal Joint Cracking
Longitudinal Cracking
Occurs parallel to the center line of roadway
Reflection Cracking
Discontinuities in the underlying layers propagate
through the asphalt surface due to movement of
cracks
Discontinuities
Cracks or joints in underlying concrete pavement
Cracks in soil-cement base course
All types of cracks in the existing bituminous
pavement
Causes
Thermal (movement of joints/cracks)
Load
3
Treatment for Cracks
Cracks should be sealed as soon as
possible so that there is no water
penetration in the pavement, which mat
cause further damage
Asphalt-rubber is considered best
material for sealing cracks
Rutting
Spalling is about to Spalling has taken place.
Lack of adequate subgrade support
take place between It can be fixed with
Unstable asphalt course(s)
parallel cracks asphalt mix patch repair.
- Poor mix design
- Rounded aggregate
- Excessive asphalt binder
Stripping in asphalt courses
4
Rutting Resulting from Subgrade Rutting within Asphalt Courses
Slippage Cracking
Treatment for Rutting
Plastic movement - Depression in the Wheel
Associated with slippage mechanism
Path with Humps in Either Side
First determine the cause(s) and location Poor bond between the surface layer and
of rutting underlying layer
Any layer exhibiting rutting must be Too much or too little tack coat
Consolidation/Densification -Depression in the
Wheel Path Without Any Humps
removed (milled) completely and Steep grades/intersections
replaced with more stable mix course Acceleration/braking exert surface traction forces
U-shaped
Mechanical Deformation - Subsidence or
Patch repairs needed in area with slippage crack
Densification in the Unbound Base or Subgrade
Kandhal and Accompanied by a Cracking Pattern 43 Kandhal 44 Kandhal 45
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Kandhal 46 Kandhal 47 Kandhal 48
Checking Corrugations
Lack of bond between asphalt courses
Unstable surface course mix
Braking and accelerating action near
intersections
Areas with corrugations have to be milled off
and replaced with highly stable asphalt mix
Raveling
Progressive disintegration of asphalt surface as a
result of dislodgment of aggregate particles in
the mix
Lack of sufficient cohesion due to low in-place
density
Lack of fines in the asphalt mix matrix,
especially in coarse, segregated areas
Aging of asphalt binder
6
Treatment for Raveling
Following treatments are suggested in order of
severity of raveling from slight to severe
Apply fog seal with diluted emulsified asphalt
binder
Apply slurry seal/microsurfacing
Overlay with dense graded asphalt mix
Classic Signs of Stripping: White Spots Followed by Bottom of Binder Course Showing Stripped
Bleeding and then Pothole Aggregate
7
Potholes may result form stripping
Bottom of Binder Course Showing Stripped Skid Resistance
Aggregate
Friction between the tire and road surface. Quantified
by Friction Number (FN). Critical when surface is
wet; makes it very slippery.
Causes for Low FNs
Flushing/bleeding of asphalt surface
Inadequate microtexture (aggregate property)
- aggregate prone to polishing
Inadequate macrotexture (mix property)
- no drainage channels
- causes hydroplaning
- important at high speeds
Look
for the
Unusual!
QUESTIONS?
Kandhal 70