1. HIGHWAY MAINTENANCE
Failures in flexible pavement

2. Outcome of this session
The student would be able to
Identify the different types of failure in flexible pavements
List down the causes and symptoms of flexible failures
Suggest suitable treatments for failure of flexible pavement

3. Recap of Flexible Pavement
Elastic
Less flexural strength
More number of layers
Materials - Gravel , tar / bitumen
Cost - Less construction cost more maintenance cost
Opened to traffic within 24 hours of construction

4. Defects in flexible pavement
1.Surface defects
2.Cracks
3.Deformation
4.Disintegration

5. 1.Surface defects Symptoms Causes Treatment
Fatty surface
Smooth surface
Streaking
Hungry surface
Symptoms
Causes
Treatment
Collection of binder material
Excessive binder
Loss of aggregate
Non uniform spreading
Application of sand
Application of Seal coat
Removal and replace

6. 1.Surface defects(contd..)
Fatty surface
Smooth surface
Streaking
Hungry surface
Symptoms
Causes
Treatment
Slippery when wet
Excessive binder
Polishing of aggregate under traffic
Resurfacing
Application of slurry Seal coat

7. 1.Surface defects(contd..)
Fatty surface
Smooth surface
Streaking
Hungry surface
Symptoms
Causes
Treatment
Presence of lean bitumen in longitudinal and transverse direction
Non uniform application of bitumen
Resurfacing

8. 1.Surface defects(contd..)
Fatty surface
Smooth surface
Streaking
Hungry surface
Symptoms
Causes
Treatment
Loss of aggregate from surface
Appearance of fine crack
Less bitumen usage
Use of absorptive aggregate
Application of slurry seal

9. 2.Cracks Symptoms Causes Treatment
Appearance of short and fine crack at close interval
Less bitumen usage
Excessive filler
Improper compaction
Depends on whether pavement is sound or not
Sound – slurry seal can be used
Not sound – rehabilitation
Hair-line cracks
Alligator cracks
Longitudinal crack
Edge crack
Shrinkage cracks
Reflection cracks

10. 2.Cracks(contd..) Symptoms Causes Treatment
Interconnected cracks – small blocks – skin of alligator
Excessive deflection – unstable sub- grade
Brittleness of binder(due to age of binder)
Depends on whether pavement is sound or not
Sound – slurry seal can be used
Not sound – rehabilitation
Hair-line cracks
Alligator cracks
Longitudinal crack
Edge crack
Shrinkage cracks
Reflection cracks

11. 2.Cracks(contd..) Symptoms Causes Treatment
Hair-line cracks
Alligator cracks
Longitudinal crack
Edge crack
Shrinkage cracks
Reflection cracks
Symptoms
Causes
Treatment
Cracks in straight line along the road (joints -(shoulder & road) (two lanes))
Alternate wetting and drying
Depends on whether pavement is sound or not
Sound – slurry seal can be used
Not sound – rehabilitation

12. 2.Cracks(contd..) Symptoms Causes Treatment
Hair-line cracks
Alligator cracks
Longitudinal crack
Edge crack
Shrinkage cracks
Reflection cracks
Symptoms
Causes
Treatment
Cracks parallel to outer edge
0.3 – 0.5 m from edge
Sometimes transverse cracks appear from this
Lack of lateral support
Settlement of underlying material
Improper surface drainage
Shrinkage
Frost heave
Improper width of pavement
Depends on whether pavement is sound or not
Sound – slurry seal can be used
Not sound – rehabilitation

13. 2.Cracks(contd..) Symptoms Causes Treatment
Hair-line cracks
Alligator cracks
Longitudinal crack
Edge crack
Shrinkage cracks
Reflection cracks
Symptoms
Causes
Treatment
Cracks in transverse cracks direction
Shrinkage due to age (materials)
Depends on whether pavement is sound or not
Sound – slurry seal can be used
Not sound – rehabilitation

14. 2.Cracks(contd..) Symptoms Causes Treatment
Hair-line cracks
Alligator cracks
Longitudinal crack
Edge crack
Shrinkage cracks
Reflection cracks
Symptoms
Causes
Treatment
longitudinal, transverse , diagonal or block cracks
Cracks in pavement underneath
Depends on whether pavement is sound or not
Sound – slurry seal can be used
Not sound – rehabilitation

15. Settlement and upheavel
3.Deformation
Symptoms
Causes
Treatment
Cresent shaped cracks – in direction of thrust of wheels
Thrust of wheels
Inadequate prime or tack coat
Lack of bond b/w layers
Excessive deflection leading to failure in bond
Resurfacing
Slippage
Rutting
Corrugation
Shoving
Shallow
Settlement and upheavel

16. Settlement and upheavel
3.Deformation(contd..)
Symptoms
Causes
Treatment
Longitudinal depression or groove
heavy traffic
Inadequate compaction
Improper mix design
Filling with premix open graded patching material after a tack coat and compacting
Slippage
Rutting
Corrugation
Shoving
Shallow
Settlement and upheavel

17. Settlement and upheavel
3.Deformation(contd..)
Slippage
Rutting
Corrugation
Shoving
Shallow
Settlement and upheavel
Symptoms
Causes
Treatment
Undulations( ripples)
Faulty laying of surface course
Lack of stability in mix
Resurfacing that affected area

18. Settlement and upheavel
3.Deformation(contd..)
Slippage
Rutting
Corrugation
Shoving
Shallow
Settlement and upheavel
Symptoms
Causes
Treatment
Plastic movement within the layer - bulging
Lack of bond b/w layers
Lack of stability in mix
Heavy traffic
Use of non –volatile oil on wheel roller
Removal of the material and patching

19. Settlement and upheavel
3.Deformation(contd..)
Slippage
Rutting
Corrugation
Shoving
Shallow
Settlement and upheavel
Symptoms
Causes
Treatment
Shallow depression
settlement of lower layers
Filled with premix material

20. Settlement and upheavel
3.Deformation(contd..)
Slippage
Rutting
Corrugation
Shoving
Shallow
Settlement and upheavel
Symptoms
Causes
Treatment
Large deformations
Uncomfortable for traffic
Inadequate compaction
Excessive moisture in sub grade
Inadequate pavement thickness
Frost heave
Excavate and refill
Under drains can be provided
Proper redesign
reconstruction

21. 4.Disintegration Symptoms Causes Treatment
Stripping
Loss of aggregate
Ravelling
Pot hole
Edge breaking
Symptoms
Causes
Treatment
Loss of bond and strength of aggregate
improper aggregate usage (design)
Spreading and compacting coarse sand (heated)
Replacing fresh bituminous mix

22. 4.Disintegration(contd..)
Stripping
Loss of aggregate
Ravelling
Pot hole
Edge breaking
Symptoms
Causes
Treatment
Loss of aggregate leading to rough appearance
poor binding b/w aggregate and binder
Application of liquid seal, fog seal or slurry seal

23. 4.Disintegration(contd..)
Stripping
Loss of aggregate
Ravelling
Pot hole
Edge breaking
Symptoms
Causes
Treatment
Failure of binder – eroded areas at edge
inadequate compaction
Construction during wet weather
Use of inferior quality aggregate
Insufficient binder – ageing of binder
Application of cut back bitumen covered with coarse sand or slurry seal

24. 4.Disintegration(contd..)
Stripping
Loss of aggregate
Ravelling
Pot hole
Edge breaking
Symptoms
Causes
Treatment
Bowl shaped holes of various sizes
penetration of water into the pavement
Application of premix open graded or dense graded patching or penetration patching

25. 4.Disintegration(contd..)
Stripping
Loss of aggregate
Ravelling
Pot hole
Edge breaking
Symptoms
Causes
Treatment
Irregular breakage leading to peeling of surface
penetration of water into the pavement
patching

26. Formative assessment (Multiple Choice Question) (Answer the following questions as the reflection of the material which you have seen in the above presentation)

27. Question number 1
Bowl shaped holes of various sizes is the symptoms of _____________ type of failure
Cracks
Surface defects
Disintegration
deformation

28. Question number 2
__________is one type of deformation failurein flexible pavement
Stripping
Corrugation
Longitudinal crack
Streaking

29. Question number 3
Excessive deflection due to unstable sub- grade results in _________failure
Longitudinal crack
Alligator crack
Edge crack
Reflection crack

30. Thank you