HOW FAILURES OCCURS IN FLEXIBLE PAVEMENTS , ITS EVALUATION AND STRENGTHENING TOTALLY DESCRIBE IN THIS PRESENTATION.

1. “Failures in flexible pavements,
its evaluation and strengthening ”
PRESENTED BY :
SOLANKI KALPESH J.
(160900713017)
Department of Civil Engineering
Tatva Institute Of Technological Studies, Modasa
GUJARAT TECHNOLOGICAL
UNIVERSITY
GUIDED BY:
Dr. H. R. VARIA
Principal T.I.T.S Modasa .

2. CONTENT
 INTRODUCTION
 LOAD DISTRIBUTION IN FLEXIBLE PAVEMENTS
 TYPES OF FLEXIBLE PAVEMENTS FAILURE
 CAUSES OF PREMATURE FAILURES
 COMMON FLEXIBLE PAVEMENT FAILURE/ DESTRESSES
 TYPES OF DISTRESSES/FAILURES AND DEFINITIONS
 EVALUATION AND STRENGTHENING
 CONCLUSION
 REFERENCES

3. INTRODUCTION
 A true flexible pavement yields “elastically” to traffic
loading. It is constructed with a bituminous-treated surface
or a relatively thin surface of hot-mix asphalt (HMA) over
one or more unbound base courses resting on a sub grade.

4. COMPONENTS OF FLEXIBLE
PAVEMENT

6.  Flexible pavement failures are fatigue cracking, rutting, and
thermal cracking. The fatigue cracking of flexible pavement
is due to horizontal tensile strain at the bottom of the
asphaltic concrete.
 The failure criterion relates allowable number of load
repetitions to tensile strain and this relation can be
determined in the laboratory fatigue test on asphaltic
concrete specimens.
 Rutting occurs only on flexible pavements as indicated by
permanent deformation or rut depth along wheel load path.
Two design methods have been used to control rutting:
one to limit the vertical compressive strain on the top of
sub-grade and other to limit rutting to a tolerable amount
(12 mm normally. Thermal cracking includes both low
temperature cracking and thermal fatigue cracking.

7. TYPES OF FLEXIBLE PAVEMENTS
FAILURES
 Failures may be:
 Failure in sub grade
 Inadequate Stability
 Excessive application of stresses
 Plastic deformation
 Failures in sub base or Base course
 Inadequate stability
 Loss of binding action
 Loss of bearing course materials
 Inadequate wearing course

9. CAUSES OF PREMATURE FAILURES
 Rutting due to high variation in ambient temperature
 Uncontrolled heavy axle loads
 Limitation of pavement design procedures to meet local
environmental conditions

11. COMMON FLEXIBLE PAVEMENT
FAILURE/ DESTRESSES
 Cracking
 Deformation
 Deterioration
 Mat problems
 Problems associated with seal coats

12. Distresses in Flexible Pavements
General Causes
(Fatigue Cracking)
(Rutting)

13. Category Distress type
Cracking Longitudinal, Fatigue, Transverse,
reflective, block ,edge
Deformation Rutting, Corrugation, Shoving, depression,
overlay bumps
Deterioration Delimitation, Potholes, Patching, raveling,
stripping, Polished aggregate, Pumping
Mat Problems Segregation, Checking, Bleeding
Seal coats Rock loss, Segregation, bleeding/fat spots,

14. TYPES OF DISTRESSES/FAILURES AND
DEFINITIONS
 Longitudinal Cracking: Cracks that are approximately
parallel to pavement centerline and are not in the wheel
path.
 Longitudinal cracks are non-load associated cracks.
Location within the lane (wheel path versus non-wheel
path) is significant.
 Longitudinal cracks in the wheel path are normally rated as
Alligator ‘A 'cracking

16. Fatigue Cracking:
Cracks in asphalt layers that are caused by repeated traffic
loadings. The cracks indicate fatigue failure of the asphalt
layer. When cracking is characterized by interconnected
cracks, the cracking pattern resembles that of an alligator’s
skin or chicken wire. Therefore, it is also referred to as
alligator cracking

17. Transverse Cracking:
Cracks that are predominately perpendicular to pavement
centerline and are not located over Portland cement concrete
joints. Thermal cracking is typically in this category.

18. Reflection Cracking:
Cracks in HMA overlay surfaces that occur over joints in
concrete or over cracks in HMA pavements.

19. Block Cracking:
Pattern of cracks that divides the pavement into
approximately rectangular pieces. Rectangular blocks range
in size from approximately 0.1 square yard to 12 square
yards.

20. Edge Cracking:
Crescent-shaped cracks or fairly continuous cracks that
intersect the pavement edge and are located within 2 feet of
the pavement edge, adjacent to the unpaved shoulder.
Includes longitudinal cracks outside of the wheel path and
within 2 feet of the pavement edge.

21. Rutting:
Longitudinal surface depression that develops in the wheel
paths of flexible pavement under traffic. It may have
associated transverse displacement.

22. Shoving:
A longitudinal displacement of a localized area of the
pavement surface. It is generally caused by braking or
accelerating vehicles, and is usually located on hills or
curves, or at intersections. It also may have vertical
displacement.

23. Depression:
Small, localized surface settlement that can cause a rough,
even hazardous ride to motorists.

24. Overlay Bumps:
In newly overlaid pavements, bumps occur where cracks in
old pavements were recently filed. This problem is most
prevalent on thin overlays.

25. Delamination:
Loss of a large area of pavement surface. Usually there is a
clear separation of the pavement surface from the layer
below. Slippage cracking may often occur as a result of poor
bonding or adhesion between layers.

26. Pot holes:
Bowl-shaped holes of various sizes in the pavement surface.
Minimum plan dimension is 150 mm.

27. Patching:
Portion of pavement surface, greater than 0.1 sq. meter, that
has been removed and replaced or additional material applied
to the pavement after original construction.

28. Raveling:
Wearing away of the pavement surface in high-quality hot mix
asphalt concrete that may be caused by the dislodging of
aggregate particles and loss of asphalt binder.

29. Stripping:
The loss of the adhesive bond between asphalt cement and
aggregate, most often caused by the presence of water in
asphalt concrete, which may result in raveling, loss of
stability, and load carrying capacity of the HMA pavement or
treated base.

30. Polished aggregate:
Surface binder worn away to expose coarse aggregate.

31. Segregation:
Separation of coarse aggregate from fine aggregate as a
result of mishandling of the mix at several points during mix
production, hauling, and placing operations. Segregation
leads to non-uniform surface texture and non-uniform
density.

32. Checking:
Short transverse cracks, usually 1 to 3 inches in length and 1
to 3 inches apart, which occur in the surface of the HMA mat
at some time during the compaction process. The cracks do
not extend completely through the depth of the course, but
are only about ½inch deep.

33. Bleeding/Flushing:
Excess bituminous binder occurring on the pavement
surface. May create a shiny, glass-like, reflective surface that
may be tacky to the touch. Usually found in the wheel paths.

34. EVALUATION AND STRENGTHENING
• Evaluation:
Evaluation of pavement is done under following
categories:
 Functional Evaluation
 Structural Evaluation
 Material durability
 Shoulder condition
 Extent of maintenance activity performanced in last
 Variation of pavement condition

35. • The structural evaluation of pavement can be broadly
classified into two major categories, namely,
DESTRUCTIVE EVALUATION and NONDESTRUCTIVE
(NDT) EVALUATION.
• In Non-destructive evaluation the structural strength of the
pavement is evaluated without causing any damage to the
pavement or disruption of traffic.
• A number of Non-destructive devices have been
developed for the structural evaluation of pavement. The
Non-destructive equipment is used to determine the;
• (i) In -situ module of pavement layers, (ii) Load transfer
efficiency at joints in the concrete pavements, and (iii)
Location and extent of void in a pavement structure.

36. Destructive or Non-destructive Evaluation:
Destructive Evaluation
• Pavement is cut open for in-situ and lab tests (e.g. density,
moisture, strength)
Non-destructive Evaluation
• Pavement subjected to applied loading and the structural
response is measured
(e.g. Benkelman Beam, Dynaflect, FWD, GPR)

37. Non destructive tests (NDT) – The application of load can
be in different modes
• Static load (Plate Load Test)
• Slow moving or creep load (Benkelman Beam Deflection
Test)
• Vibratory load (Dynaflect)
• Impulse load (Falling Weight Deflectometer)
Electromagnetic wave transmission and reflection in
layered media
• Ground Penetrating Radar (GPR)

38. METHODS OF EVALUATION OF
MATERIAL PROPERTIES
 Plate – loading test
 Triaxial compression test
 California Bearing Ratio Test
 Test of Bituminious Mixtures
 Resilient Modulus test
 Dynamic modulus test
 Poission's ratio
 Fatigue testing

39. Plate Load Test – Field test

40. METHODS OF STRUCTURAL
EVALUATION
Evaluation of structural and adequacy of a pavement
and the redesign of the pavement dependent upon the
engineer's ability to evaluate the structural properties
of the pavement components.
Methods :
 California Bearing Ratio
 Plate bearing test
 Non-Destructive Field test
 Laboratory test
 Moisture test

41. Deflection measurement as an
evaluation tool
Benkelman beam deflection method
Benkelman Beam Deflection Test

42. Benkelman Beam Evaluation of
Pavements
Single maximum deflection (actual or rebound) is measured
Structural response is measured under static or creep load
condition.
Not representative of last moving traffic loads Interpretation
about the structural condition of the total pavement structure
and the remaining life is made on the basis of this single
deflection.

43. Pavement Evaluation Survey
Falling Weight Deflectometer
Deflection Basin

44. Pavement Evaluation Survey
Structural Evaluation using FWD
FWD – applying impulse load on pavement, measures the
shape of the deflection bowl More than one surface
deflection is measured Reliable interpretation of different
layers Raise a specified mass to specified height fall freely
on a loading plate placed on the pavement surface through
a spring Mass, height, stiffness of the spring selected such
to produce load magnitude and duration similar to load
pulses produced by moving traffic.

45. Pavement Evaluation Survey
• FWD data includes: Load applied, Load plate radius,
surface deflections at different radial distances Data is
used to back-calculate the material properties and
thicknesses of different layers of flexible pavement.
Structural Evaluation using FWD

46. Pavement Evaluation Survey
Important Characteristics of Recommended Equipment for
Data collection

47. Pavement Evaluation Survey
Important Characteristics of Recommended Equipment for
Data collection

48. MAINTENANCE OF FLEXIBLE
PAVEMENTS
Problems with bituminous surfacings
 Cracking due to brittleness at low temperature
 Stripping due to rains and melting of snow
 Ravelling and formation of potholes
 Skidding
 Distress at gradients
 Oxidation due to exposure to UV rays
 Effect of snow, land slides
 Limited work year and non availability of machinery

49. TECHNOLOGICAL OPTIONS FOR
SUSTAINABLE MAINTENANCE OF ROADS
Materials
Modified bitumens
Bitumen emulsions
Modified bitumen emulsions
Adhesion promoters
Anti-oxidants
Ready made patching mixes
Multi grade bitumens

50. Technological options for sustainable
maintenance of roads
Techniques
Cold mixed premix carpet
Cold mixed semi dense bituminous concrete
Porous asphalt
Microsurfacings
Slurry sealing
Fog seal

51. Microsurfacing in Progress

52. MICROSURFACING ON ROAD
ONE HOUR
SIX
MONTHS

53. Surface maintenance
Periodic re-shaping of the road surface to ensure proper
drainage and traffic passage.
Purpose of road surface maintenance:
 To provide safety to users.
 Improve road performance.
 lengthen maintenance cycles.
 Reduce maintenance costs.

54. Roadside and drainage maintenance
 Clearing and cleaning of drains.
 Reshape/re-grade ditch, line drain.
 Clear manhole and underground
pipes.
 Erosion repair.

55. o The pavement should be designed with precise future
forecasting.
o The pavement should be constructed as per design only.
o The pavement should be maintained periodically...i.e. on the
maintenance concept of routine, Periodic & complete
maintenance.
CONCLUSION

56. CONCLUSION
oThe road user should be as per consideration only...if the
nature of traffic changes due to unexpected growth of the
area than it should be well maintained.
o There should not be any delay in maintenance.
o The nature of traffic plays vital role for the life span of
pavement so at the time of designing assumption of the
future traffic is very much important.

57. REFERENCES
1. Yoder and Witczak “Principles of Pavement Design”
John Wiley and Sons , second edition
2. IRC :37-2001, Guidelines of Design of
Flexible Pavements”
3.IRC:81 - 1997 “Tentative Guidelines for
Strengthening of Flexible Road Pavements Using
Benkelman Beam Deflection Technique.

58. REFERENCES
4. file:///C:/Users/asus/Downloads/2-77-
1444048014-1.eng-
STRENGTHENING%20OF%20FLEXIBLE%20PAVEMEN
T-NABEEL%20YOUSUF.pdf
5. http://en.wikipedia.org/wiki/flexible_pavement
6. NPTEL,http://nptel.ac.in/

59. THANK
YOU