pdce

“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 .

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

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.

COMPONENTS OF FLEXIBLE

PAVEMENT

Flexible pavement failures are fatigue cracking, rutting, andthermal cracking. The fatigue cracking of flexible pavementis due to horizontal tensile strain at the bottom of theasphaltic concrete.

The failure criterion relates allowable number of loadrepetitions to tensile strain and this relation can bedetermined in the laboratory fatigue test on asphalticconcrete specimens.

Rutting occurs only on flexible pavements as indicated bypermanent 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 ofsub-grade and other to limit rutting to a tolerable amount(12 mm normally. Thermal cracking includes both lowtemperature cracking and thermal fatigue cracking.

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

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

COMMON FLEXIBLE PAVEMENT FAILURE/ DESTRESSES

Cracking

Deformation

Deterioration

Mat problems

Problems associated with seal coats

Distresses in Flexible Pavements

General Causes

(Fatigue Cracking)

(Rutting)

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,

Delamination

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

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

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.

Reflection Cracking:

Cracks in HMA overlay surfaces that occur over joints in

concrete or over cracks in HMA pavements.

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.

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.

Rutting:

Longitudinal surface depression that develops in the wheel

paths of flexible pavement under traffic. It may have

associated transverse displacement.

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.

Depression:

Small, localized surface settlement that can cause a rough,

even hazardous ride to motorists.

Overlay Bumps:

In newly overlaid pavements, bumps occur where cracks in

old pavements were recently filed. This problem is most

prevalent on thin overlays.

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.

Pot holes:

Bowl-shaped holes of various sizes in the pavement surface.

Minimum plan dimension is 150 mm.

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.

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.

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.

Polished aggregate:

Surface binder worn away to expose coarse aggregate.

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.

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.

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.

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

• 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.

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)

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)

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

Plate Load Test – Field test

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

Deflection measurement as an

evaluation toolBenkelman beam deflection method

Benkelman Beam Deflection Test

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.

Pavement Evaluation Survey

Falling Weight Deflectometer

Deflection Basin


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.


• FWD data includes: Load applied, Load plate radius,surface deflections at different radial distances Data isused to back-calculate the material properties andthicknesses of different layers of flexible pavement.

Structural Evaluation using FWD

Pavement Evaluation SurveyImportant Characteristics of Recommended Equipment for

Data collection

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

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

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

Microsurfacing in Progress

MICROSURFACING ON ROAD

ONE HOUR

SIX

MONTHS

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.

Roadside and drainage maintenance

Clearing and cleaning of drains.

Reshape/re-grade ditch, line drain.

Clear manhole and underground

pipes.

Erosion repair.

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

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.

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 forStrengthening of Flexible Road Pavements UsingBenkelman Beam Deflection Technique.

REFERENCES

4. file:///C:/Users/asus/Downloads/2-77-1444048014-1.eng-STRENGTHENING%20OF%20FLEXIBLE%20PAVEMENT-NABEEL%20YOUSUF.pdf

5. http://en.wikipedia.org/wiki/flexible_pavement

6. NPTEL,http://nptel.ac.in/

C:/Users/asus/Downloads/2-77-1444048014-1.eng-STRENGTHENING OF FLEXIBLE PAVEMENT-NABEEL YOUSUF.pdf

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