Visual Assessement of Flexible Pavement Zarikh

A Guide To The Visual Assessement Of Flexible Pavement Surface Conditions

Cawangan Jalan, Ibu Pejabat JKR, K.L

FOREWORD

In Malaysia as well as in most other countriesin the world, the road network remains the pre-dominant mode of transportation facility. Toensure its continued efficiency and accessibili-ty, the road network has to be maintained to ahigh standard. Research work carried out atInstitut Kerja Raya Malaysia (IKRAM) hasenable Jabatan Kerja Raya (JKR) Malaysia tounderstand and develop improved techniquesfor the maintenance of the road network.

It is the aspiration of JKR to be able to sharethis knowledge with those that are involved inroad building and maintenance activities. It istherefore my pleasure to introduce this first edi-tion of A Guide to Visual Assessment ofFlexible Pavement Surface Conditions.

This guide, which is the first part of a series ofguidelines on road maintenance techniques hasa two fold purpose. Firstly, it is to encouragethe usage of common nomenclature for the var-ious pavement conditions and secondly it hopesto promote more effective maintenance workswith the indication of the possible causes ofeach different type of pavement distress andtheir probable treatments.

It is my hope that this guideline will be of helpto all who are involved in road maintenanceactivities and contribute significantly towardsbetter maintenance techniques.

(Tan Sri Dato' Ir. Wan A. Rahman Yaacob)Director General of Public WorksJabatan Kerja Raya Malaysia

ACKNOWLEDGEMENT

This guide is prepared by the PavementResearch Unit (Head: Ir Mohamed ShafiiMustafa). The authors of this guideline are IrKoid Teng Hye, Ir Mohamed Shafii Mustafa,Mohd Sabri Hasim, Abd. Mutalif K. A. Abd.Hameed and Ahmad Fauzi Abdul Malek. Thedocument forms part of a series of guidelineson the design, construction and maintenance offlexible pavements which the PavementResearch Unit produces as part of their studies.

The guide was reviewed by a Committee head-ed by the Director of IKRAM, Ir Ng ChongYuen. Other members of the Committee were

Ir. Han Joke Kwang - IKRAM

Ir. Aik Siaw Kong - Road Maintenance, Roads Branch

Ir. Tai Meu Choi - Road Maintenance, Roads Branch

Ir. Zainol Rashid Zainuddin - Road Maintenance, Roads Branch;

Ir. Lee Swee Kee - Road Design, Roads Branch.

The authors thank the Director General ofPublic Works Malaysia for his permission topublish the guideline.

FOR INTERNAL USE ONLY

A GUIDE TO VISUAL ASSESSMENT OF FLEXIBLE PAVEMENT SURFACE CONDITIONS

A Guide To The Visual Assessment Of Flexible Pavement Surface Conditions.


CONTENTSPage

FOREWORD

ACKNOWLEDGEMENT

1.0. INTRODUCTION 2

CATALOGUE OF DISTRESSES IN BITUMINOUS SURFACES 3

2.0. PAVEMENT CRACKS 3

2.1. Crocodile 42.2. Block 52.3. Longitudinal 62.4. Transverse 72.5. Edge 82.6. Crescent Shaped 9

3.0. SURFACE DEFORMATIONS 10

3.1. Rutting 113.2. Corrugation 123.3. Depression 133.4. Shoving 14

4.0 SURFACE DEFECTS 15

4.1. Bleeding 164.2. Ravelling 174.3. Polishing 18 4.4. Delamination 19

5.0. PATCH 20

6.0. POTHOLE 21

7.0. EDGE DEFECTS 22

7.1. Edge Break 227.2. Edge Drop Off 23

GLOSSARY 24

REFERENCES 25

1.0. INTRODUCTION

Assessment of pavement surface conditions is

used in one form or another by most roaddepartments and/or highway authorities as ameasure of the ability of the pavement to con-tinue to provide the required service to the pub-lic. More importantly, it is used in determiningdeficiencies and inadequacies of pavements,the remedial measures to be taken, its fiscalneeds, planning and programming of pavementmaintenance and/or rehabilitation.

This guide is for the assessment of flexibleroad pavements only. Concrete pavements andunpaved roads are not covered by this guide.

The aims of this guide are :-

i) To provide a uniform nomenclature for the description of visible pavement distresses.

ii) to provide a comprehensive catalogue ofthe major visible distress types.

iii) To promote the usage of distress recognition as an aid to the diagnosis of pavement deficiencies.

Pavement distresses are categorized and quanti-fied. Illustrations of each category are providedto lend uniformity to reporting and interpreta-tion. Description of the severity of the particu-lar distress is made to conform with standardwords that express the relative severity on alow, moderate or high scale.

The following data are also provided for eachdistress type :-

i) Common synonym(s).

ii) Description of the essential features ofthe distress.

iii) Photographs of typical examples.

iv) List of probable or most likely causes.

v) List of probable treatments.




CATALOGUE OF DISTRESSES INFLEXIBLE PAVEMENTS

Manifestation of Distresses in flexible pave-ments can be categorized into one of the fol-lowing types :

a) Cracks

b) Surface deformations

c) Surface defects

d) Patches

e) Potholes

f) Eedge defects

2.0. PAVEMENT CRACKS

Cracks are fissures resulting from partial orcomplete fractures of the pavement surface.Cracking of road pavement surfaces can hap-pen in a wide variety of patterns, ranging fromisolated single crack to an interconnected pat-tern extending over the entire pavement sur-face. The detrimental effects associated withthe presence of cracks are :

i) Loss of water-proofing of the pavement layers.

ii) Loss of load spreading ability of the cracked material.

iii) Pumping and loss of fines from the base course.

iv) Loss of riding quality through loss of surfacing.

v) Loss of appearance.

The loss of load spreading ability and water-proofing will usually lead to accelerated deteri-oration of the pavement condition. The possiblecauses of cracks include :

i) Depression.

ii) Fatigue life of the surfacing being exceeded.

iii) Age embrittlement of the surfacing.

iv) Reflection of cracks in underlying layers.

v) Shrinkage.

vi) Poor construction joints.

This section includes the following types ofcracks:

i) Crocodile cracks.

ii) Block cracks.

iii) Longitudinal cracks.

iv) Transverse cracks.

v) Edge cracks.

vi) Crescent shaped cracks.

The general form of the various types of cracksis illustrated in Fiqure 1.

FIGURE 1 : TYPES OF CRACK




CROCODILE CRACKS

2.1. CROCODILE CRACKS

SYNONYMS

Alligator, chicken wire, fish net, polygonal,fatigue cracks.

DESCRIPTION

Crocodile cracks are interconnected or inter-laced cracks which form a network of multi-sided blocks resembling the skin of a crocodile.The block size can range from 100 mm toabout 300 mm.

Crocodile cracks is a consequence of the inabil-ity of the structure to support the repeated loadsdue to a "softening" of the material normally associated with increase in moisture content.The cracks in the subbase or subgrade tend to

spread rapidly under rain and traffic causingblocks of surfacing to be displaced and brokenup.

SEVERITY LEVELS

LowInterconnected or interlaced hairline cracksrunning parallel to each other; cracks notspalled.

ModerateA pattern of articulated pieces formed bycracks that may be lightly spalled. Cracks maybe sealed.

HighPieces more severely spalled at edges and loos-ened; pieces rock under traffic; pumping mayexist.

MEASUREMENTS TO BE TAKEN

a) area affected.b) predominant crack widthc) predominant cell width.


NO. POSSIBLE CAUSES PROBABLE TREATMENTS

1. Inadequate pavement thickness Strengthen the pavement or reconstruction

2. Low modulus base Strengthen the base or reconstruction

3. Brittle base Base recycling or reconstruction

4. Poor base drainage Improve the drainage and reconstruct

5. Brittle wearing course Replace or treat wearing course

High severity with severe spalling

Moderate severity with lightlyspalled cracks

Low severity with interconnected hairline cracks



BLOCK CRACKS 2.2. BLOCK CRACKS

SYNONYM

Ladder cracks.

DESCRIPTION

Block cracks are interconnected cracks forminga series of blocks, approximately rectangular inshape. Block sizes are usually greater than 300mm and can exceed 3000 mm.

SEVERITY LEVELS

LowBlocks defined by unspalled cracks with amean width of 3 mm or less; cracks withsealant in good condition.

ModerateBlocks defined by moderately spalled cracks;cracks with a mean width greater than 3 mm.

HighBlocks well defined by severely spalled cracks.


a) area affected.b) predominant crack width.c) predominant cell width.


NO. POSSIBLE CAUSES PROBABLE TREAMENTS

1 Joints in underlying layer Crushed aggregate overlay

2 Shrinkage and fatigue of underlying cemented materialReplace underlying cemented materials

3 Shrinkage cracks (due to bitumen seal hardening) in bituminous surfacingSeal cracks or replace bituminoussurfacing

4 Fatigue cracks in embrittled bituminous wearing courseCut and patch or crushed aggregateoverlay

Low severity with cracks' width < 3 mm

Moderate severity with cracks' width > 3 mm

High severity with severely spalled cracks



LONGITUDINAL CRACKS 2.3. LONGITUDINAL CRACKS

SYNONYM

Line cracks

DESCRIPTION

Longitudinal cracks are cracks which are usual-ly straight and parallel to the centre line, situat-ed at or near the middle of the lane. It can hap-pen singly or as series of almost parallel cracksor with some limited branching.

SEVERITY LEVELS

LowCracks with low severity or no spalling; meanunsealed crack width of 3 mm or less.

ModerateCracks with moderately severe spalling; meanunsealed crack width of greater than 3 mm;sealant material in bad condition.

HighCracks with high severity spalling.


a) width of dominant crack.b) length of dominant crack. c) spacing.d) area affected.


High severity with multiple spalled cracks

Moderate severity with crack's width > 3 mm

Low severity single crackwithout any spalling

NO POSSIBLE CAUSES PROBABLE TREATMENTS

1 reflection of shrinkage cracks cut and patch

2 poorly constructed paving lanein bituminous surfacing replace bituminous surfacing

3 displacement of joints at pavementwidening reconstruction of joints

4 differential settlement between cut and fill reconstruction

5 reflection of joints in the underlyingbasecrushed aggregate overlay or reconsstruction of joints



TRANSVERSE CRACKS 2.4. TRANSVERSE CRACKS

Transverse cracks are unconnected cracks run-ning transversely (relatively perpendicular topavement centre line) across the pavement.

SEVERITY LEVELS

LowCracks with low severity or no spalling; meanunsealed crack width of 3 mm or less; sealantmaterial in good condition.

ModerateCracks with moderate severity spalling; meanunsealed crack width of greater than 3 mm;sealant material in bad condition.

HighCracks with high severity spalling.


a) predominant crack width. b) spacing.c) length.d) area affected.

.


High severitywith spalling

Moderate severity with crack's width > 3 mm

Low severity with crack's width< 3 mm without any spalling


1. Reflection of shrinkage cracks Cut and patch

2. Construction joint in bituminous surfacing Ccrack sealant

3. Structural failure of portland cement concrete base Rreconstruction of base

4. Shrinkage crack in bituminous surfacing Seal cracks or replace bituminoussurfacing

5 Reflection of joints in the underlying base Crushed aggregate overlay orreconstruction of joints



EDGE CRACKS 2.5. EDGE CRACKS

DESCRIPTION

Edge cracks are crescent shaped or fairly con-tinuous cracks, parallel to, and usually within300 mm to 600 mm of the pavement edge. Itusually occurs when paved shoulders do notexist.

SEVERITY LEVELS

LowCracks with no breakup or ravelling.

ModerateCracks with some breakup or ravelling.

HighCracks with considerable breakup or ravellingalong edge.


a) predominant crack width.b) area affected c) length


Low severity with no breakup or ravelling

Moderate severity with some breakup

High severity with considerable breakup


1. Excessive traffic loading at pavement edgeWiden the pavement or strengthen thepavement edge

2. Poor drainage at pavement edge and shoulder Improve drainage and shoulder

3. Inadequate pavement width which forces traffic too close to pavement edge Widen the pavement

4. Insufficient bearing support Reconstruction



CRESCENT SHAPED CRACKS 2.6. CRESCENT SHAPED CRACKS

SYNONYMS

Parabolic, slippage, shear cracks.

DESCRIPTION

This type of cracks are half moon or crescentshaped cracks, commonly associated withshoving, often occurring in closely spaced par-allel group. It is mainly associated with bitumi-nous layer only.

SEVERITY LEVELS

LowCracks with-no breakup or shoving.

ModerateCracks with some breakup or shoving.

HighCracks with considerable breakup or shoving.


a) predominant crack width.b) area affected.


Low severity with no breakup

Moderate severity with some breakup

High severity with considerable breakup and shoving


1. Lack of bond between wearing course and the underlying layers Cut and patch

2. Low modulus base course Reconstruction of base

3. Thin wearing course Bituminous overlay

4. Dragging of paver during laying whenbituminous mix temperatures were low Cut and patch

5. High stresses due to braking and acceleration movementsBituminous overlay with stiffer mix or use high compaction mix (HCM)



3.0. SURFACE DEFORMATIONS

Deformation takes place when a road surfaceundergoes changes from ifs original construct-ed profile. It may occur after construction dueto trafficking or environmental influences. Insome cases, deformation may be built into anew pavement owing to inadequate controlduring construction. It influences the ridingquality of a pavement and may reflect structur-al inadequacies. It may lead to cracking of thesurface layer.

The major types of surface deformation cov-ered in this section are :

i) rutting.ii) corrugation.iii) depression.iv) shoving.

The general form of the various types of sur-face deformation is illustrated in Figure 2.


FIGURE 2 : TYPE OF SURFACE DEFORMATION



RUTTING 3.1. RUTTING

SYNONYMS

Longitudinal rut.

DESCRIPTION

Rutting is longitudinal deformation or depres-sion in the wheel paths which occur afterrepeated applications of axle loading. It mayoccur in one or both wheel paths of a lane. Thelength to width ratio would normally be greaterthan 4 to 1.

SEVERITY LEVELS

LowRut depths of less than 12 mm (measuredunder a transverse 1.2 m straight edge)

ModerateRut depths of between 12 mm to 25 mm (mayinclude slight longitudinal cracks).

HighRut depths of greater than 25 mm (may includemultiple longitudinal or crocodile cracks).


a) maximum depth under a transverse 1.2 m straight edge.

b) length.


Moderate severity with rut depths between 12 mm to25mm

High severity with rut depths > 25 mm

Low severity with rut depths < 12 mm


1. Inadequate pavement thickness Strengthening overlay or reconstruction

2.Inadequate compaction of structural layers Reconstruction

3. Unstable bituminous mixes Replace or recycle bituminous surfacing or use stiffer mix/HCM

4. unstable shoulder materials which do not provide adequate lateral support

shoulder improvement and overlay rutted area with bituminous surfacing

5.Overstressed subgrade which deformspermanently Reconstruction

6. Unstable granular bases or sub-bases Base or sub-base strengthening



CORRUGATIONS 3.2. CORRUGATIONS

SYNONYM

Rippling

DESCRIPTION

Corrugations are regular transverse undula-tions, closely spaced alternate valleys andcrests with wavelengths of less than 2 m.Generally, it will result in a rough ride and willbecome worse with time.

SEVERITY LEVELS

LowNoticeable (based on observation of its appear-ance and its effect on riding quality).

Moderate Rough ride.

HighVery rough ride. Vehicle may lose controlbecause of its presence.


a) maximum depth under 1.2 m straight edge.

b) crest to crest spacing.c) length of pavement affected.


High severity causing very rough ride

Moderate severity causing rough ride

Low severity - noticeable


1. Inadequate stability of bituminous surface Replace bituminous surface

2. Compaction of base in wave form Base reconstruction

3. Faulty paver behaviour with some mixes Replace the faulty mixes and correctthe faulty paver behaviour

4. Heavy traffic on steep downgrade orupgrademill off corrugated surface and replacewith stiffer mix or use HCM

5. Stopping at intersection stop lightsor roundaboutMill off corrugated surface and replacewith stiffer mix or use HCM

6. Inadequate stability of base course Base reconstruction



DEPRESSIONS 3.3. DEPRESSIONS

SYNONYM

Distortions.

DESCRIPTION

Depressions are localized areas within a pave-ment with elevations lower than the surround-ing area. They may not be confined to wheelpaths only but may extend across several wheelpaths. Generally, it results from settlement,slope failure, or volume changes due to mois-ture changes.

SEVERITY LEVELS

LowNoticeable swaying motion. Good control ofvehicle still present. (Based on the interactionbetween vehicle and pavement surface depres-sion).

ModerateFair control of vehicle when driving over pave-ment.

HighPoor control of vehicle when driving overpavement with driver always having to antici-pate depression ahead.


a) maximum depth under 1.2 m straight edge.

b) area of depression.


Low severity with noticeableswaying motion

Moderate severity with fair control of vehicle

High severity with poorcontrol of vehicle


1. differential settlement of subgrade or basematerials subgrade or base reconstruction

2. settlement of services and/or wideningtrenchesreconstruction of services and/orwidening trenches

3. volume change of subgrade due toenvironmental influencesimprove sub-soil drainage andreconstruct

4. settlement due to instability ofembankment embankment stabilization



SHOVINGS 3.4, SHOVINGS

DESCRIPTION

Shoving is the bulging of the road surface gen-erally parallel to the direction of traffic and/orhorizontal displacement of surfacing materials,mainly in the direction of traffic where brakingor acceleration movements occur, caused bytraffic pushing against the pavement.Transverse shoving may arise with turningmovements.

SEVERITY LEVELS

LowNoticeable. (Based on observation of itsappearance and its effect on riding quality).

Moderate Rough ride.

HighVery rough ride. Vehicle may lose controlbecause of its presence.


a) maximum depth of bulge under 1.2 m straight edge from high point.

b) area affected.


Low severity with noticeable swaying motion

Moderate severity resulting in rough ride

High severity resultingin very rough ride


1. Low stability mix Mill off and replacehe bituminous surfacing

2.Lack of bond between asphalt surface and underlying layer which may be caused byexcessive tack coat acting as lubricant

Replace bituminous surfacing with lower binder content mix

3. Ustable granular base reflecting through thesurface Base reconstruction

4. Stop and start of vehicles at intersections orroundaboutMill off and replace with stiffer mix oruse HCM

5. Inadequate pavement thickness Bituminous overlay or reconstruction



4.0. SURFACE DEFECTS

Surface defects cover loss of surfacing materi-als, loss of surface micro and macro textures.While they do not usually indicate pavementstructural inadequacy, they have a significantinfluence on the serviceability and safety of apavement, especially with regard to skid resist-ance, maneuverability and riding quality. Somedefects, if not corrected, may lead to subse-quent loss of pavement structural integrity.

The major types of surface defects are:

i) bleeding.ii) ravelling. iii) polishing. iv) delamination.

The general form of the various defect types isillustrated in Figure 3.


FIGURE 3 : TYPES OF SURFACE DEFECTS



BLEEDING 4.1. BLEEDING

SYNONYMS

Flushing, fatting, slick, black spot.

DESCRIPTION

Bleeding is the presence of free bitumen binderon the surface resulting from upward migrationof the binder, causing low texture depth andinadequate tyre to stone contact. It is most like-ly to occur in the wheel paths during hotweather.

SEVERITY LEVELS

LowColouring of pavement surface visible.

ModerateDistinctive appearance with excess bitumenalready free.

HighFree bitumen which gives the pavement sur-face a wet look. Tyre marks are evident.


a) area affected.b) percentage by area of stone immersed.


Low severity with visible colouring of pavement surface

Moderate severity with excess bitumen already free

High severity which gives the pavement surface a wet look


1.

Excessive application of binder with respect to thestone size. On hot days, the binder expands into airvoids; if volume of air voids is too low, continuedexpansion results in lower stability of the mix with theconsequence that traffic will force out excess binder tothe surface.

Apply hot sand to blot up theexcess binder

2.Paving over flushed surfaces. The excess bitumen onthe old surface maycoat be pumped up through the new paving over a period of time

Apply hot sand or aggregate seal coat

3. Paving over excessively primed surfaces Apply hot sand



RAVELLING 4.2. RAVELLING

SYNONYM

Fretting.

DESCRIPTION

Ravelling is the progressive disintegration ofthe pavement surface by loss of binder oraggregates or both.

SEVERITY LEVELS

LowWearing away of the aggregate or binder hasstarted but has not progressed significantly.

ModerateAggregate and/or binder has worn away andthe surface texture is becoming rough and pit-ted. Loose particles generally exist.

HighAggregate and/or binder has worn away andthe surface texture is very rough and pitted.

MEASUREMENT TO BE TAKEN

a) area affected.


High severity with rough and pitted surface

Low severity where wearing away of theaggregate has not progressed significantly

Moderate severity with worn away aggregate and binder


1. Insufficient bitumen content Thin bituminous overlay

2. Poor adhesion of bitumen binder to aggregate particles due to wet aggregate Thin bituminous overlay

3. Inadequate compaction or constructionfduring wet weather Thin bituminous overlay

4. Deterioration of binder and/or aggregate Thin bituminous overlay



POLISHING 4.3. POLISHING

DESCRIPTION

Polishing is the smoothening and rounding ofthe upper surface of the roadstone, exposingcoarse aggregate which are glossy in appear-ance and smooth to the touch. It usually occursin the wheel paths.

SEVERITY LEVELS

Not applicable. However, the degree of polish-ing may be reflected in a reduction of skidresistance.

MEASUREMENT TO BE TAKEN

a) area affected.


Smoothening and rounding of the roadstonehas progressed significantly

Coarse aggregate exposed

Smoothening and rounding of the upper sur-face of the roadstone has started


1.

Inadequate resistance to polishing of surfaceaggregates, particularly in areas of heavy traffic movements or where high stresses aredeveloped between surface and tyres

Thin bituminous overlay or use ofstiffer mix or use HCM

2. Use of naturally smooth uncrushed aggregates Thin bituminous overlay



DELAMINATION 4.4. DELAMINATION

SYNONYMS

Peeling, surface lifting, seal break, flaking

DESCRIPTION

Delamination is the loss of a discrete and large(minimum 0.01 square metre) area of the wear-ing course. Usually there is a clear delineationof the wearing course and the layer below.

SEVERITY LEVELS

LowPeeling of the top layer has started but has notprogressed significantly. Surface area peeledoff is less than 0.1 m2.

ModerateSurface area peeled off is between 0.1 m2 to2.5 m2. Severe crocodile cracks in and aroundthe peeled off area.

HighA group of more than two (2) moderate delam-inations along a short stretch of road.


a) thickness of layer(s) peeled off.b) area of individual delaminations.c) number of delaminations.


Moderate severity with surface area peeled off between 0.1 m2 and 2.5 m2

High severity with group of delaminations

Low severity where peeling of the top surface has started


1. Inadequate cleaning or inadequate t coatobefore placement of upper layers Tack mill off and re-lay upper layers

2.Seepage of water through asphalt, especially in cracks, to break bond betweensurface and lower layers

Replace wearing course or thinbituminous overlay

3. Weak, loose layer immediately underlyingseal Reconstruction of weak layers

4. Adhesion of surface binder to vehicle tyres Thin bituminous overlay



PATCH 5.0. PATCH

DESCRIPTION

A patch is a repaired section of pavementwhere a portion of the pavement surface hasbeen removed and replaced (see FIGURE 4). Itmay or may not be associates) with either aloss of serviceability (apart from a loss ofappearance) or structural capacity. The `extentand frequency of patching can be useful indica-tors of the structural adequacy of the pavement.Defects can occur within a patch or the patchcan be a further defect where it is raised ordepressed below the level of the pavement sur-face.

SEVERITY LEVELS

LowPatch is in good condition or has low severitydistress of any type. ModeratePatch has moderate severity distress of anytype.

HighPatch has high severity distress of any type.


a) area of patch at each severity level.b) number of patches at each severity level.


Patch with high severity distress

Patch with moderate severity distress

Patch with low severity distress

FIGURE 4 : PATCH AND POTHOLE



POTHOLE 6.0. POTHOLE

DESCRIPTION

Pothole is bowl shaped cavity in the pavementsurface resulting from the loss of wearingcourse and binder course materials (see FIG-URE 4). They are produced when trafficbreaches small pieces of the pavement surfaceallowing the entry of water. These spots disin-tegrate because of the weakening of the basecourse or poor quality surfacing. Free watercollecting in the hole and the underlying baseaccelerates its development.

SEVERITY LEVELS


a) depth of pothole.b) area of pothole.c) number of potholes at each severity level.

.


Low severity with area < 0.3 m2 and depth < 25 mm

Moderate severity with depth between 25 mm to 50 mm and area < 0.3 m2

Group of potholes with depth > 50 mmand area > 0.1 m2

AREA (square metre)

DEPTH (mm) < 0.1 0.1 -0.3 > 0.3< 25 Low Low Moderate25-50 Moderate Moderate High> 50 Moderate High High


1. Loss of surface course Patching

2. Moisture entry to base course through a crackedpavement surface Cut and patch

3. Load associated disintegration of base Base reconstruction

A Guide To The Visual Assessment Of Flexible Pavement Surface Conditions


FIGURE 5 : TYPES OF EDGE DEFECTS

7.0. EDGE DEFECTS

Edge defects occur along the interface of flexi-ble pavement and the shoulder, and are mostsignificant where the shoulder is unsealed. Thedetrimental effects of edge defects include :

i) reduction of pavement width.

ii) loss of quality of ride and possible loss of control of vehicle.

iii) channelling of water at the edge of the pavement leading to erosion of shoulder.

iv) entry of water into base.

The defect types covered in this section are

i) edge break.

ii) edge drop-off.

The general form is illustrated in Figure 5.

EDGE BREAKS

7.1. EDGE BREAKS

DESCRIPTION

Edge break occurs when the edge of the bitu-minous surface are fretted, or broken.

SEVERITY LEVELS

Not applicable.

MEASUREMENTS TO BE TAKENa) length over which break occurs.b) maximum width of surfacing loss.


Significant length of edge break and surfacing loss

Edge break with considerable breakup

Edge break has just started



EDGE DROP-OFFS 7.2. EDGE DROP-OFFS

DESCRIPTION

Edge drop-off is the difference in elevationbetween the traffic lane and outside shoulder;typically occurs when the outside shoulder set-tles or erodes. It is not usually considered adefect if the drop-off is less than 25 mm.

SEVERITY LEVEL

Not applicable. However, severity levels can bedefined in relation to the height of drop.


a) height of drop.b) length affected.


NO POSSIBLE CAUSES PROBABLE TREATMENTS1. Inadequate pavement width Widen the pavement

2. Alignment which encourages driverstotravel on pavement edge Pavement widening and realignment

3. Inadequate edge support Shoulder strengthening

4. Edge drop-off Sstrengthening and levelling of shoulderwith road surface5. Loss of adhesion to base Cut and patch or bituminous overlay

Slight drop-off

Significant drop-off

Height of drop > 100 mm. It is a danger to traffic

No. POSSIBLE CAUSES PROBABLE TREATMENTS

1 Inadequate pavement width Widen the pavement

2 Shoulder material with inadequate resistance to erosion and abrasion Replace shoulder material and reconstruct

3 Resurfacing of pavement without resurfacing of shoulder Levelling of shoulder with road surface



GLOSSARY

BinderBrown or black adhesive mate rial

Bituminous overlayA method of treat ment where the existingpave ment surface is overlaid with bituminousmaterials

BleedingIdentified by a film of bitumi nous material onthe pavement surface that creates a shiny, glass-like, reflective surface that nay be tackyto the touch

Block crackThe occurrence of cracks that divide the bitu-minous surface into approximately rectangularpieces, typically 0.1 m2 or more in size

Centre lineThe white/yellow separating traffic travelling inopposite direction

Construction jointThe point at which work is concluded andreinitiated when building a pavement

CorrugationRegular transverse undulations, closely spacedalternate valleys and crests with wavelengths ofless than 2 m.

Crescent shaped crackCrack which is half moon or crescent in shape,normally associated with shoving

Crocodile crackInterconnected or interlaced crack which forma network of multisided blocks; the block sizesare smaller than 300 mm.

Cut and patchA treatment where the distressed area is exca-vated and patched back with bituminous mate-rials

DelaminationLoss of a discrete and large (minimum 0.01m2) area of the top bituminous layer

DepressionLocalized area within a pavement with eleva-tions lower than the surrounding area

Edge breakBroken or fretted pavement edge

Edge crackFracture along the pavement edge

Edge drop-offThe difference in elevation between the trafficlane and the shoulder

Hairline crackA fracture that is very narrow in width

LongitudinalParallel to the centre line of the pavement

PatchAn area where the pavement has been removedand replaced with a new material

PolishingSmoothening of the upper surface of the roadstone, exposing coarse aggregate, which areglossy in appearance and smooth to the touch

PotholeA bowl-shaped cavity in the pavement surface

PumpingThe ejection of water and fine materials underpressure through cracks under moving loads

RavellingThe wearing away of the pavement surfacecaused by the loss of binder or the dislodgingof aggregate particles or both

RuttingThe occurrence of longitudinal surface depres-sion/deformation in the wheel paths




ShovingPermanent, longitudinal displacement of alocalized area of the pavement surface causedby traffic pushing against the pavement

SpallingBreaking or cutting off small pieces from thepavement surface

TransversePerpendicular to the centre line of the pave-ment

REFERENCES

1. A Guide to the Visual Assessment of Pavement Condition, National Association of Australia State Road Authorities, 1987.

2. Distress Identification Manual for the Long-Term Pavement Performance Studies, SHRPLTPP/FR-90-001, Strategic Highway Research Program, National Research Council, Washington, D.C. 1990.

3. Manual for Condition Rating of Flexible Pavements - Distress Manifestation, G.J. Chong, W.A. Phang and G.A. Wrong; Reprinted January 1982.

4. Various Research Findings at IKRAM.


A GUIDE TO VISUAL ASSESSMENT OF FLEXIBLE PAVEMNT SURFACE CONDITIONSFOREWORDACKNOWLEDGEMENTCONTENTS1.0 INTRODUCTIONCATALOGUE OF DISTRESSES IN FLEXIBLE PAVEMENTS

2.0 PAVEMENT CRACKS2.1 Crocodile CracksSynonymsDescriptionSeverity LevelsMeasurements To Be Taken

2.2 Block CracksSynonymDescriptionSeverity LevelsMeasurements To Be Taken

2.3 Longitidinal CracksSynonymDescriptionSeverity LevelsMeasurements To Be Taken

2.4 Transverse CracksSeverity LevelsMeasurements To Be Taken

2.5 Edge CracksDescriptionSeverity LevelsMeasurements To Be Taken

2.6 Crescent Shaped CracksSynonymDescriptionSeverity LevelsMeasurements To Be Taken

3.0 SURFACE DEFOMATIONS3.1 RuttingSynonymsDescriptionSeverity LevelsMeasurements To Be Taken

3.2 CorrugationsSynonymDescriptionSeverity LevelsMeasurements To Be Taken

3.3 DepressionsSynonymDescriptionSeverity LevelsMEasurements To Be Taken

3.4 ShovingsDescriptionSeverity LevelsMeasurements To Be Taken

4.0 SURFACE DEFECTS4.1 BleedingSynonymsDescriptionSeverity LevelsMeasurements To Be Taken

4.2 RavellingSynonymDescriptionSeverity LevelsMeasurements To Be Taken

4.3 PolishingDescription Severity LevelsMeasurements To Be Taken

4.4 DelaminationSynonymsDescriptionSeverity LevelsMeasurements To Be Taken

5.0 PATCHDescriptionSeverity LevelsMeasurements To Be Taken

6.0 POTHOLEDescription Severity LevelsMeasurements To Be Taken

7.0 EDGE DEFECTS7.1 Edge BreaksDescription Severity LevelsMeasurements To Be Taken

7.2 Edge Drop-offsDescriptionSeverity LevelsMeasurements To Be Taken

GLOSSARYREFERENCES

Documents

Visual Assessement of Flexible Pavement Zarikh