GUIDE TO THE VISUAL ASSESSMENT OF FLEXIBLE PAVEMENT...

GUIDE TO THE VISUAL ASSESSMENT OF FLEXIBLE PAVEMENT SURFACE CONDITION

By:Norhidayu Hartaty Abdullah

Unit Forensik Keselamatan JalanBahagian Keselamatan Jalan

Cawangan Kejuruteraan Jalan & Geoteknik

Unit Forensik Keselamatan Jalan 1

Visual Assessment of Flexible Pavement Surface Condition

Assessment of Pavement Surface condition is required:•As a measure of the ability of the pavement to continue to provide the required service to the public• determining the deficiencies and inadequacies of the pavement•The remedial measures to be taken as well the maintenance planning for the pavement

Distresses in Flexible Pavement can be categorized into one of the following types:a.Cracksb.Surface Deformationsc.Surfaces Defectsd.Patchese.Potholesf.Edge Defects


FLEXIBLE PAVEMENT SURFACE CONDITION

CRACKS SURFACE DEFORMATIONS

SURFACEDEFECTS

EDGE DEFECTS

PATCH & POTHOLES

Depression

Rutting Bleeding

Polishing

Edge Break

Edge drop-off

Block

Longitudinal

Transverse

Edge

Crescent Shaped

Crocodile

Corrugation

Shoving Delamination

Ravelling


1. PAVEMENT CRACKS

The possible causes of Cracks include:I.Poor construction jointsII.ShrinkageIII.Reflection of cracks in underlying layersIV.DepressionV.Fatigue life of the surface being exceededVI.Age embrittlement of the surfacing

Effects of the Cracks:I.Loss of water-proofing of the pavement layersII.Loss of load spreading abilityIII.Pumping and loss of fines from the base courseIV.Loss of riding qualityV.Loss of appearance


PAVEMENT CRACKS

Types of Pavement Cracks:


CROCODILE CRACKS

Crocodile cracks is the consequences of the :Inability of the structure to support the repeated loads due to a ‘softening’of the material, which will increase the moisture content

No Possible Causes Probable Treatment

1 Inadequate pavement thickness

Strengthen the pavement or reconstruction

2 Low modulus base Strengthen the base/reconstruction

3 Brittle base Base recycling/reconstruction

4 Poor base drainage Improve the drainage and reconstruct

5 Brittle wearing course Replace or treat wearing course


Severity Level of Crocodile Crack

Low Severity• Hairline cracks running parallelto each other

• cracks not spalled

Moderate Severity• pattern of articulated pieces formed by cracks may be lightly spalled

• cracks maybe sealed

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Severity Level of Crocodile Crack

High Severity• pieces more severely spalled at edges and loosened

• pieces rocks under traffic; pumping may exist

Measrument to be taken in assest the crack:• area affected• predominant crack width• predominant cell width


BLOCK CRACKSalso known as Ladder Cracks

Blocks cracks are :interconnected cracks forming a series of blocks, approximately rectangular in shapes. Blocks sizes are usually greater than 300mm and can exceed 3000mm

No Possible Causes Probable Treatments1 Joints in underlying layer Crushed aggregate overlay2 Shrinkage and fatigue of

underlying cemented materialsReplace underlying cemented materials

3 Shrinkage cracks (due to bitumen hardening) in bituminous surfacing

Seal cracks or replace bituminous surface

4 Fatigue cracks in embrittledbituminous wearing course

Cut and patch or crushed aggregate overlay


Severity Level of Block Cracks

Low Severity• blocks defined by unspalled cracks with- mean width of 3mm or less- cracks with sealant in good condition

Moderate Severity

Cracks with a mean width greaterthan 3 mm

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Severity Level of Block Cracks

High Severity

Severely spalled cracks


LONGITUDINAL CRACKSalso known as Line Cracks

Longitudinal cracks are:- cracks which are usually straight and parallel to the centre line - situated at or near the middle of the lane- can happen singly or as series

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No Possible Causes Probable Treatments1 Reflection of shrinkage cracks Cut and patch2 Poorly constructed paving lane in

bituminous surfacingReplace bituminous surfacing

3 Displacement of joints at pavement widening

Reconstruction of joints

4 Differential settlement between cut and fill

reconstruction

5 Reflection of joints in the underlying base

Crushed aggregate overlay or reconstruction of joints

Severity Level of Longitudinal Cracks

Low Severity

- Single cracks without any spalling- Mean unsealed carcks width of 3mmor less

Moderate Severity

Crack’s width of greater than 3 mm

Severity Level of Longitudinal Cracks

High Severity

- Multiple spalled cracks

Measrument to be taken in assest the crack:• area affected• length of dominant cracks• width of dominant cracks• spacing


TRANSVERSE CRACKS

Transverse cracks are unconnected cracks running transversely(perpendicularly to pavement centre line) across the pavement.

No Possible Causes Probable Treatments1 Reflection of shrinkage cracks Cut and patch2 Construction joint in bituminous

surfacingCrack sealant

3 Structural failure of cement concrete base

Reconstruction of base

4 Shrinkage crack in bituminous surfacing

Seal cracks or replace bituminous surfacing

5 Reflection of joints in the underlying base

Crushed aggregate overlay or reconstrution of joints


Severity Level of Transverse Cracks

Low Severity

- crack’s width less than 3 mm without any spalling

ModerateSeverity

- crack’s width is more than 3 mm

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Severity Level of Transverse Cracks

High Severity

- high severity with spalling

Measrument to be taken in assest the crack:• area affected• spacing• length• predominant crack width


EDGE CRACKS

Edge cracks are Crescent shaped or fairly continuous cracks, parallel to, and usually within 300mm to 600mm of the pavement edge.It usually occurs when paved shoulders do not exist.

No Possible Causes Probable Treatments1 Excessive traffic loading at

pavement edgeWiden the pavement or strengthen the pavement 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


Severity Level of Edge Cracks

Low Severity

- no breakup or ravelling

ModerateSeverity- with some breakup or ravelling

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Severity Level of Edge Cracks

High Severity

- with considerable breakup or ravelling along edge

Measrument to be taken in assest the crack:• area affected• length• predominant crack width


CRESCENT SHAPED CRACKSor Parabolic, Slippage, Shear Crack

Crescent Shaped Cracks are commonly associated with shoving, often occurin closely spaced parallel group.It is mainly associated with bituminous layer only


No Possible Causes Treatment Treatments1 Lack of bond between wearing

course and the underlying layersCut and patch

2 Low modulus base course Reconstruction of base3 Thin wearing course Bituminous overlay4 Drangging of paver during laying

when bituminous mix temperature were low

Cut and patch

5 High stresses due to braking and acceleration movements

Bituminous overlay with stiffer mix or use high compaction mix

Severity Level of Crescent Shaped Cracks

Low Severity

- no breakup or shoving

Moderate Severity- with some breakup or shoving

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Severity Level of Crescent Shaped Cracks

High Severity

- with considerable breakup andshoving


2. SURFACE DEFORMATIONS

Deformation is :

- happen when a road surface undergoes changes from its original constructed profile

- occur after construction due to trafficking or environmental influences- influence the riding quality of the pavement- may reflect structural inadequancies- may lead to cracking of surface layer

Major types of Surface Deformation are:I.RuttingII.CorrugationIII.DepressionIV.Shoving


2. SURFACE DEFORMATIONS

The major types of Surface Deformation:


RUTTINGalso known as Logitudinal Rut

Rutting is longitudinal deformation or depression in the wheel paths whichoccur after repeated application of axle loading.May occur in one or both wheel paths of a lane.The length to width ratio would normally be greater than 4 to 1.

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No Possible Causes Probable Treatments

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

4 Unstable shoulder materials which do not provide adequate lateral support

Shoulder improvement and overlay rutted area with bituminous surfacing

5 Overstressed subgrade which deform permenantly

reconstruction

Severity Level of Rutting

Low Severity

Rut depths of less than 12mm (measured under a transverse 1.2m straight edge)

Moderate Severity

•Rut depths of between 12 mm to 25 mm

•May include slight longitudinal cracks

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Severity Level of Rutting

High Severity

• Rut depths of greater than 25mm• May include multiple longitudinal or crocodile cracks

Measurements to be taken in the assessment:• maximum depth under a transverse 1.2 m straight edge• length


CORRUGATIONSalso knows as Rippling

-Are regular transverse undulation, closely spaced alternate valleys and crests with wavelengths of less than 2 m- Will result in a rough ride and will become worse with time

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1 Inadequate stability of bituminous surface

Replace bituminous surface

2 Compaction of base in wave form Base reconstruction

3 Faulty paver behavior with some mixes

Replace the faulty mixes and correct the faulty paver behavior

4 Heavy traffic on steep downgrade or upgrade

Mill of corrugated surface and replace with stiffer mix

5 Stopping at intersection stop lights or roundabout

Mill off corrugated surface and replace with stiffer mix

Severity Levels of Corrugation

Low Severity-Noticeable (based on observation of its appearance and its effect on riding quality)

Moderate Severity- Cause rough ride

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Severity Levels of Corrugation

High Severity- Very rough ride. Vehicle may loose control because of its presence)

Measurements to be taken:

• Maximum depth under 1.2m straight edge• Crest to crest spacing• Length of pavement affected

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DEPRESSIONSalso known as Distortions

Depressions are localized area within a pavement with elevations lower than the surrounding area.It results from : Settlement, Slope Failure, Volume Change due to

moisture changes

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1 Differential settlement of subgrade or base materials

Subgrade or base reconstruct

2 Settlement of service and/or widening trenches

Reconstruction of services and/or widening trenches

3 Volume change of subgradedue to environmental influences

Improve sub-soil drainage and reconstruct

4 Settlement due to instability of embankment

Embankment stabilization

Severity Levels of Depressions

Low Severity- Noticeable swaying motion- vehicle is still in good control condition

Moderate Severity

- fair control of vehicle when driving over pavement

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Severity Levels of Depressions

High Severity- poor control of vehicles when drivingover pavement

- driver always having to anticipate depression ahead


• maximum depth under 1.2m straight edge• area of depression

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SHOVINGS

Shoving is :• the bulging of the road surface (generally parallel to the direction of traffic, and/or horizontal displacement of surfacing material)

• mainly in the direction of traffic where braking or acceleration movements occur• caused by traffic pushing against the pavement

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1 Low stability mix Mill off and replace the bituminous surfacing

2 Lack of bond between asphalt surface and underlying layer which may be caused by excessive tack coating

Replace bituminous surfacing with lower binder content mix

3 Unstable granular base reflecting through the surface

Base reconstruction

4 Stop and start of vehicles at intersections or roundabout

Mill off and replace with stiffer mix

Severity Levels of Shoving

Low Severity- Noticeable swaying motion- effect on riding quality

Moderate Severity- resulting in rough ride

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Severity Levels of Shoving

High Severity

- resulting in very rough ride- vehicle may loose controlbecause of its presence


• maximum depth of bulge under 1.2m straight edge from high point

• area affected

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3. SURFACE DEFECTS

• Surface defects cover loss of surfacing materials, micro and macro textures• Influenced on: the serviceability and safety of pavement (skid resistance, Maneuverability and riding quality)

The main types of Surface Defects are:I. BleedingII. RavellingIII. PolishingIV. Delamination

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SURFACE DEFECTS


BLEEDINGalso known as Flushing, Fating, Slick, Black Spot

Bleeding is the presence of free bitumen binder on the surface, most likely to occur in the wheel paths during hot weather.Result from : Upward migration of the binderEffect: cause low texture depth, inadequate tire to stone contact


1 Excessive application of binder with respect to the stone size.

Apply hot sand to blot up the excess ninder

2 Paving over flushed surfaces. Apply hot sand or aggregate seal coat

3 Paving over excessively primed surfaces

Apply hot sand

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Severity Levels of Bleeding

Low Severity-visible colouring of pavement surface

Moderate Severity- distinctive appearance with excess bitumenalready free

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Severity Levels of Bleeding

High Severity-Gives the pavement a wet look-Tire marks are evident


• Area affected• Percentage by area of stone immersed

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RAVELLINGalso known as Fretting

Ravelling is the progressive disintegration of the pavement surface by lossof binder or aggregates or both

No Possible Causes Probable Treatments1 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 construction during wet weather


4 Deterioration of binder and/or aggregates


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Severity Levels of Raveling

Low Severity- Wearing away of the aggregates has notprogressed significantly

Moderate Severity

- Aggregate/binder has worn away- The surface texture is becoming rough and pitted

- Loose particles generally exist

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Severity Levels of Raveling

High Severity- The surface texture is very rough and pitted

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POLISHING

Polishing is the smoothing and rounding of the upper surface of the roadstones,exposing coarse aggregates which are glossy in appearance and smooth to touch.Usually occurs in the wheel paths.

No Possible Causes Probable Treatments1 Inadequate resistance to polishing

of aggregates surfaceThin bituminous overlay or use stiffer mix

2 Use of naturally smooth uncrushed aggregates


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Severity Levels of Polishing

Low Severity

- smoothening and rounding of upper surfaceof the roadstone has started

Moderate Severity

- coarse aggregates exposed

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Severity Levels of Polishing

High Severity

- smoothening and rounding of theroadstone has progressed significantly

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DELAMINATIONAlso known as Peeling, Surface Lifting, Seal Break, Flaking

Delamination is the loss of a discrete and large area of wearing course.Clear delineation of the wearing course and the layer below

No Possible Causes Probable Treatments1 Inadequate cleaning or inadequate

tack coat before placement of upper layers

Mill off and re-lay upper layers

2 Seepage of water Replace wearing course or thin bituminous overlay

3 Weak, loose layer immediately underlying seal

Reconstruction of weak layers

4 Adhesion of surface binder to vehicle tyres


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Severity Levels of Delamination

Low Severity

- peeling of the top surface has started

Moderate Severity

- surface area peeled off between 0.1m2 to 2.5m2

- severe crocodiles cracks in and aroundthe peeled off area.

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Severity Levels of Delamination

High Severity- a group of more than 2 moderatedelaminations along a short stretch of road


• thickness of layer peeled off• area of individuall delaminations• number of delaminations

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4. PATCH AND POTHOLES


PATCH

Patch is a repaired section of pavement where a portion of the pavement surfacehas been removed and replaced.Effect: Caused further defects, where it raised or depressed below the level

of the pavement surface

Low Severity- patch is in good condition- has low severity distress


PATCH

Moderate Severity

- patch has moderate severity distress

High Severity- patch has high severity distress

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POTHOLES

Potholes is bowl shaped cavity in the pavement surface, produced when trafficbreaches small pieces of pavement surface and allow water entry.Cause by : the loss of wearing course and binder course materials

the weakening of the base course or poor surfacing quality

Severity levels of Potholes:

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


POTHOLES

- area < 0.3m2 and depth < 25mm

Low Severity

Moderate Severity

- area < 0.3m2 with depth 25 mm to 50 mm

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High Severity- area > 0.1 m2 with depth > 50 mm

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No Possible Cause Probable Treatments1 Loss of surface course patching2 Moisture entry to base course

through a cracked pavement surface

Cut and patch

3 Load associated disintegration of base

Base reconstruction

5. EDGE DEFECTS

Edge Defects occur along the interface of flexible pavement and the shoulder,where the shoulder is unsealed

The Effect of edge defects:

• reduction of pavement width• loss of quality of ride, possible loss of vehicle control• entry of water into base• leading to erosion of shoulder


5. EDGE DEFECTS


EDGE BREAKS

Edge break occur when the edge of the bituminous surface are fretted or broken

No Possible Causes Probable Treatments1 Inadequate pavement width Widen the pavement2 Alignment which encourage

drivers to travel on pavement edge

Pavement widening and realignment

3 Inadequate edge support Shoulder strengthening4 Edge drop-off Strengthening and leveling of

shoulder with road surface5 Loss of adhesion to base Cut and patch


Severity Levels of Edge Break

Low Severity- edge break has just started

Moderate Severity

- edge break with considerable breakup

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Severity Levels of Edge Break

High Severity- significant length of edge break and surfacing loss

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EDGE DROP-OFFS

Edge drop-off is the difference elevation between the traffic lane andoutside shoulderUsually occur when the outside shoulder settles or erodesIt is not a defect if the drop-off is less than 25 mm

No Possible Causes Probable Treatments1 Inadequate pavement width Widen the pavement2 Shoulder material with inadequate

resistance to erosion and abrasion

Replace shoulder material and reconstruct

3 Resurfacing of pavement without resurfacing the shoulder

Leveling the shoulder with road surface


Severity Levels of Edge Drop-Off

Low Severity- slight drop-off

Moderate Severity- significant drop-off

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Severity Levels of Edge Drop-Off

High Severity

- height of drop > 100 mm and it isdanger to traffic

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GUIDE TO THE VISUAL ASSESSMENT OF FLEXIBLE PAVEMENT...

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