Visual Assessment of Flexible Pavement. Surface Condition. Assessment of
Pavement Surface condition is required: •As a measure of the ability of the ...
GUIDE TO THE VISUAL ASSESSMENT OF FLEXIBLE PAVEMENT SURFACE CONDITION By: Norhidayu Hartaty Abdullah Unit Forensik Keselamatan Jalan Bahagian Keselamatan Jalan Cawangan Kejuruteraan Jalan & Geoteknik
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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.Cracks b.Surface Deformations c.Surfaces Defects d.Patches e.Potholes f.Edge Defects Unit Forensik Keselamatan Jalan
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FLEXIBLE PAVEMENT SURFACE CONDITION
CRACKS
SURFACE DEFORMATIONS
SURFACE
Crocodile
Rutting
Bleeding
Edge Break
Block
Depression
Polishing
Edge drop-off
Longitudinal
Corrugation
Ravelling
Transverse
Shoving
Delamination
DEFECTS
PATCH & POTHOLES
EDGE DEFECTS
Edge
Crescent Shaped
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1. PAVEMENT CRACKS
The possible causes of Cracks include: I.Poor construction joints II.Shrinkage III.Reflection of cracks in underlying layers IV.Depression V.Fatigue life of the surface being exceeded VI.Age embrittlement of the surfacing Effects of the Cracks: I.Loss of water-proofing of the pavement layers II.Loss of load spreading ability III.Pumping and loss of fines from the base course IV.Loss of riding quality V.Loss of appearance
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PAVEMENT CRACKS
Types of Pavement Cracks:
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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
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Severity Level of Crocodile Crack
Low Severity • Hairline cracks running parallel to 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
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BLOCK CRACKS also 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 Treatments
1
Joints in underlying layer
Crushed aggregate overlay
2
Shrinkage and fatigue of underlying cemented materials
Replace underlying cemented materials
3
Shrinkage cracks (due to bitumen hardening) in bituminous surfacing
Seal cracks or replace bituminous surface
4
Fatigue cracks in embrittled bituminous wearing course
Cut and patch or crushed aggregate overlay
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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 greater than 3 mm
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Severity Level of Block Cracks
High Severity Severely spalled cracks
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LONGITUDINAL CRACKS also 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 No
Possible Causes
Probable Treatments
1
Reflection of shrinkage cracks
Cut and patch
2
Poorly constructed paving lane in bituminous surfacing
Replace 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 Crushed aggregate overlay base or reconstruction of joints 12
Severity Level of Longitudinal Cracks
Low Severity - Single cracks without any spalling - Mean unsealed carcks width of 3mm or 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
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TRANSVERSE CRACKS
Transverse cracks are unconnected cracks running transversely (perpendicularly to pavement centre line) across the pavement. No
Possible Causes
Probable Treatments
1
Reflection of shrinkage cracks
Cut and patch
2
Construction joint in bituminous surfacing
Crack 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
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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 Unit Forensik Keselamatan Jalan
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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 Treatments
1
Excessive traffic loading at pavement edge
Widen 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
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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
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CRESCENT SHAPED CRACKS or Parabolic, Slippage, Shear Crack
Crescent Shaped Cracks are commonly associated with shoving, often occur in closely spaced parallel group. It is mainly associated with bituminous layer only No
Possible Causes
Treatment Treatments
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
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
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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 and shoving
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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.Rutting II.Corrugation III.Depression IV.Shoving
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2. SURFACE DEFORMATIONS
The major types of Surface Deformation:
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RUTTING also known as Logitudinal Rut
Rutting is longitudinal deformation or depression in the wheel paths which occur 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. 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
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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
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CORRUGATIONS also 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 No
Possible Causes
Probable Treatments
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 29
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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DEPRESSIONS also 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 No
Possible Causes
Probable Treatments
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 subgrade due to environmental influences
Improve sub-soil drainage and reconstruct
4
Settlement due to instability of embankment
Embankment stabilization 32
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 driving over pavement - driver always having to anticipate depression ahead
Measurements to be taken: • 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 No
Possible Causes
Probable Treatments
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 Base reconstruction through the surface
4
Stop and start of vehicles at intersections or roundabout
Mill off and replace with stiffer mix35
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 control because of its presence
Measurements to be taken: • 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. Bleeding II. Ravelling III. Polishing IV. Delamination
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SURFACE DEFECTS
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BLEEDING also 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 binder Effect: cause low texture depth, inadequate tire to stone contact No
Possible Causes
Probable Treatments
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 bitumen already free
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Severity Levels of Bleeding High Severity -Gives the pavement a wet look -Tire marks are evident
Measurements to be taken: • Area affected • Percentage by area of stone immersed
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RAVELLING also known as Fretting
Ravelling is the progressive disintegration of the pavement surface by loss of binder or aggregates or both No
Possible Causes
Probable Treatments
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 construction during wet weather
Thin bituminous overlay
4
Deterioration of binder and/or aggregates
Thin bituminous overlay
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Severity Levels of Raveling Low Severity - Wearing away of the aggregates has not progressed 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 Treatments
1
Inadequate resistance to polishing of aggregates surface
Thin bituminous overlay or use stiffer mix
2
Use of naturally smooth uncrushed Thin bituminous overlay aggregates
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Severity Levels of Polishing Low Severity - smoothening and rounding of upper surface of the roadstone has started
Moderate Severity - coarse aggregates exposed
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Severity Levels of Polishing High Severity - smoothening and rounding of the roadstone has progressed significantly
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DELAMINATION Also 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 Treatments
1
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
Thin bituminous overlay
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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 around the peeled off area.
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Severity Levels of Delamination High Severity - a group of more than 2 moderate delaminations along a short stretch of road
Measurements to be taken: • thickness of layer peeled off • area of individuall delaminations • number of delaminations
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4. PATCH AND POTHOLES
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PATCH Patch is a repaired section of pavement where a portion of the pavement surface has 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
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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 traffic breaches 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
Moderate
25 - 50
Moderate
Moderate
High
> 50
Moderate
High
High
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POTHOLES Low Severity - area < 0.3m2 and depth < 25mm
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
No
Possible Cause
Probable Treatments
1
Loss of surface course
patching
2
Moisture entry to base course through a cracked pavement surface
Cut and patch
3
Load associated disintegration of base
Base reconstruction 57
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
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5. EDGE DEFECTS
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EDGE BREAKS
Edge break occur when the edge of the bituminous surface are fretted or broken No
Possible Causes
Probable Treatments
1
Inadequate pavement width
Widen the pavement
2
Alignment which encourage drivers to travel on pavement edge
Pavement widening and realignment
3
Inadequate edge support
Shoulder strengthening
4
Edge drop-off
Strengthening and leveling of shoulder with road surface
5
Loss of adhesion to base
Cut and patch
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Severity Levels of Edge Break Low Severity - edge break has just started
Moderate Severity - edge break with considerable breakup
61
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 and outside shoulder Usually occur when the outside shoulder settles or erodes It is not a defect if the drop-off is less than 25 mm No Possible Causes
Probable Treatments
1
Inadequate pavement width
Widen the pavement
2
Shoulder material with inadequate Replace shoulder material and resistance to erosion and reconstruct abrasion
3
Resurfacing of pavement without resurfacing the shoulder
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Leveling the shoulder with road surface
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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 is danger to traffic
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