pavement performance and distress

7/29/2019 Pavement Performance and Distress

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PAVEMENT ENGINEERING

(ECG524)

PAVEMENT PERFORMANCE

AND DISTRESS

TOPIC 5.0
http://localhost/var/www/apps/conversion/tmp/TUMPANG%20SAT/ECG524-CHAPTER%204-PAVEMENT%20STRUCTURAL%20DESIGN.ppthttp://localhost/var/www/apps/conversion/tmp/TUMPANG%20SAT/ECG524-CHAPTER%204-PAVEMENT%20STRUCTURAL%20DESIGN.ppt


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5.1 Pavement Distress

5.2 Assessment on Pavement Condition

5.3 Pavement Maintenance5.4 Pavement Repair and Rehabilitations

Topic Outlines


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Synopsis:

Scope covers on types of distresses for both flexibleand rigid pavements, their causes and method ofmeasurements. Serviceability and performancecriteria are discussed.

At the end of the topic, students should be

able to: Identify and explain the various types of pavement

distresses, their causes and simple evaluation.(CO3-PO3)

To measure the serviceability and performancestatus of pavement(CO3-PO4)

Learning Outcomes


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Topic 5.1

Pavement Distress


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Overview

Can be categorized as:

i. Cracksii. Surface Deformations

iii. Surface defects

Pavement Distress


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Topic 5.1.1

Cracks


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Cracks could exist as various patterns of fissures. It may appear aslongitudinal crack, transverse crack, diagonal crack, chicken-wire or fish-net crack, ladder or block crack, crescent crack and etc.

Figure : Different Types of Cracks ( Road Branch of Public Road Department, 1992)

Cracks


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Description:

Series of interconnected cracks causedby fatigue failure of the HMA surface(or stabilized base) under repeated

traffic loading.

Problem:

Indicator of structural failure, cracksallow moisture infiltration, roughness,may further deteriorate to a pothole.

Possible Causes:

Inadequate structural support, Increasein loading & Poor construction.

Type of Cracks

i. Fatigue (Alligator/crocodile) Cracking


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ii. Block Cracking

Description:

Interconnected cracks that divide thepavement up into rectangular pieces.

Problem: Allows moisture infiltration, roughness

Possible Causes:

HMA shrinkage and daily temperature

cycling, Asphalt binder aging & Poorchoice of asphalt binder.

Type of Cracks (cont..)


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iii. Longitudinal Cracking

Description:

Cracks parallel to the pavement'scenterline or laydown

direction. Usually a type of fatiguecracking.

Problem:

Allows moisture infiltration, roughness,indicates possible onset of alligatorcracking and structural failure

Possible Causes:

Poor joint construction

HMA fatigue



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iv. Slippage/Crescent Cracking

Description:

Half-moon shaped cracks generallyhaving two ends pointed into thedirection of traffic.

Problem:

Allows moisture infiltration, roughness

Possible Causes:

Turning wheels cause the pavementsurface to slide and deform.



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v. Joint Reflection Cracking

Description:

Cracks in a flexible overlay of a rigidpavement. The cracks occur directlyover the underlying rigid pavementjoints.

Problem:


Possible Causes: Movement of the PCC slab beneath

the HMA surface because of thermaland moisture changes



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vi. Transverse (Thermal) Cracking

Description:

Cracks perpendicular to the pavement'scenterline or laydowndirection. Usually a type of thermalcracking.

Problem:


Possible Causes:

Shrinkage of the HMA surface due tolow temperatures or asphalt binderhardening

Reflective crack caused by cracksbeneath the surface HMA layer



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Topic 5.1.2

Surface Deformation


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Figure Different Types of Surface DeformationsSource: Road Branch of Public Road Department (1992)

Deformation takes place when a road surface undergoes changes fromits original constructed profile.

May occur after construction due to trafficking or environmentalinfluences.

Surface Deformation


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i. RuttingDescription: Longitudinal depression in the wheel

paths after repeated application ofaxle loading.

Problem:

Ruts filled with water can cause vehiclehydroplaning, can be hazardousbecause ruts tend to pull a vehicletowards the rut path as it is steeredacross the rut.

Possible Causes:

Insufficient compaction of HMA layersduring construction.

Subgrade rutting (e.g., as a result ofinadequate pavement structure)

Improper mix design or manufacture(e.g., excessively high asphalt content,

excessive mineral filler, insufficientamount of angular aggregate particles)

Type of Deformations (cont..)


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ii. Depression

Description:

Localized pavement surface areas withslightly lower elevations than thesurrounding pavement. Depressionsare very noticeable after a rain when

they fill with water.

Problem:

Roughness, depressions filled withsubstantial water can cause vehiclehydroplaning

Possible Causes:

Subgrade settlement resulting frominadequate compaction duringconstruction.



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iii. Corrugation and Shoving

Description:

An abrupt wave or bulging of roadsurface where braking or accelerationmovement occur.

Problem:

Roughness

Possible Causes:

Usually caused by traffic action(starting and stopping) combined with:

An unstable (i.e. low stiffness) HMAlayer (caused by mix contamination,poor mix design, poor HMAmanufacturing, or lack of aeration ofliquid asphalt emulsions)

Excessive moisture in the subgrade



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Topic 5.1.3

Surface Defects


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i. Polished Aggregate

Description:

Areas of HMA pavement where theportion of aggregate extending abovethe asphalt binder is either very smallor there are no rough or angular

aggregate particles.

Problem:

Decreased skid resistance

Possible Causes:

Repeated traffic applications.

Generally, as a pavement ages theprotruding rough, angular particlesbecome polished. This can occurquicker if the aggregate is susceptibleto abrasion

Type of Defects


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ii. PotholesDescription: Small, bowl-shaped depressions in the

pavement surface that penetrate all the waythrough the HMA layer down to the basecourse. They generally have sharp edges and

vertical sides near the top of the hole. Potholesare most likely to occur on roads with thinHMA surfaces (25 to 50 mm (1 to 2 inches))

Problem:

Roughness (serious vehicular damage can resultfrom driving across potholes at higher speeds),moisture infiltration

Possible Causes:

Generally, potholes are the end result ofalligator cracking. As alligator crackingbecomes severe, the interconnected crackscreate small chunks of pavement, which can bedislodged as vehicles drive over them. Theremaining hole after the pavement chunk isdislodged is called a pothole

Type of Defects (cont..)


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iii. Raveling

Description:

The progressive disintegration of anHMA layer from the surface downwardas a result of the dislodgement ofaggregate particles.

Problem: Loose debris on the pavement,

roughness, water collecting in theraveled locations resulting in vehiclehydroplaning, loss of skid resistance.

Possible Causes:Several including: Loss of bond between aggregate

particles and the asphalt binder Inadequate compaction during

construction. High density is requiredto develop sufficient cohesion within

the HMA.

Type of Defects


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iv. Stripping

Description:

The loss of bond between aggregatesand asphalt binder that typically beginsat the bottom of the HMA layer andprogresses upward.

Problem:

Decreased structural support, rutting,shoving/corrugations, raveling, orcracking (alligator and longitudinal)

Possible Causes:

Poor aggregate surface chemistry

Water in the HMA causing moisturedamage

Type of Defects


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v. Bleeding

Description:

The presence of asphalt binder film onthe pavement surface, likely to occur inthe wheel path.

Problem:

Loss of skid resistance when wet

Possible Causes:

Excessive asphalt binder in the HMA(either due to mix design ormanufacturing)

Excessive application of asphalt binderduring BST application (as in the abovefigures)

Low HMA air void content (e.g., notenough room for the asphalt to expandinto during hot weather)

Type of Defects


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Topic 5.2

Assessment on PavementCondition


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Methods For Measuring Roadway Condition

Four (4) characteristics of pavement condition used inevaluating pavement rehabilitation needs;

1) Pavement roughness (ride ability)

2) Pavement distress (surface condition)

3) Skid resistance (safety)

4) Pavement deflection (structural failure)


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1) Pavement Roughness

Refers to irregularities in the pavement surface thataffect the smoothness of a ride.

Roughness is an important pavement characteristic because

it affects not only ride quality but also vehicle delay costs,fuel consumption and maintenance costs

Measurement

Roughness is typically quantified using

- Present Serviceability Rating (PSR)

- International Roughness Index (IRI)


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2) Pavement/surface distress

Refers to the condition of a pavement surface in terms

of its general appearance.

A perfect pavement is level and has a continuous andunbroken surface. In contrast, a distressed pavement may

be fractured, distorted or disintegrated.

Fracture. This could be in the form of cracking (in flexibleand rigid pavements) or spelling resulting from such thingsas excessive loading, fatigue, thermal changes, moisturedamage, slippage or contraction.


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2) Pavement/surface distress (cont...)

Distortion. This is in the form of deformation

(e.g., rutting, corrugation and shoving),which can result from such things as excessive loading,creep, densification, consolidation, swelling, or frost action.

Disintegration. This is in the form of stripping. raveling orspalling , which can result from such things as loss ofbonding, chemical reactivity, traffic abrasion, aggregatedegradation, poor consolidation/compaction or binderaging.


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3) Skid resistance

Skid resistance is the force developed when a tirethat is prevented from rotating slides along the pavementsurface.

Inadequate skid resistance will lead to higher incidences ofskid related accidents.

Skid resistance depends on a pavement surface's microtextureand macrotexture

Microtexture: Refers to the small-scale texture of the

pavement aggregate component (which controls contactbetween the tire rubber and the pavement surface)

Macrotexture: Refers to the large-scale texture of thepavement as a whole due to the aggregate particle arrangement


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4. Pavement Deflection

Pavement surface deflection measurements are theprimary means of evaluating a flexible pavementstructure and rigid pavement load transfer.

Surface deflection is an important pavement evaluation

method because the magnitude and shape of pavementdeflection is a function of;

- Traffic (type and volume),

- Pavement structural section,- Temperature affecting the pavement structure and- Moisture affecting the pavement structure.


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Topic 5.3

Pavement Maintenance


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Overview

Pavement maintenance describes all themethods and techniques used to prolong

pavement life by slowing its deterioration rate.

The performance of a pavement is directly tied to thetiming, type and quality of the maintenance it receives

T

f M i t


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i. Crack Seals

Crack seal products are used to fill individual pavement cracks to prevent entry of wateror other non-compressible substances such as sand, dirt, rocks or weeds.Crack sealant is typically used on early stage longitudinal cracks, transverse cracks, reflectioncracks and block cracks.

In HMA pavements, non sealed or poorly sealed cracks allow moisture anddebris to enter the pavement structure which contributes to asphalt stripping,

secondary cracking, depressed crack edges, spalling, and lipping (elevated crack edges).

In addition the presence of excess water in the pavement base or subgradetends to reduce the compressive and shear strengths of the supporting materialsimmediately below and adjacent to the crack.

As a result, applied traffic loads in the vicinity of the crack create greaterpavement deflections, additional cracking and eventually potholes.

There is a general consensus among states experience that supports sealing cracksas a cost effective rehabilitation or maintenance treatment

Type of Maintenance

The purpose and application of crack sealingto HMA pavement


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Crack sealant

T f M i t (C t )


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ii. Fog Seals

Type of Maintenance (Cont)

A fog seal is a light application of adiluted slow-setting asphaltemulsion to the surface of an aged(oxidized) pavement surface.

Fog seals are low-cost and are used

to restore flexibility to an existingHMA pavement surface.

They may be able to temporarilypostpone the need for a BST ornon-structural overlay

Parking Lot Showing a Fog Seal on the Right Side

T f M i t (C t )


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iii. Slurry Seals


A slurry seal is a mixture ofemulsified asphalt, water, well-graded fine aggregate and mineralfiller that has a creamy fluid-likeappearance when applied.

Slurry seals are used to fill existingpavement surface defects aseither a preparatory treatment forother maintenance treatments or asa wearing course.

T f M i t (C t )


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iv. Bituminous Surface Treatments (BST)


A bituminous surface treatment, also known as a chipseal, is a thin protective wearing surface that is applied toa pavement or base course. BSTs can provide all of thefollowing:

A waterproof layer to protect the underlyingpavement.

Increased skid resistance.

A fill for existing cracks or raveled surfaces.

T p f M int n n (C nt )


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v. Patches


Patches are a common method of treating an area of localized distress.Patches can be either partial or full-depth, although typically HMApavement patches are full-depth.

A high quality HMA patch can be

considered a permanent repairalthough many patches are done asemergency repairs in poor conditions.

Patching material can be just about anyHMA or cold mix asphalt material aswell as certain types of slurries.

Typically some form of HMA is usedfor permanent patches, while cold mixis often used for temporaryemergency repairs.


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Topic 5.4

Pavement Repairand Rehabilitations

O i


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Maintenance can slow the pavement

deterioration, but cannot stop it.

Effects of deterioration need rectifying byadding or replacingmaterial in the existing pavement structure byrehabilitation.

Rehabilitation:A measure to improve, strengthen or salvageexisting deficient pavements to continue service whenpavements exhibit distress in excess of what can be handled

through routine maintenance.

Overview


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Several rehabilitation techniques:

i) Restoration:To restore the surface to suitablecondition and best applied to pavement with distress

limited to the surfacing.

ii) Resurfacing:Involve placement of fresh material on

an existing surfacing.

iii) Recycling:Old pavement that is reclaimed as a

byproduct of pavement rehabilitation and

reconstruction.

iv) Reconstruction:Removal and rebuilding of all part

of the pavement using new materials and

construction specification.

Overview (cont..)

pavement performance and distress

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