An-Najah National UniversityFaculty of Engineering – Civil

Engineering Dept

Advanced Pavement Design - 61562

Dr. Khaled Al-Sahili

Pavement Performance

PAVEMENT FAILURE Functional: it occurs when the pavement,

due to its roughness, is unable to carry out its intended function without causing discomfort to drivers or passengers or imposing high stresses on vehicles

Structural: a collapse of the entire structure or a breakdown of one or more of the pavement components renders the pavement incapable of sustaining the loads imposed on its surface

Causes may be due to inadequate maintenance, excessive loads, climatic and environmental conditions, poor drainage leading to poor subgrade conditions, and disintegration of the component materials.

Excessive loads, excessive repetition of loads, and high tire pressures can cause either structural or functional Failure

Alligator or Fatigue Cracking Block Cracking Joint Reflection Cracking from Concrete Slab Lane Shoulder Drop-off or Heave Longitudinal or Transverse Cracking Pumping or Water Bleeding Rutting Swell Others – Bleeding, Corrugation, Depression, Lane-shoulder

joint separation, patch deterioration, Polished Aggregates, Potholes, Ravelling, Slippage Cracking, etc.

Types of distresses – Flexible Pavement

Types of Distresses – Flexible Pavement

Cracking

1. Alligator Cracking: Series of interconnected cracks, many-sided, sharp-angle pieces (<1 ft. on longest side)

Severity

Possible Causes:• Insufficient bearing support and repeated traffic loading.• Poor base drainage.

Cracking

Block Cracking: Rectangular pieces of asphalt surface ranging in

size from approximately 1 sq. ft. to 100 sq. ft Related to thermal shrinkage of asphalt binder

Joint Reflection Cracking from Concrete Slab

Possible CausesMovement of the rigid pavement slab beneath the HMA surface because of thermal and moisture changes. 

Generally not load initiated, however loading can hasten deterioration

Cracking

Edge Cracking: Crescent-shaped cracks or fairly continuous cracks, parallel to, and usually within I' to 2' of the outer edge of pavement.

Cause: when paved shoulders do not

exist. Severity Levels

Low: Cracks with no breakup or raveling.

Moderate: Cracks with some breakup or raveling.

High: Cracks with considerable breakup or raveling along edge

Cracking

Transverse Cracking: usually appear across the road perpendicular to the centerline.

Possible Causes:• Poor construction joints.• Pavement Shrinkage due to asphalt hardening or freeze/thaw cycles.• Reflective cracking (cracks below the wearing course)

Patching and Potholes Patch Deterioration: Portion of pavement surface that

has been removed and replaced. Poor patching may be uneven, heavily rutted, contain different cracks, etc.

Possible Causes:• Poorly constructed paving, thin layer of patching.• Not sealed along seams, water intrusion defects patch

Patching and Potholes Potholes: Bowl-shaped holes of various sizes in pavement

surface. Potholes are localized failure areas, which may be isolated or caused by a combination of other progressively failing pavement defects (raveling, alligator cracking, patching).

Possible Causes:• Poor quality of materials and/or construction.• Inadequate drainage, Freeze-thaw cycling, Poor patching.

Deformations Deformations in pavements can be divided in

longitudinal and transverse deformations (called unevenness or roughness).

Deformations: Corrugations/Rutting

Longitudinal vertical surface depressions in the wheel path. Possible Causes:

• Poorly constructed roadway.• Substandard or failing sub-bases.• Inadequate lateral support, failing or steep road shoulder.

Deformations: Shoving Longitudinal displacement of a localized

area of the pavement surface caused by traffic pushing against the pavement

Usually occur in asphalt layers that lack stability.

Lack of stability may be caused by a mixture, which is too rich in asphalt, has too high proportion of fine aggregate, or too smooth or too round aggregate

Deformations: Settlement

It is a dip in the longitudinal profile of the pavement surface.

Cause: traffic heavier than design traffic (ESAL) settlement of the lower pavement layers, or by poor construction methods.

Severity LevelsSeverity is based on the effect of the settlement upon vehicle control when traveling along the road.

Disintegration and wear Bleeding is a defect type that can be

recognized as black, “fatty” looking spots on the pavement surface. Causes: high bitumen content or low void content

Disintegration and wear

Raveling is the loss of aggregate from the surface layer. Causes: cohesive failure in the bituminous mortar or adhesive

failure in the interface between aggregate and bituminous mortar

Raveling may occur as a result of poor mixture quality, segregation, or insufficient compacting

Lane Shoulder Drop Off

Edge drop-offs and shoulder scour are often caused by settlement, consolidation, or pumping.

Heave – freeze / thaw process

Water Bleeding and Pumping

Problem: Decreased skid resistance, an indication of high pavement porosity (water bleeding), decreased structural support (pumping)

Possible Causes: • Porous pavement as a

result of inadequate compaction during construction or poor mix design

• High water table• Poor drainage

Swell

Upheaval is a localized upward movement in a pavement due to swelling of the subgrade.

This can be due to expansive soils that swell due to moisture or frost heave (ice under the pavement).

FIX: Full depth patch

Depression

Depression is a localized area of pavement surface that is slightly lower in elevation than the surrounding pavement.

Depressions are most easily identifiable after rain when they fill with water.

Polished Aggregates

Cause: Soft aggregates that polish quickly under traffic

Problem: skidding

Slippage Cracking

Cracks produce a crescent shape. 

Cause: They occur when the top layer of the asphalt shears due to high deflections and a poor bond between the layers.

This type of cracking cannot be treated effectively with crack sealants

Concrete Pavement Blow up Corner Break Faulting or Transverse

Joints and Cracks Joint Load Transfer

System Associate Deterioration

Transverse and Diagonal Cracks

Lane/Shoulder Drop Off or Heave

Longitudinal Cracks Longitudinal Joint

Faulting Pumping or Water

Bleeding Edge Punch out Spalling Swelling Localized Distress Construction Joint

Deterioration Others …

Corner Breaks A corner break extends

through the entire slab. Problem: Roughness,

moisture infiltration, severe corner breaks will fault, spall and disintegrate

Possible Causes: Severe corner stresses caused by load repetitions combined with a loss of support, poor load transfer across the joint, curling stresses and warping stresses.

Faulting Or Transverse Joints and Cracks

A difference in elevation across a joint

Due to pumping

Spalling Problem: Loose debris on

the Pavement, roughness, generally an indicator of advanced joint/crack deterioration

Possible Causes: Excessive stresses at the

joint/crack caused by infiltration of incompressible materials and subsequent expansion (can also cause blowups).

Misalignment or corroded dowel.

Heavy traffic loading.

Pumping

Problem: Decreased structural support of the slab, which can lead to linear cracking, corner breaks and faulting.

Possible Causes: Water accumulation underneath the slab.

Joint Load Transfer System Deterioration

Indicator of a failed load transfer system

Possible Causes: Load transfer dowel bars can fail for two principal reasons: Corrosion. Misalignment.  

Longitudinal Cracking

Possible Causes: Usually a

combination of: traffic loading, thermal gradient

curling, moisture

stresses, and loss of support.

Blow Up

Rigid pavements are prone to slab buckling as a result of excessive expansion in hot weather (Figures 1 and 2)

Edge Punch Out Allows moisture

infiltration leading to erosion of base/subbase support, cracks will spall and disintegrate

Possible Causes: Can indicate a localized 

construction defect such as inadequate consolidation.

It can be caused by steel corrosion, inadequate amount of steel, excessively wide shrinkage cracks or excessively close shrinkage cracks.

Durability (D) Cracking Series of closely

spaced, crescent-shaped cracks near a joint, corner or crack. It is caused by freeze-thaw expansion of the large aggregate within the PCC slab.

Possible Causes ; Freeze-thaw susceptible aggregate.

Swell

Cause: Freeze-Thaw –

swelling soil

Transverse and Diagonal Cracking

Causes: Repetition of

Heavy Load or Stresses due to:

Temperature Gradient

Moisture Gradient

Drying Shrinkage

Serviceability

Serviceability is the ability of a specific section of pavement to serve traffic in its existing conditions.

One method of measurement is Present Serviceability Index (PSI) developed by AASHTO.

PSI is based on roughness and distress conditions (rutting, cracking, and patching).

Another method is to use Roughness Index

PSI

Present Serviceability Individual Present serviceability

rating (0 to 5) Present Serviceability Rating (PSR) Present Serviceability Index (PSI) Performance Index (PI) – summary

of PSI over a period of time

Steps in formulating PSI

Objective Measurements

Mean Slope Variance (SV) Mean Ruth Depth Cracking (linear feet/1000 sq.ft) and

Patching (square feet/1000 sq.ft)

Development of PSI Equation: Flexible Pavement (eq. 9.14) Rigid Pavement (eq. 9.15)

Roughness

It is the longitudinal profile or roughness that provides the major correlation variable for the riding comfort, an indication of PSI.

Measured by: 1. By Rod and Level Rolling straight profilometer

Surface Friction

Skid Number

Non-Destructive Deflection Testing, NDT

Benkelman Beam Test

Dynaflect

Pavement Performance

Expert Systems – professional judgment Heuristic Knowledge is the subjective

or private knowledge possessed by each individual, which is largely characterized by beliefs, opinions, and rules of thumb – knowledge-based systems.

Predictive Models: using equations to predict the allowable number of load repetitions when (fatigue, rutting, or low temperature) cracking occur over a certain area of pavement.

Introduction to Pavement Management

Problems of Highway Rehabilitation: funds are usually insufficient to adequately repair and rehabilitate every roadway section that deteriorates.

The problems is further complicated in that roads may be in poor condition but are still usable, making it easy to defer repair projects until conditions become unacceptable.

Roadway deterioration usually is not the result of poor design and construction practices but is caused by the inevitable wear and tear that occurs over a period of years.

Therefore, Pavement Management becomes necessary to balance between resources and improvement needs

Approaches to Pavement Management

The term pavement management is used to describe the various strategies that can be used to decide on a pavement restoration and rehabilitation policy.

The general topic of pavement management includes design, construction, maintenance, and rehabilitation.

Rehabilitation management is defined as any improvement made to an existing pavement after initial construction, excluding improvements to shoulders or bridges.

Pavement rehabilitation can be both preventive and corrective.

Importance of Pavement Condition Data The first step in the process of pavement management

is to secure data about the condition of each pavement section in the system.

Originally, condition data were obtained by visual inspections that established the type, extent, and severity of pavement condition.

These inspections were subjective and relied heavily on judgment and experience for determining pavement condition and program priorities.

In recent years, visual ratings have been supplemented with standardized testing equipment to measure road roughness, surface condition, pavement deflection, and skid resistance.

Pavement Condition Survey

Pavement condition data are used for the following purposes 1. Establishing Project Priorities 2. Establishing Options: 3. Forecasting Performance

Measuring Roadway Condition

(1) Pavement roughness (rideability) - PSR or PSI(2) Pavement distress (surface condition) (3) Pavement deflection (structural failure) (4) Skid resistance (safety)

Maintenance Requirements and Actions