full depth pavement

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F ULL -DEPTH ASPHALT CONCRETE

PAVEMENT Wong Y.D., Chen M.J.

School of Civil and Environmental EngineeringNanyang Technological University

01.2012

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1. Background

2. Mix type selection

3. Structural design

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1. Background

Outstanding benefits

Long structural life

over5

0 years of service lifeOnly periodic resurfacing is required

Cost-effective

R educe construction time

Eliminate expensive structuralmaintenance during the whole life-cycle

decrease user delay costs for relevantmaintenance activaties

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wearing course

capping layer

intermediate layer

base layer

Structural layers

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w earing course

directly contact with tyre loadings & climate conditions

requirements

R utting resistant

Impermeable

Wear resistant

recommendation

crushed aggregate

polymer modified asphalt

PG rank: one rank higher

OGFC: for special needs insafety

(details in notes)


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intermediate layer

upper pavement layer, subjected to high stress andencounters the problem of rutting

requirements

R utting resistant

Durable

recommendation

crushed aggregate

dense graded mixtures

fine-graded mixtures

(details in notes)


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base layer

the maximum tensile strain appears at the bottom of asphalt layer, i.e. base layer

requirements

Fatigue resistant

Durable

recommendation

coarser mix (economical)

increased thickness

(details in notes)


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capping layer

a layer to protect the base layer, which is exposed to thewet conditions of surrounding soil

requirements

improve drainage of ingressed water

cut off pore pressurefrom drawing up groundwater

recommendation

a layer of sand or gravelpaved between subgrade andbase layer


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Recommended mixture types

Pavementlayer

Mixture typeThickness

(mm)R emark

Wearingcourse

Fine, Dense

20-40Crushed aggregates,

polymer modifiedasphalt

Stone Mastic Asphalt (SMA)

OGFC

Intermediatelayer Fine, Dense 60-100 Crushed aggregates

Base layer Coarse, Dense 75-100Capping

layerSand, gravel 10-20


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Two major distresses:Bottom up fatigue cracking tensile strain at the bottom of

asphalt concrete layerStructural rutting compressive strain at the top of subgrade

Perpetual Pavement Design Concept (David and Kent)


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1 fatigue cracking

Fatigue theory

High Strain = Short LifeLow Strain = Unlimited Life

UnlimitedFatigue

Life

Fatigue Life


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Test Curve


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1 fatigue cracking

Monismith & McLean: Technology of Thick Lift Construction:Structural Design Considerations, 1 97 2 AAPT

Carpenter, Shen & Ghuzlan: A Fatigue Endurance Limit forHigh w ay and Airport Pavements Interstate Route 7 10, 2003Technical Memorandum TM UCK PRC 99 -3

Endurance limit: 7 0 micro(tensile strain at the bottom of asphalt

concrete layer)


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2 Structural rutting

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200 5 TRL (Transport Research Laboratory) Report

Monismith & Long: Overlay Design for Crack and SeatedPortland Cement (PCC) Pavement, 1 999 TRB

Endurance limit: 200 micro(compressive strain at the top of

subgrade)


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Modelling : evaluate the different combinations of layer thickness andmixture type (modulus)

Pavement layer Mixture type ***Modulus Thickness (mm) *Strain t **Strain c

Wearing courseFine, Dense E11

H1=20,30,40

70 micro 200micro

SMA E12

OGFC E13

Intermediatelayer

Fine, Dense E2 H2=60,80,100

Base layer Coarse, Dense E3 H3=75,100

Subgrade E4

* strain t: tensile strain at the bottom of asphalt concrete layer** strain c: compressive strain on top of the subgrade*** E11, E12, E13: modulus values of the material used in the wearing course, with respect to fine-

graded mixture, SMA, OGFC.


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full depth pavement

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