Pavement Design Manual Jan 09[1]

8/9/2019 Pavement Design Manual Jan 09[1]

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PAVEMENT DESIGN MANUAL

Supplement to Part 2: Pavement Structural Designof the Austroads Guide to Pavement Technology

Issued by

Queensland Department of Main Roads

Pavements & Materials Branch

For document content enquiries: Principal Engineer (Pavement Design)

Phone: (07) 3115 3079

Facsimile: (07) 3115 3055


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IMPORTANT INFORMATION

The requirements of this document represent Technical Policy of Main Roads and containTechnical Standards. Compliance with Main Roads Technical Standards is mandatory for all

applications for the design, construction, maintenance and operation of road transportinfrastructure in Queensland by or on behalf of the State of Queensland.

This document will be reviewed from time to time as the need arises and in response toimprovement suggestions by users. Please send your comments and suggestions to the feedbackemail given below.

FEEDBACK

Your feedback is welcomed. Please send to [email protected].

COPYRIGHT State of Queensland (Department of Main Roads) 2009

Copyright protects this publication. Except for the purposes permitted by and subject to theconditions prescribed under the Copyright Act, reproduction by any means (including electronic,mechanical, photocopying, microcopying or otherwise) is prohibited without the prior writtenpermission of the Queensland Department of Main Roads. Enquiries regarding such permissionshould be directed to the Road & Delivery Performance Division, Queensland Department of MainRoads.

DISCLAIMER

This publication has been created for use in the design, construction, maintenance and operationof road transport infrastructure in Queensland by or on behalf of the State of Queensland.

The State of Queensland and the Department of Main Roads give no warranties as to thecompleteness, accuracy or adequacy of the publication or any parts of it and accepts noresponsibility or liability upon any basis whatever for anything contained in or omitted from thepublication or for the consequences of the use or misuse of the publication or any parts of it.

If the publication or any part of it forms part of a written contract between the State of Queenslandand a contractor, this disclaimer applies subject to the express terms of that contract.

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Queensland Department of Main Roads Pavement Design Manual

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Table of Contents

1 INTRODUCTION...............................................................................................................................1

1.1 Foreword..................................................................................................................................11.2 MR Pavement Design System.................................................................................................1

1.3 Scope and applicability ............................................................................................................21.3.1 General......................................................................................................................21.3.2 Applying the MR Pavement Design System..............................................................21.3.3 MR Pavement Design System policy parameters.....................................................3

1.4 Definitions ................................................................................................................................4

2 PAVEMENT DESIGN........................................................................................................................8

2.1 Overview of MR Pavement Design System.............................................................................82.1.1 Design models and mechanical properties................................................................82.1.2 Designers...................................................................................................................82.1.3 Unbound granular design charts ...............................................................................82.1.4 Mechanistic design ....................................................................................................82.1.5 Estimate of life ...........................................................................................................8

2.2 Reliability..................................................................................................................................8

2.3 Selecting a trial pavement configuration and minimum standards ..........................................92.3.1 General......................................................................................................................92.3.2 Project-specific factors.............................................................................................102.3.3 Specifications...........................................................................................................102.3.4 Minimum pavement standards ................................................................................10

2.4 Shoulders ...............................................................................................................................172.4.1 General....................................................................................................................172.4.2 Shoulders with a lower structural standard..............................................................172.4.3 Unsealed shoulders.................................................................................................18

3 CONSTRUCTION AND MAINTENANCE CONSIDERATIONS......................................................20

3.1 General ..................................................................................................................................20

3.2 Unbound granular ..................................................................................................................203.3 Stabilised materials ................................................................................................................203.4 Temporary connections for HILI pavements..........................................................................213.5 Asphalt pavements.................................................................................................................213.6 Working platform....................................................................................................................213.7 Settlement ..............................................................................................................................223.8 Moisture ingress and maintenance........................................................................................22

3.9 Trafficking of incomplete pavement .......................................................................................22

3.10 Thickness of bituminous seals...............................................................................................224 ENVIRONMENT..............................................................................................................................23

4.1 General ..................................................................................................................................234.2 Climatic zones........................................................................................................................234.3 Water environment.................................................................................................................244.4 Minimising exposure to and influence of water ......................................................................27

4.4.1 General....................................................................................................................274.4.2 Design requirements................................................................................................274.4.3 During construction..................................................................................................28

4.5 Situations where pavement or subgrades cannot be protected ............................................28

4.6 Temperature environment......................................................................................................29

5 SUBGRADE ....................................................................................................................................305.1 General ..................................................................................................................................30


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5.2 Subgrade assessment........................................................................................................... 305.2.1 General ................................................................................................................... 305.2.2 Laboratory CBR test conditions.............................................................................. 315.2.3 Statistical analysis of CBR data.............................................................................. 315.2.4 Adoption of presumptive CBR values..................................................................... 315.2.5 Variation in subgrade support with moisture changes............................................ 32

5.3 Subgrade water-induced volume change.............................................................................. 325.3.1 General ................................................................................................................... 325.3.2 Minimising volume change...................................................................................... 335.3.3 Cover over reactive subgrade................................................................................. 33

5.4 Select fill and treated material ............................................................................................... 345.5 Working platform ................................................................................................................... 34

5.5.1 In-service requirements .......................................................................................... 345.5.2 Contractors design requirements........................................................................... 35

5.6 Capping................................................................................................................................. 355.7 Drainage layer ....................................................................................................................... 365.8 Combined subgrade treatments............................................................................................ 36

5.9 Elastic characterisation of subgrade materials...................................................................... 396 PAVEMENT MATERIALS .............................................................................................................. 40

6.1 Unbound granular.................................................................................................................. 406.1.1 General ................................................................................................................... 406.1.2 Determining modulus of unbound granular materials............................................. 40

6.2 Modified granular materials................................................................................................... 41

6.3 Stabilised granular material................................................................................................... 416.3.1 General ................................................................................................................... 416.3.2 Determining design modulus and Poissons ratio................................................... 426.3.3 Cracking.................................................................................................................. 426.3.4 Minimising cracks.................................................................................................... 43

6.4 Lean mix concrete ................................................................................................................. 43

6.5 Asphalt................................................................................................................................... 446.5.1 Asphalt types........................................................................................................... 446.5.2 Determining asphalt modulus and Poissons ratio.................................................. 446.5.3 Recycled asphalt..................................................................................................... 466.5.4 Minimising water infiltration..................................................................................... 46

6.6 Concrete................................................................................................................................ 466.6.1 Base concrete ......................................................................................................... 46

7 DESIGN TRAFFIC.......................................................................................................................... 47

7.1 Average daily ESA in design lane in year of opening ........................................................... 477.2 Selecting design period and assessment period...................................................................477.3 Identifying design lane........................................................................................................... 47

7.4 Initial daily heavy vehicles in the design lane........................................................................ 477.5 Growth rate and cumulative traffic volumes.......................................................................... 487.6 Project specific traffic load distribution.................................................................................. 487.7 Reduced design standard for sealed unbound granular pavements with average daily ESA < 100in design lane in year of opening.................................................................................................... 48

8 DESIGN OF NEW FLEXIBLE PAVEMENTS .................................................................................50

8.1 General.................................................................................................................................. 508.2 Mechanistic procedure .......................................................................................................... 50

8.2.1 Selecting a trial pavement....................................................................................... 508.2.2 Consideration of post-cracking phase in cemented materials ................................ 50

8.3 Empirical design of unbound granular pavements with thin bituminous surfacing ............... 50

8.4 Modified granular pavements................................................................................................ 518.5 Example design charts for mechanistic design..................................................................... 51


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9 DESIGN OF NEW RIGID PAVEMENTS.........................................................................................52

9.1 General ..................................................................................................................................52

9.2 Pavement types .....................................................................................................................529.3 Concrete channels .................................................................................................................529.4 Example design charts for rigid pavements...........................................................................53

10 COMPARISON OF DESIGNS ........................................................................................................5410.1 General ..................................................................................................................................54

10.1.1 Assessment period..................................................................................................5410.1.2 Design inclusions.....................................................................................................5510.1.3 Determining the optimal solution .............................................................................5510.1.4 Selection constraints................................................................................................56

11 TYPICAL CROSS SECTIONS........................................................................................................57

11.1 Typical cross sections............................................................................................................5711.2 Pavement structures..............................................................................................................5811.3 Pavement edge details...........................................................................................................60

12 REFERENCES................................................................................................................................61

APPENDIX 1 .............................................................................................................................................I

APPENDIX 2 ............................................................................................................................................II


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1 INTRODUCTION

1.1 Foreword

The Queensland Department of Main Roads (MR) Pavement Design Manual (this manual) is

written as a supplement to Part 2: Pavement Structural Design of the Austroads Guide toPavement Technology (Austroads, 2008),hereafter referred to as Part 2 of the Austroads guide.The MR Pavement Design Manual, used in conjunction with Part 2 of the Austroads guide and theother components of the MR Pavement Design System, provides requirements for the design ofnew pavements for MR.

Designers are also referred to the following MR documents:

Pavement Surfacings Manual

Pavement Rehabilitation Manual

Road Planning and Design Manual

1.2 MR Pavement Design System

The MR Pavement Design System, which includes this manual, sets out MR specific pavementdesign requirements. For most fundamental design principles Part 2 of the Austroads guide isused. For Main Roads purposes, the MR components of the Pavement Design System takeprecedence over Part 2 of the Austroads guide, if and where they differ.

The MR Pavement Design System includes all the following documents, systems and designproperties:

a) MR documents and systems

i) Pavement Design Manual

ii) standard specifications

iii) supplementary specifications

iv) technical standards

v) standard drawings

vi) standard test methods

vii) technical notes

viii) engineering policies

ix) engineering notes

x) quality requirements

b) Part 2: Pavement Structural Design of the Austroads Guide to Pavement Technology

c) design properties

i) Material design properties must be those stipulated in the MR Pavement DesignSystem described above. In particular, properties such as moduli, fatigue constantsand Poissons ratios must be those stipulated in this manual, or if not stated, thosegiven in Part 2 of the Austroads guide.

ii) The design properties used in the MR Pavement Design System are based on theproducts, components and materials of the pavement conforming to the requirementsof the documents listed in 1.2 a) above.


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1.3 Scope and applicability

1.3.1 General

The MR Pavement Design Manual is intended as a guide for professional, trained, experiencedand knowledgeable pavement designers who are required to:

a) work within the confines of Main Roads organisational policies, guidelines and road networkrequirements

b) be aware of, assess and apply risk management and budgetary constraints to the roadsystem as a whole and its various components

c) take into account local area or project specific issues

d) optimise initial designs and in-service treatments to suit budget and whole-of-life cost issues.

1.3.2 Applying the MR Pavement Design System

The MR Pavement Design System must:

a) be applied as a complete and integrated system. No part can be used in isolation from the

others, nor shall other models, methodologies, specifications, properties and/or materials besubstituted for those required by the MR Pavement Design System.

b) not be used on its own to form part of any contract including, but not limited to, those for thefollowing delivery mechanisms

i) design

ii) design and construct

iii) design-construct-maintain

iv) alliance

v) partnering

vi) build-own-operate-transfer

In such cases, a separate, comprehensive and robust set of project-specific requirementsmust be developed.

c) not be used for performance based contracts and/or with performance basedspecifications. Performance contracts and standards must be based on functionalrequirements guaranteed for the service life of the project.

d) not be used in isolation where functional requirements are specified. Where used by MainRoads as part of an infrastructure delivery model that includes functional requirements,achievement of the functional requirements must be based on requirements for initialconstruction and interventions that involve periodic treatments including overlays, reseals,rejuvenation, re-texturing and so on.

e) not be used for any purpose other than within the context described above. In particular, itmust not be used for

i) designing facilities other than those to be designed directly for Main Roads. It must notbe used for facilities including, but not limited to container and freight yards, miningroads and airports.

ii) designing facilities for any Legal Entity other than the State of Queensland

iii) designing projects with parameters other than those set out in Section 1.2 for theQueensland road network

iv) unsealed pavements; segmental block or flag pavements; roller compacted concretepavements; or any pavement not covered by an MR standard.


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Because of differences between design inputs and whole-of-life realities (e.g. traffic growth,enforcement of and legislative changes to legal axle loads and tyre pressures, variability inconstruction control and ongoing maintenance and rehabilitation) the analytical processes andtools contained herein can provide only an indication of future pavement performance.

If a contract interface involves a planning and/or design component, requirements separate to the

MR Pavement Design System must be developed to address the means of supplying anacceptable design process and design to the owner/client/principal.

1.3.3 MR Pavement Design System policy parameters

The MR Pavement Design System has evolved and been developed to provide solutions that bestserve the needs of the MR controlled road network as a whole and applies only in this context. Thepolicy parameters that provided guidance and the context of developments to date have included:

a) a historic priority for

i) all-weather connections with the consequence of lower initial standards in order tofavour maximum length constructed

ii) an adequate level of service over the whole network within the context of budgetaryconstraints and the comparatively large geographical area with relatively low populationdensity

b) a project delivery system requiring a defined contract between the owner and the contractor,for construction only, based on detailed drawings, specifications and test methods.

Imperatives that have had to be considered in recent times include:

a) high cost of maintenance interventions and associated user disruptions on highly traffickedurban roads, leading to the lowest whole-of-life cost solution for such pavements being highload intensity low intervention (HILI) pavements

b) increasing load intensities caused by increases in vertical loading and major increases in

horizontal shear loading caused by increased truck gross masses. This has required stifferand stronger pavement bases and surface layers.

c) increased expectations about safety requirements, leading to increases in surface propertyrequirements such as macrotexture and microtexture but also requiring stiffer and strongerpavement base layers to support these requirements

d) a greater emphasis on whole-of-life cost rather than initial cost.


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1.4 Definitions

Table 1.4-1 Definitions

Term Description

assessment period The time span over which total costs for the pavement are determined so that whole-of-life cost comparisons can be made between alternative pavement design options.

Refer to Table 7.2-1 for determination of the assessment period.

The assessment period may be the same as the design period, or there may beseveral design periods within the assessment period due to decisions to reconstructor rehabilitate the pavement at intermediate intervals.

Part 2 of theAustroads guide

Part 2: Pavement Structural Design Guide to Pavement Technology(Austroads 2008)

base layer The main structural layer nearest to the surface in a pavement.

binder layer An asphalt layer that is placed between an asphalt base layer and an asphalt surfacelayer. The binder layer is included for its better workability to reduce permeability andimprove roughness levels.

capping layer A layer that provides cover over an in situ material that has a design CBR of less than3.0% but not less than 1.0%.

CBR California bearing ratio

cover over reactivesubgrade

A thickness of material beneath the lowest pavement layer intended to reduce water-induced volume change effects on the pavement where there are in situ materialswith the potential for water-induced volume change.

Cover thickness may include any working platform, select fill, capping layer and/ordrainage layer.

curling Differential movement, usually vertical, in a concrete pavement caused bytemperature differences through the cross-section of the pavement.

constituents Materials and/or components within a product.

deep strengthasphalt pavement

A pavement structure consisting of a minimum total thickness of 175 mm of densegraded asphalt over a cementitiously stabilised subbase (subbase thickness range150200 mm).

design period Main Roads definition (this applies to Main Roads works)

The time span considered appropriate for the major structural elements of the roadpavement to function without rehabilitation and/or reconstruction. Treatments, such asreplacement of surfacing layers and stage construction treatments, that maintain theintegrity of the other components of the pavement are included within the designperiod.

Austroads definition

The time span considered appropriate for the road pavement to function withoutmajor rehabilitation and/or reconstruction.

drainage layer A layer located between the pavement and the untreated subgrade that interceptswater and/or breaks capillary rise.


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Term Description

pavement A pavement that will be used by traffic and designed and constructed in accordancewith the Main Roads Pavement Design System, including this manual.

permanentpavement

Any pavement that is not a temporary pavement.

property Result of a test method that is used to provide useful information about a material orproduct.

reactive subgrade A subgrade material with CBR swell greater than or equal to 0.5%.

rigid pavement A pavement of Portland cement concrete or having a Portland cement concrete basecourse.

safety Qualities of the pavement and associated facilities that directly affect vehicle safetyrelated to but not limited to: surface type, surface texture, skid resistance, surface

drainage, cross-fall, delineation, sight distance, guide posts, lighting and guardrail.

settlement A lowering of the height of the pavement and subgrade as a result of loading imposedby traffic, the pavement and/or the embankment, and caused by creep, shear orreduction in volume.

stabilised subgrade A subgrade that has been stabilised with chemical binders and site investigationand laboratory testing has verified that the intended long-term properties of thestabilised material will be achieved. The structural contribution of the layer may beconsidered in the same manner as an un-stabilised select fill with a material CBRdetermined by a CBR test, but not greater than 20% and subject to the maximummodulus that can be developed when sub-layered as an unbound material.

staged construction Treatments to the pavement during its design period by programmed strengtheningthat occur in a way that maintains the structural capacity of the original pavementlayers for the design period (eg. overlays).

subbase layer The layer beneath the base layer

subgrade level The level of the interface between the bottom of the pavement and the top of theSubgrade.

subgrade material Subgrade material includes working platform, select fill, treated material, drainagelayer, capping, general fill and Untreated Subgrade to a minimum depth of 1.5 mbelow the bottom of the pavement.

surface layer The layer in immediate contact with traffic.

temporary pavement Any pavement constructed for the purpose of carrying traffic for short periods(maximum 2 years) while the pavement for the road is under construction,reconstruction and/or rehabilitation, designed in accordance with the Main RoadsPavement Design System and the requirements for temporary pavements in thismanual. The design, material and construction requirements for temporarypavements are the same as for permanent pavements, unless specifically statedotherwise.

test method Unless otherwise noted a test method as specified in the relevant Main Roadsspecification, technical standard, or supplementary specification.


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Term Description

treated material Material treated with lime and/or cement in accordance with the relevant Main Roadsspecification, technical standard, or supplementary specification.

UCS Unconfined compressive strength.

unbound granularpavement material

A material complying with the relevant Main Roads specification, technical standard, orsupplementary specification that consists of graded aggregates and may include clay.

unbound granular -acceptableenvironment

An unbound granular acceptable environment generally includes, in addition to thespecification requirements:

a) Full width seal (an alternative for low traffic volumes is a low permeability select fillunsealed shoulder where whole-oflife costing confirms it is economical for theparticular situation);

b) Adequately designed, constructed and maintained surface and subsurfacedrainage;

c) Open table drains in cuttings;

d) No standing and / or ponded water within 5 m laterally of the trafficked lane(s);

e) No water within 2 m vertically unless there is a full width drainage / capillary breaklayer;

f) Degree of saturation limits achieved and maintained for all layers;

h) All layers are tested with a 4 day soaked CBR (except that an unsoaked CBR canbe used for subbase in low pavement water content environements);

i) Pavement is not subject to water inundation or flooding that lasts for more than 1day (protection such as fully enclosed low permeability verges, drainage / capillarybreak layer, full width seal and pavement drains may be required).

untreated subgrade Natural unprocessed material, other than that moved from another location and/or

compacted at the location, where the characteristics of the subgrade are to bedetermined to assess:

a) the need for one or more of the following elements: capping layer; cover overreactive subgrade; drainage layer and/or combined capping/drainage layer

b) subgrade design CBR and swell.

warping Differential movement, usually vertical, in a concrete pavement caused by watercontent differences through the cross-section of the pavement.

water-inducedvolume change

Change in the volume of the subgrade material resulting from a change in watercontent usually on a reactive subgrade material.

weighted plasticityindex (WPI) The product of the plasticity index and percentage passing the AS 0.425 mm sieve

working platform A layer that is part of the subgrade and which provides:

access for construction traffic

a platform on which to construct the pavement layers

protection to the underlying materials.


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2 PAVEMENT DESIGN

2.1 Overview of MR Pavement Design System

2.1.1 Design models and mechanical properties

Pavement design comprises empirical and mechanistic components.

The MR Pavement Design System utilises mathematical models to provide a logical frameworkwithin which to apply existing knowledge to the structural design of pavements. The models utilisemechanical properties such as modulus and Poissons Ratio. However, the direct measurement ofthese mechanical properties and the mechanistic model are not as robust as in other disciplines.Direct measurements must:

a) be statistically analysed to account for the considerable variation in pavement materials

b) have a 95% confidence level applied, unless stated otherwise

c) be considered as information additional to and integrated with values interpolated and/orextrapolated from the total calibration of the model

d) be used only in the context of the overall design system.

Where provided, the values given in the MR Pavement Design Manualmust be used.

2.1.2 Designers

Adequate design is possible only when carried out by professional, trained, experienced, andknowledgeable personnel. It requires consideration and integration of all inputs including localconditions, material characteristics, cross-sections, loading, design models, road user safety andconstructability.

2.1.3 Unbound granular design charts

The unbound granular design chart considers only rutting and shape loss.

2.1.4 Mechanistic design

Mechanistic pavement design, utilising layered linear elastic theory, considers only three distress types:rutting and shape loss, fatigue of asphalt, and fatigue of cement stabilised materials.

For concrete pavements designed utilising this Manual, the design method for base thicknessconsiders two distress types: fatigue of the base and erosion of the subbase/subgrade.

Other types of distress, such as those caused by horizontal stresses on grades, at intersectionsand on curves, or by environmental influences such as temperature and water, are not directlyassessed by these design methods. These forms of distress have to be constrained by othermeans such as specification of appropriate materials or provision of relevant cross-sections,

pavement types and drainage. Consequently, this Manual cannot be used in isolation and must beused in conjunction with all other components of the MR Pavement Design System.

2.1.5 Estimate of life

The MR Pavement Design System will provide an estimate of the life of various pavementelements. To maintain the functionality of the pavement, including for the initial design period,interventions are required to replace, overlay and/or rejuvenate elements of the pavement. Regularpavement monitoring, with input from designs in accordance with this Manual, is essential todetermine when these interventions are to occur.

2.2 Reliability

The Austroads reliability guidelines (Part 2 of the Austroads guide, Section 2.2.1.2) consider onlythe following structural distress modes:


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a) for pavements designed with layered linear elastic theory

i) fatigue of asphalt

ii) fatigue of cemented materials

iii) rutting and shape loss of unbound granular materials and subgrade

b) for concrete pavements designed with Westergaard and finite element theory

i) fatigue of concrete base

ii) erosion of subbase/subgrade.

These reliability guidelines were based on general assessments of network performance. As theunderlying causes of performance vary widely over the network, these probabilities can not beused for determining the reliability of a specific project or in the contract interface for a specificproject.

The reliability guidelines are not appropriate for assessing reliability for other distress modesincluding, but not limited to, stripping or rutting of asphalt, roughness, skid resistance, and distresscaused by environmental factors.

The choice of reliability is influenced by the classification/function of the road, its location andintended usage both prior to and after the completion of the design period. It is to be defined inaccordance with Main Roads policy. Judgement of the appropriateness of the reliability level has tobe based on the overall network performance of similar designs under similar conditions.

The minimum reliability levels to be used in the design of MR projects are given in Table 2.2-1.These reliability levels are to be used for the design of both temporary and permanent pavements.

Table 2.2-1 Minimum reliability levels

Road category Reliability (%)

All roads, or sections of road, where intervention costs are very high or traffic

management is very difficult1

97.5

Motorways, highways and main roads with lane AADT > 2000 97.5

Highways and main roads with lane AADT > 500 and 2000 95

Minor roads with lane AADT 500 90

Note:

1) Examples include high traffic volume metropolitan highways and arterials roads, mountainous sections, flood-ways,intersections and approaches to structures such as bridges.

2.3 Selecting a trial pavement configuration and minimum standards

2.3.1 General

Appropriate pavement configurations vary markedly with the function of the road, traffic loading,availability of materials and environment.

Pavement types and standards given in Table 2.3-1 to Table 2.3-5 are based on straightalignments with flat grades. The minimum layer thicknesses given are absolute minimums and theactual adopted layer thicknesses must be designed for fatigue and deformation requirements.Temporary pavement types are for temporary use while the permanent pavement is constructed,maintained, overlaid or re-constructed.

Where a permanent pavement is temporarily trafficked during construction, the damage resultingfrom the temporary trafficking must be included in the design calculations for the permanentpavement.


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2.3.2 Project-specific factors

There are a number of project-specific factors that could not be taken into account in thedevelopment of the pavement type selection tables. Consequently, there will be occasions whenthe pavement type and/or pavement details will need to be changed from those given in the tables.Project-specific factors that may influence pavement selection include, but are not limited to:

a) horizontal shear stresses on grades, curves and intersections

b) pavement contact stresses higher than those used in the development of the currentpavement design models and specifications

c) availability of materials

d) availability and adequacy of construction equipment, materials and expertise

e) construction constraints (e.g. construction under traffic)

f) changes to the function/classification of the road during the design period

g) changes to the road network during the design period

h) specific functional requirements (e.g. safety, noise)i) current and future traffic characteristics

j) settlement and/or water-induced volume change. Where settlement and/or water-inducedvolume change is likely and cannot be reduced to an acceptable level, stiff pavements, suchas concrete, stabilised or modified, must not be used.

k) whole-of-life costs. Whole-of-life costs must include direct and indirect costs of interventionssuch as raising drainage structures, increasing clearances, raising safety barriers, providingtemporary access, maintaining alternative routes, delays and disruptions to road users, etc.

l) current and future budget considerations.

m) local environmental conditions, including

i) unbound granular pavements

ii) concrete pavements

Concrete pavements must have their complete cross-section (thickness and width)completed within a month to minimise differential and potentially detrimentalmovement.

iii) asphalt pavements

Asphalt pavements must be kept as dry as possible as water is a contributor tostripping.

2.3.3 SpecificationsMain Roads specifications or technical standards shall be used.

2.3.4 Minimum pavement standards

Minimum pavement standards are given in Table 2.3-1 to Table 2.3-5, with primary selection basedon traffic loading in terms of the average daily ESA in the design lane in the year of opening.

When selecting a pavement standard from these tables for a particular traffic level, a standard for ahigher traffic category may be used. A standard for a lower traffic category may not be used.

There may be other factors that affect the choice of the pavement structure. Examples includethose described below:

1) asphalt over granular pavements


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For asphalt over granular pavements, the lowest whole-of-life cost usually occurs when theasphalt thickness is sufficient to enable the asphalt to achieve a fatigue life at least the sameas a reasonable pavement design life and the subgrade rutting life provided by the coverover subgrade.

While relatively thin1 asphalt surfaced granular pavements usually do not provide the lowest

long-term whole-of-life solution, other factors may have a significant effect on selection of thepavement type, such as

a) budget constraints for initial construction

b) the cost-effectiveness of constructing relatively short sections

c) the high cost of appropriate granular base materials

d) noise.

In addition, in areas with surfaces subject to significant horizontal shear (such as grades, curvesand intersections), the minimum thickness and type of asphalt should be determined so that italso accommodates this horizontal shear. In such cases the minimum thickness should be 100mm. Thicker and/or polymer modified asphalt should be used for more severe applications.Models for determining the required thicknesses to resist shear forces are not currently availableand local performance history is to be applied.

2) modified granular pavements

Modified granular pavements are not listed in Table 2.3-1 to Table 2.3-5. Where theirperformance has been established locally, they are to be specified and constructed inaccordance with local District requirements, but within the following requirements:

a) The pavement must comprise a full depth modified material.

b) The design modulus for the base must be determined from repeat load triaxial testingand in situ deflection analysis of a similar existing pavement. When in situ analysis is

not available, the maximum design modulus for the base shall be 350 MPa. Theabsolute maximum design modulus of the base shall be 600 MPa.

c) In all cases there must be a working platform and, where there is a reactive subgrade,cover over reactive subgrade.

d) The pavement must have at least a two-coat bitumen seal.

e) The potential for and risk associated with cracking must be recognized and acceptedand appropriate interventions allowed for in the whole-of-life costing and maintenanceduring service;

f) Modified granular pavements cannot be used where the average daily ESA in thedesign lane in the year of opening is > 1000 or only a HILI pavement type is given in

Table 2.3-1.Typical pavement cross-sections for various pavement categories are given in Chapter 11.

1

Relatively thin asphalt surfaced granular pavements are those where the fatigue life of the asphalt cannotachieve a reasonable design life for the pavement. In these cases, the asphalt has to be regularly replaced,rejuvenated and/or overlaid.


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Table 2.3-1 Pavement type: application

Average daily ESA in design lane in year of opening1

Type

L

ocation

< 10 10 to < 100 100 to < 1000 1000 to < 3000 3000

Rural

SG(D)2,3

AG(C)3

SG(C)2,3

AG(C)2,3

SG(B)2,3

AG(A-C)3

ASt(A)

HILI

SG(A)2,3

HILI

Permanent

pavement

Urban

SG(D)2,3

AG(C)3

SG(C)2,3

AG(C)2,3

SG(B)2,3

AG(A-C)3

ASt(A)

HILI HILI

Te

mporary

pa

vement

Ruraland

urban

SG(D)2,3

AG(C)3

SG(C)2,3

AG(C)3

SG(B)2,3

AG(A-C)3

ASt(B)

AG(A)

ASt(B)

AG(A)

Abbreviations

HILI High Load Intensity, Low Intervention pavement as defined in Table 2.3-2.

AG(A)

AG(B)

AG(C)

AG(A-C)

Asphalt over granular pavement as defined in Table 2.3-3.

AG(A-C) can be any standard that suits the circumstances, including budget and whole-of-life costing.

SG(A)

SG(B)

SG(C)SG(D)

Spray sealed granular pavement as defined in Table 2.3-4.

ASt(A)

ASt(B)

Asphalt over cement stabilised (Cat 1 or Cat 2) pavement as defined in Table 2.3-5.

Notes:

1) The average daily ESA in the design lane in the year of opening used in this table and elsewhere in this manual are basedon a heavy vehicle growth rate not exceeding 10.0% per annum. If the heavy vehicle growth rate exceeds 10.0% perannum in any of the first five years after opening, then the average daily ESA in the design lane for the first five years afteropening shall be used instead.

2) Asphalt over granular pavement or HILI pavement instead of spray sealed granular pavement is required in areas with highhorizontal shear stresses such as intersections, grades and curves.

3) Pavements incorporating unbound granular material must not be used where there is an in-service exposure of the

unbound material to water to the extent that the water content of the granular material is likely to rise above the specifiedmaximum degree of saturation.


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Table 2.3-2 Pavement type details: high load intensity low intervention (HILI)

Type Surface1,2

Binder Base Subbase Subgrade

Jointed plain(unreinforced)concrete

(asphalt surface notrecommended)

Jointed plain

(unreinforced)concrete

Jointedreinforcedconcretepavement

(asphalt surface notrecommended)

Jointed

reinforcedconcrete

OG10 (min 30 mm);or

OG14 (min 40 mm)

(if required)

DG14HS3

(if required)

Continuouslyreinforcedconcretepavement

DG14HS3

(if required)

Continuouslyreinforcedconcrete

Lean mixconcrete

(150 mm)

OG10 (min 30 mm):or

OG14 (min 40 mm)

Full depthasphalt

DG14HS3

OG10 (min 30 mm);or

OG14 (min 40 mm)

Deep strengthasphalt

DG14HS3

Cat 16

orCat 2

stabilisedgranular

7

(150 to200 mm)

OG10 (min 30 mm);or

OG14 (min 40 mm)

Flexiblecomposite

DG14HS3

DG14HS3

DG20HM4,5

Lean mixconcrete

8

(175 to250 mm)

ReferSection3.6

andChapter5

Notes:

1) Surface must comply with the Main Roads pavement surface property standards given in the MR Pavement SurfacingsManual. Asphalt over jointed plain concrete or jointed reinforced concrete not recommended because of reflectivecracking. Asphalt over continuously reinforced concrete used if required (usually to reduce noise). Special prime overconcrete required for any asphalt surface.

2) All surface asphalt must have an underlying S4.5S polymer modified seal (refer Section 3.5).

3) The minimum thickness of DG14HS for both surface and binder layers is 50 mm, except where the base layer is concretein which case the minimum thickness is 45 mm (surface layer) and 40 mm (binder layer).

4) The DG20HM base layer may be replaced with a different mix (DG14HS, DG14(320), DG20(320) or DG20(600)), subjectto the total thickness of binder layer plus surface layer being at least 100 mm where the base layer is not DG20HM orDG14HS. DG28 cannot be used in HILI pavements.

5) The minimum thickness of the base layer in deep strength asphalt and flexible composite pavements must be such thatthe total thickness of dense graded asphalt (base plus binder plus surface) is a minimum of 175 mm.

6) At this time, these material types are only available for project specific work with the MR project specific supplementaryspecification for unbound granular materials. Contact Pavements & Materials branch for advice on their use.

7) A prime plus a SAMI (incorporating S4.5S polymer modified binder) must be included above the stabilised granularsubbase.

8) A 10 mm Class 170 bitumen seal protection layer must be included above the lean mix concrete.


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Table 2.3-3 Pavement type details: asphalt over granular

Standard1

Surface2,3


SB18

(min 125 mm)DG144

(min 50 mm) SB29

(min 125 mm)

SB18

(min 125 mm)DG204

(min 50 mm) SB29

(min 125 mm)

SB18

(min 125 mm)

OG10 (min 30 mm)

or

OG14 (min 40 mm)

DG14

(min 50 mm)

DG284

(min 70 mm) SB29

(min 125 mm)

SB18

(min 125 mm)DG144

(min 50 mm) SB29

(min 125 mm)

SB18

(min 125 mm)DG204

(min 50 mm) SB29

(min 125 mm)

SB18 (min 125 mm)

AG(A)5

DG14 (min 50 mm)

DG284

(min 70 mm) SB29

(min 125 mm)

B18

(min 150 mm)OG10 (min 30 mm)

or

OG14 (min 40 mm)

DG14(min 40 mm) B2

9(min 150 mm)

B18

(min 150 mm)

AG(B)6

DG14 (min 45 mm) B2

9(min 150 mm)

SB29

(min 125 mm)

B28

(min 125 mm)DG10 (min 35 mm)

B39

(min 125 mm)

B28

(min 125 mm)AG(C)7

DG14 (min 45 mm)

B39

(min 125 mm)

SB49 (min 100 mm)

ReferSection3.6

andChapter5

Notes:

1) Thin asphalt-surfaced granular options may have a low asphalt fatigue life, which decreases significantly with increasing loadintensities. Frequently, where an asphalt surface is required for the whole project, a HILI pavement or a sealed granularpavement, as relevant, provides the lowest whole-of-life cost. However, an asphalt over granular pavement may be theappropriate choice where other factors dominate, such as when there is a restricted initial budget, short sections are to beconstructed (e.g. for high stress areas) or there is an absence of suitable materials for the HILI or sealed granular options. Allasphalt over granular pavements must only be constructed in an Unbound Granular Acceptable Environment.

2) Surface must comply with the Main Roads pavement surface property standards in the MR Pavement Surfacings Manual.

3) All surface asphalt must have an underlying seal (refer Section 3.5). Where the layer below the asphalt surface is also asphalt,the seal must comprise S4.5S polymer modified binder. Where the layer below the asphalt surface is unbound granular

material, the unbound material must first be primed and the seal must comprise Class 170 bitumen and minimum 10 mm sizecover aggregate.

4) DG14, DG20 or DG28 mix shall be selected to suit the situation.

5) The unbound subbase must be primed and sealed with a minimum 10 mm nominal size Class 170 bitumen seal. For asphaltover granular temporary pavements, where the average daily ESA in the design lane in the year of opening exceeds 1000,A5S binder shall be used in the surface and binder asphalt layers. The unbound subbase can be replaced with a workingplatform, in which case the pavement is called a full depth asphalt pavement. An unbound subbase shall not be used over aworking platform.

6) The unbound base must be primed and sealed with a minimum 10 mm nominal size Class 170 bitumen seal.

7) The unbound base must be primed and sealed with a minimum 10 mm nominal size Class 170 bitumen seal.


9) A new MR specification for unbound granular pavement types is being developed. Until the new specification is issued, thecurrent standard specification types that can be used are given in Table 2.3-6.


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January 2009 15

Table 2.3-4 Pavement type details: sprayed seal granular

Minimum material quality4

StandardProject

location1, 2

Surface

3Base

Upper

subbase

Lower

subbase

Subgrade

SG(A) AE sprayed seal B15

SB15

LSB15

SG(B) AE sprayed seal B2 SB2 LSB2

SG(C) AE sprayed seal B3 SB3 LSB3

AE sprayed seal B4 SB4 LSB4

SG(D) Low pavementwater-content

sprayed seal B5 SB5 LSB5

ReferSection3.6 and

Chapter 5

Notes:

1) AE: Unbound Granular Acceptable Environment (refer definitions).

2) In low pavement water-content environments the subbase layers can be assessed with an unsoaked CBR.

3) Surface must comply with the Main Roads pavement surface property standards given in the MR Pavement SurfacingsManual.

4) A new MR specification for unbound granular pavement types is being developed. Until the new specification is issued, thecurrent standard specification types that can be used are given in Table 2.3-6.



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Table 2.3-5 Pavement type details: asphalt over stabilised granular

Standard Surface1,2


DG145

Cat 16

or Cat 2stabilised granular

7

(150 to 200 mm)

DG205

Cat 16


7

(150 to 200 mm)

OG10(min 30 mm)

or

OG14(min 40 mm)

DG14

(min 45 mm)

DG285

Cat 16


7

(150 to 200 mm)

DG145

Cat 16


7

(150 to 200 mm)

DG205

Cat 16


7

(150 to 200 mm)

ASt(A)3

DG14(min 45 mm)

DG285

Cat 16

or Cat 2

stabilised granular

7

(150 to 200 mm)

OG10(min 30 mm)

or

OG14(min 40 mm)

DG14(min 50 mm)

Cat 16


8

(min 150 mm)

ASt(B)4

DG14(min 50 mm)

Cat 1

5or Cat 2

stabilised granular8

(min 150 mm)

ReferSection3.6andChapte

r5

Notes:

1) Surface must comply with the Main Roads pavement surface property standards given in the MR Pavement SurfacingsManual.

2) All surface asphalt must have an underlying S4.5S polymer modified seal (refer Section 3.5)

3) The minimum thickness of the base layer in ASt(A) pavements must be such that the total thickness of dense gradedasphalt (base plus binder plus surface) is a minimum of 175 mm.

4) Standard ASt(B) is only suitable for use as temporary pavement and not permanent pavement. Where the average dailyESA in the design lane in the year of opening exceeds 1000, A5S binder shall be used in the surface and binder asphaltlayers.

5) DG14, DG20 or DG28 mix shall be selected to suit the situation.


7) A prime plus a SAMI (incorporating S4.5S polymer modified binder) must be included above the stabilised granularsubbase.

8) A prime and seal (minimum 14 mm nominal size with C170 bitumen) must be included above the stabilised granular base.


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January 2009 17

Table 2.3-6 Current Main Roads standard granular types to be used

Current MRS11.05 materials to be used2

New unboundgranular types Any environment

(unrestricted)Low pavement water-content

environment only (low moisture)

Base materials

B1 Note 1

B2 1.1, 2.1

B3 1.1, 2.1

B4 1.1, 2.1 3.1

B5 2.2 3.2, 4.2

Subbase materials

SB1 Note 1

SB2 1.2, 2.3

SB3 2.3

SB4 2.3 3.3

SB5 2.4 3.4, 4.4

Lower subbase materials

LSB1 Note 1

LSB2 2.5

LSB3 2.5

LSB4 2.5 3.5

LSB5 2.5 3.5, 4.5

Notes:

1) At this time, material types B1, SB1 and LSB1 are only available for project specific work with the MR project specificsupplementary specification for unbound granular materials. Contact Pavements & Materials branch for advice ontheir use.

2) A new MR specification for unbound granular pavement types is being developed. Until the new specification isissued, the current standard specification types that can be used are given in this table.

2.4 Shoulders

2.4.1 General

There are two broad design alternatives for shoulders. The preferred design alternative is tocontinue all layers of the structural pavement for the full width of all trafficked lanes and shoulders.This alternative is generally more practical to construct with a lower risk of construction variabilityand/or moisture ingress.

The second, less preferred alternative is to design and construct the shoulder to a lower structuralstandard than the trafficked lanes. Further details on this option are given in Section 2.4.2.

In both cases, the structural section of the pavement (the section beneath the trafficked lanes)must extend at least 200 mm beyond the delineated edge of the trafficked lanes for HILIpavements, and at least 100 mm for other pavements.

2.4.2 Shoulders with a lower structural standard

Where a shoulder of a structural standard lower than that of the trafficked lanes of the pavement isprovided, the following must be adopted:


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a) Total pavement thickness of the shoulder shall be the same as the adjacent through lane.

b) Where the adjacent structural section of the pavement is full depth asphalt, deep strengthasphalt or flexible composite, thick asphalt over granular or thick asphalt over stabilisedpavement, the shoulder shall have the same asphalt surface, seal and binder courses as thestructural section. Beneath this, the required thickness of asphalt base, or alternatively, a

Type B1 or B2 unbound granular base with a polymer-modified seal, shall be designed toensure that the asphalt does not fatigue. The balance of material down to the top of theworking platform shall be at least a Type SB2 material. A pavement drain shall be providedat the interface of the two pavements.

c) Where the adjacent structural section of the pavement is asphalt surfaced granular or sealedgranular pavement, the shoulder shall have the same asphalt surface course(s) and/or sealas the structural section. The shoulder shall also have the same granular base layer(s) andmaterials as the structural section. Other layers required to make up the design thickness forthe shoulder are to be the same thickness and material type as used in the adjacent layers inthe structural pavement. The balance of the thickness of the shoulder to the level of thelowest pavement layer is to be a select fill material. It must not be a general fill material.

d) Where the adjacent structural section of the pavement is concrete, the shoulder shall havethe same asphalt surface, seal and binder courses (where they exist) as the structuralsection. The minimum total thickness of DG14HS shall be 100 mm. Beneath this, therequired thickness of asphalt base, or alternatively, a Type B1 or B2 unbound granular basewith a polymer-modified seal, shall be designed to ensure that the asphalt does not fatigue.The balance of material down to the top of the working platform shall be at least a Type SB2material. A concrete edge drain shall be provided at the interface of the two pavements.

e) In all cases sealing is to continue to the outside edge of any verge or outside edge of theshoulder if a verge does not exist.

f) A lower standard shoulder is not permitted on the high side of one-way crossfalls as thiscould result in moisture entering the pavement.

Where a lower structural standard shoulder is constructed as a widening to an existing pavement,the effect of disturbing in situ subgrade materials should be considered in determining thethickness of the shoulder.

There are some limitations to the use of lower structural standard shoulders that need to beaddressed when they are being considered for a particular project. These include the following:

Construction may be more difficult because of increased complexity and narrow workingwidths.

Future widening may be more difficult.

With concrete pavements, a thicker base layer is required.

Temporary trafficking of the shoulder during construction and future maintenance of thethrough lanes may be restricted by the lower structural capacity of the shoulder.

Some shoulders may experience regular trafficking because of the nature of the roadalignment (e.g. curves, end of tapers, narrow through lanes, access points, intersectionsand/or no edge lines).

2.4.3 Unsealed shoulders

Where an unsealed shoulder is to be considered, the following requirements apply:

a) It cannot be used on any pavement with average daily ESA > 1000 in the design lane in theyear of opening.

b) The seal must extend at least 200 mm beyond the delineated edge of the trafficked lane.


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January 2009 19

c) The material in the shoulder must provide low permeability (max. 5 x 10-9 m/sec), low swell(max 1.5% at maximum dry density (MDD) and optimum moisture content (OMC) after tendays soaking) as well as sufficient strength to support traffic (minimum soaked CBR 40).

Because of the additional cost of the above shoulder material and the additional risk of loss ofservice life or failure caused by the infiltration of water, whole-of-life costing must be carefully

assessed when unsealed shoulders are being considered.


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3 CONSTRUCTION AND MAINTENANCE CONSIDERATIONS

3.1 General

The design procedures in this manual assume that construction and maintenance are carried out

to the appropriate Main Roads standards. Unless such standards are met, the moduli, thicknessesand/or other critical properties assumed in the design model may not be achieved and reducedpavement performance could be expected.

3.2 Unbound granular

Unbound granular pavements are particularly susceptible to damage caused by the infiltration ofwater resulting from: rain, water ponding and/or flooding during construction; water ponding and/orflooding during service; and lack of an adequate seal and/or drainage maintenance in service.Therefore:

Projects including unbound granular material should be programmed such that constructionof the pavement occurs at the time of year with the lowest likelihood of rain.

Weather forecasts must be regularly reviewed and pavements not constructed when rain islikely and existing construction protected from the infiltration of water.

Contract provisions must allow for delays to construction caused by wet weather.

Unbound granular pavements must not be used where:

the pavement layer(s) cannot be constructed and maintained at less than their degree-of-saturation limits

the subgrade cannot be constructed and maintained at the design modulus.

Contracts including the construction of unbound granular pavements must:

a) have allowances for work ceasing during periods of wet weatherb) establish clear responsibility and liability for infiltration of water during construction from

sources including rain, surface and ground water flow, inundation/flooding, and transfer fromnew material with a high water content.

Unbound granular pavements in cuttings must have open table drains (see Figure 11.3-3).

During construction, rain gauges must be installed at least every 500 m along the job site. Rainevents must be recorded daily to help determine the possible exposure of the pavement to waterinfiltration.

Where water does infiltrate granular material, destructive testing is required to assess the extentand change to water content and degree of saturation, and hence determine what action is

required. Expensive re-work may be necessary to ensure the materials are brought within thespecified limits before overlying materials are placed.

3.3 Stabilised materials

Achieving the specified compaction standard in stabilised materials is essential for thedevelopment of the stiffness and fatigue characteristics assumed in design, particularly for thelower layers where maximum tensile stresses occur. To achieve the compaction standard, themaximum compacted thickness of a single layer is to be 200 mm.

Multi-layer construction should be avoided wherever possible as layers will eventually delaminate.

Multi-layer construction requires the provision of shear resistance (i.e. bonding) between layers to

contribute to them acting together structurally.Methods used to establish this for materials with a cementitious additive include:


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January 2009 21

a) application of a cement slurry (water/cement ratio 0.6 to 0.7), at a rate equivalent to 2 kg ofcement per square metre immediately before laying subsequent layers

b) placement of a prime and a seal with a large cover aggregate (> 14 mm) on top of the lowerlayer.

Where multi-layer construction is used:

a) The second and subsequent layers must not be stabilised with in situ stabilisation methods,even if the first layer is stabilised in situ.

b) The first layer should be constructed to be as thick as possible (compacted thickness of atleast 150 mm but not greater than 200 mm) to avoid damage to the lower layer when placingsubsequent layers. Where it is not possible to place a thick first layer, consideration shouldbe given to retarding the first layer and placing the second layer before the first layer has set.

Multi-layer construction shall not be used for HILI pavements (the full thickness, between 150 mmand 200 mm, must be placed in one layer).

Reflection of shrinkage cracks must be expected where material with cementitious additive is used.In such situations, crack sealing maintenance work will be required.

3.4 Temporary connections for HILI pavements

In order to reduce the risk of requiring frequent repairs in difficult to access locations (e.g. underheavy traffic), temporary connections for HILI pavements must be, as a minimum, asphalt overcement stabilised (ASt(B)) pavement or asphalt over granular (AG(A)) pavement.

3.5 Asphalt pavements

Water contributes to stripping of the binder from the aggregate in asphalt pavements. To minimisethis, a polymer modified binder seal must be provided beneath all asphalt surface layers inpavements where the layer beneath the surface layer is also asphalt. For effective waterproofing,

the seal must have a minimum spray rate of 1.2 litres per square metre and cover aggregate withminimum nominal size of 10 mm. At locations subject to heavy braking and/or tight cornering, suchas intersections, roundabouts and approaches, excluding the seal can reduce the risk of shearing,but increase the risk of stripping of lower layers. Provision of a seal in these locations is notmandated. If a seal is provided the spray rate should be reduced to 1.0 to 1.2 litres per squaremetre to reduce the risk of shearing.

The binder for the waterproofing seal shall be an S4.5S polymer modified binder.

Use of SBS polymer modified binder in the asphalt can also help minimise stripping.

Moisture ingress during construction can lead to stripping. Dense graded asphalt mixes of 20 mmnominal size or larger are particularly prone to moisture ingress. To reduce the risk of moisture

ingress, construction sequencing should not leave DG20 layers exposed for more than tencalendar days and DG28 layers must not be left exposed for more than two calendar days. If this isunavoidable, a seal or minimum 50 mm DG14 layer should be placed to provide protection frommoisture ingress.

3.6 Working platform

A working platform must be used for all HILI and ASt(A) pavements and is recommended for allother pavements with average daily ESA 1000 in the design lane in the year of opening.

A working platform must be used for all temporary pavements where the design subgrade CBR isless than 5%.

The working platform is located below the lowest pavement layer. Its function is to provide:

a) access for construction traffic


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b) a sound platform on which to construct the pavement layers

c) protection to the subgrade for the life of the pavement.

The design, construction and maintenance of the working platform are the responsibility of theContractor, but must include the specified in-service requirements given in Section 5.5. The in-service requirements are for the sole purpose of providing a satisfactory substrate layer for the fullservice life of the pavement.

3.7 Settlement

Neither this manual nor Part 2 of the Austroads guide include provisions to deal with settlementbelow the pavement layers. Where required, additional geotechnical investigations andassessments shall be carried out to determine if and how much settlement may occur. If settlementis likely, pre-treatment (e.g. drainage and/or surcharge of the formation) is required to reduce theextent of settlement after the pavement is constructed.

3.8 Moisture ingress and maintenance

Pavement surface courses, seals and all drainage must be adequately maintained. Failure tomaintain seals and drainage will cause, at least, loss of service life in most pavements and atworst, failure. Unbound granular pavements are particularly susceptible to loss of service life andfailure caused by the infiltration of water.

Rain following a long period of dry weather is particularly hazardous because:

a) During long periods of dry weather there may be no stimulus to adequately maintain sealsand drainage in a budget constrained environment, which could result in pavements that arenot protected upon the onset of wet weather.

b) Shrinkage of materials may generate cracks that will allow rapid entry of water.

3.9 Trafficking of incomplete pavementPavement damage resulting from temporarily trafficking pavement layers below the final surfacemust be included in the pavement design calculations.

3.10 Thickness of bituminous seals

For the purpose of determining survey levels, the thickness of seals and primerseals shall be takenas the average least dimension (ALD) of the cover aggregate. If the ALD is not known at the timeof design, the ALD can be estimated as 6 mm for 10 mm nominal size cover aggregate and 9 mmfor 14 mm nominal size cover aggregate.


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January 2009 23

4 ENVIRONMENT

4.1 General

Water and temperature have a major effect on pavement performance. Temperature directly

affects the performance of seals, asphalt and concrete, and water directly affects the performanceof unbound granular pavements and subgrades. Water can also affect asphalt. Knowledge ofenvironmental conditions is essential for the design, construction and maintenance of pavements.

4.2 Climatic zones

Figure 4.2-1 illustrates Australian climatic zones on the basis of temperature and humidity. Most ofcoastal Queensland is classified as having hot humid summers. Western areas have hot drysummers with either mild or cold winters. Further information on climate zones and climateaverages is available from the Commonwealth Bureau of Meteorology at www.bom.gov.au.

Figure 4.2-1 Australian climatic zones (www.bom.gov.au)

Figure 4.2-2 illustrates Australian seasonal rainfall zones.


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Figure 4.2-2 Australian seasonal rainfall zones (www.bom.gov.au)

4.3 Water environment

Average annual rainfall and evaporation rates for Queensland are shown in Figure 4.3-1 andFigure 4.3-2.

Figure 4.3-1 Average annual rainfall for Queensland (www.bom.gov.au)


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January 2009 25

Figure 4.3-2 Average annual evaporation for Australia (www.bom.gov.au)

In the 1950s, C. W. Thornthwaite, Professor of Climatology at John Hopkins University, introduceda method to study the climate synthetically, which combined rainfall and PotentialEvapotranspiration (PET).

PET represents the water quantity that soil would lose because of surface evaporation and plant

transpiration in an environment where continuous soil water storage exists. When PET is exactlybalanced by rainfall over the year and water is available, there is neither a deficit (d) nor surplus (s)of water.

Thornthwaite defined a total moisture index (MI) as shown in Equation 4-1.

Equation 4-1

100 ( )s dMI

PET

=

It follows that when rainfalls are lower than PET, MI is negative and the climate is dry. Whenrainfalls are higher than PET, the MI is positive and climate is wet. The climate classification basedon MI is given in Table 4.3-1.

Figure 4.3-3 shows the MI values for Queensland. A comparison between Figure 4.3-1 andFigure 4.3-2 shows that regions with a rainfall below 600 mm have a negative MI and hence aredry as the evapotranspiration exceeds the rainfall. Areas with an annual rainfall less than 500 mmare semi-arid.


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Table 4.3-1 Climatic types according to the total moisture index (MI)

Symbol Climatic type MI

A Very humid Over 100

B4 Humid 80 to100

B3 Humid 60 to 80

B2 Humid 40 to 60

B1 Humid 20 to 40

C2 Sub-humid 0 to 20

C1 Sub-dry -33 to -0

D Semi-arid -66 to -33

E Dry -110 to -66

Figure 4.3-3 Thornthwaite moisture index for Queensland(contours at intervals of 5 units)


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January 2009 27

4.4 Minimising exposure to and influence of water

4.4.1 General

It is not possible to completely prevent the influence of water on pavements and subgrades.

Increased water content in the pavement, including temporary pavements, and/or subgrade can

occur for reasons such as:

a) rain, particularly on unprotected and/or poorly maintained pavements

b) inundation

c) positive water head

d) ponded water

e) construction water

f) inadequate subsurface drainage

g) soil suction from areas such as adjacent ponded water and/or water tables. In high capillary

rise soils, water as deep as 10 m can influence the pavement and subgrade.Selection of pavement type and overall design (cross-section, embankment height, surface andsub-surface drainage, etc.) depends not only on load intensity, material availability and industrycapacity, but also on exposure to water during construction and service life.

4.4.2 Design requirements

The following are required to reduce exposure to and influence of water:

a) seal over the full width of the formation

b) verge with low permeability and low swell on the high side of one-way cross-falls including atleast an additional 100 m at either end from where the transition to a crowned pavementcommences

c) adequate surface drainage including

i) table drains (when used) located well away from the formation (min. 5 m) in flat orlightly undulating country or excluding them altogether. Water should always bedirected away from the formation or, if this is not possible, drains should be located atleast 5 m away from the edge of the formation.

ii) edge drains on embankments and directing the concentrated outflows away from theformation via drains with impermeable lining

iii) full-width sealed formation and concrete channel in cuttings or, preferably for unboundgranular pavements, providing table drains in cuttings.

d) cuttingsSubsoil drains must be provided at all times. There may also be the need for a drainage layerto intercept water under positive head, break capillary rise and/or provide additionalsubsurface drainage to intercept ground water. In cuttings with rock floors a stabilised infilllayer with surface cross-fall must be provided so that water ponding does not occur.

e) adequate embankment height above the water table or standing water

Water will travel long distances and rise to considerable heights because of capillary action.Embankments must be at least the required height above the water table or standing waterfor the particular embankment material (untreated or treated) used, or a drainage/capillarybreak layer must be provided on top of the subgrade and above the level of the water tableor standing water.


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The minimum embankment height where there is no inundation and/or standing water orwater table, measured to the bottom of the lowest pavement layer at the outside edge, abovethe natural surface should be

i) in regions with Thornthwaite Index 0 and rainfall > 500 mm/year, above the influenceof any water, but not less than 200 mm from the natural ground to the underside of thelowest pavement layer

ii) In regions with Thornthwaite Index < 0, in particular for reactive subgrades where thereis no cover to reactive subgrade provided, the thickness should be determined as abalance between keeping the pavement above water and minimising the potential forchange in subgrade water content that could cause volume change. In such areas, theminimum height should be 100 mm, unless some unusual condition, such as a perchedwater table, irrigation, etc. is likely to exist. The slope of the edge of the pavementshould be 25%.

f) inundation

Where inundation of any part of a pavement is possible, an assessment of the amount of

water infiltration, either caused by positive head or capillary action, has to be carried out andthe effect on the pavement and subgrade determined. Where it is determined that a loss ofservice life and/or pavement damage is likely, alternative designs have to be considered.These could include re-alignment, higher embankments and/or use of a pavement type thatis less sensitive to water, such as a concrete pavement.

g) Asphalt surface layers are not impermeable and must have a polymer modified sealimmediately beneath them (refer Section 3.5).

h) Pavement must be properly compacted right to its edge, and any excess, poorly compactedpaving material beyond the seal edges is to be removed.

i) kerbed pavements

Subsoil drains must be provided at all times.

j) changes in pavement structure

Pavement drains, for the purpose of draining the pavement layers and working platform,must be provided at all transverse and longitudinal interfaces between pavements withdifferent structures (i.e. layer types and/or layer thicknesses). For example, a longitudinalpavement drain is typically required when widening an existing pavement.

The invert of a pavement drain must be lower than the underside of the lowest pavementlayer, and where there is a working platform, the invert must also be lower than theunderside of the working platform.

4.4.3 During construction

Good surface and subsurface drainage must be provided and maintained at all times. Surfacesmust be left free-draining and compacted following completion of work and before any rain.

A working platform provides protection to the subgrade. Where neither a working platform norsome other form of positive protection is provided to the subgrade, reworking and/or delay must befactored into the construction program to overcome the effects of rain and/or inundation duringconstruction.

Asphalt and unbound granular materials are extremely susceptible to damage resulting fromincreased water content during construction.

4.5 Situations where pavement or subgrades cannot be protected

Where it is decided to provide a road that is not adequately protected from the infiltration of water,such as very low volume roads, particularly in arid regions, a high water content management plan


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solution may be adopted with the approval of the General Manager (Engineering & Technology).This involves monitoring the pavement after rain and/or inundation and/or when water has beenstanding and, if necessary, restricting the movement of traffic. Restrictions could include trafficlimitations on the outside edge of the pavement, restricted loads and so on, until the pavement andsubgrade have dried. This relaxation in design must not be applied to roads with average dailyESA > 100 in the design lane in the year of opening.

For all other cases, a concrete or asphalt surfaced concrete pavement must be provided with adesign subgrade strength that reflects the measures to control volume change as per Clause 5.3.

4.6 Temperature environment

The effect of temperature on asphalt is incorporated into the design method through the use of theWeighted Mean Annual Pavement Temperature (WMAPT) for the project location. The WMAPTsfor various sites in Queensland are listed in Appendix 2 of this manual.

Unbound granular pavements, except for seals, are normally not influenced by temperature.

The influence of temperature has been accommodated in the specifications for concrete

pavements. However, during construction the whole concrete pavement cross-section must becompleted within a month to minimise problems generated by differential movement.

In Flexible Composite pavements, the asphalt must be placed within a month of placement of thelean mix concrete subbase. If this is not possible, a SAMI must be provided above the lean mixconcrete subbase, prior to placing any asphalt, as wide shrinkage cracks may occur.


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5 SUBGRADE

5.1 General

The subgrade can comprise alternatives including one or a combination of the following:

a) working platform

b) capping layer

c) drainage layer

d) select fill

e) general fill

f) treated in situ material

g) natural unprocessed in situ material, other than that moved from another location and/orcompacted.

In pavement thickness design calculations, fill and/or in situ untreated subgrade materials to aminimum depth of 1.5 metres below the underside of the lowest pavement layer must be included.

This manual describes soils according to the Unified Soil Classification System, which uses a two-letter code to indicate soils classification (refer Appendix 1).

5.2 Subgrade assessment

5.2.1 General

The untreated subgrade has to be assessed for the following:

a) suitability of embankment material for the design and conformance to specifications

b) suitability of in situ material for any necessa

Pavement Design Manual Jan 09[1]

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