Pavement Design Manual Jan 09

PAVEMENT DESIGN MANUALSupplement to Part 2: Pavement Structural Design of 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

IMPORTANT INFORMATIONThe requirements of this document represent Technical Policy of Main Roads and contain Technical Standards. Compliance with Main Roads Technical Standards is mandatory for all applications for the design, construction, maintenance and operation of road transport infrastructure 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 to improvement suggestions by users. Please send your comments and suggestions to the feedback email given below.

FEEDBACKYour 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 the conditions prescribed under the Copyright Act, reproduction by any means (including electronic, mechanical, photocopying, microcopying or otherwise) is prohibited without the prior written permission of the Queensland Department of Main Roads. Enquiries regarding such permission should be directed to the Road & Delivery Performance Division, Queensland Department of Main Roads.

DISCLAIMERThis publication has been created for use in the design, construction, maintenance and operation of 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 the completeness, accuracy or adequacy of the publication or any parts of it and accepts no responsibility or liability upon any basis whatever for anything contained in or omitted from the publication 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 Queensland and a contractor, this disclaimer applies subject to the express terms of that contract.January 2009

Queensland Department of Main Roads

Pavement Design Manual

Table of Contents1 INTRODUCTION...............................................................................................................................1 1.1 1.2 1.3 Foreword ..................................................................................................................................1 MR Pavement Design System .................................................................................................1 Scope and applicability ............................................................................................................2 1.3.1 General ......................................................................................................................2 1.3.2 Applying the MR Pavement Design System..............................................................2 1.3.3 MR Pavement Design System policy parameters .....................................................3 Definitions ................................................................................................................................4 Overview of MR Pavement Design System .............................................................................8 2.1.1 Design models and mechanical properties................................................................8 2.1.2 Designers...................................................................................................................8 2.1.3 Unbound granular design charts ...............................................................................8 2.1.4 Mechanistic design ....................................................................................................8 2.1.5 Estimate of life ...........................................................................................................8 Reliability..................................................................................................................................8 Selecting a trial pavement configuration and minimum standards ..........................................9 2.3.1 General ......................................................................................................................9 2.3.2 Project-specific factors.............................................................................................10 2.3.3 Specifications...........................................................................................................10 2.3.4 Minimum pavement standards ................................................................................10 Shoulders ...............................................................................................................................17 2.4.1 General ....................................................................................................................17 2.4.2 Shoulders with a lower structural standard..............................................................17 2.4.3 Unsealed shoulders .................................................................................................18 General ..................................................................................................................................20 Unbound granular ..................................................................................................................20 Stabilised materials ................................................................................................................20 Temporary connections for HILI pavements ..........................................................................21 Asphalt pavements.................................................................................................................21 Working platform ....................................................................................................................21 Settlement ..............................................................................................................................22 Moisture ingress and maintenance ........................................................................................22 Trafficking of incomplete pavement .......................................................................................22 Thickness of bituminous seals ...............................................................................................22 General ..................................................................................................................................23 Climatic zones........................................................................................................................23 Water environment.................................................................................................................24 Minimising exposure to and influence of water......................................................................27 4.4.1 General ....................................................................................................................27 4.4.2 Design requirements................................................................................................27 4.4.3 During construction..................................................................................................28 Situations where pavement or subgrades cannot be protected ............................................28 Temperature environment......................................................................................................29 General ..................................................................................................................................30

1.4 2 2.1

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

2.2 2.3

2.4

3

CONSTRUCTION AND MAINTENANCE CONSIDERATIONS......................................................20 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10

4

ENVIRONMENT..............................................................................................................................23 4.1 4.2 4.3 4.4

4.5 4.6 5 5.1

SUBGRADE ....................................................................................................................................30

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5.2

5.3

5.4 5.5

5.6 5.7 5.8 5.9 6 6.1

Subgrade assessment........................................................................................................... 30 5.2.1 General ................................................................................................................... 30 5.2.2 Laboratory CBR test conditions .............................................................................. 31 5.2.3 Statistical analysis of CBR data .............................................................................. 31 5.2.4 Adoption of presumptive CBR values ..................................................................... 31 5.2.5 Variation in subgrade support with moisture changes ............................................ 32 Subgrade water-induced volume change.............................................................................. 32 5.3.1 General ................................................................................................................... 32 5.3.2 Minimising volume change...................................................................................... 33 5.3.3 Cover over reactive subgrade................................................................................. 33 Select fill and treated material ............................................................................................... 34 Working platform ................................................................................................................... 34 5.5.1 In-service requirements .......................................................................................... 34 5.5.2 Contractors design requirements........................................................................... 35 Capping ................................................................................................................................. 35 Drainage layer ....................................................................................................................... 36 Combined subgrade treatments ............................................................................................ 36 Elastic characterisation of subgrade materials...................................................................... 39 Unbound granular.................................................................................................................. 40 6.1.1 General ................................................................................................................... 40 6.1.2 Determining modulus of unbound granular materials ............................................. 40 Modified granular materials ................................................................................................... 41 Stabilised granular material................................................................................................... 41 6.3.1 General ................................................................................................................... 41 6.3.2 Determining design modulus and Poissons ratio................................................... 42 6.3.3 Cracking .................................................................................................................. 42 6.3.4 Minimising cracks.................................................................................................... 43 Lean mix concrete ................................................................................................................. 43 Asphalt................................................................................................................................... 44 6.5.1 Asphalt types........................................................................................................... 44 6.5.2 Determining asphalt modulus and Poissons ratio.................................................. 44 6.5.3 Recycled asphalt..................................................................................................... 46 6.5.4 Minimising water infiltration..................................................................................... 46 Concrete ................................................................................................................................ 46 6.6.1 Base concrete ......................................................................................................... 46

PAVEMENT MATERIALS .............................................................................................................. 40

6.2 6.3

6.4 6.5

6.6 7

DESIGN TRAFFIC.......................................................................................................................... 47 7.1 Average daily ESA in design lane in year of opening ........................................................... 47 7.2 Selecting design period and assessment period................................................................... 47 7.3 Identifying design lane........................................................................................................... 47 7.4 Initial daily heavy vehicles in the design lane........................................................................ 47 7.5 Growth rate and cumulative traffic volumes .......................................................................... 48 7.6 Project specific traffic load distribution .................................................................................. 48 7.7 Reduced design standard for sealed unbound granular pavements with average daily ESA < 100 in design lane in year of opening.................................................................................................... 48

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DESIGN OF NEW FLEXIBLE PAVEMENTS ................................................................................. 50 8.1 8.2 General.................................................................................................................................. 50 Mechanistic procedure .......................................................................................................... 50 8.2.1 Selecting a trial pavement....................................................................................... 50 8.2.2 Consideration of post-cracking phase in cemented materials ................................ 50 Empirical design of unbound granular pavements with thin bituminous surfacing ............... 50 Modified granular pavements ................................................................................................ 51 Example design charts for mechanistic design ..................................................................... 51January 2009

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DESIGN OF NEW RIGID PAVEMENTS.........................................................................................52 9.1 9.2 9.3 9.4 General ..................................................................................................................................52 Pavement types .....................................................................................................................52 Concrete channels .................................................................................................................52 Example design charts for rigid pavements ...........................................................................53

10 COMPARISON OF DESIGNS ........................................................................................................54 10.1 General ..................................................................................................................................54 10.1.1 Assessment period ..................................................................................................54 10.1.2 Design inclusions.....................................................................................................55 10.1.3 Determining the optimal solution .............................................................................55 10.1.4 Selection constraints................................................................................................56 11 TYPICAL CROSS SECTIONS ........................................................................................................57 11.1 Typical cross sections ............................................................................................................57 11.2 Pavement structures ..............................................................................................................58 11.3 Pavement edge details...........................................................................................................60 12 REFERENCES................................................................................................................................61 APPENDIX 1 .............................................................................................................................................I APPENDIX 2 ............................................................................................................................................II

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11.1

INTRODUCTIONForeword

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 to Pavement 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 the other components of the MR Pavement Design System, provides requirements for the design of new 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 pavement design requirements. For most fundamental design principles Part 2 of the Austroads guide is used. For Main Roads purposes, the MR components of the Pavement Design System take precedence over Part 2 of the Austroads guide, if and where they differ. The MR Pavement Design System includes all the following documents, systems and design properties: a) MR documents and systems i) ii) iii) iv) v) vi) vii) viii) ix) x) b) c) Pavement Design Manual standard specifications supplementary specifications technical standards standard drawings standard test methods technical notes engineering policies engineering notes quality requirements

Part 2: Pavement Structural Design of the Austroads Guide to Pavement Technology design properties i) Material design properties must be those stipulated in the MR Pavement Design System described above. In particular, properties such as moduli, fatigue constants and Poissons ratios must be those stipulated in this manual, or if not stated, those given in Part 2 of the Austroads guide. The design properties used in the MR Pavement Design System are based on the products, components and materials of the pavement conforming to the requirements of the documents listed in 1.2 a) above.

ii)

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1.31.3.1

Scope and applicabilityGeneral

The MR Pavement Design Manual is intended as a guide for professional, trained, experienced and knowledgeable pavement designers who are required to: a) b) c) d) 1.3.2 a) work within the confines of Main Roads organisational policies, guidelines and road network requirements be aware of, assess and apply risk management and budgetary constraints to the road system as a whole and its various components take into account local area or project specific issues optimise initial designs and in-service treatments to suit budget and whole-of-life cost issues. Applying the MR Pavement Design System 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 be substituted for those required by the MR Pavement Design System. not be used on its own to form part of any contract including, but not limited to, those for the following delivery mechanisms i) ii) iii) iv) v) vi) design design and construct design-construct-maintain alliance partnering build-own-operate-transfer

The MR Pavement Design System must:

b)

In such cases, a separate, comprehensive and robust set of project-specific requirements must be developed. c) not be used for performance based contracts and/or with performance based specifications. Performance contracts and standards must be based on functional requirements guaranteed for the service life of the project. not be used in isolation where functional requirements are specified. Where used by Main Roads as part of an infrastructure delivery model that includes functional requirements, achievement of the functional requirements must be based on requirements for initial construction and interventions that involve periodic treatments including overlays, reseals, rejuvenation, re-texturing and so on. not be used for any purpose other than within the context described above. In particular, it must not be used for i) designing facilities other than those to be designed directly for Main Roads. It must not be used for facilities including, but not limited to container and freight yards, mining roads and airports. designing facilities for any Legal Entity other than the State of Queensland designing projects with parameters other than those set out in Section 1.2 for the Queensland road network unsealed pavements; segmental block or flag pavements; roller compacted concrete pavements; or any pavement not covered by an MR standard.

d)

e)

ii) iii) iv)

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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 in construction control and ongoing maintenance and rehabilitation) the analytical processes and tools 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 an acceptable 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 best serve the needs of the MR controlled road network as a whole and applies only in this context. The policy parameters that provided guidance and the context of developments to date have included: a) a historic priority for i) ii) all-weather connections with the consequence of lower initial standards in order to favour maximum length constructed an adequate level of service over the whole network within the context of budgetary constraints and the comparatively large geographical area with relatively low population density

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. high cost of maintenance interventions and associated user disruptions on highly trafficked urban roads, leading to the lowest whole-of-life cost solution for such pavements being high load intensity low intervention (HILI) pavements 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 stiffer and stronger pavement bases and surface layers. increased expectations about safety requirements, leading to increases in surface property requirements such as macrotexture and microtexture but also requiring stiffer and stronger pavement base layers to support these requirements a greater emphasis on whole-of-life cost rather than initial cost.

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

b)

c)

d)

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1.4

DefinitionsTable 1.4-1 DefinitionsTerm Description The time span over which total costs for the pavement are determined so that wholeof-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 be several design periods within the assessment period due to decisions to reconstruct or rehabilitate the pavement at intermediate intervals. Part 2: Pavement (Austroads 2008) Structural Design Guide to Pavement Technology

assessment period

Part 2 of the Austroads guide base layer binder layer

The main structural layer nearest to the surface in a pavement. An asphalt layer that is placed between an asphalt base layer and an asphalt surface layer. The binder layer is included for its better workability to reduce permeability and improve roughness levels. A layer that provides cover over an in situ material that has a design CBR of less than 3.0% but not less than 1.0%. California bearing ratio A thickness of material beneath the lowest pavement layer intended to reduce waterinduced volume change effects on the pavement where there are in situ materials with the potential for water-induced volume change. Cover thickness may include any working platform, select fill, capping layer and/or drainage layer. Differential movement, usually vertical, in a concrete pavement caused by temperature differences through the cross-section of the pavement. Materials and/or components within a product. A pavement structure consisting of a minimum total thickness of 175 mm of dense graded asphalt over a cementitiously stabilised subbase (subbase thickness range 150200 mm). Main Roads definition (this applies to Main Roads works) The time span considered appropriate for the major structural elements of the road pavement to function without rehabilitation and/or reconstruction. Treatments, such as replacement of surfacing layers and stage construction treatments, that maintain the integrity of the other components of the pavement are included within the design period. Austroads definition The time span considered appropriate for the road pavement to function without major rehabilitation and/or reconstruction. A layer located between the pavement and the untreated subgrade that intercepts water and/or breaks capillary rise.

capping layer CBR cover over reactive subgrade

curling constituents deep strength asphalt pavement design period

drainage layer

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Term flexible composite pavement flexible pavement full depth asphalt pavement functional characteristics functional requirements HILI pavement load intensity

Description A pavement structure consisting of a minimum total thickness of 175 mm of dense graded asphalt over a lean mix concrete subbase (subbase thickness range 170 240 mm). Unbound granular, modified granular or asphalt pavements. A pavement structure consisting of full depth asphalt usually over a working platform. Characteristics provided by the particular pavement that address the necessities for traffic and are expressed in terms of lane availability, rideability, grade, cross-fall, water film thickness, flood immunity, skid resistance, etc. Requirements related to a standard of service for the pavement user, such as roughness, grade, cross-fall, rutting, surface defects, texture depth, skid resistance, delineation, visibility, etc. High load intensity, low intervention pavement as defined in Table 2.3-2. Traffic loading applied to the pavement over a specified time period, comprising the accumulation of applications of a variety of pavement contact stresses and repetitions derived from the traffic spectrum, vehicle frequency and growth rate. The layer beneath the subbase layer A low pavement water content environment is where the pavement: a) has an adequate and well maintained seal; b) is not subject to flooding; c) has adequate surface and subsurface drains; d) has no standing and / or ponded water within 5 m laterally of the trafficked lane(s); e) has no water within 2 m vertically from the bottom of the lowest pavement layer unless there is a minimum 150 mm thick capillary break layer; and f) is located where the average rainfall is less than 500 mm / year and the Thornthwaite Index is less than 0. The State of Queensland operating through the Queensland Department of Main Roads Properties that can be used as direct inputs into a mathematical equation and/or model, such as layered linear elastic theory or finite element. At this time only the layered linear elastic model CIRCLY is calibrated for use. Main Roads Pavement Design System as defined in Section 1.2 and applied as described in Section 1.3. This manual. Main Roads standard specifications, technical standards and supplementary specifications current at the time of use. The restoration of an unplanned distressed/failed pavement or the extension of the life of a pavement that has exceeded its design life, so that it may be expected to function at a satisfactory level of service for a further Design Period.

lower subbase low pavement water content environment

Main Roads (MR) mechanical properties MR Pavement Design System MR Pavement Design Manual MR Specifications and Standards pavement rehabilitation

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Term pavement permanent pavement property reactive subgrade rigid pavement safety

Description A pavement that will be used by traffic and designed and constructed in accordance with the Main Roads Pavement Design System, including this manual. Any pavement that is not a temporary pavement. Result of a test method that is used to provide useful information about a material or product. A subgrade material with CBR swell greater than or equal to 0.5%. A pavement of Portland cement concrete or having a Portland cement concrete base course. Qualities of the pavement and associated facilities that directly affect vehicle safety related to but not limited to: surface type, surface texture, skid resistance, surface drainage, cross-fall, delineation, sight distance, guide posts, lighting and guardrail. A lowering of the height of the pavement and subgrade as a result of loading imposed by traffic, the pavement and/or the embankment, and caused by creep, shear or reduction in volume. A subgrade that has been stabilised with chemical binders and site investigation and laboratory testing has verified that the intended long-term properties of the stabilised material will be achieved. The structural contribution of the layer may be considered in the same manner as an un-stabilised select fill with a material CBR determined by a CBR test, but not greater than 20% and subject to the maximum modulus that can be developed when sub-layered as an unbound material. Treatments to the pavement during its design period by programmed strengthening that occur in a way that maintains the structural capacity of the original pavement layers for the design period (eg. overlays). The layer beneath the base layer The level of the interface between the bottom of the pavement and the top of the Subgrade. Subgrade material includes working platform, select fill, treated material, drainage layer, capping, general fill and Untreated Subgrade to a minimum depth of 1.5 m below the bottom of the pavement. The layer in immediate contact with traffic. 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 Roads Pavement Design System and the requirements for temporary pavements in this manual. The design, material and construction requirements for temporary pavements are the same as for permanent pavements, unless specifically stated otherwise. Unless otherwise noted a test method as specified in the relevant Main Roads specification, technical standard, or supplementary specification.

settlement

stabilised subgrade

staged construction

subbase layer subgrade level subgrade material

surface layer temporary pavement

test method

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Term treated material UCS unbound granular pavement material unbound granular acceptable environment

Description Material treated with lime and/or cement in accordance with the relevant Main Roads specification, technical standard, or supplementary specification. Unconfined compressive strength. A material complying with the relevant Main Roads specification, technical standard, or supplementary specification that consists of graded aggregates and may include clay. An unbound granular acceptable environment generally includes, in addition to the specification requirements: a) Full width seal (an alternative for low traffic volumes is a low permeability select fill unsealed shoulder where whole-oflife costing confirms it is economical for the particular situation); b) Adequately designed, constructed and maintained surface and subsurface drainage; 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 break layer; 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 can be used for subbase in low pavement water content environements); i) Pavement is not subject to water inundation or flooding that lasts for more than 1 day (protection such as fully enclosed low permeability verges, drainage / capillary break layer, full width seal and pavement drains may be required). Natural unprocessed material, other than that moved from another location and/or compacted at the location, where the characteristics of the subgrade are to be determined to assess: a) the need for one or more of the following elements: capping layer; cover over reactive subgrade; drainage layer and/or combined capping/drainage layer b) subgrade design CBR and swell. Differential movement, usually vertical, in a concrete pavement caused by water content differences through the cross-section of the pavement. Change in the volume of the subgrade material resulting from a change in water content usually on a reactive subgrade material. The product of the plasticity index and percentage passing the AS 0.425 mm sieve 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.

untreated subgrade

warping water-induced volume change weighted plasticity index (WPI) working platform

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22.12.1.1

PAVEMENT DESIGNOverview of MR Pavement Design SystemDesign models and mechanical properties

Pavement design comprises empirical and mechanistic components. The MR Pavement Design System utilises mathematical models to provide a logical framework within which to apply existing knowledge to the structural design of pavements. The models utilise mechanical properties such as modulus and Poissons Ratio. However, the direct measurement of these mechanical properties and the mechanistic model are not as robust as in other disciplines. Direct measurements must: a) b) c) d) 2.1.2 be statistically analysed to account for the considerable variation in pavement materials have a 95% confidence level applied, unless stated otherwise be considered as information additional to and integrated with values interpolated and/or extrapolated from the total calibration of the model be used only in the context of the overall design system. Designers

Where provided, the values given in the MR Pavement Design Manual must be used. Adequate design is possible only when carried out by professional, trained, experienced, and knowledgeable personnel. It requires consideration and integration of all inputs including local conditions, material characteristics, cross-sections, loading, design models, road user safety and constructability. 2.1.3 2.1.4 Unbound granular design charts Mechanistic design The unbound granular design chart considers only rutting and shape loss. 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 thickness considers 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 intersections and on curves, or by environmental influences such as temperature and water, are not directly assessed by these design methods. These forms of distress have to be constrained by other means 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 be used 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 pavement elements. 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. Regular pavement monitoring, with input from designs in accordance with this Manual, is essential to determine 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 only the following structural distress modes:

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a)

for pavements designed with layered linear elastic theory i) ii) iii) fatigue of asphalt fatigue of cemented materials rutting and shape loss of unbound granular materials and subgrade fatigue of concrete base erosion of subbase/subgrade.

b)

for concrete pavements designed with Westergaard and finite element theory i) ii)

These reliability guidelines were based on general assessments of network performance. As the underlying causes of performance vary widely over the network, these probabilities can not be used for determining the reliability of a specific project or in the contract interface for a specific project. The reliability guidelines are not appropriate for assessing reliability for other distress modes including, but not limited to, stripping or rutting of asphalt, roughness, skid resistance, and distress caused by environmental factors. The choice of reliability is influenced by the classification/function of the road, its location and intended usage both prior to and after the completion of the design period. It is to be defined in accordance with Main Roads policy. Judgement of the appropriateness of the reliability level has to be 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 levelsRoad category All roads, or sections of road, where intervention costs are very high or traffic management is very difficult1 Motorways, highways and main roads with lane AADT > 2000 Highways and main roads with lane AADT > 500 and 2000 Minor roads with lane AADT 500Note: 1) Examples include high traffic volume metropolitan highways and arterials roads, mountainous sections, flood-ways, intersections and approaches to structures such as bridges.

Reliability (%) 97.5 97.5 95 90

2.32.3.1

Selecting a trial pavement configuration and minimum standardsGeneral

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 straight alignments with flat grades. The minimum layer thicknesses given are absolute minimums and the actual 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 resulting from the temporary trafficking must be included in the design calculations for the permanent pavement.

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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 the development of the pavement type selection tables. Consequently, there will be occasions when the 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) b) c) d) e) f) g) h) i) j) horizontal shear stresses on grades, curves and intersections pavement contact stresses higher than those used in the development of the current pavement design models and specifications availability of materials availability and adequacy of construction equipment, materials and expertise construction constraints (e.g. construction under traffic) changes to the function/classification of the road during the design period changes to the road network during the design period specific functional requirements (e.g. safety, noise) current and future traffic characteristics settlement and/or water-induced volume change. Where settlement and/or water-induced volume change is likely and cannot be reduced to an acceptable level, stiff pavements, such as concrete, stabilised or modified, must not be used. whole-of-life costs. Whole-of-life costs must include direct and indirect costs of interventions such as raising drainage structures, increasing clearances, raising safety barriers, providing temporary access, maintaining alternative routes, delays and disruptions to road users, etc. current and future budget considerations. local environmental conditions, including i) ii) unbound granular pavements concrete pavements Concrete pavements must have their complete cross-section (thickness and width) completed within a month to minimise differential and potentially detrimental movement. iii) asphalt pavements Asphalt pavements must be kept as dry as possible as water is a contributor to stripping. 2.3.3 2.3.4 Specifications Minimum pavement standards Main Roads specifications or technical standards shall be used. Minimum pavement standards are given in Table 2.3-1 to Table 2.3-5, with primary selection based on 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 a higher 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 include those described below: 1) asphalt over granular pavements

k)

l) m)

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For asphalt over granular pavements, the lowest whole-of-life cost usually occurs when the asphalt thickness is sufficient to enable the asphalt to achieve a fatigue life at least the same as a reasonable pavement design life and the subgrade rutting life provided by the cover over 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 the pavement type, such as a) b) c) d) budget constraints for initial construction the cost-effectiveness of constructing relatively short sections the high cost of appropriate granular base materials noise.

In addition, in areas with surfaces subject to significant horizontal shear (such as grades, curves and intersections), the minimum thickness and type of asphalt should be determined so that it also accommodates this horizontal shear. In such cases the minimum thickness should be 100 mm. 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 available and 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 their performance has been established locally, they are to be specified and constructed in accordance with local District requirements, but within the following requirements: a) b) The pavement must comprise a full depth modified material. The design modulus for the base must be determined from repeat load triaxial testing and 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. The absolute maximum design modulus of the base shall be 600 MPa. In all cases there must be a working platform and, where there is a reactive subgrade, cover over reactive subgrade. The pavement must have at least a two-coat bitumen seal. The potential for and risk associated with cracking must be recognized and accepted and appropriate interventions allowed for in the whole-of-life costing and maintenance during service; Modified granular pavements cannot be used where the average daily ESA in the design lane in the year of opening is > 1000 or only a HILI pavement type is given in Table 2.3-1.

c) d) e)

f)

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

Relatively thin asphalt surfaced granular pavements are those where the fatigue life of the asphalt cannot achieve a reasonable design life for the pavement. In these cases, the asphalt has to be regularly replaced, rejuvenated and/or overlaid.January 2009 11

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Table 2.3-1 Pavement type: applicationLocation Average daily ESA in design lane in year of opening1 < 10 SG(D) 2,3 AG(C)3 SG(D) 2,3 AG(C)3 SG(D) 2,3 AG(C)3 10 to < 100 SG(C) 2,3 AG(C) 2,3 SG(C) 2,3 AG(C) 2,3 SG(C) 2,3 AG(C)3 100 to < 1000 SG(B) 2,3 AG(A-C)3 ASt(A) SG(B) 2,3 AG(A-C)3 ASt(A) SG(B) 2,3 AG(A-C)3 1000 to < 3000 HILI SG(A) 2,3 HILI 3000 HILI

Type Permanent pavement

Rural

HILI

Urban

Temporary pavement

Rural and urban

ASt(B) AG(A)

ASt(B) AG(A)

Abbreviations HILI AG(A) AG(B) AG(C) AG(A-C) SG(A) SG(B) SG(C) SG(D) ASt(A) ASt(B)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 based on a heavy vehicle growth rate not exceeding 10.0% per annum. If the heavy vehicle growth rate exceeds 10.0% per annum in any of the first five years after opening, then the average daily ESA in the design lane for the first five years after opening shall be used instead. 2) Asphalt over granular pavement or HILI pavement instead of spray sealed granular pavement is required in areas with high horizontal 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 specified maximum degree of saturation.

High Load Intensity, Low Intervention pavement as defined in Table 2.3-2. 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 wholeof-life costing. Spray sealed granular pavement as defined in Table 2.3-4.

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

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Table 2.3-2 Pavement type details: high load intensity low intervention (HILI)Type Jointed plain (unreinforced) concrete Jointed reinforced concrete pavement Continuously reinforced concrete pavement Surface1,2 (asphalt surface not recommended) (asphalt surface not recommended) OG10 (min 30 mm); or OG14 (min 40 mm) (if required) DG14HS3 (if required) Full depth asphalt OG10 (min 30 mm): or OG14 (min 40 mm) DG14HS3 Deep strength asphalt OG10 (min 30 mm); or OG14 (min 40 mm) DG14HS3 Flexible composite OG10 (min 30 mm); or OG14 (min 40 mm) DG14HS3Notes: 1) Surface must comply with the Main Roads pavement surface property standards given in the MR Pavement Surfacings Manual. Asphalt over jointed plain concrete or jointed reinforced concrete not recommended because of reflective cracking. Asphalt over continuously reinforced concrete used if required (usually to reduce noise). Special prime over concrete 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 concrete in 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)), subject to the total thickness of binder layer plus surface layer being at least 100 mm where the base layer is not DG20HM or DG14HS. 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 that the 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 supplementary specification 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 granular subbase. 8) A 10 mm Class 170 bitumen seal protection layer must be included above the lean mix concrete.

Binder

Base Jointed plain (unreinforced) concrete Jointed reinforced concrete

Subbase

Subgrade

DG14HS3

DG20HM4,5

Cat 16 or Cat 2 stabilised granular7 (150 to 200 mm) Lean mix concrete8 (175 to 250 mm)

January 2009

Refer Section 3.6 and Chapter 5

DG14HS3 (if required)

Lean mix concrete (150 mm)

Continuously reinforced concrete

13



Table 2.3-3 Pavement type details: asphalt over granularStandard1 Surface2,3 Binder Base DG14 (min 50 mm) OG10 (min 30 mm) DG14 or (min 50 mm) OG14 (min 40 mm) DG204 (min 50 mm) DG284 (min 70 mm) DG144 (min 50 mm) DG14 (min 50 mm) DG204 (min 50 mm) DG284 (min 70 mm) OG10 (min 30 mm) DG14 or (min 40 mm) OG14 (min 40 mm) DG14 (min 45 mm) DG10 (min 35 mm) AG(C)7 4 8

Subbase SB1 (min 125 mm) SB29 (min 125 mm) SB18 (min 125 mm) SB29 (min 125 mm) SB18 (min 125 mm) SB29 (min 125 mm) SB29 (min 125 mm) SB18 (min 125 mm) SB29 (min 125 mm) SB18 (min 125 mm) SB29 (min 125 mm) SB18 (min 125 mm)

Subgrade

AG(A)

5

B18 (min 150 mm) B29 (min 150 mm) B18 (min 150 mm) B29 (min 150 mm) B28 (min 125 mm) B39 (min 125 mm) B2 (min 125 mm) B39 (min 125 mm)8

AG(B)6

SB29 (min 125 mm)

DG14 (min 45 mm)

SB49 (min 100 mm)

Notes: 1) Thin asphalt-surfaced granular options may have a low asphalt fatigue life, which decreases significantly with increasing load intensities. Frequently, where an asphalt surface is required for the whole project, a HILI pavement or a sealed granular pavement, as relevant, provides the lowest whole-of-life cost. However, an asphalt over granular pavement may be the appropriate choice where other factors dominate, such as when there is a restricted initial budget, short sections are to be constructed (e.g. for high stress areas) or there is an absence of suitable materials for the HILI or sealed granular options. All asphalt 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 size cover 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 asphalt over 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 working platform, in which case the pavement is called a full depth asphalt pavement. An unbound subbase shall not be used over a working 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. 8) At this time, these material types are only available for project specific work with the MR project specific supplementary specification for unbound granular materials. Contact Pavements & Materials branch for advice on their use. 9) A new MR specification for unbound granular pavement types is being developed. Until the new specification is issued, the current standard specification types that can be used are given in Table 2.3-6.

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Table 2.3-4 Pavement type details: sprayed seal granularMinimum material quality4 Standard Project location1, 2 AE AE AE AE SG(D)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 Surfacings Manual. 4) A new MR specification for unbound granular pavement types is being developed. Until the new specification is issued, the current standard specification types that can be used are given in Table 2.3-6. 5) At this time, these material types are only available for project specific work with the MR project specific supplementary specification for unbound granular materials. Contact Pavements & Materials branch for advice on their use.

Surface3 sprayed seal sprayed seal sprayed seal sprayed seal sprayed seal

Base B15 B2 B3 B4 B5

Upper subbase SB15 SB2 SB3 SB4 SB5

Lower subbase LSB15 LSB2 LSB3 LSB4 LSB5

Subgrade

SG(A) SG(B) SG(C)


Low pavement water-content

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Table 2.3-5 Pavement type details: asphalt over stabilised granularStandard Surface1,2 Binder Base Subbase Cat 16 or Cat 2 stabilised granular7 (150 to 200 mm) Cat 16 or Cat 2 stabilised granular7 (150 to 200 mm) Cat 16 or Cat 2 stabilised granular7 (150 to 200 mm) Cat 16 or Cat 2 stabilised granular7 (150 to 200 mm) Cat 16 or Cat 2 stabilised granular7 (150 to 200 mm) Cat 16 or Cat 2 stabilised granular7 (150 to 200 mm) Subgrade

DG145 OG10 (min 30 mm) or OG14 (min 40 mm)

DG14 (min 45 mm)

DG20

5

DG28 ASt(A)3 DG14

5

5

DG14 (min 45 mm)

DG20

5

DG28

5

ASt(B)4

OG10 (min 30 mm) or OG14 (min 40 mm) DG14 (min 50 mm)

DG14 (min 50 mm)

Cat 16 or Cat 2 stabilised granular8 (min 150 mm)

Cat 15 or Cat 2 stabilised granular8 (min 150 mm)

Notes: 1) Surface must comply with the Main Roads pavement surface property standards given in the MR Pavement Surfacings Manual. 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 graded asphalt (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 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. 5) DG14, DG20 or DG28 mix shall be selected to suit the situation. 6) At this time, these material types are only available for project specific work with the MR project specific supplementary specification 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 granular subbase. 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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Table 2.3-6 Current Main Roads standard granular types to be usedNew unbound granular types Current MRS11.05 materials to be used2 Any environment (unrestricted) Base materials B1 B2 B3 B4 B5 SB1 SB2 SB3 SB4 SB5 LSB1 LSB2 LSB3 LSB4 LSB5Notes: 1) At this time, material types B1, SB1 and LSB1 are only available for project specific work with the MR project specific supplementary specification for unbound granular materials. Contact Pavements & Materials branch for advice on their use. 2) A new MR specification for unbound granular pavement types is being developed. Until the new specification is issued, the current standard specification types that can be used are given in this table.

Low pavement water-content environment only (low moisture) 3.1 3.2, 4.2 3.3 3.4, 4.4 3.5 3.5, 4.5

Note 1 1.1, 2.1 1.1, 2.1 1.1, 2.1 2.2 Subbase materials Note 1 1.2, 2.3 2.3 2.3 2.4 Lower subbase materials Note 1 2.5 2.5 2.5 2.5

2.42.4.1

ShouldersGeneral

There are two broad design alternatives for shoulders. The preferred design alternative is to continue 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 variability and/or moisture ingress. The second, less preferred alternative is to design and construct the shoulder to a lower structural standard 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 HILI pavements, 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 is provided, the following must be adopted:

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a) b)

Total pavement thickness of the shoulder shall be the same as the adjacent through lane. Where the adjacent structural section of the pavement is full depth asphalt, deep strength asphalt or flexible composite, thick asphalt over granular or thick asphalt over stabilised pavement, the shoulder shall have the same asphalt surface, seal and binder courses as the structural 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 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 SB2 material. A pavement drain shall be provided at the interface of the two pavements. Where the adjacent structural section of the pavement is asphalt surfaced granular or sealed granular pavement, the shoulder shall have the same asphalt surface course(s) and/or seal as the structural section. The shoulder shall also have the same granular base layer(s) and materials as the structural section. Other layers required to make up the design thickness for the shoulder are to be the same thickness and material type as used in the adjacent layers in the structural pavement. The balance of the thickness of the shoulder to the level of the lowest pavement layer is to be a select fill material. It must not be a general fill material. Where the adjacent structural section of the pavement is concrete, the shoulder shall have the same asphalt surface, seal and binder courses (where they exist) as the structural section. The minimum total thickness of DG14HS shall be 100 mm. 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 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 SB2 material. A concrete edge drain shall be provided at the interface of the two pavements. In all cases sealing is to continue to the outside edge of any verge or outside edge of the shoulder if a verge does not exist. A lower standard shoulder is not permitted on the high side of one-way crossfalls as this could result in moisture entering the pavement.

c)

d)

e) f)

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 the thickness of the shoulder. There are some limitations to the use of lower structural standard shoulders that need to be addressed when they are being considered for a particular project. These include the following: Construction may be more difficult because of increased complexity and narrow working widths. 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 the through lanes may be restricted by the lower structural capacity of the shoulder. Some shoulders may experience regular trafficking because of the nature of the road alignment (e.g. curves, end of tapers, narrow through lanes, access points, intersections and/or no edge lines). Unsealed shoulders It cannot be used on any pavement with average daily ESA > 1000 in the design lane in the year of opening. The seal must extend at least 200 mm beyond the delineated edge of the trafficked lane.

2.4.3 a) b)

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

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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 ten days 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 of service 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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33.1

CONSTRUCTION AND MAINTENANCE CONSIDERATIONSGeneral

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, thicknesses and/or other critical properties assumed in the design model may not be achieved and reduced pavement performance could be expected.

3.2

Unbound granular

Unbound granular pavements are particularly susceptible to damage caused by the infiltration of water resulting from: rain, water ponding and/or flooding during construction; water ponding and/or flooding during service; and lack of an adequate seal and/or drainage maintenance in service. Therefore: a) b) Projects including unbound granular material should be programmed such that construction of 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 is likely and existing construction protected from the infiltration of water. Contract provisions must allow for delays to construction caused by wet weather. the pavement layer(s) cannot be constructed and maintained at less than their degree-ofsaturation limits the subgrade cannot be constructed and maintained at the design modulus. have allowances for work ceasing during periods of wet weather establish clear responsibility and liability for infiltration of water during construction from sources including rain, surface and ground water flow, inundation/flooding, and transfer from new material with a high water content.

Unbound granular pavements must not be used where:

Contracts including the construction of unbound granular pavements must:

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. Rain events must be recorded daily to help determine the possible exposure of the pavement to water infiltration. Where water does infiltrate granular material, destructive testing is required to assess the extent and 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 the specified limits before overlying materials are placed.

3.3

Stabilised materials

Achieving the specified compaction standard in stabilised materials is essential for the development of the stiffness and fatigue characteristics assumed in design, particularly for the lower layers where maximum tensile stresses occur. To achieve the compaction standard, the maximum 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:20 January 2009



a) b)

application of a cement slurry (water/cement ratio 0.6 to 0.7), at a rate equivalent to 2 kg of cement per square metre immediately before laying subsequent layers placement of a prime and a seal with a large cover aggregate (> 14 mm) on top of the lower layer. The second and subsequent layers must not be stabilised with in situ stabilisation methods, even if the first layer is stabilised in situ. The first layer should be constructed to be as thick as possible (compacted thickness of at least 150 mm but not greater than 200 mm) to avoid damage to the lower layer when placing subsequent layers. Where it is not possible to place a thick first layer, consideration should be given to retarding the first layer and placing the second layer before the first layer has set.

Where multi-layer construction is used: a) b)

Multi-layer construction shall not be used for HILI pavements (the full thickness, between 150 mm and 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. under heavy traffic), temporary connections for HILI pavements must be, as a minimum, asphalt over cement 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 minimise this, a polymer modified binder seal must be provided beneath all asphalt surface layers in pavements 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 with minimum nominal size of 10 mm. At locations subject to heavy braking and/or tight cornering, such as 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 not mandated. If a seal is provided the spray rate should be reduced to 1.0 to 1.2 litres per square metre 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 mm nominal 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 ten calendar days and DG28 layers must not be left exposed for more than two calendar days. If this is unavoidable, a seal or minimum 50 mm DG14 layer should be placed to provide protection from moisture ingress.

3.6

Working platform

A working platform must be used for all HILI and ASt(A) pavements and is recommended for all other 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 is less 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) c)

a sound platform on which to construct the pavement layers protection to the subgrade for the life of the pavement.

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

3.7

Settlement

Neither this manual nor Part 2 of the Austroads guide include provisions to deal with settlement below the pavement layers. Where required, additional geotechnical investigations and assessments shall be carried out to determine if and how much settlement may occur. If settlement is likely, pre-treatment (e.g. drainage and/or surcharge of the formation) is required to reduce the extent 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 to maintain seals and drainage will cause, at least, loss of service life in most pavements and at worst, failure. Unbound granular pavements are particularly susceptible to loss of service life and failure 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 seals and drainage in a budget constrained environment, which could result in pavements that are not protected upon the onset of wet weather. Shrinkage of materials may generate cracks that will allow rapid entry of water.

b)

3.9

Trafficking of incomplete pavement

Pavement damage resulting from temporarily trafficking pavement layers below the final surface must 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 taken as the average least dimension (ALD) of the cover aggregate. If the ALD is not known at the time of design, the ALD can be estimated as 6 mm for 10 mm nominal size cover aggregate and 9 mm for 14 mm nominal size cover aggregate.

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44.1

ENVIRONMENTGeneral

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 performance of unbound granular pavements and subgrades. Water can also affect asphalt. Knowledge of environmental 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 of coastal Queensland is classified as having hot humid summers. Western areas have hot dry summers with either mild or cold winters. Further information on climate zones and climate averages 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 and Figure 4.3-2.

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

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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, introduced a method to study the climate synthetically, which combined rainfall and Potential Evapotranspiration (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 exactly balanced 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

MI =

100 ( s d ) PET

It follows that when rainfalls are lower than PET, MI is negative and the climate is dry. When rainfalls are higher than PET, the MI is positive and climate is wet. The climate classification based on 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 and Figure 4.3-2 shows that regions with a rainfall below 600 mm have a negative MI and hence are dry as the evapotranspiration exceeds the rainfall. Areas with an annual rainfall less than 500 mm are semi-arid.

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Table 4.3-1 Climatic types according to the total moisture index (MI)Symbol A B4 B3 B2 B1 C2 C1 D E Climatic type Very humid Humid Humid Humid Humid Sub-humid Sub-dry Semi-arid Dry MI Over 100 80 to100 60 to 80 40 to 60 20 to 40 0 to 20 -33 to -0 -66 to -33 -110 to -66

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

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4.44.4.1

Minimising exposure to and influence of waterGeneral

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) b) c) d) e) f) g) rain, particularly on unprotected and/or poorly maintained pavements inundation positive water head ponded water construction water inadequate subsurface drainage 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 and sub-surface drainage, etc.) depends not only on load intensity, material availability and industry capacity, but also on exposure to water during construction and service life. 4.4.2 a) b) Design requirements seal over the full width of the formation verge with low permeability and low swell on the high side of one-way cross-falls including at least an additional 100 m at either end from where the transition to a crowned pavement commences adequate surface drainage including i) table drains (when used) located well away from the formation (min. 5 m) in flat or lightly undulating country or excluding them altogether. Water should always be directed away from the formation or, if this is not possible, drains should be located at least 5 m away from the edge of the formation. edge drains on embankments and directing the concentrated outflows away from the formation via drains with impermeable lining full-width sealed formation and concrete channel in cuttings or, preferably for unbound granular pavements, providing table drains in cuttings. The following are required to reduce exposure to and influence of water:

c)

ii) iii) d)

cuttings Subsoil drains must be provided at all times. There may also be the need for a drainage layer to intercept water under positive head, break capillary rise and/or provide additional subsurface drainage to intercept ground water. In cuttings with rock floors a stabilised infill layer 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 water for the particular embankment material (untreated or treated) used, or a drainage/capillary break layer must be provided on top of the subgrade and above the level of the water table or standing water.

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The minimum embankment height where there is no inundation and/or standing water or water table, measured to the bottom of the lowest pavement layer at the outside edge, above the natural surface should be i) in regions with Thornthwaite Index 0 and rainfall > 500 mm/year, above the influence of any water, but not less than 200 mm from the natural ground to the underside of the lowest pavement layer In regions with Thornthwaite Index < 0, in particular for reactive subgrades where there is no cover to reactive subgrade provided, the thickness should be determined as a balance between keeping the pavement above water and minimising the potential for change in subgrade water content that could cause volume change. In such areas, the minimum height should be 100 mm, unless some unusual condition, such as a perched water table, irrigation, etc. is likely to exist. The slope of the edge of the pavement should be 25%.

ii)

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 and the effect on the pavement and subgrade determined. Where it is determined that a loss of service 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 that is less sensitive to water, such as a concrete pavement.

g) h) i) j)

Asphalt surface layers are not impermeable and must have a polymer modified seal immediately beneath them (refer Section 3.5). Pavement must be properly compacted right to its edge, and any excess, poorly compacted paving material beyond the seal edges is to be removed. kerbed pavements Subsoil drains must be provided at all times. 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 with different structures (i.e. layer types and/or layer thicknesses). For example, a longitudinal pavement drain is typically required when widening an existing pavement. The invert of a pavement drain must be lower than the underside of the lowest pavement layer, and where there is a working platform, the invert must also be lower than the underside of the working platform.

4.4.3

During construction

Good surface and subsurface drainage must be provided and maintained at all times. Surfaces must 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 nor some other form of positive protection is provided to the subgrade, reworking and/or delay must be factored into the construction program to overcome the effects of rain and/or inundation during construction. Asphalt and unbound granular materials are extremely susceptible to damage resulting from increased 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 plan28 January 2009



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 been standing and, if necessary, restricting the movement of traffic. Restrictions could include traffic limitations on the outside edge of the pavement, restricted loads and so on, until the pavement and subgrade have dried. This relaxation in design must not be applied to roads with average daily ESA > 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 a design 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 the Weighted Mean Annual Pavement Temperature (WMAPT) for the project location. The WMAPTs for 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 be completed 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 the lean mix concrete subbase. If this is not possible, a SAMI must be provided above the lean mix concrete subbase, prior to placing any asphalt, as wide shrinkage cracks may occur.

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55.1a) b) c) d) e) f) g)

SUBGRADEGeneralworking platform capping layer drainage layer select fill general fill treated in situ material natural unprocessed in situ material, other than that moved from another location and/or compacted.

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

In pavement thickness design calculations, fill and/or in situ untreated subgrade materials to a minimum 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 twoletter code to indicate soils classification (refer Appendix 1).

5.25.2.1 a) b)

Subgrade assessmentGeneral suitability of embankment material for the design and conformance to specifications suitability of in situ material for any necessary treatments and the subgrade design modulus to permit the design of the pavement.

The untreated subgrade has to be assessed for the following:

Testing of subgrade materials to determine design inputs shall be undertaken in the planning and design phase. Subgrade assessment can be made difficult by highly variable natural materials and changes to the subgrade material during construction. Accordingly, the subgrade materials must be reassessed immediately prior to pavement construction, in addition to any prior assessments. The pavement design as a whole must also be subsequently reassessed and amended to reflect any change. Where prior assessment has been adequate, few changes should be required. Allowances must be made in the construction contract for changes to the pavement design and changes to subgrade treatments during the construction phase. The requirements for subgrade testing prior to pavement construction also apply to temporary pavements. Subgrade samples shall be selected and tested for: a) b) c) d) e) plastic limit liquid limit in situ moisture content percent passing the AS 0.425 mm sieve weighted plasticity index (WPI), which is the plastic limit multiplied by the percent passing the AS 0.425 mm sieve

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f)

california bearing ratio (CBR) and swell determined at the density and moisture content as provided in Section 5.2.2.

The in situ untreated subgrade shall also be tested with a dynamic cone penetrometer (DCP). Where there is to be any subgrade stabilisation, the subgrade shall be tested in accordance with AS1289.4.2.1 Soil Chemical Tests Determination of the sulphate content of a natural soil and the sulphate content of the groundwater-Normal method. The soluble sulphate content shall not exceed 0.2%. Many extremely weathered and highly weathered rocks in Queensland (especially sedimentary rocks such as siltstone, mudstone and shale) tend to break down during construction to form moisture-sensitive silts and clays. For such s

Pavement Design Manual Jan 09

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