supplement to austroads guide

TS 10801:1.0 | Version 1.0 29 September 2021 Transport for NSW UNCONTROLLED WHEN PRINTED 1

Supplement to Austroads Guide TS 10801:1.0 – 29 September 2021 Supersedes: Nil

Supplement to Austroads Guide to Pavement Technology Part 5: Pavement Evaluation and Treatment Design Version 1.0

General Austroads has released the Guide to Pavement Technology, Part 5: Pavement Evaluation and Treatment Design and all road agencies across Australasia have agreed to adopt the Austroads Guides to provide a level of consistency and harmonisation across all jurisdictions. This agreement means that the new Austroads Guides and the Australian Standards, which are referenced in them, will become the primary technical references for use within the Agency. This supplement is issued to clarify, add to, or modify the Austroads Guide to Pavement Technology, Part 5: Pavement Evaluation and Treatment Design. Transport for NSW accepts the principles in the Austroads Guide to Pavement Technology, Part 5: Pavement Evaluation and Treatment Design with variations documented in this supplement under the following categories:

• Transport for NSW enhanced practice: Transport practices which enhance the Austroads Guides.

• Transport for NSW complementary material: Transport reference material that complements the Austroads Guides. These documents include Manuals, Technical Directions and/or other reference material and are to be read in conjunction with the Austroads Guides.

• Transport for NSW: Transport practices that depart from the Austroads Guides. For other associated supplements see Transport for NSW supplement to Austroads Guide to Pavement Technology, Part 2: Pavement Structural Design. Note: In this Supplement the Austroads Guide to Pavement Technology, Part 5: Pavement Evaluation and Treatment Design (2019) is referred to as the “Guide” and section numbering corresponds to the Guide. Variations to the Guide are detailed under the corresponding headings and Transport for NSW is referred to as Transport.

Supplement to Austroads Guide to Pavement Technology, Part 5: Pavement Evaluation and Treatment Design


About this release Title: Supplement to Austroads Guide to Pavement Technology, Part 5: Pavement Evaluation

and Treatment Design

Document Number: TS 10801:1.0

Branch/Section/Unit: Technical Services/Advanced Technical Services/Ground Engineering

Author: Pavement Manager (Flexible Pavements)

Contributors: Pavement Manager (Flexible Pavements), Pavement Manager (Rigid Pavements) Pavement Manager (Project Engineering), Pavement Manager (Asphalt Technology), Pavement Manager (Sprayed Seals), Pavement Manager (Pavement Performance)

Endorsed by: Director Ground Engineering

Approvals: Confer with Director of Advanced Technical Services

Approved by: Director of Advanced Technical Services

Date of Approval and Effect: 29 September 2021

For: Transport and pavement design consultants

Next Review Date: 2022

Keywords: pavement, base, subbase, subgrade, flexible, rigid, bound, asphalt, granular, concrete, maintenance, rehabilitation, design

Document history Version Date Reason for amendment Page No. Editor

1.0 October 2020 Initial document All PM(FP)



1. Introduction

Transport enhanced practice, complementary material, or departures This supplement is to be read in conjunction with the Transport supplement to Part 2 of the Austroads Guide to Pavement Technology and relevant specifications, technical directions and standard drawings related to pavement maintenance and construction. As defined in the Transport supplement to Part 2 of the Austroads Guide to Pavement Technology, heavy duty pavements are pavements with a design traffic loading ≥ 107 ESA in the design lane for the first 20 years of the design period.

2. Project Definition

Transport enhanced practice, complementary material, or departures

2.5 Acceptable Risk and Project Reliability

The mechanistic empirical procedure must be used for the design of all heavy duty pavement overlays and rehabilitation treatments. The minimum project reliability levels for rehabilitation projects involving heavy duty pavement overlays are listed in Table 1 of this Supplement. Table 1. Minimum project reliability levels for rehabilitation projects

Road Type Project Reliability (%)

Freeway, Motorway, Major Highway or other Heavy Duty Pavements 95

Other than above where Lane AADT > 2000 90

Other than above where Lane AADT < 2000 85

Traffic data for State roads can be obtained from the Transport Pavement Unit.

3. Pavement Data and Inspection


3.2 Historical Data

Some functional and structural data on the existing road network can be obtained from the Transport Road Asset Management System (RAMS). Contact the Transport Pavement Unit for advice on obtaining data.

3.2.4 Climatic Conditions Refer to Section 4 of the Transport Supplement to Part 2 of the Austroads Guide to Pavement Technology for more NSW climatic information. The laboratory CBR strength of the subgrade is to be assessed at:



• Soaked for 10 days for soils in higher annual rainfall areas (> 600 mm) or areas possibly subject to inundation, or

• Soaked for 4 days for drier climatic areas (annual rainfall < 600 mm).

3.3.2 Visual Condition Data Some pavement condition data on the existing road network can be obtained from the Transport Road Asset Management System (RAMS). Contact the Transport Pavement Unit for advice on obtaining data.

3.3.3 Other Site and Environment Information Geology, topography and climate Rocks and recycled material commonly available for roadwork in New South Wales include basalt, latite, dolerite, breccia, dacite, andesite, granite, rhyolite, syenite, sandstone, conglomerate, limestone, shale, chert, argillite, ironstone, laterite, river gravel, gneiss, quartzite, recycled concrete aggregate and slag. The order above is generally igneous (basic to acidic), sedimentary then metamorphic and finally recycled or manufactured. Basalt

Basalt is a fine grained igneous rock generally dark in colour. It is widely used and is usually hard, tough and dense. There are cases of secondary mineralisation such as in the Goulburn area which causes otherwise hard basalt to soften and break down over time. Basalt has little or no quartz content and when it is used in the wearing surface shows a tendency to polish which reduces resistance to skidding when the road is wet. Crushed basalt has performed well as a granular base when blended with a natural fine granular material such as decomposed granite and some sandstones. Weathered basalt has a high clay content and is not satisfactory for pavement construction. Latite

The Illawarra volcanic series occurs from Kiama to Port Kembla. It arises from a common magma which has been given the name of latite. It varies from basic basaltic rock to intermediate compositions. Polished friction values are at the lower end of the scale reflecting the quartz content. Thicker flows have a columnar structure and sometimes inferior zones of weathered overlying material or dyke intrusions are incorporated into the crushed product. The crusher dust from latite which weathers from blue to grey, has been used successfully as a soil conditioner with the more basic sources being most successful. Dolerite

Dolerite is a fine to medium grained basic igneous rock containing minerals similar to those in basalt. Prospect dolerite, which has a lighter colour than the associated basalt, was for many years a major source of aggregate in Sydney. However the lower layers are picrite containing weathered olivine which renders rock from this source unsuitable for roadworks. Breccia

There are several sources of volcanic breccia around Sydney. They occur in volcanic necks filled with non-igneous material including fragments of coal, shale, sandstone and other material derived from wall rocks. These breccias were used as a road base substitute for Prospect dolerite prior to full development of the Illawarra latite quarries. They were often modified with lime to improve their durability. Dacite and Andesite

These igneous rocks have an intermediate composition between basalt and granite. They frequently have large crystals and a grey or pink colour. Their skid resistance is good and they crush to a reasonable shape but often need fly ash to counteract alkali reactivity when used in concrete. Dacite and andesite quarries supply much of the rock in the Hunter Valley. Rhyodacite is used in the Holbrook area.



Granite

Granite is the principal coarse grained igneous rock. It is often classed as an acidic rock with a quartz content greater than 65%. It causes high wear in crushing plants and is not widely used for aggregate. It is susceptible to stripping from bitumen coatings. Gravels derived from weathered granite are used extensively in flexible pavement construction. Better quality gravels usually occur in thin layers which require restoration of large areas. Some granite gravels which contain a high clay or mica content should not be used. Rhyolite

Rhyolite is a fine grained to glassy igneous rock with a similar chemical composition to granite. South Coast rhyolites are glassy. The polishing characteristics of rhyolite vary from good to poor according to the location and source. One source from the Hunter Valley (Gosforth) has been widely used in asphalt surfacing for skid resistance. Additional binder is needed to compensate for the absorption of the more skid resistant rhyolite aggregates. Syenite

Syenite is a highly absorptive lighter coloured rock of igneous origin with little or no quartz. It occurs in the Mittagong area and has been used as a concrete aggregate. Thermal expansion up to ten times greater than less absorptive rocks can occur. Sandstone

Sandstone is a variable sedimentary rock composed of coarse grains of sand cemented together by calcium carbonate, iron oxide, silica or clay. The sandstone group of rocks includes siltstone, conglomerate and greywacke depending on the grain size of the fragments. The granular composition and different cementing materials mean that variable strengths can occur. Crushed sandstone is generally suitable as a selected formation material under pavements but may require the top 150 mm to be modified and sealed to achieve volumetric stability and avoid loss of compaction at the interface. It has also performed well as a subbase in lightly trafficked roads provided the 10% fines assessment is satisfied. Sandstone breaks down rapidly to sand when compacted at moisture contents greater than 90% of optimum. Some sandstone can be fine grained (eg Banks Wall sandstone) and difficult to compact when broken down, stabilisation may be necessary where used as a selected material. Conglomerate

Conglomerate consists of rounded and water eroded material of different sizes ranging from pebbles to cobbles embedded in a matrix of finer material which is mainly sand. Conglomerate usually consists of the erosion resistant varieties of minerals and rocks, often siliceous pebbles, which may have travelled some distance from their original source. Conglomerate from stream banks has been used on black soil sections of the Newell Highway north of Narrabri where the source is the Kaputar Range. Careful selection and often modification of this material is necessary, as the material has a clay matrix from its basalt source. Conglomerate was for many years a major source of road gravel in the Upper Hunter Valley to as far north as Willow Tree. Limestone

Limestone varies from marble through to limestone nodules, called calcrete, which are found in gravels west of Balranald in the mallee areas. Major deposits with clay sericite (decomposed mica) seams occur between Lithgow and Mudgee. Limestone has the benefit of some natural cementation and when finely ground may be used as filler in asphalt but usually at higher percentages than the more reactive lime. Calcereous gravels perform well as lightly bound granular materials. Lime has a natural affinity for bitumen.



Limestone aggregate is generally not used for surface course applications due to its low skid resistance but is occasionally used for delineation on shoulders. A feature of limestone gravels and lime stabilised gravels is their ability to absorb moisture. However, once instability occurs, drying back to increase strength is necessary prior to trafficking. Shale

This is the principal member of a group of soft rocks. Other rocks in this group include mudstone, phyllite, slate and mica schist. These are usually harder than shale. It is critical when considering the use of shale and other soft rocks that the amount of weathering that is likely to occur is assessed by accelerated weathering tests in a laboratory. Other testing is to be carried out on material which has been pre-treated by accelerated laboratory weathering. In view of material breakdown over time, sources such as Wianamatta shale in the Sydney basin are unsuitable for pavement layers and selected formation material. Other sources have been modified with lime to slow the rate of breakdown and used in lower pavement support layers. Chert

Groundwater, percolating through shales, gives rise to silica replacement forming chert. Hard cherts have performed well as granular pavement materials on the Far North Coast of NSW showing some natural siliceous cementing. Argillite

Argillite is an intermediate metamorphic state in the hardening of shales to slates. It is a rock source of marginal hardness used as an aggregate on the North Coast of NSW for skid resistance in lieu of basalt. It is also an important source of crushed road base, especially when blended with finer granular material. Ironstone and Laterite

In sandstone and sandy loam oxides of iron (ironstone), iron and aluminium (laterite) often leach to the surface and cement as nodules with quartz and sandstone clay minerals. These materials because of their natural siliceous cementing when placed with a macadam grading have performed well in a granular pavement. Although with their rounded shape, the material suffers minor surface rutting under high truck tyre pressures. They also tend to corrugate when used on unsealed roads. The disadvantage is that their recovery disturbs large surface areas and retention of existing materials is a valuable resource. River Gravel

Extensive deposits of river gravel occur along major rivers in NSW. They formed a major source of rock in Sydney from the Emu Plains quarries. River gravels were a driving force in the move to concrete pavements in the granite areas of southern NSW near the Murrumbidgee River. However, with river protection, direct dragline extraction has been replaced by extraction from former river beds where clay is often a contaminant. The sources are now primarily used for natural sand supplies. Whilst river gravels consist of a range of rocks, quartz usually predominates as quartzite with other metamorphic rocks surviving as round water worn pebbles and cobbles. There are usually a small percentage of softer rocks which break down under truck tyre pressures. Consequently, river gravels are not used as sealing aggregates on heavily trafficked roads. Unless pre-screening is undertaken, crushed river gravel may have inadequate crushed faces for rut resistance in asphalt and compressive strength in concrete, especially where large cobbles are not available. When used as an aggregate, river gravel has good skid resistance because of its quartz content except where the gravel has a basalt source as occurs on the North Coast. Prior Stream Gravels

Prior stream gravels are a name given to fine river gravels west of the Great Dividing Range. They tend to become finer and sparser as the distance from the Great Dividing Range increases. In black soil areas, they are often the only local source of gravel. In these locations, the gravel is actually a clayey or silty



sand. These gravels have relatively poor shear strength. Granular stabilisation with hard rock or modification may be necessary for effective use of this material. Gneiss

Gneiss is a foliated metamorphic rock having a mineral composition similar to granite and containing alternate layers or bands of mica and granular ‘eyes’ that are granite like in texture and composition. Gneiss aggregates tend to shear along the mica layers when used in bituminous sealing. Deposits of these materials are found and used in Western New South Wales. Quartzite

Quartzite is a hardened or metamorphosed sandstone. It crushes to a hard angular rock which usually requires addition of fines with some cohesion to perform as a pavement material. Quartzite has low skid resistance due to the coarse crystalline nature and has a tendency to strip from bitumen. There is no secondary cementation. Clay

Clay is material finer than 2 microns (as compared to fine silt which is between 2 and 20 microns) which provides cohesion, even when mixed with other materials in small quantities, and plasticity. There are three primary groups of clays.

• Smectites (includes montmorillonite and bentonite) which have multilayered plate like structures up 500 times wider than their thickness and are the most expansive. Expansion is related to free potassium and sodium ions taking up to five times their volume in water.

• Illites are clays with intermediate expansion.

• Kaolinites (includes potting clay) are the least expansive, typically about one tenth as reactive as smectites and are characterised by relatively high free calcium ions.

In general, expansive clays are produced in the weathering products of basic rocks such as basalts and less expansive clays in acidic rocks such as granite although mica and feldspars are ferromagnesian minerals which occur in granites. Slag

Blast furnace slag occurs either as “skulls” or a crushed product. It performs well as a free draining pavement material with self-cementing properties because of the presence of free lime. A water quenched granular form which is the source for ground slag binder can also be produced. Blast furnace slag has only marginal rock strength but performs well as a thick bound pavement layer. As aggregate, it has a low polishing value. Another form of slag is steel slag which is a heavy, hard rock produced in a steel furnace. Steel slag, where vesicular, generally has good polishing resistance and an affinity for bitumen. This type of slag needs to be stockpiled for several months to avoid expansive lime reactions, expansive magnesium oxide reactions may not be prevented by stockpiling and its use in pavement material is subject to restrictions. Recycled Construction Materials

Transport specifications allow recycled construction materials with limitations on foreign material such as timber, steel, plaster and plastic. Suppliers need to have a sufficient area to stockpile various classes of recycled construction material. Waste materials must comply with NSW Environment Protection Authority (EPA) resource exemptions before use. Recycled concrete often lacks fines, has little cohesion and is difficult to work. This can be overcome in granular pavement material by blending with recycled asphalt pavement (RAP). Crushed brick and RAP blends have also been successfully used as selected formation materials.



4. Investigative Testing on the Pavement Surface


4.6 Skid Resistance

Surface treatment options for improving skid resistance of various pavement surfacing types are detailed in Technical Direction PTD 2013/004. While diamond grinding is usually specified for concrete pavements, it may also be applicable for aged asphalt pavement surfaces where the binder is sufficiently hard to not allow the narrow and short fins to collapse. The default blade spacing of 2.5 mm detailed in specification R93 is applicable for dense graded asphalt.

4.8 Use of Ground Penetrating Radar

Ground penetrating radar (GPR) surveys must be calibrated to the actual pavement layer profile by a subsequent field investigation (pavement cores or test pits) targeting areas of change in the GPR data.

4.9.2 Methods of Testing The location and load level for Falling Weight Deflectometer (FWD) testing must be specified to suit the rehabilitation design application. Particular care is required in defining the location of tests and arrangement of geophones in relation to joints and cracks when assessing deflections in rigid pavements. While a 40kN load is required for use with granular overlay design charts, heavier loads may be appropriate to generate a better bowl shape for back calculation purposes on stiffer pavements. Transport Test Methods T160, T191, T177 and specifications R925 and R425 are relevant to surface deflection testing by Benkelman Beam, pavement deflection and curvature by Deflectograph and pavement deflection by FWD. However these are written for specific purposes and require modification to be applicable for the collection of data for pavement rehabilitation design. When analysing Benkelman beam data it should be noted that the testing procedure is slightly different when using automated data collection as opposed to manual data collection and the derivation of the maximum deflection from the raw data is different. The designer should review the raw data to ensure that it has been analysed appropriately as a misinterpretation will result in erroneous overlay design.

4.9.3 Selection of Test Sites The location of FWD tests for use with the Mechanistic Empirical Procedure (MEP) must be planned to coincide with known pavement layer thickness and material types previously determined by a pavement investigation (pavement cores or test pits). Typical FWD spacing on a 2 lane 2 way road would be at 25m intervals alternating between the inner and outer wheel paths for each lane. GPR surveys can be useful to identify areas of variable pavement layers, which are typical in urban areas, and where previous patching has been undertaken. FWD testing must target areas of variable thickness and the back calculation modelling must be undertaken so that the FWD deflections are correctly aligned with the different pavement profiles determined from pavement investigations and GPR.

4.10 Surface Deflection of Rigid Pavements

Assess deflections for load transfer efficiency assessment and deflections for mean deflection and differential deflection calculations for asphalt overlay design by FWD with 40kN load at rigid pavement joints and cracks in the outer wheelpath of the heaviest trafficked lane. Plan the testing to ensure the results are not influenced by passing traffic. When locating the FWD, ensure the plate is as close to the crack or joint as possible but is not in contact with slabs on both sides of the joint or crack.



Assess deflections for voids at slab corners by FWD.

5. Pavement Composition and Subgrade Characteristics


5.3 Pavement Pits and Trenches

Unless specified otherwise in the project brief, pit, trench or core sampling is to be undertaken for rehabilitation investigation at a maximum spacing of 250 m or more frequently as required if the material properties change along the project length. The frequency of sampling needs to be assessed based on the scope of works, the level of traffic and accessibility. The depth should be adequate for the full pavement profile including the subgrade type. Typically the subgrade is tested to a depth of one metre from the underside of pavement. Dynamic Cone Penetrometer (DCP) testing is to be carried out at the underside of the pavement layers wherever practical. Sample sufficient quantities of each discrete pavement layer and subgrade to be able to categorise each discrete material and conduct appropriate testing for pavement design. The investigation is to include a check of transverse pavement variability. Pavement boxing, individual lane treatments and shoulder widening need to be identified for consideration in the rehabilitation design.

5.4 Insitu CBR from DCP Testing

Insitu DCP testing is to be undertaken in accordance with T161 – Penetration of a soil (Dynamic cone penetrometer - 9 Kg mass). An estimation of subgrade CBR of existing roads by means of Benkelman Beam deflection testing may be made using the following process. This approach is only applicable for unbound granular pavements with thin bituminous surfacing. Provided Benkelman Beam testing is carried out during the appropriate season (representative of equilibrium conditions or worst conditions where potentially affected by climatic conditions such as flooding) and on similar subgrades, the deflection response can be used to estimate the subgrade CBR by using the following approach. A measure of the deflection profile of the pavement under the Benkelman Beam is needed to estimate the subgrade stiffness. From the deflection profile, a pavement spreadability term can be determined as follows:

Sp = 100(d0 + d2 + d3)/(3d0) 1

Where

Sp = Spreadability (%)

d0 = Maximum rebound deflection

d2 = Rebound deflection at 600 mm

d3 = Rebound deflection at 900 mm

At each measurement point a subgrade CBR value is determined from Figure 1 below.



Figure 1. Indirect determination of CBR values

The CBR values should be analysed statistically to determine the appropriate percentile value using equation 2.

CBR = Mean CBR - f × s 2

f = value from section 9.6.2 of this supplement

s = standard deviation

It should be noted that this method will generally lead to conservative values for the insitu CBR at the time of testing and should be supplemented with testing that gives direct measurement of the subgrade conditions.

7. Selection of Treatments for Flexible Pavements


7.3 Treatments to Improve Drainage Additional requirements are included in the Transport Standard Pavement Subsurface Drainage standard drawings, technical guides and construction specifications.



Site investigations for groundwater, seepage and drainage conditions should be undertaken during the wetter months as these flows may be seasonal. If the site investigations occur outside the wettest period and seepage observations are inconclusive, additional subsurface drains may need to be installed in high risk areas as a precautionary measure. Boxed pavements are not to be constructed without appropriate subsurface drainage treatment. Boxed pavements may also occur through the provision of impermeable verge material or through pavement widening or patching with impermeable materials.

7.4.2 Sprayed Seals Additional requirements for sprayed sealing are included in Transport Form 395K and sprayed seal specifications. Only 10 mm nominal size aggregate and scrap rubber modified bitumen is to be used in strain alleviating membrane interlayers (SAMIs) and the use of GRS and FRS is not recommended in SAMIs. Do not apply a SAMI under asphalt wearing courses. Slow setting emulsions and highly cutback bitumen (between 20 - 50 % cutter oil) are to be used for surface enrichment.

7.4.3 Holding Actions Additional requirements for crack and joint sealing are included in the Transport specifications M211 and M214.

7.4.4 Asphalt Work Additional requirements are included in the Transport Asphalt Maintenance standard drawings and asphalt construction specifications. Figure 7.12 of the Guide shows an example of the effect of asphalt overlay thickness on roughness. The typical minimum thickness of asphalt over bound subbase is 175 mm to minimise reflective cracking from shrinkage cracks. Increases in asphalt thickness or alternative/additional treatments may be required if the cracking is wider than shrinkage cracks. Additional requirements for cold milling and subsequent overlay work are included in Transport specification R101.

7.5.1 Introduction The Transport supplement to Part 2 of the Austroads Guide to Pavement Technology notes that the minimum structural shoulder width for flexible pavements is 0.5 m if no kerb and gutter is present, except for granular pavements with a thin surfacing where the minimum width is 1.0 m. Unless funding is limited for the project, the strengthening of pavement layers should include the widening of shoulder structural pavements widths.

7.5.2 Heavy Patching Additional requirements (material and asphalt layer thickness limits) are included in Transport specification M250.

7.5.3 Granular Overlay Avoid placing a granular pavement over a bound layer which forms part of the pavement. The granular material may be intended to bridge reflective cracking from the bound layer but results in an “upside down pavement”. An upside down pavement is considered to be a high risk treatment in moderate to wet climates unless the following limitations are observed:

• Positive drainage of pavement is provided

• Full width pavement and a well maintained seal is adopted

• Design traffic loading < 106 ESA.



These limitations exist as moisture entering the granular base may be held in the granular layer through the permeability reversal of the pavement structure. Additional requirements are included in the Transport specifications M290, R71, 3051.

7.5.6 Insitu Stabilisation of Granular Pavements Additional requirements for stabilisation are included in the Transport specifications M290, R71, R75, 3051 and 3211.

7.5.8 Cement and Cementitious Stabilisation Binders used to create cementitiously bound materials by stabilisation must be slow setting binders as defined in accordance with test method T147. Unless used as a working platform, granular pavements less than 400 mm thick should not be stiffened by cementitious stabilisation unless on a subgrade greater than CBR 5%. Cementitiously bound pavements should not be considered over soft subgrades (CBR <2%) or expansive subgrades (swell >2.5%) unless there is a minimum of 1 m of cover to the finished surface level. Deflection testing prior to stabilisation allows soft areas of an otherwise suitable pavement to be identified for separate treatment. Additional requirements for stabilised pavement mix design and construction are included in specifications M290, R75 and R73. Stabilisation in multiple layers for a pavement course is not permitted. While plant mix courses are limited to a maximum of 250 mm placed in one layer, deep lift insitu stabilised courses may exceed this thickness with an allowance for a reduction in compaction in the lower portion of the layer. Deep lift insitu stabilised courses in excess of 300 mm and constructed in accordance with specification R75 are to be modelled with a reduced modulus in the lower third of the layer. In this case model the upper layer (two thirds thick) with E = 5000 MPa, K = 263, rough lower interface and the lower layer (one third thick) with E = 3200 MPa, K = 312 and rough lower interface. The fatigue of each of these layers is considered in determining the life of the entire insitu stabilised course by considering the post cracking phase of the lower third until the upper two thirds has also fatigued. Analysis is in accordance with Austroads Guide to Pavement Technology Part 2 equation 52 however the second phase is relevant to the top two third layer of bound material instead of the asphalt layer.

7.5.10 Bitumen Stabilisation Additional requirements for the use of foamed bitumen stabilisation are included in Transport Technical Direction PTD 2015/001 and specification R76 and R74. Bitumen stabilisation must only be by foamed bitumen in accordance with specification R76 and R74.

7.7.5 New Pavement Abutting an Existing Pavement Where a new pavement is constructed adjacent to an existing pavement with a different structure (either the pavement materials vary or course thicknesses vary by more than 50 mm) construct a No Fines Concrete (NFC) interface drain wrapped in geotextile with a suitable outlet to ensure drainage. For asphalt details to tie into existing pavements refer to the Transport Asphalt Maintenance standard drawings.

7.7.7 Shoulder Sealing Refer to the Transport supplement to Part 2 of the Austroads Guide to Pavement Technology for design requirements for structural and sealed shoulders.

7.7.10 Risk, Design Sensitivity, Construction Tolerances and Degree of Control A minimum construction tolerance of 10 mm is to be applied to the design thickness of the critical layer of pavements designed for 20 or more years.



8. Treatment for Rigid Pavements


8.1 Introduction For rigid pavement maintenance treatments refer to the Transport Rigid Pavement Maintenance standard drawings and maintenance specifications.

8.4.3 Grinding/profiling Additional requirements are included in the Transport Technical Guide P-G-003 ‘Grinding Concrete Pavements’. Where grinding is used to address roughness caused by voids under slabs, the grinding must be undertaken in combination with slab jacking.

9. Empirical Design of Granular Overlays for Flexible Pavements


9.1 Introduction For designs of 20 years or more, a minimum construction tolerance of 10 mm is to be applied to the design thickness derived from the procedure outlined in section 9. When nominating a test method to determine pavement deflections, ensure the test method nominates the appropriate tyre pressure and/or load plate configuration for the empirical method.

9.2.2 Adjustment of Deflections to Account for Seasonal Moisture Variations When assessing an appropriate seasonal moisture correction factor, give consideration to the following:

• Existence of pavement subsurface drainage system

• Width of sealed shoulders

• Influence of moisture ingress and moisture variation under the outer wheelpath.

9.2.5 Selection of Homogeneous Sections Use the cumulative difference approach (CDA method defined in Appendix D of the Guide) to identify homogeneous sections. When assessing whether an individual change in slope represents a homogeneous section boundary, consideration needs to be given to the significance of the change in relation to adjacent points. An individual change in the Z-value plot is to be considered as a homogenous section boundary (or boarder) when it is determined to be ‘significant’. A significant boundary is considered to occur when the individual Z-value is the most extreme (minimum or maximum) of 7 values either side of the potential boundary, i.e. if Zx is the maximum value in the range {Zx-7 to Zx+7} or Zx is the minimum value in the range {Zx-7 to Zx+7} then it is considered to be a homogeneous section boundary.



After applying the CDA method, verify that the results are rational by considering whether the homogeneous sections; are not less than 100m in length; coincide with geotechnical and GPR results (where GPR survey was undertaken); each have a Coefficient of Variation (CoV) not exceeding 0.25. Where the rehabilitation treatment includes a heavy patching treatment in addition to an overlay, eliminate the deflection points that coincide with the areas of heavy patching when determining homogeneous sections for the design of the overlay. From an economic perspective there is a limitation on a practical area of heavy patching included in the maintenance strategy. If the proportion of heavy patching becomes excessive then reconstruction should be considered. Where marked differences in deflections exist between inner and outer wheelpaths, consideration should be given to designing for the worst wheelpath only as combining them will moderate the design thickness for the worst wheelpath. For construction efficiencies short lengths of different pavement profiles designed for each homogeneous section are not acceptable, one treatment applied to the whole rehab area is preferable. Typically a minimum length of 500 m is required except where specific site constraints exist such as; intersections with traffic constraints due to road occupancy licence limitations; immovable utilities; short sites.

9.2.6 Calculation of Characteristic Deflections For empirical overlay design the values of ‘ƒ’ for heavy duty pavements and rural highways without heavy duty pavements are given in the following table: Table 2. Calculation of Characteristic Deflections

Number of deflection measurements

ƒ (heavy duty pavements)

10 1.83

12 1.79

14 1.77

16 1.75

19 1.73

24 1.71

≥ 30 1.69

For other roads refer to the definition and recommended values provided in table 9.3 in the Guide. For MEP rehabilitation design use values from Table 9.3 of the Guide or alternatively, where sufficient test results are available to establish that the distribution fits a distribution type other than a normal distribution then f values may be used to suit the actual distribution.



10. Mechanistic-empirical Procedure of Designing Strengthening Treatments for Flexible Pavements


10.1 Introduction The MEP for rehabilitation design must be used for granular overlays where the design traffic loading exceeds 107 ESA. Where the MEP uses the same procedures as that set out in the Austroads Guide to Pavement Technology Part 2, the respective requirements included in the Transport supplement to Part 2 of the Austroads Guide to Pavement Technology also apply. Where only deflectograph deflection data is available and the design period doesn’t exceed 20 years or the design traffic loading does not exceed 107 ESA, an asphalt overlay may be designed in accordance with the empirical method from Austroads Guide to Pavement Technology Part 5 edition 3 (2011) Sections 6.2.11 and 6.2.13. There are several back-calculation computer programs available that perform this procedure in an automatic way. Nevertheless, there are several characteristics and limitations common to these types of program. These limitations are briefly discussed as follows:

(a) Seed modulus - Due to the iterative nature of the process it is possible to converge on an incorrect solution if the seed moduli are not representative of the material and strength state that it is in at the time of testing. Care needs to be taken in selecting appropriate seed values

(b) Modulus range - In some of the back-calculation programs, a range (minimum and maximum) of moduli are nominated, selected or calculated to prevent program convergence to unreasonable moduli levels (too high or too low). Care needs to be taken in selecting limits where they are nominated by the user as the use of selected values can cause the analysis to converge on an unrealistic result.

(c) Layer thickness - Stiffness results from back-analysis are extremely sensitive to the layer thicknesses assumed for the analysis. Where coring shows a range of thicknesses greater than ±5% of the mean thickness and there is no other information to indicate where changes in pavement thickness occur, a GPR survey is suggested. In some instances further coring might also be considered.

(d) Thin layers - A common back-calculation difficulty is the impossibility to estimate pavement moduli of layers that are less than 50 mm thick. When these thin layers exist at the pavement surface it is recommended to combine the first layer with the second if it has similar materials.

10.2 Mechanistic-empirical Procedure Note that the MEP doesn’t consider the fatigue life of existing bound materials (refer to section 10.10.1 of the Guide) and existing cracked materials may require removal and replacement to prevent reflective cracking in an overlying treatment.

10.4 Selection of Homogeneous Sub-sections Where the assessment is based on a continuous pavement deflection survey, the project area must be divided into homogeneous sections in accordance with section 9.2 of the Guide. Analysing non-homogeneous sections tends to skew the characteristic values as the standard deviation increases in non-homogeneous sections.



Where marked differences in deflections exist between inner and outer wheelpaths, consideration should be given to designing on the worst wheelpath as combining them will moderate the design thickness. Excluding areas of high deflection from the data on the basis that they will be heavy patched may allow the identification of homogeneous sections where the rehabilitation strategy involves a combination of heavy patching and an overlay. From an economic perspective there is a limitation on a practical area of heavy patching included in the maintenance strategy. If the proportion of heavy patching becomes excessive then reconstruction should be considered.

10.5.2 Selection of Deflection Bowls for Modulus Back-calculation When identifying representative deflection bowls for use in the MEP design, determine the CD using ‘ƒ’ in accordance with Table 6.3 of the Guide. Where there is sufficient deflection data collected in a homogeneous section to establish that the distribution of D0 is different to a normal distribution, an alternative distribution can be used. In this case, determine the CD that defines the 90th percentile D0 (i.e. 10% of values exceed this value) for the actual data distribution type determined to apply to the D0 data set. Where a heavy patch strategy is included as part of the rehabilitation design, exclude the deflection bowls with the highest D0’s that would be treated by heavy patching from the analysis in the same proportion as the percent area of heavy patching when designing the other treatment. Use the three bowls with D0 closest to the CD of the homogeneous section to represent the homogeneous section. Exclude any of these three bowls that have a D0 outside the range ±10% of the CD. The average back-calculated moduli determined from these bowls for each layer is the moduli representative of each layer within that homogeneous section at the time of testing before correction for environmental factors. When undertaking the MEP, a geotechnical investigation must be undertaken with sufficient scope and accuracy to determine the thickness of each layer within each homogeneous section. As a minimum:

• Bound material is to be cored

• Unbound granular and subgrade materials are to be test pitted

• DCP testing is to be conducted to 1000 mm below pavement level.

10.5.3 Pavement and Subgrade Configuration For uncracked asphalt wearing courses less than 75 mm thick on a granular base, constrain the asphalt modulus in the back calculation model to the modulus of new asphalt adjusted by the MRF and for the pavement surface temperature at the time of testing.

10.7.2 Subgrade Limit the subgrade design modulus to be no greater than 10 times the soaked CBR when designing treatments for 20 or more years. The soak period for laboratory CBR testing is defined in the following table: Table 3. Soak period for laboratory CBR testing

Medium annual rainfall (mm)

Specimen compaction moisture content

Testing condition

Excellent to good drainage Fair to poor drainage

<600 OMC Unsoaked 4-day soak

600 – 800 OMC 4-day soak 10-day soak

>800 OMC 10-day soak 10-day soak



10.7.3 Selected Subgrade and Lime-stabilised Subgrade The design CBR value assigned to a selected material for use in step 1 of Section 10.7.3 of the Guide is the lesser of the 4-day soaked CBR value and the insitu CBR derived from DCP testing.

10.7.4 Unbound and Modified Granular Materials The design modulus of granular material (unbound and not modified) is limited to a maximum of 350MPa, or 450MPa where it is known from construction records that the material is Class 1 DGB.

10.7.5 Asphalt Consideration needs to be given to the pavement surface temperature at the time of deflection testing and diurnal effects in relation to the modulus adjustment applied to lower layers in thick asphalt pavements. In the absence of reliable historical Traffic Load Distribution (TLD) data use the following presumptive ESA/HVAG values to calculate the past traffic in ESAs; rural 0.9; urban 0.7. In addition to the procedure used to calculate the design modulus of existing asphalt for use in Section 10.10, where the existing asphalt is not fatigue cracked, the design modulus must not exceed the temperature-adjusted back-calculated modulus multiplied by the MRF (Equation 16) calculated using the traffic ratio. Additional requirements of the Transport supplement to Part 2 of the Austroads Guide to Pavement Technology apply when calculating the modulus of asphalt for use as the design modulus for new pavements in this section of the Guide.

10.7.6 Cemented Material and Lean-mix Concrete In the absence of reliable historical TLD data use the following presumptive ESA/HVAG values to calculate the past traffic in ESA’s; rural 0.9; urban 0.7. In addition to the procedure used to calculate the design modulus of existing cemented material for use in Section 10.10, where the existing material is not fatigue cracked, the design modulus must not exceed the back-calculated modulus multiplied by the MRF (Equation 16) calculated using the traffic ratio. Additional requirements of the Transport supplement to Part 2 of the Austroads Guide to Pavement Technology apply when calculating the modulus of cemented material for use as the design modulus for new pavements for use in this section of the Guide.

10.7.7 Foamed Bitumen In the absence of reliable historical TLD data use the following presumptive ESA/HVAG values to calculate the past traffic in ESA’s; rural 0.9; urban 0.7. In addition to the procedure used to calculate the design modulus of existing foamed bitumen for use in Section 10.10, where the existing foamed bitumen is not fatigue cracked, the design modulus must not exceed the temperature-adjusted back-calculated modulus multiplied by the MRF (Equation 16) calculated using the traffic ratio. Additional requirements of the Transport supplement to Part 2 of the Austroads Guide to Pavement Technology apply when calculating the modulus of Foamed bitumen material for use as the design modulus for new pavements in this section of the Guide.

10.8 Procedures for Determining Critical Strains

Calculate strains for use in the forward mechanistic-empirical design procedure using the computer program CIRCLY (version 5.0 or later).

10.10.1 Introduction In addition to the MEP design process, consideration must be given to potential reflective cracking of the rehabilitation treatment from any bound materials retained in the existing pavement.



The rehabilitation treatment profile selected for assessment must conform to any material and construction requirement set out in Transport specifications and standards.

13. Economic Comparison of Alternative Treatments


13.2 Method for Economic Comparison The present worth of costs method is the preferred option. It effectively allows both uniform series and sporadic events (which are applied through the life of the pavement) to be simultaneously accommodated in the analysis.

13.3.3 Salvage Value Transport favours a nil residual benefit or salvage value for roads at the end of the analysis period (unless the plan for a particular option is to have rehabilitation or reconstruction through the period). However certain long lasting pavements would still be functional after 40 years (or even have substantial value as suitable to take an overlay). These pavements should be assigned a residual value in the analysis but not more than 25 % of the initial construction cost.

13.3.4 Real Discount Rate Based on the Principles and Guidelines for Economic Appraisal of Transport Investment and Initiatives – Transport Economic Appraisal Guidelines, the analysis must be carried out using a central real discount rate of 7 %, with sensitivity tests performed at 4 % and 10 %.

13.3.5 Analysis Period For heavy duty pavements, an analysis period of 40 years from the year of opening to traffic should be used.

13.4 Road user costs

Road users costs are not applied for pavement costs comparisons unless specified in the project brief.



11. References Guides Guide to Pavement Technology, Part 5: Pavement Evaluation and Treatment Design (2019) Austroads Guide to Pavement Technology, Part 2: Pavement Structural Design (2017) Austroads P G 001 Standard Pavement Subsurface Drainage Details, NSW Roads and Maritime Services P G 003 Grinding Concrete Pavements, NSW Roads and Maritime Services Principles and Guidelines for Economic Appraisal of Transport Investment and Initiatives – Transport Economic Appraisal Guidelines, Transport for NSW TPP 07 5 NSW Government Guidelines for Economic Appraisal, 2007, NSW Treasury. Transport specifications IC-QA-R71 Unbound and Modified Pavement Course IC-QA-R73 Construction of Plant Mixed Heavily Bound Pavement Course IC-QA-R75 Insitu Pavement Stabilisation Using Slow Setting Binders IC-QA-R76 Insitu Pavement Stabilisation Using Foamed Bitumen IC-QA-R93 Diamond Grinding Of Concrete Pavement IC QA R101 Cold Milling Of Road Pavement Materials IC QA R425 Measurement of Deflection by Falling Weight Deflectometer IC-QA-R925 Measurement of Deflection by Falling Weight Deflectometer IC QA 3051 Granular Base and Subbase Materials for Surfaced Road Pavements

IC-QA-M211 Crack Sealing Bituminous Surfaces IC-QA-M214 Repair of Joint Seals in Concrete Pavement IC QA-M250 Heavy Patching (Flexible Pavement)

IC QA-M290 Pavement Rebuilding (Bound and Unbound Material). Test Methods T147 Working time for road construction materials (Blended in the laboratory with slow setting binders) T160 Deflection Measurement (Portable Beam) T161 Penetration Resistance of a Soil (Dynamic Cone Penetrometer - 9 Kg Mass) T177 Pavement Deflection Measurement (Falling Weight Deflectometer) T191 Determination of Deflection and Curvature by Deflectograph.

Pavement standard drawings Standard Pavement Subsurface Drainage Details

Asphalt, Volume 2 - Maintenance

Rigid Pavement, Volume MP - Plain Concrete Pavement

Rigid Pavement, Volume MC - Continuously Reinforced Concrete Pavement

Rigid Pavement, Volume MP – Jointed Reinforced Concrete Pavement.



Technical directions and supplements Supplement to Austroads Guide to Pavement Technology Part 2:Pavement Structural Design

PTD 2013/004 Selection of Surface Treatments to Improve Skid Resistance

PTD 2015/001 Foamed Bitumen Stabilisation

Contact Us: If you have any questions or would like more information on this document, please contact Transport for NSW:

roads-waterways.transport.nsw.gov.au

September 2021 TS 10801:1.0

[email protected]

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