ROAD SECTOR DEVELOPMENT PROGRAMME PACKAGE 3 PAVEMENT DESIGN SUPPLEMENT: PART II REHABILITATION AND RECYCLING OF FLEXIBLE PAVEMENTS

Transcription

1 PROGRAMME PACKAGE 3 PAVEMENT DESIGN SUPPLEMENT: PART II REHABILITATION AND RECYCLING OF FLEXIBLE PAVEMENTS

2 PROGRAMME PACKAGE 3 PAVEMENT DESIGN SUPPLEMENT: PART II REHABILITATION AND RECYCLING OF FLEXIBLE PAVEMENTS INDONESIA INFRASTRUCTURE INITIATIVE May 2011

3 INDONESIA INFRASTRUCTURE INITIATIVE This document has been published by the Indonesia Infrastructure Initiative (IndII), an Australian Government funded project designed to promote economic growth in Indonesia by enhancing the relevance, quality and quantum of infrastructure investment. The views expressed in this report do not necessarily reflect the views of the Australia Indonesia Partnership or the Australian Government. Please direct any comments or questions to the IndII Director, tel. +62 (21) , fax +62 (21) Website: ACKNOWLEDGEMENTS This report has been prepared by Geoff Jameson and Edward James on behalf of Cardno Emerging Markets in association with the Australian Road Research Board who were engaged under the Indonesia Infrastructure Initiative (IndII), funded by AusAID, as part of the Directorate General of Highways (DGH) Programme Development Activity. This supplement rests on the work of the Activity 201 group and previous documents delivered under Activity 201, notably Deliverable 2: National roads pavement design guidelines and practice deficiencies, Draft Deliverable 3 Interim pavement design and cost charts and Deliverable 4A Life cycle cost analysis Part A: model, data preparation, and results of new design options for flexible pavements. This supplement draws from many sources; particularly the following published guidelines and technical papers: Pavement Design Guide, AASHTO, 1993 Austroads Pavement Design A Guide to the Structural Design of Road Pavements 2008 Overseas Road Note 31, Transport Research Laboratory (TRL), UK, 1993 LR 1132, Transport Research Laboratory, 1986 The debt owed to these documents must be acknowledged. Ir. Purnomo S, Director Bintek, and Dr. Ir. Hedi Rahadian MSc have provided invaluable guidance on the many pavement related issues facing the Technical Directorate of DGH (Bintek). Valuable dialogues have been held with Ir. Nyoman and the pavements staff of the Indonesian Road Research Institute (Pusjatan). The Department of Communication (Perhubungan) provided access to their weighbridge facility at Demak, Central Java, which allowed the collection of necessary confirmation of articulated vehicle axle weights.

4 Any errors of fact or interpretation of previous studies under the IndII Road Sector Development Programme are solely those of the author. Ed Vowles, Team Leader Jakarta, May 2011 Document Control: IndII RSDP3 Activity 201 Deliverable 6B Rehabilitation and Recycling Version Date Author Initials Reviewer Initials Geoff Jameson HIS edit corrections August 2011 Edward James Tyrone Toole PREAMBLE This document is designed to be used in conjunction with current pavement design instructions: Directorate General of Highways (DGH) 2002: Flexible Pavement and DGH 2005: Overlay Design using Deflections. The objective of this format is to facilitate immediate introduction of necessary changes. The Indonesian Road Research Institute (Pusjatan) has commenced a review of pavement design instructions in current use. Once that review is complete, incorporation of this and other planned supplements in a single concise pavement design guideline format will be possible. Efficient pavement design and maintenance solutions will only become possible when the following issues have been comprehensively addressed: a) Enforcement of reasonable axle loading limits b) Enforcement of reasonable construction quality standards General specification and design specification changes are required to support field use of the extended analysis and design treatments set offered by this document. Changes to the Indonesian Road Management System are needed to support identification of candidate projects for reconstruction or recycling and to introduce deflection-based overlay design to the planning process. Consultant and contractor training will be required. IndII 2011 All original intellectual property contained within this document is the property of the Indonesia Infrastructure Initiative (IndII). It can be used freely without attribution by consultants and IndII partners in preparing IndII documents, reports designs and plans; it can also be used freely by other agencies or organisations, provided attribution is given. Every attempt has been made to ensure that referenced documents within this publication have been correctly attributed. However, IndII would value being advised of any corrections required, or advice concerning source documents and/ or updated data.

5 TABLE OF CONTENTS ABBREVIATIONS, ACRONYMS AND TRANSLATIONS... V CHAPTER 1: INTRODUCTION... 1 CHAPTER 2: SELECTION OF REHABILITATION TREATMENTS TREATMENT SELECTION PROCESS OUTLINE... 5 CHAPTER 3: DESIGN TRAFFIC PAVEMENT DESIGN LIFE ESTIMATING VEHICLE DAMAGE FUTURE AXLE LOAD CONTROL TRAFFIC GROWTH RATE LANE DISTRIBUTION FACTOR AND LANE CAPACITY VEHICLE TYPE VEHICLE DAMAGE FACTORS (VDF) TRAFFIC MULTIPLIER... 9 CHAPTER 4: SUBGRADE SUPPORT FOR RECONSTRUCTION AND RECYCLING EXISTING PAVEMENT ANALYSIS SOFT SOIL TREATMENTS PEAT EXPANSIVE SOILS CHAPTER 5: MATERIALS CHARACTERISATION CHAPTER 6: DRAINAGE CHAPTER 7: THICKNESS DESIGN OF OVERLAYS INTRODUCTION DESIGN TRAFFIC LESS THAN OR EQUAL TO 10 7 ESA Adjustment of measured curvature to account for testing temperature Standardisation of deflections and curvatures Calculation of characteristic curvatures Fatigue of an asphalt overlay CHAPTER 8: THICKNESS DESIGN OF FOAMED BITUMEN STABILISATION TREATMENTS INTRODUCTION MATERIALS SUITABLE FOR FOAMED BITUMEN STABILISATION MINIMUM SURFACING REQUIREMENTS THICKNESS DESIGN CHARTS DESIGN PROCESS i

6 CHAPTER 9: DESIGN OF CEMENT STABILISATION TREATMENTS MATERIALS SUITABLE FOR CEMENT STABILISATION MINIMUM SURFACING REQUIREMENTS THICKNESS DESIGN CHARTS DESIGN PROCESS CHAPTER 10: CONSTRUCTION ISSUES AND PAVEMENT PERFORMANCE PREPARATION OF EXISTING PAVEMENTS FOR OVERLAY PAVEMENT LAYER THICKNESSES PAVEMENT EDGE (INCLUDING MEDIAN) SUPPORT BOXED CONSTRUCTION WET SEASON EFFECTS CONSTRUCTION UNDER TRAFFIC JOINT LOCATIONS CONSTRUCTION SEQUENCE FOR RECYCLING ANNEXE 1: COMMERCIAL FLEET VDF CALCULATOR ANNEXE 2: DEVELOPMENT OF THE THICKNESS DESIGN METHOD FOR FOAMED BITUMEN STABILISATION ANNEXE 3: FOAMED BITUMEN STABILISATION DESIGN CHARTS, DESIGN TRAFFIC UP TO 108 ESA ANNEXE 4: FOAMED BITUMEN STABILISATION DESIGN CHARTS, DESIGN TRAFFIC 10 8 TO 10 9 ESA ANNEXE 5: CEMENT STABILISATION DESIGN CHARTS REFERENCES ii

7 LIST OF TABLES Table 2.1: Design life, rehabilitation triggers and surfacing type relationships for reconstruction and recycling... 3 Table 2.2: Selection of treatment types... 4 Table 2.3: Roughness triggers for overlay and reconstruction... 5 Table 2.4: Triggers for overlay, reconstruction or recycling... 6 Table 3.1: Presumptive traffic growth rates (Bintek concurrence required)... 8 Table 3.2: Lane distribution factor... 8 Table 3.3: Classification of vehicles and standard VDF values: Java arterial Table 5.1: Characteristic moduli used for development of design charts and for mechanistic design Table 5.2: Characteristic Poisson s ratio values Table 5.3: Characteristic unbound materials moduli used for development of design charts Table 8.1: Guide to the selection of method of stabilisation Table 8.2: Minimum surfacing requirements over foamed bitumen stabilised materials Table 8.3: Procedure for foamed bitumen stabilisation design Table 9.1: Procedure for CTSB design Table 10.1: Permitted layer thicknesses iii

8 LIST OF FIGURES Figure 1.1: Flexible pavement structure components... 2 Figure 6.1: m factor adjustments for subgrade drainage condition Figure 6.2: Examples of subsoil drainage for various site conditions Figure 7.1: Curvature function Figure 7.2: Temperature correction for Benkelman Beam for various asphalt thicknesses Figure 7.3: Temperature correction for FWD for various asphalt thicknesses Figure 7.4: Curvature standardisation factors Figure 7.5: Asphalt overlay fatigue lives MAPTs >35 C Figure 8.1: Foamed bitumen pavement recycling Figure 8.2: Zone A grading envelope Figure 8.3: Example design chart for thickness design foamed bitumen stabilisation recycling Figure 9.1: Example design chart for thickness design cement treated sub-bases (CTSB) Figure 10.1: Pavement edge support and median treatment Figure 10.2: (A and B) Construction sequence for recycling with widening iv

9 ABBREVIATIONS, ACRONYMS AND TRANSLATIONS AADT Average annual daily traffic AASHTO Association of American State Highway and Transportation Officials AC Asphaltic concrete ACf Fine graded asphaltic concrete ACc Course graded asphaltic concrete AC BC Asphaltic concrete binder course AC WC Asphaltic concrete wearing course AMP Asphalt mixing plant Angkot Mini bus AusAID Australian Agency for International Development Austroads Association of Australian and New Zealand road transport and traffic authorities ARRB Australian Road Research Board Bintek Technical Directorate of DGH BB Benkelman Beam Cakar ayam Friction pile system of Indonesian origin to support rigid pavement on soft soil CBR Californian bearing ratio CC Characteristic Curvature CESA Cumulative equivalent standard axles CIRCLY Australian mechanistic design software program used by Austroads 2004 CF Curvature function = D 0 -D 200 CTB Cement treated base CTSB Cement treated sub-base D 0 Maximum deflection D 200 Deflection when the load has moved 200 mm from the test point DCP Dynamic cone penetrometer DG Director General DGH Directorate General of Highways (Bina Marga) DGH 2002 DGH Flexible Pavement Design Guide DGH 2003 DGH Rigid Pavement Design Guide DGH 2005 DGH Asphalt Overlay Design Guide EA Executing agency ESA 4 Equivalent standard axle 4th power ESA asphalt Equivalent standard axle for asphalt (5th power) FB Foamed bitumen Ft Temperature factor FWD Falling weight deflectometer FY Fiscal year GMP General mechanistic procedure Gol Government of Indonesia HRS Hot rolled sheet IndII Indonesia Infrastructure Initiative v

10 Ir IRI IRMS K kn Lij LMC LR m MAPT MDD MPa OMC ORN PI PPK Pusjatan RF Sirtu SL SG2 Tmeas TM asphalt TRL VDF Vb WMAPT μɛ Engineer International Roughness Index Indonesian Road Management System Constant Kilo Newtons Load on any axle Lean mix concrete TRL report reference Correction factor for granular layer thickness relating to drainage conditions Mean annual pavement temperature Maximum dry density Megapascal Optimum moisture content Overseas Road Note Plasticity Index Pejabat Pembuat Komitment (Sub Project Manager) Road Research Institute (Indonesia) Reliability factor Coarse river gravel Standard load Subgrade with CBR 2 percent Temperature measured Traffic multiplier for design of asphalt layers Transport Road Laboratory (UK) Vehicle damage factor Specific volume of bitumen in an asphalt mixture Weighted mean average pavement temperature Microstrain vi

11 CHAPTER 1: INTRODUCTION CHAPTER 1: INTRODUCTION This supplement shall be used in conjunction with Directorate General of Highways (DGH) 2002: Flexible Pavement Design, and DGH 2005: Pusjatan Overlay Design using Deflections, and shall take precedence over those documents. The document scope includes design of pavements for structural rehabilitation treatments, including recycling. Procedures and warrants provided by this document strengthen the existing Guidelines with respect to: a) Service life delivery b) Minimisation of life cycle costs c) Practical construction d) Efficient use of material resources Significant changes compared to DGH 2002 include: a) Optimum design lives determined from life cycle cost analysis b) Correction for climate factors that affect pavement service life c) Comprehensive axle load analysis d) Service temperature effects e) Introduction of structural design of in situ cement stabilisation treatments f) Introduction of structural design of in situ foamed bitumen stabilisation treatments g) Drainage design h) Layer analysis requirements for DGH 2002 (Association of American State Highway and Transportation Officials [AASHTO] based) i) Support for mechanistic design j) Catalogue design solutions This document will form part of a planned suite of highway design supplements. Other planned supplements in the series include: PART I PART III PART IV PART V PART VI New Pavement Design Drainage Reconnaissance Mechanistic Design Geometric Design 1

12 The pavement structure terminology and the pavement structures described throughout the text are illustrated by Figure 1.1. Figure 1.1: Flexible pavement structure components 2

13 CHAPTER 2: SELECTION OF REHABILITATION TREATMENTS CHAPTER 2: SELECTION OF REHABILITATION TREATMENTS There are two treatment selection stages: Planning; Project; sections broad selection of candidate routes and global treatments close interval testing and detailed treatments for homogeneous Table 2.1 provides an outline of the triggers applicable to each selection stage. A trigger is defined within this document as a test value at which a rehabilitation treatment becomes viable. Trigger 1 is the test value at which an overlay becomes viable. Trigger 2 is the test value at which reconstruction is likely to be a more practical and cost effective treatment than a structural overlay. Table 2.1: Design life, rehabilitation triggers and surfacing type relationships for reconstruction and recycling Design life (years) Light traffic ESA4/10 <1 million All other roads ESA4/10 million 10 all treatments 20 - structural overlay, and reconstruction 15 non-structural overlay 10 - holding treatments Equivalent traffic repetitions (million ESA) ESA4/10 1 (current Indonesian practice) < >2.5 ESA 5/10 (proposed for light traffic) < >4.25 ESA 5/15 < >7.2 ESA5/20 (proposed for intermediate and heavy traffic) < >10 Asphalt type HRS, surface dressing, other AC f ACc 1 Fourth power equivalent standard axle (ESA), 10 year design life. 3

14 Treatment triggers Planning level triggers IRI, visual IRI, deflection at 200m c/c visual Project level triggers IRI (primary) deflection 2 visual DCP Curvature and deflection at 50m c/c DCP, IRI, visual Test pits 3 DCP, IRI, visual Tables 2.2 (a), (b) and (c), provide detailed treatments and project selection trigger types for homogeneous sections. A homogeneous section is defined as a road section requiring a single set of treatments. Selection of treatments at the project level also requires judgment. Table 2.2: Selection of treatment types (a) Selection of treatment type < 1.7 million ESA 5/10 Treatment 1 Routine maintenance only Triggers for any homogeneous section IRI below trigger 1, serious distress < 5% of area 2 Heavy patching Visible failures exceeding 10 m2 and areas with deflection above trigger 2 provided those areas do not exceed 30% of total 3 Mill and replace selected areas Extensive alligator cracking, or ruts >30 mm or IRI > trigger 3 4 Overlay Deflection or IRI above trigger 1 and below trigger 2 5 Reconstruct Deflection above trigger 2, existing asphalt < 10 cm or heavy patch exceeds 30% of area 6 Recycle Deflection above trigger 2, existing asphalt > 10 cm or heavy patch exceeds 30% of area (b) Selection of treatment type 4 10 million ESA 5 /20 Treatment 1 Routine maintenance only Triggers for any homogeneous section Deflection, curvature and IRI below trigger 1, serious distress < 5% of area metre intervals or greater. 3 AASHTO SN or Mechanistic design. 4

15 CHAPTER 2: SELECTION OF REHABILITATION TREATMENTS Treatment Triggers for any homogeneous section 2 Heavy patching Visible failures exceeding 10m2 and areas with deflection above trigger 2 provided those areas do not exceed 30% of total 3 Mill and replace selected areas Extensive alligator cracking, or ruts >30 mm or IRI > trigger 3 4 Overlay Deflection, curvature or IRI above trigger 1 and below trigger 2 5 Reconstruct Deflection or curvature above trigger 2, existing asphalt < 10 cm 6 Recycle Deflection or curvature above trigger 2, existing asphalt > 10 cm Tables 2.3 and 2.4 provide project level triggers for a range of traffic levels. Selection of detailed planning level triggers and realistic budgets for planning purposes that are associated with those triggers will be addressed in Phase 2 of this study. Table 2.3: Roughness triggers for overlay and reconstruction AADT IRI trigger justifying an overlay IRI trigger justifying a holding treatment overlay IRI trigger for investigation of reconstruction or recycling < > > > TREATMENT SELECTION PROCESS OUTLINE 1. Determine the design life from Table Determine traffic loading (equivalent standard axle [ESA]4 value) by the method given in Section Determine design ESA values (ESA5/10, ESA 5/15 or ESA 5/20) by calculation by the method described in Section Use Table 2.2 (a), (b) or (c), Table 2.3 and Table 2.4 as applicable to select the optimum treatment type or types also using judgment when necessary. 5. Calculate alternative actual treatment thicknesses using this Supplement, Supplement I and the DGH Design Guides 2002 and

16 Planning and project level triggers 6. When more than one solution is possible, select the most cost-effective solution using discounted whole-of-life analysis. Table 2.4: Triggers for overlay, reconstruction or recycling Traffic for 10 years (million ESA5/lane) Surfacing type Deflection triggers justifying an overlay 4 Characteristic deflection Benkelman Beam (mm) 5 D0-D200 Curvature FWD (mm) Deflection triggers justifying an investigation for reconstruction or recycling Characteristic deflection Benkelman Beam (mm) 6 D0-D200 Curvature FWD (mm) <0.1 HRS >2.3 Not applicable HRS > >3.0 Not applicable HRS > > HRS > > HRS > AC > AC > AC > AC > Planning level triggers AC AC / rigid AC / rigid >0.5 and surface under defects as investigation Table 2.2c AC / rigid 0.9 under investigation 4 Below these values an overlay is not required except to restore shape or to address surface deterioration. 5 An adjustment factor applies to falling weight deflectometer (FWD) readings. 6 An adjustment factor applies to FWD readings. 7 test pit analysis is also necessary for project level design other than for non structural overlays 6

17 CHAPTER 3: DESIGN TRAFFIC CHAPTER 3: DESIGN TRAFFIC 3.1 PAVEMENT DESIGN LIFE Structural treatments, including asphalt overlays, in situ stabilisation with cement or foamed bitumen shall be undertaken using design traffic predicted for a 10- to 20-year design life. The design life shall be in accordance with Table 2.1 unless otherwise instructed or approved by the Technical Directorate of DGH (Bintek). 3.2 ESTIMATING VEHICLE DAMAGE Accurate traffic counts are essential. The percentage and type of commercial vehicles varies between routes but the level of overloading of specific vehicle types and load categories is believed to be reasonably constant across all provinces. Therefore a reasonable estimate of ESA value can be obtained from a traffic count for current Indonesian conditions and from the standard damage factors (vehicle damage factor [VDF]) given by Table 3.3. A spreadsheet calculator that only requires input of vehicle type and load category numbers is provided in Annexe 1. Although 100 kilo Newtons (kn) axle loads are permitted on some routes, the ESA values shall nevertheless always be determined on the basis of a 80 kn standard axle load. 3.3 FUTURE AXLE LOAD CONTROL There is an extremely high road asset maintenance cost associated with overloading in Indonesia. There is also a serious safety issue. Effective control is essential if pavement replacement and maintenance costs are to be controlled. The only prudent policy for current pavement designs is to assume that current overload levels will continue. ALTERNATIVE DESIGN WARRANT FOR COMMERCIAL VEHICLE LOADING: Unless otherwise instructed or approved by Bintek, current levels of overloading shall be assumed until year An agreed level of loading control shall be assumed after that date. At the date when legal loading is presumed to become effective (January 2021), the traffic flow rate used for calculation of cumulative equivalent standard axles shall be increased by an amount sufficient to maintain an equal volume of goods transported compared to the overload case. A DECISION ON THIS MATTER IS FUNDAMENTAL TO THE SUCCESS OF FUTURE PAVEMENT DESIGN AND ROAD ASSET MANAGEMENT. ADDITIONAL LEGISLATION MAY BE REQUIRED TO SUPPORT RIGOROUS ENFORCEMENT. 7

18 3.4 TRAFFIC GROWTH RATE Growth rates shall be as provided in Table 3.1 unless evidence is provided to justify alternative values. Table 3.1: Presumptive traffic growth rates (Bintek concurrence required) > Arterial and metropolitan (%) 5 4 Rural (%) LANE DISTRIBUTION FACTOR AND LANE CAPACITY The lane distribution of commercial vehicles shall be as provided by Table 3.2. The design traffic loading on any lane shall not exceed the lane capacity in any year within the design life. The maximum lane capacity shall be 18,000 average annual daily traffic (AADT). Table 3.2: Lane distribution factor Number of lanes in each direction Commercial vehicles in design lane (% of total commercial vehicle population) VEHICLE TYPE The vehicle classification system shall be as defined by Table 3.3. The subdivision of vehicle types and cargos defined by the table shall be used for all data collection. Table 3.3 provides a distribution of commercial vehicle types that are typical for arterial routes in Java. 8

19 CHAPTER 3: DESIGN TRAFFIC 3.7 VEHICLE DAMAGE FACTORS (VDF) Vehicle damage factors (VDF) shall be determined from axle loads measured from a fixed weigh bridge study or from Table 3.3. If a portable weighbridge system is used it shall have a wheel pair weight capacity of not less than 18 tonne or an axle weight capacity of not less than 35 tonne. Lower capacity systems shall not be used. Weigh-inmotion data shall only be permitted if the equipment used has been comprehensively calibrated against weighbridge data. Fourth power VDF (VDF4) values shall be determined using the axle group values provided by DGH Table 3.3 provides vehicle damage factor (VDF4) values that are typical for arterial routes in Java. Table 3.3 also provide fifth power VDF (VDF5) as fatigue of asphalt is related to the 5th power of axle group load (refer to Section 2.8). Annexe 1 provides a simple procedure for determining characteristic VDF values for any traffic count. The traffic count should include all vehicle types and the goods categories listed in Table TRAFFIC MULTIPLIER Section of the Austroads Guide (2008) describes various indices used to assess the pavement damage due to axle group load. For flexible pavements it is common to express damage caused by the design traffic in terms of an equivalent number of passes of an 80 kn Standard Axle. When the pavement damage varies with the fourth power axle load, the equivalent number of Standard Axle repetitions is calculated as follows from AASHTO road test: ESA 4 = L ij SL 4 Flexible pavement performance is influenced by a number of factors not captured by the 4 th power rule. Asphalt fatigue relationship is related to the 5 th power of strain (and hence axle load) as follows: Asphalt fatigue life = RF 6918(0.856 Vb ) 5 (Austroads, 2008) ɛ As a result, expressing the damage due to the design traffic in ESA 4 underestimates the damage in terms of asphalt fatigue. Consequently traffic the multipliers (TM) is used as a convenient device to adjust the ESA 4 design life to the asphalt fatigue design life (ESA 5 ) in design calculations: The method of assessment of axle group damage should be reviewed when related Australian Road Research Board and other research is complete. 9

20 ESA 5 = TM asphalt. ESA 4 where ESA 5 = the number of standard axle repetitions for use in assessing asphalt fatigue life (5 th power rule) ESA 4 = the number of standard axle repetitions calculated using the 4 th power rule The asphalt fatigue TM value (TM asphalt ) for normal Indonesian loading conditions is typically 2.06 but may vary depending on the extent of overloading of commercial vehicles in the truck fleet. Annexe 1 provides a calculator for TM asphalt for any commercial fleet distribution and standard Indonesian vehicle loadings. 10

21 COMMERCIAL VEHICLES CHAPTER 3: DESIGN TRAFFIC Table 3.3: Classification of vehicles and standard VDF values: Java arterial 2011 DGH Vehicle type Proposed Description Axle configuration Axle groups Typical distribution (percent) All motorised vehicles All motorised except motor bikes Vehicle damage factor (VDF) (ESA/vehicle) 4 th power (VDF 4) 5 th power (VDF5) Combined values (distribution x VDF - motor bikes excluded) VDF4 VDF5 1 1 Motor bike , 3, 4 2, 3, 4 Sedan/angkot/pickup/station wagon a 5a Light bus b 5b Heavy bus a axle truck - light general cargo a axle truck - light earth, sand b b axle truck - medium general cargo 2-axle truck - medium earth, sand, steel b axle truck - heavy general cargo

22 DGH Vehicle type Proposed Description Axle configuration Axle groups Typical distribution (percent) All motorised vehicles All motorised except motor bikes Vehicle damage factor (VDF) (ESA/vehicle) 4 th power (VDF 4) 5 th power (VDF5) Combined values (distribution x VDF - motor bikes excluded) VDF4 VDF5 6b axle truck - heavy earth, sand, steel a axle truck - general cargo a axle truck - earth, sand PC, steel a axle truck - general cargo b 10 2-axle truck and 2 axle towed trailer c axle truck - trailer c axle truck - trailer c axle truck - trailer c axle truck - trailer

23 CHAPTER 4: SUBGRADE SUPPORT FOR RECONSTRUCTION AND RECYCLING CHAPTER 4: SUBGRADE SUPPORT FOR RECONSTRUCTION AND RECYCLING 4.1 EXISTING PAVEMENT ANALYSIS The Supplement Part I Section 5 provides procedures for determining subgrade California bearing ratio (CBR) and for standard subgrade treatments including for expansive and soft soil that must also be applied to rehabilitation works. The key difference for rehabilitation works is that the existing pavement layers usually prevent further treatment of the existing subgrade. Areas where heavy patching is required are an exception. Subgrade analysis can be by dynamic cone penetrometer (DCP) (best choice for saturated ground), by Atterburg limits and Part I Design Chart 8.1 or by fourday soaked CBR at the in situ density. The thickness of existing pavement layers remaining after recycling or other treatment can also be determined from the test pit survey. The characteristic existing subgrade CBR value and the remaining characteristic existing pavement layer thickness are necessary inputs to the design charts provided in this document. These data are also needed for mechanistic or Structural Number based design. The subgrade and the existing pavement thickness are likely to be highly variable. Homogeneous sections must be determined and characteristic values must then be used for design following the same principles as for new pavement subgrade analysis. a) Coefficient of variation for a homogeneous section = standard deviation/mean < 0.3 b) Characteristic CBR = mean CBR 1.3 x standard deviation c) Characteristic remaining thickness of existing pavement after other treatments = mean remaining thickness 1.3 x standard deviation Heavy patching areas shall be designed in the same manner as for new pavement (Supplement Part I). Heavy patching is required in areas where the existing pavement has failed or where the existing pavement layers are insufficient to provide an adequate foundation. Part I Design Chart 8.2 must be satisfied for existing pavement layer thicknesses other than the recycled layer, necessary to provide adequate foundation support for recycling. 4.2 SOFT SOIL TREATMENTS Soft soil areas are defined as areas having an in situ CBR significantly lower than 2 percent. They are unable to support compaction of subsequent layers without special treatment. In Indonesia, soft soil areas are usually alluvial or marine silty clays that are 13

24 permanently or seasonally saturated. Soft soil areas frequently exhibit instability that must be treated either by grade raising, reconstruction or other treatment. Grade raising is often applied in country areas when there is no finished surface level height constraint. When full construction is required the requirements of Supplement I shall apply. The capping layers should preferably be rock or sirtu (coarse river gravel). A geotextile layer should be used to separate original ground from the capping to limit pumping of the soft soil zone into the capping material. The extent of soft soil areas should be determined by DCP testing. A 2 metre deep DCP test is recommended (standard DCP with extension rod). Tests should be conducted at 20 metre centres. Special treatment such as micro piling or cakar ayam (friction pile system of Indonesian origin) to support rigid pavement on soft soil) must be considered for areas where the depth from original ground to CBR 2 equivalent bearing capacity exceeds 2.0 metres at any point, especially for rigid pavement construction. Micro piling, cakar ayam, injection piling or similar treatment is likely to be necessary when restoring block cracked rigid pavement on soft soil. Grade raising designs should consider: a) Embankment heights should be between 2 and 2.5 metres. b) Height of new subgrade should preferably be a) 1 metre above standing water, and b) not less than 300mm above 10-year flood. c) The foundation design rules provided in Supplement I should be satisfied. The settlement rates and embankment stability should be considered when widening embankments, especially those exceeding 2 metres in height. Preloading should be used to limit differential movement between the existing embankment and the widening. Micro piling or other treatment may be required at bridge approaches. Geotechnical advice should be sought. Embankment batter slopes should be not steeper than 1V: 3H. Use of edge walls should be avoided. If used, wall stability shall be checked and piling or other treatment used as necessary. 4.3 PEAT Specialist geotechnical advice must be obtained. Preloading is always necessary when widening existing pavement. Adequate cross drainage must be maintained at all times. Batter slopes should be not steeper than 1V: 3H. In addition to this, high embankments should be benched. Bridge approaches should be piled. Georgic treatments should be considered. Geotextile should be used at the interface between original ground and widening. 14

25 CHAPTER 4: SUBGRADE SUPPORT FOR RECONSTRUCTION AND RECYCLING 4.4 EXPANSIVE SOILS Reference should be made to Supplement I. The most important consideration is to limit moisture variation in the expansive soil layer by: a) Sealing the road shoulder b) Providing good surface and subsurface drainage including sealing of all surface drains, and ensuring that any subsurface drain provided has a 0.5 percent invert gradient and a permanent discharge point above flood level and above water levels in the drainage system Providing the minimum cover thicknesses required by Supplement I. 15

26 CHAPTER 5: MATERIALS CHARACTERISATION Characteristic materials moduli and Poisson s ratio for Indonesian climatic and loading conditions are provided by Table 5.1 and 5.2 for bound materials and Table 5.3 for unbound granular materials. Other characteristic asphalt materials parameters required for mechanistic design are also provided by Table 5.1. Asphalt moduli have been determined based on an air temperature range of 25-34oC and a mean annual pavement temperature (MATP) of 41oC. These values are reasonable for use throughout Indonesia other than for mountainous areas where a MAPT of 35 o C may be appropriate. Table 5.1: Characteristic moduli used for development of design charts and for mechanistic design Material type Typical modulus for Indonesia (MPa) Volume of binder (Vb) (%) Asphalt fatigue parameter K 1 for Indonesian climatic conditions AASHTO 9 structural coefficient HRS WC HRS BC AC WC AC BC Foamed bitumen stabilised material (effective long-term value) Cemented material (effective long-term value) Subgrade x CBR 1. K = (6981(0.856Vb )/E To be confirmed by the Indonesian Road Research Institute (Pusjatan) 16

27 CHAPTER 5: MATERIALS CHARACTERISATION Table 5.2: Characteristic Poisson s ratio values Material Typical modulus for Indonesia Asphalt 0.40 Foamed bitumen stabilised material 0.40 Cemented material 0.35 Granular materials 0.35 Cohesive subgrade 0.45 Non-cohesive subgrades 0.35 As described in Section of the Association of Australian and New Zealand road transport and traffic authorities (Austroads) Guide, the moduli of granular materials varies with thickness and stiffness of overlying bound (e.g. asphalt) pavement layers. Characteristic granular moduli and Poisson s ratio for Indonesian climatic and loading conditions are provided by Table 5.3. Table 5.3: Characteristic unbound materials moduli used for development of design charts Thickness of overlying bound material (mm) 900 MPa (HRS WC/ HRS BC) Modulus of overlying bound 10 material 1100 MPa (AC WC) 1200 MPa (AC BC) Overlying bound material may be asphalt, cemented materials of foamed bitumen stabilised materials 17

28 CHAPTER 6: DRAINAGE Subsoil drains shall be provided whenever necessary for national and provincial roads and in cases where high groundwater pressures are known to exist for local roads generally. Judgment must be used. When an existing road shows moisture related distress either surface drainage or subsoil drainage improvement must be provided. Subsoil drains must have free draining and maintainable discharge points that are not subject to, or are only occasionally subject to, flooding. If there is moisture related distress and a subsoil or surface drainage solution cannot be provided, m factor adjustment (correction factor for granular layer thickness relating to drainage conditions) and associated grade raising may be necessary. In mountainous areas, discrete pavement failures caused by drainage system deficiencies can often be identified. In these cases surface or subsoil drainage solutions should be provided in addition to other treatments. Even if extensive treatment is required this will always be cost effective. Further information will be provided in the Drainage Design Guide. The following rules should be satisfied for all rehabilitation works: All sub-base layers shall be free draining. Pavement widening designs shall ensure free drainage of the lowest granular layer of the existing pavement. Lateral drains shall be provided through embankment verges when the flow path from the subbase layer to the embankment edge exceeds 300mm. Subsoil drains shall be provided in all cuts and at grade areas where the sub-base level is lower than the adjacent ground level (this condition shall be avoided by good geometric design when possible); if not possible m factor adjustment rules shall apply (Table 6.1). Subsoil drains shall be provided adjacent to all u-ditches and other structures that block the free flow of water from any sub-base layer. Subsoil drains must have a gradient of not less than 0.5 percent towards an outlet point and must have a rod point, a discharge point or a sump at not more than 60m spacing. Subsoil drains entry and discharge points shall be higher than five-year storm levels. Super elevated sections of divided roads, when draining towards the median, shall be provided with a subsoil drainage system at the median. When subsoil drainage cannot be provided, m factor adjustments shall be used for granular layer thickness design in accordance with AASHTO 93 Rule and this Supplement Table

29 CHAPTER 6: DRAINAGE Figure 6.1: m factor adjustments for subgrade drainage condition 19

30 Figure 6.2: Examples of subsoil drainage for various site conditions Figure 6.2 provides examples of subsoil drainage system positions that are appropriate for various site conditions. 20

31 CHAPTER 7: THICKNESS DESIGN OF OVERLAYS CHAPTER 7: THICKNESS DESIGN OF OVERLAYS 7.1 INTRODUCTION This section describes procedures for determining the design thickness of overlays placed to rectify the distress and structural deficiencies of an existing pavement. Such treatments may often be placed on pavements for other reasons that relate to the rectification of the functional characteristics of pavements, such as shape, ride quality and surface competency. The structural adequacy of these treatments also needs to be considered. Currently, DGH has two guidelines that may be used for the design of asphalt overlays: A deflection-based approach contained in the Indonesian Road Research Institute (Pusjatan) Guide to Overlay Design Using Deflections. A Structural Number approach contained in the Pusjatan Guide to the Design of Flexible Pavements (Pt T B). The Pusjatan deflection-based approach uses maximum deflections (D 0 ) to determine the required overlay thicknesses. The Austroads overlay method utilises these design deflections to determine asphalt overlay thickness to inhibit sub-base and subgrade rutting and shape loss. However, these design deflections (D 0 ) are not suitable for assessing whether asphalt overlays will fatigue crack. Consequently, for road projects with design traffic loading less than or equal to 10 7 ESA, Austroads have an additional requirement that the deflection bowl curvature (D 0 - D 200 ) be checked to ensure the fatigue resistance of the overlay. It is recommended this requirement be added to the Pusjatan deflection-based approach as described in Section 7.2. For rehabilitation projects with design traffic loading greater than 10 7 ESA, Austroads recommends the use of general mechanistic procedures (GMP) based on estimating the moduli of the existing pavement. These moduli are then used in the mechanistic method for the design of new pavements to assess the resistance to rutting and fatigue of asphalt overlay thicknesses. The use of the GMP requires the development of an Indonesian mechanistic method for the design of new pavements. Hence the GMP approach is currently unsuitable for routine use by Indonesian designers. It is recommended that for rehabilitation projects with design traffic loading greater than 10 7 ESA 11, the overlays estimated by the Pusjatan deflection-based approach be checked for structural adequacy using the Structural Number approach contained in the Pusjatan Guide to the Design of Flexible Pavements year design life, 5 th power (ESA 5/20 ) 12 If the Austroads mechanistic method (CIRCLY) is used to check or determine the overlay thickness the moduli and mechanistic design parameters provided in Section4 and 5. should 21

32 When the subgrade or original ground is CBR 2.5 or weaker, especially when traffic the existing pavement layer thicknesses including any subgrade improvement or capping layer shall be determined from test pits or cores combined with DCP readings when necessary. For this case the subgrade and original ground (beneath any capping) bearing capacities or moduli shall be determined by the methods described in Section DESIGN TRAFFIC LESS THAN OR EQUAL TO 10 7 ESA As discussed in Section 7.1, it is recommended the Austroads curvature requirement be added to the Pusjatan deflection-based approach for projects with a design traffic loading less than or equal to 10 7 ESA. Due to the high fatigue resistance of hot rolled sheet (HRS) wearing course, there is no need for checking the curvature requirements when the deflections indicate only a thin HRS wearing course is required. The curvature function (CF) of a deflection bowl is given by where CF = D 0 - D 200 D 0 D 200 = maximum deflection at a test point (mm) = the deflection measured at the test point when the load has moved 200mm from the test point Figure 7.1 shows in schematic form the dimension represented by the curvature function. Figure 7.1: Curvature function Source: Austroads be used. Appropriate mechanistic design parameters for deformation of Indonesian soft soils are currently under investigation. 22

33 CHAPTER 7: THICKNESS DESIGN OF OVERLAYS Adjustment of measured curvature to account for testing temperature For asphalt overlays on asphalt surfaced granular pavements, the measured curvatures need to be corrected because pavement temperature influences pavement stiffness and response to load. Any significant difference between the pavement temperature at the time of testing and in-service conditions means the curvature measurements would be unrepresentative of the normal pavement response to traffic loadings. The in-service pavement temperature at a site is characterised by the mean annual pavement temperature (MAPT), which is 41ºC for Indonesia. The temperature correction factor is calculated using the following procedure: Step 1 Determine the temperature factor f T where (Equation 7.1): ft = MAPTfor thesite Measuredpavement temperatur e at time of testing 7.1 Step 2 Determine the temperature correction factors using Figure 7.2 for Benkelman Beam and Figure 7.3 for falling weight deflectometer (FWD). No temperature correction is required if the bituminous surfacing is less than 25mm thick. Step 3 Multiply the deflection and curvature by the corresponding deflection and curvature temperature correction factors. Figure 7.2: Temperature correction for Benkelman Beam for various asphalt thicknesses Source: Austroads

34 Figure 7.3: Temperature correction for FWD for various asphalt thicknesses Source: Austroads Standardisation of deflections and curvatures As the curvatures of a pavement test site measured by Benkelman Beam and FWD differ, it is necessary to standardise the measured values. The overlay design charts for asphalt fatigue (Figure 7.5) are based on FWD curvatures (Austroads 2008). Hence, the values measured with Benkelman Beam need to be converted to equivalent FWD values. The standardisation factors required for this conversion vary with pavement composition and subgrade strength, and the most accurate factors are those obtained by paired field measurements. However, as it is often impractical to undertake such correlation studies, presumptive standardisation factors are provided in Figure

35 CHAPTER 7: THICKNESS DESIGN OF OVERLAYS Figure 7.4: Curvature standardisation factors Source: Austroads Calculation of characteristic curvatures For the design of flexible overlays on flexible pavements, a Characteristic Curvature (CC) is assigned to each subsection for evaluation purposes. These values are determined after the seasonal, temperature and standardisation adjustments have been made to the individual test measurements. The CC for a homogeneous subsection of pavement is equal to the mean of the curvature values calculated from the deflection survey Fatigue of an asphalt overlay Where an asphalt overlay is required to inhibit permanent deformation, or to restore pavement shape or skid resistance, for pavements with a design traffic loading of 10 5 ESA or more, it is necessary to check that fatigue performance of the overlay will be adequate. Asphalt fatigue is not a common distress mode for lightly trafficked (<105 ESA) pavements. 25

36 The procedure assumes that any existing asphalt layers have little or no remaining fatigue life, and that it will be uneconomical to design the overlay to inhibit fatigue cracking of these layers. Hence, the overlay is not designed to inhibit fatigue of any existing asphalt layers. Accordingly, the design charts are inappropriate to design asphalt surfaced pavements which are progressively strengthened in stages that have significant remaining asphalt fatigue life. Similarly, they do not apply to overlay requirements of newly constructed asphalt pavements. As asphalt fatigue is not a common distress mode for lightly trafficked roads, it is not necessary to check the fatigue performance of overlays for projects with design traffic loadings less than 10 5 ESA. The predicted fatigue performance of asphalt overlays is assessed using the CC (D 0 - D 200 ) of the deflected pavement surface. Design charts of overlay thicknesses for a range of traffic loadings and curvature values are shown in Figure 7.5 for MAPTs of >35 C, applicable to Indonesia. This chart may be used to determine the overlay thicknesses that have an allowable traffic loading in terms of fatigue cracking less than the design traffic loading, as discussed in Austroads Guide. Figure 7.5: Asphalt overlay fatigue lives MAPTs >35 C Source: Austroads

37 CHAPTER 8: THICKNESS DESIGN OF FOAMED BITUMEN STABILISATION TREATMENTS CHAPTER 8: THICKNESS DESIGN OF FOAMED BITUMEN STABILISATION TREATMENTS 8.1 INTRODUCTION Strengthening pavement using in situ foamed bitumen stabilisation is increasingly being used to recycle pavements worldwide, including Indonesia. Figure 8.1: Foamed bitumen pavement recycling Foamed bitumen is a hot bituminous binder that has been temporarily converted from a liquid state to a foamed state by addition of a small amount of water (2-3 percent of the bitumen mass). In the foamed state, bitumen can be mixed with aggregates at ambient temperatures and in situ moisture contents. The bitumen foam coats the fine fraction of the treated aggregate, creating mastic that binds the larger particles of the aggregate skeleton. Foaming agent may be needed to ensure the bitumen foaming properties are acceptable. In Indonesia, the foamed bitumen content added to the aggregates normally ranges from percent, and 1 percent cement is used as the secondary binder, although lime may be used for higher plasticity materials. 27

38 The strength/stiffness of foamed bitumen mixes is derived from: Friction between the aggregate particles Viscosity of the bituminous binder under operating conditions Cohesion within the mass resulting from the binder itself, and the adhesion between the bituminous and hydraulic binders and the aggregate Similar to other stabilising binders, foamed bitumen stabilisation can be undertaken in situ or in a mixing plant. The foamed bitumen is incorporated into the recycling drum or into the plant where it wets and coats the surface of the fine fraction particles to form a flexible bound pavement material. The mixing of the foamed bitumen and soil is critical to the success of the process because the bitumen is in its foamed state for only a very short period and coating of the particles must be achieved within this period. Given that the use of foamed bitumen treatments is more recent than many other rehabilitation treatments, mix and thickness design procedures are progressively being refined in various countries. The development interim thickness design method is described in Annexe 2. It is emphasised that the method is interim and it is recommended that the performance of foamed bitumen stabilised pavements recently constructed in Indonesia be monitored to further develop this interim method. 8.2 MATERIALS SUITABLE FOR FOAMED BITUMEN STABILISATION In Indonesia, foamed bitumen stabilisation is commonly applied to recycle existing asphalt and granular base materials. In assessing the suitability of materials for foamed bitumen stabilisation, the plasticity index (PI) should generally not exceed 10 unless treated with lime, subject to an upper PI limit of 20 (refer to Table 8.1). The material should also comply with the Zone A particle size distribution shown in Figure

39 CHAPTER 8: THICKNESS DESIGN OF FOAMED BITUMEN STABILISATION TREATMENTS Table 8.1: Guide to the selection of method of stabilisation 29

40 Figure 8.2: Zone A grading envelope 8.3 MINIMUM SURFACING REQUIREMENTS As discussed in Annexe 2, Table 8.2 describes the proposed minimum surfacing requirements over foamed bitumen stabilised materials. Table 8.2: Minimum surfacing requirements over foamed bitumen stabilised materials Design traffic (ESA5) >30 10 < Traffic < 30 Minimum surfacing 100mm comprising 40mm AC WC 60mm AC Binder 80mm comprising 2x40mm AC WC 1 < Traffic < 10 40mm AC WC < 1 30 HRS WC or surface dressing 30

41 CHAPTER 8: THICKNESS DESIGN OF FOAMED BITUMEN STABILISATION TREATMENTS 8.4 THICKNESS DESIGN CHARTS As described in Annexe 2, the Austroads mechanistic method for design of new flexible pavements together with the proposed minimum surfacing requirements (Table 8.1) were used to derive thickness design charts. These design charts are given in Annexes 3 and 4, Figure 8.3 illustrates one of the charts. In developing the design charts, the foamed bitumen stabilised depth was limited to a maximum of 300 mm due to concerns about in situ mixing and compaction at greater depths. Figure 8.3: Example design chart for thickness design foamed bitumen stabilisation recycling Asphalt Foamed bitumen stabilised material Remaining granular subbase 150 mm Subgrade design CBR =4 Foamed bitumen Asphalt Foamed bitumen thickness (mm) Total asphalt thickness (mm) mm HRS Wearing Course E E E E+08 Design traffic (ESA 5 ) 8.5 DESIGN PROCESS Table 8.3 lists the steps in the structural design of foamed bitumen stabilisation treatments. Table 8.3: Procedure for foamed bitumen stabilisation design Step Activity 1 Calculate the design traffic in ESA5 as described in Section 3. 2 Using the data from construction and maintenance records, test pits and cores determine the in situ material layer types, qualities and thicknesses. 31

42 Step Activity Determine a subgrade design CBR for the project, based on in situ dynamic cone penetrometer (DCP), or laboratory soaked CBR testing of material recovered from the test pits. Using step 3 data, assess whether the in situ materials are suitable for FB stabilisation. Using the layer thicknesses, select a trial stabilisation depth and calculate the remaining depth of pavement material beneath the stabilised layer. For pavements with a subgrade design CBR less than 5%, a minimum 100mm of pavement material is required below the FB layer. Using the design charts in Annexes 3 and 4, determine the asphalt thickness required over the FB stabilised material. 32

43 CHAPTER 9: DESIGN OF CEMENT STABILISATION TREATMENTS CHAPTER 9: DESIGN OF CEMENT STABILISATION TREATMENTS 9.1 MATERIALS SUITABLE FOR CEMENT STABILISATION In Indonesia, cement stabilisation of pavement materials is commonly applied to recycle existing asphalt and granular base materials. In assessing the suitability of materials for stabilisation, the PI should generally not exceed 10 unless treated with lime, subject to an upper PI limit of 20 (refer to Table 8.1). The material should also comply with the Zone A particle size distribution shown in Figure 8.2. The thickness design charts are suitable for use with stabilised materials with a minimum unconfined compressive strength of 2 Megapascal (MPa) at 28 days. Generally 3 percent by mass of Portland cement is suitable. 9.2 MINIMUM SURFACING REQUIREMENTS Surface cracking is common when cement treated bases are used with thin bituminous surfacing, unless slow setting cementitious blends (lime, slag, fly-ash) are used. As quick-setting Portland cement is commonly used in roadworks in Indonesia, the use of cement treated bases is not recommended as early fatigue cracking occurs under the very high axle loads leading to high pavement maintenance costs. It is recommended that cement stabilisation be limited to the provision of cement treated sub-base (CTSB) with a minimum asphalt surfacing thickness of 175mm (adapted from Austroads Guide, 2008). 9.3 THICKNESS DESIGN CHARTS The Austroads mechanistic method for design of new flexible pavements, together with the proposed minimum surfacing of 175mm asphalt, were used to derive thickness design charts. These design charts are given in Annexe 5; Figure 9.1 illustrates one of the charts. In developing the design charts, the cement stabilised depth was limited to a maximum of 300mm due to concerns about in situ mixing and compaction at greater depths. 33

44 The minimum design traffic provided in the charts is 10 7 ESA 5 as this treatment is unlikely to be cost-effective at lower traffic levels. Figure 9.1: Example design chart for thickness design cement treated sub-bases (CTSB) Asphalt 240 thickness (mm) Asphalt Cement stabilised material Remaining granular subbase 150 mm Subgrade design CBR=4 150 mm CTSB 200 mm CTSB 250 mm CTSB 300 mm CTSB E E E+09 Design traffic (ESA 5 ) 9.4 DESIGN PROCESS Table 9.1 lists the steps in the structural design of cement stabilised sub-bases. Table 9.1: Procedure for CTSB design Step Activity 1 Calculate the design traffic in ESA5 as described in Section Using the data from construction and maintenance records, test pits and cores determine the in-situ material layer types, qualities and thicknesses. Determine a subgrade design CBR for the project, based on in-situ dynamic cone penetrometer (DCP), or laboratory soaked CBR testing of material recovered from the test pits. Using step 3 data, assess whether the in situ materials are suitable for cement stabilisation. 34

45 CHAPTER 9: DESIGN OF CEMENT STABILISATION TREATMENTS Step 5 6 Activity Using the layer thicknesses, select a trial stabilisation depth and calculate the remaining depth of pavement material beneath the stabilised layer. For pavements with a subgrade design CBR less than 5%, a minimum 100mm of pavement material is required below the stabilised layer. Using the design charts in Annexe 5, determine the asphalt thickness required over the FB stabilised material. 35

46 CHAPTER 10: CONSTRUCTION ISSUES AND PAVEMENT PERFORMANCE A major improvement in construction quality standards is needed for all roadworks including rehabilitation works. It is not possible to adequately compensate for poor construction quality by pavement design adjustments PREPARATION OF EXISTING PAVEMENTS FOR OVERLAY Thorough preparation is essential. Pothole repairs, heavy patching, sealing of wide cracks, milling of ruts and severely cracked areas and repair of edge breaks must all be completed and accepted by the Engineer or Project Manager before the overlay is commenced PAVEMENT LAYER THICKNESSES Compaction and segregation limitations determine practical pavement structure thicknesses. Designs must recognise these limitations, including layer thicknesses in Table Table 10.1: Permitted layer thicknesses Material Thickness (mm) Multiple layers permitted HRS WC 30 No HRS BC 35 Yes AC WC 40 No AC Binder Yes Aggregate Base A 40 (40mm grading) Yes Aggregate Base A 30 (30mm grading) (recommended) Yes Aggregate Base B (50mm grading) 200 Yes Aggregate Base B (40mm grading) Yes CTSB (30mm grading)or LMC (lean mix concrete) No 36

47 CHAPTER 10: CONSTRUCTION ISSUES AND PAVEMENT PERFORMANCE 10.3 PAVEMENT EDGE (INCLUDING MEDIAN) SUPPORT Pavement structures require adequate edge support, particularly when placed on soft soil or peat. Edge support requirements must be detailed in contract drawings. Minimum requirements are: Each pavement layer shall be placed to a width equal to or exceeding the minimum indicated by Figure This rule also applies to medians on multi-lane facilities. Embankments on soft soil (< CBR 2) and peat shall be placed at a batter slope of not steeper than 1v:3h. Each pavement layer must be widened as shown in Figure 10.1 to provide support to the next layer. Capping and subgrade improvement should be continued across narrow medians. Median zones should be drained or should be filled with lean mix concrete (LMC) or an impermeable fill to prevent water accumulating and damaging the pavement edge BOXED CONSTRUCTION Boxed construction refers to a pavement structure with granular pavement layers that are not free draining other than through a subsoil drainage system. Boxed construction should only be used when no other option is possible. Pavements in cuttings are always boxed and must obey the rules given in this section. A subsoil drainage system (including lateral subsoil drains for wide verges) must be provided whenever boxed construction is used (refer to Section 6). Figure 10.1: Pavement edge support and median treatment 37

48 10.5 WET SEASON EFFECTS Designers shall consider wet season implications for construction, especially in alluvial areas likely to become saturated during the wet season. If dry season construction cannot be assured (in most cases it cannot), the design should be based on the expected subgrade condition in the wet season (Section 4) CONSTRUCTION UNDER TRAFFIC Designs requiring construction under traffic (for example, widening works) shall give due consideration to practical excavation depths and safety. Practical considerations may limit pavement types able to be used. The contract drawings may include notes describing the designers preferred work. The contractor may be permitted to propose and the Engineer to instruct or accept other solutions JOINT LOCATIONS Longitudinal joints shall not be located in wheel paths. Excavation widths for widening works shall be adjusted when necessary to comply with this rule. 38

49 CHAPTER 10: CONSTRUCTION ISSUES AND PAVEMENT PERFORMANCE 10.8 CONSTRUCTION SEQUENCE FOR RECYCLING The construction sequence must be clearly described by the drawings for recycled works involving widening of the existing pavement or reshaping. Figure 10.2(A and B) illustrates the correct widening sequence for recycling work. Traffic provisions must be decided prior to commencement of work. Lane closure will be necessary for multi-lane roads but may not be possible for two-lane treatments. Figure 10.2: (A and B) Construction sequence for recycling with widening (A) 39

50 (B) 40