RESEARCH ON IMPROVEMENT OF RUT RESISTANCE FOR ROAD

RESEARCH ON IMPROVEMENT OF RUT RESISTANCE FOR ROAD PAVEMENTS IN

DEVELOPING COUNTRIES

Final Report

FEBRUARY 2020

JAPAN INTERNATIONAL COOPERATION AGENCY (JICA)

EIGHT-JAPAN ENGINEERING CONSULTANTS INC.

INFRASTRUCTURE DEVELOPMENT INSTITUTE-JAPAN GL

JR

20-002

Research on Improvement of Rut Resistance for Road Pavements in Developing Countries

Final Report

Table of Contents

Table of Contents

List of Figure

List of Table

List of Photo

Abbreviation

Page

Outline of the Study .......................................................................................................... 1

1.1 Background and Objectives of the Study .............................................................. 1

1.2 Study Process.......................................................................................................... 2

1.3 Study Flow .............................................................................................................. 3

1.4 Contents of the Final Report ................................................................................. 4

Sorting of Improvements to the Existing Handbook ....................................................... 5

2.1 Illustrative Cases of Rutting .................................................................................. 5

2.2 Sorting of the Causes of Rutting ............................................................................ 6

2.3 Flow Rutting Countermeasures in the Existing Handbook ............................... 10

2.4 Contents of Handbook Revision ........................................................................... 13

Summarization of Findings from Hearings and Questionnaires in Japan .................. 17

3.1 Hearing Targets and Items .................................................................................. 17

3.2 Summarization of Findings in the Questionnaire to Consultants in Japan

through IDI ........................................................................................................... 22

Exchange of Opinions between Experts for the Pavement ........................................... 27

4.1 Outline of the Roundtable Meetings of Experts .................................................. 27

4.2 First Opinion Exchange Meeting (May 22, 2019) ............................................... 28

4.3 Second Opinion Exchange Meeting (January 20, 2020) ..................................... 31

Report on the Analysis within Japan ............................................................................. 34

5.1 DS value Calculation Method .............................................................................. 34

5.2 HWTD Information Collection ............................................................................. 40

5.3 Information Collection Relating to PG ................................................................ 49

5.4 Impact of High Pavement Temperature .............................................................. 52

5.5 Example of Using Modified Asphalt in JICA Gratis Projects ............................. 55

5.6 Information Collection Relating to Problem Soils and Special Soils ................. 59

5.7 Review and Comparison of Pavement Construction Management Standards

and Construction Supervision Standards.......................................................... 62

5.8 Cost Comparison between Modified Asphalt Pavement and Cement Pavement ..

............................................................................................................................... 72

5.9 Structural Analysis Using a Theoretical Design Method (Multilayer Elasticity

Theory) ................................................................................................................ 76

Results of Field Surveys (Thailand and Tanzania) ....................................................... 85

6.1 Overseas Questionnaire Surveys ......................................................................... 85

6.2 Conducting Field Surveys .................................................................................... 86

6.3 On-site Core Extraction Test ............................................................................... 87

Domestic Test Results ..................................................................................................... 99

7.1 Purpose and Overview ......................................................................................... 99

7.2 Materials Used ..................................................................................................... 99

7.3 Preliminary Tests ............................................................................................... 103

7.4 Verification Tests ................................................................................................ 105

7.5 Summary ............................................................................................................ 115

List of Figure Page

Figure 1.1 Study Schedule ........................................................................................... 2

Figure 1.2 Study Flow .................................................................................................. 3

Figure 2.1 Illustrative Cases of Deviant Gradation and Damage in Asphalt ............ 8

Figure 2.2 Outline of the Asphalt Mixture Preliminary Review System ................... 9

Figure 2.3 Structure of the Revised Handbook ......................................................... 14

Figure 5.1 Temperature Correction Coefficient Distribution Map ........................... 35

Figure 5.2 Relation between Temperature and Coefficient (Ct) ............................... 35

Figure 5.3 Comparison of Temperature Correction Coefficients .............................. 37

Figure 5.4 Verification of Temperature Correction Coefficients by Horary

Temperature and Average Temperature by Month (Overseas) .............. 39

Figure 5.5 Relationship between the Duration of the Wheel Tracking Test and

Deformation ............................................................................................. 40

Figure 5.6 Conceptual Diagram of SIP ...................................................................... 45

Figure 5.7 Grading System ........................................................................................ 49

Figure 5.8 Relationship between PG and Modified Asphalt ..................................... 51

Figure 5.9 Performance Grades of Various Binders (PG) ......................................... 51

Figure 5.10 Relationship between Pavement Temperature and Dynamic Stability . 52

Figure 5.11 Result of the WT test by Condition .......................................................... 53

Figure 5.12 Performance Grades of Various Binders (PG) ......................................... 54

Figure 5.13 Classification of Types of Modified Asphalt ............................................. 55

Figure 5.14 Thickness of an Embankment Layer of Expansive Soil of High

Expandability ........................................................................................... 60

Figure 5.15 Global Laterite Deposition Map ............................................................... 61

Figure 5.16 Conceptual Diagram of Gradations ......................................................... 67

Figure 5.17 Passed Years until Repairs ....................................................................... 74

Figure 5.18 Period until Repairs are needed (Years) .................................................. 74

Figure 5.19 Results of LCC Analysis for 4 Countries ................................................. 75

Figure 5.20 Pavement Structure Model ...................................................................... 76

Figure 5.21 Flow of Review for Pavement Composition ............................................. 83

Figure 5.22 Review of Deterioration of Asphalt Layer and Subgrade by Excel......... 83

Figure 6.1 Gradations（AC14） ................................................................................ 91

Figure 6.2 Gradations（As Base: AC20） ................................................................. 92

Figure 6.3 Gradations（Asphalt Surface: AC20） .................................................... 93

Figure 6.4 Gradations（AC14） ................................................................................ 95

Figure 6.5 Gradations（Asphalt Base）.................................................................... 96

Figure 6.6 Gradations（Asphalt Stabilized Base） .................................................. 97

Figure 7.1 Relations between Number of Gyrations and Sample Mixture Height

when Using SGC (Example) .................................................................. 107

Figure 7.2 Relations between DS and Each Parameter .......................................... 110

Figure 7.3 Relations between Rutting, Cracking and Compression Ratio ............. 111

Figure 7.4 Relations between Compression Strength (60C) and DS .................... 111

Figure 7.5 Relations between Compression Ratio and DS ..................................... 111

Figure 7.6 Relations between Final Air Void and DS .............................................. 112

Figure 7.7 The Concepts of Bulk Density and Apparent Density ........................... 113

Figure 7.8 Relations between No. of Gyrations and Bulk Void .............................. 114

List of Table Page

Table 1.1 Structure of Final Report ............................................................................. 4

Table 2.1 WT Test Results ............................................................................................ 7

Table 2.2 Procurement of Aggregate and Asphalt Mixture in JICA Projects ........... 10

Table 2.3 Composition of the Existing Pavement Construction

Supervision/Management Handbook .......................................................... 11

Table 2.4 Contents concerning Flow Rutting Countermeasures (Existing Handbook

Chapter 5) .................................................................................................... 12

Table 2.5 Part 1: Reinforcement Points in Survey/Design ........................................ 14

Table 2.6 Part 2: Reinforcement Points in Construction Supervision/Management

...................................................................................................................... 15

Table 3.1 Targets and Contents of Hearings ............................................................. 17

Table 3.2 Main Opinions Ascertained in Hearings .................................................... 18

Table 3.3 Illustrative Cases of Issues in the Field Voiced by Pavement Companies

...................................................................................................................... 21

Table 3.4 Questionnaire Items ................................................................................... 22

Table 3.5 Concerning Existence and Experience of Using the “Existing Handbook”

...................................................................................................................... 23

Table 3.6 Points where Troubles or Difficulties have arisen in Applying the

“Existing Handbook” ................................................................................... 23

Table 3.7 Points that are considered to Require Improvement and/or Reinforcement

in the “Existing Handbook” ......................................................................... 24

Table 3.8 Other Points Noticed or Requests in the “Existing Handbook” ................ 26

Table 3.9 Other Requests concerning the “Existing Handbook” in General ............ 26

Table 4.1 Opinion Exchange Meeting Members ........................................................ 27

Table 4.2 Main Opinions in the First Meeting .......................................................... 28

Table 4.3 Main Opinions in the Second Opinion Exchange Meeting ....................... 32

Table 5.1 Comparison of Temperature Correction Coefficients by Location ............ 36

Table 5.2 Verification of Temperature Correction Coefficients by Hourly

Temperature and Average Temperature by Month (Japan) ...................... 38

Table 5.3 Verification of Temperatures by Using Temperature Correction

Coefficients (Typical Places in Developing Countries) ............................... 38

Table 5.4 Comparison of WT Test Methods ............................................................... 41

Table 5.5 Comparison between the Threshold Values of BS Wheel Tracking Test

and the Japanese Standard ........................................................................ 42

Table 5.6 Comparison of DS Standard Values of Japan ............................................ 43

Table 5.7 Comparison of HWT Test Methods ............................................................ 44

Table 5.8 Standards of Evaluation Performed by Using HWT Tests (Tex-242-F) ... 45

Table 5.9 Standards of Evaluation Performed by Using HWT Test (South Africa) . 45

Table 5.10 Types of Straight Asphalt ........................................................................... 49

Table 5.11 Asphalt Assessment Tests in PG ................................................................ 50

Table 5.12 Correction of PG Considering the Traffic Condition ................................. 50

Table 5.13 Conditions of the WT test conducted for Mixtures ................................... 53

Table 5.14 Test Conditions ........................................................................................... 54

Table 5.15 Standards of Asphalt Softening Points ...................................................... 54

Table 5.16 Classification of Modified Asphalt Types within Japan ............................ 56

Table 5.17 Classification of Modified Asphalt Types within Japan ............................ 58

Table 5.18 Expansive Soil Judgment Standards in Australia .................................... 59

Table 5.19 Material Standard in Australia (Victoria) ................................................. 60

Table 5.20 Criteria Recommended for a Laterite Base Ccourse ................................. 61

Table 5.21 Outline of Base Course Specifications of 13 African Counties ................. 61

Table 5.22 Examples of Martial Standards (ORN31) ................................................. 62

Table 5.23 Examples of Granular Material Standards (ORN31) ............................... 63

Table 5.24 Examples of Material Standards (Pavement Design Handbook/Pavement

Construction Handbook) ............................................................................ 64

Table 5.25 Examples of Material Standards (SATCC) ................................................ 64

Table 5.26 Examples of Asphalt Mixture Materials (1) .............................................. 65

Table 5.27 Examples of Asphalt Mixture Materials (2) .............................................. 66

Table 5.28 Type of Mixture and Gradations ................................................................ 68

Table 5.29 Ramming Compaction Test ........................................................................ 69

Table 5.30 Ramming Compaction Test (Standard Method and Modified Method) .... 69

Table 5.31 Examples of Degree of Compaction Specifications (Standard Method)

(Australia) .................................................................................................. 70

Table 5.32 Examples of 100% or Higher Specified Compaction (Modified Method) .. 70

Table 5.33 Permissible Deviate Gradations (Examples) ............................................. 71

Table 5.34 Examples of Expense Items Included in Pavement Life Cycle Costs ...... 73

Table 5.35 Direct Construction Expenses by Pavement Type .................................... 73

Table 5.36 Structural Design Condition Setting Items............................................... 76

Table 5.37 Pavement Damage Load Reference Values ............................................... 77

Table 5.38 Elastic Modulus and Poison’s Ratio of the Material Used for Each

Pavement Layer ......................................................................................... 77

Table 5.39 Example of Structural Review Using Theoretical Design Method (1) ..... 80

Table 5.40 Example of structural Review Using Theoretical Design Method (2) ...... 82

Table 6.1 Countries that Participated in the Questionnaire Survey ........................ 85

Table 6.2 Mixing Test Methods Currently Applied ................................................... 85

Table 6.3 SUPERPAVE Application Track Records ................................................... 85

Table 6.4 Countries Visited for the Field Surveys ..................................................... 86

Table 6.5 Test Items .................................................................................................... 88

Table 6.6 Core Sampling Positions ............................................................................ 88

Table 6.7 Comparison of AC14 (Surface) ................................................................... 91

Table 6.8 Comparison of AC20 (As Base) ................................................................... 92


Table 6.10 Core Sampling Positions ............................................................................ 94


Table 6.12 Comparison of As Base ............................................................................... 96

Table 6.13 Comparison of As Stabilization .................................................................. 97

Table 7.1 Test items for Materials Used .................................................................. 100

Table 7.2 Aggregate Used ......................................................................................... 100

Table 7.3 Asphalt Used (Straight Asphalt 40/60) .................................................... 101

Table 7.4 Asphalt Used (Straight Asphalt 60/80, 80/100, Modified Type II) .......... 102

Table 7.5 Preliminary Test Mixtures ....................................................................... 103

Table 7.6 Preliminary Test Mixtures ....................................................................... 103

Table 7.7 Preliminary Test Results .......................................................................... 104

Table 7.8 Comparison of the Values of the Various Characteristics by Parameter 104

Table 7.9 Degree of the Effect on Characteristics by the Various Parameters ...... 105

Table 7.10 Verification Test Mixtures ........................................................................ 106

Table 7.11 Verification Test Items .............................................................................. 106

Table 7.12 Compaction Energy of the Superpave Gyratory Compactor ................... 108

Table 7.13 Verification Test Results ........................................................................... 109

Table 7.14 Verification Test Results (SGC Compaction Tests) ................................. 109

Table 7.15 Correction Factor and bulk void .............................................................. 114

List of Photo Page

Photo 1.1 Typical Example of Rutting (Ethiopia) ........................................................ 1

Photo 2.1 Flow Rutting (Flat Section) National Trunk Road (Tanzania) ................... 5

Photo 2.2 Flow Rutting (Tropical Area and Steep Gradient) International Trunk

Road (Ethiopia) ............................................................................................ 5

Photo 2.3 Flow Rutting (Mountainous Section and Steep Gradient) International

Trunk Road (Ethiopia) ................................................................................. 5

Photo 2.4 Flow Rutting (Mountainous Section and Steep Gradient)International


Photo 2.5 Flow Rutting (Mountainous Section and Steep Gradient) International


Photo 2.6 Flow Rutting (Flat Section, Approach to Pedestrian Crossing)

International Trunk Road (Tanzania) ......................................................... 6

Photo 2.7 Structural Rutting (Flat Section, Problem Soil) Urban Trunk Road

(Other Donor, Ethiopia) ............................................................................... 6

Photo 2.8 Rutting Rapid Increase in Traffic Volume (ESAL) (Tanzania) ................. 15

Photo 2.9 Rutting Impermissible High Temperature (Ethiopia) .............................. 15

Photo 2.10 Alligator Crack & Pot Hole: Poor Subsurface Drainage Design (Ethiopia)

...................................................................................................................... 15

Photo 2.11 Alligator Crack Inadequate Cemented Base (Tajikistan) ........................ 15

Photo 2.12 Subbase that Lost Bearing Capacity Improper Material (Laos) .............. 15

Photo 2.13 Pot Hole caused by Problem Soil (Cambodia) ........................................... 15

Photo 2.14 Rutting Unsuitable Material (Aggregate) (Tanzania) .............................. 16

Photo 2.15 Rutting Unsuitable Mix Design (Ethiopia) ............................................... 16

Photo 2.16 Rutting Inadequate As Plant Management (Zambia) .............................. 16

Photo 2.17 Slippage on Cemented Base Faulty Workmanship (Tajikistan) .............. 16

Photo 2.18 Slippage on Existing As Layer Faulty Workmanship (Tanzania) ............ 16

Photo 4.1 The First Opinion Exchange Meeting ....................................................... 30

Photo 4.2 The Second Opinion Exchange Meeting .................................................... 33

Photo 5.1 State where Asphalt Flowing Out ............................................................. 55

Photo 5.2 Example of PMB Manufacturing Plant based on Grant Aid (Liberia) ..... 57

Photo 6.1 New Bagamoyo (Shule) .............................................................................. 88

Photo 6.2 New Bagamoyo (Goigi) ............................................................................... 88

Photo 6.3 Tazara Jct. .................................................................................................. 89

Photo 6.4 Morogoro Road (Bucha) .............................................................................. 89

Photo 6.5 Morogoro Road (Shekilango) ...................................................................... 89

Photo 6.6 Core Sampling（New Bagamoyo） ........................................................... 89

Photo 6.7 Core Sampling（Morogoro Bucha） .......................................................... 89

Photo 6.8 Core Samples（Morogoro Bucha） ............................................................ 89

Photo 6.9 Tazara Jct.New ........................................................................................... 90

Photo 6.10 Morogoro Road (Shekilango) ...................................................................... 90

Photo 6.11 New Bagamoyo (Goigi). .............................................................................. 90

Photo 6.12 Morogoro Road (Bucha).............................................................................. 90

Photo 6.13 Bagamoyo (Shule) ...................................................................................... 90

Photo 6.14 Modified Part（Rutting） .......................................................................... 94

Photo 6.15 Modified Part (Damage) ............................................................................. 94

Photo 6.16 Straight Asphalt Damaged in the Most Central Lane ............................. 94

Photo 6.17 Core Sampling (Damaged Position) .......................................................... 94

Photo 6.18 Core Sampling (Fair Position) ................................................................... 94

LIST OF ABBREVIATION Abbreviation Description

AASHTO American Association of State Highway and Transportation Officials

AC Asphalt Concrete

ACV Aggregate Crushing Value

AFCAP Africa Community Access Programme

AI Asphalt Institute

As Asphalt

ASTM American Society for Testing and Materials

BBR Bending Beam Rheometer

BS British Standard

CBR California Bearing Ratio

COLTO Committee of Land Transport Officials

CSIR The Council for Scientific and Industrial Research

DCP Dynamic Cone Penetration Test

DFR Draft Final Report

DTT Direct Tension Tester

DOH Department of Highways

DS Dynamic Stability

DSR Dynamic Shear Rheometer

EN European Norm（European Standards）

ESAL Equivalent Standard Axle Loads

ESWL Equivalent Standard Wheel Load

FR Final Report

FWD Falling Weight Deflectmeter

GC Gyratory Compactor

GTM Gyratory Test Machine

HP Home Page

HWTD Hamburg Wheel Tracking Device

ICR Inception Report

IDI Infrastructure Development Institute

JICA Japan International Cooperation Agency

JIS Japanese Industrial Standards

JMF Job Mix Formula

LCC Life Cycle Cost

LCPC Laboratoire Central des Ponts et Chaussées

MA Multi Asphalt

Abbreviation Description

MDD Maximum Dry Density

NEXCO Nippon Expressway Company Ltd.

OAC Optimal Asphalt Content

ODA Official Development Assistance

OL Overlay

OMC Optimum Moisture Content

ORN Overseas Road Note

PAV Pressure Aging Vessel

PG Performance Grade

PMB Polymer Modified Bitumen

PRR Progress Report

RTFO Rolling Thin Film Oven

RV Rotational Viscometer

Sabita Southern African Bitumen Association

SAMDM South African Mechanistic -Empirical Design Method

SATCC Southern Africa Transport and Communication Commission

SBS Styrene-Butadiene-Styrene

SGC Superpave Gyratory Compactor

SHRP Strategic Highway Research Program

SIP Stripping Infection Point

StAs Straight Asphalt

TA Total Asphalt

TFV Ten Percent Fine Value

TRH Technical Recommendations for Highways

TRRL Transport and Road Research Laboratory

VFA/VFB Percent of Voids Filling with Asphalt/Bitumen

VIM Volume of air Voids / Voids in Mix

VMA Voids in Mineral Aggregates

WT Wheel Tracking

WTD Wheel Tracking Device

WTR Mean Wheel Tracking Ratio

WTS Wheel Tracking Slope


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1. Outline of the Study

1.1 Background and Objectives of the Study

(1) Background of the Study

The Government of Japan’s overseas development assistance, comprising mainly loan aid, grant aid and technical cooperation, has consistently focused on supporting infrastructure development while contributing to economic infrastructure and human resources development. In particular, since road infrastructure accounts for an overwhelmingly large share of transportation in developing countries, Japan has so far implemented numerous assistance exemplified by road construction and improvement projects with a view to realizing effective and efficient road transportation.

Many developing countries have unique weather conditions (temperature, rainfall) and, consequently, distinctive soil conditions; moreover, road conditions (driving manners, large vehicle ratio, axle load management, etc.) are harsher than in Japan. The construction environment also presents differences: construction firms autonomously implement materials management and mix design from the aggregate stage to asphalt composite materials, and maintenance work also cannot be implemented with the same frequency or on the same level. As a result, after roads go into service, there are numerous cases where pavement experiences troubles and damage that couldn’t be assumed at the time of design.

In these circumstances, Japan International Cooperation Agency, in fiscal 2016, implemented the “Study (Basic Research) on Pavement Construction Supervision/Management in Developing Countries” (hereafter referred to as the “pre-existing basic research”). In this, it sorted the applicability of Japanese pavement design standards in developing countries, examined the issues and important points to consider regarding road pavement according to design standards, operation of standards, survey of natural conditions and so on, and compiled a handbook for future road projects. However, this failed to present adequate solutions to a number of issues. Moreover, to implement construction in the environmental conditions of various countries around the world, since it was necessary to reflect the latest knowledge especially concerning rutting countermeasures, it became necessary to revise the handbook to facilitate its use in practical work.

(2) Objectives of the study

This work entails implementing various tests and studies with a view to revising the “Construction Supervision/Management Handbook” that was compiled based on the pre-existing basic research, in order to facilitate its use in practical work, with the goal of improving the quality of road projects in developing countries. In particular it focuses attention on flow rutting (hereafter referred to as rutting), which is a major issue regarding road pavement in developing countries. Upon surveying, analyzing and testing countermeasures that are adopted in Japan and other countries, the findings

Source: JICA Study Team

Photo. 1.1 Typical Example of Rutting (Ethiopia)


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will be compiled into a handbook intended for JICA officials, project consultants and contractors, augmenting and supplementing the contents of the pre-existing basic research.

1.2 Study Process

Figure 1.1 shows the final schedule of the study following revision based on the opinion exchange meeting by experts for the pavement, additional domestic test, situation regarding the analysis work in Japan and so on.


Figure 1.1 Study Schedule


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1.3 Study Flow

This study was carried out according to the flow shown in Figure 1.2. As the first step, the points to be improved of the existing handbook based on the results of interviews with consultants and construction companies conducted in the related survey were summarized. Subsequently, a questionnaire survey on the specific handbook revision was conducted, and the composition of the revised handbook was decided through a meeting for exchanging opinions with key experts.

Finally, the revised handbook, which reflected hearings on countermeasures against rutting for persons involved in JICA road projects, domestic analysis, field survey results, etc., was finalized based on the opinion exchange meeting by experts.


Figure 1.2 Study Flow

Collection and review of past road pavement construction plans and construction supervision plans

Hearings about quality control methods, etc. in asphalt plants and crushedstone plants in Japan

Collection, review and comparison of pavement construction management standards and construction

Extraction of problems and important points in roadpavement construction

Finalization of proposed draft improvements to the Handbook

First Roundtable Meeting of Experts

Extraction of problems and important points in roadpavement construction

Creation of proposed improvements to the Handbook created in the pre-existing basic research

Examination of tests in Japan (draft)

Re-consigning and implementation of tests in Japan

Implementation of overseas preliminary questionnaire Implementation of JapanRoad Contractors Association preliminary questionnaire Analysis in JapanMethod for setting DS value in tropical countries Examination of measures to address high DS values Information collection in Japan (WT test, HWT test, PG, etc.)

Creation of draft Handbook revisionCreation of Draft Final Report

Examination of site survey areas and contents

Second Roundtable Meeting of Experts

Handbook finalizationCreation of Final Report

PRRStart of July

Start of survey work

ICREnd of March

DFREnd of

January

FREnd of

February

First Japan Road Contractors Association and Infrastructure

Analysis of overseas preliminary questionnaire Analysis in JapanMethod for setting DS value in tropical countries Examination of measures to address high DS value Information collection in Japan Selection (draft) of pavement structure based on lifecycle cost Etc.


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1.4 Contents of the Final Report

The structure of the final report of this study is shown in Table 1.1.

Table 1.1 Structure of Final Report

Chapter Title Contents

1 Outline of the Study The purpose of the study, the content of the study, the study flow, etc. are explained.

2 Sorting of Improvements to the Existing Handbook

The contents and issues of the previous handbooks are summarized, and the structure and reinforcement points of the revised handbook are described.

3 Summarization of Findings from Hearings and Questionnaires in Japan

The results of interviews with related companies for the existing handbooks and the results of questionnaires to consultants regarding requests for the revised handbook are described.

4 Exchange of Opinions between Experts for the Pavement

The proceedings of the Expert Opinion Exchange Meeting, the contents of the consultation, and a summary of the opinions issued are described.

5 Report on the Analysis within Japan

For the revision of the handbook, examples and data collected, analysis, etc. in domestic works are described.

6 Results of Field Surveys (Thailand and Tanzania)

Hearing results and core sampling test results from the field survey in Thailand and Tanzania are described.

7 Domestic Test Results The results of domestic tests on rutting resistance conducted in this study are described.



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2. Sorting of Improvements to the Existing Handbook

2.1 Illustrative Cases of Rutting

Rutting is road deformation in the longitudinal direction cause by the load of vehicle wheels. This is primarily divided into two types.

(1) Flow rutting

Deformation of asphalt mixture is predominantly caused by the blend of asphalt mixture (gradation, type and quantity of binder, etc.) and the external factors of traffic load and temperature. Consequently, it is commonly observed on roads in relatively warm regions that have a lot of heavy-vehicle traffic. Flow rutting is primarily caused by fluidity (plastic deformation) of asphalt mixture arising from high temperatures and heavy-vehicle traffic. Flow rutting is characterized by rutting in the running position of tires and bulging on the outside of ruts.

Illustrative Cases

Photo 2.1 Flow Rutting (Flat Section) National Trunk Road (Tanzania)

Photo 2.2 Flow Rutting (Tropical Area and Steep Gradient)

International Trunk Road (Ethiopia)

Photo 2.3 Flow Rutting (Mountainous Section and Steep Gradient)





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Photo 2.6 Flow Rutting (Flat Section, Approach to Pedestrian Crossing)

International Trunk Road (Tanzania) Source: JICA Study Team

(2) Rutting caused by settlement of subgrade and base/subbase

Rutting that arises from settlement of subgrade and base/subbase is caused by the deterioration of bearing capacity in the subgrade and base/subbase due to the impact of groundwater, etc., lack of sufficient base/subbase compaction, and imparting of excessive traffic load on the pavement structure. The following illustrative cases show settlement rutting caused by “expansive soil”, which is regarded as a type of problem soil.

Illustrative Cases

Photo 2.7 Structural Rutting (Flat Section, Problem Soil)

Urban Trunk Road (Other Donor, Ethiopia)


2.2 Sorting of the Causes of Rutting

(1) External factors (factors that should mainly be addressed during design)

Flow rutting in developing countries is especially caused by large vehicle traffic (overloaded vehicles, etc.), while the impact of road surface temperature is also large. In developing countries, since trucks and other transport vehicles are loaded to capacity, their travel speed sometimes becomes excessively slow, and damage to asphalt pavement happens quicker than expected in


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places where there is a concentration of such large-size slow-moving traffic. Moreover, in areas of Asia and Africa that have high annual average temperatures, higher road surface temperatures lead to decline in the elastic coefficient of the asphalt mixture, which in turn leads to fluidization. Such causes can be summarized as external factors as shown below.

Traffic load … Large vehicle traffic volume, axle load, tire grounding pressure Road conditions … Speed reduction, braking, etc. (traffic congestion, areas around

intersections, etc.)

In developing countries, travel speeds sometimes become excessively low because poorly maintained trucks, etc. are loaded to capacity. In places where numerous such large-size slow-moving vehicles pass, damage caused by flow rutting occurs faster than expected. Concerning plastic deformation, it is possible to ascertain the impacts based on the wheel tracking (WT) test. Table 2.1 compares the impacts on pavement in terms of dynamic stability of traffic conditions assuming the cases of heavy vehicles and slow-speed vehicles.

Table 2.1 WT Test Results Asphalt content

(%)

Projected conditions

Vertical Load Test speed* (rpm)

Dynamic stability (DS) (rpm) Test wheel load

(KN) Contact pressure

(MPa)

5.3

Standard 686 0.63 42 492 Heavy vehicles

980** (approx. 1.4times) 0.90 42 348

Low speed vehicles 686 0.63 21 (0.5 times) 294

*Travel speed: Loaded travel speed is prescribed as traveling at a uniform speed over a section of 22cm in the centre of the specimen, and the reference value is given as 42±1 times/minute. This value is the test standard given by the British RRL (Road Research Laboratory). ** Test device threshold value Source: How to Approach Road Construction and Improvement Planning through Loan Aid Projects in Africa (Ethiopia, Ghana, Tanzania), March 2011

According to these test results, the rate of deformation (RD) in case 1) where the vertical load is assumed to be 1.4 times (0.63Mpa→0.90Mpa) is approximately 1.4 times greater (0.085mm/min→0.121mm/min), indicating that the rate of deformation is proportional to the vertical load. In case 2) where the travel speed is reduced to half (161.0mm/sec→80.5mm/sec), the test wheel loading time is doubled (0.14sec→0.27sec), however, the rate of deformation (RD) increases by approximately 1.7 times (0.085mm/min→0.143mm/min). This test clearly indicates that deformation in asphalt pavement is influenced by the size of load and the travel speed.

Natural conditions … Changes in air temperature and temperature of the pavement, and rainfall: When the road surface temperature is continuously measured to be 45°C or more for an accumulated time of 100 hours, the amount of rutting increases suddenly.

Pavement structure … Thickness of the asphalt layer, type of base/subbase

(2) Internal factors (factors that are mainly addressed in construction)

In addition to the above external factors, the following internal factors (factors that are mainly addressed in construction) can also be considered.

Asphalt … Hardness, temperature sensitivity, use of modifying material Aggregate (materials)… Hardness, coarseness of texture, angularity (shape)

Mix design…Gradation, asphalt content, air void, voids filled with asphalt (VFA), etc.


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As has been revealed by past test results, “deviation from stipulated gradation” of asphalt mixture imparts a major impact on the properties of asphalt mixture. Below are indicated illustrative cases from of road asphalt sampling core confirmation tests in Africa, and these clearly show that there is a relationship between the degree of deviation from stipulated gradation and pavement damage (predominantly rutting). The actual conditions of damage are as shown in Figure 2.1.


Figure 2.1 Illustrative Cases of Deviant Gradation and Damage in Asphalt

The noteworthy thing here is the clear relationship between the deviation degree of gradation and the damage ratio. The gaps between the pavement aggregate have not been estimated or calculated here, however, in Figure 2.1, a), it is possible that the presence of a high ratio of fine particles led to insufficient meshing of the aggregate, which in turn led to the destruction. This indicates that the gradation or the meshing of aggregate is an important factor in the occurrence of rutting.

Concerning this “deviation from stipulated gradation”, the Japan Road Contractors Association’s “Asphalt mixture preliminary review system” is utilized in Japan, and stringent quality control is conducted based on “in-company work standards” for autonomous management in major plants. Accordingly, this system ensures that the management standards required by clients are almost entirely satisfied.


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Asphalt mixture preliminary review system

In Japan, the asphalt mixture preliminary review system is predominantly used with the objective of rationalizing quality control and stabilizing quality in asphalt plants in public works projects. Through this system, which entails having a third party agency (an asphalt mixture review committee comprising representatives from government, academia and private sector: the Road Management Technology Centre) certify asphalt mixture produced by asphalt plants in advance, makes it possible to abbreviate the standard tests (including mix design, etc.), batch trial and so on that had been conducted for each pavement work. However, NEXCO, which conducts a large volume of pavement works, does not use this system because it often establishes independent plants for each works project.


Figure 2.2 Outline of the Asphalt Mixture Preliminary Review System

Moreover, in the developing countries where JICA projects are implemented, since the division of labor system like that seen in Japan is not adopted, construction firms often implement all work processes from production of aggregate and asphalt mixture to plant management and construction management. Accordingly, gradation management, etc. must be implemented on works sites, and this is something that is not experienced in Japan.

Review agency(third party agency)

(Review certification)

Preliminary review committeeOn-the-spot

survey committee

Client

Contractor Manufacturer

Autonomous management

(Work standards)

[Copy of certificate]

(Order)

(Ordering)(Designation)

[Certificate]Quality System

(Confirmation) [Copy of certificate]


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Table 2.2 Procurement of Aggregate and Asphalt Mixture in JICA Projects

Project Country Aggregate

procurement Asphalt mixture

procurement The Project for Rehabilitation of National Route 1 Cambodia Own company

(subcontracting) Own company (subcontracting)

The Project for Improvement of National Road 9 as the East-West Economic Corridor of the Mekong Region

Laos Own company production

Own company production

The Project for Rehabilitation of the Outer Bangkok Ring Road (National Route 9) Thailand Local purchasing Local purchasing

Project for Improvement of Dusty-Nizhniy Pyandzh Road Tajikistan Local purchasing Own company

production The Project for Rehabilitation of Trunk Road, Phase 3 and Phase 4 Ethiopia Own company

production Own company production

Kilwa Road Widening Project Tanzania Local purchasing Own company production

New Bagamoyo Road Widening Project Tanzania Own company (subcontracting)

Own company (subcontracting)

The Project for Improvement of Livingstone City Road Zambia

Local purchasing/Own company production


The Project for Improvement of the Living Environment in the Southern Area of Lusaka Zambia Own company


The Project for Rehabilitation of Trunk Road N8 Ghana Own company


The Project for Reconstruction of Somalia Drive in Monravia Liberia Own company


The Project for Dualling of Nairobia-Dagoretti Corner Road Kenya Own company


The Project for Improvement of Tazara Intersection Tanzania Own company


The Project for Rehabilitation of National Route 1 Inner City Section The Project for Rehabilitation of National Route 1 (Phase 4)

Cambodia Own company (subcontracting)

Own company (subcontracting)

The Project for Dualling of Nairobia-Dagoretti Corner Road (Phase 2) Kenya Own company


The Programme for Improvement of Ghanaian International Corridors (Tema Motorway Roundabout)

Ghana Local purchasing Own company production

The Project for Improvement of Gulu Municipal Council Roads Uganda Own company


The Project for Reconstruction of Somalia Drive in Monravia (Phase 2) Liberia Own company


Project d’Aménagement de l’échangeur d’amitié ivoiro-japonaise (Phase 2) Cote d’Ivoire Own company


Kukum Highway Upgrade Project Solomon Islands




2.3 Flow Rutting Countermeasures in the Existing Handbook

(1) Objectives and composition of the existing Handbook

Under the aforementioned circumstances, there have been cases where the occurrence of unexpected troubles and damage has impeded traffic functions. Early damage of pavement is often caused by not only lack of investigation and examination in the design stage, but also construction

https://www.jica.go.jp/activities/schemes/grant_aid/state/ku57pq00001spovn-att/result2015_03.pdf


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and quality control issues during works (plant operation with loose quality control based on systems that are different from in Japan, use of defective raw materials, etc.). Accordingly, in an effort to prevent the reoccurrence of such cases, the “Handbook for Pavement Construction Supervision/Management in Developing Countries (Draft)” provides information on the roles of consultants and contractors concerning construction supervision and management of pavement works in road pavement projects (grant aid projects) and management of raw materials and base/subbase construction in the first half (Chapters 1 to 3), and describes illustrative cases of pavement damage, the main causes of damage, caution points and proposals for countermeasures in the second half (Chapters 4 to 7).

Table 2.3 Composition of the Existing Pavement Construction Supervision/Management Handbook

Item Main Text Composition Attached Materials Construction supervision/management

1. General matters related to construction supervision and management

Attachment-1 Pavement Construction Supervision and Construction Management

Construction supervision 2. Pavement construction supervision

Construction management

3. Pavement works construction management

Management system, etc.

(1) Pavement construction management

Materials management

(2) Materials procurement and testing

Mix design

(3) Mix design and testing Attachment-2 Mix Design Method in Japan Attachment-3 Mix Design Method based on Gyratory Compactor

Base/subbase construction

(4) Base/subbase construction management

Asphalt construction

(5) Asphalt mixture pavement management

Damage illustrative cases and main causes

4. Illustrative cases of asphalt pavement damage

Flow rutting

5. Flow rutting countermeasures Causes of damage

(1) Causes of flow rutting

Mix design

(2) Important points to consider in mix design

Attachment-4 Flow Rutting Countermeasures in Each Country Attachment-5 Impact of Temperature on Dynamic Stability

Performance experiments

(3) Comparative experiments for various performance

Attachment-6 Comparative Experiments for Various Performance Attachment-7 Evaluation of Asphalt Mixture based on WT Test

Quality control

(4) Important points to consider in plant management

Cement stabilization

6. Important points to consider in cement stabilization

Causes of damage

(1) Causes of damage in cemented base

Quality control

(2) Important points to consider in cemented base

Attachment-8 Groundwater Level and Base/Subbase Drainage

problem soil

7. Problem soil countermeasures Causes of damage

(1) Causes of damage caused by problem soil

Quality control

(2) Problem soil countermeasures



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(2) Flow rutting countermeasures, etc. in the existing Handbook

In the existing Handbook, Chapter 4 describes illustrative cases of damage in asphalt pavement; Chapter 5 describes flow rutting countermeasures; Chapter 6 describes the important points to consider regarding cement stabilization; and Chapter 7 describes problem soil countermeasures. In Chapter 5, the following kind of contents are stated regarding flow rutting countermeasures.

Table 2.4 Contents concerning Flow Rutting Countermeasures (Existing Handbook Chapter 5)

5．Flow rutting countermeasures

(1) Causes of flow rutting

In recent years, in grant aid projects for roads, due to the rapid increase of traffic volume, in particular a preponderance of large-size vehicles and overloaded vehicles, more and more pavement damage is being seen. Many of the pavement troubles arising in construction (including materials) comprise flow rutting. Since causes of flow rutting in asphalt mixture are often the asphalt mixture blend (gradation, type and asphalt content, etc.) and external factors such as traffic load and temperature, flow rutting occurs on roads in tropical countries that have high road surface temperatures and a lot of heavy-vehicle traffic. Such damage to asphalt pavement is caused not only by discrepancies between actual conditions and the conditions assumed in design (unlawful overloaded vehicles, slow-speed traveling of vehicles, etc.), but also by inappropriate mix design, inferior quality construction (use of defective materials, inappropriate plant management, etc.) and so on. However, even tropical countries of Asia and Africa have highland cold regions. In these places, in addition to flow rutting countermeasures, it is necessary to also consider measures to address cracking like in Japan.

(2) Important points to consider in mix design

Mix design refers to the process of selecting aggregate and deciding the type and asphalt content to ensure that asphalt mixture exhibits its specified performance. In Japan, not much attention is paid to the selection of aggregate, however, in developing countries, this is another major determinant. As flow rutting countermeasures, attention must first be given to the mix design. The conventional approach to mix design is based on the Marshall mix design method, however, other approaches include the Superpave system in the United States, the volumetric design method using gyratory compactor in Australia and so on. In the method based on the Marshall mix design method, it is effective to observe the important points to consider regarding mix design that are stated in the “Pavement Construction Handbook”. Moreover, in tropical countries and other areas that are subject to high road surface temperatures for extended periods, it is also effective to ascertain the flow property resistance (Dynamic stability: DS) of asphalt mixture based on Marshall stability test and wheel tracking (WT) test. At these times, the target Ds value is set upon taking the ESAL value, travel speed, air temperature, economy, etc. into account. When designing pavement road surface, considering the asphalt procurement situation, etc. in developing countries, the basic approach is to adopt straight asphalt from the viewpoint of economy, however, on sections where it is deemed unfeasible to apply straight asphalt, modifying material is added or modified asphalt is used. When designing mix, out of standard mixtures, the scope of gradation ranging from dense graded asphalt and dense graed gap asphalt is referred to. In countries that have widely disseminated standards concerning porosity, etc. concerning gyratory compactors, it may be required to conduct mix design in accordance with such standards.

(3) Comparative experiments of mix design performance

To ascertain the influence of gradation, porosity, and asphalt content in relation to flow rutting countermeasures, Marshall stability test, wheel tracking (WT) test, and confirmation of final porosity based on gyratory compactor were implemented. The findings were as follows: As a result of testing with the focus on grading deviation, which hinders the

meshing of aggregate and leads to deterioration of flow property resistance, it was found that deviation in the fine particle ratio (increase) causes the flow property resistance to decline greatly. In particular, it was confirmed that gradation management of fine aggregate during plant mixing is especially important from the viewpoint of ensuring flow property resistance.

It was confirmed that the asphalt content has a major impact in terms of increasing flow property resistance.

The flow property resistance can be enhanced by reducing the asphalt content


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5．Flow rutting countermeasures (over the extent that doesn’t detract from the ease of construction).

As a result of comparing findings obtained from the WT test (DS value) and findings obtained from using the gyratory compactor (final porosity), it was possible to ascertain the correlation between degree of final porosity and flow property resistance (dynamic stability: DS), indicating that final porosity is effective for adjudicating flow property resistance.

The question of how much of a DS value can be obtained through straight asphalt is important from the viewpoint of economy. In this test, a high value of 3250 times/mm was obtained, and this is worth researching further in the future.

(4) Important points to consider in plant management

Rutting of asphalt pavement is triggered by inappropriate plant management, etc. In other words, even if mix design is appropriately implemented, defective asphalt mixture will still be produced if plant management is not conducted properly. In grant aid projects, since it is usually necessary for the Japanese consultant and contractor to autonomously conduct plant management, the important points to consider in plant management are stated. Cases of troubles in plant facilities in grant aid projects are described together with the important points to consider in countermeasures. After that, countermeasures and important points to consider are stated for cases where problems arise concerning the gradation, asphalt content, and manufacturing temperature.


Out of the above, improvement and reinforcement are deemed to be necessary on the underlined parts for the following reasons.

The importance of materials management is recognized, however, there is a lack of specific information regarding specific quality control standards for materials and mixture in asphalt plants.

Concerning calculation of the necessary DS value, adequate solutions are not presented for issues regarding the method of calculation, method of use and so on.

Overseas, in both advanced nations and also some developing countries, standardization is being advanced concerning the mix design method using gyratory compactor. Moreover, it is necessary to reflect new knowledge concerning methods for evaluating mixture (WT test, HWT test) both in Japan and overseas.

Since it is difficult to secure modifying material, some countries try to achieve flow property resistance through use of straight asphalt, however, it is necessary to sort know-how concerning the DS value that can be secured by this approach.

No information or knowledge are presented concerning methods for procuring and manufacturing modifying material in cases where such material is used.

Methods and approaches for conducting pavement diagnosis and identifying causes of damage are not indicated.

It is necessary to translate the text into English so that it can be used as a tool for engineers in overseas road projects.

2.4 Contents of Handbook Revision

Based on the information obtained in this study, for the reasons described above, the existing ”Pavement Construction Supervision/Management Handbook” will undergo complete revision and be issued as the “Revised Pavement Construction Supervision/Management Handbook”. The, “Revised Pavement Construction Supervision/Management Handbook” has the composition shown in Figure 2.3, with the main reinforced points being the contents shown in Table 2.5 and 2.6.


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Figure 2.3 Structure of the Revised Handbook

Table 2.5 Part 1: Reinforcement Points in Survey/Design

Main Issues Handbook Contents

Rapid increase in traffic volume and ESAL higher than expected

Implementation of demand forecast taking risks of switching traffic volume and economic growth into account; and adoption of appropriate design period taking the local maintenance situation, etc. into account.

Flow rutting arising from high temperature

Adoption of an appropriate indicator (DS: Dynamic Stability) taking air temperature, load and road structure into account, and improvement of mixture functions based on use of modifying material, etc. Introduction of mixture evaluation testing based on WT.

Pavement structural design and checking

Concerning calculation of subgrade strength in the depth direction, verify based on Japanese standards. State thinking related to the application threshold of each standard and the improved subgrade (capping layer). Implement checking of pavement structure based on multilayer elastic theory, etc.

Pavement drainage design (base drainage)

Application of base drainage as adopted primarily in Europe and America.

Cement stabilized base Avoid the adoption of cement stabilized base. If there is no other choice but to adopt it, state the case of adopting an asphalt layer of 150 mm or more and other illustrative cases.

Decline in bearing capacity of cement stabilized subbase

Selection of appropriate materials (e.g. PI≦9)

Pavement damage caused by problem soil

Dispersive soil: Adoption of the construction method that entails, for example, installing an impervious layer (road shoulder, etc.) that has reduced percolation due to use of cement-mixed soil or good quality soil. Expansive soil: Water shielding, replacement, installation of an impervious layer, lime stabilization, adoption of waterproof sheet.



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Photo 2.8 Rutting Rapid Increase in Traffic Volume

(ESAL) (Tanzania)

Photo 2.9 Rutting Impermissible High

Temperature (Ethiopia)

Photo 2.10 Alligator Crack & Pot Hole: Poor Subsurface Drainage Design (Ethiopia)

Photo2.11 Alligator Crack Inadequate Cemented Base

(Tajikistan)

Photo2.12 Subbase that Lost Bearing Capacity

Improper Material (Laos)

Photo2.13 Pot Hole caused by Problem Soil

(Cambodia) Source: JICA Study Team

Table 2.6 Part 2: Reinforcement Points in Construction Supervision/Management Main Issues Handbook Contents

Inappropriate materials (aggregate particle shape)

Implementation of tertiary crushing (impact crusher), application of fine aggregate shape test, and mixture evaluation (WT test).

Mix design Concerning the achievement of flow property resistance based on the Marshall stability test, state that the WT test is recommended, etc. Application according to necessity of increased hammering impacts (75 times) in the Marshall stability test, Superpave, and other mix design methods taking heavy traffic load into consideration. Adoption of modified asphalt

Asphalt plant quality control Specification of examples of routine management items. Adoption of extraction test among the essential items of routine management.

Poor quality construction State special illustrative cases (base compaction of 100% or higher) in overseas works, and important points to consider in pavement works in areas with high temperatures.



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Photo2.14 Rutting Unsuitable Material (Aggregate)

(Tanzania)

Photo2.15 Rutting Unsuitable Mix Design

(Ethiopia)

Photo2.16 Rutting Inadequate As Plant

Management (Zambia)

Photo2.17 Slippage on Cemented Base Faulty Workmanship (Tajikistan)

Photo2.18 Slippage on Existing As Layer Faulty Workmanship

(Tanzania) Source: JICA Study Team


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3. Summarization of Findings from Hearings and Questionnaires in Japan

3.1 Hearing Targets and Items

(1) Objective of hearings

In the first stage of the study, materials were collected, the analysis in Japan was conducted, and hearings were implemented with JICA road project officials, pavement-related facilities, etc. in Japan. The hearings were intended to ascertain quality control methods for flow rutting countermeasures and opinions concerning actual cases in the field in Japan and overseas, with a view to using the findings as reference for making improvements to the existing Handbook.

(2) Hearing targets and items

The hearings targeted contractors, pavement companies and consultants who have experience of pavement works in JICA-funded projects (loan aid and grant aid), and experts associated with asphalt plants and this study.

Table 3.1 Targets and Contents of Hearings Target of Hearing

Hearing Contents Company Name

Contractors

- Method for confirming pavement works specifications at times of tender

- Pavement works implementation method (selection of sub-contractors)

- Handling of plant specifications - Illustrative cases and causes of rutting - Other issues in pavement works

DAI NIPPON CONSTRUCTION Satoh Kogyo Zenitaka

Pavement companies

- Plant quality control methods in Japan and overseas

- Pavement materials and plant management in overseas works

- Quality control standards - Implementation of extraction tests - Other issues in pavement works

Kajima Road Obayashi Road World Kaihatsu Kogyo

Asphalt plants (Japan)

- Quality control standards in Japan - Routine management methods - Gradation management standards

Kajima Road Kuribashi Plant Nippon Road Fukushima Prefecture Chuo Ascon (mail) Obayashi Road Kuki asphalt plant

Consultants

- Issues in ODA pavement works - About revision of the Pavement

Construction Supervision/Management Handbook

- Handling in plant specifications - Recent illustrative cases and causes of

rutting - Other

Ingerosec Corporation Eight-Japan Engineering Consultants Inc. Katahira Engineering International Yachiyo Engineering

Other related organizations

- General points concerning rutting countermeasures

- Information concerning HWTD - Mix design

Prof. Takeuchi, Tokyo University of Agriculture Nippon Road Co., Ltd. Nichireki research laboratory



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(3) Hearing results

The main opinions that were confirmed in the hearings are summarized below. Since the opinions have not yet been collated, contradictory views are also stated. The minutes of the hearings are given in the report attachments. Table 3.2 shows general questions related to pavement projects and contents related to rutting in Japan and overseas, while Table 3.3 summarizes the views of contractors concerning differences in opinions between contractors and consultants.

Table 3.2 Main Opinions Ascertained in Hearings

Question Contents Response (Summary))

Overseas pavement projects

Methods for confirming pavement works specifications at times of tender

We let the engineers of related companies handle the parts of the tender documents related to pavement. (Contractor)

Since tender participants are general contractors that don’t have pavement experts, they are incapable of discovering problems in specifications in the tender preparation stage. (Pavement company)

We asked questions about materials information concerning aggregate, etc. in the tender stage, but received no clear response. It is necessary to disclose materials test information in the survey stage. (Contractor)

Pavement works implementation method (selection of sub-contractors)

When selecting a pavement subcontractor, we start from investigating whether there is a local company that can respond to our needs. If there is no local company, we consider a contract with a Japanese company or a company from a nearby country. (Contractor)

Due to the difficulty of newly developing a quarry, we sometimes sign a subcontracting contract with a pavement company that owns a quarry. (Contractor)

Due to the small scale of pavement works, it was not worth carrying over a plant from Japan. (Contractor)

Elaboration and issues in plant specifications

We have never undergone elaboration of specifications regarding asphalt plant. When we limit the plant in terms of specifications, we have less options for finding a pavement subcontractor. (Contractor)

When the scale of pavement works is small, it is not worth carrying over a plant from Japan.

Concerning the asphalt plant, we adopted the batch type and included installation of a screen measuring 2.36mm (2.5mm) in the specifications. (Consultant)

The consultant is responsible for supervising the outputs, but this doesn’t include the plant and equipment. Moreover, it would be better to have no rules that give an advantage to certain bidders. (Consultant)

Plant quality control methods and issues in Japan and overseas

Overseas, often the quality of aggregate is unstable. We visit the aggregate plant to check on quality before it starts shipping. Unless we manage from the grassroots level, we cannot secure quality. (Pavement company)

In countries that have no mountains and need to procure coarse aggregate from neighbouring countries, we have had a lot of trouble with unstable quality because we could not directly visit the quarry site and quarry plant. (Pavement company)

It is our company policy to autonomously manufacture aggregate and mixture. This is because quality control problems arise when aggregate and mixture are purchased in developing countries. (Pavement company)

Experienced employees in a pavement company should be responsible for plant operation and management. We sometimes entrust this work to third country employees or local engineers for budget reasons, however, there have been occasions where this led to a decline in quality. (Pavement company)

Need for extraction tests

As the opinion of a quality control staff member, I would prefer plant extraction tests to be avoided. Even if it is just one sample a day, extraction tests take time and effort and make the work a lot busier. (Pavement company)

In terms of routine management, we monitor the hot bin gradation and


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Question Contents Response (Summary)) asphalt content at the outlet. However, since this is a new plant that we have no experience of using, we intend to implement an extraction test every day. The specifications also include provisions concerning the extraction test. When using new machinery, since you can never be sure if it is going to work or not, we think that extraction tests should be an essential item of routine management. (Pavement company)

Based on experience in a certain Asian country, measuring devices do not have reliable accuracy, while hot bin gradation is also subject to daily fluctuations (the aggregate carried in each day is different). Therefore, extraction tests are essential. (Pavement company)

Even if mixture is purchased, we think it is essential to implement extraction tests. Various approaches are possible, however, a half-day test does not hinder the works at all. (Consultant)

A certain works site I know uses a kerosene centrifugal separator. The test only takes 1 hour if the goal is to ascertain the asphalt content, and it is still only around 3 hours if the test is extended to include gradation. In Japan, safer solvents (Dipsol) are used more often, so it takes between 2.5 hours and 1 day just to confirm the asphalt content.

About characteristic quality control standards

In Japan, the aggregate crushing test (for example, ACV) is not implemented, however, we think it is better to implement it. (Pavement company)

In former French colonies, French standards prescribe about ascertaining air content based on sampling, however, the standard is set very stringently at 6%±2%. (Pavement company)

Illustrative cases and causes of rutting Illustrative cases of countermeasures

In a bridge project in Africa, rutting occurred on the bridge surface, and this was repaired using concrete pavement. It wasn’t possible to use modifying material because there wasn’t enough budget to obtain modifying material or prepare a plant for manufacturing modified asphalt . (Contractor)

In a bridge project in Africa, rutting occurred on the bridge surface. The bridge section is situated on a longitudinal gradient (roughly 7%) and is used by vehicles carrying freight inland from the port (upward slope). Since there is a checkpoint after the bridge, vehicles sometimes stop on the bridge. Moreover, many vehicles are overloaded and they also come to a stop on the bridge (where the longitudinal section is harsh). Accordingly, the bridge pavement is subjected to large braking loads caused by the stopping and starting of large-size vehicles. The fundamental issue is the overloading. (Consultant)

In a bridge project (loan aid) in Africa, rutting has occurred on the bridge surface. The pavement works are outsourced to a local contractor, which undertook all work from manufacture of aggregate to manufacture of asphalt mixture and execution of the pavement works. There is no extraction test, and quality control is implemented based on printed data. After the rutting occurred, core sampling and testing were implemented to confirm the asphalt content and gradation. The asphalt content was found to be as specified, while gradation indicated a high proportion of fine particles, however, this was within the prescribed range of deviation. No special specifications are required in pavement on the bridge surface. As a countermeasure, the asphalt will be switched to modified asphalt. The modified asphalt will be the plant mix type and it is intended to procure the modifying material from Japan. (Contractor)

Opinions concerning revision of the Pavement Construction Supervision/Management Handbook

When using management standards that are adopted in Japan, it is necessary to secure the consent of the counterpart country regarding the validity of standards. We cannot say they are JICA standards and then offer warranty after problems have occurred. (Consultant)

Since there are some countries that do not trust Japanese pavement technology, care is needed. (Consultant)

It is desirable to have the Handbook translated into English so that it can be used as a tool to help communication with the local engineers. (Contractor)

Pavement projects in Japan


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Question Contents Response (Summary))

Routine plant management methods in Japan

Usually in Japan, extraction tests are not implemented on mixture intended for shipping (unless the specifications specially require it). The accuracy of measuring devices is usually guaranteed in the plant calibration; moreover, if the hot bin gradation is confirmed, it should be possible to suffice with routine management based on monitoring rational printed records. (Pavement company)

Routine management basically entails management of printed data from a computer. In addition, we conduct visual management of the hot bin once a day. (Pavement company)

We conduct a sieve test of hot bin gradation two times a month or more. This varies depending on the plant performance. We increase the test frequency in cases of new plants. (Pavement company)

As aggregate inspections, we certify quality when we receive aggregate from the stone crushing operator, and we also conduct autonomous checks roughly once a month. (Pavement company)

In Japan, it is compulsory for measurement certification tests to be conducted on plant measuring devices once a year. (Pavement company)

Applied standards for gradation management

Gradation management standards are derived from plant mixing results. Concerning the preliminary review system too, the results of plant mixing are used as standard values. (Pavement company)

NEXCO common specifications for civil engineering works also state that “site mixing” should be adopted as the standard for deciding the scope of gradation.

In mixing that is based on indoor testing, aggregate obtained from the quarry is used, however, sometimes asphalt plants and quarry plants use different sieve sizes. Also, there are differences in aggregate classification based on the number of bins in the asphalt plant. Therefore, when conducting mixing based on gradation management standards, we adopt the results of plant mixing. (Pavement company)

Specifically: ・ The size of the screen used at the quarry to manufacture simple grain

crushed stone is not always consistent with the screen size in the plant. Accordingly, grade 6 crushed stone (grade 5 and grade 7) used in indoor mixing is not necessarily the same as the gradation in the plant hot bin 3 (bin 4 and bin 2).

・ The dust content of aggregate is recovered in the plant manufacturing process. (Drier→Dust collectorー→Bag accumulation or discharge to the aquifer). Therefore, differences in gradation arise due to the fine particle content. (Pavement company)

General points concerning rutting countermeasures

Knowledge and opinions concerning rutting countermeasures

Due to concern over flow rutting in the surface layer, we have adopted 12cm (surface layer + base layer) to reduce the plastic region (referring to connected EU roads). Also, since the necessary DS value was found to be almost 4,000, we use modified asphalt on the surface layer. (Consultant)

Rutting occurs when asphalt with high temperature sensitivity is used on the surface layer. To address the issue of rutting, it is better to adopt a thin layer of asphalt on the surface. In that case, it is ideal to use hard asphalt that has low temperature sensitivity for the base. (Prof. Takeuchi)

The gradation of granular base is close to the Fuller-Thomson curve (gradation curve for filling particles to the highest density) and cannot be compacted any further. Therefore, it becomes a matter of what material to use for the base. However, ample consideration must also be given to economy. (Prof. Takeuchi)

Use in surface layers that comprise asphalt of large gradation can also be considered. (Prof. Takeuchi)

Other

In light of past experience and conditions in other countries, it appears that a fairly high degree of flow property resistance is secured with straight asphalt. Japanese engineers tend to rely too much on modifying materials, and there are often times when opinions diverge from the outset when discussing measures in light of conditions in the


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Question Contents Response (Summary)) overseas country concerned (difficulty of procuring modifying materials, etc.). (Consultant)

The Japanese are frequently unskilled at implementing pavement construction. It’s because they adhere too much to Japanese methods without considering the local conditions. (For example, the asphalt content in Japan is extremely high compared to in Pakistan and Africa). (Consultant)

Since we cannot be sure when letting Japanese contractors construct a single layer, we tend to reduce the likelihood of error by asking them to build a two-layer structure. (Consultant)

No matter how often we explain that “mix design＝design, therefore, it is the consultant’s responsibility”, we fail to obtain understanding. (Consultant)

Information related to HWT

This item is discussed in Chapter 5-2 of the report.


Table 3.3 Illustrative Cases of Issues in the Field Voiced by Pavement Companies Question Contents

Response (Summary))

Problems of standards indicated in technical specifications and issues in application

Weather conditions and traffic conditions are not reflected in specifications. Even though we conducted mix design in consideration of flow property resistance over a scope that didn’t deviate from the range of specifications, it still wasn’t enough (rutting still occurred). The porosity was okay at 3-5%, but the voids filled with asphalt (VFA) was 75%-85%. Because VFA was large and covered a narrow scope, the asphalt content was large while the porosity was small. It was a mistake to set the asphalt content within the common scope. We should have stressed the irrationality of the specifications.

Although the specifications did include the proviso “For reference”, the asphalt content was stipulated. Moreover, it was clearly excessive. This scope was stubbornly adhered to, while tolerance of ±0.4% was applied where necessary. For example, in cases where the special note specifications in Japan simply do not fit with local conditions, it is normal to respond through revised special notes or written instructions upon holding discussions, however, this doesn’t seem to be the case overseas. We did see specifications concerning the applied amount of prime coat and tack coat, however, these too were clearly too high.

Even though specifications are often deviant or they are irrational in technical and quality terms, they are left untouched. The reasons include the following: ・People don’t notice (they lack knowledge of pavement technology) ・People don’t like to admit that specifications are wrong. ・People don’t want to be made responsible (they don’t want to have to take steps because they brought the problem to light). I felt that the level of the consultants was extremely low. Even though materials are decided with the consultant’s approval, the contractor incurs the responsibility. The consultant has decision making authority but doesn’t have to take responsibility. Consultants are very negative when it comes to changing specifications. It’s a matter of responsibility. I think that this is the problem.

Even though I was dispatched from Japan as a pavement expert engineer, I felt a dilemma because the specifications prevented us from building good pavement.

Illustrative cases of discrepancies in opinions between consultants and contractors that were a problem in the field (filler)

There are major differences between Japan and overseas in terms of how filler is used. In Japan, since sand that doesn’t contain filler is used, the filler is almost 100% supplied from outside (filler silo) (in Japan’s case, since stone powder is stipulated in JIS, gradation no higher than 0.075mm is targeted). Overseas , however, filler is included in sand (crushed limestone is used as it is instead of stone powder). Since cold bins are used for performing mix design in both batch and continuous processes, testing is conducted using PI no greater than 0.425mm in the sand. Basically, 4 or less is stipulated for 0.425mm pass in aggregate-related reports related to American Superpave and other overseas projects. However, there have been times where we were asked to test even JMF materials on the works site. In other words, we were required to conduct testing on materials that were recovered in a bag filter.


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Question Contents

Response (Summary))

Quality confirmation of asphalt concrete is implemented using cold bin materials in indoor mixing tests. Materials that pass such tests should also be acceptable as JMF asphalt concrete. Therefore, there is no need to redo the mix design of hot bin materials that are used in JMF. Moreover, since testing cannot be performed in the case of a continuous plant, the requirements do not make sense.

Illustrative cases of discrepancies in opinions between consultants and contractors that were a problem in the field (clay)

The PI percentage does not inherently indicate the amount of content but rather shows the difference in terms of water content between the liquid limit and the plastic limit. To grasp the viscous content, the sand equivalent test and other tests should be implemented. Moreover, the decision about whether or not asphalt concrete is harmful should be made after manufacturing the asphalt concrete.

Specifications do not reflect site conditions, rather they are simply cut and pasted from other countries or works sites. The intended purpose of the specifications is not understood.


3.2 Summarization of Findings in the Questionnaire to Consultants in Japan through IDI

(1) Objectives of the questionnaire

Opinions and requests were gathered from consultants that use the “Pavement Construction Supervision/Management Handbook (Draft)” (hereafter, the “Existing Handbook”) for reflecting in the revision of the “Existing Handbook”.

(2) Targets of the questionnaire

Out of consultants (23 companies) that are regular members of the Infrastructure Development Institute, the following nine companies which have experience of JICA grant aid road projects were targeted.

Ingerosec Corporation, Eight-Japan Engineering Consultants Inc., Oriental Consultants Global Co., Ltd., Katahira & Engineers International, CTI Engineering Co., Ltd., Central Consultant Inc., Chodai Co., Ltd., Nippon Koei Co., Ltd., Yachiyo Engineering Co., Ltd.

(3) Questionnaire items

The contents of the questionnaire items are as indicated in Table 3.4.

Table 3.4 Questionnaire Items Questionnaire No. Contents of Questionnaire Q1 Concerning existence of the “Pavement Construction Supervision/Management

Handbook” Q2 Experience of using the “Pavement Construction Supervision/Management

Handbook” in design and construction supervision/management Q3(1) Points where troubles or difficulties have arisen in applying the “Existing

Handbook” (in particular items related to rutting countermeasures) Q3 (2) Points that should be improved or reinforced (in particular items related to rutting

countermeasures) Q3 (3) Other points noticed or requests (in particular items related to rutting

countermeasures) Q4 Other requests concerning the “Existing Handbook” in general


(4) Questionnaire results

1) Number of responses


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Out of 9 companies, 6 gave responses.

2) Questionnaire results

Table 3.5 Concerning Existence and Experience of Using the “Existing Handbook” Q1. Concerning existence of the “Existing Handbook” Yes No

Number of responses: 6 6 0 Q2. Experience of using the “Existing Handbook” Have experience No experience

Number of responses: 6 4 2 Source: JICA Study Team

Table 3.6 Points where Troubles or Difficulties have arisen in Applying the “Existing Handbook” Relevant Part in the

Handbook (item/page)

Points where troubles or difficulties have arisen

3. Pavement works construction management (3) Mix design/test 2) Asphalt mixture performance test/P30

It is recommended that the WT test be implemented, however, there are no standards for indicating the situations in which the WT test should be used.

Response In the revised Handbook, it was specified standards for adopting modified asphalt and also clarify concerning implementation of the WT test.

3. Pavement works construction management (3) Mix design/test 2) Asphalt mixture performance test/P30 (Related passage on P56)

Since it is generally difficult to secure WT test instruments for confirming DS value in countries that are targeted by grant aid projects, it is necessary to examine the procedure for implementing tests in Japan and third countries. At this time, it is desirable to consider the impact on management cost of a

test implementation plan that encompasses from the procurement of local aggregate and other materials, transportation, storage, and preparation of samples (implementation of Marshall stability test), and sort model cases of test methods (including adoption of WT test machines used in Europe and America) that are objectively deemed to be valid according to each area.

Response Use of WT test (Japan) for Grant aid project was stated in revised Handbook. 5. Flow rutting countermeasures (2) Important points to consider in mix design 5) Materials problems/P56

There are no specific DS road surface design standards.

Response Specific DS calculation methods and standards (draft) that can be used overseas are described.

5. Flow rutting countermeasures (2) Important points to consider in mix design 5) Materials problems/P56

Caution points after considering the materials that are available on actual sites are needed.

Response Domestic testing was based on overseas cases to the extent possible. The results and points to note about materials obtained overseas are also described.

General matters

The Handbook is used as a reference resources for conducting pavement construction supervision in developing countries. Pavement technology has become highly specialized in recent years, with specialist knowledge required concerning materials, mixing, plant operation, and construction, however, in construction supervision implemented by a consultant, even when a pavement expert is assigned, usually only one expert is assigned for a short period. It is thus difficult for consultants to oversee (obtain support for) general matters concerning pavement technology on sites


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Relevant Part in the Handbook (item/page)

Points where troubles or difficulties have arisen

in developing countries far away from head offices in Japan. The quality of construction, including occurrence or not of rutting, largely depends on the skill and know-how of the contractor. In particular, since smooth implementation from plant installation to trial operation, trial mixing and test construction has a major impact on the works schedule, it is important for the contractor to have experience of pavement construction in the country concerned. Therefore, especially in cases where preliminary survey points to the possibility of problem soil, etc., it is deemed advisable for the consultant to assign sufficient pavement experts and to give priority to experience in the country concerned when selecting the contractor.

Response Upon examining the proposed contents, discussions will be held with JICA concerning how they should be reflected in the future.

General matters

Understanding would be facilitated if weather conditions in ODA target countries were zoned and illustrated (indicated on +Map) as shown below. Zone / Region / Air temperature / Gradation example / Asphalt content / Remarks A: Africa / A / 20～35℃/ A / A / Night-time temperature 25℃, 3 months B: Africa / B / 25～38℃/ B/ B/ Night-time temperature 27℃, 6 months C: Asia / A / 25～38℃/C/ C/ Night-time temperature 25℃, 3 months D: Asia / B / -5～40℃/ D/ D/ Night-time temperature 22℃, 2 months Gradation pattern: A / B / Japan (reference) Asphalt content: A 3.7～5.2% / B 3.5～5% / Japan (reference) 5.2～5.7% (dense graded) Remarks: Modifying material example Points to consider: 1) Unless the aggregate specific gravity test is carefully implemented, this

will lead to failure of the mix. 2) There have been cases where water on the cement stabilized base cause

deterioration, cracking and slip trouble on the surface layer 3) There have been cases where troubles arose because a bag filter wasn’t

installed in the plant 4) Countries that present a high risk in terms of aggregate quality 5) Countries that have experienced rutting in the past: Tanzania, Ethiopia,

Zambia

Response

It is difficult to create a MAP for the proposed content related to weather because the data volume is huge. However, the results of verification in representative cities are shown. Data such as the gradation ranges of major countries are described in the Appendix. In addition, other cases are described as much as possible.

-

Some proponents specify use of Superpave because it has a more progressive image (e.g. Tanzania), however, Japanese companies need to prepare a pattern for presenting past performance (how many kilometres constructed) and explaining that it is better to adopt wheel tracking because it enables site reproducibility (not only in a laboratory) and thereby facilitate the adoption of Japanese standards. It is considered necessary to compile information concerning application of Japanese standards in areas of Japan that are similar to the zones described earlier.

Response The achievements and examples of the WT test in Japan and the fact that the standards are stricter than other standards are described in the Appendix.


Table 3.7 Points that are considered to Require Improvement and/or Reinforcement in the “Existing Handbook”


Points that are considered to Require Improvement and/or Reinforcement

3. Pavement works construction management

When locally manufacturing polymer modified asphalt mixture, it is necessary to have accurate measuring equipment for adding plant mix type


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(2) Materials procurement test 2) Bitumen (asphalt ) modified asphalt /P20-23

modifying material. In particular, in continuous plants, since it is generally difficult to continuously conduct the measurement management of additive, in cases where compatible plant equipment cannot be secured, it is necessary to manufacture plant mix type modified asphalt with modifying material added in advance and carry it onto site. In such cases, to avoid separation when conducting mixed manufacture onsite, temperature management during heating is important. In either case, since the series of quality control measures in materials procurement, manufacture, transportation, storage and construction when using modified asphalt have a major impact on calculation of the construction cost, it is necessary to conduct detailed examination as construction supervision items corresponding to the local conditions.

Response Upon examining the contents pointed out, the handbook on the production method of modified asphalt, the response in a continuous plant, and quality control, including the examples so far, was described.

3. Pavement works construction management (4)Base/subbase construction management Flow rutting countermeasures in each country/P35

It would be helpful if the Handbook indicated test methods, important points to consider in construction supervision, countermeasures and other advice in cases of harsh weather conditions in target areas, for example, road surface temperature exceeds 60 degrees.

Response The correspondence to the pavement temperature is described in the road surface design of revised Handbook. In addition, points to keep in mind in construction supervision are described in the handbook including past cases.

5. Flow rutting countermeasures (2)Important points to consider in mix design /P52-55

Grant aid target roads are regarded as important routes in the target countries in light of their project objectives; moreover, the target developing countries do not have adequate maintenance structures due to budget constraints, and since the securing of long-term integrity after roads goes into use directly impacts the project evaluation (effectiveness), it is essential to set the target DS value based on the assumption of a long-term design period. Considering these points, trustworthy standards that are adopted on important routes in Japanese specifications should be used, and adoption of polymer modified asphalt should be recommended as the basic policy for the purpose of strengthening flow property resistance for longer service life.

Response It was revised the Handbook so that the validity of adopting modified asphalt can be objectively explained.

5. Flow rutting countermeasures (2) Important points to consider in mix design /P54

Concerning application of modified asphalt Points concerning application of modified asphalt in Japan are indicated, and modified asphalt in overseas cases is frequently applied in reference to these. If possible, we want the Handbook to stipulate about application of modified asphalt with conditions attached. (Some overseas manuals stipulate about application of modified asphalt.)

Response In the revised Handbook, it was clarified about adoption of modified asphalt overseas in the road surface design stage.

5. Flow rutting countermeasures (2) Important points to consider in mix design /P54

Concerning the categories of large vehicle traffic volume comparing DS standards, etc. in Table 5.6, since the comparative relationship between the three standards is not clear, it is difficult to apply the standards. It would help if there were a practical commentary.

Response In the revised Handbook, it was specified concrete DS calculation methods and standards (draft) that can be used overseas.

Reference materials 6 Large vehicle traffic volume and rutting on high-speed roads/P57

The graph is effective for seeking future estimates of the amount of rutting according to each DS, however, the data is limited to conditions in Japan. If data from other countries and from experience of implementation in ODA is available, it would provide useful reference.


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Response It is difficult to obtain rutting data of ODA. The necessity of accumulation of future data was described.


Table 3.8 Other Points Noticed or Requests in the “Existing Handbook” No. Other Points Noticed or Requests

1

On overseas works sites, specifications concerning pavement materials, construction, etc. are stipulated in technical specifications; thus it is necessary to specify contents about materials and construction in the technical specifications. Since technical specification are created when creating the tender documents (at the time of detailed design), it is necessary to thoroughly inform those specifications to staff implementing the detailed design.

Response Use of the Handbook will be expanded through the consultant briefings and IDI. Source: JICA Study Team

Table 3.9 Other Requests concerning the “Existing Handbook” in General No. Other Requests concerning the “Existing Handbook” in General

1

Since the addition of countermeasures and materials in the “cooperation preparatory stage” incurs additional costs, unless it is written that “such countermeasures will be examined and taken into account in cost estimation” in the sections describing each countermeasure, the contents are merely guidelines (i.e. not standards) and so cannot be applied. (In such cases, since money cannot be set aside, design is implemented by the conventional method and quality is sought from the contractor at the time of construction. Even in cases where details regarding the large vehicle traffic volume and overloading ratio are unknown, adopt a higher mix, etc.).

Response The revised handbook specifically described how to reflect modifiers in the cost estimation.

2 It is desirable that the Handbook be translated into English so that it can be used as a tool for communicating with local engineers.

Response The revised Handbook was translated into English.

3 Rutting of pavement on bridges is also a major issue, so addition of countermeasures for that are also desired.

Response Since bridge surface rutting is not included among the study targets here, it will continue to be treated as a matter for consideration.

4 Since the Handbook tends to be sweeping in parts, it is desirable that it be given a simpler composition for more practical and simpler use.

Response The handbook flow is simplified with three parts (design / survey, construction, appendix).

5

As a result of conducting internal hearings, our company had few road construction supervision projects and little experience of use after the existing Handbook was published. In future, we hope to share information after requests, etc. have been gathered from related officials.

Response Use of the Handbook will be expanded through the consultant briefings and IDI. Source: JICA Study Team


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4. Exchange of Opinions between Experts for the Pavement

4.1 Outline of the Roundtable Meetings of Experts

Hearings with companies that have experience of road construction and improvement, construction management/supervision in ODA projects reveal a lot of objective responses, however, it is sometimes difficult to systematically, comprehensively and objectively grasp problems concerning road pavement flow property resistance, mixing and construction through hearings alone. Accordingly, the joint venture utilized its experience and network of IDI related to pavement research to assemble around 10 pavement experts of differing affiliations and standing and held opinion exchange meetings. Table 4.1 shows the opinion exchange meeting members.

Table 4.1 Opinion Exchange Meeting Members

Field Name Affiliation Attendance at First Meeting Remarks 1st 2nd

Chairperson Teruhiko Maruyama

Professor Emeritus, Nagaoka University of Technology 〇〇

Observer Koichi Oguro Advisor, Toa Survey Inc. 〇〇 HB 1st edition

member

Education/ Research

Shuichi Kameyama

Professor of Urban Environmental Science, faculty of Engineering, Hokkaido University of Science

〇 X

Shoichi Akiba Professor, Department of Civil Engineering, College of Industrial Technology, Nihon University

〇 X

Yasushi Takeuchi

Professor, Department of Bioproduction and Environment Engineering, Faculty of Regional Environment Science, Tokyo University of Agriculture

X 〇

Osamu Takahashi

Professor, Civil and Environmental Engineering, Nagaoka University of Technology

X 〇

Research / Administration

Masayuki Yabu

Senior Researcher, Pavement Team, Road Technology Research Group, Public Works Research Institute

〇

Keizo Kamiya

Manager, Pavement Research Section, Road Research Department, Nippon Expressway (NEXCO) Research Institute Company

〇〇

Road construction/

materials

Toshiaki Matsuda

Manager, Public Information and Engineering Department, Japan Road Contractors Association

〇〇 Note 1

Satoshi Furukawa

Obayashi Road Headquarters Engineering Department 〇〇 HB 1st edition

member

Consultant

Seitaro Tsukuda

Manager, Research Department 3, Infrastructure Development Institute 〇 X Note 2

Hideaki Morita Director, Ingerosec Corporation X 〇

Client

Moriyasu Furuki

International cooperation expert (road field) 〇〇

Akira Fujiwara

Implementation Supervision Section 1, Financial Cooperation Implementation Department

〇〇

[Note 1] Road Construction Association internal workshop composition [Note 2] Infrastructure Development Institute internal workshop composition Source: JICA Study Team


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4.2 First Opinion Exchange Meeting (May 22, 2019)

(1) Outline of the first opinion exchange meeting

Place: Conference Room 108, Nibancho Center Building, 5-25 Niban-cho, Chiyoda-ku, Tokyo 102-8012, Japan

Time: 14:00~16:00 Agenda: 14:00～14:05 (5 minutes): Opening address (Maruyama Professor Emeritus, Nagaoka

University of Technology) 14:05～14:10 (5 minutes) Explanation of purport (Mr. Fujiwara, JICA employee) 14:10～14:20 (10 minutes) Necessity of the Handbook (Mr. Furuki, JICA international

cooperation expert) 14:20～14:50 (30 minutes) Explanation of this fiscal year’s study plan (Consultant: Mr. Mizuno,

Team Leader) 14:50～15:50 (60 minutes) Questions and discussion (all members) 15:50～16:00 (10 minutes) Closing remarks (Mr. Furuki, JICA international cooperation

expert)

Contents of Explanatory Materials for the First Opinion Exchange Meeting of Experts

1. Characteristics of JICA projects

2. Outline of the Handbook 2.1 Objectives of the Handbook 2.2 Applicable scope of the existing Handbook and information that needs to be added 2.3 Applicable scope and reinforced points of the revised Handbook 2.4 Composition of the revised Handbook (Draft)

3. Flow rutting countermeasures 3.1 Illustrative cases of flow rutting 3.2 Sorting of the causes of rutting occurrence 3.3 Outline procedure of flow-resistant pavement design and construction (draft) 3.4 Cooperation preparatory survey (rough design)/Detailed design (DD) stage 3.5 Construction stage/mix design 3.6 Construction stage/ construction supervision/management

4. Other matters 4.1 Analysis work in Japan 4.2 Implementation of overseas preliminary questionnaire and site surveys 4.3 Study schedule 4.4 Meeting members (draft)

(2) Main opinion in the first opinion exchange meeting

The main opinions that were aired in the First Meeting are shown in Table 4.2.

Table 4.2 Main Opinions in the First Meeting

Item Main opinions aired in the opinion

exchange meeting Response in this study

Manifestation of flow rutting

Is the occurrence of flow rutting becoming manifest in overseas countries?

State the results of local hearings and field observations in this report.

→Flow rutting is occurring on steep uphill slopes, etc. in recent years due to the rapid


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increase in volume of heavy-load vehicle traffic. Are the causes of damage arising in the materials; are there issues concerning traffic volume?

In the Handbook, specify about traffic volume and axle load surveys and calculation of design load that takes risk into account. →Setting of traffic conditions is also an

issue, however, the materials mixture is considered to be a bigger issue.

Flow rutting countermeasures

The easiest thing is to reduce the asphalt content, but it is important to determine how far to reduce it.

State that reducing the asphalt content is also effective as a flow rutting countermeasure in the mix design stage. Also, add results concerning DS and asphalt content from tests in Japan as attached materials.

→ It is thought that construction supervision consultants, contractors, and clients don’t know either.

Utilization of DS estimation formula

Will countermeasures that consider very heavy loads be required?

As a flow rutting countermeasure, specify calculation of the DS value based on the estimation formula in the Handbook. State the results of applying the estimation formula overseas in the Handbook materials.

→Temperature and other conditions differ between countries and regions. Utilization of the Japanese DS estimation formula is considered necessary. →The necessary data for the DS estimation formula is surveyed in the design stage.

Pavement temperature issue

Does the WT test temperature of 60 degrees reflect actual conditions?

Concerning results when the test temperature is 70 degrees, state pre-existing tests and literature in the attached materials.

→There are illustrative cases where the pavement temperature exceeds 70 degrees, however, there are major impediments to setting the DS value for the case of 70 degrees. Here, experience will first be gathered assuming the case of 60 degrees.

Concerning WT test and HWT test (relevance and correlation of HWT test and WT test)

Correlation of HWT test and WT test In JICA grant aid projects, state that mixtures are evaluated using the Japanese WT test. Concerning HWT test, through overseas trends obtained in the hearing results in Tanzania (standards now being formulated), etc. and collection of existing literature in Japan, state contents concerning the correlation between WT test equipment and HWT test equipment in the attached materials.

Confirm the local availability of HWT test equipment, its conditions of use, and if possible, utilize them in flow property resistance survey work in the targeted sites.

Continuous plant Overseas asphalt plants are generally the continuous type.

State contents concerning plant management methods including continuous plants.

Modified asphalt mixture

Concerning the method for manufacturing modified asphalt mixture

State contents concerning modified asphalt mixture manufacturing method in both continuous and batch plants.

Concerning securing of aggregate on sites

In the overseas, the quality of crushed stone is determined by the quality of the quarry operator. In Bangladesh, which has no local quarries, all crushed stone is imported by local suppliers, but quality levels vary from day to day and it seems that the suppliers do not conduct quality

State contents concerning the aggregate and materials tests that should be implemented by the consultant in the survey stage. In construction, state in the Handbook that management in quarries is part of the aggregate quality control


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control. responsibility of contractors.

Plant management

Japanese plant inspections are implemented upon confirming the asphalt content, measured values and so on. On works sites in developing countries, materials are free flowing and sand causes blockages, and there is concern over printouts of measured values.

State illustrative cases of plant damage and current conditions of mixture problems in the Handbook, and also specify that the extraction test is an essential item of routine management.

Concerning extraction test

There are many places where extraction is conducted using gasoline onsite.

State illustrative cases of plant damage and current conditions of mixture problems in the Handbook, and specify that the extraction test is an essential item of routine management.

Screens are poor quality and have a lot of damage, and plant management is not adequately conducted.

Works special note specifications

On sites, it is difficult to make changes from specifications.

State in the Handbook that making appropriate changes to specifications is also included in the consultant’s construction supervision.

Mix design for tests implemented in work

It is necessary to confirm by means of mix design using overseas materials.

Implement the tests that are adopted in Japan with contents that are adapted to match with actual conditions overseas.

Flow property resistance confirmation test

It is advisable to implement additional tests to confirm the impact of filler on flow property resistance.

Add a test concerning the influence of filler to the tests implemented in Japan.

Concerning faults following works completion (utilization of HB)

Defect liability warranty is provided for work conducted overseas, however, there are no provisions concerning performance. Sometimes problems are confirmed following the end of the defect warranty period and standards are compiled from that point.

It is intended to translate the proposed Handbook into English and provide it to countries where JICA conducts projects.

→Unless there are penalties, there is a risk that problem stone (aggregate) will continue to be used from now on, and hence it is necessary to inform local counterparts so that they can conduct ongoing management.


Photo 4.1 The First Opinion Exchange Meeting Source: JICA Study Team


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4.3 Second Opinion Exchange Meeting (January 20, 2020)

(1) Outline of the second opinion exchange meeting

Place: Plaza Edogawa-bashi 3F, 1-23-6 Sekiguchi, Bunkyo-ku, Tokyo, 112-0014, Japan Time: 15:00～17:00 Agenda: 15:00～15:05 (5 minutes) Opening address (Maruyama Professor Emeritus, Nagaoka

University of Technology) 15:05～15:10 (5 minutes) Explanation of purport (Mr. Fujiwara, JICA employee) 15:10～15:50 (40 minutes) Explanation of the Handbook (Consultant: Mr. Mizuno, Team

Leader) 15:50～16:50 (60 minutes) Questions and discussion (all members) 16:50～17:00 (10 minutes) Closing remarks (Mr. Furuki, JICA international cooperation

expert)

Contents of the Explanatory Materials for the Second Opinion Exchange Meeting of Experts

1. Outline of the second opinion exchange meeting 1.1 Characteristics of JICA projects 1.2 Objectives of the Handbook 1.3 Options aired in the First Opinion Exchange Meeting

2. Outline of the Handbook 2.1 Handbook composition 2.2 Part 1: Important points to consider in survey/design 2.3 Part 2: Important points to consider in construction supervision/management 2.4 Priority (discussion) items

3. Flow rutting countermeasures 3.1 Road surface design 3.2 Evaluation of flow property resistance of mixture 3.3 Mix design 3.4 Plant management

4．Test results in Japan 4.1 Outline of tests 4.2 Outline of preliminary test 4.3 Preliminary test results 4.4 Outline of verification experiment 4.5 Verification experiment results

5. Other matters 5.1 Design checking using multilayer elastic theory 5.2 Superpave

6. Meeting members (2) Main opinions in the second opinion exchange meeting

The main opinions that were aired in the Second Meeting are shown in Table 4.3.


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Table 4.3 Main Opinions in the Second Opinion Exchange Meeting

Item Main opinions aired in the opinion exchange meeting Response in this study

DS calculation equation

Average monthly temperature is adopted, however, are temperature changes over 24 hours considered?

Implement verification at the 24 hour temperature and the monthly average temperature. State verification illustrative cases in the attached materials.

Traffic volume is presented in terms of ESALs and pavement converted number of wheels, which are on different dimensions. When using the DS estimation formula, are both sets of data for ESALs and pavement converted number of wheels available?

From the data obtained in axle load survey, it is possible to obtain data for both types. State the calculation examples in the attached materials.

The formula here is that used by the Public Works Research Institute in Japan. Only Japanese data is used concerning temperature conditions, etc. too. Can this be applied to Africa?

In the future projects, accumulate the calculated DS and actual WT data, and consider implementing review in the future based on the gathered information.

Target DS

Surely DS 1500~6000 presents too high a hurdle. Isn’t DS 1000~1500 a more realistic target for straight asphalt?

It is intended to use the Ministry of Land, Infrastructure and Transport’s DS 1500 as the border for straight asphalt, but the basis of the determined standard will continue to be reinforced.

If it is DS1500, it is difficult to judge about inserting modifying material from the start. For example, incorporating LCC thinking, isn’t it better to say that it is cheaper to insert modifying material?

Reflect illustrative cases of economic analysis using LCC in the Handbook.

Axle load ASSHTO has coefficients for reducing the axle damage factor for 2 axles and 3 axles.

In the Handbook, reduction based on the axle layout will not be adopted. State in the attached materials.

Plant control

Troubles often arise when there is no bag filter. Isn’t it possible to examine in a plant that is stipulated as having a bag filter in the specifications?

In the Handbook, it is not intended to examine the plant based on specifications.

Do plants refer to both the continuous type and batch type?

Both types exist overseas. The Handbook summarizes caution points in consideration of both types.

Multi-layer theory

When the subgrade elastic coefficient is calculated as 10CBR, the elastic coefficient ends up on the low side and the overall flection increases. At 10CBR, it is thought that parts with small CBR are underestimated.

Verification will continue to be implemented in the study. Base/subbase deterioration can be evaluated by subgrade deterioration. This can also be used for investigating causes of

damage in the multilayer elastic theory and theoretical design method.

Drainage issues There are illustrative cases of laterite, however, where will drainage issues be written? The general assumption is that water is not allowed to infiltrate pavement.

In the Handbook, state the importance of drainage and give illustrative cases of base drainage, etc.

Tests in Japan

Concerning the graph showing the relationship between GC residual air gaps and DS, I understand that it differs from the forecast, however, in the WT test too, is it possible that abnormal values better or worse than expected appeared because there weren’t enough test samples?

There still isn’t much data or past track record. Judgment cannot be made based on the test results at the current time. Verification of the test results will continue to be implemented in the study.

Even if the air gap ratio is small, wouldn’t the DS increase if the asphalt content is small? We may know more if there are the final air gap ratio and the air gap ratio at the three times of N-initial, N-design and N-max. If data is going to be gathered, it is better to take not only the final air gap ratio but also data for the first 10 times and also midway at around 120 times.



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Photo 4.2 The Second Opinion Exchange Meeting Source: JICA Study Team


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5. Report on the Analysis within Japan

5.1 DS value Calculation Method

(1) Calculus equation for DS value

The “Road Pavement Design Handbook in Assistance Surveys (draft)” that was prepared in the previous basic research shows the method for acquiring the performance of DS as the target of the necessary asphalt mixture based on the traffic conditions, climatic conditions, and designed rutting depth as the specific method (draft) of the road surface design. However, since adequate solutions are not presented for the issues on the specific DS value calculation methods and the utilization methods for the target countries of different climate conditions, improvements and reinforcement of the contents are made regarding the specific strategy for actually calculating the DS values of the target countries.

Prior to the creation of temperature correction coefficient distribution maps for developing countries, the temperature correction coefficient distribution map that is used in Japan is examined. Specifically, the differences with the values on the temperature correction coefficient distribution map that is proposed are verified by using the climatic data from 1985.

In the Pavement Design Handbook (2006), an expression is proposed for calculating a DS performance value as the target of the required asphalt mixture by setting a design rutting depth for a large vehicle traffic volume over a specific duration. This method is based on the civil engineering reference material, “Proposal of a dynamic stability target setting technique for asphalt mixtures (ITO Gosei, et. al.)” (referred to as the civil engineering paper).

DS 0.679

DS : Dynamic stability (rotations/mm) D : Rutting tolerance (mm) Y : Service period (days) T : Large vehicle traffic volume (vehicles/day) W : Wheel load correction coefficient

= equivalent standard wheel load (ESWL)/heavy vehicle traffic volume/day Source: Proposal for Dynamic Stability Goal Setting Methodology for Asphalt Mixtures

V : Running speed correction coefficient General 0.4 Intersections 0.9 (not apply to outflow of intersections) Ct : Temperature correction coefficient

Of the parameters indicated above, a distribution map is proposed for the temperature correction coefficient based on the following expression.

Log Ct 𝐿𝑜𝑔 𝐷𝑆 𝐿𝑜𝑔 𝐷𝑆 0.0003216𝑇 0.01537𝑇 2.080

Ct = Temperature correction coefficient (DS0/DSt) DS0 : Dynamic stability with 60℃ DSt : Dynamic stability with test temperature T : Paved road surface temperature (℃)

(Equation 5.1)

(Equation 5.2)


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Source: Pavement Design Handbook P.41 (Japan Road Association)

Figure 5.1 Temperature Correction Coefficient Distribution Map

The temperature and temperature correction coefficient (Ct) in the above equation rapidly increase when the road surface temperature exceeds 50-60 ℃ as shown in Figure 5.2. Therefore, as the road surface temperature increases, the required DS value sharply increases.


Figure 5.2 Relation between Temperature and Coefficient (Ct)

Examination on the use of monthly average temperatures for the calculation of the temperature correction coefficient

In general, the average value of the temperature correction coefficients based on the hourly temperatures is used for calculating the temperature correction coefficient. However, in developing countries, hourly temperature data may not be able to be obtained from the locations near the offices. Therefore, for the calculation of temperature coefficients in developing countries, the possibility of using monthly average temperatures as the alternative to hourly temperatures is verified for calculating temperature coefficients since they can be obtained more easily. In the temperature


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correction coefficient distribution map that is shown above, correction coefficients are calculated for all the sites where the temperatures that are observed by AMeDAS for the period from 1984 to 1986. This verification task targets the cities on the correction coefficient setting lines of the distribution map that are shown below by using the AMeDAS data from 1985.

As for the pavement temperature (T) used in equation 5.2, there are two types, Akiyama's equation and the equation shown in the pavement design handbook. Here, the time temperature and the monthly average temperature are compared using both equations.

y = 1.100x + 1.500 + 0.170𝑒𝑒0.126𝑥𝑥 y : Pavement surface temperature (℃) x : Temperature (in air) (℃)

As shown in Table 5.1, the differences of temperature correction coefficients between hourly temperatures and monthly average temperatures confirm that the hourly temperatures are comparatively higher than the monthly average temperatures. The variations of the differences are within the range from -0.002 to 0.006, which are minimal. To verify the factor for causing the variations of the increase rates of temperature correction coefficients between monthly average temperatures and hourly temperatures, data is extracted from two types of cities each, one with large differences and the other with small differences.

Table 5.1 Comparison of Temperature Correction Coefficients by Location


(Equation by Akiyama)


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The graph that is shown below indicates the temperature correction coefficients based on the monthly average temperature, highest temperature of the month, lowest temperature of the month, average of daily highest temperatures, and average of daily lowest temperatures. The result indicates the following:

The Climate Category (cold regions, temperate regions, etc.) does not have much impact on the Ct differences between the hourly temperature and the monthly average temperature. → In Wakinosawa (Aomori) and Ohara (Okinawa), differences of average temperatures are assumed to have no significant impact since the difference of Ct of each is small.

When there is any hourly temperature that excessively deviates from the average temperature, the difference becomes large since the hourly Ct is impacted by the value that deviates excessively.

Since the increase of the Ct of high temperatures is larger than that of low temperatures, the hourly Ct is slightly larger than the monthly Ct.

This means that the calculation expression is sensitive to the excessively high temperature and the difference between the hourly Ct and the monthly Ct is due to the excessively high hourly temperature. However, since in this verification, the maximum difference is very small, which is 0.006, substitution of hourly temperatures with monthly average temperatures may not cause any problem. Since the Ct based on the hourly average temperature tends to be a smaller value than the Ct based on the hourly temperature, the value is closer to the value that is specified in the Pavement Design Handbook.


Figure 5.3 Comparison of Temperature Correction Coefficients

As shown in Table 5.2 below, the difference in the temperature correction coefficients for temperature by hour and average temperature by month indicates that the effected range of the difference is about 0.004 at the most.

𝑀𝑀𝑀𝑀 = 𝑀𝑀𝑀𝑀 �1 + 2.54𝑧𝑧+10.16

� − 25.49(𝑧𝑧+10.16) + 10

3

Mp : Pavement surface temperature (℃) Ma : Average monthly temperature (℃) z : Depth (cm) from surface

(Equation from Pavement Design Handbook)


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Table 5.2 Verification of Temperature Correction Coefficients by Hourly Temperature and Average Temperature by Month (Japan)


Figure 5.4 shows the results of a similar examination for tropical countries. For the purpose of verifying the difference between the monthly average temperature and the hourly temperature, Metroblue1 data for which the hourly temperature can be obtained was used.

Table 5.3 Verification of Temperatures by Using Temperature Correction Coefficients (Typical Places in Developing Countries)

Country City Uganda Jinja Tanzania Dar es Saalam Thailand Bangkok


As the diagram in Figure 5.4 below shows, Ct based on hourly temperature is slightly larger than Ct based on monthly average temperature, but the biggest difference is 0.008 in Bangkok. In other words, there was not a big difference which was similar to the results of verification in Japan.

1 Typical simulation weather data. Hourly temperatures are available for the last 30 years. (https://www.meteoblue.com)

A:horaly B:monthly (A-B) A:horaly B:monthly (A-B)

1 Okushiri 0.022 0.021 0.001 31 Hachiman 0.032 0.029 0.003

2 Wakinozawa 0.024 0.022 0.002 32 Kanayama 0.032 0.029 0.003

3 Nobechi 0.024 0.022 0.002 33 Kurokawa 0.030 0.027 0.003

4 Misawa 0.026 0.024 0.002 34 Nakatsugawa 0.035 0.031 0.003

5 Tobishima 0.029 0.028 0.001 35 Kanazawa 0.038 0.035 0.003

6 Hamanaka ー - - 36 Hakusankouchi 0.031 0.030 0.001

7 Tsuruoka 0.031 0.029 0.003 37 Sumoto 0.037 0.035 0.002

8 Ooizawa 0.024 0.021 0.003 38 Tomogashima ーーー

9 Yonezawa 0.030 0.027 0.003 39 Wakayama 0.043 0.040 0.003

10 Washikura 0.017 0.017 0.001 40 Nankishirahama ーーー

11 Kooriyama 0.030 0.027 0.003 41 Utsumi 0.037 0.035 0.003

12 Tamagawa ー - - 42 Imabari 0.039 0.037 0.003

13 Ishikawa 0.029 0.026 0.003 43 Matsuyama 0.042 0.039 0.003

14 Kitaibaraki 0.028 0.026 0.001 44 Hisakata 0.030 0.028 0.002

15 Kuki 0.035 0.032 0.003 45 Yusuhara 0.028 0.028 0.001

16 Saitama 0.037 0.033 0.003 46 Nakamura 0.040 0.037 0.003

17 Koshigaya 0.037 0.033 0.004 47 Shimizu 0.043 0.041 0.001

18 Nerima 0.038 0.035 0.004 48 Minakata 0.038 0.036 0.003

19 Edogawarinkai 0.034 0.033 0.002 49 Kuroki 0.039 0.035 0.004

20 NiiJima 0.039 0.037 0.002 50 Kahoku 0.038 0.034 0.004

21 Kisarazu 0.036 0.034 0.003 51 Kikuchi 0.040 0.036 0.003

22 Kamogawa 0.036 0.033 0.003 52 Kousa 0.042 0.038 0.004

23 Yokohama 0.036 0.034 0.002 53 Hitoyoshi 0.039 0.036 0.003

24 Miura 0.035 0.033 0.002 54 Kakutou 0.037 0.034 0.003

25 Namiai 0.023 0.021 0.002 55 Seito 0.042 0.039 0.003

26 Minamishinano 0.030 0.028 0.003 56 Kobayashi 0.038 0.035 0.003

27 Ikawa 0.026 0.024 0.002 57 Onoma 0.048 0.047 0.001

28 Fuji 0.037 0.034 0.002 58 Nase 0.056 0.054 0.002

29 Inatori 0.035 0.033 0.002 59 Naha 0.059 0.057 0.002

30 Nagataki 0.029 0.026 0.003 60 Oohara 0.060 0.060 0.000

StationTemperature correction coefficient (1985)

StationTemperature correction coefficient (1985)

Note: - N/A


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Weather data: Meteoblue (Y2018) Source: JICA Study Team

Figure 5.4 Verification of Temperature Correction Coefficients by Horary Temperature and Average Temperature by Month (Overseas)

From the above study results, the difference in Ct between hourly temperature and monthly average temperature in Japan and tropical countries is small, so it is possible to use monthly average temperature instead of hourly temperature for Ct calculation. In addition, it was confirmed that there was no significant difference in the calculation of the pavement temperature used for Ct using either the Akiyama equation or the pavement design handbook equation. Therefore, in this study, the equation described in the pavement design handbook, which is widely recognized as the standard book for pavement design, was adopted.

0.05

0.084

0.107

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

0.11

0.12

Jinja Dar Es Salaam Bangkok

Comparison of temperature correction coefficient(horaly data and monthly data)Ct

horalymonthly

0.081

0.048

0.099


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5.2 HWTD Information Collection

(1) Asphalt mixture evaluation method

In Japan, a wheel tracking test (referred to as a WT test) is widely used for evaluating plastic deformation of asphalt mixtures. The WT test was introduced by the Traffic Road Research Laboratory (TRRL) of Britain. In this test, small rubber wheels with a load travel back and forth on a sample of a specified size at a specified speed for a specified duration at a specified temperature and the dynamic stability (times/mm) is obtained from the degree of defamation per unit of time. However, since the test precision is effected when the value reaches 6,000 (times/mm), a caution is necessary in the judgment and handling of the value. For the test, a roller compactor, a mixer with capacity of 20 kg or more (a high mixing capacity for kneading the modifying material), and a mold are necessary in addition to a WT tester.

Definition of dynamic stability: Number of times that wheels pass through (for 15 minutes between 45 minutes and 60 minutes after the start of the wheel tracking test) until the sample is deformed by 1 mm. This is referred to as DS (Dynamic Stability).

On the other hand, a Hamburg Wheel Tracking Test (also called a Hamburg Wheel Tracking: referred to as a HWT test) is widely used around the world and is used as the world standard test. In the HWT test, tires pass through on a sample of an asphalt mixture and the amount of deformation itself is measured. As the differences from a WT test, the number of traveling times is 10,000 times (EN12697-22 test method) as opposed to 2,520 times and the degree of diachronic deformation before and after the test is measured, as opposed to the difference of the amount of deformation that occurred during the period between 45 minutes and 60 minutes. In this test, other detail properties (water resistance/abrasion resistance) can also be evaluated. (In Japan, water resistance and abrasion resistance are also verified by a water immersion WT test.) Objective and detailed tests are also possible for evaluating the deflection and depression of highly durable asphalt mixtures due to aging, which are assumed to be difficult to evaluate. In Japan, Nippon Road Co., Ltd. has a HWT tester for the research on the evaluation of rutting resistant asphalt mixtures to respond to heavy loads.

As the standard for evaluating rutting resistance with HWT, the HWT evaluation standard of South Africa that is described in (5) “Standard of evaluation by a HWT test” is available.

(2) Overview of the WT test

The Japanese standard and the British standard (BS standard) for WT tests are described below. The DS value is larger under the BS standard as the load is comparatively low, which is 520 kN, compared to that of the Japanese standard of 686 kN. The rule of the TR (deformation rate) equal to 5.0 mm/hr or lower under the BS standard is equivalent to 504 times/mm of the DS value. In the BS standard, two test temperatures, 60°C and 45°C, are applied and essentially, the standard is milder than the Japanese standard.


Figure 5.5 Relationship between the Duration of the Wheel Tracking Test and

Deformation


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Table 5.4 Comparison of WT Test Methods Country Japan Britain

Standard Pavement Survey and Test Method

Handbook B003 BS598-110※1

Tester (example)

Sample creation method

300 × 300 × 50 mm (Labo samples) 300 × 150 × 50 mm (sample excavated on-site)

305 × 305 × 50mm

Sample curing conditions

Unsoaked (Air) Unsoaked (Air)

Compaction Compaction degree 100%±1% -

Test objective Plastic deformation (rutting resistance)

evaluation Plastic deformation (rutting resistance)

evaluation Test temperature 60±2°C 45°C (standard)

Test duration (loading completion

conditions)

60 minutes after the start of loading or until the sample becomes deformed by 25 mm

45 minutes after the start of loading

Tester

Tire type Solid tire (JIS hardness 84) Solid rubber (BS hardness 80)

Tire shape W=5 cm, ϕ=20 cm W=5 cm, ϕ=20 cm

Load 686±10 N 520 N

Cycle 42±1 times/min

(two-way 21.0±0.5 times/min) 42 times±4/min

(two-way 21.0±2 times/min)

Traveling distance

230 mm 230 mm

Summary of results

Dynamic stability: DS (times/min)

Measure the displacement at the measuring point at the center of the sample. Calculate the displacement magnitude (mm/hr) per hour for the final 1/3 traveling cycle. In addition, assess the rutting of the sample based on the final displacement (maximum displacement) (mm).

Remarks

In Tokyo, in principle, an extracted core of 20 cm in diameter x 5 cm in thickness is applied as the sample. However, a section of 30 x 30 x 5cm (length/width/thickness) that is excavated from the site can also be used as the sample. The target DS varies depending on the shape of the sample.

*1 In Britain, the HWT test by EN12697-22 has been applied since 2011.



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Table 5.5 Comparison between the Threshold Values of BS Wheel Tracking Test and the Japanese Standard

Item Japanese standard BS standard

Analysis method

DS (times/mm) = 15 X 42/(d60-d45) d60: Deformation amount over 60 minutes d45: Deformation amount over 45 minutes

TR (mm/hour) =3.6(rn-r(n3) + 1.2(r(n-1)-r(n-2) rn: Deformation amount over n minutes

Conversion from TR=5.0 mm/

hr to DS

Number of passes over 60 minutes = 60 minutes x 42 times = 2,520 times Mm/hr = 2,520 mm/times

Therefore, since 5 mm/hr is translated to 5/2,520 mm/times, the inverse number of the value will be

DS = 2,520/5 = 504 times/mm. Maximum

rutting depth =7.0 mm

Deformation amount over 45 minutes of passing


In a WT test, when the DS value (dynamic stability) exceeds 6,000 times/mm, the value is to be reported as 6,000 times/mm or more. Since the mixture whose DS value is 6,000 times/mm or more is regarded as having the same performance, qualified assessment of high rutting resistance of asphalt concrete is regarded as a difficult proposition.

In the current WT test, after 2,520 passes (number of passes under the WT test 60 min x 42 times = 2,520 times/test), DS is determined by the deformation amount in the last one fourth (45-60 minutes). Therefore, the deformation amount of a high fluid resistance mixture of DS 6,000 times or more is 0.1 mm or less. This means that there is a problem in the test precision.

Example: The deformation amounts change for the duration from 45 minutes to 60 minutes as 0.10 mm→DS6,300, 0.09 mm→DS7,000, 0.08 mm→DS7,875, and 0.07 mm→DS9,000. The DS values fluctuate exponentially with the difference of 0.01 mm starting from around this level. The error varies greatly depending on the sensitivity of the device used for measuring the deformation amount. Therefore, the Test Method Handbook indicates that 6,000 or more is reported when DS exceeds 6,000.

(3) Standard for the plastic deformation wheel load (DS) obtained by a WT test (DS)

In Japan, the plastic deformation resistance is evaluated by the plastic deformation wheel load (DS value) that is obtained by a WT test as one of the indicators of the pavement performance regulation. The target DS values that are required by the MLIT Technical Standard for the major roads in Japan are 3,000 times/mm or more in the sections whose pavement plan traffic volume is 3,000 units/day or more, 1,500 times/min in the sections whose pavement plan traffic volume is less than 3,000 units/day, and 500 times/mm for roads other than major roads. The NEXCO Standard targets 800 times/mm for the straight asphalt of the sections other than high function pavement (drainage pavement) on highways with the large vehicle traffic volume class of less than 5,000 units per day in one direction in the initial year and 3,000 times/mm or more on the modified asphalt with the traffic volume of 5,000 units or more. The NEXCO Standards specifies the coping of the large vehicle traffic volume of 5,000 units/day under DS800 times/mm by straight asphalt. The targeted large vehicle traffic volume that is specified in the Standards seems to be higher in comparison to


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that of the MLIT Standards. The reason is assumed to be that the traveling speed is high on highways and the wheel load action time is short.

Table 5.6 Comparison of DS Standard Values of Japan


As shown above, the DS values that are obtained from straight asphalt are 500 times/mm or 800 times/mm or more according to the Standards of Japan. In addition, the Technical standards and Descriptions relating to the Pavement Structure indicates, “By using the upper limit area of the dynamic stability range that is obtained by adjusting the gradation of the asphalt mixture and the asphalt content by using straight asphalt as the reference, the DS value was determined to be 1,500 times/mm for major roads”. Therefore, the upper limit area of DS values of straight asphalt is assumed to be around 1,500 times/mm. In the actual constructions in overseas locations, as there are issues such as low-quality aggregates and differences of binder properties, there are some indications that securement of 1,500 times/mm may be difficult for straight asphalt. Therefore, data accumulation for the examination is required.

Outline of a HWT test

The standards for HWT tests for AASHTO (T324) and EN (12697-22) are described below. The test machines, test methods, testers, and evaluation methods vary according to the organization. The specifications of a HWT test and a WT test almost match, while the types of tires used and the result indicators (result summarization method) are different. This method is suitable for evaluating a high rutting resistance mixture that exceeds DS600 since the deformation amounts before and after the test are assessed after 10,000 passes with tires. While a WT test focuses on the difference of deformation amounts between 45 minutes and 60 minutes after the start of the test, a HWT test focuses on the deformation amounts of the sample itself before and after the test. As another feature,


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the test can be performed by immersing the sample in water, enabling evaluation of the performances such as waterproofing and abrasion resistance. According to the concept of a HWT test that is applied in Japan, the initial compaction amount varies depending on how the sample is created, how the sample is installed in the mold, and how the sample is adopted to the wheels. To remove the errors of the initial compaction deformation amount, testing from the duration point of 45 minutes, which is the primary linear displacement, is used.

Table 5.7 Comparison of HWT Test Methods Country USA Europe

Standard AASHTO T324-04 European Standard EN 12697-22

Small Size Device*2 (maximum axle loads <13 tons*2)

Divice (example)

Sample creation method ϕ150 mm, t=60 mm (Snowman shape) ϕ150 mm, t=60 mm

Sample curing conditions Soaked Unsoaked (Method A and Method B) or

Soaked (Method B)

Compaction rate SGC (Compaction rate 7%±0.5%) Compaction degree 99 to 101%

Test objective Plastic deformation (rutting) assessment and

abrasion resistance Plastic deformation (rutting) assessment and

abrasion resistance Test temperature 40 - 50°C 60°C

Test duration (loading completion conditions)

Wheels tested: After passing 20,000 times Deformation amount: Point of exceeding

40.90 mm

Method A (HRA: Hot Rolled Asphalt) Test wheel: After 1,000 passes (two-way)

Deformation amount: Point of exceeding 15 mm

Method B (AC & SMA) Test wheel: After 10,000 passes (two-way) Deformation amount: Point of exceeding 20

mm

Divice

Tire type Iron wheel Solid tire Tire shape W=47 cm, ϕ=20.32 cm W=45 to 55 mm, ϕ=200 to 205 mm Load 705±4.5 N 700±10 N

Cycle 50 times/min (two-way 25.0 times/min) 53 ± 2 times/min (two-way 26.5±1 times/min)

Distance Total width of the sample (around 230 mm) 230 mm

Summary of results

Number of passes up to SIP Deformation amount up to SIP: Creep Slope Damage count: Stripping Slope SIP: Stripping Infection Point

Procedure A Single measurement point Rut rate (µm/cycle) and rut depth (mm) Procedure B 25 measurement points Rut rate (mm/10³ cycles) and proportional rut depth (%)

Remarks

*2: In EN12697-22, a separate test method is specified for the axle loads of 13 t or more.



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(4) Standard of evaluation by a HWT test

As shown in the above table, since a sample is evaluated based on the deformation amount in a HWT test, the evaluation is simple and easy to understand such as ‘small deformation amount = high rutting resistance’ or high abrasion resistance. As AASHTO requires a water immersion test as a principle, an indicator called SIP (Stripping Infection Point) is also used.

According to Figure 5.6, by applying the number of passes in the horizontal axis and cumulative deformation amount (rutting depth) of the sample in the vertical axis, the deformation progresses instantly for the load in the initial state, however, the deformation ratio (gradient) changes to a straight line. When the load test is continued further, the deformation may progress instantly again at a certain number of passes. The number of passes at the boundary is defined as SIP and the number of passes at which stripping infection occurs. In general, the larger SIP is, the higher is the stripping resistance. SIP may not occur depending on the type of the mixture. The following tables show the examples of standards that are applied in the countries that apply a HWT test for evaluating mixtures as the standard.

Table 5.8 Standards of Evaluation Performed by Using HWT Tests (Tex-242-F)

Source: Asphalt Institute, USA

Table 5.9 Standards of Evaluation Performed by Using HWT Test (South Africa)

Source: Design and Use of Asphalt in Road Pavements Manual 35 / TRH 8 (2016)

(5) Correlation between a WT test and a HWT test

Only the Research Center of the Nippon Road Co., Ltd. currently has a HWT tester within Japan. Therefore, only the available reference material that indicates the relationship between a WT test and a HWT test is the ‘Evaluation of high rutting resistant mixture using a HWT test” that was presented at the 71st Academic Lecture (September 2016) of the Japan Society of Civil Engineers.

Source: Sabita Manual 35: Design and Use of Asphalt in Road Pavements

Figure 5.6 Conceptual Diagram of SIP


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Therefore, the following descriptions are the quotations from the reference material of the announcement.

Evaluation of high rutting resistant mixture using a HWT test (Research Center of the Nippon Road Co., Ltd.)

Overview of the test The test was conducted by using four types of dense graded asphalt concrete that are shown in Table 3 under the test conditions that are indicated in Table 2. A HWT test was conducted by creating a sample of 150 mm in diameter, 60 mm in thickness, and compaction rate of 7±2%, and a WT test was conducted by creating a WT sample by using a roller compactor, and the results were compared and examined.

Evaluation method Figure 2 shows the relationship between traveling times of the 4 types of asphalt concrete and the deformation amounts. The traveling time of HWT is longer than that of the WT test, however, the deformation curve is similar to that of the WT test. Since the deformation curve following the traveling time (45 minutes to 60 minutes) where DS is obtained by WT is not a straight line, evaluation was conducted multiple times in the same method as for DS. DS is evaluated for the final 15 minutes (1/4 of the traveling time) out of the entire traveling time of 60 minutes. For the HWT test also, in the same way, evaluation was performed by obtaining the ratios between the traveling speeds and the deformation amounts for 5 minutes from 15 minutes to 20 minutes, 15 minutes from 45 minutes to 60 minutes, and 100 minutes from 300 minutes to 400 minutes and by adding the traveling speeds. The absolute value of the deformation amount was included in the evaluation as it is important.

Test results Table 4 shows the results of the WT test and the HWT test. The results are examined as described below.

DS: As shown in Figure 3, regarding the relationship of DS between WT and HWT for


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the duration of 15 minutes to 20 minutes, although the determination coefficients are high, the sequence of III and IV is reserved. For the duration from 45 minutes to 60 minutes, the determination coefficients are even higher and the size relationship sequences between WT and DS match. For the duration from 300 minutes to 400 minutes, the size relationship of I and II and that of III and IV are reversed. Based on this, it is possible to consider that the evaluation of WT and that of HWT are almost the same. However, as the test duration increases, the evaluation of WT and the evaluation of HWT vary significantly.

Rutting depth: As shown in Table 4, the difference of D60 rutting depths between I and II is 0.63 mm, while the rutting depths of D400 are almost the same. The same is applied to III and IV.

D0: The results of the WT test and the HWT test showed that IV produced a favourable D0.

Visual observation: Based on the observation of the conditions of the samples after the HWT test as shown in Photograph 2, the deformation of asphalt concrete of II is inferior to that of I as it is larger. The samples of III and IV were hardly deformed; however, the deformation of III is slightly larger than that of IV.

Based on the above, the type III showed a favourable result in the conventional DS evaluation. However, in other indicators, the evaluation results were different including those of D0 of WT. In this way, judgement based on the DS by the deformation amount for the duration from 45 minutes to 60 minutes is insufficient for examining the characteristics and performance of asphalt concrete.

Based on the paper described above, WT and HWT are basically the same tests and only the load times (number of passes) and the evaluation methods are different. For the WT test also, the same evaluation as that of the HWT test can be performed by extending the test duration. Therefore, in the WT test also, it is assumed that the necessity for observation after 60 minutes is suggested.


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(6) Results of the hearing conducted from the Research Center of the Nippon Road Co., Ltd.

Hearing was conducted by Mr. Endo, the Assistant Manager of the Research Center of the Nippon Road Co., Ltd., which has a HWT tester. The summary of the hearing is outlined below.

WT test - In overseas locations, HWT tests are adopted as the mainstream. Although the reason for the

unpopularity of WT tests is not clear, the difficulty in understanding of the summarization method is considered to be one of the factors.

- The reason for the popularity of HWT tests may be attributed to its intuitive and easy-to-understand evaluation method. From a personal perspective, it is necessary to introduce an intuitive and easy-to-understand summarization method (deformation amount) to WT tests also.

What conditions are reproduced in a WT test and a HWT test? - Undoubtedly, severe conditions for mixtures are reproduced. In the Japanese test method,

conditions of a high pavement temperature and a slow speed are considered and tests are implemented under the most severe conditions.

- Some surface temperatures that are measured in developing countries exceed 60°C and in Japan also, there are many examples where the surface temperatures exceed 60°C. What is important is not surface temperature but the temperature of the raw material bed and verification is necessary for the condition under which it exceeds 60°C.

Correlation between a WT test and a HWT test - The Nippon Road Co., Ltd. has not implemented any tests relating to the correlation between

a WT test and a HWT test. The objective of the introduction of the tester is to evaluate high rutting resistance mixtures that cannot be evaluated by a WT test. As a personal view, the correlation does not have any significance.

WTD and HWTD - Possibility of replacement of WTD with HWTD, except for a test under the condition of

testing by immersing in water


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5.3 Information Collection Relating to PG

(1) What is PG (Performance Grade)?

For the asphalt binder standard, classification by penetration is applied by many countries. However, in response to the result of SHRP of the USA, transition of the standard for asphalt is progressing from penetration to PG (Performance Grade). In South Africa, its specific PG is set by referencing the PG standard of the USA and the operation is started.

Table 5.10 Types of Straight Asphalt

Country Standard Main category

Japan JIS K2207-1996 Penetration

USA ASTM D946-82 Penetration ASTM D6373-99 Pavement temperature PG

Europe (EN) EN 12591

Penetration Britain BS EN12591:2000 France NF EN12591:1991

Germany DIN EN12591:2000 China JTG F40-2004 Penetration & Climate

South Korea KSM 2201-88 Penetration

KSF 2389 (2004) Pavement temperature Same as ASTM D6373-99

Taiwan 60°C viscosity Source: Characteristics and Evaluation of Asphalt in the Pavement Engineering Library 13a

Source: Performance Grading of Bitumen, H. Bahia (The University of Wisconsin-Madison)

Figure 5.7 Grading System

(2) SHARP Superpave test items and evaluation items

In a SHRP Superpave test, by reproducing the original condition of the asphalt binder, the deterioration condition after heating the plant, and the deterioration condition after a long period of common use, the application limits are specified based on the characteristics at low temperatures and high temperatures. The PG is set in detail and the dynamic characteristics of the binder quality are also set. This is different from the index test that is used by other design standards as the main. The binder test items and the evaluation objectives are shown below.


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Table 5.11 Asphalt Assessment Tests in PG

Source: Superpave Fundamentals Reference Manual

(3) Selection of PG in a heavy traffic route

With the correction according to the traffic level and traffic speed in addition to the pavement temperature, the traffic condition is reflected in the PG selection.

Table 5.12 Correction of PG Considering the Traffic Condition

Source: Kingdom Of Saudi Arabia, Ministry of Transport: Hot Asphalt Mix Design System, September 2006

PG selection example in a heavy traffic route Base Grade PG 58-22 ・ for toll road: high Volume, PG 64-22 ・ for toll booth: high volume and slow traffic, PG 70-22 ・ for rest area :high volume and standing traffic, PG 76-22

Source: Performance Grading of Bitumen, H. Bahia (The University of Wisconsin-Madison)

(4) Relationship between the existing asphalt and PG

In Japan, in general, modified asphalt is applied for the road pavement from which rutting or low-temperature cracking is assumed. At the present situation, research relating to PG is not developing due to the substantial improvement of the performance of modified asphalt. At the present, the only information available is the “Viscoelasticity of the modified asphalt that is used in Hokkaido by the Superpave test”, which was obtained by the survey led in 2000 by the Hokkaido Regional Development Bureau. The overview and the results of the research are described below.

This test was implemented by applying one type each of straight asphalt, modified asphalt type I, and MA (Multi Asphalt) and 17 types of modified asphalt type II (of which 15 types are collected from the site). Figure 5.9 shows the results of available temperatures of each asphalt by plotting them on a range diagram of PG.


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Source: Superpave Specification Ver.1 (Deleted from the latest Superpave Standard)

Figure 5.8 Relationship between PG and Modified Asphalt

Source: Viscoelasticity of the modified asphalt used for the Superpave test in Hokkaido (Hokkaido Regional Development Bureau, Hokkaido University of Science)

Figure 5.9 Performance Grades of Various Binders (PG)

According to this result, many of modified asphalt type I and modified asphalt type II satisfy the performance requirement of PG70-22.


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5.4 Impact of High Pavement Temperature

(1) Impact of high pavement temperature

In the areas where high road surface temperatures are assumed throughout the year such as African countries, flow rutting of the surface layer is a major issue. The results of the road surface temperature measurement in Ethiopia that was implemented in the past operation, “Concept of the road improvement plan by the financial cooperation project for Africa (Ethiopia, Ghana, and Tanzania)”, show some cases where the road surface temperatures exceed 60°C.

In Japan, the following expression is established for the relationship between pavement temperature and strength (DS value) of asphalt pavement (using straight asphalt) based on the wheel tracking test.

Log10 (DS) = 8.656 – 0.07095T – 0.2285P

DS: Dynamic stability (times/m) T: Temperature (°C) P: Ground pressure (kgf/cm2)

Source: Questions and Answers on Pavement Technology (Volume 7-1)

The relational expression is shown in graphic format below. As shown in the graph, the strength deteriorates to 382 times/mm at 65°C and 169 times/mm at 70°C, which are 44% and 20% compared to the DS value of 864 times/mm at the normal test temperature (60°C). This indicates that rutting occurs more easily in asphalt pavement when hot days continue.

Source: Created by the Study Team based on the Questions and Answers on Pavement Technology (Volume 7-1).

Figure 5.10 Relationship between Pavement Temperature and Dynamic Stability

According to the result of the test that was implemented by the World Kaihatsu Kogyo Co., Ltd as the in-house research center, in the WT test conducted under the temperature 70°C2, the DS value is 913 times/mm under Standard condition (dense graded (13), OAC (6.3%), test temperature 60oC), while the DS value deteriorates to 261 times/mm, which is about 30% under the condition of Test temperature of 70°C. Since the result of the calculation expression that is described before indicates deterioration to 20%, the resistance deteriorates at the rate of 20% to 30% when the temperature increases from 60°C to 70°C for the pavement that uses straight asphalt.

2 The manufacturer guarantees the WT tester at the temperatures up to 60°C and does not guarantee the product performance under the temperature at 70°C. Normally, a request for testing at 70°C cannot be accepted.


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Table 5.13Conditions of the WT Test Conducted for Mixtures Name Mixture 2.36mm

pass rate (%) As. ratio(%) As. type Others

1 Dense graded (13)

Dense graded (13)

±0%

6.3% (OAC)

Straight asphalt 60/80

2 OAC+1% 7.3% (OAC+1%)

3 OAC-1% 5.3% (OAC-1%)

4 2.36mm+5% +5% 6.8% (OAC) 5 2.36mm-5% -5% 6.2% (OAC) 6 St.As.20/40

±0%

6.3% (OAC) Straight asphalt 20/40

7 Modified type II 6.3% (OAC) Polymer modified

asphalt type II

8 Test temperature 70℃ 6.3% (OAC)

Straight asphalt 60/80

Test temperature:

70℃ 9 Dense graded

(20) Dense graded (20)

6.0% (OAC)

10 21 times/min 6.0% (OAC) No. of

passes: 21 times/min

11 Dense graded gap (13)

Dense graded gap

(13) 5.5% (OAC)

Source: Extract from the in-house reference materials of the World Kaihatsu Kogyo Co., Ltd.

Source: Extract of the in-house reference material of the World Kaihatsu Kogyo Co., Ltd.

Figure 5.11 Result of the WT test by Condition

(2) Impact of high pavement temperature on modified asphalt

Hardly any information is available regarding the impact of the test temperature of 70°C on the modified asphalt. The only reference material that is currently available is the paper that was presented at “Japan Society of Civil Engineers, Tohoku Branch, Technical Research Presentation (2007): Impact of global warming on asphalt mixtures (Tohoku Institute of Technology)”. According to this paper, the ratio of the test result of sample V (dense graded asphalt mixture (13)) at 70°C (685 times/mm) to that at 60°C (242 times/mm) is about 30% , which matches the test result that is


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described above. The ratio of sample VII (modified type II dense graded asphalt mixture (13)) at 70°C to that at 60°C is about 17%.

Table 5.14 Test Conditions Sample name Conditions of mixture

V Dense graded asphalt mixture (13) VII Modified asphalt type II dense graded mixture (13)

VS Rutting resistance semi-blown dense graded asphalt mixture (13)

R Wood waste 100% asphalt mixture (13) R+V Recycled dense graded asphalt mixture (13)

Source: Created by the Study Team based on the Japan Society of Civil Engineers, Tohoku Branch, Technical Research Presentation (2007): Impact of global warming on asphalt mixtures (Tohoku Institute of Technology).

Source: Created by the Study Team based on the Japan Society of Civil Engineers, Tohoku Branch, Technical Research Presentation (2007): Impact of global warming on asphalt mixtures (Tohoku Institute of Technology).

Figure 5.12 Performance Grades of Various Binders (PG)

Although a conclusion cannot be reached from this result only, this study shows that the resistance to plastic deformation of the modified asphalt (type II) also deteriorates significantly under high temperatures. The cause seems to be the softening point temperature. Since the softening point temperature of both straight asphalt and modified asphalt type II is 60°C and lower, the resistance deteriorates instantly at a test temperature exceeding 60°C. Therefore, examination is necessary for the use of modified asphalt type III as well as the DS value setting method.

Table 5.15 Standards of Asphalt Softening Points

Type Softening point Price

(based on straight asphalt as 1.00) Straight asphalt (60/80) 48.0～56.0°C 1.00 Modified asphalt type II 56°C or higher 1.91 Modified asphalt type III 70°C or higher 2.35

Source: Extract from “Transition of modified asphalt standards of Japan”, Kansai Road Study Association, Pavement Study Committee


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5.5 Example of Using Modified Asphalt in JICA Gratis Projects

(1) What is modified asphalt?

Modified asphalt is described based on the reference materials that are presented in the homepage of the Japan Asphalt Association. Modified asphalt is produced by improving the properties of petroleum asphalt by adding polymer and natural asphalt and is used for improving various properties (rutting resistance, abrasion resistance, abrasion resistance, adhesion to aggregates, deflection followability of asphalt mixtures). Photograph 5.1 shows the result of the experiment where each piece of modified asphalt and straight asphalt is placed sideways in a beaker in a room at the temperature of 25°C and are left for one hour. The straight asphalt (left side of the photograph) flows out, while the modified asphalt (right side of the photograph) remains at the bottom without flowing out. Modified asphalt with such a feature enables pavement to be highly durable.

(2) Types of modified asphalt

The types of modified asphalt are classified into the major categories as shown in Figure 5.13. For these types, asphalt that is modified by using polymer such as SBS (Styrene-butadiene thermoplastic elastomer) is referred to as polymer modified asphalt. The polymer modified asphalt that is produced by adding polymer in a factory in advance is referred to as a pre-mix type and the polymer modified asphalt that is produced by directly adding polymer in the mixture production plant is referred to as a plant mix type. The plant mix type is a modifying material that enables production of a modified asphalt mixture in a normal asphalt plant. Semi-blown asphalt is a modified asphalt that is produced for coping with the traffic load by hardening the straight asphalt by deliberately degrading it through oxidization by blowing air into the asphalt. Hard asphalt is produced by mixing straight asphalt with the hard asphalt that is naturally mined.

Source: HP of Japan Asphalt Association

Figure 5.13 Classification of Types of Modified Asphalt

The modified asphalt types are classified according to the application purpose as shown below.

(Left: Straight asphalt Right: Modified asphalt)

Source: HP of Japan Asphalt Association

Photo 5.1 State where Asphalt Flowing Out

Improved asphalt

Hard asphalt

Polymer modified asphalt

Semi-blown asphalt

Pre-mix type

Plant mix type


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Table 5.16 Classification of Modified Asphalt Types within Japan

Source: Pavement Construction Handbook, 2006 (Japan Road Association)

Modified asphalt types are classified into two types, a pre-mix type and a plant mix type. The pre-mix type is produced by the manufacturer by mixing a modifying material to the straight asphalt in advance and the plant mix type is a modifying material for producing a modified asphalt mixture by directly supplying the modifying material in a mixer in a normal asphalt plant.

A pre-mix type is delivered to an asphalt plant by a tanker and is usually supplied to a tank for modified asphalt of the asphalt plant. A modified asphalt mixture is produced by dry-mixing the modified asphalt that is stored in the tank with stones, sand, stone dust in a mixer, spraying, and wet-mixing the mixture. When two or more asphalt tanks are available, in general, one of the tanks is exclusively used for modification. When only one asphalt tank is available, a hose is directly connected to the asphalt measuring tank of the asphalt plant from the asphalt tanker. In this case, a dedicated tanker is necessary.

For a plant mix type, modifying materials that are produced by the manufacturer are delivered to an asphalt plant in a packing style such as a drum or container. The SBR that is stored in a drum or a container is measured and supplied by a supplying device (such as a conveyor belt) or manually, sprayed and mixed in the section where stones, sand, stone dust were mixed in a mixer. A plant mix type is designed to be dissolved and dispersed to straight asphalt in a short time. Its performance is demonstrated in this way. Therefore, in Japan, modified asphalt can be produced without special equipment for the plant mix.

(3) Notes on using modified asphalt manufactured in Japan

In overseas locations, the following points must be noted when using modified asphalt that is manufactured in Japan.

Pre-mix type The modified asphalt that is used in Japan can be stored for about one month. The asphalt cannot be stored longer than that period. If modified asphalt is to be brought from Japan, it is delivered in a drum and a separate facility is necessary for heating the asphalt, requiring extra efforts ( this can be cumbersome).

Plant mix type The modifying materials that are used in Japan can be used as they are. However, since they are after all the modifying materials suitable for the asphalt used in Japan, the degree of compatibility with the asphalt in overseas locations is unclear although the same effects can be expected to some extent. Therefore, testing is necessary for the compatibility with the asphalt

Added notation Ⅲ type-W

Ⅲ type-WF H type-F

Applied mixture

Main applied parts

◎

◎ ◎ ◎ ◎

◎ ○ ○ ○ ○Abrasion resistance ◎ ◎ ○ ○ ○Aggregate fly-off resistance ○ ◎Water resistance ○ ○ ◎

Small flexure ○ ○ ◎ ◎(As base layer)Large flexure ◎ ◎(As base layer)

◎ ◎Added notation abbreviations W: Water resistance　F: FlexibilityLegend　◎：High applicability　○：Application is possible 　No mark: Application can be considered but examination is needed

Bridge surfaces (concrete plates)

Flexure following performance Bridge surfaces(steel plates)

Drainage (permeability)

Used often in dense, fine, coarse mixtures, etc.Mainly the added amount of polymer differs

between the Ⅰ type, Ⅱ type and Ⅲ type.

Used in gooseasphalt mixture

Snowy and cold areas

Plastic deformation resistanceGeneral partsAreas of heavy large-vehicle trafficAreas and intersections of very heavy

Type

Mixture functions

Polymer Modified AsphaltSemi-blown

asphalt

Used in porousasphalt mixtures.Modified asphalt

with a lot of addedpolymer.

Used in dense andcoarse mixtures,etc. Asphalt withimproved plastic

deformationresistance

Hard asphaltⅠ type Ⅱ type Ⅲ type H type


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in Japan. (4) Application examples of modified asphalt in JICA projects

In the African countries whether the temperatures are high and, in general, large vehicles travel at low speeds, flow rutting countermeasures are urgently required for the slopes and intersections of the roads that are paved with asphalt. As the measures to respond to this issue, cases of using modified asphalt in the JICA projects are increasing. (see Table 5.17)

However, in African countries, pre-mix type modified asphalt is not sold except in some countries. Therefore, the following methods can be considered for constructing modified asphalt pavement.

[Batch plant]

Almost all asphalt plants operating in Japan and those installed in grant aid projects are the batch type, and this type is also becoming increasingly widespread in other countries. The following can be considered as the modified asphalt manufacturing method when using this type of plant.

In a batch type asphalt mixture plant, the asphalt mixture and modifying material (admixture) are inserted from the inspection port. (Insertion port, inspection port, installation (improvement) of insertion port, etc., making it easy to manufacture modified asphalt mixture in the plant)

The modified asphalt (for example, premix produced in South Africa, etc.) is imported.

A small modified asphalt plant (polymer modified asphalt (PMB) manufacturing plant) is installed to manufacture the modified asphalt. (See Photograph 5.1)

Photo 5.2 Example of PMB Manufacturing Plant based on Grant Aid (Liberia)


[Continuous Mix plant]

Most asphalt plants in developing countries, especially African nations, adopt continuous mechanisms. Importing premixed modified asphalt or installing PMB manufacturing plants does not present any technical issues, however, when using additive-type modifying materials, it becomes necessary to consider initially storing produced mixture in a temperature-insulating silo and then mix in the modifying material using an after mixer (additionally installed) just before shipping. Mixing in the modifying materials during the cold bin materials mixing process can also be considered, however, currently no stable mixing technology has been confirmed.


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Table 5.17 Classification of Modified Asphalt Types within Japan



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5.6 Information Collection Relating to Problem Soils and Special Soils

Standards are available for the countermeasures for problem soils (black cotton soil, etc.) in South African and East African countries and these standards are described/introduced in the Handbook.

(1) Black cotton soil

For the judgment methods and countermeasure constructions of an expansive soil (black cotton soil) standards of Australia, South Africa, Tanzania, and Ethiopia are available as a result of the previous studies. As the countermeasure constructions, water shielding, replacement, installation of a capping layer (between subbase course and subgrade), and lime stabilization are available. However, no standards are available for the materials that are used. Therefore, examples of the standards used for the materials that are used for replacement construction in Australia are added. A series of standards relating to expansive soils in Australia is introduced below.

Expansive soil judgement method in Australia

Table 5.18 shows the expansive soil judgment standards that are shown in the section of Part 2 Pavement Structural Design, in the Austroads Pavement Guideline in Australia. Although the expansion rate can be judged by PI to some extent, however, it is desirable to make a judgement based on the expansion rates by conducting expansibility tests.

Table 5.18 Expansive Soil Judgment Standards in Australia

Expansibility Liquid limit (%) Plasticity index (PI) PI x % < 0.425 mm Expansion

rate* Very high > 70 > 45 > 3200 > 5.0

High > 70 > 45 2200 - 3200 2.5 – 5.0 Moderate 50 - 70 25 - 45 1200 - 2200 0.5 – 2.5

Low < 50 < 25 < 1200 < 0.5 * The expansion rate is measured by the Standard method under OMC, where 98% MDD (modified dry density),

4-day water immersion, and 4.5 kg surcharge are applied. Source: Austroads, Guide to Pavement Technology, Part 2 Pavement Structural Design

Countermeasure construction in Australia

In the Pavement Structural Design section in the Guideline to Pavement, a capping layer is installed between subbase course and subgrade to prevent infiltration of water to the expansive soil. The thickness of the capping layer is 150 mm or more. An embankment is installed to control deformation of the pavement surface and ensure traveling comfort. In the supplementary standards for pavement structure design that are applied by Queensland and Victoria, in the case where the expansibilities are large but no detail soil survey is implemented, the embankment thickness can be determined based on the data that is shown in Figure 5.14.


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Source: VicRoads, Code of Practice, Selection and Design of Pavements and Surfacings RC 500.22, October 2013A

Figure 5.14 Thickness of an Embankment Layer of Expansive Soil of High Expandability

Material specification (added in this Study)

The road construction specification (VicRoad) that is applied in Victroa specifies the use of type A materials for the countermeasure construction of expansive soils. The type A material standard is shown in Table 5.19.

Table 5.19 Material Standard in Australia (Victoria)

Source: VicRoads, Standard Specification Sections for Roadworks and Bridgeworks, February 2016

(2) Laterite

Laterite is a red weathered product that mainly comprises iron oxide and aluminium oxide. Rocks are significantly weathered under the tropical environment of high temperature and high humidity and components other than those two components are leached and, as a result, laterite is created. Laterite has a low plasticity and does not absorb moisture easily once it is dehydrated. Laterite forms a specific honeycomb or slag structure or a cementation layer rich in iron oxide concretion of pisolite shape on a ground surface or shallow area. Laterite is mainly deposited in the areas that are shown in Figure 5.15.


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Source: Review of Specifications for the Use of Laterite in Road Pavements (Contract: AFCAP/GEN/124) 2014.05

Figure 5.15 Global Laterite Deposition Map

Specification relating to a laterite base course

The review on the specification relating to the use of laterite for road pavement in AFCAP is reported in “Review of Specifications for the Use of Laterite in Road Pavements”. Krinitzsky et al recommend the following as the criteria of a laterite base course. Table 5.21 shows the comparison of base course specification in 13 African countries. It should be noted that the CBR values in the table are as high as 50-100.

Table 5.20 Criteria Recommended for a Laterite Base Course

*Class I – III：traffic categories in Ghana.

Source: Review of Specifications for the Use of Laterite in Road Pavements

Table 5.21 Outline of Base Course Specifications of 13 African Counties

Source: Review of Specifications for the Use of Laterite in Road Pavements


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5.7 Review and Comparison of Pavement Construction Management Standards and Construction Supervision Standards

(1) Comparison and summarization of the construction management standard of each project

1) Examination outline

Construction supervision standards relating to pavement for overseas projects are collected and summarized and the various types of test information (“test method”, “standard value”, and “test frequency”) are compared and summarized.

2) Review

The applied test methods and standards of the reference source of the values that are applied in each project are summarized.

・ AASHTO is applied by most countries, while some countries have their own standard with BS. JIS is hardly applied.

・ Some African countries apply the standards of the former colonial power. (Former colonial power: Britain) → BS

・ Some countries apply the same standards for construction and material with AASHTO and some countries apply a mixture of ASSHT0 and BS. It is assumed that such countries initially applied either ASSHT0 or BS; however, the insufficiency of test methods was supplemented by the cooperation of the donor.

(2) Review and comparison of the pavement construction management standards and the construction supervision standards

Based on the pavement construction standards in Japan and overseas, past work specifications, and construction supervision standards were reviewed and organized the contents, actual conditions and characteristics of application. Standards were compared in two stages: material/test and construction.

1) Materials and tests

Table 5.22 Examples of Martial Standards (ORN31)

Material Required standard

Embankment material

The upper 500 mm of soil immediately beneath the subbase or capping layer i.e. the top of the embankment fill or the natural subgrade, should be well compacted In practice this means that a minimum level of 93 - 95 per cent of the maximum dry density obtained in the British Standard (Heavy) Compaction Test.


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Subgrade material

Category (1). Subgrades where the water table is sufficiently close to the ground surface to control the subgrade moisture content. The type of subgrade soil governs the depth below the road surface at which a water table becomes the dominant influence on the subgrade moisture content. For example, in non-plastic soils the water table will dominate the subgrade moisture content when it rises to within 1 m of the road surface, in sandy clays (PI < 20 per cent) the water table will dominate when it rises to within 3 m of the road surface, and in heavy clays (PI > 40 per cent) the water table will dominate when it rises to within 7 m of the road surface. In addition to areas where the water table is maintained by rainfall, this category includes coastal strips and flood plains where the water table is maintained by the sea, by a lake or by a river. Category (2). Subgrades with deep water tables and where rainfall is sufficient to produce significant changes in moisture conditions under the road. These conditions occur when rainfall exceeds evapotranspiration for at least two months of the year. The rainfall in such areas is usually greater than 250 mm per year and is often seasonal. Category (3). Subgrades in areas with no permanent water table near the ground surface and where the climate is dry throughout most of the year with an annual rainfall of 250 mm or less.

Selected subgrade

material and Capping

Layer

These materials are often required to provide sufficient cover on weak subgrades. They are used in the lower pavement layers as a replacement for a thick subbase to reduce costs. The requirements are less strict than for sub-bases. A minimum CBR of 15 per cent is specified at the highest anticipated moisture content measured on samples compacted in the laboratory at the specified field density.

Subbase course

material

A minimum CBR of 30 per cent is required at the highest anticipated moisture content when compacted to the specified field density, usually a minimum of 95 per cent of the maximum dry density achieved in the British Standard (Heavy)

Base course material

Graded crushed stone (GB1, A and GB1, B). Two types of material are defined in this category. One is produced by crushing fresh, quarried rock (GB1, A) and may be an all-in product, usually termed a `crusher-run', or alternatively the material may be separated by screening and recombined to produce a desired gradation. The other is derived from crushing and screening natural granular material, rocks or boulders (GB1, B) and may contain a proportion of natural, fine aggregate.

Source: ORN31

Table 5.23 Examples of Granular Material Standards (ORN31)

Material Code Description Summary of Specification


GB1, A Fresh, Crushed Rock Dense graded unweathered stone. Non-plastic parent fines

GB1, B Crushed Rock, Gravel or boulders

Dense grading, PI < 6, soil or parent fines.

GB2, A Dry-bound macadam Aggregate properties as for GB1, B PI < 6


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GB2, B Water-bound macadam Aggregate properties as for GB1, B PI < 6

GB3

Natural coarsely graded granular material including processed and modified gravels

Dense grading, PI < 6

Subbase course

material GS Natural Gravel CBR after soaking > 80

Capping layer GC Gravel and gravel-soil Dense graded, CBR after soaking > 15

Source: ORN31

Table 5.24 Examples of Material Standards (Pavement Design Handbook/Pavement Construction Handbook)

Material Required standard Embankment

material None

Subgrade material

CBR tests shall be conducted from the section of 50 cm or more in depth from the subgrade surface after disturbing the soil. When the CBR test result is 3 or lower, improvement shall be made so that the designed CBR becomes 3 or higher.

Selected subgrade material and

Capping Layer

Compaction rate 90% When the modified CBR is 20 or more, 20 shall be used as the assessed value.

Subbase course material

CBR 20 or more by modification with crusher-run, iron and steel slug, sand, etc. Cement stabilization unconfined compressive strength [7 days] 0.98 MPa Lime stabilization unconfined compressive strength [10 days] 0.7 MPa


Bituminous stabilization Hot mix: Stability 3.43 kN or higher Normal temperature mix: Stability 2.45 kN or higher Cement/bituminous stabilization Unconfined compressive strength (7 days) 1.5 ~ 2.9 MPa Primary displacement (7 days) 5 ~ 30 (1/100 cm) Residual strength rate (7 days) 65% or more Cement stabilization unconfined compressive strength [7 days] 2.9 MPa Lime stabilization unconfined compressive strength [10 days] 0.98 MPa Granularity adjusted crushed stone/granularity adjusted iron and steel slug Modified CBR 80 or higher Hydraulicity and granularity adjusted iron and steel slug Modified CBR 80 or higher, Unconfined compressive strength [14 days] 1.2 MPa

Source: Pavement Design Handbook/Pavement Construction Handbook

Table 5.25 Examples of Material Standards (SATCC)

Material Required standard

Embankment material

TRH-14: No statement SATCC: Depth below final surface 0.0 m – 1.2 m: Minimum soaked CBR = 3% at 90% modified AASHTO density


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1.2 m – 9.0 m: Minimum soaked CBR = 3% at 100% modified AASHTO density

Subgrade material

No grading requirements Minimum CBR at in-situ density = 10% (G8); 7% (G9); and 3% (G10) Maximum swell at 100 % mod AASHTO density = 1.5%

Selected subgrade

material and Capping Layer

Minimum soaked CBR at 93% modified AASHTO density = 25% (G6); 15% (G7); PI should not exceed 12%; in the case of G6 or G7 material with a large coarse fraction, a higher PI of soil fines may be acceptable. In such case PI may be given by the formula Maximum PI = 3 × Grading Modulus (GM) + 10 Maximum swell at 100 % mod AASHTO density = 1.0% (G6); 1.5% (G7 ) GM minimum 1.2 (G6); 0.75 (G7)

Subbase course material

Minimum soaked CBR = 30% at 95% modified AASHTO density Maximum PI = 10 Maximum swell at 100 % mod AASHTO density = 0.5% (G5); 1.0% (G6 ) GM minimum 1.5 (G5); 1.2 (G6) can be authorized by the Engineer


Minimum soaked CBR = 80% at 98% modified AASHTO density Maximum PI = 6 (G2, G3, G4). For stabilized soil shall not exceed 6% after treatment Maximum swell at 100 % mod AASHTO density = 0.2% (G2, G3, G4) GM minimum 2.0 for untreated material or 1.7 if material are to be chemically stabilized Maximum linear shrinkage = 3% (G2, G3, G4)

*GM = (300 - (P2.00 mm + P0.425 mm + P0.075 mm))/100 P2.00 mm, etc., denotes the percentage passing through the sieve size.

Source: SATCC

Table 5.26 Examples of Asphalt Mixture Materials (1)

Standard Pavement Design Handbook Superpave Method; AASHTO M323-07, R35-09)

Asphalt

Petroleum asphalt for pavement: Four penetration grades (40/60, 60/80, 80/100, and 100/120)

Improved asphalt: Four types of polymer improvement (type I, type II, type III, and type H)

Performance grade PG binder: Select based on the highest pavement temperature and the lowest pavement temperature.

Correct the grade on the high temperature side based on the traffic level and the traffic speed.

Emulsion Tack coat: Cation type PK-4 Prime coat: Cation type PK-3

Coarse aggregate material

Crushed stone (JIS A5501, Japan Road Association): Granularity, dry surface density, water absorption rate, abrasive weight loss, stability loss, harmful substance content (clay, soft stone pieces, long thin or flat type)

Crushed gravel: Same as the number of fracture surfaces + crushed stones

Angulation (number of fracture surfaces) Flatness and fineness ratio granularity Los Angeles abrasive weight loss Stability • and are common items among the

road institutions. and are determined by the road institutions.


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Ballast: Same as crushed stones

Fine aggregate material

Natural sand Artificial sand Screenings: Granularity

Angulation (porosity of the uncompacted aggregate in a loose state)

Amount of clay (sand equivalent) Stability Harmful substance content • and are common items among the

road institutions. and are determined by the road institutions.

Filler Limestone dust: Granularity Other than Limestone dust: PI,

etc.

Mixture

9 types of mixtures (its application depends on the section used): Dense graded, fine graded, dense graded gap, open graded, porous, etc.

Specify the maximum particle size and granularity range of the aggregate material for each type.

Mixture types: Primarily, dense graded type.

The maximum particle size of the surface layer mixture is between 4.75 mm and 19 mm.

Set an aggregate granularity within the upper and lower limit values of the granularity control point. Coarse aggregates are defined as follows: In the case of the maximum particle size of 19 mm, 4.75 mm and sieve pass-through rate of less than 47% and in the case of the maximum particle size of 12.5 mm, 2.36 mm and sieve pass-through rate of less than 39%. Others are defined as fine graded.

Remarks - These are the structural design guidelines

and the descriptions in the table are based on the Superpave method.


Table 5.27 Examples of Asphalt Mixture Materials (2) Standard Road Note 19 SATCC

Asphalt

Penetration grade asphalt: 40/50, 60/70 (recommended), 80/100 (The specification is indicated in Road Note 19.)

ORN 31 is recommended.

Coarse aggregate material

Crushed stones and crushed gravel: Cleanness, particle shape, strength, abrasion, polishing, stability, water absorbency, and flaking resistance


Fine aggregate material

Crushed rocks and natural sand: Cleanness and stability


Filler Fine aggregate of crushed rocks, cement, and slaked lime


Mixture types

3 types of mixtures: Asphalt concrete, dense bitumen macadam, and hot rolled asphalt



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Remarks

ORN 19 was prepared by updating the contents of ORN 31 by supplementing the items relating to the heated asphalt mixture.

These are the structure design working rules (proposal) and ORN 31 is recommended for the specification of the asphalt mixtures.


2) Types of mixtures

At the selection of the asphalt mixtures, weather conditions, local conditions, traffic conditions, material conditions, the finished thickness of one layer, and the construction method should be taken into consideration.

A) Types of asphalt mixtures are classified into continuous graded (dense graded), gap graded, and open graded. The conceptual diagrams of these gradations are shown below.

- Source: JICA Study Team

Figure 5.16 Conceptual Diagram of Gradations

B) The aggregate of 20 mm in the maximum particle size and the aggregate of 13 mm in the maximum particle size are compared. In general, the former type is superior in terms of flow resistance, abrasion proof, and skid resistance and the latter are superior in terms of water-proofing and cracks.

C) In general, under the heavy traffic condition, mixtures superior in the flow property resistance are applied to surface layers and in other cases, mixtures superior in deflection property/water-proofing and high resistance to cracking are selected.

Continuous graded Gap graded Open graded

Aggregate sizes are widelydistributed, smallaggregates fill gapsbetween large aggregates,gaps between aggregatesare small and dense, andinterlock is high. Most ofthe applicable ACpavements are of this type.

Except for some ranges ofaggregate sizes, coarseaggregates form a skeletonto provide interlock and fillthe interstices of coarseaggregate with filler.

Since the number ofcontacts between theaggregates is small, theeffect of the interlock issmall.


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Table 5.28 Type of Mixture and Gradations

Design standard

Pavement Construction

Handbook ORN19 Superpave

Mixture type

Dense graded

Dense graded

Dense graded

Dense graded

Dense graded

Dense graded type*

Dense graded type*

Dense graded type*

Maximum aggregate size (mm)

20 13 19 12.5 9.5 19* 12.5* 9.5*

26.5 100 25 100 100

19.0 95 - 100 100 90 - 100 100 90 - 100 100

13.2 75 - 90 95 - 100

12.5 90 - 100 100

-90 (upper limit only)

90 - 100 100

9.5 56 - 80 90 - 100

-90 (upper

limit only 90 - 100

4.75 45 - 65 55 - 70 35 - 65 44 - 74 55 - 85 -90

(upper limit only

2.36 35 - 50 35 - 50 23 - 49 28 - 58 32 - 67 23 - 49 28 - 58 32 - 67 0.6 18 - 30 18 - 30 0.3 10 - 21 10 - 21 5 - 19 5 - 21 7 - 23 0.15 6 - 16 6 - 16

0.075 4 - 8 4 - 8 2 - 8 2 - 10 2 - 10 2 - 8 2 - 10 2 - 10

* All the Superpave mixtures are dense graded type. In Superpave, pass-through rates are set under main control sieving as shown below and the mixtures whose granularity curve is below the setting values are called coarse mixtures and mixtures whose granularity curve is above the setting values are called fine mixtures.


Pass-through rate (%) at the main control point in the maximum particle size and the maximum nominal size of mixtures

Maximum particle size of aggregate (mm) 19.0 12.5 9.5 Sieve opening at the main control point (mm) 4.75 2.36 2.36

Sieve opening pass-through rate at the main control point (%) 47 39 47

Source: AASHTO MP 1


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3) Construction managent for base/subbase course

In the case of granular base/subbase materials, the water content (optimum water content) and gradation of materials greatly impact the compaction characteristics. Accordingly, large fluctuations in water content and gradation during construction can lead to inadequate base/subbase compaction, which in turn leads to early pavement damage.

In Japan, the optimum moisture content (OMC) and maximum dry density (MDD) of embankment and base/subbase materials are sought according to “JISA 1210 Ramming Compaction Test (”Handbook of Pavement Survey and Test Methods”), and the degree of compaction is managed onsite based on the MDD. The ramming method in the “ramming test” when deciding the standard density comprises five types A~E, and these are divided into the following two types according to the impact load (Ec).

JIS name A, B “Standard method” Ec≒550kJ/m3 JIS name C, D, E “Modified method” Ec≒2500kJ/m3

Table 5.29 Ramming Compaction Test

Source: Handbook of Pavement Survey and Test Methods

Table 5.30 shows a comparison of the standard method and modified method.

Table 5.30 Ramming Compaction Test (Standard Method and Modified Method)

Item Standard Method Modified Method

Applicable standard Stipulated as unconfined compression strength

Stipulated as corrected CBR

Rammer weight 2.5kg 4.5kg Rammer falling height 30cm 45cm Number of compaction 25times, 3 layers 92 times, 3 layers Onsite compaction specification

100% or more 95% or more

Source: Handbook of Pavement Survey and Test Methods

When each test is implemented using the same materials, the MDD tends to be smaller and OMC larger in the standard method compared to the modified. In other words, the standard density differs depending on which method is used to implement the ramming test. In Japan, the standard specified value for the degree of compaction in the base is given as 95% or more of standard density in the modified method. Meanwhile, the specified degree of compaction is sometimes set at 100% or more in overseas countries. For example, as is shown in Table 5.31, standard density is sometimes prescribed according to the standard method in Australia, and in such cases the degree of compaction must be set at 100% or more.

Compactionmethods

Molddiameter

(mm)

Molddepth

(sampleheight)(mm)

Mold(sample)bulk

(cm3)

Rammerweight(kg)

Falling height(cm)

Number ofcompaction

(number)

Layernumber

Permissiblemax.

aggregate size(mm)

Ec(kJ/m3)

A 100 127.3 1,000 2.5 30 25 3 19 552

B 150 125 2,209 2.5 30 55 3 37.5 549

C 100 127.3 1,000 4.5 45 25 5 19 2,482

D 150 125 2,209 4.5 45 55 5 19 2,472

E 150 125 2,209 4.5 45 92 5 37.5 2,481


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Table 5.31 Examples of Degree of Compaction Specifications (Standard Method) (Australia)

Item Specified degree of compaction

Subbase Base

QDMR, Queensland Province (Type 1) ≥102% (standard) ≥102% (standard)

QDMR, Queensland Province (Types 2, 3, 4) ≥100% (standard) ≥100% (standard)

RTA, New South Wales Province ≥102% (standard) ≥102% (standard)

VicRoads, VIC (Scale A) ≥98.0% (modified) ≥100% (modified)

VicRoads, VIC (Scale B) ≥97.0% (modified) ≥98.0% (modified) Source: QDMR, RTA (2007a)

Also, as examples of seeking 100% or more of the standard density set in the modified method and constructing harder base, Table 5.32 shows standards in Australia (Victoria), South Africa, Eastern Africa (Tanzania, Uganda, etc.) and so on.

Table 5.32 Examples of 100% or Higher Specified Compaction (Modified Method)

Standard Specified Compaction

(Base course) Remarks (targets)

VicRoads (2008b) ≥100%（modified） -

TRH4 100 - 102 % mod AASHTO G2: GRADED CRUSHED STONE

General Specification for Road and Bridge Works, Uganda

102% of BS-Heavy CRR（Crushed Rock）


The following effects can be gained through adopting 100% or higher compaction in the base course (high compaction).

The asphalt layer can be made thinner. The bottom surface of the asphalt has smaller tensile stress and is less prone to cracking. Less cement can be used for cement stabilization. It is more economical.


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4) Permissible deviate gradation

Based on the gradation of the onsite mixing conducted through test kneading, quality control is implemented in the asphalt plant when manufacturing the asphalt mixture in the plant, however, concerning deviate gradation (deviations from the onsite mixing) at this time, because the permissible deviate gradation differs according to standard as shown in Table 5.33, it is necessary to confirm standards in the counterpart country. Moreover, caution is needed because the control threshold example concerning heated asphalt mixture gradation indicated in the Pavement Construction Handbook differs greatly from current international standards.

Table 5.33 Permissible Deviate Gradations (Examples)

Note 1: Standard Specification for Road Works, Tanzania Note 2: Interim Guideline for the Design of Hot-Mix Asphalt, Tanzania


CountryMixture

Particle size(mm)Upper limit

(%)Lower limit

(%)Upper limit

(%)Lower limit

(%)28252019 100 100 100 10014

13.2 95 100 95 10012.5109.5 - - - -7.16.35

4.75 55 70 55 70 ±5.02.36 35 50 ±15.0 35 50 ±4.0

21.18

10.6 18 30 18 30 ±3.00.3 10 21 10 21 ±3.00.15 6 16 6 16 ±3.0

0.075 4 8 ±5.0 4 8 ±1.5CountryMixture

Particle size(mm)Upper limit

(%)Lower limit

(%)Upper limit

(%)Lower limit

(%) Note 1 Note 2

28 ±5.0 ±4.025 ±3.020 100 ±5.0 100 ±4.019 ±3.014 80 100 ±5.0 85 100 ±5.0

13.212.5 ±3.010 85 ±5.0 72 94 ±5.09.5 ±3.07.1 ±5.06.3 ±5.05 ±4.0 52 72 ±5.0

4.75 ±3.02.36 37 55 ±2.0

2 28 58 ±4.0 ±4.01.18 26 41 ±4.0 ±2.0

1 ±4.00.6 ±4.0 16 28 ±4.0 ±2.00.3 ±3.0 12 20 ±4.0 ±2.00.15 ±2.0 8 15 ±3.0 ±2.0

0.075 2 10 ±1.0 4 10 ±1.5 ±0.7

Japan (Pavement Construction Handbook) Japan (NEXCO)Dense grading (13mm) Permissible

deviation

TYPE A (13mm) Permissibledeviation

South Africa TanzaniaNMPS (Nominal Maximum Permissible

deviation

AC14 Permissible deviation


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5.8 Cost Comparison between Modified Asphalt Pavement and Cement Pavement

(1) Overview of the cost comparison

As a part of the countermeasures for rutting in road pavement, the life cycle cost of the modified asphalt and/or concrete pavement that is effective for rutting is compared based on the unit price of material and unit cost of direct work. The comparison target countries were Cambodia, Uganda and Tanzania which construction cost data were available and Japan. The types of pavements used for comparison are dense-grained asphalt, modified asphalt and concrete pavement.

(2) Life cycle cost calculation conditions

As long as there is a need to maintain the performance of pavement above a certain level, pavement will be constructed (new pavement or reconstructed pavement), put into service, repaired when traffic loads cause the performance to deteriorate, and if performance cannot be improved through repairs, then pavement will have to be reconstructed (roads will have to be repaved). This cycle from construction of pavement to the next construction is referred to as the pavement life cycle, and the costs that are related to it are called life cycle costs. There are generally three major expenses used in life cycle cost calculations: road management expenses, road user expenses, and roadside and local community expenses. Table 5.34 shows the typical items included in the various expense categories. It is not always necessary to consider all of these items in life cycle cost calculations. The items to be included depending on the purpose of the calculations and the required accuracy, construction conditions, traffic conditions, roadside and local community conditions, etc.


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Table 5.34 Examples of Expense Items Included in Pavement Life Cycle Costs

Category Item Specific examples

Road management expenses

Survey and planning expenses Study expenses, design expenses

Construction expenses Construction expenses, on-site management expenses

Maintenance expenses Maintenance expenses, snow removal expenses Repair and reconstruction expenses

Repair and reconstruction expenses, disposal expenses, on-site management expenses

Related administrative expenses Promotional expenses

Road user expenses

Vehicle operating expenses

Fuel expenses, increases in vehicle wear expenses

Time loss expenses Time loss expenses from construction restrictions and detours

Other expenses Accident expenses, psychological load (ride comfort, road congestion) expenses

Roadside and local community expenses

Environmental expenses

Noise, vibration, and other effects on roadside communities, etc.

Other expenses Psychological load of construction on roadside residents Economic losses to roadside businesses

Source: Design and Construction Guidelines (Japan Road Association, 2006)

1) Considered pavement makeup and direct construction expenses (Japan)

Under N5 traffic conditions (formerly B traffic, design CBR=6, reliability 90%), the approximate direct construction expenses were as follows for straight asphalt, modified asphalt, and concrete pavement. The calculations for direct construction expenses were based on Japanese construction unit prices for 2019. Also, based on the results of the overseas questionnaire, direct pavement construction costs for Cambodia, Uganda and Tanzania are set as shown in Table 5.35.

Table 5.35 Direct Construction Expenses by Pavement Type

Case Pavement type Direct construction cost (yen/m2)

Japan Cambodia Uganda Tanzania

A

Surface: Dense graded asphalt (20), t=5cm Straight asphalt

1,692

3,423

1,849

3,740 3,080

1,522 1,335

2,595 As base: Open graded asphalt (20), t=5cm Straight asphalt

1,731 1,891 1,558 1,260

B

Surface: Dense graded asphalt (20), t=5cm Modified asphalt

2,019

3,750

-

- -

1,450

2,710 As base: Open graded asphalt (20), t=5cm Straight asphalt

1,731 - 1,260

C Concrete pavement: 25cm 8,383 6,118 6,050 - Source: JICA Study Team

2) Maintenance and repair cycle


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Figure 5.17 shows reference material concerning repair timing for asphalt pavement and concrete pavement in Japan. Additionally, Figure 5.18 shows material about the period required for repairing straight asphalt and modified asphalt.

Source: General Study on Pavement Management Levels and Maintenance and Repair Methods (Report from the 40th Ministry of Construction Technical Study Group)

Figure 5.17 Passed Years until Repairs

Source: Monthly Report from the Civil Engineering Research Institute for Cold Region (October 2006)

Figure 5.18 Period until Repairs are needed (years)

Figure 5.17 shows that an average of 14.0 years elapses before repairs to B traffic asphalt pavement are necessary and 21.5 years for concrete pavement. With respect to material for the number of years until repairs for modified asphalt and straight asphalt are necessary, the material for cold regions (Hokkaido) in Figure 5.18 is available. According to these comparisons, modified asphalt is about 1.8 times more durable than straight asphalt. However, because the current study is about generally tropical area where the effects of rutting are greater, the durability will be about 1.3 times greater.

Case Maintenance/Repair (Analysis for 60 years)

A As new construction: Overlay after (surface) 7 years, full repair (surface + As base) after 12 years

B Modified As new construction: Overlay after (surface) 9 years, full repair (surface + As base) after 15 years

C Co new construction: Full repair every 20 years

As a result, LCC of concrete pavement became dominant after 24 years in Cambodia where concrete pavement costs are low, after 43 years in Uganda, and after 55 years in Japan. In

Passed year (As pavement) Passed year (Co pavement)

Average year Average year

No No.

<5yr 20yr<10yr - 15yr5yr - 10yr 15yr - 20yr

<5yr 20yr<10yr - 15yr5yr - 10yr 15yr - 20yr

Class DClass CClass B




yryryr

yryryr

St. AsMod. II

Period until repair (year)

Num

ber

of h

eavy

veh

icle

/day

-lane


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addition, the LCC of modified asphalt became dominant after 54 years in Japan and after 39 years in Tanzania.

Japan Cambodia

Uganda Tanzania


Figure 5.19 Results of LCC Analysis for 4 Countries


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5.9 Structural Analysis Using a Theoretical Design Method (Multilayer Elasticity Theory)

(1) Description of the design method

A theoretical design theory (multilayer elasticity theory) is a method to design the cross-section of a pavement by positing the elasticity of the materials in each layer that makes up a pavement, repeatedly places a 49 kN traffic load, and calculates the stress, distortion, and displacement at arbitrary points on the pavement from elasticity theory.

A model of the pavement structure is created as shown in Figure 5.20. The elasticity coefficients and Poisson ratios of each layer of the pavement are set, and the pavement cross-section is posited after considering arbitrary traffic conditions, weather conditions, etc. If the 49 kN converted wheel load in the design is smaller than the predicted fatigue damage wheel load for the posited pavement cross-section, then it can be determined that there is mechanical stability.

(2) Structural design condition settings

Setting conditions

The following conditions in Table 5.36 need to be set for the structural design.

Table 5.36 Structural Design Condition Setting Items Item Setting conditions to be clarified

Traffic conditions

Fatigue damage wheel load Traffic load

• Classification of single wheel load and multiple wheel load • Singe tire load • Central interval of multiple tires • Tire ground contact pressure and ground contact radius

Foundation conditions

When the subgrade condition is set, set the subgrade thickness to 1 m. • Elastic modulus and Poison’s ratio of the construction subgrade, and

the subgrade (original ground)

Environment conditions

Air temperature or asphalt mixture layer temperature (annual average, monthly average, etc.)

Freezing index (cold areas)

Material condition Elastic modulus and Poison’s ratio of each pavement layer Source: Created by the JICA Study Team based on the Pavement Design Handbook

Fatigue damage wheel load

Fatigue damage refers to the damage on the pavement due to the cracks caused by repeated application of loads. A fatigue damage load is defined as “the number of times a load is applied until the pavement is cracked when a wheel load of 49 kN is applied to the paved road surface repeatedly”. Since the minimum reference values of the fatigue damage wheel load are specified according to the pavement plan traffic volume as shown below, the values are determined according to the cumulative 5t-converted wheel load (ESWL) that is obtained from the actual traffic. When the

49KN

226mm

h1

226mm

320mm

AC

Base

Subbase

Subgrade

Compressive Strain

Tensile Strain

E1,µ1

E2,µ2

E3,µ3

E4, µ4

h2

h3

h4=?

Dual Tyer


Figure 5.20 Pavement Structure Model


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pavement designed period is other than 10 years, the fatigue damage wheel load is calculated by multiplying the ratio of the designed period to 10 years by the value that is indicated below. When the designed period is 20 years, multiply the ratio of 20 years to 10 years, which is 2, by the value indicated in Table 5.37 below.

When the total is calculated based on the cumulative equivalent standard axles (ESAL), the value created by dividing the ESAL value by 2.25 is regarded as the cumulative 5t converted wheel load (ESWL).

Table 5.37 Pavement Damage Load Reference Values

Type Pavement plan traffic volume* (units/day, direction)

Fatigue damage load (times/10 years)

N7 3,000 or more 35,000,000 N6 1,000 ~ 3,000 7,000,000 N5 250 ~ 1,000 1,000,000 N4 100 ~ 250 150,000 N3 40 ~ 100 30,000 N2 15 ~ 40 7,000 N1 Less than 15 1,500

*: Pavement plan traffic volumes refers to the average traffic volume of large vehicles within the pavement designed period.

Source: Pavement Design Handbook

Foundation and material conditions

It is desirable to set the elastic modulus and Poison’s ratio of the materials that are used in each pavement layer by testing. However, if test data is not easily available, the following values can be used.

Table 5.38 Elastic Modulus and Poison’s Ratio of the Material Used for Each Pavement Layer Material used Elastic modulus(MPa) Poison’s ratio Measuring method and notes

Asphalt mixture

600 ~ 12,000 0.25 ~ 0.45

(0.35) *+

⋅ Pavement Test Method Handbook, Separate volume, “3-1-1T Resilient Modulus Test Method of Asphalt Mixtures” etc.

⋅ Considering the pavement temperature and assumed traveling speed.

Pavement concrete

25,000 ~ 35,000 (28,000)

0.15 ~ 0.25 (0.20)

JIS A1149 “Static elastic modulus test methods for concrete”, etc.

Cement stabilization

mixture

1,000 ~ 15,000* May be estimated based on the assumed compression strength.

0.10 ~ 0.30 (0.20)

Pavement Test Method Handbook, Separate volume, “3-1-2T Resilient Modulus Test Method of Base Course Materials and Subsoil” etc.

Granular material

100 ~ 600 (crushed stone for mechanical

stabilization: 300) (Crusher run: 200

May be estimated from other mechanical tests.

0.30 ~ 0.40 (0.35)

Pavement Test Method Handbook, Separate volume, “3-1-2T Resilient Modulus Test Method of Base Course Materials and Subsoil” etc.

Subgrade material

10 × CBR*** 0.4 JIS A1149 “Static elastic modulus test methods for concrete”, etc.

*: Unconfined compression strengths range from 3 MPa to 15 MPa.


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**: ( ): Representative value.

***: May be used when the CBR value is required for the subgrade. However, CBR must be 20% or less (according to Huan; Pavement Analysis and Design). Originally, physically different properties are assessed for the elastic modulus and CBR of a subgrade and many studies are conducted for the conversion. The results and information of the main studies are summarized below.

Yasushi Takeuchi and others: Proposal of simple calculation expressions of subgrade elastic modulus with the consideration to reliability, Japan Society of Civil Engineers Papers E1 (Pavement Engineering) Vol.67, No.3, 2011

Geotechnical Aspects of Pavements Reference Manual: https://www.fhwa.dot.gov/engineering/geotech/pubs/05037/

Source: Created by the JICA Study Team based on the Pavement Design Handbook

Environmental Conditions

Environmental conditions include temperature, rainfall, etc. The temperature (freezing indexes should be considered in the cold regions of Japan) has an effect on the temperature and elasticity coefficient of asphalt mixtures, and it can also cause pavement to deform and affect the durability of structures. Because of this, the temperature of asphalt mixture layers (including base material using bitumen stabilization) must be set appropriately based on the air temperature data. It is desirable to set the temperatures used for design from the actual air temperature and asphalt mixture layer temperature data, but if the temperature of asphalt mixture layers cannot be measured, then the asphalt mixture layer temperature can be estimated from the air temperature data by using the expression below.

Mp: Monthly average pavement temperature (°C)

Ma: Monthly average air temperature (°C)

z: Depth (cm) from the top of the surface from where the temperature is being estimated.

Note that the average temperature of a given layer is the temperature at the h'/3 location from the top of the given layer (thickness = h'). Therefore, the average temperature of a given layer is z which adds h'/3 to the depth of the top of the given layer from the road surface.

(3) Pavement failure conditions

Fatigue cracking of asphalt mixtures is mainly caused by the tensile distortion from the bottom of asphalt layers. Moreover, permanent deformation caused by compression of various pavement layers, including subgrades, is mainly caused by the compression distortion of the top of the subgrade. These values are calculated by using multilayer elasticity theory. The tentatively set failure standards are applied to the calculated distortion according to the cracking rate and permanent deformation amount to calculate the permissible 49 kN wheel load.

Compare the pavement cross-section (permissible 49 kN wheel load/reliability coefficient) and fatigue destruction wheel load, and if (permissible 49 kN wheel load/reliability coefficient) ≥ fatigue destruction wheel load, then there is mechanical stability and the pavement cross-section can be assessed as meeting the design conditions. The tentative destruction standards are shown below.

Tentative destruction standards for subgrades

NfS=βS1x(1.365×10-9 x εz-4.477βs2) (Equation 5.4)

(Equation 5.3)

https://www.fhwa.dot.gov/engineering/geotech/pubs/05037/


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Nfs: Permissible 49 kN wheel load for subgrades

εz: Compression distortion at the top of the subgrade

βs1: 2.134×103

βS2: 0.819

Tentative destruction standards for asphalt mixtures

NfA=βa1x (C) x (6.167 x 10-5 x εt-3.291βa2 x E-0.854βa3) NfA: Permissible 49 kN wheel load for asphalt mixtures C ：C=10M (M=4.84 (VFA/100-0.69))

VFA: Voids filled with asphalt (%)

εt: Tensile distortion at the bottom of the asphalt mixture layer

E: Elasticity coefficient (MPa) of the asphalt mixture βa1＝Ka×βa1’

βa1’：5.229×104

βa2: 1.314

βa3: 3.018

Ka=1/(8.27×10-11+7.87×e-0.11Ha) （Ha<19cm）, Ka=1.0 (Ha≧19cm)

Ha: Thickness (cm) of the asphalt mixture

(4) Comparison of Pavement composition by Theoretical Design Method

In the theoretical design method, the elastic modulus of the asphalt mixture reflects the influence of the “pavement temperature” as the modulus changes according to the temperature.

In the pavement design by the TA method and the AASHTO method, only the cost is evaluated other than the specified minimum value. However, by using the multilayer elastic theory, the life span is to be calculated from the strain, enabling theoretical examination of the optimum pavement thickness. Table 5.39 shows a comparison according to results of multilayer elastic theory calculation of four pavements having the same TA value but different composition, to examine different temperature conditions between Japan and a certain country in South-eastern Asia. From this, the following points are learned.

1) Due to the different temperature conditions between Japan and Southeast Asia, even if the pavement structure is the same, a difference of 1.1 times and 2.1 times arises in the asphalt mixture layer Nfad (allowable wheel load determined according to cracking in the bottom of asphalt layer) and Nfsd (aloowable wheel load determined according to permanent deformation of the subgrade), respectively. In other words, in areas of high temperature, pavement damage (stress cracking) occurs at a faster pace than in Japan. (Comparison of pavement composition A and B).

2) In all the pavement compositions, the target TA value is approximately 24cm, however, the Nfad and Nfsd differ greatly according to the pavement composition. In particular, if a thin asphalt mixture layer is adopted (pavement composition D), the allowable wheel load of the asphalt mixture layer becomes dramatically shorter at the center point between wheels – around 15% of pavement composition B, and 10% of pavement composition C. However, Asphalt layer thickness of 7 cm does not meet the minimum thickness standard.

3) Concerning thickness of the asphalt mixture layer (including asphalt stabilization), more than asphalt mixture layer of 19cm with adoption of asphalt stabilization (9cm), pavement

Correction coefficient for the AI destruction standard based on experience.

Correction coefficient for the AI destruction standard based on experience.

(Equation 5.5)


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composition with an asphalt mixture layer of 15cm has around 38% higher allowable wheel load at the center point between wheels. This is due to the fact that VFA of the asphalt stabilized layer is small (see tentative damage criterion of asphalt mixtures in Equation 5.3). However, the allowable wheel load on the subgrade decreases by 38%.

4) Adopting a thicker asphalt mixture layer contributes to longer service life, however, if it becomes too thick, allowable wheel load of the subgrade will end before allowable wheel load of the asphalt mixture layer; accordingly, it is necessary to adopt pavement composition that also considers cost and balance in terms of maintenance, etc. (overlay, etc.).

Table 5.39 Example of Structural Review using Theoretical Design Method (1)


Also, regarding the effects of improved subgrade and cement stabilized subbase, which is frequently adopted in Africa, the results of comparison based on the theoretical design method using the five pavement compositions shown in Table 5.40 are indicated below.

1) Adopting an asphalt stabilized layer greatly increases allowable wheel load of the asphalt mixture layer, however, its effect in terms of increasing the subgrade’s allowable wheel load is small (comparison between pavement composition A and B).

2) Adopting a cement stabilized subbase also increases allowable wheel load of the asphalt mixture layer, but it increases allowable wheel load of the subgrade even more. Accordingly, the disparity in allowable wheel load with the asphalt mixture layer becomes extremely large, leading to the possibility that repairs will need to be made to the asphalt surface over the long term (comparison between pavement compositions A and C, and D and E).

3) The adoption of improved subgrade (CBR=15%) alone does not lead to increase in allowable wheel load of the asphalt mixture (comparison is made between pavement structures A and D). From this observation, it can be deduced that the allowable wheel load of an asphalt mixture depends on the thickness of the highly elastic materials, significantly more than the strength of the subgrade. With that in mind, however, determination of the pavement structure should account for workability such as compaction of the base course, as well as economic efficiency.

4) Adopting both a cement stabilized subbase and improved subgrade increases allowable wheel

Thickness (cm) TA Thickness (cm) TA Thickness (cm) TA Thickness (cm) TA

Surface Hot mix asphalt 1.00 5 5 5 5 5 5 7 7As interlayer Hot mix asphalt 1.00 0 0 0 0 5 5As base Hot mix asphalt 1.00 5 5 5 5 5 5 0 0

As stabilized 0.80 9 7.2 9 7.2 0 0 0 0Granular 0.35 0 0 0 0 12 4.2 27 9.45Crusher-run 0.25 30 7.5 30 7.5 20 5 30 7.5Cemented 0.25 0 0 0 0 0 0 0 0

49 24.70 49 24.70 47 24.20 64 23.95

Centre of Dual Tyre Beneath a Tyre Centre of Dual Tyre Beneath a Tyre Centre of Dual Tyre Beneath a Tyre Centre of Dual Tyre Beneath a Tyre1.18.E-04 1.13.E-04 1.71.E-04 1.64.E-04 1.69.E-04 1.67.E-04 2.39.E-04 2.66.E-041.78.E-04 1.66.E-04 2.24.E-04 2.07.E-04 2.55.E-04 2.34.E-04 2.61.E-04 2.40.E-0423.9E+06 28.6E+06 21.2E+06 25.2E+06 29.2E+06 30.9E+06 3.0E+06 1.9E+06148.4E+06 194.5E+06 70.0E+06 94.3E+06 43.7E+06 60.2E+06 40.0E+06 54.3E+062.49.E-02 2.48.E-02 2.89.E-02 2.92.E-02 3.06.E-02 3.06.E-02 4.29.E-02 4.42.E-021.77.E-02 1.72.E-02 1.96.E-02 1.90.E-02 2.07.E-02 2.00.E-02 2.25.E-02 2.18.E-02

Nfad 1.13 1.13 1.00 1.00 1.38 1.23 0.14 0.07Nfsd 2.12 2.06 1.00 1.00 0.62 0.64 0.57 0.58Uz (cm)　As layer top 0.86 0.85 1.00 1.00 1.06 1.05 1.49 1.52Uz (cm)　Subgrade top 0.90 0.91 1.00 1.00 1.05 1.05 1.15 1.15

PavementComposition

MaterialsEquivalent conversion

coefficient (TA)

Weather condition (Tokyo) Weather condition (South-eastaern Asia)A：Japan Design #1 B: Japan Design #1 C: Japan Design #2 D: Test Design

Base

Subbase

Total

Pavement Composition

Examination pointTensile Strain εt As undersurface

Compressive Strain εz top of subgradeNfadNfsd

Deflection Uz (cm)　Top of As surfaceDeflection Uz (cm)　Top of subgrade

Unit cost: yen/m2 - 5060 4044

Examination conditions

Existing ground CBR=16%ESWL=16.5×10＾6Required TA=24 (reliability 90%)As elastic modulus E=7500 x 10^0.368(20-T/20) (T=pavement temperature)Source: Temperature distribution and design strain of asphalt mixture layer[6]

As layer VFA=70%As stabilized layer VFA=56%

ReultsJapan Design#1 (Weather condition:

south-eastern ais)=1.0

5831

HMA 15cm

Existing ground CBR 16%

Granular base 12cm

Granular subbase 20cm

HMA 7cm



Granular base 27cm

HMA 10cm


As stabilized base 9cm


HMA 10cm


As stabilized base 9cm



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load of the asphalt mixture layer and subgrade by 1.5 times and 7 times respectively (comparison between pavement composition A and E). Moreover, since it reduces deflection of the subgrade to around 0.6 times, it can be expected to lead to easier workability (comparison between pavement compositions A and E and F). Actually, in Africa, making a part of pavement foundation through adopting cement stabilized subbase and improved subgrade is considered to be a good platform for conducting pavement works for base and surface.

Moreover, common observations that can be drawn from the results of Tables 5.39 and 5.40 are as follows.

1) Since allowable wheel load of asphalt mixture layer and subgrade differs greatly depending on the temperature conditions and materials used in each layer, it is necessary to confirm the balance by implementing checking that reflects temperature and materials in the target country.

2) Allowable wheel load of the asphalt mixture layer is mainly determined by the thickness of the asphalt mixture layer. This is due to the large influence of the cracking propagation correction coefficient (Ka). However, while adopting a thicker asphalt mixture layer leads to a longer service life, it also incurs higher costs; moreover, if it is too thick, allowable wheel load of the subgrade will end before allowable wheel load of the asphalt mixture layer, making it necessary to adopt pavement composition that also considers balance in terms of maintenance, etc. (overlay, etc.).

3) This checking example is verification of the fatigue breakdown, and there is concern that adopting a thick asphalt mixture layer will lead to rutting damage. Concerning this point, it is necessary to conduct ample examination in the road surface design that is separately explained.


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Table 5.40 Example of Structural Review using Theoretical Design Method (2)


Thickness (cm) TA Thickness (cm) TA Thickness (cm) TA

Surface Hot mix asphalt 1.00 5 5 5 5 5 5

As base Hot mix asphalt 1.00 5 5 5 5 5 5

As stabilized 0.80 0 0 10 8 0 0

Granular 0.35 30 10.5 0 30 10.5

Crusher-run 0.25 34 8.5 44 11 0 0

Cemented 0.25 0 0 0 0 34 8.5

74 29.00 64 29.00 74 29.00

2.03.E-04 2.10.E-04 1.55.E-04 1.48.E-04 1.87.E-04 1.95.E-042.44.E-04 2.29.E-04 2.41.E-04 2.27.E-04 1.42.E-04 1.34.E-045.97E+06 5.15E+06 23.79E+06 28.78E+06 8.58E+06 7.17E+06

51.38E+06 64.68E+06 53.99E+06 66.79E+06 445.61E+06 552.06E+064.31.E-02 4.30.E-02 3.70.E-02 3.72.E-02 3.25.E-02 3.29.E-022.58.E-02 2.53.E-02 2.71.E-02 2.66.E-02 2.06.E-02 2.03.E-02

Nfad 1.00 1.00 3.98 5.59 1.44 1.39Nfsd 1.00 1.00 1.05 1.03 8.67 8.53Uz (cm)　As layer top 1.00 1.00 0.86 0.86 0.75 0.77Uz (cm)　Subgrade top 1.00 1.00 1.05 1.05 0.80 0.80

Thickness (cm) TA Thickness (cm) TA Thickness (cm) TA

Surface Hot mix asphalt 1.00 5 5 5 5 5 5As base Hot mix asphalt 1.00 5 5 5 5 0 0

As stabilized 0.80 0 0 0 0 0 0Granular 0.35 25 8.75 25 8.75 35 12.25Crusher-run 0.25 33 8.25 0 0 39 9.75Cemented 0.25 0 0 33 8.25 0 0

68 27.00 68 27.00 79 27.00

2.05.E-04 2.12.E-04 1.84.E-04 1.92.E-04 2.20.E-04 2.69.E-042.33.E-04 2.17.E-04 1.44.E-04 1.35.E-04 1.18.E-04 1.11.E-045.68E+06 4.92E+06 9.18E+06 7.59E+06 2.57E+06 1.09E+06

61.14E+06 79.45E+06 354.03E+06 453.96E+06 734.96E+06 917.46E+063.90.E-02 3.89.E-02 2.87.E-02 2.92.E-02 3.34.E-02 3.74.E-022.21.E-02 2.15.E-02 1.78.E-02 1.74.E-02 1.62.E-02 1.59.E-02

Nfad 0.95 0.95 1.54 1.47 0.43 0.21

Nfsd 1.19 1.23 6.89 7.02 14.31 14.18Uz (cm)　As layer top 0.91 0.91 0.67 0.68 0.77 0.87Uz (cm)　Subgrade top 0.86 0.85 0.69 0.69 0.63 0.63

Nfsd

Base

Subbase

Total

PavementComposition


coefficient (TA)

A: Design #1 B: Design #2 C: Design #3

Beneath a Tyre Centre of Dual Tyre Beneath a Tyre Centre of Dual Tyre

Examination point

Examination point

Deflection Uz (cm)　Top of As surfaceDeflection Uz (cm)　Top of subgrade

Reults(Design#1=1.0)

Tensile Strain εt As undersurfaceCompressive Strain εz top of subgrade

Nfad

Beneath a TyreCentre of Dual Tyre

Base

Subbase

Total

PavementComposition


coefficient (TA)D: Design #4 E: Design #5 F: Design #6

Unit cost: yen/m2 5485 6388 5505

構成

Examination point Centre of Dual Tyre Beneath a Tyre Centre of Dual Tyre Beneath a Tyre

Deflection Uz (cm)　Top of As surface

Centre of Dual Tyre Beneath a Tyre

Tensile Strain εt As undersurfaceCompressive Strain εz top of subgrade

NfadNfsd

Examination conditions

Existing ground CBR=8%Application of capping layer CBR=11% (replacement material for subgrade: CBR=15%, 50cm)ESWL=11.8×10＾6Existing ground: Required TA=29 (reliability 90%)Application of capping layer: Required TA=27 (reliability 90%)As elastic modulus E=7500 x 10^0.368(20-T/20) (T=pavement temperature)Source: Temperature distribution and design strain of asphalt mixture layer[6]As layer VFA=70%As stabilized layer VFA=56%

Deflection Uz (cm)　Top of subgrade

Reults(Design#1=1.0)

Unit cost: yen/m2 6116 6906 6955

HMA 10cm

As stabilized 10cm



HMA 10cm


Granular base 30cm


HMA 10cm


Granular base 30cm

Cemented subbase 34cm

HMA 10cm

Capping layer CBR 15%t=50cm

Granular base 25cm



HMA 5cm


Granular base 35cm



HMA 10cm


Granular base 25cm




Final Report

83

(5) Review of pavement compositions using theoretical design methods

In this study, it is proposed that the pavement structural design be checked using theoretical (mechanical-empirical) design methods as shown in Figure 5.21. Structural design of pavement by the theoretical design method requires results of strain derived from multi-layer elastic analysis, and allowable wheel load of asphalt layer and subgrade. For this reason, in order to carry out this process more efficiently, an Excel calculation sheet was created, as shown in Figure 5.22, in which the damage can be easily checked from the calculation results based on the multi-layer elastic analysis.


Figure 5.21 Flow of Review for Pavement Composition

Manual Input data

Results Calculation sheet for Resilient modulus of Asphalt layer


Figure 5.22 Review of Deterioration of Asphalt Layer and Subgrade by Excel

Necessary program for this process can be obtained from the following.

Pavement design based on catalog design method

Pavement design based on empirical design method

Pavement design based on theoretical design method

Pavement design based on empirical design method

1 Since this file creats a macro in Excel, as first step, enable macros in Excel settings2 Stresses from January to December based on the monthly elastic modulus are analyzed by GAMES.3 Analysis results using GAMES are output with the specified file name [Jan._bre.csv, …, Dec._bre.csv]4 Save this Excel file and output results derived from GAMES in the same folder.5 Input the analysis conditions into yellow cell of the sheet "Input"

- Reliability- Number of wheelload for fatigue, VFA (As layer)- Bottom of As layer (cm) and Layer number- Surface of subgrade layer (cm) and Layer numberNote: Up to 2 positions (X,Y) can be set.

6 Development tab → Macro → Macro name: Execute “Calculate”（Read-in GAMES results into sheets of Feb._bre～Dec._bre of this Excel)* Development tab can be displayed by option setting → ribbon setting

7 Command "recalculation"* Excel files are calculated manually, so you need to recalculate each time.

Procedure

If you input the average air temperature in the “sheet of As Modulus” of this Excel file,The reference value of the monthly elastic modulus of the asphalt layer and the As stabilized layer can be

Design conditions (input sheet)*Input into yellow cells

Reliability 90%Number of wheel load for fatigue×106(N) 11.8

VFA (%) (As layer) 70%Bottom of As layer (cm) 10.0

Layer number 1Surface of subgrade (cm) 74.0

Layer number 4

Case-1　（ｃｍ） X Y Z

Strain (bottom of As layer) 0.0 0.0 10.0Strain (subgrade surface) 0.0 0.0 74.0

Defrection (bottom of As layer) 0.0 0.0 0.0Defrection (subgrade surface) 0.0 0.0 74.0

Case-2　（ｃｍ） X Y Z

Strain (bottom of As layer) 16.0 0.0 10.0Strain (subgrade surface) 16.0 0.0 74.0

Defrection (bottom of As layer) 16.0 0.0 0.0Defrection (subgrade surface) 16.0 0.0 74.0

1.87.E-04 1.95.E-041.41.E-04 1.33.E-048.58E+06 7.17E+06

378.30E+06 468.36E+06

As layer OUT OUTReliability 90% Subgrade OK OK

3.25.E-02 3.29.E-022.05.E-02 2.02.E-02

Defrection Uz (cm)　 As surfaceDefrection Uz (cm)　 Subgrade surface

Case-1 Case-2

NfadNfsd

N 11.8E+06

Results of Mechanistic Analysis

Strain (Bottom of As layer)Strain (Subgrade surface)

Evaluation

As layer thickness (cm) 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0

h/3 (cm) 1.7 2.0 2.3 2.7 3.0 3.3 3.7 4.0 4.3 4.7 5.0 5.3 5.7 6.0 6.3 6.7 7.01 27.7 1 36.7 36.5 36.4 36.2 36.1 36.0 35.9 35.7 35.6 35.5 35.4 35.3 35.2 35.2 35.1 35.0 34.92 27.9 2 36.9 36.8 36.6 36.5 36.3 36.2 36.1 36.0 35.9 35.8 35.7 35.6 35.5 35.4 35.3 35.2 35.13 27.5 3 36.4 36.3 36.1 36.0 35.9 35.7 35.6 35.5 35.4 35.3 35.2 35.1 35.0 34.9 34.8 34.8 34.74 26.6 4 35.3 35.2 35.1 34.9 34.8 34.7 34.6 34.4 34.3 34.2 34.1 34.1 34.0 33.9 33.8 33.7 33.65 25.6 5 34.1 34.0 33.9 33.7 33.6 33.5 33.4 33.3 33.2 33.1 33.0 32.9 32.8 32.7 32.6 32.6 32.56 24.3 6 32.6 32.4 32.3 32.2 32.0 31.9 31.8 31.7 31.6 31.5 31.5 31.4 31.3 31.2 31.1 31.1 31.07 23.6 7 31.7 31.6 31.4 31.3 31.2 31.1 31.0 30.9 30.8 30.7 30.6 30.6 30.5 30.4 30.3 30.3 30.28 23.8 8 31.9 31.8 31.7 31.6 31.5 31.3 31.2 31.1 31.1 31.0 30.9 30.8 30.7 30.6 30.6 30.5 30.49 24.4 9 32.7 32.5 32.4 32.3 32.2 32.1 32.0 31.9 31.8 31.7 31.6 31.5 31.4 31.3 31.3 31.2 31.110 25.3 10 33.8 33.7 33.6 33.4 33.3 33.2 33.1 33.0 32.9 32.8 32.7 32.6 32.5 32.4 32.4 32.3 32.211 26.4 11 35.1 35.0 34.8 34.7 34.6 34.4 34.3 34.2 34.1 34.0 33.9 33.8 33.7 33.7 33.6 33.5 33.412 27.2 12 36.1 36.0 35.8 35.7 35.6 35.4 35.3 35.2 35.1 35.0 34.9 34.8 34.7 34.6 34.6 34.5 34.4

Month As layer thickness (cm) 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0

1 3699.1 3723.6 3747.0 3769.4 3790.7 3811.1 3830.6 3849.2 3867.1 3884.3 3900.8 3916.6 3931.9 3946.5 3960.7 3974.3 3987.42 3661.2 3685.7 3709.0 3731.3 3752.6 3772.9 3792.3 3811.0 3828.8 3845.9 3862.4 3878.2 3893.4 3908.0 3922.1 3935.7 3948.83 3737.3 3762.0 3785.4 3807.8 3829.2 3849.6 3869.2 3887.9 3905.8 3923.0 3939.6 3955.5 3970.7 3985.4 3999.6 4013.2 4026.44 3914.5 3939.4 3963.2 3985.8 4007.4 4028.1 4047.8 4066.7 4084.9 4102.2 4118.9 4135.0 4150.4 4165.2 4179.5 4193.3 4206.55 4121.3 4146.5 4170.5 4193.3 4215.2 4236.0 4256.0 4275.1 4293.4 4310.9 4327.8 4344.0 4359.5 4374.5 4388.9 4402.8 4416.26 4406.5 4432.0 4456.2 4479.4 4501.5 4522.5 4542.7 4562.0 4580.5 4598.2 4615.2 4631.6 4647.3 4662.4 4676.9 4690.9 4704.47 4568.1 4593.7 4618.1 4641.4 4663.6 4684.8 4705.0 4724.4 4743.0 4760.8 4777.8 4794.2 4810.0 4825.2 4839.8 4853.8 4867.48 4521.3 4546.9 4571.3 4594.5 4616.7 4637.8 4658.1 4677.4 4696.0 4713.8 4730.8 4747.2 4762.9 4778.1 4792.7 4806.7 4820.39 4383.8 4409.3 4433.6 4456.7 4478.8 4499.8 4520.0 4539.3 4557.8 4575.5 4592.5 4608.8 4624.5 4639.6 4654.1 4668.1 4681.610 4174.6 4199.9 4224.0 4246.9 4268.8 4289.7 4309.7 4328.8 4347.2 4364.8 4381.6 4397.9 4413.5 4428.5 4442.9 4456.8 4470.211 3955.0 3980.0 4003.8 4026.5 4048.1 4068.8 4088.6 4107.6 4125.7 4143.2 4159.9 4175.9 4191.4 4206.2 4220.6 4234.4 4247.712 3785.7 3810.5 3834.0 3856.5 3877.9 3898.4 3918.0 3936.8 3954.8 3972.0 3988.6 4004.5 4019.8 4034.6 4048.8 4062.4 4075.6

Month As layer thickness (cm) 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.01 2667.7 2681.4 2694.5 2707.0 2719.0 2730.6 2741.6 2752.3 2762.6 2772.5 2782.0 2791.22 2641.0 2654.6 2667.7 2680.2 2692.2 2703.7 2714.7 2725.4 2735.6 2745.5 2755.0 2764.13 2694.7 2708.4 2721.5 2734.1 2746.1 2757.7 2768.8 2779.5 2789.8 2799.7 2809.2 2818.54 2819.6 2833.5 2846.7 2859.4 2871.6 2883.2 2894.5 2905.3 2915.6 2925.6 2935.3 2944.65 2965.2 2979.2 2992.6 3005.4 3017.7 3029.5 3040.8 3051.7 3062.2 3072.2 3082.0 3091.36 3165.8 3179.9 3193.4 3206.4 3218.8 3230.7 3242.1 3253.1 3263.7 3273.9 3283.7 3293.17 3279.3 3293.5 3307.1 3320.1 3332.5 3344.5 3356.0 3367.0 3377.6 3387.8 3397.7 3407.28 3246.5 3260.6 3274.2 3287.2 3299.6 3311.6 3323.0 3334.1 3344.7 3354.9 3364.7 3374.29 3149.9 3164.0 3177.5 3190.4 3202.8 3214.7 3226.2 3237.1 3247.7 3257.9 3267.7 3277.110 3002.8 3016.8 3030.2 3043.0 3055.3 3067.2 3078.5 3089.4 3099.9 3110.0 3119.8 3129.211 2848.2 2862.0 2875.3 2888.0 2900.2 2911.9 2923.2 2934.0 2944.4 2954.4 2964.0 2973.412 2728.9 2742.6 2755.7 2768.3 2780.4 2792.0 2803.2 2813.9 2824.2 2834.1 2843.7 2852.9

Stabilized As layer Modulus: E2 (Mpa)E2=E×0.7

Pavement tenperature (°C) Mp

As layer Modulus: E (MPa)

As Modulus (Mpa)

Month Mean Air Temperature(°C)： Ma Month


Final Report

84

Download site of the multi-layer elastic analysis program "GAMES" The Committee on Pavement Engineering, JSCE:

http://www.jsce.or.jp/committee/pavement/downloads/

Excel file (macro) for judgment of deterioration of asphalt layer and subgrade by theoretical design method (Both Japanese and English version are prepared.)

Eight-Japan Engineering Consultants Inc.: [email protected] (Mail title: JP_Mechanistic-Empirical Design Method

mailto:[email protected]


Final Report

85

6. Results of Field Surveys (Thailand and Tanzania)

6.1 Overseas Questionnaire Surveys

(1) Objectives of the questionnaire surveys

The result of SHRP in the USA triggered the current acceleration of transition of asphalt standards from penetration to PG (Performance Grade) and transition of methods of designing mixes from the Marshall stability test to the utilization of a gyratory compactor. Regarding the securement of rutting resistance, since modifying materials are difficult to secure, some countries seem to resort to alternative measures such as devising aggregate engagement while using straight asphalt. Based on these facts, the following questionnaire survey was conducted.

(2) Contents of the questionnaire survey

Methods of the mixing tests that are currently used as the mainstream (Marshall stability test and Gyratory Compactor, etc.)

Examination status of the gyratory compactor by Superpave, etc., application directivity, and application track record

Retention status, utilization status, and related engineers in the gyratory compactor related facilities

Examination status and application directivity of binder standard application by the performance grade

Binder acquisition track record in the performance grade (local acquisition, importation, and distributor)

Asphalt binder and modifying material acquisition status (local acquisition, importation, etc.) Rutting resistance performance evaluation method for asphalt mixtures (evaluation by HWT

tests or WT tests) Holding a HWT or WT tester in the related facility and establishment of related standards Rutting resistance measures (use of modifying materials, concrete pavement, use of low-

penetration binder, elaboration of aggregate engagement, etc.) Track record of application of concrete pavement (extension) and future policy Standard unit prices of concrete pavement and asphalt pavement (m2)

(3) Result of the questionnaire survey

The following tables show the summary of the results of the main answers to the questionnaires.

Table 6.1 Countries that Participated in the Questionnaire Survey Asia (4 countries) Thailand, Vietnam, Myanmar, and Cambodia

Africa (6 countries) Kenya, Uganda, Ghana, Ethiopia, Tanzania, Rwanda

Table 6.2 Mixing Test Methods Currently Applied

Marshall Mix Design Thailand, Vietnam, Myanmar, Cambodia, Kenya, Uganda, Ghana, Ethiopia, Tanzania (rural road), Rwanda

SUPERPAVE Tanzania (main road)

Table 6.3 SUPERPAVE Application Track Records SUPERPAVE application track records available Uganda, Ghana, and Tanzania

Currently examining introduction of SUPERPAVE Thailand, Myanmar, Uganda, and Ethiopia

Source: JICA study team


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86

6.2 Conducting Field Surveys

(1) Selection of field survey target countries

Initially, three Asian countries and one African country are targeted for the field survey. However, since the result of the questionnaire survey conducted overseas revealed that Thailand and Tanzania implement rutting resistance measures, Thailand is determined to be the target country for the Asian region and Tanzania for the African region.

Table 6.4 Countries Visited for the Field Surveys Region Country Reason for selection

Africa Tanzania

The result of the questionnaire survey indicates that Tanzania is most advanced in the effort of addressing the mix design using Superpave.

The condition of New Bagamoyo Term 1 (gratis) is unsatisfactory. The condition of the Tazara intersection, which is the target of this comparison, is satisfactory.

There is a road (Morogoro road: BRT route) that was constructed under the Superpave mix design.

A consultant (ISEC) and construction contractor (NIPPO) for New Bagamoyo Term 2 are available.

Sumitomo Mitsui Construction that constructed the Tazara intersection has its own representation in Tanzania.

Asia Thailand

Thailand is extremely cooperative regarding the implementation of the rutting resistance measures and responding to the overseas questionnaire survey and wishes to share the result of the questionnaire survey.

The straight asphalt section and the section that uses modifying materials can be compared in the improvement (gratis) of Eastern outer ring road (National Route 9).

There exists information on the occurrence of rutting in the repaired section of the Eastern outer ring road (National Route 9) (gratis) and its verification is possible.

There is an EJEC office in Bangkok, enabling effective management. Source: JICA study team

(2) Objective of the field surveys

The objective of the field survey is to obtain the information necessary for revising the Handbook for the Asian and African regions and the following surveys are conducted.

Questionnaire survey and information collection relating to rutting resistance measures towards the related organizations

Implementation of field surveys (including sample collections such as core extraction and analysis)

(3) Major questionnaire surveys

[Tanzania]

TANROADS Dar-es-Salaam Regional Office: Eng. Julius (Regional Manager) Contents of the discussion: Explanation of the contents of the survey and request for a core

extraction test

C-Labs (private pavement test laboratory): Eng. Jotham Ntensibe (Director) Contents of the discussion: New mix design manual for asphalt, Effects of Superpave,

Pavement of the New Mogaboyo road and Tazara intersection

Oriental Consultants Global (Tazara intersection construction supervision): Mr. Nishida


Final Report

87

(Pavement spot supervision) Contents of discussion: Construction structure and quality control system, Measures taken

to secure rutting resistance

New Bagamoyo II road construction: ISEC and NIPPO Contents of discussion: Construction structure and quality control system, Construction

safety control, Securement of rutting resistance, mix design, etc., Inspection at the site and asphalt plant

TANROADS CML: Eng. Jojn T. N. Malisa (Senior Engineer, Pavement) Contents of discussion: New mix design manual for asphalt, Revision of the pavement

design standard, Evaluation of asphalt pavement

Construction of Gerezani bridge: ISEC and Sumitomo Mitsui Construction Contents of discussion: Construction structure and quality control system, Construction

safety control, Concrete quality control, On-site inspection

[Thailand]

DOH: Dr. Piya (Deputy Director), Dr. Jiraroj (Director), Mr.Surachai (Civil Engineer), Ms.Suladda (Civil Engineer), Mr.Pairat (Public Works Technician) Contents of discussion: Explanation of the contents of the survey, application for the

permission for a core extraction test, and sample analysis request

Route 9 maintenance management office: Mr. Pairat (Public Works Technician) Contents of discussion: Current condition of Route 9 maintenance management

Thailand NIPPO and cooperation company (SECO): Mr. Nakagawa, Manager Contents of discussion: Explanation of the contents of the survey and the pavement quality

and issues in Thailand

Japan Highway Public Corporation: Mr. Kawamura, Manager Contents of discussion: Explanation of the contents of the survey, the pavement quality

and issues in Thailand, etc.

6.3 On-site Core Extraction Test

(1) Purpose of core sampling

Purpose

In grant aid road projects implemented in Tanzania and Thai, pavement damages such as flow rutting came into existence. In order to confirm the cause of the pavement damage, a core sampling was performed, and the properties of the asphalt mixture were analyzed in a laboratory test.

Test contents

The core samplings were taken to laboratory and 5 selected to determine the following properties in Table 6.5.


Final Report

88

Table 6.5 Test Items

Test items Test methods Required results

Measurement - Asphalt layer thickness Bulk density AASHTO T116 Density, air voids Marshall stability AASHTO T245 Stability, flow value Maximum density AASHTO T209 Maximum density Bitumen extraction AASHTO T164A Asphalt content Gradation AASHTO T30 Gradation


(2) Core sampling in Tanzania

Selection of core sampling location

The scope of work involved coring 5 locations detailed in Table 6.6.

Table 6.6 Core Sampling Positions

Route Position Conditions Remarks

New Bagamoyo Road

Shule A position that is flat but close to the intersection. Rutting has occurred and the condition is not fair. Grant aid

Goigi A position is flat and fair condition.

Tazara Jct. - A position is a side road of a flyover. A number of heavy vehicles is high, but in fair condition.

Grant aid

Morogoro Road Bucha

A position is the sag of the gradient section. A number of heavy vehicles is very high, and the deep rutting is occurred. The superpave was applied for the asphalt mix design.

Government (BRT project)

Shekilango A position is flat, and a number of heavy vehicles is low. A pavement condition is fair.


Photo6.1 New Bagamoyo (Shule) Photo6.2 New Bagamoyo (Goigi)


Final Report

89

Photo6.3 Tazara Jct. Photo6.4 Morogoro Road (Bucha)

Photo6.5 Morogoro Road (Shekilango) Photo6.6 Core Sampling（New Bagamoyo）

Photo6.7 Core Sampling （Morogoro Bucha）

Photo6.8 Core Samples （Morogoro Bucha）


Test results

View and thickness

The photographs below show the condition of the core in fair and damaged section. It can be seen that the height is almost constant at the place where the condition is faire, and the level of the road surface is kept constant. On the other hand, it can be seen that the core of the tire running part is compacted and the height is non-uniform at a portion where the condition is poor.


Final Report

90

Fair position

Photo6.9 Tazara Jct.New Photo6.10 Morogoro Road (Shekilango)

Photo6.11 New Bagamoyo (Goigi).

Damaged position

Photo 6.12 Morogoro Road (Bucha) Photo 6.13 Bagamoyo (Shule) Source: JICA study team

Analysis of AC14（Surface）

Table 6.7 shows a comparison of projects using AC14 for the surface layer. The air void of New Bagamoyo Road (Shule), which is in poor condition, is undervalue of 2.2%, normally, the porosity of a dense graded asphalt layer is about 4% during construction, and gradually decreases due to repeated loading. However, at present, it is considered that flow rutting due to consolidation is likely to occur. In addition, the asphalt content of New Bagamoyo Road was as low as less than 4.0% (in Japan, about 5.0 to 5.5% for ordinary fine graded asphalt). Low asphalt content has an advantage to the rutting resistance, but the abrasion resistance and workability are inferior. Regarding the flow value and the stability, both value were satisfied the standard at samples.


Final Report

91

Table 6.7 Comparison of AC14 (Surface)


Regarding the gradations, a part of fine aggregate is out of the standard at all samples. The New Bagamoyo Road has a composition in which the ratio of fine particles and coarse aggregate is high and the intermediate gradation is low.


Figure 6.1 Gradations（AC14）

Analysis of AC20（As base）

Table 6.8 shows a comparison of projects using AC20 as the asphalt base layer. The air void of New Bagamoyo Road (Shule) in damage section is 1.7%, which is undervalue compare to the normal condition. The asphalt content of the New Bagamoyo Road was larger than the surface course. The flow value and the stability were satisfied the standard at all points.

Sieve sizes , mm AC14 (Lower Limit %) AC14 (Upper Limit %) TAZARA NB Shule (bad) NB Goiga (good)

28 100 100 100.0 100 10020 100 100 100.0 100 10014 85 100 95.4 99.8 99.710 72 94 84.7 85.1 81.15 52 72 67.7 54.5 56

2.36 37 55 45.0 35.1 36.31.18 26 41 35.2 28.1 29.60.6 16 28 29.6 24.6 26.20.3 12 20 23.0 21 21.60.15 8 15 15.6 16.1 16.40.075 4 10 10.6 12 13.1

As content (%) - - 4.4 3.7 3.9Air void (%) 6 3 5.3 2.2 3.7

Flow value (mm) 4 2 2.5 2.0 2.0Stability (kN) 4.5 - 20.0 18.0 16.0Penetration 40/50 - -

Tolerance Sampling Test

60/70, 80/100

0

10

20

30

40

50

60

70

80

90

100

0.05 0.5 5 50

TAZARA

NB Shule (bad)

NB Goiga (good)

%

mm


Final Report

92

Table 6.8 Comparison of AC20 (As Base)


Regarding the gradations, the fine particles are out of the standard in all samples. The gradation of the Tazara intersection is almost close to the upper limit. The New Bagamoyo Road and Morogoro Road have a high proportion of fines and coarse aggregate, and have a small intermediate gradation.


Figure 6.2 Gradations（As Base: AC20）


Table 6.9 shows a comparison of Morogoro roads using AC20 for the surface layer. Superpave is used in the asphalt mix design of Morogoro Road.

Bucha, which is in damaged section, has air void of 2.5%, which is low, and it is considered that flow rutting due to consolidation is likely to occur. In addition, the asphalt content is high compared to the past projects, from this result, rutting resistance is inferior.

Sieve sizes , mm AC20 (Lower Limit %) AC20 (Upper Limit %) Tazara NB Shule (bad) NB Goiga (good) MorogoroShekilango

28 100 100 100.0 100 100 10020 80 100 100.0 98.5 98.6 10014 60 80 84.6 76 77.9 98.810 50 70 74.0 54.3 57 79.25 36 56 57.3 42.5 48 55.4

2.36 28 44 42.1 31 38 35.51.18 20 34 32.8 26.2 30.9 27.80.6 15 27 27.4 23.2 27.2 23.60.3 10 20 21.8 19.3 22.3 19.40.15 5 13 15.2 14.5 14.4 13.90.075 2 6 10.1 10.4 10.3 11.2

As content (%) - - 4.2 4.3 4.2 3.9Air void (%) 6 3 6.6 1.7 3.3 6.8

Flow value (mm) 4 2 2.4 2.0 2.2 2.4Stability (kN) 4.5 - 16.0 13.0 16.0 15.0Penetration 40/5060/70, 40/50

SamplingTolerance

0

10

20

30

40

50

60

70

80

90

100

0.05 0.5 5 50

Tazara

NB Shule (bad)

NB Goiga (good)

Morogoro Shekilango

mm

%


Final Report

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Regarding the gradations, almost the same results are shown, and the fine particle component is out of the upper limit, and the ratio of the fine particle component and the coarse aggregate is high.


Figure 6.3 Gradations（Asphalt Surface: AC20）

Sieve sizes , mm AC20 (Lower Limit %) AC20 (Upper Limit %) Morogoro Bucha MorogoroShekilango

28 100 100 100 10020 80 100 100 10014 60 80 96.3 89.410 50 70 75.3 72.55 36 56 54.8 48.7

2.36 28 44 37.7 34.41.18 20 34 29.8 27.30.6 15 27 25.5 23.20.3 10 20 21.3 19.20.15 5 13 16.6 13.80.075 2 6 11.8 12.1

As content (%) - - 5.2 4.2Air void (%) 6 3 2.5 4.7

Flow value (mm) 4 2 2.0 2.6Stability (kN) 4.5 - 15.0 19.0Penetration - -60/70, 40/50

MorogoroTolerance

0

10

20

30

40

50

60

70

80

90

100

0.05 0.5 5 50

Morogoro Bucha

Morogoro Shekilango

mm

%


Final Report

94

(3) Core sampling in Thai

Selection of core sampling location

The scope of work involved coring 3 locations detailed in Table 6.10.

Table 6.10 Core Sampling Positions

Route Conditions Remarks

Route no.9

Km19+639: Modified asphalt section. Rutting has occurred and the condition is not fair (Sample A)

Grant aid Km19+600: Straight As section At the same point, both fair section and a damaged section are confirmed. Rutting is identified in the fourth lane in the centre. （Fair section: Sample B、Damaged section: Sample C）


Photo6.14 Modified Part（Rutting） Photo6.15 Modified Part (Damage)

Photo6.16 Straight Asphalt Damaged in the Most Central Lane

Photo6.17 Core Sampling (Damaged Position)

Photo6.18 Core Sampling (Fair Position)



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Test results


Table 6.11 shows a comparison of surface asphalt. There was no change in the pavement thickness, and the air void was about 4%, and no results indicating the rutting were obtained. The flow value is low compare to accepted trial mix design at the place of the rutting section. In addition, the asphalt contents of all samples were lower than accepted mix design.



Regarding the gradations, in the modified asphalt section where the condition is not fair, aggregates size more than 5 mm fall below the lower limit of the standard. In other samples, the aggregate size of 12 mm or more is below the standard. However, this is not considered to have a significant effect on the flow resistance.


Figure 6.4 Gradations（AC14）

Analysis of As base

Sieve sizes , mm Lower Limit % Upper Limit % Traial Modefied StAs (good) StAs (bad)

37.5 100 100 100 100.00 100.00 100.0025 100 100 100 99.23 99.43 99.0719 100 100 99.6 89.53 92.07 92.83

12.5 78 88 82.8 72.80 78.70 78.209.5 69 79 73.8 61.63 70.33 68.774.75 46 56 51.5 43.47 51.53 49.202.36 28 38 33.5 30.00 35.97 34.071.18 17 25 21.4 19.87 23.47 22.230.6 10 18 14 13.47 16.37 15.600.3 5 13 9.4 9.37 11.03 10.530.15 3 9 6.4 6.97 8.03 7.670.075 3 7 4.8 5.47 6.87 6.60

As content (%) 4.77 4.83 4.87 4.47 4.49 4.65Air void (%) 3 5 4.07 3.93 3.53

Flow value (mm) 11 13 11 9.00 12.00 9.67Stability (kN) 2370 2388 3203 3173 2847Thickness 50 52.0 49.7 50.3

0

10

20

30

40

50

60

70

80

90

100

0.05 0.5 5 50

Modefied

Traial

StAs (good)

StAs (bad)

%

mm


Final Report

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Table 6.12 shows a comparison of the base asphalt. In the asphalt base layer where the modified asphalt was used, the air void was excessively low at 0.7%, and the flow value was also low. At the sections where straight asphalt was used, the stability was lower than the trial mix design at both samples. In addition, the asphalt content of all samples is lower than trial mix design.

Table 6.12 Comparison of As Base


Regarding the gradations, it fell within the standard value at all samples and showed almost the same proportion as the gradation of the accepted trial mix design.


Figure 6.5 Gradations（Asphalt Base）

Analysis of asphalt stabilized layer

Table 6.13 shows comparison of asphalt stabilized base. In the asphalt stabilized base at the section where the modified asphalt is used, the air void and flow value are excessively low. In addition, the asphalt content of all samples is lower than accepted trial mix design. As a characteristic of the test


37.5 100 100 100 100.00 100.00 100.0025 100 100 100 99.33 99.43 99.2319 90 100 95.5 93.30 95.07 91.73

12.5 74 84 79.5 79.30 78.07 75.939.5 66 76 71.1 70.63 69.70 67.504.75 46 56 51 50.67 50.23 47.202.36 29 39 34.1 35.20 34.93 33.031.18 18 26 22.5 22.70 22.83 21.700.6 10 18 14.4 15.10 16.03 15.200.3 5 13 9.2 10.40 10.77 10.300.15 3 9 6.5 7.47 7.73 6.770.075 3 7 4.7 5.67 6.60 5.73


Flow value (mm) 10 12 12 4.67 10.00 10.33Stability (kN) 2400 2936 1631 1453Thickness 50 54.5 48.5 51.1

0

10

20

30

40

50

60

70

80

90

100

0.05 0.5 5 50

Modefied

StAs (good)

StAs (bad)

Traial

%

mm


Final Report

97

results of this asphalt stabilized base, the thickness is insufficient by about 20 mm at all samples. However, this is unlikely to be due to the compaction of the stabilized layer.

Table 6.13 Comparison of As Stabilization


Regarding the gradations, the coarse aggregate is out of the upper limit of the standard upper limit at the section of the straight asphalt. The gradation proportion of the modified asphalt section shows almost the same proportion as the accepted trial mix design.


Figure 6.6 Gradations（Asphalt Stabilized Base）

Analysis method

DOH Laboratory gave the following explanation on the analysis method.

・ 2 samples of 5 samples of each sampling position were used for the Maximum Density test. 3 samples were used for the other tests.

・ For the Maximum Density test, it is necessary to remove incomplete crushed stone that was cut during core sampling. Since one core is not enough for analysis, 2 samples were


37.5 100 100 100 100.00 100.00 100.0025 100 100 100 99.43 99.37 99.3719 87 97 92.4 93.13 92.43 92.43

12.5 63 73 68.5 70.03 76.80 74.309.5 54 64 59.4 60.93 67.60 65.104.75 40 50 44.9 43.87 48.47 45.602.36 26 36 31.3 31.17 33.80 32.201.18 17 25 20.7 20.73 22.17 21.370.6 9 17 13.2 14.00 15.53 15.130.3 5 13 8.6 9.80 10.53 10.330.15 3 9 6 7.17 7.67 7.600.075 2 6 4.4 5.43 6.43 6.43


Flow value (mm) 9 11 10 3.67 10.33 8.00Stability (kN) 2330 3974 4077 3721Thickness 100 83.9 82.0 86.0

0

10

20

30

40

50

60

70

80

90

100

0.05 0.5 5 50

Traial

Modefied

StAs (good)

StAs (bad)

%

mm


Final Report

98

used to determine the Maximum Density. ・ Therefore, the maximum densities of the two samples were regarded as the remaining

three maximum densities. Calculation of air void (%) = (1-Density/Maximum Density）* 100


Final Report

99

7. Domestic Test Results

7.1 Purpose and Overview

(1) Purpose of the tests

In view of local conditions in developing countries, the objective is to find a mix design method for maximizing the flow resistance of straight asphalt while considering durability.

These test results will be used to determine whether modified asphalt should be used during the cooperation preparation and survey phase.

(2) Test overview

A confirmation experiment was conducted for the mixture design in the existing handbook in order to consider flow resistance. However, the type of aggregate used was limited to one kind. Although it was verified that the relations between quantity of asphalt and air void had a high effect on flow resistance, it was also believed that it was dependent on the quality of the source material (aggregate). Therefore, in this work, the tests (preliminary tests) were conducted with a focus on the shape of the coarse aggregate particles, the types of find aggregate (natural sand, artificial sand), and differences in filler (limestone powder, cement, recovered dust). Additionally, tests were conducted with different quantities of asphalt, different gradation, and different types of asphalt to confirm the durability and flow resistance (verification tests).

This work is a two-part verification test: The preliminary tests are conducted to determine the mixture used in the verifications test, and the aggregate proportion determined by the preliminary tests are the basis for the verification tests that use different conditions.

7.2 Materials Used

(1) Materials used

Coarse aggregate

In order to confirm the character of the mixtures due to different shapes, there were three types of coarse aggregate used: Coarse aggregate that underwent primary crushing (graded cut crushed stone; not for sale), tertiary crushing (standard product), and quaternary crushing (special order product for water-draining mixtures).

Fine aggregate

In order to confirm the character of the mixtures due to different shapes, there were three types of fine aggregate used: Natural sand (river sand), crushed sand, mixed sand (natural sand: crushed sand = 50:50).

Filler

In order to confirm the character of the mixtures due to different types, three types of fillers were used: Stone dust, cement, and recovered dust.


Final Report

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(2) Test items

Table 7.1 shows the test items for each material.

Table 7.1 Test Items for Materials Used

Source: JICA Survey Team

(3) Test results

Tables 7.2, 7.3, and 7.4 show the materials criteria test results for aggregate and filler, and the characteristics of the asphalt to be used in the preliminary tests.

Table 7.2 Aggregate Used


First order Third order First order Third order Forth order First order Third order Natural Crushed Mixed Stone powder Recovery Cement Mixed

Futaba Futaba Futaba Futaba Futaba Futaba Futaba Kanematsu Futaba － Hishikou Obayashi Road Taiheiyou －

Tochugi Tochugi Tochugi Tochugi Tochugi Tochugi Tochugi Sakuma dam Tochigi － Saitama Kuki Plant Gunma －

Tight sands Tight sands Tight sands Tight sands Tight sands Tight sands Tight sands Natural sand Tight sands －calcium

carbonate Tight sand PortlandCement －

31.5 100.0

26.5 99.5 100.0

19.0 79.0 91.8 100.0 100.0 100.0

13.2 24.3 14.9 99.9 92.1 95.2

9.5 5.8 1.0 75.8 51.5 51.9 100.0 100.0 100.0

4.75 3.9 15.3 1.5 1.0 99.9 97.7 98.2 100.0

2.36 4.5 0.9 0.6 20.8 13.0 92.4 90.0

0.600 3.0 4.9 1.8 62.9 38.8 100.0 100.0 100.0

0.300 23.7 22.8 100.0 99.8 100.0

0.150 4.9 11.0 99.2 95.4 100.0

0.075 1.5 4.0 87.5 77.4 100.0Saturatedsurface-drycondition[g/cm3]

2.678 2.648 2.672 2.653 2.670 2.657 2.653 2.592 2.594 －－－

Apparentdensity[g/cm3]

2.729 2.680 2.733 2.692 2.699 2.723 2.694 2.658 2.687 2.710 2.581 3.160

Bulk density[g/cm3]

2.648 2.629 2.637 2.630 2.653 2.619 2.628 2.552 2.539 －－－

1.11 0.71 1.33 0.88 0.64 1.47 0.93 1.55 2.17 －－－－－

－－ 24.6 8.4 7.9 －－－－－－－－－

6.2 1.2 3.9 3.3 0.2 －－－－－－－－－

－－ 23 9 7 －－－－－－－－－

－－－－－－－ 20.6 23.9 20.9 －－－－

－－－－－－－－－－－ N.P. － N.P.

Density

Water Absorption[%]

Abrasion[%]

Product company

Production area

Materials

Testitems

Passingpercentage

(%)

CAA[%]

Crushing Value[%]

FAA[second]

Plastic Index [PI]

ClassClass 5 Class 6 Class 7 Sands Filler


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Table 7.3 Asphalt Used (Straight Asphalt 40/60)


CriteriaElongation [cm] 10 <Fire point　COC [℃] 260 <Kinematic viscosity(120℃[mm2/s]Kinematic viscosity(150℃[mm2/s]Kinematic viscosity(180℃[mm2/s]Softening Point [℃] 47.0 - 55.0Penetration (25℃) [1/10㎜] 40 - 60Penetration ratio after eva[%] 110 >Toluene solubles [mass%] 99.0 <Density (15℃) [g/cm3] 1.000 <Thin-film oven testmass chage rate [%] 0.6 >

Thin-film oven testpenetration residual rate [%] 58 <

RemarksPavement

constructionmanual (H18)

22171.1

70.4

Testitems

ProductManufacturer

99.991.040

(+)0.10

Straight Asphalt 40/60JXTG Energy

49.551102

100(+)3581030


Final Report

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Table 7.4 Asphalt Used (Straight Asphalt 60/80, 80/100, Modified Type II)


CriteriaElongation [cm] 100 <Fire point　COC [℃] 260 <Kinematic viscosity(120℃[mm2/s]Kinematic viscosity(150℃[mm2/s]Kinematic viscosity(180℃[mm2/s]Softening Point [℃] 44.0 - 52.0Penetration (25℃) [1/10㎜] 60 - 80Penetration ratio after eva[%] 110 <Toluene solubles [mass%] 99.0 <Density (15℃) [g/cm3] 1.000 <Thin-film oven testmass chage rate [%] 0.6 >


RemarksPavement


CriteriaElongation [cm] 100 <Fire point　COC [℃] 260 <Kinematic viscosity(120℃[mm2/s]Kinematic viscosity(150℃[mm2/s]Kinematic viscosity(180℃[mm2/s]Softening Point [℃] 42.0 - 50.0Penetration (25℃) [1/10㎜] 80 - 100Penetration ratio after eva[%] 110 >Toluene solubles [mass%] 99.0 <Density (15℃) [g/cm3] 1.000 <Thin-film oven testmass chage rate [%] 0.6 >


RemarksPavement


PerformanceElongation [cm] 30 <Fire point　COC [℃] 260 <Softening Point [℃] 56.0 <Penetration (25℃) [1/10mm] 40 <Density (15℃) [g/cm3] ReportingThin-film oven testmass chage rate [%] 0.6 >


Toughness (25℃) N･m 8.0 <tenacity (25℃) N･m 4.0 <

RemarksPavement


Manufacturer Nichireki100(+)

343

1.035Testitems

29.321.5

63.054

(+)0.04

77.8

60.2

Product Modified Asphalt (Type II)

Testitems

130(+)34670117361.145.091100

Manufacturer JXTG Energy

99.991.032

(-)0.03

10299.96

(+)0.11

70.1

Product Straight Asphalt 80/100

1.035

Product Straight Asphalt 60/80Manufacturer JXTG Energy

Testitems

100(+)36281818562.046.570


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7.3 Preliminary Tests

(1) Mixtures used for the preliminary tests

The preliminary test mixtures had three parameters: Coarse aggregate shape, fine aggregate shape, and different fillers. The combinations of the various materials are listed in Table 7.5 in order to clarify the effect of each.

Table 7.5 Preliminary Test Mixtures


(2) Preliminary test items

The preliminary tests will follow the instructions in the Pavement Construction Handbook and use the 5-point method of the Marshall Stability Test to calculate OAC, then OAC will be used to calculate the residual stability and dynamic stability. For the air void, it was not used the theoretical maximum density but rather the maximum density as calculated by the maximum density test (Rice method). This is because Japan is the only country using the theoretical maximum density which is a theoretical value used in calculations for mixture design. In the U.S., Europe, and other countries, the maximum density used during mixture design is an actual value that is calculated from tests, such as the Rice method. Table 7.6 shows the test items.

Table 7.6 Preliminary Test Mixtures


Items Name of test Refference to test method Application

Marshall Stability Test Pavement construction manual As content 5 points

Marshall Stability Test Pavement test manual B001 OAC 1 point

Marshall Stability Test (Soaked) Pavement test manual B001 OAC 1 point

Maximum Density Test Pavement test manual G027 As content 1 point + OAC 1 point

Performance Wheel Trucking Test Pavement test manual B003 OAC 1 point

Mix Design


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(3) Preliminary test results

The results of the preliminary test are as shown in Table 7.7. However, the number of WT specimens was N=5, and the average was set to N=3, excluding the maximum and minimum.

Table 7.7 Preliminary Test Results


(4) Examination of the preliminary test results

The results of the preliminary tests show that when the preliminary representative mixture (1) is the reference point, Table 7.8 shows a comparison of the values of the various characteristics by parameter and Table 7.9 shows the degree of their effects.

Table 7.8 Comparison of the Values of the Various Characteristics by Parameter


Parameter Parameter ParameterMixture No. 1 2 3 Mixture No. 1 4 5 Mixture No. 1 15 16

Crused order Third Forth First Material Mixed Natural Crushed Material StonePowder

Recoverydust Cement

Marshall stability 1 0.97 0.98 Marshall stability 1 0.87 1.09 Marshall stability 1 1.02 0.98Resideual stability 1 1.01 0.88 Resideual stability 1 0.92 0.95 Resideual stability 1 1.02 1.06DS 1 1.00 0.69 DS 1 0.82 1.13 DS 1 0.58 0.72

Fine aggregate FillerCAA


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Table 7.9 Degree of the Effect on Characteristics by the Various Parameters


The following can be said from Tables 7.8 and 7.9:

• With respect to the shape of coarse aggregate, there is little difference in characteristics due to whether they are round (quaternary crushing) or angular (tertiary crushing).

• When comparing the shape of coarse aggregate, flat shapes (primary crushing) has smaller stability, residual stability, and dynamic stability (DS) compared with rectangular shaped aggregate (tertiary crushing), and the degree of effect of the shape is great. The effect on DS is especially significant.

• When comparing fine aggregate, stability and DS are largest for artificial sand followed by mixed sand and natural sand, and the degree of effect is high. As for the artificial sand which is angular, it was confirmed that has superior deformation resistance compared with round natural sand.

• As for fillers, differences have little effect on stability and residual stability. However, their effect on DS was large, and cement and dust with smaller particles than limestone powder are at a disadvantage with regard to flow resistance.

7.4 Verification Tests

(1) Selection of materials for verification test mixtures

The materials used for the representative mixture in the verification tests were selected from those used in the preliminary tests. The materials were selected based on two considerations: The materials used had to be standard material in the target country from the viewpoints of pricing, ease of construction, and availability; and they must be usable as reference points for mixture design conducted abroad.

The aggregate combinations for verification representative mixture are as follow.

[Coarse aggregate] tertiary crushing; [fine aggregate] natural sand 50: artificial sand 50; [filler] cement 4% + recovered dust 1.5%

(2) Selection of verification test mixtures

The three parameters for verification test mixtures were asphalt content, gradation, and asphalt type. The combinations of the various materials are shown in Table 7.10 so that their effects are clear.


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Table 7.10 Verification Test Mixtures

*MLIT standard: 2.36mm passing ±12％, 75μm passing ±5％ **NEXCO standard: 2.36 ㎜ passing ±4％, 75μm passing ±1.5％ Source: JICA Survey Team

(3) Verification test items

Table 7.11 shows the test items in the verification tests.

Table 7.11 Verification Test Items


<Mixture compaction test using SGC>

The SGC (Superpave Gyratory Compactor) is a testing device used for Superpave mixture design. The feature of this testing device is that the relations between the number of gyrations of compaction by the SGC and the height of the mixture can be acquired. Figure 7.1 shows an example of those relations. From this relation, the apparent density and void ratio can be calculated from the number of gyrations.

Compaction parameter N is defined in the following way from the number of gyrations and mixture density.

Nini: Number of gyrations which is an index for ease of compaction and mixtures which are hard to settle down during construction. Immediately after spreading with a finisher and before starting surface compaction.

Ndes: Number of gyrations necessary to make a sample that has the same density as the site density due to forecasted traffic volume. State immediately after putting into service.

Nmax: Number of gyrations necessary to acquire the indoor density that must not be exceeded at the site in order to avoid fluid rutting. State after the end of the design traffic volume.

Items Name of test Refference to test method Application Remarks

Marshall Stability Test Pavement construction manual As content 5 points

Marshall Stability Test Pavement test manual B001 OAC 1 point

Marshall Stability Test (Soaked) Pavement test manual B001 OAC 1 point

Maximum Density Test Pavement test manual G027 As content 1 point + OAC 1 point

Marshall Stability Test Pavement test manual B001 As content 1 point per each

Maximum Density Test Pavement test manual G027 As content 1 point per each

Wheel Trucking Test Pavement test manual B003 As content 1 point per each

Compression Test Pavement test manual B006 As content 1 point per each 0℃、60℃

Compaction Test by SGC SHRP As content 1 point per each

Mix design No.6

Performance

Mix design


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Table 7.12 shows the setting for parameter N which is the compaction caused by traffic volume. Additionally, the air void by mixture that are acquired for each compaction parameter are defined as follows:

Nini: Vini (initial air void)

Ndes: Vdes (design air void)

Nmax: Vmax (final air void)

This study is assuming use at routes with extremely heavy traffic so the design ESAL is a compaction parameter of 30 × 106 or greater.


Figure 7.1 Relations between Number of Gyrations and Sample Mixture Height when Using SGC (Example)


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Table 7.12 Compaction Energy of the Superpave Gyratory Compactor

Source: AASHTO R35

Testing was conducted according to Superpave (Mix Design) Superpave Series No.2 (SP-2). The procedure is as follows:

1) The aggregate and asphalt should be cured in a circulating drying oven set to a temperature of 165°C.

2) The mixture must be thorough until the aggregate is covered with asphalt. 3) The mixture is laid out on a vat at a thickness of 25 to 50 mm. 4) The evenly spread mixture is cured in a circulating drying oven set to a temperature of

145±3°C. 5) The mixture is taken out of the circulating drying oven every 60 minutes and mixed. 6) After curing for two hours, use a bar thermometer to confirm that the mixture is at the

surface compaction temperature. 7) Place the mixture into a mold that has been heated in the circulating drying oven and

compact with the SGC. 8) Calculate Vmax, Vdes and Vini from the relations between the acquired number of gyrations

and height of the mixture.

Ninitial Ndesign Nmax

Less than 0.3 6 50 75

Applications include roadways with very light traffic volumes suchas local roads, county roads, and city streets where truck traffic isprohibited or at a very minimal level. Traffic on these roadwayswould be considered local in nature, not regional, intrastate, orinterstate. Special purpose roadways serving recreational sites orareas may also be applicable to this level.

0.3 to < 3 7 75 115 Applications include many collector roads or access streets.Medium-trafficked city streets and the majority of county roadwaysmay be applicable to this level.

3 to < 30 8 100 160

Applications include many two-lane, multilane, divided, andpartially or completely controlled access roadways. Among theseare medium-to highly-trafficked city streets, many state routes, UShighways, and some rural interstates.

≥ 30 9 125 205

Applications include the vast majority of the US Interstate system,both rural and urban in nature. Special applications such as truck-weighing stations or truck-climbing lanes on two-lane roadwaysmay also be applicable to this level.

Number of Gyrations

a. Design ESALs are the anticipated project traffic level expected on the design lane over a 20-year period. Regardless ofthe actual design life of the roadway, determine the design ESALs for 20 years, and choose the appropriate Ndesignlevel.b. Typical Roadway Applications as defined by A Policy on Geometric Design of Highway and Streets, 1994, AASHTO.

in millions ofESALa Typical Roadway Applicationb


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(4) Verification test results

Tables 7.13 and 7.14 show the verification test results.

Table 7.13 Verification Test Results


Table 7.14 Verification Test Results (SGC Compaction Tests)



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(5) Examination of the verification test results

Dynamic stability (DS)

Figure 7.2 shows the relations between the various parameters and DS. However, mixture No.14 (modified asphalt) is excluded because it is a singular value.

Relation between asphalt content and DS Relations between gradation and DS

Relations between penetration and DS


Figure 7.2 Relations between DS and Each Parameter

The following can be said from Figures 7.2.

• It was confirmed that reducing the quantity of asphalt and degree of penetration was effective in improving flow resistance.

• If gradation is limited to a range of ±4% (2.36 mm Pass, NEXCO standard), flow resistance is assured, but it deteriorates when the range is ±12% (2.36 mm Pass, MLIT standard).

• It is known that when gradation is -4% (lower gradation), DS improves, but the results of these tests show that DS improves even at +4% (upper gradations). It is believed that the increase in finer particles led to a relative decrease in asphalt content.


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Crack resistance

The purpose of this study is to find a mixture method that maximizes dynamic stability while considering durability. Therefore, as a method to assess the dynamic stability and crack resistance of mixtures, compression tests were conducted.

According to the Pavement Study and Testing Handbook (2019 edition), there is a negative relation between compression strength and rutting depth at a temperature of 60°C, and it is said that the higher the compression strength, the better the dynamic stability. (left figure) Additionally, there is a relation between the compression strength comparison between 0°C and 60°C (compression strength at 0°C/compression strength at 60°C) which is supposed to indicate the temperature sensitivity of asphalt mixtures and road surface characteristics. When the compression strength ratio is high (temperature sensitivity high), then rutting is greater (mid figure), and when the compression strength ratio is low (temperature sensitivity low), cracks are more likely to occur (right figure).

Source: Pavement Study and Testing Handbook

Figure 7.3 Relations between Rutting, Cracking and Compression Ratio

Figure 7.4 shows the relations between compression strength (60°C) and DS, and Figure 7.5 shows the relations between the compression strength ratio (0°C/60°C) and DS as confirmed by our results.

Figure 7.4 Relations between Compression

Strength (60°C) and DS Figure 7.5 Relations between Compression

Ratio and DS


From the test results, the followings were derived:


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• The relative relations were not apparent between compression strength/compression ratio and DS were not apparent in these test results.

• According to Table 7.13, mixture No.10 (gradation -12%) had significantly smaller compression strength then the others at 0°C, so it is believed that its crack resistance would be inferior at low temperatures.

(6) Examination of the verification tests (SGC compaction tests)

Relations between final void rate and DS

Figure 7.6 shows the relations between the final void rate and DS according to these results.


Figure 7.6 Relations between Final Air Void and DS

The following results are summarized from Figure 7.6:

• With respect to the relations between the residual air void and DS, when separated at the 2% on the horizontal axis and 800 passes/mm on the vertical axis, most of the data points indicate that when residual void is greater than (or lesser than) 2%, then DS is greater than (or lesser than) 800 passes/mm.

• The sample ⑪ in the block on the upper left of the graph is a mixture with +4% gradation. Because only the gradation was reduced without increasing the asphalt quantity, this occurred because the asphalt content was relatively smaller.

• The sample ⑰ in the block on the lower right of the graph is a mixure that uses asphalt with a high penetration degree (80/100), and it is believed that the effect of soft asphalt was the cause.

• Sample ⑩ deviating from the approximation line has a lower gradation with percentage passing 2.36 mm sieve size of -12%. Although the aggregate space and the final air void were large respectivelly, there was no improvement in DS due to the relative increase in asphalt content.

Compaction characteristics of the various mixtures

In order to verify the compaction characteristics of each mixture, there is a way to calculate and assess the density and void rates of each number of gyrations,. In the SGC compaction tests, in the steps other than the final number of gyrations Nmax, the density is calculated from the mold inner diameter and height. However, because the surface of the sample is not flat, the actual bulk density is different. (Fig. 7.7)


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Figure 7.7 The Concepts of Bulk Density and Apparent Density

In stages other than Nmax, because the actual sample density cannot be measured, the actual bulk density is only estimated. Therefore, after Nmax is completed, the bulk density of the demolded specimen is actually measured, and it is necessary to use that value to calculate the correction factor C.

The correction factor C was calculated in the following manner:

• A sample with 205 gyrations was used. The actual bulk density measured after the final number of gyrations (Nmax) and the apparent density calculated from the height displacement are used to calculated correction factor C.

Correction factor C = Bulk density/Apparent density

• Using C that is calculated from the above formula, the estimated bulk densities Nini and Ndes are calculated, and then the bulk air void for Nini and Ndes are calculated.

Bulk density at No. of gyrations N = Correction factor C × Apparent density at No. of gyrations N

Air void [%] = (1-density [g/cm3]/Maximum density [g/cm3] × 100

* The result of themeasurement test method was used for the maximum density in the calculation.

The apparent density, apparent air void, bulk density, and bulk air void used in this study are defined as follows:

Apparent density: Density calculated from the sample cubic capacity (πR2/4×h;cm3) that was calculated by using the aerial weight of the sample (g), height displacement of the testing device (h), and sample diameter (R).

Apparent density (g/cm3) = Aerial weight/Sample cubic capacity

Bulk density: Bulk density calculated with the method described in " Pavement Survry and Test Method Handbook B008-1 Method of Measuring Density for Dense Graded Asphalt Mixtures”.

Bulk density = Weight in air/(Surface dry weight – Weight in water)

* With water specific gravity at 1.00.

Apparent air void: Air void rate calculated from the apparent density

Bulk air void: Air void calculated from the bulk density

Volume

Counted air● Bulk density ● Apparent densityWeight in air / ( Saturated surface-dry condition - weight-in-water)

Weight in air / Sample volume mesured by caliper(calculated from inner diameter and height)

Blocked air Air with depth Rough-sufaced air


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Table 7.15 and Figure 7.8 show the correction factor and bulk air void calculated from the above formula.

Table 7.15 Correction Factor and Bulk Void



Figure 7.8 Relations between No. of Gyrations and Bulk Void

Figure 7.8 shows that the ten samples used in our tests were almost parallel in their positioning and the compaction characteristics were about the same, but the following were derived:

• Mixture No.10 (gradation -12%) has inferior ease of compaction (workability) compared with the others during construction and it is initially difficult to compact (because the initial void is large), however, the final void is secured. Lowering the gradation decreases workability, but it is believed that flow resistance is improved.

Bulkdensity

(L)[g/cm3]

Correctioncoefficient

L÷I

Nini Ndes Vini Vdes Vmax

2.337 2.412 1.032 2.145 2.316 2.214 2.390 10.7 3.5 2.7

2.365 2.443 1.033 2.162 2.340 2.233 2.417 9.4 1.9 0.9

2.333 2.428 1.041 2.153 2.311 2.241 2.405 10.4 3.9 3.0

2.412 2.470 1.024 2.214 2.389 2.267 2.446 9.1 1.9 1.0

2.275 2.384 1.048 2.066 2.251 2.165 2.359 12.5 4.6 3.6

2.376 2.462 1.036 2.177 2.352 2.256 2.437 9.3 2.0 1.0

2.339 2.419 1.034 2.140 2.314 2.213 2.393 10.6 3.3 2.3

2.374 2.429 1.023 2.179 2.352 2.229 2.406 10.3 3.2 2.3

2.366 2.437 1.030 2.171 2.343 2.236 2.413 9.7 2.6 1.6

2.365 2.427 1.026 2.176 2.342 2.233 2.403 10.0 3.1 2.1

Mixtur

7

9

11

13

17

8

10

12

Ｃ

6

Nmax

14

Nmax Nini Ndes

Apparent density(M)

[g/cm3]

2.475

2.486

2.477

2.480

2.478

2.464

2.502

2.495

2.473

2.487

Estimeted bulk densityusing Ｃ

(N)[g/cm3]Ｃ×M

Bulk air void [％]

(1-N/K)*100

Maximumdensity (K)

(Test result)

Apparentdensity

(I)[g/cm3]

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 50 100 150 200 250

1086121317141197

Number of Gyrations


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• Mixture No.8 (asphalt content -0.5%) has better workability than the others and initial compaction is also easy. Moreover, because the final void can also be secured, it is a mixture with both good workability and flow resistance.

• Mixture No.7 (asphalt content +0.5%), mixture No.9 (gradation +12%), and mixture No.11 (gradation +4%) have good workability and initial compaction is also easy, however, the final void cannot be secured. Increasing the asphalt content or raising the gradation help workability but decrease flow resistance.

• The correction factor C deviated from 2 to 5% depending on the mixture and there was no specific tendency.

7.5 Summary

<Mixture design>

• The OAC for the various mixtures in the preliminary mixture tests was from 4.6 to 5.0%. It was lower than the 5.0 to 5.5% that is the norm for the general dense graded asphalt mixture (20) used in Japan. The reasons for this could be the characteristics of the aggregate used in the study and because the maximum density used was not the theoretical maximum density but the direct measuring density from tests.

<Marshall stability tests>

• Overall, the Marshall stability was high. The reason for this is likely to be because of the characteristics of the aggregate used in this study. The parameter that has a large effect on Marshall stability is fine aggregate.

<WT tests>

The following items were shown to be effective as methods for improving DS.

a) Material

• Use angulated coarse aggregate with less flatness • Increase the ratio of artificial sand • Filler uses stone powder • Reduce the asphalt penetration grade

b) Proportion

• Reduce the asphalt content • Adjustment of the gradation within the acceptable range (percentage passing 2.36mm sieve size ± 4%,

75 μm sieve size ± 1.5%)

<Compression tests>

• Within a range of ±4% gradation and ±0.5% OAC, there should not be a major change in crack resistance and fragility. However, when gradation is at ±12%, there are concerns about cracking resistance at low temperatures.

• No correlation with DS value was found.

<SGC mixture compaction tests>

• If the final air void is 2% or more, it is expected that there is a high possibility that a high DS value can be obtained.

• Lower gradations help to improve flor resistance compared with other gradations, but it is believed that workability will be lower than other mixtures.


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• Upper gradations may have better workability but their flow resistance may be inferior.

The results of these test were derived from using high quality domestically produced coarse aggregate. It will necessary to follow the precautions below when working at overseas sites.

• In order to reproduce the results of these tests, it will be necessary to preconfirm with local materials.

• Even if good quality materials are used, the pavement may be damaged depending on the construction. For this reason, in construction on site, a careful construction management and quality control system is important.

Documents

RESEARCH ON IMPROVEMENT OF RUT RESISTANCE FOR ROAD