Technical Problems of Pavement in Tropical Countries

and Their Solutions

Technical seminar on road transportation infrastructure for ASEAN integration

13June, 2016

Moriyasu FURUKI Senior Advisor, JICA

20160531

I. ASEAN Road Transport in 21st Century (1) Economic Growth

ASEAN economic growth depend thoroughly on the international specialization which will necessarily develop international trade and cross board transport.

Elimination of tariffs in ASEAN and smooth cross border procedures (Cross Border Transportation Agreement).

Improvement of transportation infrastructure.

Example: Second Friendship Bridge between Mukdahan and Savanakett, open to traffic at Jan. 2007. Second Friendship Bridge

Year Truck Bus Car Other Total

2007 12,517 8,205 19,061 5,374 45,157

2008 21,481 17,142 43,931 8,151 90,705

2009 27,502 32,015 64,031 8,674 132,209

2010 29,024 43,308 82,661 8,639 163,632

2011 29,274 54,871 97,331 7,785 189,207

Ratio(2011/2007) (annual

growth %)

2.34 (23.6%)

6.69 (60.8%)

5.11 (50.3%)

1.45 (9.7%)

4.19 (43.1%)

Table Traffic from Thailand to Laos (vehicle/ year)

(2) Expanding cross border transport

(3)Improving ASEAN (ASIAN) highway

Table Asian Highway design standards 1993

■ Design standard and pavement design

Traffic load to pavement is expressed by equivalent single axle load (ESAL).

Minimum ESAL for each Hwy classification should be set.

■ Increase of large truck and over loading Difficult to control large truck comes into from

other countries in the continent. Overloading is an hot issue in GMS countries.

Over loaded truck full of sown rosewood timber estimated to be more than 120t .

II. Typical Pavement Damage How to take measures to deal with?

(1) Plastic Rutting

Deep plastic rutting is developed on the climbing sections of national road of Ethiopia.

Rutting : ① mechanical deformation ( in subgrade or base) ② Plastic flow (unstable asphalt layer) ③Wheel path consolidation & wearing

Wearing c.

Binder c.

Asphalt stabilization

Mechanical stabilization

Crusher run

One lane width

Fig. Cross section of rutting under very heavy traffic in Japan

①

②

■What is happening underneath?

There are two approach to eliminate plastic rutting.

a. Strengthen the mastic Modified asphalt

b. keep aggregate skeleton (matrix)Stone Matrix As

Plastic rutting is caused by inadequate mix design where excessive asphalt together with fine is found. What is more, it will become serious if mastic (asphalt + filler) is not stiff enough.

Fig. Mechanism of plastic rutting (particle size is not in scale)

Mastic (asphalt +filler) + fine

aggregate

Large & medium size aggregate

Movement of asphalt mix

Vehicle wheel

■Another example of plastic rutting Good section Poor section

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Out of Grading envelope*n

Excessive fine material & bitumen Grading is completely out of quality control allowanace.

* In the first place, actual distribution should be within the permissible deviation of quality assurance.

Grading envelope

(Allowable line for Design)

Actual distribution*l

Balanced distribution of fine material & bitumen. Lower percent of fine and bitumen.

■Practical approaches to prevent plastic rutting at mix

design stage

1) Empirical approach

Several requirements for anti-rutting measures are pointed

out.

2) Wheel Tracking (WT) test is to run simulative tests that

measure HMA qualities by rolling a small loaded wheel device repeatedly across a prepared HMA specimen.

3) Air voids control (Volumetric Design Method)

Adopted in the SUPERPAVE method and in some other

places where SGC (Superpave Gyretory Compactor) is

used instead of Marshal Compactor.

4) Adoption of Gap type mix asphalt such as SMA.

a. HMA type selection and mix design

① Mix distribution should be under the center line of grading

envelope.

② Asphalt contents should be below the optimum value derived from Marshal test.

③ Marshal stability should be above 3.75kN (75blow), stiffness (Stability/flow value ) should equal or above 2,500 kN/m.

④ Collected dust should not exceed 30% of filler (passing 75µm sieve).

⑤ If DS requirement is not met, reduce 2.36mm sieve passing contents, and also reduce 75µm sieve passing contents. If not enough, use more hard (high melting point) bitumen.

b. Asphalt choice penetration grade of asphalt

c. For heavy traffic sections, apply anti-rutting scheme for binder course

as well. modified asphalt

１）Empirical approach

Countermeasures by Japan Road Association

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■Standard HAM of Japan

Typical grading envelope for 14 mm dense graded mix

■Grading envelope and recommended grading curve for dense graded mix resistant against rutting

Austroads, Guide to Pavement Technology Part 4B: Asphalt, 2014

Empirical mix design recommends to set mix curve lower (red line) at fine aggregate below 2.36mm.

2) Dynamic Stability (DS) Number as performance requirement.

Classification Category-Class

Pavement Design Traffic (per day)

Dynamic Stability (DS)

Category I, II Category III-Class 1,2 Category IV-Class 1

3,000 or more 3,000

Below 3,000 1,500

Others 500

Table : Dynamic stability requirement

Road Department, MLIT, Japanese

DS is defined by a number of path by a test wheel until 1 mm rut has developed on the test pavement piece.

DS number of 800 is used as a target for HMA of strait asphalt in a local government of Japan.

出典：「骨材間隙率に基づく加熱アスファルト混合物の容積配合設計法の提案」

郡司保雄・井上武美・赤木寛一（土木学会舗装工学論文集 第５巻 2000 年12 月）

Voids in mix (VIM) : %

Dynam

ic S

tability (

DS)

: path

/mm

Fig. VIM and DS

Strait asphalt

Modified asphalt

■ Target of DS number

3,000

1,500

Accumulated number of large vehicle

■Difference of Rutting by DS (below 5,000/day.lane)

DS≦500

５００＜DS≦８００

８００≦DS

By Akio IIDA

Aggregate selection.

Asphalt binder selection. performance grading

(PG) system

Sample preparation (including compaction). SGC

Performance Tests. being developed

Density and voids calculations. Volumetric Mix Design Air voids (Va), Voids in the Mineral Aggregate (VMA), Voids Filled with Asphalt (VFA)

Optimum asphalt binder content selection.

Moisture susceptibility evaluation.

3）Superpave Procedure (Superior Performing Asphalt Pavement System )

The Superpave mix design method consists of 7 basic steps:

VMA

VFB=VFA

Basic Terminology for Volumetric Mix Design

Fig. Constituents of a compacted asphalt mix

■Superior Performing Asphalt Pavement System

VIM

VMA: Voids in Mineral Aggregate

VIM: Voids in Mix

VFB=VFA: Voids Filled with Binder/Asphalt

Superpave Mix Design : January 26, 2011 Author: Pavement Interactive Introduction to Superpave Gyratory Compaction

and Mixture Requirements Asphalt Institute

Superpave Gyratory Compactor (USA)

Concept of Superpave Gyratory Compactor

SGC sample & Marshal(left) Compactor sample(right)

Sample preparation (including compaction).

The Superpave gyratory compactor (SGC) was developed to simulate actual field compaction particle orientation with laboratory equipment.

Gmm : Theoretical maximum specific gravity

Table Superpave Gyratory Compaction Effort ⇒establish optimum binder content

⇒to check workability

⇒to check ultimate condition

Superpave Mix Design : January 26, 2011 | Author: Pavement Interactive

Density and voids calculations to get optimum binder content

Selection of optimum asphalt binder content example : 4 basic steps

Superpave Mix Design : January 26, 2011 | Author: Pavement Intera

For routine mix design, the level of compaction depends on the traffic level as follows:

light traffic – 50 cycles medium traffic – 80 cycles Va (VIM) 3-6% heavy traffic – 120 cycles voids at maximum cycles – 250 /350 cycles Va (VIM) >2.0%

Gyropac

■Austroads

Servopac

Austroads, Guide to Pavement Technology Part 4B: Asphalt, 2014

Austroads also provide comprehensive guide on pavement where Volumetric Mix Design is introduced and unique gyratory compactors was developed. The gyratory angle is 2.0degree and the vertical force is 500kPa.

If the air voids content of asphalt in-service is too low (less than about 2%), plastic flow may occur resulting in flushing, bleeding, shoving or rutting of the pavement. Austroads, “Guide to Pavement Technology” 4.3.6

■Particle Size Distribution (Grading) dense graded asphalt

(DGA), also called asphaltic concrete (AC)

stone mastic asphalt (SMA)

open graded asphalt (OGA), also called open graded porous asphalt (OGPA) and open graded friction course (OGFC)

fine gap graded asphalt (FGGA).

(particle size is not in scale)

Vehicle wheel

Force flow

Large & medium

size aggregate

Fig. Concept of stone matrix model

■ Particle skeleton (matrix)

4) Adoption of Gap type mix asphalt

Air voids

Matrix or skeleton of aggregate is the key of anti-rutting capability. The skeleton will support the wheel lord and eventually seized air does not fully escape and remained. So air voids could be a good parameter to check anti-rutting capacity.

■Various Types of Water Intrusion

26

地下水

毛管現象 地下水の上昇 水蒸気

高地からの流入

端部での移動

舗装破損部からの流入

路面勾配による排水

雨水Precipitation

Surface water drainage

②Seepage from higher ground

①Infiltration from surface

④Upward movement of water-table

⑥Vapor movement ⑤Capillary w.

Water-table

③ Seepage from shoulders & side ditches

Fig. Movements of water

Ground surface

water

(3) Water Intrusion

27

Conceptual relations between moisture content & bearing capacity of base course.

Water content in the base/sub-base

Granular material

Clayish material

N=0.0002228×TA×CBR1.875 CBR ×1/2 N0.27N CBR ×2 N3.67N

■Why water is so risky?

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<by Benkelman beam>

■ Ｄｉｆｆｅｒｅｎｃｅ ｏｆ Pavement Dｅｆｌｅｃｔｉｏｎ ｂｙ Sｅａｓｏｎ

Deflection in rainy season Ave. 0.56ｍｍ、σ＝0.16ｍｍ

Deflection in dry season

Ave. 0.42ｍｍ、σ＝0.14ｍｍ

ｐｏｉｎｔｓ

Deflection (mm)

By Kamimura, Konno, Furuki, 2014

29

‘FLEXIBLE PAVEMENT EVALUATION WITH THE BENKELMAN BEAM’ C. G. Kruse, Research Project Engineer Minnesota Highway Department, 1968

SCL: Silty Clay Loam FS: Fine Sand

Fig. Influence of Water/frost , seasonal variations bearing capacity of base course/subgrade (measured by pavement

deflection)

In Sendai Japan (Source:Japan Road Association)

■ Influence of Water/Frost

30

Pavement damaged by seepage from higher ground on trunk road in Ethiopia （Rainy season, in August）

Mountain side

Mountain side

:indicates damaged area

■Damage by Water Intrusion

■Damage by Water Intrusion (Continued)

31

Damages by water in base course at a sag point. in Ethiopia

Structural damage at sag

Fig. Longitudinal profile

River

Weak point

Rising water level

■Fine Grain Pumping

32

Base course condition in dry season (partial saturation)

Base course condition in rainy season (saturation)

Muddy water pumping out of base course of asphalt pavement (Ethiopia)

■Drainage System Design

1. Protect the road from

surface and ground

water.

2. good road drainage

system, is vital to the

successful operation

of a road.

3. It is impossible to

guarantee that road

surfaces will remain

waterproof

throughout their lives.

ensure that water

is able to dram away

quickly from within

the pavement layers

(ORN31)

Ground water

Ground water

Surface water

Surface water

■ Example: Groundwater in Cutting Section

Asphalt concrete (Ac)

Coarse graded asphalt concrete

Crusher-run (Granular sub-base)

ｄ＝8ｃｍ

ｄ＝21ｃｍ

ｄ＝16.ｃｍ

Subgrade

Tokyo Metropolitan Exp-way ‘KARIBA-SEN’

Total thickness ｄ＝45ｃｍ

SN>10

34

Courtesy of Mr. Yamamoto, Metropolitan Exp. Way Tec. C.

35

What happened?Surface Damages

Left : alligator crack

Right : pothole

Courtesy of Mr. Yamamoto, Metropolitan Exp. Way Tec. C.

:Existing drain pipe is not working well.

Bed rock

Fill

Ｓｐｒｉｎｇ ｗａｔｅｒ

Wearing course d=40mm

Binder course d=40mm

Base course

（Coarse graded Ac）

d=160mm Sub-base

（Crusher-run）

d=210mm

Cracked and cannot stand -peeling off of bitumen from aggregate

Core sample

Rainfall

Total daily traffic : 101,000, Heavy trucks: 15,000 !

Confined groundwater

Courtesy of Mr. Yamamoto, Metropolitan Exp. Way Tec. C.

■Pavement Damage Caused by High Water Table

36

■Countermeasure

Fill Perforated drain pipes are installed

Bed rock

Confined groundwater

Rainfall

Installation

Precipitation and pressure head

Base level of base course

Pressure head of

groundwater

Detailed section

Precipitation

Courtesy of Mr. Yamamoto, Metropolitan Exp. Way Tec. C.

Newly installed drain pipe

37

■Overseas Road Note 31 - Drainage

“Under no circumstances should the ‘trench’ type of cross-

section be used in which the pavement layers are confined

between continuous impervious shoulders. “ (p.19)

38

‘trench’ type cross-section

×

“It is impossible to guarantee that road surfaces will

remain waterproof throughout their lives, hence it is

important to ensure that water is able to drain away

quickly from within the pavement layers.” (p.19)

39

Highway Design in Ethiopia (Supported by China)

Expressway in Ethiopia

■Example of Base Course Drainage

Penetratio Macadam pavement in Myanmar -Base course drainage is carefully carried out

40

■Base Course Drainage

41

Good maintenance work --important and thankful to those people

A example of good devise for better drainage

Maintenance work

■Base Course Drainage

42

Alligator cracks on low embankment section(near 42km)

Damage repaired （near 30km）

(4) Damages Caused by Base Course Failure

■Degradation of Cement Stabilized Sub-base Course Sub-base course which was treated with 2% of cement deteriorated after 10 years of construction on the Natl. road #9 in Laos.

43

Repairing work is underway

in 2015.

Replacing subgrade

material.

Surface conditions suggest

possible damage of subgrade.

(Laos natl. hwy No. 9 in 2012)

■Degradation of Cement Stabilized Sub-base Course (Continued)

44

Pavement Compositions

15cm

10cm

30cm

10cm?

Base course (CBR169)

Recycled subgrade (CBR9)

Old sub-base course

Natural Ground

crushed stone

Laterite cement stabilization

Cement stabilization

Sub-base course (CBR23)

45

Picture (a) shows degraded sub-base course where laterite with higher PI, while picture (b) shows sub-base course with higher bearing capacity where laterite with lower PI value is used for cement stabilization.

Cement stabilized sub-base course deteriorated in places. (Laos natl. hwy No. 9)

■ Damaged Sub-base Treated by Cement Stabilization of 10 Years Ago.

(a)Degraded sub-base course (b)Better conditioned sub-base course

46

破損個所

健全な個所

PI

■Influence of PI (Plasticity Index) on the Pavement

Damaged pavement

Sound pavement

PI of base course materials at damaged and sound pavement at this project site* are compared and apparent difference was found as shown below. ＊The test was done at the spot and which means not necessarily reflected the PI of original material ahead of cement treatment in ten year before.

■Another Example of Damage of Cement Stabilized Layer.

Ac:5 cm, Cement stabilized base course:15cm Material for base course is silty cray with PI 15, mixed with granular material.

47

Surface damage caused by failure of cement stabilized base course.

In Tajikistan

48

■Long Term Behavior of Lightly Cemented Material (South Africa)

“PAVEMENT ANALYSIS AND DESIGN SOFTWARE (PADS) BASED ON THE SOUTH AFRICAN MECHANISTIC-EMPIRICAL DESIGN METHOD” H L Theyse and M Muthen

■Overseas Road Note (ORN 31)

49

‘If cement or lime-stabilized (CS/LS) materials are

exposed to air, the hydration products may react with

carbon dioxide thereby reducing the strength of the

material by an average of 40 percent of the unconfined

compressive strength (Paige-Green et al(1990)).’

(P.32 )

Note ●Hydraulic chemical reaction

「Alite C3S」 Hydration:2{3CaO・SiO2} + 6H2O → 3CaO・2SiO2・3H2O + 3Ca(OH)2

「Blite C2S」 Hydration :2｛2CaO・SiO2｝ + 4H2O → 3CaO・2SiO2・3H2O + Ca(OH)2

●carbonation of cement mix

Ca(OH)2＋H2O＋CO2→ Ca(OH)2＋H+＋HCO3-→ CaCO3＋2 H2O

Summery of Cement Stabilized Base course (CSB) ① Reflection cracking and/or stripping are reported regarding Ac on CSB base course. ② CSB for sub-base course is standardized in ORN31 and other countries. Damage of CSB with low cement using laterite soil was reported however. The cause is not clear, chemical or mechanical? ③ Not use CSB for clay glut soil(noted in ORN31). ‘PI’ should carefully be observed (PI<9:Japan). ‘Water seems to be another key factor. ← :Laterite CSB in wet condition showed poor performance (Thailand). Another factor is the thickness of CSB layer, for which the strain should be minimized to eliminate ‘kneading’ by traffic load.

■Cement Stabilization (of Laterite)

50

Surface crack on local road (Nagano, Japan)； Shrinkage and/or structural crack developed but not seriously damaged because of very light traffic.

Surface crack on street; Once covered by surface dressing, but probably base course material might be degraded and alligator cracks developed shortly. (Tokyo)

(5) Other Structural Damages

Stripping of road surface of 4cm thick on existing Ac pavement (Tanzania)

Stripping of road surface of 10cm thick on cement stabilized base course at slope section.(Tajikistan)

(6) Slippage of Ac Layer

References Yang H. Huang, “Pavement Analysis and Design” Pearson

Education, Inc., 2004.

Japan Road Association, “Maintenance Guide Book of Pavement”,

2013 (translation is now being prepared)

Transport Research Laboratory, “Overseas Road Note 31,” 1993.

AASHTO, “Design of Pavement Structures”, 4th Edition with 1998

Supplement

AASHTO, “Mechanistic-Empirical Pavement Design Guide”, Interim

Edition: A Manual of Practice, PE Exam Edition

E. J. Yoder, “Principles of Pavement Design,” John Wiley & Sons,

Inc. 1959.

“South African Pavement Engineering Manual” (an initiative of the

South African National Roads Agency Ltd.) 2013.

PIARC, “Bituminous Materials with a high Resistance to Flow

Rutting”, 1995

Austroads, “Guide to Pavement Technology”, 2012