1. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
INTRODUCTION
Differences Between Concrete and Asphalt Pavement
Historically, pavements have been divided into two broad categories, rigid and flexible.
These classical definitions, in some cases, are an over-simplification. However, the terms
rigid and flexible provide a good description of how the pavements react to loads and the
environment.
The flexible pavement is an asphalt pavement. It generally consists of a relatively thin
wearing surface of asphalt built over a base course and subbase course. Base and subbase
courses are usually gravel or stone. These layers rest upon a compacted subgrade (compacted
soil). In contrast, rigid pavements are made up of portland cement concrete and may or may
not have a base course between the pavement and subgrade.
The essential difference between the two types of pavements, flexible and rigid, is the manner
in which they distribute the load over the subgrade. Rigid pavement, because of concrete’s
rigidity and stiffness, tends to distribute the load over a relatively wide area of subgrade. The
concrete slab itself supplies a major portion of a rigid pavement's structural capacity. Flexible
pavement, inherently built with weaker and less stiff material, does not spread loads as well
as concrete. Therefore flexible pavements usually require more layers and greater thickness
for optimally transmitting load to the subgrade.
The major factor considered in the design of rigid pavements is the structural strength of the
concrete. For this reason, minor variations in subgrade strength have little influence upon the
structural capacity of the pavement. The major factor considered in the design of flexible
pavements is the combined strength of the layers.
One further practical distinction between concrete pavement and asphalt pavement is that
concrete pavement provides opportunities to reinforce, texture, color and otherwise enhance a
pavement, that is not possible with asphalt. These opportunities allow concrete to be made
exceedingly strong, long lasting, safe, quiet, and architecturally beautiful. Concrete
pavements on average outlast asphalt pavements by 10-15 years before needing
rehabilitation.
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2. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
Introduction to the Pavement Design Process
Effective pavement design is one of the more important aspects of project
design. The pavement is the portion of the highway which is most obvious
to the motorist. The condition and adequacy of the highway is often judged
by the smoothness or roughness of the pavement. Deficient pavement
conditions can result in increased user costs and travel delays, braking and
fuel consumption, vehicle maintenance repairs and probability of increased
crashes.
The pavement life is substantially affected by the number of heavy load
,repetitions applied, such as single, tandem, tridem and quad axle trucks
buses, tractor trailers and equipment. A properly designed pavement
structure will take into account the applied loading
A typical flexible-pavement structure is shown in Figure bellow. It illustrates the terms used in this
manual that refer to the various layers. All the layers shown in Figure bellow are not present in every
flexible pavement.
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3. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
A new 6-lane expressway is proposed to be built from Bandar A to Bandar B. The length of the
expressway is approximately 25 km.
AASHTO Flexible Design Procedure :
The design basis presented in this document is based upon the 1993 American Association of State
Highway and Transportation Officials (AASHTO) Design Guide. The objective is to provide design
parameters for local materials and conditions, and to provide guidance on the use of AASHTO
equations.
For estimating the thickness base on the AASHTO design method procedure we need to
determine the SN ( structural number ) from the design chart for flexible pavement or using
the equation as the above indicate :
In this project we have decided use the chart instead of equation so before using the chart we
need to have some parameters for using it :
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4. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
1.reliability that be given in the project ,
Reliability= 85%
2.Standard Deviation that be given ,
Standard Deviation= 0.45
3.ESAL
4.The resilient Modulus for the different roadbed layers
5.Design Serviceability Loss,
∆PSI = PSI terminal – PSI initial = 4.2 – 2.0 = 2.2
By the above information at first we require to have the ESAL ( equivalent Single Axle Load)
Traffic analysis :
Overview
Pavement is designed based on the traffic loadings expected in the highway’s design lane,
the lane expected to experience the greatest number of 18,000 pound equivalent single axle
loads (18K ESALs) over the design period (usually 20 years). The traffic data required to
calculate the ESALS include:

base year ADT

ADT traffic growth rate for the design year

percentage trucks, including dual-rear-tire pickups and buses, for each classification
category

directional distribution for the design period

lane distribution factor for the design period.
Traffic Data Provided

ADT traffic growth rate for the design year

percentage trucks, including dual-rear-tire pickups and buses, for each classification
category

directional distribution for the design period.
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5. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Traffic Data
ADT
% Trucks
1ffic growth factor
Design period
Directional distribution
Lane distribution
Slow lane
Middle lane
Fast lane
Lane width
= 25, 500 vehicles (both direction)
= 15*
= 12.58
= 10 years
= 60/40
= 65%
= 25%
= 10%
= 3.70 m ( 12 ft)
*Detailed information on trucks
Cars, pickups, light vans
Single-unit truck
Tractor semi-trailer truck
= two 2000-lb (8.9-kN) single axles ( 40%)
= 8000-lb (35.6 kN) steering, single axle ( 15%)
= 22,000-lb (97.9-kN) drive, single axle ( 15%)
= 10,000-lb (44.5-kN) steering, single axle (10%)
= 16,000-lb (71.2-kN) drive, tandem axle (10%)
= 44, 000-lb (195.7-kN) trailer, triple axle (10%)
Tandem drive axle on a tractor frame during manufacturing
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6. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
Determine ESAL :
ESAL initial = ADT * %T * Gi * N * 365 * Y
ESAL final = ESAL ini * Dd * Ld
Determine N :
In terms of the table 6.4 the EALF can be found so :
Cars, pickups, light vans
2 * 0.00018 = 0.00036
0.00036 * 0.4 = 0.000144
Single-unit truck
0.0343*0.15=0.00514
2.18*0.15=0.327
Tractor semi-trailer truck
0.0877*0.1=0.00877
0.0472*0.1*2 =0.00944
0.723*0.1*3 = 0.2169
N = 0.000144 + 0.00514+0.327+0.00877+0.00944+0.2169
N= 0.567
ESAL initial = 25500 * 0.15 * 12.58 * 0.567 * 365
ESAL initial = 9958364.168
ESAL final = 9958364.168 * 0.6 * 0.65
ESAL final = 3883762.025 psi
ESAL final = 3.9 * 10^6 psi
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ECV 5606
Saeed Badeli

7. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
Determine MR :
Resilient Modulus (Mr) is a fundamental material property used to characterize unbound
pavement materials. It is a measure of material stiffness and provides a mean to analyze
stiffness of materials under different conditions, such as moisture, density and stress level. It
is also a required input parameter to mechanistic-empirical pavement design method. Mr is
typically determined through laboratory tests by measuring stiffness of a cylinder specimen
subject to a cyclic axle load. Mr is defined as a ratio of applied axle deviator stress and axle
recoverable strain.
Reslient Modulus Experimental Setup
Resilient modulus is determined using the triaxial test. The test applies a repeated axial cyclic
stress of fixed magnitude, load duration and cycle duration to a cylindrical test specimen.
While the specimen is subjected to this dynamic cyclic stress, it is also subjected to a static
confining stress provided by a triaxial pressure chamber. It is essentially a cyclic version of a
triaxial compression test; the cyclic load application is thought to more accurately simulate
actual traffic loading.
In this project we have resilient modulus for 3 different layers this means that we do not need
to find the resilient modulus base on AASHTO design method.
Resilient modulus properties :
SMA, MR=3104 Mpa (450,000 psi)
SMA (Stone Matrix Asphalt)
Base, MR= 241 Mpa (35,000 psi)
Subbase, MR= 93 Mpa (13,500 psi)
Subgrade, MR ( Subgrade Resilient Modulus Varies throughout the project length)
Subgrade, MR= 48 Mpa (7,000 psi)
The Subgrade resilient modulus is the effective resilient modulus.
So we have enough information for determining the Structural Number by using the chart.
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8. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
As the above chart indicates we have 3 different Structural Number by 3 different roadbed
Resilient modulus,
Base resilient modulus = 35000 psi
SN 1 = 2.30
Subbase resilient modulus = 13500
SN 2 = 3.30
Subgrade resilient modulus = 7000
SN 3 = 4.00
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9. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
Determine the Thickness :
For determining the thickness by AASHTO ,it gives the equation
SN = a1D1 + a2D2m2 + a3D3m3
In which a1 , a2 and a3 are the layer coefficients of the asphalt, base and subbase layers
which be given in this project
D1 , D2 and D3 are the thicknesses of the different layers
,m2 is the drainage coefficient for the base layer and m3 for the subbase layer.
Design of layer thickness :
D1 = SN1 / a1*m1
D1=2.30/0.44*1
D1=5.227 ≈ 5.50 inch = 13.97 cm
SN* = D1*a1*m1
SN* = 5.50*0.44*1
SN*=2.42 ≥ 2.30 OK√
-----------------------------------------------------------------------------------------------------D2 = (SN2-SN1*)/(a2*m2)
D2=(3.30-2.42)/(0.15*0.75)
D2=7.82 inch ≈ 8.00 inch = 20.32 cm
SN*2 = 8.00*0.75*0.15
SN*2 = 0.90
SN*1 + SN* 2 ≥ SN2
0.90 + 2.42 = 3.32
3.32 ≥ 3.30 OK√
-----------------------------------------------------------------------------------------------------D3 = (SN3 – ( SN* 2 + SN*1 )) / (a3*m3)
D3 = (4.00 – (0.90+2.264)) / (0.75*0.10)
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10. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
D3 = 11.147
D3 = 11.50 inch = 29.21 cm
SN* 3 = 11.50*0.75*0.10
SN* 3 = 0.8625
SN*3 + SN*2 + SN*1 ≥ SN3
0.8625+0.90+2.42=4.183
4.00
OK√
So the layer thickness for the asphalt , base and subbase are :
D1=5.50 inch = 13.97 cm
D2=8.00 inch = 20.32 cm
D3=11.50 inch = 29.21 cm
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11. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
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ECV 5606
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12. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
JKR method based on CBR
California Bearing Ratio (CBR)
The California Bearing Ratio (CBR) test is a simple strength test that compares the
bearing capacity of a material with that of a well-graded crushed stone (thus, a high
,quality crushed stone material should have a CBR @ 100%). It is primarily intended for
but not limited to, evaluating the strength of cohesive materials having maximum
particle sizes less than 19 mm (0.75 in.) (AASHTO, 2000). It was developed by the
California Division of Highways around 1930 and was subsequently adopted by
numerous states, counties, U.S. federal agencies and internationally. As a result, most
agency and commercial geotechnical laboratories in the U.S. are equipped to perform
CBR tests.
JKR Method
This method is a combination of two methods using a formula and figures from the result of
the testing. A complete guideline for pavement design can be found in “ Arahan Teknik
(Jalan) 5/85”. The thickness of the pavement depends on the CBR value and the Total
Cumulative of Standard Axle ( JBGP ).Some data need to be collected before starting any
design. They are;
i. Design life.
ii. Road hierarchy base of JKR classification.
iii. Average daily traffic volume.
iv. Percentage of commercial vehicle.
v. Yearly rate of traffic growth.
vi. CBR value for sub-grade.
vii. Topography condition.
Design Life
The design life on JKR Design Method is suggested for 10 years. The design life begins from
the road starts in use for traffic until the maintenance is required.
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13. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
This manual is to be used for the design of flexible pavements for roads. It comprises of
details for the thickness design,materials specification and the mix design requirements.
For determining the thickness JKR recommend to use the bellow nomograph
So in terms of the above nomograph we require to find the CBR of the subgrade and also
Equivalent Axle Load.
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14. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
FHWA Class 9 five-axle tractor semi trailer (18 tires total). A typical tire load is 18.9 kN (4,250 lbs) with an inflation pressure of 689 kPa
100 psi
Traffic Estimation
Vo = ADTT*Dd*Ld*365*Pc/100
ADTT = ADT * T%
ADTT = 25500*0.15
ADTT = 3'825.00
Determine Pc :
In terms of the table 6.4 the EALF can be found so :
Cars, pickups, light vans
2 * 0.00018 = 0.00036
0.00036 * 0.4 = 0.000144
Single-unit truck
0.0343*0.15=0.00514
2.18*0.15=0.327
Tractor semi-trailer truck
0.0877*0.1=0.00877
0.0472*0.1*2 =0.00944
0.723*0.1*3 = 0.2169
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15. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
Pc = 0.000144 + 0.00514+0.327+0.00877+0.00944+0.2169
Pc= 0.567
Vo=3825*0.60*0.65*365*0.567
Vo = 308'725.1213
In which Vo is the initial annual commercial traffic for one direction .
The total number of commercial vehicles for one direction Vc is obtained by :
Vc = (Vo*(((1+r)^x) – 1 )) / r
Vc = Vo * Gi
Vc= 308725.1213 * 12.58
Vc = 3883762.026 psi
Vc = 3.9 * 10^6
In this case we have :
The total equivalent standard axles (ESA) can determine as :
ESA = Vc
ESA = 3.90 * 10^6
The maximum hourly traffic volume is calculated as follows :
C=I*R*T
For determining the above equation we should use the table 3.2 , 3.3 and 3.4 on the JKR
Road type = Multilane
I = 2000*3 = 6000
R= 1.00
T= 100 / (100+pc)
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16. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
T= 100/(100+15)
T= 0.87
C= 6000 * 1 * 0.87
C= 5220 veh/hour/lane
C reflects 10% of the 24 hours , then the one way daily capacity is as follows:
C= 10 * c
C = 52200 veh/day/lane
V = ( ADT * (1+r)^x) / 2
Gi=12.58
For finding r ,we can use the 6.13,
r=0.05
V= ( 25500 * (1+0.05)^10 ) / 2
V = 20768.41 veh/day/lane
Hence capacity has not been reached after 10 years .
Determine the subgrade CBR:
The CBR can be found by the resilient modulus of subgrade soil which is :
Subgrade, MR= 48 Mpa (7,000 psi)
In terms of the subgrade resilient modulus we have :
CBR = 48 / 10
CBR = 4.80
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17. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
From the above nomograph, the chart shows that for ESA of 8.30*10^6
,the required TA is 24.70 cm
Determine the Structural Layer Coefficient :
For estimating this number for each layers we can use the Table 3.5
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ECV 5606
Saeed Badeli

18. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
a1=1.00
a2=0.32
a3=0.23
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Saeed Badeli

19. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
Design of Layer Thickness :
In terms of the table 3.8 ,the minimum thickness of bituminous layer in this case will be 15.0
cm.
TA = a1D1 + a2D2 + a3D3
1st Trial :
Nominate
D1=15.00 cm
D2=16.00 cm
D3=18.00 cm
Then
TA = 1.00*15.00 + 0.32*16 + 0.23*18
TA = 24.26 ≤ T
Second Trial
D1=15 cm
D2=18 cm
D3=18 cm
T
24.
≈T
So the Final thickness of Asphalt, Base and Subbase layers are :
D1 = 15 cm
D2 = 18 cm
D3 = 18 cm
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20. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
Cost considerations :
Cost of Materials and construction (includes transportation cost)
Crusher-run Base
Sand Subbase
Stone Mastic Asphalt
Cost of construction
cubic meters * density = tonnes
20
= RM 22.00 tonne
= RM 15.00 per tonne
= RM 330.00 per tonne
RM 15.50 per sq meter
ECV 5606
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21. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
Determining the total cost by using the AASHTO thickness :
Layer
Cost of
Material
(RM/ton)
Required
Density
(ton/m³)
No.
of
Lane
Lane
Width
(m)
Road
Length
(m)
Thickness
(m)
Construction
cost (m²)
Project Cost
(RM)
SMA
330.00
2.35
6
3.7
25000
0.1397
15.50
68'729'729
Base
22.00
2.25
6
3.7
25000
0.2032
15.50
14'184'912
Subbase
15.00
2.3
6
3.7
25000
0.2921
15.50
14'195'485
Total =
97'110'126
RM
The above table is indicated that the sum of cost will be more than 97 million RM which is
effected from the Stone Matric Asphalt layer which is more than 68 million RM.
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22. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
Determining the total cost by using the JKR method and thickness :
Layer
Cost of
Material
(RM/ton)
Required
Density
(ton/m³)
No.
of
Lane
Lane
Width
(m)
Road
Length
(m)
Thickness
(m)
Construction
cost (m²)
Project Cost
(RM)
SMA
330.00
2.35
6
3.7
25000
0.15
15.50
73'162'875
Base
22.00
2.25
6
3.7
25000
0.18
15.50
13'547'550
Subbase
15.00
2.3
6
3.7
25000
0.18
15.50
12'049'050
Total =
98'759'475
RM
The above table is indicated that the sum of cost will be more than 98 million RM which is
affected from the Stone Matric Asphalt layer which is more than 73million RM.
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23. ASSIGNMENT FLEXIBLE PAVEMENT DESIGN
ECV 5606
Saeed Badeli
RECOMMENDATIONS :
The above tables is indicated the different cost for constructing the roadway.
The first table shows that the cost of AASHTO method is more than 108 million RM with
0.1651 m asphalt layer thickness.
The second table shows that the cost of using the JKR method of design is more than 101
million RM with 0.158 m asphalt layer thickness.
The JKR method gives a higher cost than the AASHTO .
The layer thickness of AASHTO method is thinner compare to the JKR method.
So the AASHTO method in this case is cost-effectiveness than the JKR method so the
authorities should use the AASHTO method . Many project in the U.S.A and many other
countries design by AASHTO method.
The most important factor that effects the cost is the asphalt thickness
We require to have a minimum thickness of asphalt layer for have a cost-effective design so
try to use the minimum thickness and finding the base and subbase based on the minimum
thickness of asphalt layer.
Maximize crushed stone thickness and sand subbase thickness – minimize AC thickness Can
also stabilize base to use less HMA
Use gravel only for fill or frost
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