By: Asst. Prof. Imran Hafeez
Contents
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Ancient Roads (5000 years ago)
Modern Roads (17th & 18th Centuries)
Evolution Of Pavement Design Methodology
Modern Trends in Design
Mechanistic- Empirical Design methods
Pavement performance prediction models
Super-pave & Perpetual pavements
concepts
Pavement Performance Tests/Equipments
Engr. Imran Hafeez
Concept of Ancient Roads
(5000 years ago)
Definition: “Paths treaded by animals and
human beings”
Pavement Structure:
 Stone –paved roads made of one or two rows of
slabs 50 mm thick in central portion….,
Roman Roads
Types of Roman Roads
 Ordinary roman roads
 Important Roman roads
 Built in straight line regardless of gradient
 Excavated parallel trenches 40-ft apart for
longitudinal drainage
 Foundation raised 3-ft above ground level
 Embankment covered with sand or mortar
CROSS-SECTION
(Ordinary Roman Roads)
1) Foundation layer (10-24inch),composed of
large stones
2) Firm base 9-in thick made of broken
stones,pebbles, cement and sand
3) Nucleus layer about 12-in thick using concrete
made from gravel and coarse sand
4) Wearing surface of large stone slabs at least 6in deep
5) Total thickness varied from 3ft to 6ft
Ordinary
Roman
roads
CROSS-SECTION
(Important Roman Roads)
 Bottom coarse(25-40cm) made of large
size broken stones in lime mortar
 Base coarse(25-40cm) made with smaller
broken stones in lime mortar
 Wearing coarse(10-15cm) of dressed
large stone blocks/slabs set in lime
mortar
 Total thickness varied 0.75 to 1.20 m
 Heavily crowned central carriage way
15ft wide(total width 35ft)
Important
Roman
roads
17th and 18th centuries.
MODERN ROADS
(17th & 18th Centuries)
TRESAGUET ROAD (1775)
CROSS-SECTION
TRESAGUET ROAD (1775)
 The subgrade was prepared in level
 Layer of large foundation stone with large kerb
stones at edges
 Base coarse about 8cm of compacted small broken
stones
 Top wearing coarse 5cm at edges,thickness
increased towards center for providing surface
drainage
 Sloping shoulders with side drain
 Total thickness about 30cm
MODERN ROADS
(17th & 18th Century)
TELFORD ROAD (1803)
CROSS-SECTION
TELFORD ROAD (1803)
 Level subgrade
 Large foundation stones of thickness 17-22cm
 Two layers of angular broken stones compacted
thickness of 10-15cm
 Lime mortar concrete instead of kerb stones at
pavement edges
 Top wearing coarse of 4cm thick gravel as
binding layer
MODERN ROADS
(17th & 18th Century)
MACADAM ROAD (1827)
CROSS-SECTION
TELFORD ROAD (1803)
 The subgrade is compacted with cross
slope
 Sub-base of broken stone 5cm size were
compacted to uniform thickness of 10 cm
 Base coarse of strong broken stone 3.75cm
size compacted to 10cm uniform thickness
 Top layer of stone 2cm size compacted to
thickness of about 5cm
 Total thickness approximately 25cm
(20th Century)
EVOLUTION OF PAVEMENT DESIGN
METHODOLOGY
 Pavement design :
1) Mix design of material
2) Thickness design of structural layers
 Pavement design philosophy:
1) Empirical
2) Mechanistic ( Theoretical , Analytical, Structural)
3) Mechanistic-Empirical
Design Approaches
Road Note 29 (TRRL, UK 1960, 1970,
Empirical)
Road Note 31
The Asphalt Institute Manual
Series
AASHTO Guide for Design of
Pavement Structures
ROAD NOTE 29
 A guide to the structural design of Pavements for
new roads …TRRL, UK 1960, 1970,
 Empirical Approach: study performance of
experimental sections built into in-service road
network
 Foundation soil CBR .. Upto 7 %
 Traffic.. Upto 100 Million Eq. Standard Axles
 Specification of material given in table-4
 Design life..20mm rutting or severe cracking
ROAD NOTE 29
 Performance data interpreted in light of structural
theory, mathematical modeling of pavement
behavior, simulative testing of road materials and
pavements
 The Structural Design of Bituminous Roads..
TRRL Laboratory Report 1132 published in 1984
 Structural design criteria:
1) Critical stress and strain
2) Permissible strains induced by standard 40 KN
wheel load at pavement temperature of 20o C
ROAD NOTE 31
 A guide to the structural design of bitumensurfaced roads in tropical and sub-tropical
countries ( Overseas Edition 1962,1966,1977)
 For traffic upto 30 msa in one direction, for >30
msa use TRRL 1132 with calibration to local
conditions
 subgrade strength by CBR method
 6 Sub-grade strength classes(2,4,7,14,29,30+)
 8 Traffic classes (0.3.0.7,1.5,3.0,6.0,10,17,30)
 Design charts for 8 type of road base/surfacing
material
THE ASPHALT INSTITUTE (MS-1)
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Thickness Design-Asphalt Pavements for Highways and
streets ( 1964,1981,1991)
Initially developed from data of AASHO Road test
Design charts in latest edition developed using DAMA
elastic –layered pavement analysis program that modeled
two stress strain conditions ( mechanistic based design
procedure uses empirical correlations)
Roadbed soil strength characterized by Mr
AC by Modulus of Elasticity and Poisson’s ratio
The design charts for 3 MAAT/ computer program for
full depth asphalt concrete or with emulsified base/
untreated aggregate base are given
AASHTO GUIDE FOR THE DESIGN OF
PAVEMENT STRUCTURES

Approach : study performance of trial sections
constructed to a wide range of overall thickness
round a close loop trafficked by repetitions of
known axle loads
 Developed empirical model by regression
analysis from data of ASSHO Road Test
 Interim guide 1961,1972, 1981
 ASSHTO Guide for the design of Pavement
Structures (1986,1993)
AASHTO GUIDE…………..contd.
 Performance period
 Analysis period
 Traffic ..Load
Equivalence Values
 Reliability
 Standard deviation
 Serviceability
 Roadbed soil resilient
modulus
 Resilient modulus for
unbound material
 Elastic model for
asphalt concrete
 Layer co-efficient
 Drainage
AASHTO GUIDE…………..contd.
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Log(W18)= Zr x So+9.36 log10 (SN+1)-0.20
+
Structural design model/equation
log10[ΔPSI/4.2-1.5]
0.40 + 1094
5.19
( SN+1)
+ 2.32x log10 ( Mr) – 8.07
SN = a1D1 + a2 D2 m2 + a3D3m3
PAVEMENT RESPONSES
Flexible Pavements
Given Wheel Load
150 psi
3 psi
Wearing C.
Base
Sub-base
Sub-grade
Load Distribution in Flexible Pavements
PAVEMENT RESPONSES
 Load related responses:
1) Vertical ( compressive)stresses and strains
2) Shear stresses and strain
3) Radial ( compressive or tensile) stresses and
strain
 Temperature induced responses:
1) Shrinkage stresses and strains ( temp:
cycling)
2) Low temperature cracking
3) Thermal cracking
PAVEMENT RESPONSES
Critical responses:
1) horizontal tensile stress/strain at the bottom of
bound layers
2) Vertical compressive stress/strain at the top of
sub-grade
 Calculating responses:
1) Using equations
2) Graphical solutions
3) Elastic layer computer programs
i) CHEVRON ii) ELSYM5
iii) ILLI-PAVE iv) MICH-PAVE
PAVEMENT PERFORMANCE
PREDICTION MODELS
 Performance prediction models are also
called distress models or transfer functions
 Models relate structural responses to
pavement distress
1) Fatigue cracking Model
2) Rutting Model
3) Thermal cracking Model
PAVEMENT PERFORMANCE
PREDICTION MODELS
 Fatigue cracking Model
 Nf = f1( εt ) –f2 ( Es)-f3
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Nf =
Nf =
Nf =
Nf =
0.0796( εt ) –3.291 ( Es)-0.854
0.0685( εt ) –5.671 ( Es)-2.363
1.66x 10-10 ( εt ) –4.32
5.0 x 10-6 ( εt ) –3.0
(General form)
(A. Inst)
(Shell)
(TRRL)
(IDOT)
PAVEMENT PERFORMANCE
PREDICTION MODELS
 Rutting Model(subgrade strain model)
Nf = f4( εv ) –f5
Org
f4
Asp Inst
1.365 x 10-6
Shel
TRRL
1.94 x 10-7
6.18 x 10-8
(General form)
f5
Allowable Rut
Depth mm
4.44 13
7
4.00 13
3.95 10
PAVEMENT PERFORMANCE
PREDICTION MODELS
 Permanent deformation model
log εp = a + b (log N) or εp = A (N)b
a = Exp estb material/stress condition
parameter
A= antilog of “a”
b= 0.1---0.2
PAVEMENT PERFORMANCE
PREDICTION MODELS
 Asphalt concrete Rutting Model
log εp = Cv + C1(log N) +C2 (log N)+ C3 (log
N)
 Cv depends on temp and deviator stress
 C1, C2 are constants
 Sub-grade Rutting Model
log εp = Cv + C1(log N) +C2 (log N)+ C3 (log N)
 Cv depends on moisture and deviator stress
PAVEMENT PERFORMANCE
PREDICTION MODELS

Thermal Cracking Model
Low temperature cracking
2) Thermal fatigue cracking
3) Models like that Shahin-McCullough model
are quite complex , but examine both types of
cracking.
1)
SUPERPAVE

Superior Performing Asphalt Pavements
 New, comprehensive asphalt mix design and
analysis system (SHRP 1987-1993) using SPGC
 Development of Performance based AC specs
(PG Grading) to relate lab Volumetric analysis
with field performance
 Four basic steps for Superpave asphalt mix
design
1)Material selection
2)Selection of design aggregate structure
3) Selection of design asphalt binder content
4) Evaluation of mixture for moisture sensitivity
Aggregate Properties
 Aggregate crushing value
(ACV)
 Ten percent fine value
(TFV)
 Aggregate Impact value
(AIV)
 Toughness Index (TI)
 Loss Angles Abrasion
value (LAA)
 Polish Stone Value (PSV)
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Soundness value
Sand equivalent
Specific gravity (Gsb)
Porosity
Flakiness Index (FI)
Elongation Index (EI)
Binder Properties
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Softening Point
Ductility
Flash & Fire Point
Penetration
Viscosity
Specific gravities
 Polar Molecular structure
 Elastomeric /Plastomeric
Stiffness
 Shear modulus
 Phase angle
 Accumulated strain
 Strip off value
SUPERPAVE

Binder tests:
1) Rolling Thin Film Oven ( RTFO) Test.. Aging
during mixing
2) Pressure Aging Vessel… in-service aging
3) Rotational Viscometer… viscosity
4) Dynamic shear Rheometer… visco-elastic
property
5) Bending beam Rheometer….stiffness at low
temp
6) Direct tension tester…. Low temp tensile
strain
PERPETUAL PAVEMENTS
 Long lasting(50yrs or more)
asphalt pavements
 Full depth asphalt pavement
constructed since1960s
 Need periodic surface renewal
 Pavements distress confined to
top layer
 The removed upper layer can
be recycled
 Mechanistic-based
design,material
selection,mixture
design,performance testing,life
cycle cost analysis
PERPETUAL PAVEMENTS
 HMA Base layer
 Fatigued resistant
layer
 No bottom up
cracking
 Intermediate layer
 Stable and durable
 Wearing coarse
resistant to surface
cracking and rutting
Pavement Performance Tests
The Performance based tests can be
classified as:
1)
2)
3)
4)
5)
6)
7)
8)
Dia-metral tests,
Uni-axial tests,
Tri-axial tests,
Shear tests,
Empirical tests,
Simulative tests.
Moisture Susceptibility tests.
Friction tests.
1.Diametral tests
a)
b)
c)
d)
Creep tests,
Repeated load
permanent deformation,
Dynamic modulus,
Strength test.
2.Uniaxial Creep Test
3.Triaxial Creep Test
a) Uniaxial and Triaxial
Repeated Load Tests
b) Uniaxial and Triaxial
Dynamic
Modulus
Tests
4.Shear Tests
a) SST Repeated Shear at
Constant Height Test
b) Shear Dynamic Modulus
c) Direct Shear Dynamic
Modulus
d) Direct Shear Strength Test
5.Empirical Test
a Marshall Stability and flow,
b Hveem stability,
c GTM, and
d Lateral pressure indicator
(LPI).
6.Simulative Tests
a
The
Asphalt
Pavement
Analyzer (APA) (Georgia
Loaded Wheel Tester)
b) Hamburg Wheel-Tracking
Device (HWTD)
c) Purdue
University
Laboratory Wheel Tracking
Device
a
Model
Mobile
Load
Simulator
b
Dry Wheel Tracker (Wessex
Engineering)
c
Rotary
Loaded
Wheel
Tester (Rutmeter) and
d French Rutting Tester (FRT)
7. Moisture Susceptibility Tests
8.
Friction Tests
State of the Art Equipment at TITE
 Triaxial Test system
 Universal Testing Machine
 Computerized Profilograph
 Benkelman Beam
 Dynamic Modulus of Fill
 Accelerated Polishing
machine
 Surface Friction Tester
 Universal Testing Machine
 Gyratory Compactor
 Wheel Tracker
Tri-axial Test system
Design to perform following tests
on Soil, aggregates and asphaltic
samples
 Modulus of Resilience of soil and
aggregates (Vacuum Triaxial test)
Four point beam fatigue test on
asphalt
Resistance to Permanent
Deformation
The repeated load Axial or Dynamic
Creep test
Controlled Fatigue Stress & strains
Computerized Profilograph
Measures the profile of the road surface
and display the results immediately on
screen in the form of roughness index.
Main Features:
Compact and lightweight
Battery operated
On screen graphics display
On screen display of Profile Index
Immediate results
Meets all ASTM standards
Easily setup and operated by one person
User friendly menu driven software
Transfer data to office PC for additional
analysis
Easily transported in a pickup or trailer
Bump Detection Warning System (BDWS)
Wheel Tracker
Wheel tracker is used to assess the
resistance to rutting of asphaltic
materials by simulating the in-site traffic
and environmental conditions.
Features:
Integral temperature controlled cabinet
Tracks for specified number of passes or
to specified rut depth
Double glazed doors for observation of
testing
Automatic test stop/start and speed control
A loaded wheel tracks a sample under
specified conditions of speed and
temperature
Development of the rut is monitored
continuously during the test
User friendly Windows software
Accelerated Polishing Machine
It gives a Polished Stone Value for aggregates
to be used in road surfaces and provides a
measure of the resistance to skidding.
Features:
Machine polishes samples of aggregates,
simulating actual road conditions
Meet the specifications of British standards &
ASTM
Predetermined revolution counter
Specimens manufactured and easily removed
from accurately machined moulds
Specimens located on ‘Road Wheel’ by rubber
rings and held by simple side fixing
Tired wheel easily removed for replacing tyres
Used abrasive and water collected in removable
tray
Loaded tire raised and lowered to the running
surface by mechanical lifting device