By: Asst. Prof. Imran Hafeez

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By Asst. Prof. Imran Hafeez
MODERN TRENDS
IN
PAVEMENT DESIGN
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• Contents
• 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

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ANCIENTS ROADS
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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.,

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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

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CROSS-SECTION(Ordinary Roman Roads)

• Foundation layer (10-24inch),composed of large
  stones
• Firm base 9-in thick made of broken
  stones,pebbles, cement and sand
• Nucleus layer about 12-in thick using concrete
  made from gravel and coarse sand
• Wearing surface of large stone slabs at least
  6-in deep
• Total thickness varied from 3ft to 6ft

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Ordinary Roman roads
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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)

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Important Roman roads
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MODERN ROADS
17th and 18th centuries.
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MODERN ROADS(17th 18th Centuries)
TRESAGUET ROAD (1775)
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CROSS-SECTIONTRESAGUET 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

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TELFORD ROAD (1803)
MODERN ROADS(17th 18th Century)
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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

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MACADAM ROAD (1827)
MODERN ROADS(17th 18th Century)
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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

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(20th Century)
EVOLUTION
IN
PAVEMENT DESIGN
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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
  
  

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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

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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

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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

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ROAD NOTE 31

• A guide to the structural design of
  bitumen-surfaced roads in tropical and
  sub-tropical countries ( Overseas Edition
  1962,1966,1977)
• For traffic upto 30 msa in one direction, for gt30
  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

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THE ASPHALT INSTITUTE (MS-1)

• 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 Poissons
  ratio
• The design charts for 3 MAAT/ computer program
  for full depth asphalt concrete or with
  emulsified base/ untreated aggregate base are
  given

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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)

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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

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AASHTO GUIDE..contd.

• Log(W18) Zr x So9.36 log10 (SN1)-0.20
• Structural design model/equation
• log10?PSI/4.2-1.5
• 0.40 1094
  ( SN1) 5.19
• 2.32x log10 ( Mr) 8.07
• SN a1D1 a2 D2 m2 a3D3m3

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MODERN TRENDS
IN
DESIGN
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PAVEMENT RESPONSES
Flexible Pavements
150 psi
Wearing C.
Base
Sub-base
3 psi
Sub-grade
Load Distribution in Flexible Pavements
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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
• Shrinkage stresses and strains ( temp cycling)
• Low temperature cracking
• Thermal cracking

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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

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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

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PAVEMENT PERFORMANCE PREDICTION MODELS

• Fatigue cracking Model
• Nf f1( et ) f2 ( Es)-f3 (General
  form)
• Nf 0.0796( et ) 3.291 ( Es)-0.854 (A.
  Inst)
• Nf 0.0685( et ) 5.671 ( Es)-2.363 (Shell)
• Nf 1.66x 10-10 ( et ) 4.32 (TRRL)
• Nf 5.0 x 10-6 ( et ) 3.0 (IDOT)

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PAVEMENT PERFORMANCE PREDICTION MODELS

• Rutting Model(subgrade strain model)
• Nf f4( ev ) f5 (General form)

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PAVEMENT PERFORMANCE PREDICTION MODELS

• Permanent deformation model
• log ep a b (log N) or ep A (N)b
• a Exp estb material/stress condition parameter
• A antilog of a
• b 0.1---0.2

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PAVEMENT PERFORMANCE PREDICTION MODELS

• Asphalt concrete Rutting Model
• log ep 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 ep Cv C1(log N) C2 (log N) C3 (log
  N)
• Cv depends on moisture and deviator stress

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PAVEMENT PERFORMANCE PREDICTION MODELS

• Thermal Cracking Model
• Low temperature cracking
• Thermal fatigue cracking
• Models like that Shahin-McCullough model are
  quite complex , but examine both types of
  cracking.

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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

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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)

• Soundness value
• Sand equivalent
• Specific gravity (Gsb)
• Porosity
• Flakiness Index (FI)
• Elongation Index (EI)

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Binder Properties

• 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

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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

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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

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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

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Pavement Performance Tests
The Performance based tests can be classified
as 1) Dia-metral tests, 2) Uni-axial
tests, 3) Tri-axial tests, 4) Shear tests, 5)
Empirical tests, 6) Simulative tests. 7)
Moisture Susceptibility tests. 8) Friction
tests.
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1.Diametral tests a) Creep tests, b) Repeated
load permanent deformation, c) Dynamic
modulus, d) 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
• Marshall Stability and flow,
• 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
• Model Mobile Load Simulator
• Dry Wheel Tracker (Wessex Engineering)
• Rotary Loaded Wheel Tester (Rutmeter) and
• French Rutting Tester (FRT)
• 7. Moisture Susceptibility Tests
• 8. Friction Tests

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State of the Art Equipment at TITE
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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

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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)
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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

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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

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END