Pavement Research in California: Challenges and Results

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Pavement Research in California Challenges and
Results

• John Harvey
• Principal Investigator
• UC Pavement Research Center

Dynatest CSIR
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Outline

• Quieter Pavements
• Mechanistic-Empirical Pavement Design
• Reflection Cracking and Modified Binder Mixes
• Pavement Preservation
• Pre-Cast Concrete
• Urban freeway rehabilitation traffic delay
• Recycled Asphalt Pavement
• Pulverization
• Foamed asphalt
• Pay Factors for Hot Mix Asphalt
• Warm Mix Asphalt

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Challenge Quieter, Safer and More Durable
Surfaces

• Noise major public issue for highways
• Current solution is concrete sound walls
• Pavement surface choice can reduce pavement noise
  at critical frequencies
• Challenge
• Make quieter surfaces last longer
• Keep skid resistance benefits
• Get pavement preservation benefits

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Caltrans Quieter Pavement Research

• Asphalt and concrete pavement surfaces
• Improve On-Board Sound Intensity (OBSI)
• correlate to pass-by measurements
• Asphalt pavement program
• Performance evaluation of existing thin asphalt
  surfacings
• Development of improved surfacings
• Noise, skid resistance, ride quality, service life

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Status of Asphalt Pavement Work

• Completing 2 year evaluation of 80 field sections
• 57 with currently used surfacings
• 23 with experimental mixes
• 2007-2008 work
• Evaluate surfacings from outside California
• Develop new mix designs in lab
• Plan for field and HVS evaluations

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All data in relational databases tied to GPS
locations
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Instrumented car for highway speed work
Inertial profilometer High speed laser for
macrotexture Microphone for OBSI
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Laboratory work on cores from sites
Standard tests Impedancetube
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Findings

• Open graded mixes provide noise and permeability
  benefits that continue over 4-8 years
• Rubberized similar to non-rubberized
• RAC-G has initially lower noise than dense graded
  asphalt
• Due to higher initial air-voids
• Same as dense graded within 5 years
• Best choice at this timeopen graded with max
  aggregate 12.5 mm or less
• Size and connectivity of pores more important
  than total air-void content for noise

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Challenge More Economical Pavements through
Mechanistic-Empirical Pavement Design

• Mechanistic-Empirical Pavement Design Guide
  (MEPDG), national effort
• Version 1.0 delivered April, 2007
• Balloting by states in June, 2007
• Steps afterward still uncertain
• Caltrans is implementing ME design
• Use parts of MEPDG
• Develop new models where needed

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Mechanistic-Empirical Design

• UCPRC tasks for Caltrans
• Evaluation of MEPDG
• CalME software to fill flexible pavement gaps
• RadiCal spreadsheet for concrete pavement
  longitudinal cracking
• Prepare WIM databases
• Laboratory and field materials properties
  databases
• New back-calculation routine (CalBack)
• Climate region definition
• Training (later)

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Overall objective of CalME fill gaps in
models in MEPDG

• Gaps in MEPDG
• Calibrated for conventional binders
• Primary emphasis on new construction not
  rehabilitation
• Some models not mechanistic
• Difficult to calibrate with accelerated pavement
  testing
• Primary reliance on laboratory testing for moduli

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Addressing the Gaps

• CalME Rutting model
• Recursive mechanistic model calibrated with
  repeated shear test
• Calibrated with APT and test tracks
• Calibrated for modified and conventional
  overlays thin overlays
• CalME Reflection cracking model
• Recursive mechanistic model for traffic loading
• Calibrated with APT for modified and conventional
  overlays thin overlays

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Addressing the Gaps

• CalME Fatigue model
• Recursive analysis
• Equal calibration focus between laboratory and
  back-calculated moduli
• All damage equations share common format and
  operate off common relational database structure
• Monte Carlo simulation for reliability

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Accelerated Pavement TestingThin Rubber and
Modified Overlays

• Three experiments to date
• RAC-G vs conventional overlay, full and half
  thickness on cracked asphalt
• Polymer modified overlay on cracked PCC
• Gap-graded terminal blend rubber mixes vs
  conventional overlay and RAC-G on cracked asphalt
• Each tested at 20 C with overloading for
  cracking 55 C without overloads for rutting

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Terminal Blend Rubber Test Sections
45 or 90 mm Overlay 90 mm cracked asphalt 400 mm
gran base Clay subgrade
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HVS Rutting Test at 55 C 45mm Modified Binder
with 7 Rubber Overlay
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Predicted vs Measured Rutting at 55 C
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Rutting in Asphalt Layers at 55 C Surface
Temperature
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HVS Cracking test comparison with CalME recursive
updating of asphalt stiffness
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Simulated stiffness of layers during HVS test
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Are we capturing the magic of the rubber
binders?

• Propagation phase not captured by traditional
  fatigue relations to 50 loss of stiffness
• Alternative fatigue characterization being used
  in CalME that captures initiation and propagation

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50 Stiffness
Blue- dense graded conventional binderOther
colors- gap-graded with various rubberized
binders
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Findings

• CalME rutting and reflection cracking models work
  for thin modified/rubber overlays
• Rutting phenomenon in thin overlays needs further
  field comparisons
• Half-thickness RAC-G has same reflection cracking
  performance as conventional overlay
• Terminal blend rubberized overlays had better
  cracking performance than RAC-G
• Be careful with rutting in critical locations

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Licensing of CalME

• Owned by UC, a research organization not a
  business
• License being written for Caltrans
• Code Use Distribute ModifyOwn
• Object X X X
• Executable X X X
• Use use internally
• Distribute permit others to use it
• ModifyOwn make changes, creates a new product
  owned by the licensee (Caltrans) provide UC copy
  of new product

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Challenge Pavement Preservationand
Optimizing Available
Optimize Budgets
Life Cycle Cost Analysis
Performance Prediction
Construction quality
Materials details Pavement
structure Climate data Truck traffic
loading Surface condition and IRI on fixed
segments
Database
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Effect of Overlay Thickness on cracking life
from Bayesian models and WSDOT data

• 45 64 100 mm
• Overlay thickness

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Effect of existing alligator cracking on overlay
cracking life
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Effect of Rainfall and Freeze Thaw Cycles
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Overcoming lack of historical construction data
for use in PMS

• Investigation of use of Ground Penetrating Radar
  (GPR) at network level
• Asphalt, concrete and composite pavements
• GPR found to have sufficient accuracy
• Cost-effective method to baseline 80,000 lane-km
  in one year

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Pilot network
500 lane-km
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Example of GPR cross sections
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Thickness comparisons with cores
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Challenge Quick repairs for urban freeways

• HVS evaluation of pre-cast concrete slab
  replacement
• Dry and wet conditions
• Staged construction of dowel grouting

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Dowel grout
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Failure modesCorner cracksand pumping of
bedding material
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Pre-Cast Slabs Findings

• Pre-Cast Slabs exceeded design traffic
  requirements
• One week of traffic before grouting dowels
• Approximately 40 million E80s after dowel
  grouting
• Risk of erosion of bedding sand
• Contractor has revised specification
• District is looking for location to implement on
  freeway

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Challenge Optimizing design and construction
for urban freeway rehabilitation

• 50,000 to 250,000 ADT
• 5 to 15 heavy trucks
• 4 to 10 lane freeways
• 30 to 50 year old pavements
• Need to rehabilitate to 30 year design lives

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Analysis Solution CA4PRS software

• Calculates construction duration and traffic
  delay
• for different strategies pavement structures,
  traffic closures, and construction logistics
• Concrete, asphalt, composite
• Integrated analysis approach to balance and
  optimize competing objectives
• Longer lasting pavements
• Faster delivery of construction
• Tolerable traffic delays
• Within agency budget and scope

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Case Study on I-15 Devore Reconstruction Project
6 km Replace slab and base 130,000 ADT 15
trucks Completed in two 9-day closures
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I-15 Devore Pre-Construction Analysis with
CA4PRS Schedule-Traffic-Cost
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Challenge In-Place Recycling of Cracked Asphalt
Pavement

• Pulverization
• Foamed asphalt

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California Context

• Thick layers (150-300 mm) cracked asphalt
• Current practice thin overlays and digouts
• Pulverization
• Pulverize distressed asphalt then overlay
• Foamed asphalt
• Same except stabilized with foamed asphalt

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Objectives of Research

• Site selection guide
• Mix and structural design guides
• Construction guide

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Failure on foamed asphalt
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Underlying drainage problem Not foamed asphalt
problem
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Challenge Performance-Related Pay Factors for
Hot Mix Asphalt

• Alternative to Percent Within Limits
• Based on Life Cycle Cost Analysis
• Modeling of sensitivity of performance for
  rutting and fatigue to construction quality
• Compaction, binder content, thickness, gradation

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RAC-G w/Sasobit

• First round conventional DGAC control Sasobit
  EvoTherm Aspha-Min
• Second round (if authorized) RAC-G

HVS Test Plan in preparation
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Combined Pay Factors includes Rutting, Fatigue
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Challenge Warm Mix Asphalt

• Potential benefits
• Reduce energy use
• Reduce fumes
• Better compaction
• Potential risks
• Does WMA increase risk of rutting, water
  sensitivity, fatigue?
• Do all WMA products have similar performance?

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Reports downloadable at www.its.berkeley.edu/pave
mentresearch www.ucprc.ucdavis.edu after August 07