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Pavement Research in California: Challenges and Results
John HarveyPrincipal Investigator
UC Pavement Research Center
Dynatest CSIR
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
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
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
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
All data in relationaldatabases tied to GPS locations
Instrumented car for highway speed work
Inertial profilometer
High speed laser for macrotexture
Microphone for OBSI
Laboratory work on cores from sites
Standard tests
Impedancetube
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 time:open graded with max aggregate 12.5 mm or less– Size and connectivity of pores more important than
total air-void content for noise
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
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)
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
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
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
Accelerated Pavement Testing:Thin 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
Terminal Blend Rubber Test Sections
45 or 90 mm Overlay90 mm cracked asphalt400 mm gran baseClay subgrade
HVS Rutting Test at 55 C: 45mm Modified Binder with 7% Rubber Overlay
Predicted vs Measured Rutting at 55 C
Rutting in Asphalt Layers at 55 C Surface Temperature
HVS Cracking test comparison with CalMErecursive updating of asphalt stiffness
Simulated stiffness of layers during HVS test
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
-10
-8
-6
-4
-2
0
2
0 2 4 6 8 10 12 14 16 18Ln(n)
Ln(-l
n(SR
))
G9-DGAC-21B, AV = 5.61%, 699 microstrainG9-RACG-5A, AV = 6.41%, 698 microstrainG9-MAC15-9B, AV = 5.70%, 696 microstrainG9-MB15-26A, AV = 6.45%, 702 microstrainG9-MB4-32A, AV = 6.01%, 740 microstrain
Goal 9 FMLC
20C
SR = 0.1000
SR = 0.5000
SR = 0.9999
Blue- dense graded conventional binderOther colors- gap-graded with various rubberized binders
50% Stiffness
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
Licensing of CalME• Owned by UC, a research organization not a
business
• License being written for CaltransCode Use Distribute Modify&OwnObject X X XExecutable X X X
Use: use internallyDistribute: permit others to use itModify&Own: make changes, creates a new
product owned by the licensee (Caltrans); provide UC copy of new product
Challenge: Pavement
Preservationand Optimizing
$ Available
Database
Performance Prediction
Life CycleCost Analysis
OptimizeBudgets
Construction qualityMaterials details
Pavement structure Climate data
Truck traffic loadingSurface condition and IRI on fixed segments
Effect of Overlay Thickness on cracking life from Bayesian models and WSDOT data
0
200,000
400,000
600,000
800,000
1,000,000
1,200,000
1,400,000
0.00 0.09 0.15 0.21 0.33
Overlay thickness in ft
Expe
cted
Cum
ulat
ive
ESAL
s to
5%
cr
acki
ng baaa
27 45 64 100 mmOverlay thickness
Effect of existing alligator cracking on overlay cracking life
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
0.00 4.98 12.33 27.02
Percentage of existing alligator cracking
Exp
ecte
d Cu
mul
ativ
e ES
ALs
to 5
%
crac
king ba
aa
Effect of Rainfall and Freeze Thaw Cycles
0
100,000
200,000
300,000
400,000
500,000
600,000
0 22,192 45,278 68,363 91,448
Product of freeze thaw cycles and precipitation
Expe
cted
Cum
ulat
ive
ESAL
s to
5%
cr
acki
ng
baaa
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
Pilot network500 lane-km
Example of GPR cross sections
Thickness comparisons with cores
0
5
10
15
20
0 5 10 15 20
GPR Thickness (in)
Cor
e Th
ickn
ess
(in)
Layer 21:1 Line
0
5
10
15
20
0 5 10 15 20
GP R Thickness (in)
Cor
e Th
ickn
ess
(in)
Layer 11:1 Line
0
5
10
15
20
0 5 10 15 20
GPR Thickness (in )
Cor
e Th
ickn
ess
(in) Layer 3
1:1 Line
0
5
10
15
20
0 5 10 15 20
GPR Thickness (in )
Cor
e Th
ickn
ess
(in) Layer 4
1:1 Line
Challenge: Quick repairs for urban freeways
• HVS evaluation of pre-cast concrete slab replacement– Dry and wet conditions– Staged construction of dowel grouting
Dowel grout
Failure modes:Corner cracksand pumping of bedding material
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
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
Analysis Solution: CA4PRS software
• Calculates construction duration and trafficdelay– 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
Case Study on I-15 Devore Reconstruction Project
6 kmReplace slab and base130,000 ADT15% trucksCompleted in two 9-day closures
I-15 Devore Pre-Construction Analysiswith CA4PRS: Schedule-Traffic-Cost
TotalClosures
ClosureHours
UserDelay
AgencyCost
TotalCost
One RoadbedContinuous (24/7) 2 400 5.0 15.0 20.0 80
72-Hour WeekdayContinuous 8 512 5.0 16.0 21.0 50
55-Hour WeekendContinuous 10 550 10.0 17.0 27.0 80
10-Hour Night-timeClosures 220 2,200 7.0 21.0 28.0 30
Max.
Delay(Min)
Scenario
Schedule Cost Comparison ($M)PeakConstruction Comparison
Challenge: In-Place Recycling of Cracked Asphalt Pavement
• Pulverization
• Foamed asphalt
California ContextThick layers (150-300 mm) cracked asphalt Current practice: thin overlays and digouts
PulverizationPulverize distressed asphalt; then overlay
Foamed asphaltSame except stabilized with foamed asphalt
Objectives of Research
• Site selection guide • Mix and structural design guides• Construction guide
Failure on foamed asphalt
Underlying drainage problemNot foamed asphalt problem
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
RAC-G w/Sasobit®
• First round: conventional DGAC control; Sasobit; EvoTherm; Aspha-Min
• Second round (if authorized): RAC-G
HVS TestPlan inpreparation
Combined Pay Factors —includes Rutting, Fatigue
-50
-40
-30
-20
-10
0
10
20
30
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Combined RP
Com
bine
d Pa
y Fa
ctor
TY=20 TY=10
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?
Reports downloadable at:www.its.berkeley.edu/pavementresearch
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