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

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0

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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