enhanced durability overall objective through increased ......3. higher density is achievable mix...

SEAUPG Annual Meeting‐Corpus Christi, TX 11/16/2016

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N O V E M B E R 1 6 , 2 0 1 6C O R P U S C H R I S T I , T E X A S

T I M A S C H E N B R E N E R , P . E .F H W A

S E N I O R A S P H A L T P A V E M E N T E N G I N E E RM A T E R I A L S A N D Q U A L I T Y A S S U R A N C E T E A M

O F F I C E O F A S S E T M A N A G E M E N T , P A V E M E N T S A N D C O N S T R U C T I O NL A K E W O O D , C O L O R A D O

Enhanced Durability Through Increased Density

Overall Objective

Ultimately,

achieving the in-place asphalt pavement density that results in the highest asphalt pavement performance.

Our Visit

1•The Importance of % Density

2•FHWA – AI Compaction Workshop

3•Field Demonstration Projects

4•Wrap Up

Compaction is Important

“A 1% decrease in air voids was estimated to:• improve fatigue

performance by 8.2 and 43.8%

• improve the rutting resistance by 7.3 to 66.3%

• extend the service life by conservatively 10%.”

NCAT Report 16‐02 (2016)

http://eng.auburn.edu/research/centers/ncat/files/technical‐reports/rep16‐02.pdf

Average Increase in Fatigue Life for1% Decrease in Air Voids

27.2%

15.1%

11.9%

9.2%

19.0%

8.7%

UCB 1969

UCB 1996

WesTrack 2002

AI 2010

TFHRC

Avg Field Avg Lab


2

Average Decrease in Rut Depth for1% Decrease in Air Voids

22.7%

10.0%

11.5%

9.6%

66.3%

7.3%

10.9%

WT f/f+

WT oc

WT rc

WT f/f+/c

WT rc

AI 2010

TFHRC

Avg Field Avg Lab

WT ‐ 2002 WesTrack

Reasons for CompactionReasons for Compaction

Cracking• To improve fatigue cracking resistance

• To improve thermal cracking resistance

Rutting• To minimize prevent further consolidation

• To provide shear strength and resistance to rutting

Moisture Damage• To ensure the mixture is waterproof (impermeable)

Aging• To minimize oxidation of the asphalt binder

Compaction is important, but not a cure‐all remedy

Our Visit

1•The Importance of % Density



4•Wrap Up

CA

AZ

CO

NM

TX

OKAR

LA

MO KY

AL GA

FL

VA

OH

MI

AK

MT

NV

ME

WA

OR

UT

KS

ID

WY

ND

SD

MN

NE

WI

IA

IL IN

MS

TN

SC

NC

WV

PA

NY

CTNJDEMD

DCHI

Key:

PRDemonstration projects (10) 10

Enhanced Durability of Asphalt Pavements through Increased In‐Place

Pavement Density

Workshop Only (15)

Workshop Outline

1 • Introduction

2 • Mixture Factors Effecting Compaction

3 • Compaction Best Practices

4 • Other Best Practices

5 • Measurement & Payment

6 • New Technologies

7 • Wrap Up11

Workshop• Feedback Very Positive

– Formal training– Comprehensive:

• Mix design to• Finish roller to• Measurement and Acceptance

– Back to the basics focus– Learned new topics

and reinforced others

• Workshops to Date– 10 locations– > 450 participants


3

Our Visit

1•The Importance of Density



4•Wrap Up

FHWA Demonstration ProjectField Project Results

• 8 of 10 projects to date

• Three Key Lessons:

1. Follow best practices

2. Inter‐relationship between:

3. Higher density is achievable

Mix Design

Field Density

AcceptanceField Verify

State #1Experiment Contractor’s Compactive Effort

Control 2 static rollers in echelon (≈10 passes each)

Test Section 1 Added 1 to 2 vibratory passes

Test Section 2 3 rollers – added pneumatic

State #1

Experiment DensityResults (%)

Change

Control 93.5 ‐‐‐

Test Section 1 93.2 Not significant

Test Section 2 95.4 + 1.9

Average of 10 core densities each / Reference is Gmm

• 2 static rollers achieved full incentive• Using vibratory mode resulted in no change in % density• Adding pneumatic increased % density

State #2Experiment Contractor’s Compactive EffortControl 10‐ton vibratory roller (8 passes)

4‐ton vibratory roller (7 passes)

Test Section 10‐ton vibratory roller (10 passes)4‐ton vibratory roller (7 passes)

State #2


Change


Test Section 92.5 ≈ + 1

Average of 6 cores each / Reference is Gmm

• Only 1 compaction roller needed to meet specification• Adding 2 passes increased % density


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How Is Acceptance Determined

24

4

23

0 10 20 30 40 50

PWL

Other advancedstatistics such as AAD

Simple averaging

Number of State Highway Agencies

How Is Acceptance Determined?

Asphalt Institute 2016

PennDOT Case Study

0

100

200

300

400

500

600

86 87 88 89 90 91 92 93 94 95 96 97 98 99

142

369

562

415

230

540 0 3 0 1130

3

4 0Number of Increments

In Tolerance Out of Tolerance

2015Statewide Density Wearing & BinderMinimum Individual Sublot

02

0

4

0

13

2 30 0 0 0

0

5

10

15

20

25

30

Number of State

Highway Agencies

Minimum Lot Average

Density (%)Asphalt Institute 2016

NYSDOT Case Study

22

2015 Avg. = 94.1S.D. = 0.83

Percent within Limits

PWL: Lower Specification Limit

Asphalt Institute 2016

Density (%)

State #3

Experiment Contractor’s Compactive EffortControl 4 rollers

‐ 2 vibratory in echelon (5 to 7 passes each)‐ 2 pneumatic in echelon (5 to 7 passes each)

Test Section 1 5 rollers – added 1 vibratory roller

Test Section 2 5 rollers – added 0.3% asphalt


5

State #3


Change


Test Section 1 92.9 No change


Average of 8 core densities each / Reference is Gmm

• 4 compaction rollers needed to meet specification• 1 additional roller did not change % density• Mix design adjustment resulted in % density increase

State #4Experiment Contractor’s Compactive EffortControl 2 vibratory rollers in echelon (5 passes each)

1 pneumatic roller (11 passes)

Test Section 1 Added 1 vibratory roller

Test Section 2 4 rollersAdded 0.3% asphalt

State #4


Change




Average of 12 nuclear gauge readings each / Reference is Gmm

• Control achieved maximum incentive• Additional roller did not change % density• Mix design adjustment resulted in % density increase

Selecting Optimum with Superpave

What Changes Were Made to AASHTO Standards?

• Gyrations

• Air Voids

• Voids in the Mineral Aggregate (VMA)

• Is There Additional Criteria?

Combination of Changes54% (14 of 26) Made 2 or More Changes

CA

AZ

CO

NM

TX

OK AR

LA

MOKY

AL GA

FL

VA

OH

MI

AK

MT

NV

MEWA

OR

UTKS

IDWY

ND

SD

MN

NE

WI

IA

IL IN

MS

TN

SC

NC

WV

PA

NY

CTNJDEMD

DCCA

HI

PR

2 of 4 Changes

3 of 4 Changes

1 of 4 Changes

Not a Superpave State

No Changes (Generally)

State #5

Experiment Contractor’s Compactive EffortControl ???

Test Section 1 4 rollers – 3 vibratory rollers in echelon1 vibratory on joint (4 vibratory & 1 static pass)


6

State #5


Change

Statewide Avg. 93.6 ‐‐‐


Test Section 1 96.1 +1.7

Average of 5 cores each / Reference is Gmm

• Implementing PWL specification• Control and test section both obtained maximum

incentive

State #6Experiment Contractor’s Compactive EffortControl 1 vibratory roller (9 passes)

1 pneumatic roller (14 to 18 passes)1 finish roller ( passes)

Test Section Same rollers and passesDecreased roller spacingIncreased pneumatic weight by 3 tons

State #6


n LSL PWL

Control 93.1 77 91.0 90.3

Test Section 93.0 11 92.0 93.3

Standard deviation changes from 1.58 to 0.67 / Reference is Gmm

• Additional effort by contractor was minimal• Uniformity improvements showed LSL could be 1% higher

Percent Within Limits

Percent Within LimitsFHWA Demonstration Project

Field Project Results

• 8 of 10 projects to date

• Key Lessons:1. Follow best practices

• 6 of 8 increased density from control

• 4 of 8 had equipment issues

2. Inter‐relationship between:• Mix design / Field mix verification / Density specification

• 2 of 8 had “dry” mixtures

3. Higher density is achievable:• Optimistically: higher density with best practices only (8 of 8)

• Pessimistically: higher density with additional roller (4 of 8)


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Our Visit

1•The Importance of Density



4•Wrap Up

Next Steps

• Summary report on 10 projects’ construction– Potential follow‐up on field performance

• Best practices communication– Summary document– Tech Brief– Additional training workshops (funding dependent)

• Potential to extend field experiment with more states– Dependent of funding– Dependent on state interest

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Thank youQ U E S T I O N S / C O M M E N T S :

T I M A S C H E N B R E N E R , P . E .F H W A

S E N I O R A S P H A L T P A V E M E N T E N G I N E E RM A T E R I A L S A N D Q U A L I T Y A S S U R A N C E T E A M

O F F I C E O F A S S E T M A N A G E M E N T , P A V E M E N T S A N D C O N S T R U C T I O N

L A K E W O O D , C O L O R A D O

( 7 2 0 ) 9 6 3 - 3 2 4 7T I M O T H Y . A S C H E N B R E N E R @ D O T . G O V

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enhanced durability overall objective through increased ......3. higher density is achievable mix...

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