mix design: changing the recipe book · dave newcomb and fujie zhou texas a&m transportation...

March 22-24, 2016 | Nashville, TN | www.worldofasphalt.com

Mix Design: Changing the

Recipe Book

DAVE NEWCOMB AND FUJIE ZHOU

TEXAS A&M TRANSPORTATION INSTITUTE

How have asphalt materials changed?

• 1901 – 2000 Age of Uncomplicated

– Almost all unmodified asphalt

– Recycling in 1970s – 90s: Low amounts of RAP

– Almost all dense-graded mixes

– Marshall and Hveem become displaced

– Volumetric design works OK

Recycled as Roads

How have asphalt materials changed?

• 2000 – 2016 – PG System in full swing

– Refineries change – asphalt gets expensive

– Warm mix

– PPA to make high PG

– REOB to make low PG

– Polymers

– More RAP and RAS

– Smaller NMAS

– SMAs

Refinery Changes

• ROSE (Residuum Oil Supercritical Extraction)

• Cokers

• More terminal blenders

REOB and PPA

• Recycled Engine Oil Bottoms (Steve Escobar)

– Most common additive

– High flash point, high visc. index, low wt. loss, low visc., etc.

– Also paraffinic

• Polyphosphoric Acid (TRB Circular E-C160)

– Commonly used additive

– High visc., no free H2O, does not oxidize asphalt or lower m-value

– May react with anti-strip

• Both are dependent upon asphalt chemistry!

What Does This Mean?

Asphaltenes Aromatics Resins Saturates

Asphalt

Most Reactive Least Reactive

RAP and RAS

• Resource Conservation

• Energy Conservation

• Price Stabilization

Greenhouse Gases

• Pavement construction very low compared to vehicle operations – 82 MT for pavements out of 1600 MT

for all transportation

• Using RAP/RAS reduces CO2e about the same amount as removing 270,000 vehicles

3/17/2015 WOA High Binder Replacement Webinar 8

Cost Savings

Reference Material Cost Savings

Zhou et al. (2006) 5% RAS 2 – 5%

Brock (2008) 20% RAP

50% RAP

>16%

>40%

NCAT (Willis et al.,

2012)*

25% RAP

50% RAP

14 – 20%

29 – 35%

3/17/2015 WOA High Binder Replacement Webinar 9

* Used different amounts and stiffness of virgin binders used in mixtures.

RAP/RAS and PG

RAP/RAS binder too stiff?

The Need

• Volumetric Mix Design – Does it make sense when our materials have changed so much?

• Balanced Mix Design

– Max. set by AC for 98% density

– Max. AC set by rutting test (must be less than 98% density)

– Min. AC set by cracking test

– Optimum is between max. AC and min. AC

November 2015 NCHRP 9-57

Balanced Mix Design


Rutting Tests

• Asphalt Pavement Analyzer

• Hamburg Wheel Track Test


• Decrease design air void

0

2

4

6

8

10

12

14

16

TOAS-E MWAS-C

HWTT

Rut

Dep

th @

1000

0 Pa

sses

(m

m)

Impact of Decreasing Design Air Voids on Rutting/Moisture Damage

5.2% AC with 3.0% air voids


0

10

20

30

40

50

60

70

80

90

TOAS-E MWAS-C

OT

Cycl

es

Impact of Decreasing Design Air Voids on Cracking



5.2% AC with 3.0% air voids 5.7%AC with 2.3% air voids

TOAS-E MWAS-C

16

12

2

8

4

0 HW

TT R

ut

Dep

th @

10

00

Pa

sse

s (m

m)

30

0

90

TOAS-E MWAS-C

60

OT

Cyc

les

Impact of Decreasing Design Air Voids on Rutting/Moisture Damage

Impact of Decreasing Design Air Voids on Cracking

Approaches for Improving Cracking Resistance of RAS

Mixes

Types of Cracking


Thermal Reflection

Bottom-Up Fatigue

Top-Down Fatigue

Thermal Cracking

• Two types

– Cold Temperature Contraction

– Temperature Cycling Fatigue


Tem

p

Summer Fall Winter

Elko, NV October 2015

Reflection Cracking

• Due to movement of underlying material


Shrinkage from Temperature Change

or Hydration

Lack of Load Transfer

Bottom-Up Fatigue Cracking


Repeated loads cause bending with cracks starting at the bottom and propagating up. Usually occurs in thin pavements.

Top-Down Fatigue Cracking

• Aged pavements are stiffer at the top, and that starts the crack that propagates down very slowly.

• Usually occurs in thick pavements


Stiffness Aging

9-57 Project Objectives

• Identify cracking tests for thermal, reflection, T-D fatigue, B-U fatigue – Literature review

– State survey

– Workshop • Develop experimental design for field validation

– Experimental design

– Plans for sampling, storing, shipping and testing materials

– Estimated schedule and budget

• Develop plans for laboratory evaluation – Precision and Bias

– Ruggedness


Cracking Tests Workshop

• Goals

– Select cracking tests for 4 cracking types

– Identify potential field/APT test sections

• What we prepared for the workshop:

– Interim report

– Cracking test webinars

– Cracking test booklet

– 9 cracking test videos


Interim Report


Low-temp. Reflection Bottom-up Top-down

DCT (D7313-13) Texas OT (Tex 248-F)

Beam fatigue ( T321)

IDT (UF)

SCB (TP105) DCT (D7313-13) S-VECD (TP107) S-VECD (TP107)

IDT (T322) SCB (LTRC) RDT (TAMU) RDT (TAMU)

TSRST/UTSST (UNR)

SCB (LTRC) SCB (LTRC)

Texas OT (Tex 248-F)

Cracking Tests

Cracking types vs. tests


No. of cycles

Stra

in le

vel

1

Monotonic Very high strain

Overlay High strain

Fatigue Lower strain

Low

High


• IDT for low temperature cracking

• SCB at low temperature

• TSRST/UTSST

• DCT

• OT

• RDT

• S-VECD

• Bending beam fatigue

• SCB at intermediate temperature

9 Cracking Test Videos

Available at NCHRP 9-57 web page on TRB web site.

Cracking Test Videos

• DCT: https://www.youtube.com/watch?v=Ynsbs_M8gbk

• SCB at low temperature: https://www.youtube.com/watch?v=YW5E69iKAPA

• UTSST: https://www.youtube.com/watch?v=gDdHMhAhnTU

• IDT: https://www.youtube.com/watch?v=xycvHX0XoyA

• OT: https://www.youtube.com/watch?v=5Np6lGSPfLA

• SCB at int temp: https://www.youtube.com/watch?v=vd-rdQCW2Pk

• BBF: https://www.youtube.com/watch?v=3V0SW0vQ8mY

• S-VECD: https://www.youtube.com/watch?v=9sGb2lkYb8I

• RDT: https://www.youtube.com/watch?v=_1Avh5nMV-g


https://www.youtube.com/watch?v=Ynsbs_M8gbk

https://www.youtube.com/watch?v=YW5E69iKAPA

https://www.youtube.com/watch?v=gDdHMhAhnTU

https://www.youtube.com/watch?v=xycvHX0XoyA

https://www.youtube.com/watch?v=5Np6lGSPfLA

https://www.youtube.com/watch?v=vd-rdQCW2Pk




https://www.youtube.com/watch?v=3V0SW0vQ8mY

https://www.youtube.com/watch?v=9sGb2lkYb8I

https://www.youtube.com/watch?v=_1Avh5nMV-g




• A quick reference

• Discussion guide

– Test simplicity • Training, spec. prep., instru.

testing, analysis, interpretation

– Test variability

– Test sensitivity

– Correlation to field performance

– Test equipment cost/availability

– State adoption

Cracking Tests Booklet

Available at NCHRP 9-57 web page on TRB web site.

Workshop Outcomes Items Thermal Cracking Reflection Cracking Bottom-up Fatigue

Cracking

Top-down Fatigue

Cracking

Selected cracking

tests

1. DCT

2. SCB-IL

3. SCB at low temp.

1. OT

2. SCB at

intermediate

temp.

3. BBF

1. BBF

2. SCB at

intermediate

temp.

1. SCB at

intermediate

temp.

2. IDT-UF

Key factors for

designing field

experimental test

sections

1. Climate (temperature, moisture, solar radiation); 2. Traffic; 3. Pavement structure and subgrade;

4. Asphalt mixtures; 5. Existing pavement conditions for reflection cracking.

Potential field test

sections

1. LTPP; 2. SPS10; 3. MnRoad; 4. NCAT Test Track; 5. Test sections under NCHRP 9-55, 9-58, and 9-

59.


Selected Cracking Tests

• Disc Compact Tension (DCT)

• Semi-Circular Bending (SCB)

– University of Minnesota – Low Temperature

– Louisiana Transp. Research Center – Intermed. Temp

– University of Illinois – Intermed. Temp

• Overlay Tester (OT)

• Indirect Tension Test (IDT)

• Bending Beam Fatigue (BBF)


What’s Measured?


Load

Crack Opening

Fracture Energy

Stra

in

Time

Stre

ss

Strain

Tensile Strength

Cre

ep

Co

mp

lian

ce

Time

Creep Compliance

DCT SCB

BBF OT

IDT +

Number of Cycles

Disk Compact Tension (DCT) • Low Temp. Cracking • ASTM D7313 • Fracture Energy • Relatively Simple

– Training – Sample Prep – 4 cuts, 2 holes – Instrumentation – Quick – Analysis

• Low Variability • Correlated to Thermal Cracking at Mn/ROAD • Cost ~ $49,000 • State Adoption: MN and WI. Under review in CO, SD, MT


DCT Video


Semi-Circular Bend (SCB) • Thermal, Reflection, Bottom-Up, Top-Down • AASHTO TP105 • Fracture Energy • Relatively Simple

– Training – Sample Prep – 4 cuts – Instrumentation – ~30 min – Analysis

• Medium Variability • Correlated to Thermal Cracking at Mn/ROAD • Cost ~ $52,000 • State Adoption:

– Low Temp: Under Review by UT, SD, PA, MT – Intermed Temp: LA, WI. Under Review by OK, NM. IL adopting mod version.


SCB Low Temp Video


SCB Intermediate Temp Video


Overlay Tester (OT) • Reflection, Bottom-Up Fatigue • Tex-248-F • No. Cycles to Failure • Relatively Simple

– Training – Sample Prep – 4 cuts, plate mount – No Instrumentation – 30 – 120 min. – Analysis

• High Variability • Correlated to Refl. Cracking in TX, NJ, CA. Fatigue Cracking at ALF, NCAT • Cost ~ $46,000 • State Adoption: TX and NJ. Under review in NV, FL, OH, MT


OT Video


Bending Beam Fatigue (BBF) • Bottom-Up Fatigue • AASHTO T321 • No. Cycles to Failure or 50% Modulus Reduction • Relatively Simple

– Med. Training – Sample Prep – 4 cuts – Instrumentation – Hours to days – Analysis

• Very High Variability • Correlated to Bottom-Up Cracking • Cost could be > $100,000 • State Adoption: CA for Long-life asphalt. Under

review in NV and GA


BBF Video


Indirect Tension (IDT) • Thermal Cracking • AASHTO T322 • Creep Compliance/Tensile Strength • Relatively Simple

– Med Training – Sample Prep – 2 cuts – Instrumentation can be complex – 4-6 hrs – Analysis

• Low Variability • Correlated to Thermal Cracking in SHRP and MEPDG • Cost can be > $100,000 (hydraulic test machine)


IDT Video


Laboratory Evaluation

• Review Existing Information and Studies

– SCB ILS

– Asphalt Institute

– NCAT

• Available Test Equipment

• Ruggedness Testing

• Precision and Bias


Ruggedness Testing

• Purpose: Identify factors that influence test results and determine how closely they must be controlled.

• Sensitivity test on variables instead of materials.

• Example: SCB

– Specimen thickness

– Loading rate

– Test temperature

– Notch depth

– Air voids


Interlaboratory Study

• Purpose: Determine repeatability and reproducibility of test method.

– Repeatability – single operator

– Reproducibility – multiple laboratories

• Test familiarization is important

• Test specimens from one laboratory

– Virgin DGA with 19 mm NMAS

– Virgin DGA with 9.5 mm NMAS

– DGA with high binder replacement


Field Validation Experimental Design

• Objective:

– Validate Cracking Tests

– Not Study Cracking Mechanisms

• Want to make sure cracking test differentiates mixes that will crack from those that will not.


Field Validation Experimental Design

• Consider Factors

– Pavement Structure

– Climate

– Traffic

– Mix Types

– Binders

• Existing Facilities vs. New Sections


Available Facilities and Characteristics

Items APT Full-scale test tracks Full-scale Test Roads In-service Pavements

Examples FHWA-ALF, Louisiana-LAF, CalTrans-HVS, Florida-HVS, Illinois-ATLAS, TxDOT-APT

WesTrack NCAT test track

MnRoad LTPP-GPS/SPS sections and state DOT sections NCHRP Sections

Traffic load Known traffic; well controlled traffic; often overloaded

Known traffic; WesTrack: 4 units of tractor/ trailer –triple combinations NCAT Track: four fully loaded trucks

Known traffic; Real traffic

Unknown traffic (most of time); Real traffic; many SPS sections equipped with WIMs

Traffic speed Slow; around 5-12 mph

Around 40-45 mph Real traffic and real speed (around 60 mph)

Real traffic and real speed (around 60 mph)

Test period Several months one-three years 4 years Several years to more than 15 years

Environment Temperature is often controlled

Natural weather Natural weather Natural weather

Aging effect Artificial aging can be considered, but not natural aging

Impact of short-term aging on performance is considered.

Impact of short/medium-term aging is considered

Impact of long-term aging is addressed


Texas Example

Balanced RAP/RAS Mix Design for Project- Specific Service Conditions

Introduction

• Benefit of RAP/RAS

– Economics • Saving aggregates • Saving asphalt binder

– Reducing rutting

– Environment • Reducing demands of non-renewable resources • Reducing landfill space demands

• RAP/RAS must be used!

• No.1 concern- variability

– Binder grade variation

– Binder content variation

– Aggregate gradation

• Solution:

– Best practices for RAP/RAS processing and stockpile management

Well Separated RAP Multiple sources RAP

Limitations of current design methods for RAP/RAS mixes

Feature of RAP/RAS mixes: Unknown VMA (VBE) – Don’t know how RAP/RAS blends with virgin binder.

• Need a mechanical test to assure cracking resistance.

Virgin RAP/RAS

Balanced RAP/RAS mix design for project specific condition

• Current mix designs not suitable for RAP/RAS design

– Need to assure rutting resistance

– Need to assure cracking resistance

– Need volumetric-air voids for QC

– Need project-specific rutting and cracking requirements • Traffic

• Climate

• Structure

RAP/RAS field test sections and performance

• Amarillo-Overlay: (Aug 2009) • IH40: Heavy traffic; Cold weather; Soft binder

• RAP: 0, 20, 35%

• Pharr district-New Const.: (April 2010) • FM1017: low traffic; Hot weather; stiff binder

• RAP: 0, 20, 35%

• Laredo-Overlay: SH359, 20%RAP (Mar. 2010)

• Houston-New Const.:SH146, 15%RAP/5%RAS (Oct. 2010)

• Fort Worth-AC/CRCP: Loop 820 (July 2012)

RAP/RAS field test sections and performance

Test sections Highway Overlay/

new const.

Weather Traffic

MESAL

OT cycles Performance

Amarillo

0%RAP

IH40 (severely

cracked thick

asphalt pavement)

4 inch/

overlay Cold 30

95 3 yrs: 100% refl.

cracking 20%RAP 103

35%RAP 200 3 yrs: 57% refl.

cracking

Pharr

0%RAP

FM1017-Very

good support

1.5 inch/

new const. Very hot 0.8

28 3yrs: overall -

good conditions 20%RAP 6

35%RAP 7

Laredo 20%RAP SH359-regular

support

3 inch/

overlay Very hot 1.5 3

3yrs: No cracking

Houston 15%RAP/5

%RAS

SH146-Very good

support

2 inch/new

const. hot 3.0 3

2.5yrs: No cracking

Dalhart 5%RAS US87 3 inch/

Overlay Cold 3.0 48/96

96 cycles-20%

RCR; 48 cycles-

50%RCR

RAP/RAS field test sections and performance 1. RAP/RAS mixes perform well at certain locations.

2. One OT requirement cannot fit for all.

3. Successful use of RAP/RAS mixes depends on • Weather/Traffic

• AC overlay

– Overlay thickness, Existing pavement structure (AC/AC; AC/PCC)

– Existing pavement conditions

• New construction

– Pavement structure and which layer (surface, base, etc.)

4. Design the mix for project-specific conditions

Balanced RAP/RAS mix design for project specific condition

Cracking Rutting

Mix Design

Balanced RAP/RAS Mix Design

• Hamburg test for rutting/moisture damage

• Overlay test for cracking OT requirement determined by Overlay program

• Max. density-98% for controlling potential bleeding

Existing pavement conditions (crack severity level,

LTE) if asphalt overlays

Climate Traffic Pavement structure

Yes

No

Raw aggregates Virgin binder

RAS (/RAP) WMA additive

Mixing temperature and time

Conditioning temperature and time

SGC(Ndesign)

Compactability/ workability Volumetric properties

Select at least 2 asphalt contents

Rutting/moisture damage:

Hamburg wheel tracking test

S-TxACOL

Predicted cracking development

Mix

ture

engin

eeri

ng

pro

per

ties

at se

lect

ed

asphal

t co

nte

nts

Cracking:

Overlay test

Meet requirements

Balanced mix for project-specific conditions

Balanced RAP/RAS Mix Design for Project-Specific Conditions

Determination of Min. OT cycles

Required main inputs: 1. OT cycles 2. Existing pavement conditions

Simplified Overlay design system

0

12

24

36

48

60

72

0 50 100 150 200 250 300 350

Ove

rlay

Life

(mon

ths)

OT Cycles

2" Overlay over 10" JPCPunder 3 MESALs/20 Years

165

Demonstration of project-specific OT requirement

• AC overlay scenarios – AC/PCC

– AC/AC/CTB

– AC/AC/granular base

• Traffic level: 3 MESAL – SH/US: 3-5 MESAL

• Weather: – Amarillo

– Austin

– McAllen

Demonstration of project-specific OT requirement • Amarillo

Demonstration of project-specific OT requirement • Austin

Demonstration of project-specific OT requirement • McAllen

Approaches for Improving RAP/RAS Mix Cracking Performance

• Available approaches

– Increase virgin AC (higher density)

– Soft, modified binders: PG64-28, PG64-34, PG58-34

– Decrease air voids

– Rejuvenators

Summary and Conclusions

• RAP/RAS mixes can have same or better performance with proper design.

• Balanced RAP/RAS mix design for project-specific conditions is recommended for use.

– Hamburg test for rutting/moisture damage

– OT for cracking; Project-specific OT requirement

– Max. density to control potential bleeding

• Different approaches are available for improving RAP/RAS mix performance if needed.

0

12

24

36

48

60

72

0 50 100 150 200 250 300 350

Ove

rlay

Life

(mon

ths)

OT Cycles

2" Overlay over 10" JPCPunder 3 MESALs/20 Years

What do We do with This?


BalancedMix Design

Opt. AC

Set Volumetrics

Table 11 Operational Tolerances

Description Test Method Allowable Difference Between Trial Batch and JMF1 Target

Allowable Difference from Current JMF Target

Individual % retained for #8 sieve and larger Tex-200-F

or Tex-236-F

Must be within master grading limits

in Table 8

±6.01

Individual % retained for sieves smaller than #8 and larger than #200

±4.01

% passing the #200 sieve ±2.01

Asphalt binder content, % Tex-236-F ±0.5 ±0.5

Laboratory-molded density, % Tex-207-F ±1.0 ±1.5 VMA, %, min Tex-204-F Note2 Note2

1. When within these tolerances, mixture production gradations may fall outside the master grading limits; however, the % passing the

#200 will be considered out of tolerance when outside the master grading limits. 2. Mixture is required to meet Table 8 requirements.

QC Volumetrics

QA Volumetrics QA Performance

Testing

Some Day

Set Tolerances

www.asphalttechnology.org/membership November 2015 NCHRP 9-57

At the 2016 AAPT Meeting:

Leading Edge Workshop: Cracking Tests

5 Presentations on Cracking Tests

Symposium: Balanced Mix Design

5 Presentations on High RAP/RAS

Implementation of Specifications

Aging Behavior

Forum Topic: World Asphalt Market


March 22-24, 2016 | Nashville, TN | www.worldofasphalt.com

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mix design: changing the recipe book · dave newcomb and fujie zhou texas a&m transportation...

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