Properties and Short- Term Laboratory Conditioning of...

Properties and Short-Term Laboratory Conditioning of Foamed Asphalt for WMA Applications 7 April 2016

Today’s Presenters

• Moderator Ed Harrigan, TRB/NCHRP

• Presenters Dr. David Newcomb, TTI

Dr. Fan Yin, TTI

Dr. Edith Arámbula Mercado, TTI

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DOT practitioners • Often become AASHTO

standards, specifications, guides, manuals

• Can be directly applied across the spectrum of highway activities: planning, design, materials, construction, maintenance, operations, safety

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program • Opportunity to interact with

NCHRP investigators, learn about research products, and foster implementation and adoption.

For More Information

http://www.trb.org/NCHRP

Christopher Hedges Manager, NCHRP

CHedges@nas.edu

TRB WEBINAR ON SHORT TERM CONDITIONING OF ASPHALT

MIXTURES AND PROPERTIES OF FOAMED ASPHALT MIXTURES

Dr. David Newcomb Dr. Fan Yin

Dr. Edith Arámbula Mercado

INTRODUCTION NCHRP 9-52 (Aging) – Dr. Yin Short Term Aging

Protocol Long Term Aging Protocol Factors Affecting Aging

NCHRP 9-53 (Foaming) – Dr. Arámbula Mercado Foaming for WMA Methods for Measuring

Foam Properties Factors Affecting

Foaming Effects of Foaming on

Mixture Behavior Laboratory vs. Field

SHORT-TERM LABORATORY

CONDITIONING OF ASPHALT MIXTURES

NCHRP Report 815

AGING OF ASPHALT MIXTURES

• Stiffening with time

• Short-term during production and construction

• Long-term throughout pavement service life

• Significant effect on mixture properties and pavement performance

Short-Term Conditioning

AGING OF ASPHALT MIXTURES • Laboratory aging protocols per AASHTO R 30 Mix design: STOA 2 hours at Tc Performance testing: STOA 4 hours at 275°F Field aging: LTOA 5 days at 185°F

• Mixture components and production parameters Use of polymer modifiers Inclusion of recycled materials Advent of WMA technologies DMP replacing BMP Increased production temperature

Aging Characteristics

OBJECTIVES

• Validate laboratory STOA protocol to simulate plant aging of asphalt mixtures (Task I)

• Correlate field aging of asphalt mixtures with laboratory LTOA protocols (Task II)

• Identify factors affecting the aging characteristics of asphalt mixtures (Task III)

FIELD PROJECTS

Connecticut Florida Indiana

Iowa New Mexico South Dakota

Texas (2) Wyoming

FIELD PROJECTS

Field Project WMA Production Temperature Plant Type RAP/RAS Aggregate

Absorption Binder Source

Texas I

Connecticut

Wyoming

South Dakota

New Mexico

Florida

Indiana

Texas II

LABORATORY TESTS • Resilient Modulus (MR) ASTM D 7369 MR Stiffness at 77°F/10Hz

• Dynamic Modulus (E*) AASHTO TP 79-13 E* Stiffness at 68°F/10Hz and E* Master Curve

• Hamburg Wheel Tracking Test (HWTT) AASHTO T 324 Rut Depth at 5,000 Load Cycles and Rutting Resistance

Parameter (RRP) at 122°F

Loading Pulse

Mixture Response

HWTT RRP DETERMINATION

0.0E+00

1.0E-01

2.0E-01

3.0E-01

4.0E-01

0 5000 10000 15000 20000 25000 30000

Load Cycle

Measured Rut Depth Predicted Rut Depth Viscoplastic Strain

Permanent Strain Stripping Strain

Stripping Number

LCSN LCST

VALIDATION OF STOA PROTOCOLS

vs. & PMPC

HMA Stabilize@275F

WMA Stabilize@240F

Volumetrics: Gmm & Pba Stiffness: MR & E*

Rutting Resistance: HWTT

Construction Core HMA

2h@275F

WMA 2h@240F

Lab < Plant

Lab > Plant

Lab = Plant

PMPC / Construction Core Property

Line of Equality

TASK 1

MIXTURE VOLUMETRICS FOR LMLC VS. PMPC

Theoretical Maximum Specific Gravity (Gmm)

2.3 2.4 2.5 2.6 2.7

LMLC - Gmm

TX I NM CT WY SD IA IN FL TX II

Percent of Absorbed Asphalt (%Pba)

0.0 0.6 1.2 1.8 2.4 3.0

LMLC - Pba(%)

Equivalent volumetrics for lab mix vs. plant mix STOA representative of asphalt absorption and aging during plant production

TASK 1

MR STIFFNESS at 25°C/10Hz

Equivalent MR stiffness for LMLC vs. PMPC Slightly lower MR stiffness for construction core vs. LMLC due to higher AV

LMLC vs. PMPC LMLC vs. Construction Core

0 1400 2800 4200 5600 7000

LMLC - MR (MPa)

0 1400 2800 4200 5600 7000C

LMLC - MR (MPa)

TASK 1

SUMMARY – VALIDATION OF STOA PROTOCOLS Validated laboratory STOA protocols of 2 hours at 275°F for HMA and 240°F for WMA to simulate plant aging • Volumetrics: LMLC = PMPC • E* stiffness: LMLC = PMPC • MR stiffness: LMLC = PMPC • Rutting resistance: LMLC = PMPC • Construction core vs. LMLC & PMPC Higher AV (9.0% vs. 7.0%) Use of plaster (degradation and debonding)

> construction core > construction core

TASK 1

QUANTIFICATION OF FIELD AGING

• Cumulative Degree-Days (CDD): sum of the daily high temperature above freezing for all the days from time of construction to the time of core sampling

Construction Season Geographic Location

Winter Oct. 2012

𝐶𝐶𝐶𝐶𝐶𝐶 = �(𝑇𝑇𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 − 32)

TASK 2

CDD CURVES

Dec-11 Jul-12 Jan-13 Aug-13 Mar-14 Sep-14 Apr-15

Coring Date

Texas New Mexico Wyoming South Dakota

Iowa Indiana Florida

TASK 2

MRR = 1.81 MRR = 2.23

PROPERTY RATIO (PR) • To quantify effect of aging on mixture properties

• Samples before aging Field cores at construction

LMLC specimens with only STOA

• Samples after aging post-construction field cores

LMLC specimens with STOA + LTOA

𝑃𝑃𝑃𝑃 =𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑎𝑎𝑎𝑎𝑃𝑃𝑃𝑃𝑃𝑃 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 𝑏𝑏𝑃𝑃𝑎𝑎𝑃𝑃𝑃𝑃𝑃𝑃 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴

TASK 2

CDD vs. PR (MR STIFFNESS)

TASK 2

FIELD AGING VS. LABORATORY LTOA – MR STIFFNESS

Field Project 2w@60C 5d@85C

Florida 1.22 1.38

Indiana 1.30 1.54

Iowa 1.32 1.65

New Mexico 1.89 2.21

South Dakota 1.58 1.95

Texas 1.60 1.94

Wyoming 1.44 1.80

Average 1.48 1.78

Stdev 0.23 0.28 2w@60C = 9,600 CDD (MR & HWTT RRP)

5d@85C = 17,500 CDD (MR & HWTT RRP)

TASK 2

SUMMARY – FIELD AGING VS. LTOA PROTOCOLS

• Proposed CDD to quantify field aging of asphalt pavements

• Proposed PR to evaluate mixture property evolution with field and laboratory aging

• Correlated field aging with laboratory LTOA protocols

LTOA Protocols CDD In-Service Time

Warmer Climates

Colder Climates

2 weeks at 140°F 9,600 7 months 12 months

5 days at 185°F 17,500 12 months 23 months

TASK 2

FACTOR ANALYSIS*

21 *STAT Validation by ANOVA Analysis

WMA Technology

Production Temperature

Plant Type

Recycled Materials

Aggregate Absorption

Binder Source

Control Mixture

Positive Effect

Negative Effect

Insignificant Effect

Short-term: mixture property Long-term: mixture property ratio

TASK 3

FACTOR – WMA TECHNOLOGY

Short-Term: MR Stiffness

0.0 1.0 2.0 3.0 4.0

HMA MR Ratio

TX NM WY SD IA IN FL

0 200 400 600 800 1000

HMA - MR (ksi)

TX I NM CT WY SD IA IN FL

Long-Term: MR Stiffness Ratio

TASK 3

FACTOR – PLANT TYPE

Short-Term: MR Stiffness Long-Term: MR Stiffness Ratio

0 200 400 600 800 1000

DMP Mixture - MR (ksi)

IN TX II

0.0 1.0 2.0 3.0 4.0

BMP Mixture MR Ratio

TASK 3

Factors Significant?

Trends Explanations ST* LT*

WMA Technology Yes Yes

WMA vs. HMA ST: worse properties

LT: faster aging

• Reduced production temperatures

• WMA additives

Recycled Materials Yes Yes

RAP/RAS vs. control ST: better properties

LT: slower aging

• Over aged binders • Less virgin binders

available for aging

Aggregate Absorption Yes Yes

High vs. low abs. ST: worse properties

LT: faster aging

• More effective binders available for aging

Binder Source Yes N/A Same PG ≠ same properties

• Different oxidation kinetics

Production Temperature No No

Equivalent mixture properties Plant Type No No

* ST = short-term; LT = long-term

FACTOR ANALYSIS SUMMARY

Laboratory STOA HMA: 2h@275°F WMA: 2h@240°F

Plant Production & Construction

Laboratory LTOA Field Aging

CDD = ∑(𝑇𝑇𝑑𝑑𝑑𝑑𝑑𝑑 − 32)

MR Stiffness Ratio (Aged/Unaged)

Volumetrics MR & E* Stiffness

HWTT Rutting Resistance

2w@140°F = 9,600 CDD 5d@185°F = 17,500 CDD

Novel HWTT Methodology

Mixture Property Ratio (Aged/Unaged)

WMA Technology

Recycled Materials

Aggregate Absorption

Binder Source

Production Temperature

Plant Type

Significant Effect on Aging Characteristics?

CONCLUSIONS Short-Term Conditioning

PROPERTIES OF FOAMED ASPHALT

FOR WMA APPLICATIONS

NCHRP Report 807

WARM-MIX ASPHALT • Additives or mechanical foaming process • Reduced production temperatures (~50°F)

Properties of Foamed Asphalt

Benefits

• Economic

• Environmental

• Performance

Limitations

• Susceptibility to rutting and moisture damage

• Correlation between laboratory and field performance

• Unknowns of the mechanical foaming process

WARM-MIX ASPHALT • Mechanical foaming accounted for ~84% of total

WMA produced in 2014 • Mechanical foaming mechanism

• Limitations Foaming measurements Foamed asphalt characteristics Foamed mixture properties Mix design procedure

Dipstick Method

Viscosity Reduction

Volume Expansion

Water injection into hot binder

OBJECTIVES

• Develop test methods and metrics to characterize

asphalt foaming.

• Evaluate the effects of foamed asphalt characteristics

on foamed mixture properties.

• Develop a mix design procedure for foamed asphalt

mixtures.

FOAMED ASPHALT MEASUREMENT METHODS

Laser Device

Camera

Container

Laboratory Foamer

LASER MEASUREMENT

Higher ERmax = higher instantaneous expansion Higher FI(t) = better stability

0 30 60 90 120 150

Time (s)

Fitted ER Measured ER Distance Reading

Foamability Index, FI(t)

𝐸𝐸𝑃𝑃𝑡𝑡 = 1 + 𝑎𝑎𝑃𝑃−𝑏𝑏𝑡𝑡 + (𝐸𝐸𝑃𝑃𝑑𝑑𝑑𝑑𝑑𝑑 − 𝑎𝑎 − 1)𝑃𝑃−𝑐𝑐𝑡𝑡

CAMERA MEASUREMENT

• Image analysis for surface foam bubbles – Diameter distribution, Dsfb-i(t)

– Amount, Nsfb(t)

• Foam bubble volume quantification

• Surface area index

SAI = SA/SA0 = f[ER(t), Dsfb-i(t), Nsfb(t)] Higher SAI = more foam binder surface available

= better aggregate coating

Laser Camera

FOAMED MIXTURE MEASUREMENT METHODS • Workability: ease with which asphalt mixture can be

placed, work by hand, and compacted • Coatability: degree of coating of the aggregate with

asphalt binder

Pre-heated Aggregate

Foamed Asphalt

WORKABILITY MEASUREMENT

Asphalt Loose Mix

Compaction Piston

τ) (k

Gyration

Reduction in Shear Stress

Phase II

Phase I Phase III τmax

Lower τmax = better workability

4,700g

𝝉𝝉 =𝟐𝟐 × 𝑭𝑭 × 𝑳𝑳

𝝅𝝅 × 𝒅𝒅𝟐𝟐

𝟐𝟐× 𝒉𝒉

COATABILITY MEASUREMENT

Water Water

Coarse Aggregate Fraction

Coarse Foamed

Loose Mix Fraction

Soak under water for 1 hour

Coatability Index (CI): relative difference in SSD water absorption

Higher CI = better aggregate coating

WORKABILITY & COATABILITY MEASUREMENTS

FACTOR ANALYSIS

Foamed Asphalt

• Binder Source and Grade

• Water Content • Temperature • Additives • Shearing action • Foamer Type

Foamed Mixture • Binder Source and

Grade • Water Content • Additives • Foamer Type • Mixture Type

• Significant effects on foamed asphalt characteristics Volume expansion, ERmax

Foam stability, FI

Foam bubble surface area, SAI

• Significant effects on foamed mixture properties Workability, τmax

Optimum foaming water content Wopt = lowest τmax ≠ Wmax

Equivalent or better performance at Wopt vs. HMA

FACTOR ANALYSIS – FOAMING WATER CONTENT

FACTOR ANALYSIS – LABORATORY FOAMER TYPE

InstroTek Foamer PTI Foamer Wirtgen Foamer

73 psi 30 psi Gravity

Main Difference – Asphalt Flow Pressure

FACTOR ANALYSIS – LABORATORY FOAMER TYPE

• Volume Expansion (ERmax) & Foam Stability (FI) Wirtgen > InstroTek > PTI (no expansion)

• Foam Surface Area (SAI) Wirtgen > InstroTek PTI: limited amount of foam bubbles

• Workability (τmax) & Coatability (CI) Wirtgen ≠ InstroTek ≠ PTI Individual Wopt Equivalent or better properties at Wopt vs. HMA

MIX DESIGN PROCEDURE

• Water content optimization Workability Coatability

• Performance evaluation Stiffness Rutting resistance Moisture susceptibility

MIX DESIGN PROCEDURE

Materials Selection

Add/Modify Mixture Components

Superpave Mix Design AASHTO R35

Performance Evaluation

Specimen Fabrication Foamed Mixture at

Indirect Tensile (IDT) Strength per

AASHTO T 283

Resilient Modulus (MR) per modified ASTM D 7369

Hamburg Wheel Tracking Test (HWTT) per AASHTO T 324

Fail AASHTO/DOT Specification

Pass AASHTO/DOT Specification

Optimum Binder Content

Lowest Max Shear Stress

(τmax)

Workability Evaluation on Foamed Mixture at

1, 2, and 3% water

Coatability Evaluation on Foamed Mixture at

Wopt% CI > 70%

Optimum Water Content

(Wopt%)

MIX DESIGN VALIDATION

Laboratory Testing

Workability Evaluation for Foamed

LMLC at Various Water Contents

Determination of Optimum Foaming

Water Content (Wopt%)

1st Plant Visit

Sampling of Raw Materials

Sampling of Plant Produced Foamed

Mixture at 5.5% Water Content

MIX DESIGN VALIDATION

Laboratory Testing

Workability Evaluation for Foamed

LMLC at Various Water Contents

Determination of Optimum Foaming

Water Content (Wopt%)

2nd Plant Visit

Mixture at Wopt% and HMA

Adjustment of Plant Foaming Water

Content to Wopt%

Workability Evaluation for Plant Produced HMA and Foamed Mixture at

5.5% and Wopt%

1st Plant Visit

Sampling of Raw Materials

Mixture at 5.5% Water Content

PERFORMANCE • Resilient Modulus • IDT Strength • Hamburg

SUMMARY

Volume Expansion: ERmax Foam Stability: FI

Foam Surface Area: SAI

Foamed Asphalt

SGC Compaction Data Workability: τmax

Water Absorption Method Coatability: CI

Foamed Mixture

Effect of Water Content

ERmax, FI, and SAI: Wirtgen > InstroTek > PTI τmax and CI: Wirtgen ≠ InstroTek ≠ PTI

(Individual Wopt)

Effect of Foamer Type

Mix Design Procedure for Foamed Asphalt Mixtures

(Wopt% = 1.0-2.0% in most cases)

Laser & Camera

Methods and metrics to

characterize foamed asphalt

Methods and metrics to evaluate foamed mixtures

WEBINAR SUMMARY

CONTRIBUTION OF RESEARCH STUDIES NCHRP 9-52: SHORT-TERM LABORATORY CONDITIONING OF ASPHALT MIXTURES Laboratory Aging Protocols New Method to Quantify Field Aging (CDD) Relationships between Field and Lab Aging Effects of Factors on Aging Effects of Aging on WMA New Interpretation of HWTT

CONTRIBUTION OF RESEARCH STUDIES NCHRP 9-53: PROPERTIES OF FOAMED ASPHALT FOR WMA APPLICATIONS Understanding of Foaming Factors Affecting Foaming New Test Methods for Foaming Characteristics Understanding of Foaming Effects on Mixtures Considerations of Coating and Workability Mix Design Procedures

Thank you!

Questions?

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