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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
NCHRP is...
AASHTO’s research program
• The state DOTs, through AASHTO’s Standing Committee on Research... – Sponsor and support NCHRP
– Suggest research topics and select final projects
– Help select investigators and guide their work through oversight panels
NCHRP delivers...
Practical, ready-to-use results • Applied research aimed at state
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
NCHRP Webinar Series • Part of TRB’s larger webinar
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
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
2
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
4
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
5
Aging Characteristics
Short-Term Conditioning
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)
6
Short-Term Conditioning
FIELD PROJECTS
7
Connecticut Florida Indiana
Iowa New Mexico South Dakota
Texas (2) Wyoming
Short-Term Conditioning
FIELD PROJECTS
8
Field Project WMA Production Temperature Plant Type RAP/RAS Aggregate
Absorption Binder Source
Texas I
Connecticut
Wyoming
South Dakota
New Mexico
Iowa
Florida
Indiana
Texas II
Short-Term Conditioning
9
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
Short-Term Conditioning
HWTT RRP DETERMINATION
10
Short-Term Conditioning
0.0E+00
1.0E-01
2.0E-01
3.0E-01
4.0E-01
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
0 5000 10000 15000 20000 25000 30000
Stra
in
Rut
Dep
th (m
m)
Load Cycle
Measured Rut Depth Predicted Rut Depth Viscoplastic Strain
Permanent Strain Stripping Strain
Stripping Number
LCSN LCST
RRP
VALIDATION OF STOA PROTOCOLS
11
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
LMLC
Lab < Plant
Lab > Plant
Lab = Plant
LMLC
Pro
pert
y
PMPC / Construction Core Property
Line of Equality
TASK 1
MIXTURE VOLUMETRICS FOR LMLC VS. PMPC
12
Theoretical Maximum Specific Gravity (Gmm)
2.3
2.4
2.5
2.6
2.7
2.3 2.4 2.5 2.6 2.7
PMPC
-G
mm
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
0.0 0.6 1.2 1.8 2.4 3.0
PMPC
-P b
a(%
)
LMLC - Pba(%)
TX I NM CT WY SD IA IN FL TX II
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
13
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
0 1400 2800 4200 5600 7000
PMPC
-M
R(M
Pa)
LMLC - MR (MPa)
TX I NM CT WY SD IA IN FL TX II
0
1400
2800
4200
5600
7000
0 1400 2800 4200 5600 7000C
onst
ruct
ion
Cor
e -M
R(M
Pa)
LMLC - MR (MPa)
TX I NM CT WY SD IA IN FL TX II
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)
14
> construction core > construction core
TASK 1
QUANTIFICATION OF FIELD AGING
15
• 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
16
0
5000
10000
15000
20000
25000
30000
35000
40000
Dec-11 Jul-12 Jan-13 Aug-13 Mar-14 Sep-14 Apr-15
Cum
ulat
ive
Deg
ree
Day
s (°
F-da
ys)
Coring Date
Texas New Mexico Wyoming South Dakota
Iowa Indiana Florida
TASK 2
MRR = 1.81 MRR = 2.23
17
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
18
CDD vs. PR (MR STIFFNESS)
TASK 2
19
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
20
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
Varia
ble
Mix
ture
Control Mixture
Positive Effect
Negative Effect
Insignificant Effect
Short-term: mixture property Long-term: mixture property ratio
TASK 3
FACTOR – WMA TECHNOLOGY
22
Short-Term: MR Stiffness
0.0
1.0
2.0
3.0
4.0
0.0 1.0 2.0 3.0 4.0
WM
A M
RR
atio
HMA MR Ratio
TX NM WY SD IA IN FL
0
200
400
600
800
1000
0 200 400 600 800 1000
WM
A -
MR
(ksi
)
HMA - MR (ksi)
TX I NM CT WY SD IA IN FL
Long-Term: MR Stiffness Ratio
TASK 3
FACTOR – PLANT TYPE
23
Short-Term: MR Stiffness Long-Term: MR Stiffness Ratio
0
200
400
600
800
1000
0 200 400 600 800 1000
BM
P M
ixtu
re -
MR
(ksi
)
DMP Mixture - MR (ksi)
IN TX II
0.0
1.0
2.0
3.0
4.0
0.0 1.0 2.0 3.0 4.0
DM
P M
ixtu
re M
RR
atio
BMP Mixture MR Ratio
IN
TASK 3
24
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
25
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
LTOA
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)
27
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
28
Dipstick Method
ERmax
HL
Properties of Foamed Asphalt
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.
29
Properties of Foamed Asphalt
FOAMED ASPHALT MEASUREMENT METHODS
30
Laser Device
Camera
Container
Laboratory Foamer
Properties of Foamed Asphalt
LASER MEASUREMENT
31
Higher ERmax = higher instantaneous expansion Higher FI(t) = better stability
1400
1420
1440
1460
1480
1500
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0 30 60 90 120 150
Dist
ance
Rea
ding
(mm
)
Expa
nsio
n Ra
tio
Time (s)
Fitted ER Measured ER Distance Reading
ERmax
Foamability Index, FI(t)
Properties of Foamed Asphalt
𝐸𝐸𝑃𝑃𝑡𝑡 = 1 + 𝑎𝑎𝑃𝑃−𝑏𝑏𝑡𝑡 + (𝐸𝐸𝑃𝑃𝑑𝑑𝑑𝑑𝑑𝑑 − 𝑎𝑎 − 1)𝑃𝑃−𝑐𝑐𝑡𝑡
CAMERA MEASUREMENT
32
• 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
Properties of Foamed Asphalt
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
33
Pre-heated Aggregate
Foamed Asphalt
Properties of Foamed Asphalt
WORKABILITY MEASUREMENT
34
Asphalt Loose Mix
Compaction Piston
F
h
L
d
Shea
r Str
ess (
τ) (k
Pa)
Gyration
Reduction in Shear Stress
Phase II
Phase I Phase III τmax
Lower τmax = better workability
4,700g
Properties of Foamed Asphalt
𝝉𝝉 =𝟐𝟐 × 𝑭𝑭 × 𝑳𝑳
𝝅𝝅 × 𝒅𝒅𝟐𝟐
𝟐𝟐× 𝒉𝒉
COATABILITY MEASUREMENT
35
Water Water
Coarse Aggregate Fraction
Coarse Foamed
Loose Mix Fraction
VS.
Soak under water for 1 hour
Coatability Index (CI): relative difference in SSD water absorption
Higher CI = better aggregate coating
Properties of Foamed Asphalt
WORKABILITY & COATABILITY MEASUREMENTS
36
Properties of Foamed Asphalt
FACTOR ANALYSIS
37
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
Properties of Foamed Asphalt
• 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
38
Properties of Foamed Asphalt
FACTOR ANALYSIS – LABORATORY FOAMER TYPE
39
InstroTek Foamer PTI Foamer Wirtgen Foamer
73 psi 30 psi Gravity
Main Difference – Asphalt Flow Pressure
Properties of Foamed Asphalt
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
40
Properties of Foamed Asphalt
MIX DESIGN PROCEDURE
• Water content optimization Workability Coatability
• Performance evaluation Stiffness Rutting resistance Moisture susceptibility
41
Properties of Foamed Asphalt
MIX DESIGN PROCEDURE
42
Properties of Foamed Asphalt
Materials Selection
Add/Modify Mixture Components
Superpave Mix Design AASHTO R35
Performance Evaluation
Specimen Fabrication Foamed Mixture at
Wopt%
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%)
No
Yes
Or
Or
MIX DESIGN VALIDATION
43
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
Properties of Foamed Asphalt
MIX DESIGN VALIDATION
44
Laboratory Testing
Workability Evaluation for Foamed
LMLC at Various Water Contents
Determination of Optimum Foaming
Water Content (Wopt%)
2nd Plant Visit
Sampling of Plant Produced Foamed
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
Sampling of Plant Produced Foamed
Mixture at 5.5% Water Content
Properties of Foamed Asphalt
PERFORMANCE • Resilient Modulus • IDT Strength • Hamburg
SUMMARY
45
Properties of Foamed Asphalt
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
W%
ERmax
FI
SAI
τmax
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
46
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
47
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
48
49
Thank you!
Questions?