RAP, RAS and Durable Asphalt Pavements
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Transcript of RAP, RAS and Durable Asphalt Pavements
www.wrsc.unr.edu
RAP, RAS and Durable Asphalt Pavements
Adam Hand, PhD, PEPavement Engineering and Science Program
University of Nevada, Reno
CalAPA Fall ConferenceSacramento, CA – October 27, 2016
www.wrsc.unr.edu
What’s Up With Recycled Materials Use inand Durability of HMA?
• NAPA
• Nationally
– FHWA
Binder ETG
Mixture ETG
TFHRC
– TRB Annual Meeting
– NAPA Annual Meeting
– AAPT Annual Meeting
– NCHRP Projects
“The Pendulum Swung
Too Far and We Need to
Get Durability Under
Control “
www.wrsc.unr.edu
How is HMA Durability Improved?
• Raw Materials
– Aggregates - Contribute to Cracking Resistance?
– Asphalt Binder
Stiffness + Ability to Relieve Stress + Aging Sensitivity
• HMA Design
– Binder Content
Higher the Better, VMA, Gsb vs. Gse if using RAP/RAS
– Denser Mix Types
• Construction
– In-place Density ≤ 8%
www.wrsc.unr.edu
Where is the Pendulum Headed?
• Mid 1990’s Superpave without Performance Indicator Tests
• Early 2000’s Rutting and Moisture Sensitivity Focus
– Hamburg Wheel Track Device Proliferation
– More Fine Graded Mixtures
• Late 2000’s Economic Collapse and Escalating Binder Costs
– Increased Competition/Collapsing Margins
– Recycling Focus and Push
• Mid 2010’s Mix Durability WITHOUT Forgetting Rutting
• Late 2010’s BMD and Moderate Recycled Materials
www.wrsc.unr.edu
Outline
• RAP & RAS Use
• Agency & Industry Responses
• AASHTO Standards & Related NCHRP Projects
• Performance
• Trends - Our Future?
www.wrsc.unr.edu
2014 NAPA Annual Survey
• 2015 Survey Soon
• 2014 Trends
Continued?
www.wrsc.unr.edu
Count of State DOT Allowable RAP Percentages
• 2013 to 2014 Reduction in 10-20% & Increase in 20-30+%
• 4 DOTs > 30% RAP, 2 Since Reduced
www.wrsc.unr.edu
FHWA MemoOctober 2014
• Premature Cracking
• High Recycled Binder
Content
– RAP & RAS
– RAS
www.wrsc.unr.edu
Caltrans MemoJune 2016
• Premature Cracking
Failures
• Caltrans NSSP
– >15% RAP
– Blending Charts
www.wrsc.unr.edu
2015 Caltrans SS & NSSP on %RAP & %ABR
Type A HMA Location in Pavement
Allowable ABR (%)
2015 Standard Specification (RSS 05-06-16)
NSSP
Upper 0.2’ (Surface Courses)
= 25% n/a
Below 0.2’ (Intermediate or Base Courses)
= 40% n/a
Reference and Levels PG Required
2015 Standard Specification (RSS 05-06-16)
NSSP
%RAP
= 15% Specified PG n/a - silent
>15% = 25% As specified
or -1 PG by REQUEST
Blending Charts & Meet Specified PG
>25% = 40% Does not allow > 25% RAP n/a - silent
%ABR >0% = 25%
As specified or
-1 PG by REQUEST n/a - silent
>25% = 40% -1 PG REQUIRED n/a - silent
www.wrsc.unr.edu
Current NCHRP Projects
• Many Related to High ABR Performance, RAP, RAS, Aginghttp://www.trb.org/NCHRP/NCHRPProjects.aspx
www.wrsc.unr.edu
NCHRP Project Highlights• 09-52 Short-term Laboratory Conditioning of Asphalt Mixtures
– Lab mix short-term aging underestimates field aging
• 09-54 Long-term Aging of Asphalt Mixtures for Performance
Testing and Prediction
– AASHTO R30 Lab mix long-term aging (compacted mix at 85°C for 5
days) significantly under estimates long-term field aging
– Preliminary - Loose mix oven aged at 95°C for 5 to 25 days
• 09-58 Effect of Recycling Agents on Asphalt Mixtures with High
RAS & RAP Binder Ratios
– RA’s not Equal, ΔDose Rutting/Cracking, Aging Susceptibility
Diminishes Effectiveness, Compatibility, Binder Availability
• 09-61 Short- and Long-term Binder Aging Methods
– Replace or Modify T240 and R28
www.wrsc.unr.edu
Current AASHTO Standards
• AASHTO M320 PG Binder Grading
– AASHTO T240 Short-term Binder Aging (RTFO)
– AASHTO R28 Long-term Binder Aging (PAV)
• AASHTO M323 Superpave Mix Design
– AASHTO R30 Short-term Mixture Aging
– AASHTO R30 Long-term Mixture Aging
• AASHTO MP15 Recycled Asphalt Shingles
– AASHTO PP78 RAS in HMA
NCHRP 9-61
NCHRP 9-61
NCHR 9-52
NCHRP 9-54
PP78
RevisionsSignificant Change is Coming – Not Bad, but
Different
www.wrsc.unr.edu
AASHTO PP78 Changes before SOM
• Increase %AC over Optimum
– 0.1%AC per 2%RAS
• ΔTc ≤ -5°C
– On Blended Virgin/RAS Binder
What is Virgin Binder ΔTc?
What is RAP/RAS/Virgin Binder ΔTc?
www.wrsc.unr.edu
What is RAP Stiffness Range in California?
• Consider Climate
– Central and North Coast
– San Joaquin Valley
– Southern Deserts
• PG76-16 to PG100-4
– 4 PGs so 4x Stiffness
and ?x Embrittlement
• Is Cracking Similar in the
Different Environments?
www.wrsc.unr.edu
High ABR HMA Performance Observations
• NCHRP Report 752
• Illinois DOT
• FHWA ALF
• NCAT
• Nevada
• MinnRoad
• WiscDOT
– Mathey
www.wrsc.unr.edu
Current Focus – High ABR Mixes
• What is High Asphalt Binder Replacement?
– >25% Virgin Asphalt Binder Replacement with RAP, RAS, or RAP&RAS
• %ABR = %Asphalt Binder Replacement
– Specs Changing to %ABR from %RAP or %RAS
– Why?
%AC in 25% Coarse RAP ≠ %AC in 25% Fine RAP
RAP with 4% vs. 5.5%AC
Tear-off RAS vs. Manufacture Waste RAS
…
• Why Does It Matter?
– ↑ %ABR = ↑ Binder Stiffness + ↓Stress Relaxation
– High Stiffness/Low Stress Relaxation = Cracking and Durability Issues
www.wrsc.unr.edu
IL DOT →FHWA ALF High Binder Replacement Mixtures
• FHWA Memos – High ABR, RAS and REOB Warning to DOTs
• FHWA lllinois DOT Memo
– http://www.youtube.com/watch?v=zJv2oZG2Mys
• Illinois DOT Reduced %ABR
– 40% to 25% Base Mix
– 40% to 15% Surface Mix
– 40% to 10% PMA Mix
• FHWA ABR RESEARCHRAP, High RAP, RAS, RAP+RAS
Sections with and without PG Grade
Drops
www.wrsc.unr.edu
FHWA ALF – Like HVS used in California
• Simulated Truck Loading and Pavement Temperature
• 35,000 Load Cycles per Week
• 7k to 19k Wheel Load
www.wrsc.unr.edu
FHWA ALF Cycles to 200” of Cracking
0
50
100
150
200
250
300
350
400
450
L1: 0% ABRControl PG64-
22
L9: 20% ABRRAP PG64-22Foamed WMA
L4: 20% ABRRAP PG64-22
WMA Evotherm
L6: 20% ABRRAP PG64-22
L11: 40% ABRRAP PG58-28
WMA Evotherm
L3: 20% ABRRAS PG64-22
L5: 40% ABRRAP PG64-22
AL
F C
ycle
s t
o 2
00
" C
rackin
g
Lane and Material
www.wrsc.unr.edu
FHWA ALF Crack Life Ratio
100
73
38
3028
16
11
0
10
20
30
40
50
60
70
80
90
100
L1: 0% ABRControl PG64-
22
L9: 20% ABRRAP PG64-22Foamed WMA
L4: 20% ABRRAP PG64-22
WMAEvotherm
L6: 20% ABRRAP PG64-22
L11: 40% ABRRAP PG58-28
WMAEvotherm
L3: 20% ABRRAS PG64-22
L5: 40% ABRRAP PG64-22
Cra
ck L
ife
Ra
tio
(%
)
Lane and Material
www.wrsc.unr.edu
FHWA ALF Findings
• Use of Recycled Materials Significantly Impacts Cracking
(Fatigue) Performance
– Virgin, low RAP, high RAP, RAS
• Grade Bumping Down improves Performance Slightly
• Foaming helps with low RAP at WMA Temperatures
• FHWA Determining How Much “Additional Virgin Binder over
Optimum is Need for Recycle Mixes” to Achieve Equal
Cracking Performance to Virgin Mix
– VTRC (VDOT)
≈ 0.1%/10% RAP ABR
≈ 0.X/10% RAP ABR
www.wrsc.unr.edu
RAP/RAS Compatibility with Polymer Modified Asphalt Binders
• NCAT Test Track
– Florida DOT Top Down Cracking
RAP and RAS
• Nevada
– RAP Only
www.wrsc.unr.edu
NCAT Test Track (FDOT top down cracking test sections)
• 2 Mile Oval, Conventional Construction, Highway Trucks
• 4 Mix/Binder Combinations
• No Distress Except Top Down Cracking at 10M ESALs
PMA-0%
RAP
GTR-0%
RAP
PMA-20%
RAP
PMA-20%
RAP + 5%
RAS
www.wrsc.unr.edu
NCAT Test Track (FDOT top down cracking test sections)
0
10
20
30
40
50
60
70
80
90
100
0 2000000 4000000 6000000 8000000 10000000 12000000
Perc
ent
Lane C
rackin
g
Traffic (ESALs)
PMA-0% RAP
GTR-0% RAP
PMA-20% RAP
PMA-20% RAP + 5% RAS
“Stiffer polymer-
modified binders
should not be used
in conjunction with
RAP/RAS mixtures
because this causes
mixes to be too stiff”
www.wrsc.unr.edu
Other NCAT Technology News Updates
• 2016 “Go to” Florida DOT high traffic mix
– PG76-22 (No RAP/RAS Allowed)
• Michigan DOT
– Design Air Voids = 3% to increase Optimum %AC
• Colorado DOT
– Revised Section 403
– CDOT has ability to adjust contractor mix design optimum %AC
up & only fine graded mixes or SMA for surface course to
improve Durability
www.wrsc.unr.edu
Nevada Study
• Aggregate Source & Blend
• 3 RAP Sources
• 2 PG Binder Grades
• All Properties – Just Fatigue Here
www.wrsc.unr.edu
Influence of %RAP on Fatigue of Mixes with Polymer Modified Binder
30
0,0
00
1,2
00
,00
0
4,5
00
,00
0
www.wrsc.unr.edu
Nevada Study
100
4 2
14
51
3 2
0
10
20
30
40
50
60
70
80
90
100
Fatigue
LIfe R
atio
www.wrsc.unr.edu
Backgroud
• Concerns with long term pavement performance related to
binder durability is not new
Predates Superpave & PG binders
Focus of many studies simply related to binder aging
• Asphalt Institute - Anderson 2011 – REOB Concerns
– Rheological & ductility of PAV binders and binders recovered from
aged field mixtures
– Relationship to non-load associated distress
–ΔTc of 2.5°C = cracking warning limit, ΔTc = 5°C
point where binder durability lost
www.wrsc.unr.edu
Fatigue
Cracking
Rutting
PAV - aging
RTFO - aging
No aging
Time
Construction
[RV] [DSR]
Low Temp
Cracking
[BBR]
[DTT]
Superpave PG Binder Specification
www.wrsc.unr.edu
Binder Relaxation Properties
• Bending Beam Rheometer measures Stiffness and m value
• BBR m value measures relaxation or ability of binder to
relieve stress at cold temperatures
• As binder ages m value continues to decrease indicating loss
of relaxation properties (embrittlement) while the stiffness
increase levels off
• ΔTc is an indicator of embrittlement = difference in temp
where S = 300MPa and m value = 0.3
www.wrsc.unr.edu
ΔTc Concept for REOB/CrackingWhat is ΔTc ?
• ΔTc=BBR S Tcritical – BBR m Tcritical
• Is negative value for m-controlled binders
• 2xPAV
980 mN (100 g) Load
Asphalt Beam
Deflected PositionAsphalt Beam
Original Position
www.wrsc.unr.edu
So Why is Any of This Important?
• As Binders age they lose the ability to relax stresses,
mechanical or thermal
– Stiffness Increases
– Ductility Decreases
– Brittleness Increases
• Having a means of identifying when we can expect field
problems would be worthwhile
Spread between BBR S & m Tcritical values increase, ΔTc
becomes more negative
www.wrsc.unr.edu
Blending Charts – Do they help? Are they enough?
0 20 40 60 80 100
100 80 60 40 20 0% RAP
% New
Vis
co
sity o
r G
*/S
in
of R
AP
Bin
de
r (O
ld)
Vis
co
sity o
r G
*/S
in
of V
irg
in B
ind
er
(Ne
w)
Spec Limits
10-25% RAP
Percentages of Virgin and RAP
Material
www.wrsc.unr.edu
Comparative Crude Source Study
• 2006 Mathy constructed 5 test sections for MNDOT on
Olmsted CTH 112 near Rochester, MN
– 3 test sections compared performance of 3 different crude sources
of the same PG Grade, all (NEAT)
PG 58-28 Source #1, 0% RAP
PG58-28 Source #2, 0% RAP
PG58-28 Source #3, 0% RAP
– 2 test sections compared PG 58-34 PMA (0% RAP) and PG 58-34
(NEAT) + 20% RAP
www.wrsc.unr.edu
0.0
4.0
8.0
12.0
16.0
20.0
24.0
PG58-34(neat)+20% RAP
PG58-34(PMA)+0% RAP
PG58-28 S1(neat)+0% RAP
PG58-28 S2(neat)+0% RAP
PG58-28 S3(neat)+0% RAP
Lo
ng
itu
din
al/T
ran
svers
e C
rackin
g,
mF
ati
gu
e C
rac
kin
g,
m2
MN CTH 112 Cracking Data4 Years
Transverse Longitudinal Fatigue
www.wrsc.unr.edu
0.0
4.0
8.0
12.0
16.0
20.0
24.0
PG58-34(neat)+20% RAP
PG58-34(PMA)+0% RAP
PG58-28 S1(neat)+0% RAP
PG58-28 S2(neat)+0% RAP
PG58-28 S3(neat)+0% RAP
Lo
ng
itu
din
al/T
ran
svers
e C
rac
kin
g,
mF
ati
gu
e C
rackin
g,
m2
MN CTH 112 Cracking Data5 Years
Transverse Longitudinal Fatigue
www.wrsc.unr.edu
0
50
100
150
200
250
300
350
400
450
500
550
-7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0
To
tal
Cra
ckin
g,
m
ΔTc of Recovered Binder from Cores (Top 1/2")
MN CTH 112 Cracking DataTotal Cracking vs. ΔTc of Recovered Binder (8 Years)
PG58-28 S2 (neat)+0%
RAP
PG58-34 (PMA)+0%
RAP
PG58-28 S1 (neat)+0%
RAP
PG58-28 S3 (neat)+0%
RAP
www.wrsc.unr.edu
MnROAD Test of 3 Binders
• Constructed September 1999
• 3 Binders
– PG 58-28
– PG 58-34
– PG 58-40
• Trafficked until April 2007
• Annual Distress Surveys Conducted
www.wrsc.unr.edu
MnROAD COMPARATIVE BINDER STUDY
58-28
58-34
58-40
y = -160.85x - 417.74R² = 0.9957
0
100
200
300
400
500
600
700
800
900
1000
-9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0
LIN
EA
R F
EE
T O
F C
RA
CK
ING
ΔTc, °C
5.5 year total cracks (Non CL) = F(ΔTc 40 hr. PAV)
5.5 year total cracks (Non CL) Linear (5.5 year total cracks (Non CL))
RATIO CRACKS IN YEAR 5.5 TO YEAR 4
BINDER YEAR 5.5 YEAR 4 RATIO
58-28 126 20 6.3
58-34 13 0 ∞58-40 924 77 12
58-28
58-34
58-40
y = -12.935x - 29.753R² = 0.9946
0
10
20
30
40
50
60
70
80
90
-9.0 -8.0 -7.0 -6.0 -5.0 -4.0 -3.0 -2.0 -1.0 0.0
LIN
EA
R F
EE
T O
F C
RA
CK
ING
ΔTc, °C
4 year total cracks (Non CL)=F(ΔTc 40 hr PAV AGED BINDER)
4 YEAR TOTAL CRACKS (NON CL) Linear (4 YEAR TOTAL CRACKS (NON CL))
www.wrsc.unr.edu
Findings
• Blending Charts and ΔTc Provide DIFFERENT Answers
• ΔTc < -5°C (i.e. more negative) for the 40 hour PAV is
associated with the increased levels of pavement distress
after approximately 5 years of service
• Use of some blend additives can accelerate the decrease of
ΔTc at equal dosage levels
– This is exacerbated when trying to accommodate high RAP
&/or RAS binder replacement levels
• Use of RAS in mixes at levels ≈ 4% will significantly
accelerate the decrease in ΔTc as mixes age
www.wrsc.unr.edu
Gerry’s Comments
• All asphalt binders are not created equal
– Crude source—which dictates compositional makeup
affects long term performance
– We all know this and yet are perplexed when OUR
pavement doesn’t ALL perform well
– Not all binders are refined to grade, more likely today than
previously
– In some cases binders are post refining blends of stiffer
materials with lower stiffness VTB’s or gas oil
– Non asphaltic materials are being used to produce finished
binders (petroleum oils, bio-based oils, PPA, various types
of polymers)
www.wrsc.unr.edu
Our Future?
• ABR used vs. % RAP or %RAS• Allowable %RAP ABR↓ likely
15-25%?• Allowable %RAS ABR↓↓↓ or Disallowed
2-3%• RAP &/or RAP with PMA ↓↓↓ or Disallowed• Allowable RAP &/or RAS different for
– Surface vs. Base Mixes• REOB Disallowed &/or ΔTc in Specs (NE & SE)
– Especially if RAP &/or RAS Mixes• “Balanced” Mix Design
– New Lab Aging Conditions in Mix Design
– “Optimum %AC+”
www.wrsc.unr.edu
Balanced Mix DesignVolumetrics + Rutting/MS Test + Cracking Test
• Raw Material Properties• Volumetrics
DC
T?
SC
B?
Rutting/MS
HWTD?
DurabilityAt What
Temp?
At What
Temp?
www.wrsc.unr.edu
Leading Edge
• RAS
– 1X State DOT’s
• REOB/ ΔTc
– NEAUPG
– SEAUPG
• Balanced Mix Design
– NAPA Durability Committee
– FHWA Mix ETG BMD Taskforce
– State DOT’s
Louisiana, Illinois, New Jersey, Wisconsin (almost)
www.wrsc.unr.edu
Our Industry Responsibility - Get It Right
• Agencies
• Producers/Contractors
• Associations
• Academia
Our
Industry
Our
Responsibil
ity
www.wrsc.unr.edu
92nd AAPT Annual Meeting and Technical
Sessions
The 2017 Annual Meeting will be held March 19-22,
2017
The Island Hotel, Newport Beach, California USA2017 Annual MeetingThe Annual Business Meeting and Technical Sessions of the
Association of Asphalt Paving Technologists (AAPT) will be March 19-
22, 2017 in Newport Beach, California at The Island Hotel
(www.islandhotel.com). The annual meeting includes asphalt-related
technical sessions comprised of peer-reviewed papers, and invited
presentations on specific topics in the Leading Edge Workshop, AAPT-
ISAP International Forum, and Symposium. Please see the Annual
Meeting page (http://asphalttechnology.org/annual-meeting.html) for
more details as they become available.
Important datesAugust 15, 2016 - deadline for submitting papers (CLOSED)
October 10, 2016 - peer reviews completed
November 4, 2016 - notification of paper acceptance
December 2016 – Annual Meeting registration opens
March 19 to 22, 2017 - Annual Business Meeting and Technical Sessions
Our 2017
venue
For the latest information please check our web site at: http://www.asphalttechnology.org
AAPT Office:6776 Lake Drive, Suite 215
Lino Lakes, MN 55014
Phone: 651-293-9188
Fax: 651-293-9193 or Email: [email protected]
www.wrsc.unr.edu
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html
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