2. Outline
Experiences
Academic – UNR, WRSC, WT, Purdue
Industry – GCI, Several Roles
Service – SP ETG, NCHRP, AAPT, NAPA, …
Lessons Learned
Materials
Labs and Equipment
Implementation
Lab vs. Field
Production & Construction
Context – Superpave and QC/QA All at Once
3. Lessons Learned
Things We Worried About:
Aggregate Properties (CAA, FAA, FEP)
Mix Design VerificationRestricted Zone
PMBs
How to Handle RAP
Performance Testing
Tenderzone
4. Lessons Learned
Asphalt Binder Specification – Chemical Goal
Physical Property Spec - Huge Improvement
Still - PG+
, MSCR, PPA, CRM, TB
Aggregates
Not Big Change in California – Early 1990’s
Restricted Zone – Guide
ARZ, BRZ, TRZ can ALL Perform Well
Some Sand May Be Needed
Washed Crusher Fines, Chips?
P200 Must Be Managed – Mix Sensitivity
5. ASTM STP December 2000
p200 Management - 19mm Example
0
1
2
3
4
5
6
7
8
9
10
4.0 5.0 6.0 7.0
% AC
%AirVoids
At Target p200 = Solid Lines
At Field Observed p200 = Dashed Lines
Reduction in AC
at 4.0% AV =
0.8% due to
+1.5% p200
Reduction in AV
at Opt AC = 1.8%
due to +1.5%
p200
6. Lessons Learned
Δ from AASHTO Standards = Challenging…
NDesign
Min VMA (increase vs. production)
D/A (smaller NMAS mixes)
FEP (3:1)
T283 (conditioning and minimums)
Adding Conflicting Requirements
Use or Generate Data via Shadow Specs First
7. Everything is Bigger in the Lab
Bigger Samples (4x)
Bigger Equipment
More Square Footage
$ Investment
SGC
4800g
Hveem
1200g800lbs - Really?
10. Compactors and Verification
Superpave Center and ETG – SGC’s
10 years
SGCs are NOT all the same
SGC Frame Compliance
Internal Angle Verification Needed
DON’T Buy a Headache!!!
Follow Your Owner?
Superpave Center – Mix Verification
Aggregates Batching
Dust Correction
Will Now Know Source of Δ
12. Hamburg Wheel Track Device (HWTD)
Colorado →Texas, … (Rutting and Stripping)
Slabs or paired cylindrical samples, 7 ± 2% AV (Cores OK)
8”diam x 1.75” steel wheel, 50pass/min, 158lb load
50ºC and 20k passes or ½” rut depth, SIP
50ºC and PG64 (5k), PG70 (10k), PG76 (20k) ≤ ½”
r & R not yet published
13. AASHTO T324 Hamburg Test Method
ILS by AMRL
SGC
4800g
Hveem
1200g
ILS
AMRL Prepared all Samples
Only Cutting and Test Method Variability
9.5mm 19mm
15. AASHTO T324 Hamburg ILS
Observations
Very Significant Variability in Results Between Labs
Did Not Publish Precision Statement
Conduct Ruggedness Experiment First
Key Factors Affecting Results:
Starting location of the wheel
Wheel track alignment on the sample
Number of sensors and sensor locations
Gyratory sample cutting and mold
Closely Inspect your New Equipment
Utah DOT Similar Experience – Great Job Addressing
Before Implementation
Encourage Similar in California
16. Dry Tensile Strengths vs. Binder Grade
Date of Design Agency
Method/Sample
Diameter
Laboratory Who Performed
Testing
Mix Design
Nominal
Maximum Size
Binder Grade
Aggregate
Source
Ant-Strip
Method
Dry Tensile
Strength (psi)
3/25/2010 Caltrans Hveem/4” Construction Materials Engineers 12.5mm PG 64-28PM Source A
Lime Slurry
Marination
86
1/31/2012 NDOT Hveem/4” NDOT 19.0mm PG 64-28NV Source A
Lime Slurry
Marination
100
1/31/2012 NDOT Hveem/4” NDOT 19.0mm PG 64-28NV Source A
Lime Slurry
Marination
76
5/29/2012 FAA Marshall/4” Eastern Sierra Engineering 12.5mm PG 64-28 Source A
Lime Slurry
Marination
71
8/24/12 NDOT Hveem/4” NDOT 19.0mm PG 64-22 Source A
Lime Slurry
Marination
125
10/1/2012 Caltrans Hveem/4” Construction Materials Engineers 9.5mm PG 64-28TR Source A
Lime Slurry
Marination
77
3/1/2013* Caltrans Hveem/4” Construction Materials Engineers 19.0mm PG 64-28 Source A
Lime Slurry
Marination
84
3/22/2013* Caltrans Superpave/6” GARCO - Stockton 19.0mm PG 64-28 Source A
Lime Slurry
Marination
94
*- The 3/22/2013 Superpave 6” diameter dry tensile strength data was performed using the same gradation and
optimum asphalt content obtained from the 3/1/2013 Hveem design as to permit a direct comparison of sample size vs.
dry tensile strength.
18. Dry Tensile Strength = f(PG Binder Grade)
Mix Type
Aggregate
Source
Binder
Type
Asphalt
Content
(BDW)
Compaction
Method
Dry
Tensile
Strength
(psi)
Hamburg
Rut Depth
@ 15,000
passes (in)
Hamburg
Inflection
Point (No. of
Passes)
¾” HMA Source A PG64-28 5.5 Hveem – 4” 84 n/a n/a
¾” HMA Source A PG64-28 5.5 Gyratory– 6” 94 0.1 >25,000
¾” HMA Source A PG70-10 5.5 Gyratory– 6” 211 n/a n/a
• Dry Tensile Specification > 120 psi
• Hamburg Rut Depth < 0.5in after 15,000 passes
• Hamburg Inflection point – min. 10,000 passes
19. Tensile Strength
Specimens under Tensile Stress/Strain
What Material Can Resist Tension?
Key Drivers of Tensile Strength
Bond
Binder Stiffness
Should PG70- 10 vs. PG64-22 vs. PG64-28 all have
same TSDry?
Binder Stiffness vs. Grade (1/2 or 2x)
NCHRP Report 444, "Compatibility of a Test for
Moisture-Included Damage With Superpave
Volumetric Mix Design“
No Difference in Hveem and Superpave TS
20. Impacts of Lab Turnaround Time
Function of:
Project Location/Logistics
Test Method
Available Resources
Test and Time
Volumetrics and In-Place Density ≈ 1-2 days
WTD ≈ 3 days
TSR ≈ 7 days
Risk (Production TSR Example)
≈ 2000 to 4000 tons/ day x $100/ton in-place
Over $1M per week (2kx$100x7days) – WOW!
How to Address Risk?
21. Plant Production
Aggregate Plant Balance?
VSI Crushers?
RAP Fractionation?
Treat Like Aggregate
Additional Feed Bins and Controls
Drive with Acceptance Criteria
Volumetric Specifications
Sensitivity to p200
More Washing?
Baghouse Controls?
Aggregate Breakdown
SGC = Plant?
How Addressed?
22. ASTM STP December 2000
p200 Management - 19mm Example
0
1
2
3
4
5
6
7
8
9
10
4.0 5.0 6.0 7.0
% AC
%AirVoids
At Target p200 = Solid Lines
At Field Observed p200 = Dashed Lines
Reduction in AC
at 4.0% AV =
0.8% due to
+1.5% p200
Reduction in AV
at Opt AC = 1.8%
due to +1.5%
p200
23. Aggregate Breakdown
Mix Design to Post-Plant (Lab to Field)
Must Consider in
Mix Design Process
Production Start-up
Gradation Acceptance
Does Breakdown in Lab Mixer and SGC =
Breakdown in Drum or Dryer and Pugmill?
NO
What Gradation Should be Used in Mix Design
Stockpile, Hot Bin, Coldfeed?
What Gradation Should be Used for Acceptance?
Coldfeed, Hot Bin, or Post-Plant?
24. 24
What About Production?
Lab Mix Design to Field Production
Differences are Real – Must Address
What Occurs During Production that Affects
Gradation and Volumetrics?
Breakdown in the Drum (p200 ↑)
If p200 ↑ Post Plant what will be Done to Maintain
4.0% Air Voids, …?
Reduce %AC?
Reduced Durability
Is this Good or Bad?
%AC
Rutting
Durability
25. Lab Mix Design to Field Production
Mix Design Purpose?
How to Address Δ’s - What is End Goal?
End Product Quality
Field Adjust AC and Grad to Desired
Volumetrics
Appropriate TV Δ’s
P200 dosing in MD?
Test Strip
%AC, Gradation, Volumetrics – Same Sample
…
27. Asphalt Binder Set Point
Verification (Hot Drop)
Plant Set Point = Mix Design OBC
In-Spec – Go to Production
Out-of-Spec - Repeat, Repeat, Repeat
Production
Plant Setpoint = Mix Design OBC
Standard Process
if PSP and OBC Δ ≤ 0.4% OK
If PSP and OBC Δ ≥ 0.4% Shut Down
QC/QA
if PSP and OBC Δ ≥ 0.0% PWL Compomised
Typical σT = 0.20
28. Lab Mix Design to Field Production
Lab to Field No %AC Set Point Change?
Impact on Volumetrics
Impact on %AC PWL/PF
σ%AC = 0.20 typical (CT, AMRL, …)
Off Target, no Set Point or TV Δ
36. Superpave is Technology Friendly
Can Technically Address in Lab
Neat, PMB
RAP
RAS
WMA
…
We Can Field Produce
37. Field Observations
NMAS
¾” has ¾” Rock in It
t/NMAS ≥ 3, Max by Density Measurement
BRZ can = Segregation (everywhere) & Workability
Challenges – Training and QC Critical
Density Matters!!!
Get All but 1.5% Immediately
Fewer Pneumatics
Tenderzone (not something new)
Truck Loading Focus
MTV’s
Joints
38. Field Observations
Have Compacted up to 5.5” Lift with ¾” NMAS
We Can Place and Compact Superpave Mixes
Tenderzone - special Kneeding compactors?
40. Training Needs
Significant Training Required:
Professional and Technical
Mix Designers and Technicians
Estimating Staff
Plants Staff
Construction Operations Staff
Inspection Staff
Agency/Contractors/Engineering Firms
Consider FHWA Efforts in Early 1990’s
41. My Gut
Importance of Training Will Be WAY Under Estimated
Lab Investment will Be Too Slow - Logistics Issues?
Issues with Differences in Caltrans and AASHTO and
City/County Specs – Design, Equipment, Acceptance,
Mix Management, … will Exist
Grad+D/A Spec, Grad +Vol Independent Samples
HWTD, Dry Tensile Strength, Lab to Field
Could Have HWTD Challenges if Not Patient
Could Not Address Aggregate Breakdown and Mix
Sensitivity
Some Aggregate Sources will Be Challenging
Required Plant Investments will Be Underestimated
There will Need to Be Specification Iterations
42. Moving Forward
Superpave = HUGE Step ForwardSuperpave = HUGE Step Forward
Late Adoption will Eliminates Others Early ChallengesLate Adoption will Eliminates Others Early Challenges
InvestmentInvestment
LabsLabs
Plant $ – VSI’s, RAP Feeder Bins, Baghouse ControlsPlant $ – VSI’s, RAP Feeder Bins, Baghouse Controls
Con Ops – No ProblemsCon Ops – No Problems
Technology – RAP, RAS, WMA, … friendly - JDITechnology – RAP, RAS, WMA, … friendly - JDI
Get Lab Equipment and Methods Right FIRSTGet Lab Equipment and Methods Right FIRST
We Will All Need to Continually ImprovementWe Will All Need to Continually Improvement
Binder, Mix Design, Perf Tests, Mix to StructuralBinder, Mix Design, Perf Tests, Mix to Structural
Design, Test Methods and SpecificationsDesign, Test Methods and Specifications
We Will Make Better Products and That Will Be Good forWe Will Make Better Products and That Will Be Good for
Our IndustryOur Industry