1. Rebecca McDaniel KDOT/KAPA Fall Forum November 5, 2014
Asphalt Update
Rebecca McDaniel
KDOT/KAPA Fall Forum
November 5, 2014

2. Topics North Central Superpave Center (NCSC) National Issues
Regional Issues
Recent Research at the NCSC
North Central Asphalt User Producer Group

3. History of the NCSC Established in 1994-95
FHWA initiative to assist states and industry implement Superpave
Initial focus on Superpave refinements and training
Evolved as Superpave became routine
Now working on variety of asphalt issues

4. Regional Center Illinois Indiana Iowa Kansas Michigan Minnesota
Missouri
Wisconsin
Nebraska
Ohio
Manitoba
Saskatchewan

5. Topics/Emphasis Areas
Recycling/Sustainability
Tire/Pavement Noise
Surface Characteristics
Materials and Mix Designs
Pavement Performance
Lab Testing

6. Current National Issues
Issues considered by Binder and Mix ETGs
MSCR Binder Test – replacement for elastic recovery
Ground Tire Rubber – conditioning, DSR testing
Low Temperature Binder Testing in DSR
Emulsions – PG grading
PPA

7. Current National Issues
Recycled Engine Oil Bottoms – binder aging, mixture low and intermediate temperature properties
RAP and RAS – proposed changes to R 35 and M 323
RAP/RAS and Recycling Agents
AMPT Testing
Beam Fatigue
LTPP WMA Experiment

8. Regional Issues Longitudinal Joints Tack Coats Premature Cracking
Durability
Shingles and High RAP Mixes
REOB

9. Current and Recent NCSC Research

10. Longitudinal Joints
NCSC report on Longitudinal Joint Specifications and Performance
Asphalt Institute best practices report and workshops
Joint density specs in some states reportedly successful

11. Deterioration may start with crack

12. Low density material lets in water

13. Deterioration progresses

14. Joint Construction Techniques
Echelon or Tandem Paving
Various Rolling Patterns
Butt, Tapered or Notched Wedge Joint
Edge Restraining or Precompaction Devices
Cutting Wheels
Infrared Joint Heaters
Joint Adhesives
Joint Sealers

15. Joint Type All can work or can fail.
Butt joints can crack and let in water.
Can be safety issues with drop off.
Pulling up adjacent lane affects productivity.
Wedge (tapered) and notched wedge.
Fewer safety concerns.
Challenging to compact.
Challenging to maintain notch under traffic.

16. Rolling Patterns Wide range of opinions
Some agreement to overhang unconfined edge by ~6 in.
Some prefer to stay back 6 in. from unconfined edge
Split on confined edge
Some overhang slightly, others pinch
Few recommend rolling from cold side

17. Pennsylvania DOT/PAPA/FHWA
2010 spec change – PWL end result, not method
Incentive for density over 89% Gmm (up to $5000 per lot), increasing to 90% in 2013
Disincentive for density below 89% (up to $12,000 per lot)
For density below 88%, seal with PG binder
One core centered over joint every 2500 linear feet
In North Central region, Michigan specification is a good model.

18. Penn Joint Densities Year Density Lots Average Joint Density
Average Mat Density
2007 18
87.8%
93.9%
2008 43
88.9%
94.1%
2009 29
89.2%
2011*
137
91.1%
*2011 – first year of PWL specification

19. My Conclusions There is no one way to construct joints.
Some things work in some cases and not in others.
Depends on mix, temperature, crew, underlying pavement, etc.
Give the contractor flexibility to choose the best option for given situation.
Joint sealers or adhesives have not always improved performance but rarely if ever hurt.
May be insurance, if economics are not too bad.
Joint quality specs have led to improved performance in some states.

20. Tack Coats Upcoming NCSC Research Tack Coat Installation Guidelines
Impact of poor tack coat application (accelerated testing)
QC/QA methods – lab and field
Tack coat bond testing
NCHRP Report on Tack Coats

21. Premature Cracking/ Durability
Several states are experiencing problems.
Causes are under investigation.
One approach to address this is to get more binder in the mixes.

22. How to Decrease Voids and Increase Durability?
Increase field density while maintaining effective binder content and VMA
Mixes need to be more compactable
Concept
Make changes in mix design to make mixes easier to compact in field
Design and compact mixes to 5% air
French mixes have no traffic densification

23. Optimizing Mixture Compaction
With same aggregate stockpiles
Same crushed faces, FAA and hardness
Decreasing gyrations→
Change in gradation
Lower mix stiffness in lab
Easier compaction in field
Need equal or better final mechanical properties to prevent traffic densification

24. Approach Start with 3 current mix designs 9.5 and 19 mm
100 gyration mixes
3-10 and million ESAL designs
Dolomite, limestone and slag with PG 64-22
Adjust gradation to achieve 5% voids
70, 50 and 30 gyrations
Maintain VMA and Vbe in 5% void mixes
Bailey method used to guide adjustments

25. Approach (continued) Test mechanical properties of the mixes
Want same (or better) mechanical properties in the higher air void mixes as the original mix provided.
Do not sacrifice rutting resistance for higher density.
Test 100 gyration mix at 7% and others at 5% air voids.
Determine number of gyrations to achieve 5% air voids and similar (or better) mechanical properties.
Field Validation
Can we achieve higher densities with revised mix design?

26. Lab Findings
With changes in gradation, mixes can be designed at 5% air voids in the lab
Re-designed mixes at 5% air can have higher stiffnesses and higher rut resistance than mixes designed at 4% air and compacted to 7% air
Concept looks promising
Field trial recommended and identified

27. Field Trial Mill and overlay on state road (SR13)
9.5 mm surface for million ESALs
Steel slag and limestone coarse agg
Manufactured and natural sands
7% RAS
N100 mix re-designed at 30 gyrations
Changed during production to N50

28. SR13 Mix Designs

29. SR13 Mix Design FN Test Original (N100) mix – FN = 841
Bigger is better, more rut resistant
Air voids ~1% low on both mixes
Statistically significant difference
Things look promising

30. Overall Average Core Density = 94.7%
Field Compaction
Sublot
Density 1
Density 2
Average 1
92.30
94.53
93.42 2
93.59
94.68
94.13 3
96.29
96.69
96.49
Overall Average Core Density = 94.7%
Target 95%
No change in compaction equipment nor patterns!

31. Conclusions
Mixes designed at 5% air in lab can be compacted to 5% in the field with minimal to no changes in compaction process.
Results of testing reheated plant produced mixes did not agree with lab research nor mix design.
Field trial will show if rutting develops.
Second field trial being placed this month.

32. Anticipated Benefits Potential 2-3 years of increased service life
Potential savings of $20-30 million a year
Based on $300 million HMA rehab budget and that 50% of the HMA pavements reaching end of life do so because of durability problems

33. Current Research
Analysis of the MSCR Binder Test and Specifications for Implementation in Indiana
Current polymer-modified binders seem to be over-engineered.
May provide method to allow use of GTR.
Can MSCR spec maintain good performance while lowering polymer loadings and reducing costs?

34. NCHRP Synthesis Projects
Pavement Patching Practices
Patching practices for asphalt and concrete pavements.
Report published onlinepubs.trb.org/onlinepubs/nchrp/nchrp_syn_463.pdf
Fiber Additives for Asphalt Mixtures
Fibers for dense, open and SMA mixtures.
Report in publication.

35. Technical Support
Third Party Testing

36. 9/20/2018

37. Third Party Testing Testing agg sources for polish resistance.
Binder extraction and testing for contractors for RAP mix design.
Mix testing for contractor experimenting with recycling agent.
Friction testing of thermoplastic material.
Field friction testing of high friction surfaces and microsurfacing.
Tack coat bond strength testing.

38. February 2-3, 2015 IHotel Champaign, IL
2015 Asphalt Technical Conference Joint Meeting with Illinois Bituminous Paving Conference
February 2-3, 2015
IHotel
Champaign, IL

39. Agenda February 2 – Reception and Exhibits
NCAUPG Management and NCSC Steering Committee meetings
February 3 – Presentations and Exhibits
Regional updates – panel discussion with states
Tack Coats
Thin Overlays for Pavement Preservation
Use of Local Aggregates
Recycled Engine Oil Bottoms
Performance Based Mix Designs
Mix Optimization for Quality
Constructability Issues and Consequences

40. More Information https://engineering.purdue.edu/~ncaupg/
Look under What’s New
bituminousconference/program.html

41. Rebecca McDaniel North Central Superpave Center rsmcdani@purdue
Rebecca McDaniel North Central Superpave Center 765/ ext 226 engineering.purdue.edu/NCSC