1. TRENDS IN ASPHALT PAVEMENT
Cliff Ursich, PE, Flexible Pavements of Ohio

2. Trends In Asphalt Pavement
Thickness Design
Materials
Pavement Preservation
Longitudinal Joint Construction Strategies

3. Pavement Thickness Design
TREND: Utilization of chemically stabilized soil as a structural component in pavement thickness design.
ODOT research…Question: Is the improvement in soil stiffness a lasting improvement such that ODOT can confidently use it when determining pavement thickness?

4. Pavement Thickness Design
TREND: Utilization of chemically stabilized soil as a structural component in pavement thickness design.
ODOT research…Question: Is the improvement in soil stiffness a lasting improvement such that ODOT can confidently use it when determining pavement thickness?

5. Does Stabilization Last?
Results of stabilized subgrade modulus from analysis of Dynamic Cone Penetrometer (DCP) tests – ODOT research State Job No:
20 sites tested
ODOT projects constructed between years 2001 and 2011
15 flexible pavement sections; 5 rigid pavement
Stabilized Subgrade Modulus
Test Method
FWD back-calculation
Dynamic Cone
Overall Ave.
108.7 ksi
133.7 ksi
Note: an ODOT thickness design for non-stabilized soil would use a value typically between 4 ksi to 10 ksi

6. Does Stabilization Last? YES
Approx. 4 to 10 ksi
Figure 20. Whisker plot of stabilized subgrade modulus determined from Dynamic Cone Penetrometer (DCP) measurements for all test sites.

7. Survey Response – States Taking Structural Credit for Stabilized Soil

8. Effect of Stabilization on Aggregate Base Strength Contribution
441, Type 1, etc.
441 Type 2, etc.
301(3” min.) or
302 (4” min)
304 IMPROVED CONFINEMENT!
Stabilized Subgrade, Item 206
IMPROVED STIFFNESS FROM STABILIZED SUBGRADE RESULTS IN IMPROVED CONFINEMENT AND GREATER AGGREGATE BASE STRENGTH.

9. Effects of Confinement on Aggregate Base Layer
Modulus of aggregate base layer placed on stabilized subgrade. ODOT research State Job No:
20 sites tested
ODOT projects constructed between years 2001 and 2011
15 flexible pavement sections; 5 rigid pavement
Stabilized Subgrade Modulus
Test Method
FWD back-calculation
Dynamic Cone
Overall Ave.
170.9 ksi
156.3 ksi
Note: an ODOT thickness design for non-stabilized soil would use a value 30 ksi

10. Effects of Confinement on Aggregate Base Layer
Approx. 30 ksi
Figure 23. Whisker plot of granular base modulus determined from Dynamic Cone Penetrometer (DCP) measurements for all test sites.

11. Implications for Pavement Thickness Design
Stabilized Subgrade Layer Coef.
Agg. Base (Item 304) Layer Coef.
Test Method
FWD AASHTO 2.3.5
DCP AASHTO 2.3.5
Overall Ave.
0.27
0.29
0.32
0.31
ODOT current practice: As of Nov. 1, 2015
Mr for subgrade multiplied by 1.36
Layer coefficient for Item 304 = 0.17 (increased from 0.14)

12. Trends In Asphalt Pavement
Thickness Design
Materials
Pavement Preservation
Longitudinal Joint Construction Strategies

13. TREND: “Balanced Mix Design” aka “Optimized Mix Design”
Materials
TREND: “Balanced Mix Design” aka “Optimized Mix Design”
Advent of performance-based mix testing capabilities gives opportunity to develop mixes that will better resist deformation/rutting, cracking, and stripping.
Traditional asphalt mix formulations are developed using volumetric principles and requiring specific aggregate physical properties.
Volume of asphalt needed to ensure mix property of stability,
Volume of asphalt needed to fill voids in the mineral aggregate yet ensuring sufficient air in the mix for long term durability,
Specifying aggregate angularity and crushed percentages, etc.

14. Volumetric Mix Design

15. Volumetric Mix Design
Premise: An asphalt mixture will perform satisfactorily if the volumetric properties meet the specified requirements at the mixture design air void content.
This premise proved satisfactory for many years, however, with the growing use of modified asphalt binders and reclaimed materials in asphalt mixes, reliance strictly on volumetric properties to predict pavement performance has shown to be inadequate.

16. Optimized Mix Design
Premise: Optimizing asphalt mixture composition based upon the results of performance tests will better ensure desired performance on the road and greater efficiency in material selection.
Performance measures:
Resistance to pavement deformation/rutting
Improved crack resistance in low temperatures
Improved resistance to reflection cracking
Improved durabilty (i.e. resistance to stripping)

17. Optimized Mix Design
Performance tests:
Rutting resistance, stripping

18. Optimized Mix Design
Performance tests:
Cracking resistance

19. Volume of effective binder
Optimized Mix Design
Where asphalt mix durability is found.
Volume of effective binder
Rutting Resistance
Cracking Resistance

20. Trends In Asphalt Pavement
Thickness Design
Materials
Pavement Preservation
Longitudinal Joint Construction Strategies

21. Pavement Preservation
TREND: Increasing interest in “Thinlays”
Asset management /pavement preservation concepts are leading agencies to more frequent, applications of less substantial pavement surface treatments.
Image source: FHWA

23. Pavement Preservation
ODOT’s current asphalt mix preservation treatment is “Smoothseal” (spec. name: Item 424, Fine-Graded Polymer Asphalt)
An industry innovation introduced formally to Ohio’s pavement preservation market in 2002.
Has experienced wide acceptance in Ohio and is nationally recognized.
Facility types on which the material has been used: all traffic levels including interstate and multi-use path

24. Asphalt Pavement Maintenance
ODOT challenge to the asphalt industry…do it again. Innovate a new preservation mix type with these attributes…
Less cost per square yard than Item 424
Performs like an overlay – smoother ride, better life than surface treatments
Acceptable friction performance
Design flexibility – rutting resistant on heavy traffic roads, cracking resistance on the lightest traffic roads

25. Pavement Preservation
Industry Response…develop a Thinlay Asphalt Pavement product.
What’s a thinlay?
“Thinlay” is a nationally established term that connotes a thin layer of asphalt pavement.
Thinlays are a pavement preservation treatment for preserving pavement assets.
They are for use on structurally sound pavements (no fatigue failure evident).
Typically ¾-inch to 1” thin.

27. Thinlay Asphalt Pavement Development
Desired Performance Attribute
 Evaluation Method / Comments
Resilient (self-healing, less brittle, improved crack resistance, slower oxidation)
Evaluate impact of off-spec to produce greater ductility
Rutting resistant (commensurate with traffic level)
Use LWT to evaluate deformation resistance
Evaluate for: blow count, natural/man. sand ratio, RAP effect on stiffness
Appropriate friction properties
Use polisher to quantify
Evaluate ODOT skid results for similar pavement type
Restorative of serviceability
Evaluate pre and post construction IRI
Aesthetically positive to ODOT and user
Survey

28. Thinlay Asphalt Pavement Development
Desired Construction Attributes
 Evaluation Method / Comments
Utilizes conventional production, placement, and compaction equipment
Avoid costs associated with specialized equipment and labor
Readily compactible
Evaluate for maximum percentage of natural sand
Places consistently with uniform texture/segregation resistant
Set limits of JMF such that mix placement is repeatable in all areas of Ohio, using locally available aggregate.
Set target P4, bands +/- 5%
Lift placement thinness ¾ inch (2 X max agg size)
Evaluate use of 3/8ths max diameter aggregate

29. Thinlay Asphalt Pavement Development
Desired Mix Attributes
 Evaluation Method / Comments
Max agg size 3/8 inch
Utilizes locally available aggregates for cost efficiency
Meeting ODOT quality
Advantages lower cost aggregates (fine vs. coarse)
Evaluate proportions as related to cost efficiency
Optimizes asphalt binder utilization to ensure resilience/flexibility
Evaluate binders off-spec 52-28, 58-28, by testing completed mix for stability, flow, retained energy
High impermeability (shingle-like)
Evaluate permeability by test method
Design flexibility to accommodate use on LT, MED, HVY traffic pavements
Goal is one mix type with capacity to alter ratio of mix components to meet demands of use on LT, MED, and HY traffic roads

30. Thinlay Asphalt Pavement Development
Desired Acceptance Attributes
 Evaluation Method / Comments
Lower life cycle cost than chip sealing or microsurfacing
Evaluate treatments for LCCA and annual cost; PCR service life vs. actual
Simplicity in contract administration including: field inspection, QC
QC: gradation & binder content only; schedule of testing frequency provided
Compaction by method spec &.16
Placement by wt./unit area
Payment in CY

31. Thinlay Asphalt Pavement Development

32. Thinlay Asphalt Pavement Development

33. Thinlay Asphalt Pavement Development

34. Trends In Asphalt Pavement
Thickness Design
Materials
Pavement Preservation
Longitudinal Joint Construction Strategies

35. Pavement Construction
TREND: Longitudinal Joint Construction Strategies to Improve Life of Joints
ODOT Supplemental Specification 806
Void Reducing Asphalt Membranes (VRAM)

36. Longitudinal Joint Construction Strategies
ODOT Supplemental Specification 806
March 2015 ODOT began piloting a new joint specification for multi-lane highways.
The specification significantly raises the stakes for improved performance by instituting a requirement that cores be taken directly over the longitudinal joint and measured for density.
The presumption is that a lack of mix density is the reason for weak performance.

37. Longitudinal Joint Construction Strategies
Understanding the problem
Position roller to maximize compactive effort.
Lack of lateral support results in lesser compaction and lower joint density.
Overlap and setup height are critical to ensuring sufficient mix is under the roller to compact the joint.

38. Longitudinal Joint Construction Strategies
Understanding the problem
Correct setup of matching pass.
Without sufficient setup height the roller bridges from the matching pass to the first pass, leaving mix insufficiently compacted in this area.

39. Longitudinal Joint Construction Strategies
Supl. Spec. 806 encourages proper setup height and compactive effort by requiring joint density to be measured directly over the joint.
Acceptance is statistically based using percent within limits tolerances. PWL has the effect of improving uniform density by exacting heavy penalties for variation in test results. It has a way of getting a contractors’ attention.

40. Longitudinal Joint Construction Strategies

41. Longitudinal Joint Construction Strategies
Void Reducing Asphalt Membranes (VRAM)

42. Thank you ! Clifford Ursich, PE info@flexiblepavements.org
An association for the development, improvement and advancement of quality asphalt pavement construction.
Thank you !
Clifford Ursich, PE