Dave Aver, City of Santa Rosa, and Greg Reader, George Reed Inc., deliver a presentation on Superpave Mix Designs, test methods and how the results are incorporated in the final Job Mix Formula. Presentation delivered on Nov. 7, 2019 at the California Asphalt Pavement Association Fall Asphalt Pavement Conference in Sacramento, Calif.

1. Superpave Mix Designs
Developing the JMF

2. Introduction
• Classification of Asphalt Mixtures
• Objectives of the Mix Design
• Materials Selection and classification
• Laboratory Trials
• Volumetric Analysis and finding OBC (Optimum Binder
Content)
• Moisture Sensitivity and Rutting
• Finalize the JMF

3. Asphalt Mixture Classifications

4. Asphalt Mixture Classifications
• Dense Graded
• Gap-Graded or Stone Matrix Asphalt (SMA)
• Open Graded Friction Course

5. Asphalt Mixture Classifications

6. Dense Graded Asphalt Mixture
• Most Commonly used mixtures
• Can be base course, Intermediate course or surface course.
• Proper thickness of layer vs NMAS size 3:1

7. Gap-Graded or Stone Matrix Asphalt (SMA)
• Caltrans Minimum Binder content of 7.5% TMM
• Improved Skid resistance
• Decreased road noise
• Wearing course

8. Open Graded Friction Course
• Wearing course
• Improved Skid Resistance
• Reduces spray from rain on the roadway
• 10%+ Air Void Structure = High Permeability
• Different Design Methodology based upon drain down of binder

9. Objective of the Mix Design
What do we want the mixture to do?

10. Ultimate Objective
• Find the most economical and best performing combination of
aggregate and binder content.
• Find the aggregate structure that can carry the most amount of
binder while resisting permanent deformation.
• Durability vs Stability = BMD Cracking vs Rutting <- Future of our
Industry
• Aggregates are the skeleton – Approximately 92% to 96% of the
mixture.
• Binder is approximately 4% to 8% of the mixture

11. Objectives of the Mix Design
• Resistance to Permanent Deformation aka Stability
• Fatigue Resistance
• Low Temperature Cracking
• Moisture Resistance
• Durability
• Skid Resistance
• Workability

12. Resistance to Permanent Deformation
• Roadway Stresses
• Speak about the picture of rutted roadway

13. Fatigue Resistance
• Speak about different causes of the failure type ie subgrade
failure vs mix too brittle

14. Low Temperature Cracking
What is the role of PG binders?
Climatic regions

15. Materials Selection and Classification

16. Consensus Aggregate Properties
• Aggregate properties that are required for a good pavement,
regardless of specific source i.e. particle shape and clay content
(SE).
• Cubical vs Marbles
• Different requirements depending on traffic levels and which layer
within the structural section

17. Consensus Aggregate Properties
• Coarse Aggregate Angularity
• Fine Aggregate Angularity
• Flat and Elongated
• Clay Content (Sand Equivalent)

18. Consensus Aggregate Properties

19. Source Aggregate Properties
• These are specific to individual source and geology
• Can have significant impact on mixture performace
• Toughness
• LA Abrasion
• Micro-Deval
• Soundness – Sodium Sulfate or Magnesium Sulfate
• Deleterious Materials – Clay Lumps and Friable Particles
• Gradations of each aggregate size fraction
• Specific Gravity

20. Laboratory Trials and
Volumetrics

21. Evaluate Multiple Mix Trials
• Select Trial Gradations based upon blending of source aggregates
to meet the intended specification or Historical Source Data and
information.
• Estimate Trial OBC for Single Point Volumetric Analysis and
comparison.
• Lab Batch, cure and compact, test for physical properties.

22. Trial Mix Comparison
Sieve Size Trial Mix 1 Trial Mix 2 Trial Mix 3 Design TV’s
3/4” 100 100 100 100
1/2” 97 95 98 95-98 X +/- 5
3/8” 83 73 94 72-95 X +/- 5
#4 59 53 68 52-69 X +/- 5
#8 40 36 54 35-55 X +/- 5
#16 27 25 39
#30 19 16 29 15-30 X +/- 4
#50 13 10 20
#100 9 6 13
#200 5.2 3.0 7.5 2-8 X +/- 2
Est. Trial AC(TWM) 4.9% 4.6% 5.3%

23. Trail Mix Comparison – ½” HMA-SP – Caltrans
2018 Standard Specs – Design TV’s

24. Trial Mix Comparison - Volumetrics
Physical Property Trial Mix 1 Trial Mix 2 Trial Mix 3 Specification
AC Content (TWM) 4.9% 4.6% 5.3% N/A
Agg Blend SpGr 2.656 2.664 2.642 N/A
Air Voids 4.7% 2.7% 5.8% 4.0 +/- 1.5
VMA 15.2 13.4 16.8 14.5 – 17.5
VFA 69.0 65.7 68.5 65 – 75 (MS-2)
Dust Proportion 1.14 .66 1.55 0.6 – 1.3

25. Volumetric Analysis and Finding OBC
Trial Mix #1

26. Volumetric Analysis – Trial Mix 1 – Aggregate
Blend
AGGREGATE GRADATION
Bin 1 2 3 4 5 6 RAP LIME
Combined Gradation (JMF TV)
Material Size Man Sand Rock Dust 3/8" 1/2" 3/4" -3/8"
Bin % 10 37 21 20 12 100
Sieve Size % PASSING
2" 100 100 100 100 100 100 100
1 1/2" 100 100 100 100 100 100 100
1" 100 100 100 100 100 100 100
3/4" 100 100 100 100 87.8 100 100
1/2" 100 100 99.9 86.4 19.2 100 97
3/8" 100 100 92.3 22 4 99.1 83
No. 4
99.7 95.9 20.2 3.1 1.8 74.5 59
No. 8
79.2 65.3 4.4 2 1.4 54 40
No. 16
54.2 42.7 3.9 1.9 1.1 40.6 27
No. 30
35.5 29.3 3.3 1.7 0.9 30.7 19
No. 50
18.5 20 2.7 1.6 0.7 21.7 13
No. 100
8.6 14.3 2 1.5 0.5 14.2 9
No. 200
3.4 8.7 1.43 1.31 0.42 9.28 5.2

27. Volumetric Analysis
HOT MIX ASPHALT DESIGN DATA
Quality Characteristic Test Method ABR (Corrected) - 0.5% ABR (Corrected) ABR (Corrected) + 0.5% ABR (Corrected) + 1.0%
Pb Asphalt binder content (%) by TWM
AASHTO T 308
Method A 4.4 4.9 5.4 5.9
Gmb Briquette specific gravity AASHTO T 275 2.355 2.368 2.383 2.392
Gmm Maximum specific gravity AASHTO T 209 2.502 2.485 2.469 2.452
Va Air voids content (%)
SP-2
Asphalt Mixtures 5.9 4.7 3.5 2.4
VMA Voids in Mineral Aggregate (VMA)
SP-2
Asphalt Mixtures 15.2 15.2 15.1 15.3
GseR Effective specific gravity of RAP aggregate
SP-2
Asphalt Mixtures 2.715 2.715 2.715 2.715
DP Dust Proportion
SP-2
Asphalt Mixtures 1.28 1.14 1.04 0.95
Gse Effective specific gravity of aggregate
SP-2
Asphalt Mixtures 2.677 2.679 2.682 2.683
VFA Voids Filled with Asphalt (VFA)
SP-2
Asphalt Mixtures 61.4 69.0 77.0 84.0
Pbe
Effective Asphalt Content (% TMM)
SP-2
Asphalt Mixtures
4.10 4.58 5.04 5.53
Pba
Absorbed Asphalt (%TMA)
SP-2
Asphalt Mixtures
0.31 0.34 0.38 0.40

28. Volumetric Analysis

29. Volumetric Analysis
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
4.4 4.9 5.4 5.9
%AirVoids
% Binder Content
AIR VOIDS

30. Volumetric Analysis

31. Moisture Sensitvity and Rutting
Performance Tests at Optimum Binder Content

32. Moisture Resistance
• Wet/Dry = %
• Caltrans looks at Retained Strength rather than TSR Wet/Dry
• Wet = 70 PSI
• Dry = 100 PSI Min - 300 PSI Max
• Different treatment methodologies based upon specifications and
aggregate qualities.

33. Moisture Sensitivity – AASHTO T283
• Fabricate Briquettes in 2 sets of equal air void content 7.0% +/-
0.5%
• Saturate Wet Group to 70% - 80% of the volume of air voids.
• Freeze Wet group
• Trying to destroy the bond of oil to aggregate with moisture
• Minimum Wet Strength of 70 PSI
• Dry Strength has a range of 100 psi to 300 psi
• Ratio of wet to dry strength

34. AASHTO T324 Hamburg Wheel Track
• Frabricate Samples in 2 sets of equal air voids
• 7.0% +/- 0.5% Air Voids
• Test Temperature based upon PG Grade of Mix
• Maximum Rut Depth of 12.5mm
• Number of Cycles dependent upon type of mix classification,
Dense Graded vs RHMA-G

35. AASTHO T324 – Hamburg Wheel Track

36. AASTHO T324 – Hamburg Wheel Track
Passing Failing

37. Finalize the JMF

38. Caltrans CEM 3511, 3512, and 3513
• Caltrans form CEM 3511 is your JMF
• It shows the combined gradation of the mix plus the tolerance
band.
• It identifies the OBC of the JMF
• The source of all the constituent products
• Project information
• Filled out by the Contractor/Producer/Lab of Record
• Checked by Project RE for compliance with project specials and
standard specifications.

39. Caltrans CEM 3511, 3512, and 3513
• Caltrans form CEM 3512 is Mix Design Data sheets
• Includes all of the physical properties of the constituent products
used to develop the mix design.
• All of the volumetric testing of the mix design at the chosen
proportions.
• Lab verification of OBC along with performance tests at Optimum
Binder Content that was selected.
• Volumetric Charts for analysis of Lab Design

40. Caltrans CEM 3511, 3512, and 3513
• Caltrans for CEM 3513 – GOLDEN TICKET to Willie Wonka's Factory!
• This is your mix approval from Caltrans
• You obtain this by producing the JMF through the plant and
sampling with a Caltrans District lab.
• The District lab will test for the volumetric properties of the
aggregates, the HMA/WMA/RHMA, the binder used, and the
performance tests TSR and Hamburg to ensure compliance with
the specification and the JMF submitted.

41. Questions and Discussion