At the California Asphalt Pavement Association (CalAPA) Spring “Technical Tune-Up” Educational Workshop held April 5, 2022 in Brea, a presentation titled, "Superpave Mix Design – What Agencies Need to Know" was delivered by
Dave Aver, QC Associate (ret), City of Santa Rosa.
In 2015, Caltrans adopted the “Superpave” mix design methodology for asphalt pavements. This session will
provide an overview of the Superpave method and provide the difference to the Hveem mix design methodology.
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
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
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
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
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.
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
Fabricate 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
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.