1. How To Effectively Raise The Bar And Level The Playing Field
Balanced mix design
How To Effectively Raise The Bar And Level The Playing Field
TxAPA Membership Meeting 2018

2. Some Questions We Need to Ask Ourselves
Is going to SP without addressing performance the answer?
Is putting more general notes in the plans the answer?
Is disallowing modifiers like REOB and PPA without understanding binder quality the answer?
IS DOING THINGS THE WAY WE’VE ALWAYS DONE THEM THE ANSWER?

3. How Do We Incentivize For Better Designs
General Notes:
no RAP
no RAS
no double grade dump
minimum asphalt content
OT requirement for SP mixes
increase lab molded density for SP mixes
raise VMA
disallow gradation through the reference zone
gradation must stay below the reference zone
Is there a better way?

4. What is a Balanced Mix Design?
Optimize the mix to provide needed performance and balance between stability and durability.

5. Optimized Mix Design Approach – Specification
Material Selection
Optimize JMF
Mix Performance Evaluation
Workability
Gradation
Aggregates
Stability
Mixing
Binder, Modifiers & Additives
Binder Content
Durability
Compaction
Recycled Materials
Volumetrics
Adjustments
Segregation

6. Optimized Mix Design Approach – Specification
Material Selection
SAC, Frictional Properties
Source Properties
Aggregate Blending
Aggregates
ΔTc
MSCR
Blended binder must meet specified grade
Binder, Modifiers & Additives
COMPATIBILITY
No limits on recycled materials or binder ratios
Recycled Materials

7. Optimized Mix Design Approach – Framework
Optimize JMF
Some method to optimize the gradation
(Bailey Method)
Gradation
No minimum AC content
Binder Content
VMA
D/A Ratio
In-Place Air Voids
Volumetrics

8. Optimized Mix Design Approach – Specification
Mix Performance Evaluation
Stability
Durability
Adjustments
BALANCE

9. Hamburg Analysis for Stripping Susceptibility

12. Optimized Mix Design Approach – Specification
Workability
Temperature & WMA requirements
Mixing
Air Voids
Density Profiles
Compaction
Thermal Imaging System
Other placement tests
Segregation

13. Summary Integration of the new OT analysis procedure is underway
NCHRP study on BMD
NCAT Test Track in 2018
Ongoing Research
Binder Quality
Balanced Mix Design (Specification in early 2018)
Aggregate Quality related to performance
New Performance Tests being developed to quickly access rutting and cracking susceptibility of mixtures
New design tools

14. District Trials Rejuvenator Project BMD Trial
WICHITA FALLS
PARIS
ATLANTA
TYLER
DALLAS
LUFKIN
FORT WORTH
WACO
BRYAN
BEAUMONT
HOUSTON
YOAKUM
CORPUS
CHRISTI
PHARR
LAREDO
SAN ANTONIO
AUSTIN
BROWNWOOD
SAN ANGELO
EL PASO
ODESSA
AMARILLO
ABILENE
CHILDRESS
LUBBOCK
Rejuvenator Project
BMD Trial
As I had mentioned, we also have a few districts that have tried some form of this balanced mix design approach. Of these 4 test districts; San Angelo, Tyler, Houston, and Laredo, we actually have Raymond from the Laredo District to talk about their experiences with the BMD approach.

15. NCAT Track
One section designed traditionally. The other section designed using BMD.
To further explore this balanced mix design approach, TxDOT has internal research, joint research with Universities, projects in a few districts, and now we are about to get on the NCAT track at Auburn. The actual mixes types and material details still need to be decided, but we are planning on 2 sections. Both will be Superpave. One will be designed using the traditional design methodology, whereas the second will be designed using the balanced mix design approach. The most important detail about this is that both sections will experience the same level of traffic and both are on the straight away at the NCAT track.

16. What would a Balanced Mix Design specification look like?
Next Steps
What would a Balanced Mix Design specification look like?
What‘s In
Frictional properties for aggregate (SAC)
DTc (<6⁰ single PAV)
VMA (varies by mix type)
HWT (varies by binder grade)
Overlay Tester ( <0.5 CPR)
Performance Testing during production
What’s Out
Recycle limits
Recycled Binder Ratio limits
Additive restrictions – rejuvenators, etc.
Basic volumetrics

17. Questions?