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

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?

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?

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

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

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

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

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

Hamburg Analysis for Stripping Susceptibility

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

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

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.

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.

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

Questions?