Dense Graded Mixes

John Christensen Quality Manager October 13, 2015

Superpave – A History

History

Why? 1970s – 1980s Years of Neglect -> Deteriorated

Highways Pavements Not Lasting as Long as

Expected (All Types!) In Asphalt Changes Due to Oil Embargo Idea of a Focused Research Program

1982 – 4 Year 58 Billion Highway Bill Needs Outpace Resources Innovation Through Targeted Research

New Approach 150 Million 5 Year Program of Focused

Research Sponsored by FHWA & Conducted by

TRB

History

Strategic Highway Research Program SHRP – Accepted by FHWA and

AASHTO 0.25% Earmark of Federal Highway

Funds in 1987 through 1991 50 Million for Asphalt In 5 Projects Superior Performing Asphalt Pavements Superpave

History

Superpave

Performance Graded (PG) Asphalt Other Binder Related Products Mix Design System and Software Three Levels of Design Superpave Gyratory Compactor

Origins from TX Gyratory via Army & France Aggregate and Asphalt Mix Specs

Superpave

Gyrations Have Dropped Initial 80 – 110+ Now 35 – 50

PG + Specifications Added Elastic Recovery

Performance Testing Has Changed From SST to Rut Testing, Overlay & SPT

Gone From Coarse to Fine

Superpave Changes

What Superpave is Not! Aggregate Properties Are Similar

5% Lower on Soundness and LAR Crushed Face % is the Same

• 15 of 98 Aggregate Sources Affected

What Is Superpave Now?

What Superpave is Not

Dense Graded Gap Graded

Open Graded

What Superpave is Not

Dense

Gap

Open

What Superpave is Not

Not a Radical Change in Mix 344 is a Dense Graded Mix

Dense Graded Mix

Dense Graded Mixes

Dense Graded Mixes

Nominal Maximum Size (B, C, D etc) One Sieve Larger than the 1st Sieve to

Retain More than 10% Max Sieve Size One Sieve Larger than Nominal

B or C???

↓ Max Size - ↑ VMA More Asphalt!!!

VMA

Size 1 in 3/4 in 1/2 in 1/2 - 3/8 3/8 - #4 25mm 19mm 12.5mm 9.5mmProperty A B C D F A B C D

VMA 12.0 13.0 14.0 15.0 16.0 13 14 15 16Va

HamburgOverlay -- -- -- -- -- -- -- -- --

In-Place Va

4.010 - 20k

<7.5 (92.5)

Dense - 344 SHRPDense - 341 TGC

<8.5 (91.5)

3.5*10 - 20k

More Asphalt

Thank You – Robert Lee

Can Be Used on Medium to High Volume Roads Yes, But It Can Be Used Anywhere

Binder Content Can Be Adjusted by Altering the Ndes Level Yes, Absolutely

Stone on Stone Contact Yes and No

What’s Being Said

Stone on Stone Dense Graded

Stone on Stone

Stone on Stone??

Coarse Surface Texture Can Be Beneficial for Wet Weather Traction Sure, If Designed as Dense – Coarse

Gradation Not As Gap Graded as SMA Yes, Degree Varies

More Susceptible to Cracking and Water Infiltration Than SMA Yes and No

What’s Being Said

Increased VMA Get Away From The Max Density Line

Heights vs Gyrations Stability of Mix May be Determined

During Compaction in Superpave Higher Asphalt Contents If Not, Probably Some Thing Wrong

Things to Look For

49 Other States Can’t Be Wrong!!!

I Love Texas

Thank You!