Long-Life PavementsConcepts and Lab Testing

Pre-bid MeetingSolano 80 04-4A0104

James M. SignoreOakland, CA9/14/2012

Presentation Overview• Long Life Pavement (LLP)

What it is? What are the benefits?

• Recent California Experience I-5 in Red Bluff and Weed

• What to Anticipate Specimen Preparation & Lab

Testing

Long Life Pavement – What is it?

• Design Life 40+ years• Bottom-Up Design and

Construction• Renewable Pavement Surface

• High Rutting and Cracking Resistance

• Smooth and Safe Driving Surface

Long Life Pavement – What is it?

RepeatedBending

Leads toFatigue Cracking

RepeatedDeformation

Leads toRutting

HMA

Base

Subgrade

Long Life Pavement What are the Benefits?

• Lower Life Cycle Cost Better Use of Resources Low Incremental Costs for

Surface Renewal• Lower User Delay Cost

Fewer or Shorter Work Zone Periods for Future Maintenance

Long Life Pavements in the US

Structural Section – SOLANO 80

OGFCHMA w/ 15% Max. RAP

(PG 64-28PM)

HMA w/ 25% RAP (PG 64-10)

Geosynthetic Interlayer

Existing Pavement

2 Mix Designs

!!!

Leveling Course

Project Considerations• Materials Selection &

Testing• Structural Design• Specs• Construction

Recent Projects• Weed I-5 D2• Red Bluff I-5 D2

Structural Section – Weed

HMA w/ 15% Max. RAP (PG 64-28PM)

HMA w/ 25% RAP (PG 64-16)

HMA w/ 25% RAP (PG 64-16) (leveling

course)

2 Mix Designs

!!!NTS

Existing Cracked & Seated PCC or HMA

SAMI*

* Asphalt Rubber Seal Coat

Structural Section – Red Bluff

OGFCHMA w/ 15% Max. RAP

(PG 64-28PM)

HMA w/ 25% RAP (PG 64-10)

HMA-Rich Bottom (PG 64-10)

CTB-Existing

Agg Subbase & Subgrade

3 Mix Designs

!!!NTS

What to Anticipate Solano 80

Mix Design based on “Mechanistic” Lab

Testing• Hveem (CT 366) • Shear Testing (T-320)• Fatigue Testing (T-321)• Hamburg WT (T-324)• Mix must meet performance

requirements in Special Provisions

Modified (Mechanistic) Mix Design Process

Establish target binder content with Hveem (CT 366)

Performance Testing 1. Shear testing at target binder content ±

X2. Select design binder content based on

shear test results3. At design binder content

Fatigue Hamburg Wheel Track (HWT)

Modified Mix Design Flow Chart

HVEEM Mix Design for Target “OBCH”

SHEAR Testing to determine “OBCS” 3 specimens prepared and tested at HBC + 3 more each @ +/- X Total of 9 specimens per mix (3 x 3BC)

SELECT OBC based on SHEAR test resultsFATIGUE Testing @ OBCSFlexural Fatigue – 20C, 2 levels of strain (bending) – 6 Total (6 x 1BC)Flexural Stiffness - 20C & 30C – 6 Total (6 x 1BC)Spare beams recommended – 14 Total if possible

HWTD testing @ SOBC – 1 Test, 50C, 4 cores

If Fail Te

sting

Modified Mix Design Materials and Time

HVEEM to determine target BCSHEAR Cores are prepared firstTesting performed to determine “OBCS”Requires 3 x 3BC Cores (6 in. diameter x 2 in. tall)Cores are prepared with Rolling Wheel Compaction (RW)

OBC based on SHEAR test resultsFATIGUE Beams prepared after OBCS determined6 Flexural Fatigue (2 in. tall x 2.5 in. wide x 15 in. long)6 Flexural Stiffness (2 in. tall x 2.5 in. wide x 15 in. long)Beams are prepared with Rolling Wheel Compaction (RW)HWTD TestingCores are 6 in. diameter x 2.5 in. tall1 Test with 4 cores prepared with Superpave Gyratory (SGC)

Time Per Mix

3 wks

6 wks

1 wk

Quantity of Materials Per Mix DesignCaltrans Project

Typical Long LifeHveem Mix Design(includes CT 371)

5 gal binder~500 lb aggregate

5 gal binder~500 lb aggregate

Performance Testing

(includes specimen fabrication)

10 gal binder~ 1,200 lb aggregate(Plant Mix Equivalent)

ShearFatigue

Hamburg

SPECIMEN FABRICATIONShear & Fatigue

Caltrans LLP – AC2 “Sample Preparation Design and Testing for Long Life Hot Mix Asphalt Pavements”

AASHTO PP3-94 Rolling Wheel Compaction

SPECIMEN FABRICATIONShear & Fatigue

• Beams and Cores cut from HMA Ingot (Example)

SPECIMEN FABRICATIONShear & Fatigue

• Beams and Cores cut from HMA Ingot

SPECIMEN FABRICATIONShear & Fatigue

SPECIMEN FABRICATIONShear & Fatigue

SPECIMEN FABRICATIONShear & Fatigue

FATIGUE BEAMS

FATIGUE BEAMS

Protection of Beams in transit/shipping is essential – no bending or flexing of packaging

SPECIMEN FABRICATIONHamburg

• Superpave Gyratory Compactor

SPECIMEN FABRICATIONHamburg

• Hamburg Testing Fixture – cut ‘flat’ on cores

LABORATORY TESTING• SHEAR TESTING• FATIGUE TESTING• HAMBURG TESTING

SHEAR TESTING

SHEAR TESTING

SHEAR CORE – Post TestNote Shear or “Slope” of specimen

SHEAR TESTING

Perm

anen

t She

ar S

train

(PSS

) “R

uttin

g”

Cycles

Spec Minimum to pass

5% PSS

FATIGUE TESTING

FATIGUE TESTINGFl

exur

al S

tiffne

ss (F

S)

Cycles (millions)

Spec Minimum to pass

50% FS (typical)

Not to scale

HAMBURG WHEEL TRACKING (Moisture

Sensitivity)

HAMBURG WHEEL TRACKING (Moisture

Sensitivity)

Rut

Cycles

Theoretical

“Rut Resistant”

HAMBURG WHEEL TRACKING (Moisture

Sensitivity)

SPECIFICATIONS and Testing Variability

 Design Parameters

 Test

Method

 Sample

Air Voids

Requirement 

 HMA (15% Max RAP, Long

Life)

 HMA (25% RAP, Long Life)

 

Permanent deformation (min. stress repetitions)

 AASHTO

T-320Modified

 3% +/-0.3%

 360,000

 360,000

 

 Beam Stiffness (psi)

At 20° C and 10 HzAt 30° C and 10 Hz

 AASHTO T-321Modified

 6% +/-0.3%

 415,000 to 486,000

220,000 (min)

 870,000 to 1,000,000

--

 

 Fatigue (min. repetitions)

At 400x10-6 in./in. strainAt 200x10-6 in./in. strain

 AASHTO T-321Modified

 6% +/-0.3%

 23,000,000345,000,000

 25,000950,000

 

Moisture Sensitivity(min. repetitions)

AASHTOT-324

Modified

 7% +/-

1%

  12,000

 12,000

 

SPECIFICATIONS and Testing Variability

Specifications for Shear and Fatigue are statistically based

The specifications are based on the lowest 5 percentile expected from testing

Comparable mixes should pass this specification 95 out of 100 times

Limits are set low to accommodate large testing variability present in Shear and Fatigue Testing

Stabilometer Variability

Based on these numbers, the 5th percentile is about 80% of the average (mean)

Questions?

Acknowledgements:Rita Leahy, Professor Monismith, Caltrans

Staff