Implementation of Superpave at the County Level in Florida

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Implementation of Superpave at the County Level
in Florida
Jim Musselman Florida Department of Transportation
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Superpave

• What is Superpave and whered it come from?
• FDOT experience with Superpave
• Is it time to start using Superpave at the County
  level?
• Basic Recommendations suggestions
• Other issues
• QC 2000
• Friction Courses

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What is Superpave? Where did it come from?

• New asphalt mixture and binder
  system/specification
• Composed primarily of three parts
• 1) New mix design system (Superpave mix design)
• Replaces Marshall Mix Design (Developed in
  1940s)
• 2) New asphalt binder specification (Superpave
  binder)
• 3) New performance prediction and analysis system
  
• (Simple Performance Test)
• Originated in the SHRP Program of the late 80s
  early 90s

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Strategic Highway Research Program (SHRP)

• Established by Congress in 1987
• 5-Year, 150 Million Research Effort
• To Improve the Performance and Durability of Our
  Nations Roads and to Make Them Safer for Both
  Motorists and Highway Workers

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SUPERPAVE SUperior PERforming Asphalt PAVEments

• 50 Million Spent on Asphalt Research, 1987-1992
• Primary Objectives of Research
• Investigate Why Some Pavements Perform Well and
  Others Do Not
• Develop Tests and Specifications Which Will
  Better Predict Performance
• Superpave System Delivered in 1993

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Superpave Mix Design

• Goal
• aggregate skeleton - strength
• asphalt content - durability
• Composed of
• Superpave gyratory compactor (SGC)
• volumetric requirements (VMA, Air Voids, etc)
• additional aggregate requirements
• moisture susceptibility tests

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Superpave Mix Design (cont.)

• Function of the Design Traffic Level for the
  Project
• Expressed as Equivalent Single Axle Loads
  (ESALs)
• Currently Five Traffic Levels
• Traffic Level A Low Volume
• Traffic Level E High Volume

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67 kN 15,000 lb 0.48 ESAL
27 kN 6,000 lb 0.01 ESAL
0.49 ESALs


151 kN 34,000 lb 1.10
151 kN 34,000 lb 1.10
54 kN 12,000 lb 0.20
2.40 ESALs



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Note 19 When the estimated design traffic level
is between 3 and 10 million ESALs, the agency at
its discretion use Ndesign of 75. (FDOT used
this option TL C . FDOT Traffic Level D is 10
to lt30 million ESALs used on all interstates)
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Superpave Gyratory Compactor

• Marshall Hammer out
• Constant pressure (600 kPa)
• Constant Angle (1.25 degrees)
• Constant Speed (30 rpm)
• Better simulation of what happens to the mix than
  static drop hammer compaction.

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Superpave Gyratory Compactor
Gmm
Log Number of Gyrations
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Volumetric Properties

• Good laboratory indicator of how the asphalt mix
  will perform in the field
• Air Voids, VMA, VFA, Dust Proportion
• Higher traffic levels higher gyrations
• Higher gyrations require stronger aggregate
  skeleton to maintain volumetrics
• Higher quality aggregates
• Also tend to lower asphalt contents

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Superpave Aggregate Properties

• Consensus Properties
• coarse aggregate angularity (ASTM D 5821)
• fine aggregate angularity (AASHTO T 304)
• flat, elongated particles (ASTM D 4791)
• clay content (AASHTO T 176)
• Source Properties (FDOT Aggregate Control
  Program)
• toughness (LA Abrasion)
• soundness
• deleterious materials

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Superpave Gradations

• Gradation Controls
• Use 0.45 Power Chart with
• control points
• restricted zone
• AASHTO Nominal Maximum Aggregate sizes
• 4.75 mm (AASHTO Ballot)
• 9.5 mm
• 12.5 mm
• 19.0 mm
• 25.0 mm
• 37.5 mm

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Superpave Gradations
Percent Passing
100
max density line
restricted zone
max size
nom max size
control point
0
.075 .3 2.36 4.75 9.5
12.5 19.0
Sieve Size, mm (raised to 0.45 power)
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Superpave Gradations
Percent Passing
Design Aggr Structure
100
0
.075 .3 2.36 4.75 9.5
12.5 19.0
Sieve Size, mm (raised to 0.45 power)
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Superpave Gradations

• Coarse Mixes Below the Restricted Zone
• Predominantly coarse aggregate
• Higher density requirement
• Pack a lunch!
• Fine Mixes Above the Restricted Zone
• Predominantly fine aggregate
• Similar to FDOT Type S

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SP-12.5 Fine
S-I
SP-12.5 Coarse
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(No Transcript)
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Moisture Susceptibility Testing

• Tests for the Potential that a Mix Will Be
  Susceptible to Moisture Damage (Stripping)

Wet Dry
TSR x 100 ? 85
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Superpave Asphalt Binder Specification

• Grading System Based on Climate

PG 67-22
Performance Grade
Average 7-day max pavement design temp
Min pavement design temp
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Binder Testing
Rotational Viscometer (RV)
Direct Tension Tester (DTT)
Dynamic Shear Rheometer (DSR)
Bending Beam Rheometer (BBR)
Pavement Temperature, C
Low Temp Cracking
Fatigue Cracking
Rutting
Construction
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Examples of PG Grading System

• Florida PG 67-22 (153 F to -8 F)
• Old AC-30
• Minnesota PG 58-34 (136 F to -29 F)
• Arizona PG 70-10 (158 F to 14 F)

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Performance Prediction and Analysis

• Simple Performance Test
• Under development thru NCHRP 9-19 (Arizona State
  Matt Witczak PI)
• Looking at mixture stiffness and fracture
  resistance (rutting and cracking)
• Triaxial Dynamic (Complex) Modulus
• Tied into the AASHTO 2002 Pavement Design Guide
• Next few yearsstay tuned

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So Whats This All Mean in English?

• Mix Design (In the Lab)
• Different way to design the asphalt mix
• Composed of
• Gyratory compactor
• Selected aggregate requirements
• Moisture susceptibility tests
• Five Traffic Levels (low to high)
• Coarse graded or fine graded

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Old vs. New

• Old
• Type S-I, S-II, and S-III (All fine graded)
• 50 Blow Marshall
• Same mix parking lot or I-75
• 3 combinations
• New
• Type SP-9.5, SP-12.5 and SP-19.0 (Fine or coarse
  graded)
• Five Traffic Levels
• 15 combinations

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Anticipated Performance

• More resistant to rutting
• Gyratory compactor mix has to be stronger
• Angular materials
• Stronger asphalt binders
• Better Quality Control
• More resistant to cracking
• Increased density better durability
• Higher quality asphalt binders

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Performance Data Where is FDOT today?

• Total State Highway System 36,567 lane miles
• Rutting 572.1 deficient miles (1.6)
• Ride 1556.0 deficient miles (4.3)
• Cracking 6702.1 deficient miles (18.3)

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Brief History of Superpave in Florida

• 1995 one project (US-301 Hillsborough Co.)
• 1996 ten projects mostly north Florida
  Interstate
• Supplemental Agreement
• Used existing construction specifications
• Late 1996 Noticed permeability problems
• Started weeping (Pavement FDOT)
• 1996/1997 Permeability/Density study

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Permeable Pavement I-10 Suwannee County
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Permeability/Density Relationship
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Brief History of Superpave in Florida (contd)

• 1997 Specification changes
• Increased density level (coarse mixes)
• Increased lift thicknesses (coarse mixes)
• Dropped nuclear gauges went to cores
• Added a density bonus
• 1998 Beginning designing all projects as
  Superpave
• 1997 2000
• Approximately 250 projects
• Most went well
• Some were painful
• 2001 - 2002
• Fairly smooth sailing!

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FDOT Superpave RequirementsSection 334(July
2001 version)

• Three mix types
• SP-9.5 (3/8)
• SP-12.5 (1/2)
• SP-19.0 (3/4)
• Five Traffic Levels (A E)
• Two Gradation Types
• Coarse (Traffic Levels D E)
• Fine (Traffic Levels A, B, C)

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Traffic Levels
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FDOT Superpave (contd)

• Contractor may substitute one traffic level
  higher ie., TL-C for TL-B
• Traffic Levels A, B, C
• Fine or coarse graded
• Contractors option (typically fine)
• Must meet lift thickness requirements
• Similar to Type S mixes
• Traffic Levels D E
• Mandatory Coarse Graded

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Lift Thicknesses (Fine Mixes)
Type SP-9.5 0.75 - 1.25 in. Type SP-12.5 1.25 -
2.50 in. Type SP-19.0 2.00 - 2.75 in.
Basically the same as Type S
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Lift Thicknesses (Coarse Mixes)
Type SP-9.5 1.50 - 2.00 in. Type SP-12.5 2.00
- 3.00 in. Type SP-19.0 3.00 - 3.50 in.
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Coarse graded SP-19.0 mix
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Basic Testing Requirements(Plant)

• Asphalt Content and Gradation
• Acceptance (FDOT) - 1/1000 tons
• Quality Control (Contractor) - 1/day
• Target approved mix design
• Payment based on binder content, No. 8 200
  sieves
• Ignition oven (FM 5-563 and FM 1-T 030)
• Air voids of the mix during production (new)
• Quality Control requirement 1/1000 tons
• Important for rutting resistance
• Gyratory compactor max specific gravity (AASHTO
  TP-4 and FM 1-T 209)

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Basic Testing Requirements(Roadway)

• Density
• Acceptance 6 diameter cores 1/1000 ft
• Targets
• 92.0 max sp. gr. (fine mixes)
• 93.5 max. sp. gr. (coarse mixes)
• Added bonus provision
• Quality Control Nuclear gauge
• Smoothness
• 15 ft. rolling straightedge
• Acceptance and QC

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What Has FDOT Learned?

• Performance has been excellent so far
• Coarse mixes are exceptionally difficult!
• Permeable
• Require higher density
• Require thicker lifts
• Require greater compactive effort
• Vibration
• Nuclear density gauge not very accurate
• Bonus system works well
• Carrot vs. Stick

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What Has FDOT Learned?

• Contractor can handle additional testing duties
• Probably better than FDOT!
• Superpave mixes
• Less sand, increased manufactured aggregates
• Less RAP
• Greater cost (45/ton)
• Experience is the best teacher!
• Walk before you run.

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Is it time to start using it at the county level?

• My recommendation is to let FDOT sort out the
  problems before you implement Superpave.
• -- Jim Musselman
• FACERS Meeting
• November 18, 1998

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Is it time to start using it at the county level?

• Yes!

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Why?

• Most of the problems have been sorted out
• Issued over 1900 mix designs
• 500 projects
• 15 million tons
• Excellent performance
• Contractors have experience
• Strength in uniformity
• Consistent with FDOT CTQP Training
• Uniform language between counties
• It makes life simpler for Contractors
• Its a better asphalt system!

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Recommendations

• Use FDOT 334 Superpave Specification -- July
  2001 Supplemental Version
• 2000 Specification Book is different.
• Traffic Levels
• A for Light Duty,
• B for Medium Duty,
• C for Heavier Duty.
• Avoid coarse mixes - stay with fine-graded mixes,
  save many headaches, live longer!
• Bigger/stronger is not necessarily better

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Recommendations (contd)

• Extreme loading conditions consider fine graded
  Traffic Level D mix with a modified binder (PG
  76-22)
• Cost typically increases for higher type mixes.
• PG 76-22 additional 10/ton
• Use.
• SP-9.5 instead of S-III
• SP-12.5 instead of S-I
• May want to consider substitution of 1 TL higher
  
• Be careful, though.
• Stay with your current density requirement.

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Recommendations (contd)

• Discuss with local asphalt contractors first
• Walk before you run
• Dont be afraid to ask for help
• Jim Warren Asphalt Contractors Association
• jwarren_at_acaf.org
• [phone]
• Bob Boyer Asphalt Institute
• asphaltnfl_at_aol.com
• [phone]
• Jim Musselman Florida Dept. of Transportation
• Jim.musselman_at_dot.state.fl.us
• [phone]

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QC 2000

• Changes in 23 CFR 637 Part B
• Requires Qualified Personnel (CTQP)
• Requires Qualified Laboratories (LQP)
• Accredited Central Lab
• AASHTO Accreditation Program
• Independent Assurance Program
• Systems based
• Option to use Contractor Quality Control data for
  acceptance
• FDOT calls this QC 2000 (now Contractor Quality
  Control)

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In a Nutshell..

• Payment based on Contractors (Quality Control)
  test data
• FDOT runs verification tests at a lesser
  frequency
• Payment is based on density on the roadway and
  air voids, asphalt content and gradation at the
  plant.
• Uses Percent Within Limits (PWL) statistically
  based specifications
• Begins with July 2002 letting
• Consistent with FDOT staff reduction (25)
• Might be applicable to counties
• Specification refresher course
• Stay tuned

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Friction Courses

• Utilize polish resistant aggregate
• Oolitic limestone or granite
• All roadways with AADT gt3,000
• FC-2 FC-5
• Open graded mixes minimize hydroplaning
• Multi-lane roadway w/speed limit gt45 mph
• FC-3 FC-6 Dense graded friction courses
• FC-3 (S-III) sunsetting
• FC-6 (SP-12.5 TL-C) - Replacement
• All friction courses contain asphalt rubber
• Liability?

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SR-16 Bradford County
With ARB
Without ARB
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In Conclusion
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Thank You!