cliff ashcroft
DESCRIPTION
Presentation on Rubber Pavements presented at the CalAPA Fall Asphalt Pavement Conference Oct. 24, 2013 in Sacramento, Calif.TRANSCRIPT
CalAPA ConferenceSacramento, CAOctober 24, 2013
Asphalt Rubber
Revolution
By
Cliff Ashcroft
President
Rubber Pavements Association
If you think you know everything about asphalt rubber pavements?
Think again!
Major changes in California
regarding AR pavements.
Asphalt Rubber History
1960 1970 1980 1990 2000
Asphalt Rubber Chip Seal (SAM)
A R Chip Seal Interlayer (SAMI)
Open-Graded Hot Mix
Dense-Graded Hot Mix
Gap-GradedHot Mix
2010
AZ
CA
Definition of Asphalt Rubber
Uses a minimum of 20 +/- 2 % crumb rubberUses 10 mesh (2mm) crumb rubberReacts/interacts crumb rubber for a minimum of 45
min. at elevated temperaturesModifies original properties of asphalt cementOnly crumb rubber binder with an ASTM definition
and extensive research background
What is Asphalt Rubber Binder?
It is a NON PRORIATARY recipe specificationA blend of recycled tire rubber, asphalt and extender
oilReacted at high temperatures to significantly modify
the asphaltResult is a unique product – asphalt rubber binder AR has a 45 year proven performance history
How is Asphalt Rubber produced?
Specialized equipment and binder blended on-site
High shear blender for mixing crumb rubber with asphalt and modifier
Reaction tank with adequate agitation to assure proper reaction
All materials are metered-in
Asphalt Rubber Blending Schematic
Crumb Rubber
Asphalt Storage Tank
Heat TankHigh Shear
Blender
Reaction Vessel
Binder Pumped to Plant
Heater Blender
Rubber Weigh Hopper
Reaction Vessel
Reaction VesselAugers and
Direct Fire Heating
Computer ControlledAccurately Measures
Materials During Production
Components of the Asphalt Rubber Binder
Crumb rubber modifier (CRM)Asphalt cementAsphalt modifier
Paving Asphalt
PG 64-16 and PG 58-22 asphalt (80 +/- 2 %)Conform to Section 92 “Asphalts” of the Standard Specifications
Asphalt Rubber Binder Properties
Cone penetrationResilienceField softening pointViscosity
Factors Affecting Binder Properties
Asphalt cementAmount of crumb rubberGradation of crumb rubberReaction time and temperature
20 % CRM
High Viscosity
Asphalt Rubber
Conv. & Other Mod. Asphalts
22,937,600 rubber particles per ton of mix help fight cracking
13 Year Old Asphalt Rubber Chip Seal
Key to asphalt rubber is high viscosity and reduced aging properties.
Where have Asphalt Rubber strategies been used successfully?
AR Hot Mix
AR Chip Seals
22 yrs. old 15 yrs. old
AR Multi-layer Strategies
20 yrs. old 10 yrs. old
AR Cape Seals
Asphalt Rubber Specifications
Rubberized hot mix asphaltType “G”Type “O”Type “O-HB”
Asphalt rubber chip sealAsphalt rubber cape sealMulti-layer systems
What are the major changes in California (Caltrans)
regarding specifications for AR pavements?
Changes in AR Pavements in California
Changes in Caltrans specificationsNew Superpave specificationsSome changes made to Section 39
Changes in testing requirementsGyratory compactorHamburg wheel tracking Moisture sensitivity, minimum dry and wet strengths
Changes in acceptance requirementsChanges in measuring
MPQP
Changes in Specifications
New Superpave specification developed by Caltrans with major changes to RHMA requirements (will be finalized in July 2014)
Some changes also made to Section 39 in standard specifications
New specs have new requirements for RHMA Laboratory mix designField mix acceptance
Changes in Mix Design Testing
Increase in minimum binder content to 7.5 % by total weight of mix (move from min. 7.0% to 8.1% by dry weight of aggregate)
However, no change in the minimum void requirements or aggregate grading requirements - makes this especially difficult
Changes in Mix Design TestingAASHTO T-312 gyratory compactor now required for
compaction during mix design (National Standard from SHRP)
Move away from Hveem kneading compactorNew compaction method in California for all mixes,
labs have very little experienceContractor’s/labs need to familiarize themselves with
new methodNew method allows variable compaction to achieve
mix voids requirements (N design 50-150 gyrations and can increase pressure to 825 kPa)
Gyratory Compactor
Changes in Mix Design TestingAASHTO T-324 (modified) Hamburg testing requirementMaximum rut depth requirement of 0.5 inch on field produced mixesRut depth - minimum number of passes (15,000 to
25,000) depending on type and grade of asphalt (PG 58, 64 or 70)
Inflection point - minimum number of passes (10,000 to 15,000) depending on type on grade of asphalt (PG 58, 64 or 70)
Hamburg Wheel Tracking Device
Changes in Mix Design Testing
AASHTO T-283 (modified) Moisture Induced Damage Test requirementMinimum dry strength of 110 psi on field produced material
Minimum wet strength of 84 psi on field produced material
Freeze thaw cycle required
Changes in AcceptanceBinder content tolerance changed from +/- 0.5% to - 0.4% +0.5%
In-place mix density requirements changed from 91-97% relative density to 92-97%
Air voids requirement in field changed from +/- 2% to +/- 1.5%
Changes in MeasuringNew requirements for AR in the Materials Plant Quality Program (MPQP)New requirements for weights and measures for AR blending and production
New recording requirementsNew reporting requirementsAsphalt rubber MPQP requirements are different from other types of binder production
Use of Warm Mix Technology in RHMA
Contractor now has the option to use warm mix technology (WMA) in asphalt rubber hot mix.
WMA will help offset low temperature placement problems
WMA will aid in the compaction process
WMA Benefits to ContractorReduced worker exposure to fumesDecreased emissions at HMA plantSavings in energyEasier permittingExtended haul distancesLower odor/fumesImproved thin lift capabilitiesExpanded season
What to Expect in the Future Performance Grade (PG) AR specification
Sub-Task Group formed under CT/Industry Rock Products Committee to work on development of a PG specification for asphalt rubber - 3 year work plan
Draft specification developed by IndustryInitial round robin testing conducted through the PCCAS to
determine feasibility of using Dynamic Shear Rheometer (DSR) for testing AR binders
Very successful –results indicate DSR can be used for testing AR binders
Second round robin planned for early next year
AB 513 (FRAZIER) Establishes the rubberized asphalt concrete (RAC) market development act.
Requires CalRecycle to award grants to California Cities, Counties, and regional park districts.
Requires grants provide $2 for every 12 lbs. of crumb rubber used in a paving project.
Limited to road rehabilitation, not chip seal projects which use less crumb rubber.
Program sunsets on January 1, 2020 (5 year program)
AB 513 (FRAZIER) Background on why this bill is needed.CalRecycle collects $40 million annually for its tire fund from the fee on sale of new tires.
Of all the programs to divert tires from landfills, RAC grants have had the most success. Environmental groups support RAC because it is considered the highest and best use of tire recycling.
Most California Cities and Counties are strapped for money and even though life cycle costs for RAC are less than conventional asphalt, local governments look for up front savings.
AB 513 (FRAZIER) Conventional asphalt is cheaper up front. Unless they can get
grants, they usually repave with conventional asphalt)
The RAC grants are so popular in California that this past year $3 million was allocated for them but there were almost $10 million in qualified grant applications from cities and counties.
Governor Jerry Brown signed AB 513 on October 3, 2013.
Net result to industry is $7,000,000 +
How do you get your bang for your buck using Asphalt
Rubber design?
Reflection Crack Retardation Equivalencies (ft.)
HMA RHMA-GRHMA-G
Over SAMI-R
0.15 0.10 --
0.20 0.10 --
0.25 0.15 --
0.30 0.15 --
0.35 0.15 or 0.20a 0.10 or 0.15a
0.45 0.15/0.15 HMA 0.20
a. Depending on crack width and base conditions
3-Layer AR Cape Seal San Leandro
Original
AR Chip Seal
Microsurfacing as Leveling
Slurry/Micro Surfacing
Randolph AvenueCosta Mesa, CA
Costa Mesa 20 years old
37mm ARHM-GG
ARCS
25mm AC
Whittier 20 years old
37mm ARHM-GG
ARCS
25mm AC
Advantages of Asphalt Rubber Pavement Strategies
50% reduced thickness applicationInitial savingsIncreased fatigue resistanceReduced oxidation Reduced construction timeIncreased safetySavings in energy and natural resourcesLower maintenance cost
Thank You
Questions?