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?