AC Binder Characterization Containing Crumb Tire Rubber

AC Binder Characterization Containing Crumb Tire Rubber Gaylon L. Baumgardner Paragon Technical Services, Inc. LOUSIANA TRANSPORTATION RESEARCH CENTER SUSTAINABLE MATERIALS FOR PAVEMENT INFRASTRUCTURE: USE OF WASTE TIRES IN ASPHALT MIXTURES 5 SEPTEMBER 2012

INTRODUCTION

RUBBER MODIFIED ASPHALT Ground Tire Rubber (GTR) is a post consumer polymer fractionally beneficial in modification of asphalt binders. Benefits of modification of asphalt with GTR are similar to those achieved with virgin synthetic polymers with the exception GTR loadings are typically higher. Knowledge and technology for processing GTR modified binders are just as critical as with synthetic polymer modified binders e.g. SBS In the US, Asphalt Rubber or rubber modified bitumen/asphalt is the largest single market for recycled tires and consumes an estimated 12 million tires annually.

RUBBER MODIFIED ASPHALT Ground Tire Rubber (GTR) is separated into two particle sizes by class ground (2000μm and less) and coarse (greater that 2000μm) Rubber produced from ground whole tires contains ~ 30% reactive material for asphalt modification. Functional yield is dependent of tire composition and asphalt and is directly proportional to rubber source, rubber particle size and asphalt source. Terminal blending can be an operations challenge without adequate knowledge of asphalt chemistry, GTR source and processing.

TIRE COMPONENTS AND COMPOSITION

TYPICAL TIRE CONSTRUCTION

TYPICAL TYPES OF MATERIALS USED TO MANUFACTURE TIRES Synthetic Rubber Styrene-Butadiene Rubber Isoprene Butadiene Butyl Rubber Halogenated Butyl Rubber Ethylene Propylene Diene Monomer Natural Rubber Sulphur and sulphur compounds Silica Phenolic resin Oil: aromatic, naphthenic, paraffinic Fabric: Polyester, Nylon, Etc. Petroleum waxes Pigments: zinc oxide, titanium dioxide, etc. Carbon black Fatty acids Inert materials Steel Wire

TYPICAL TIRE COMPOSITIONS BY WEIGHT Passenger Tire Natural rubber 14 % Synthetic rubber 27% Carbon black 28% Steel 14-15% Fabric, fillers, accelerators, antiozonants, etc. 16-17% Average weight: New 25 lbs, Scrap 20 lbs. Truck Tire Natural rubber 27 % Synthetic rubber 14% Carbon black 28% Steel 14-15% Fabric, fillers, accelerators, antiozonants, etc. 16-17% Average weight: New 120 lbs., Scrap 100 lbs.

RUBBER PERCENT BY WEIGHT IN A NEW RADIAL PASSENGER TIRE TREAD 32.6% BASE 1.7% SIDEWALL 21.9% BEAD APEX 5.0% BEAD INSULATION 1.2% FABRIC INSULATION 11.8% INSULATION OF STEEL CORD 9.5% INNERLINER 12.4% UNDERCUSHION 3.9% 100.0%

MODIFIED ASPHALT BINDERS

ASPHALT MODIFICATION Samuel Whiting 1873 patent 1% natural rubber (Balata) France 1902 Rubberized asphalt Paving technologist improving asphalt pavements since. Use of synthetic polymers limited Styrene-Butadiene Polymers most common Rubber is a polymer of primarily the Styrene- Butadiene type

UTI SUPERPAVE MADE SIMPLE

SUPERPAVE UTI

CONTINUOUS PHASE 20 Parts Natural Rubber + 80 Parts Cement Water Xylenes

CR ASPHALT MODIFICATION METHODS CR in asphalt is not a new idea. Three common methods of modification: Wet Process Rubber blended with asphalt at the asphalt mix facility CR content ~ 18 20% Dry Process Rubber added to mixture either fine or coarse CR content ~ 5 25% Terminal Blend Rubber blended with asphalt and stored as liquid CR content ~ 5 15%

CRITICAL PARAMETERS Asphalt Source Asphalt Grade Rubber Composition Natural/Synthetic Rubber Particle Size < 30 mesh Rubber Grinding Method Ambient/Cryogenic Blending Temperature > 180 C Blending Time > 45 min.

SPECIFICATIONS

Historically testing has been done with pen and vis. Viscosity was mostly rotational or vane shear. CRM

NEW CRM SPEC TO MATCH MSCR BINDER SPEC Original DSR G*/sinδ Min 1.0 64 64 Standard MSCR3.2 <4.0 64 Heavy MSCR 3.2<2.0 64 Very heavy MSCR3.2 <1.0 [(MSCR3.2 MSCR 0.1)/ MSCR 0.1] <.75 RTFOT PAV 64 64 64 S grade DSR G*sinδ Max 5000 H & V grade DSR G*sinδ Max 6000 28 25 22 19 16 28 25 22 19 16 Low temp BBR and DTT remain unchanged

CRM SIZES Rubber is delivered in different systems with supper sacks very prevalent. CRM comes in different sizes.

COMPARISON OF MEASUREMENTS AT 1 AND 2 MM GAPS 2.00 1.80 76 C G*/sinδ, 1 mm Gap (kpa) 1.60 1.40 1.20 1.00 0.80 Linear (Line of Equality) 0.60 0.40 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 G*/sinδ, 2 mm Gap (kpa)

HOW TO HANDLE LARGER CRM 60 mesh material is easily handled in 1 mm gap. 30 mesh material may be tested at 2 mm 20 mesh material may require larger gaps. What is the limit of gap size? Are other geometries available to test larger particles?

4 MM GAP

Malvern Instruments Kinexus Pro Rheometer Active Heated Chamber Used with 25mm parallel plates Peltier Cylinder Cartridge Used with Cup & Bob and Cup & Vane

PARALLEL PLATE

CUP & BOB Top View

COMPARISON OF GEOMETRIES DSR 64-22 NEAT 70-22 (64-22+PPA) 74 72 PP1, 72.2 PP2, 72.4 CB, 72.6 Continuous grade temp 70 68 66 PP1, 65.8 PP2, 65.7 CB, 65.9 64 62 PG 64 22 PG 70 22

COMPARISON OF GEOMETRIES DSR 64-22 NEAT 70-22 (64-22+PPA) For Neat binder and or non particulate modifier the three geometries provide equivalent results using current G*/sin criteria.

CONTINUOUS GRADE FOR SPECIFIC BINDERS WITH DIFFERENT GEOMETRIES 80 60 65.8 65.7 65.9 73.6 73.6 72.1 40 20 24.6 20.4 0 20 40 22.00 1 25.46 64 22 PP1 64 22 PP2 64 22 CB 64 22 PAV 64 22 BBR 10% 60M PP1 10% 60M PP2 10% 60M CB 10% 60M PAV 10% 60M BBR

PG CONTINUOUS GRADING FOR BLENDS USING DIFFERENT GEOMETRIES 70 64 22 Continuous grade 50 30 10 BBR 70 22 76 22 10% 60M 15% 60m 10% 30M 10 PP1 PP2 C&B PAV DSR 15% 30M 30

EFFECT OF CRM ON LOW TEMPERATURE GRADE Low Temp Continuous Grade All m controlled Difference between S and M grade temp All m controlled 0.00 64 22 70 22 76 22 10% 60M 15% 60m 10% 30M 15% 30M 8.00 7.00 5.00 Transportation 6.00 10.00 5.00 15.00 20.00 25.00 30.00 22.00 22.67 23.13 25.46 27.61 25.09 27.63 4.00 3.00 2.00 1.00 0.00 Low Temp Grade 64 22 70 22 76 22 10% 60M 15% 60m 10% 30M 15% 30M

MSCR JNR 0.1KPA DATA FOR VARIOUS BLENDS 3.5 3 Jnr 0.1 kpa 1 2.5 2 1.5 1 0.5 PP1 PP2 CB 0 64 22 70 22 76 22 10% 60M 15% 60m 10% 30M 15% 30M binder blend

MSCR JNR 3.2KPA DATA FOR VARIOUS BLENDS 4 3.5 3 Jnr 3.2 kpa 1 2.5 2 1.5 1 0.5 PP1 PP2 CB 0 64 22 70 22 76 22 10% 60M 15% 60m 10% 30M 15% 30M Binder blend

OTHER ISSUES Solubility What values should be considered? 99% 93% No solubility MSCR % Recovery Rubber and polymers are not the same. Do we have a separate spec?

NEW CRM SPEC TO MATCH MSCR BINDER SPEC Original DSR G*/sinδ Min 1.0 64 64 Standard MSCR3.2 <4.0 64 Heavy MSCR 3.2<2.0 64 Very heavy MSCR3.2 <1.0 [(MSCR3.2 MSCR 0.1)/ MSCR 0.1] <.75 RTFOT PAV 64 64 64 S grade DSR G*sinδ Max 5000 H & V grade DSR G*sinδ Max 6000 28 25 22 19 16 28 25 22 19 16 Low temp BBR and DTT remain unchanged

SUMMARY

SUMMARY CRM binder is sensitive to crude source. Rubber size will effect test results. Particles should be ¼ gap size or less. Careful formulation is needed to meet all Jnr specs, but it can be done successfully. CRM Binders can be produced to meet PMA specs. Large CRM particle sizes can be tested in DSR

SUMMARY There may be some differences for CRM binder spec and PMA Spec Solubility for CRM binder may be different. Stress sensitivity may be different. Most other properties will be the same. Addition of ground tire rubber (GTR) to asphalt is an accepted practice in HMA production Modification of liquid asphalt binders with GTR is well established and can provide high performance pavements which aid in reduction of the number of waste tires deposed of in landfills and elsewhere

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