Asphalt Rubber: The Arizona Experience. Julie Kliewer, Ph.D., PE Arizona Department of Transportation

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1 Asphalt Rubber: The Arizona Experience Julie Kliewer, Ph.D., PE Arizona Department of Transportation

2 What is Asphalt Rubber? A mixture of Aggregate Asphalt Rubber Binder (crumb rubber + asphalt cement)

3 Ground Tire Rubber

4 ADOT Rubber Mixes AR-ACFC Final wearing surface (friction course) ARAC Structural Lift

5 History: I-19 Project (1988) 10.0 % asphalt rubber by weight of mix Placed on plain jointed concrete pavement First reflection cracks noted in 1996 Sections no longer in service because of I-10/I-19 interchange project not because of poor performance Experimented with recycling in this section

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7 History: ARAC 1990 placed on I-40 near Flagstaff 2 thick Structural Overlay Gap graded mix Placed on severely cracked and failed concrete pavement Least reflection cracking of any application

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9 Usage Tons Mix Thousands ARAC AR-ACFC

10 ADOT ARAC and AR-ACFC Usage Year Tons of mix Est. Tires Recycled ,155 2,512, ,260 1,921, ,570 1,802, ,790 1,803, ,566 1,926, ,914 2,100,000

11 About 1000 Tires Per Lane Mile

12 What does Asphalt Rubber do for us? Nature of asphalt rubber binder allows the use of approximately 2% more binder than with asphalt cement Elastic properties slow reflective cracking Asphalt rubber binder does not seem to age as rapidly as asphalt cement It lasts! Reduces noise It is not without its cost$$

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14 Asphalt Cements in CRA Type 1 Hot Climate PG (Phoenix) Type 2 Moderate Climate PG (Prescott, Flagstaff) Type 3 Cold Climate PG (Alpine, highest elevations)

15 CRA Properties Influenced by Asphalt Cement Amount of crumb rubber Crumb rubber gradation Reaction temperature and time

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17 Viscosity Monitors fluid consistency of binder to: Ensure pumpability Identify binder changes which might affect mix placement and compaction Can be done in field

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21 Resilience Appears to be a reliable measure of the elastic properties of the asphalt rubber binder. Expressed as a percentage of rebound for the binder. Resilience is one of the most important properties of AR binders and is considered a primary indicator of performance.

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25 Design of Asphalt Rubber Mixtures AR-ACFC ARAC

26 AR-ACFC A: Asphalt R: Rubber - A: Asphaltic C: Concrete F: Friction C: Course

27 AR-ACFC Open graded (not free draining) Typically around 9.5% asphalt rubber (by wt of total mix) (range 8.9% to 10.0%) Used as final wearing surface, not structural On asphalt pavements, typically ½ inch thick On concrete pavements, typically 1 inch thick

28 AR-ACFC Mix Design Aggregate basically 95% 3/8 chips and 5% fines Get as much asphalt rubber binder in the mix as possible without draindown

29 AR-ACFC Mix Design: Determining Binder Content Starting binder content estimated by equation Starting point may be adjusted based on history Check draindown Adjust binder content as needed

30 AR-ACFC: Design 1. Place Mix in a beaker 3. Empty beaker 2. Place beaker in oven for 1 hour 4. Determine % mass loss

31 How much rubber in AR-ACFC 20% rubber by weight of asphalt cement Approximately 9.5% asphalt rubber binder in mix Works out to about 1.75% rubber in the mix

32 ARAC A: Asphalt R: Rubber A: Asphaltic C: Concrete

33 ARAC Gap graded (to allow space for rubber particles) Typical binder contents 6.5% to 8.0%

34 ARAC Design Design for 4.5 to 6.5% air voids Minimum VMA specified Have to watch for building of VMA by binder

35 Costs (a little outdated) ACFC $1.60/sy AR-ACFC $2.20/sy AC(3/4) $2.25/sy/in ARAC $3.25/sy/in Asphalt Rubber $300/ton Asphalt Cement $200/ton

36 Asphalt Rubber How is it made?

37 Asphalt Rubber Binder Minimum 20% crumb rubber by weight of asphalt cement Crumb rubber added to F asphalt cement Crumb rubber and asphalt cement mixed Asphalt rubber reacted for at least one hour at with agitation

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39 An aerial view of a portable Asphalt-Rubber Plant setup at a Hotplant. RUBBER STAGING AREA BLENDER VIRGIN AC TANK AR BLEND TANK Hotplant

40 High Shear Mixer

41 Mix Placement

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51 Quiet Pavments Program

52 Quiet Pavement Pilot Program Arizona QPPP consists of Initial research to demonstrate performance of existing and proposed pavement Overlaying new and existing PCC with ARFC 4 db credit for lower tire/pavement noise On-going testing to track pavement performance

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54 Noise Levels By Surface Type (CPX) 105 Random Transverse (Wisconsin) 102 Uniform Transverse (ADOT-3/4 ) 99 Longitudinal (ADOT-3/4 ) 99 Whisper Grind 94 ARFC

55 Asphalt Rubber Performance

56 Smoothness Ride (In./Mile) PCCP PCCP_ARFC Age (YR)

57 Friction Levels Mu PCCP PCCP_ARFC Desired Level Age

58 Rutting Rut Depth vs. Age 0.3 Rut Depth, inches Overlays / Inlays AR-ACFC Year

59 Maintenance Costs Maintenance Cost $/lane -Mile 1600 Overlays / Inlays Neat asphalt only Asphalt Rubber projects Maint. Cost Year

60 Cracking Percent Cracking vs Age % Cracking Years Overlays / Inlays Neat asphalt only Asphalt Rubber projects

61 Smoothness (AR-ACFC v. ACFC) Smoothness vs Age for AC pavements Inch. / Mile Year ACFC AR- ACFC

62 Friction Levels AR-ACFC v. ACFC Friction Vs. Age Mu Meter number ACFC AR-ACFC Year

63 I-17 SB ARFC placed in 1994, elev. 6800

64 I-17 SB MP I-17 SB MP Cracking (%) Roughness (in/mi) Year Roughness Cracking

65 I-19 AR-ACFC placed in 1989, elev. 2700

66 I-19 Project built in 1989 I-19, MP 59, Roughness/Cracking vs Age Crack (%) Roughness (in/mi) Year 2001 Cracking Series1 Roughness Series2

67 AR-ACFC Recycling Research Hot-in-place proof of concept I-19 Project Hot-in-place Hot plant (20% and 30% RAP) using terminal blend Constructed in 2006, performing well

68 Its Perfect, isn t it? When things go wrong.

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72 I-17 Problem 1

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75 I-17 The new Problem

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83 Jack Rabbit

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88 SR 260 The Summer Problem

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