NCHRP Project 9-61 Short- and Long-Term Binder Aging Methods to Accurately Reflect Aging in Asphalt Mixtures Ramon Bonaquist, P.E.
Research Team Ramon Bonaquist - PI Western Research Insititute Jeramie Adams - Co-PI Consultants Dave Anderson Gayle King Jim Rosenberger Erick Sharp
Outline Objectives Project Tasks Work Completed What s Next
Objectives Evaluate AASHTO 240, AASHTO R 28 and alternatives Recommend improvements New procedure Modifications to existing procedures Calibrate the improved procedures to accurately simulate aging Mixture production, transport, and placement Service life of the pavement
NCHRP 9-61 Is Not! A study of binder rheology A study of binder chemistry A study to relate chemical and rheological properties of binders A study to recommend improved specification criteria
Approach Task 1. Evaluate and Select Methods Task 2. Prepare Experimental Plans Task 3. Prepare Interim Report Task 4. Conduct and Analyze Experiments Task 5. Perform Industry Impact Assessment Task 6. Prepare Methods in AASHTO Format Task 7. Prepare Final Report
How Much Binder? Only a few grams if you use 4 mm DSR Probably not realistic at this time M 320 or M 332 without direct tension 35 g for verification 65 g for grading M 320 or M 332 with Modified DENT? (per 9-59) 75 g for verification 105 g for grading M 320 or M 332 with LAS? (per 9-59) 40 g for verification 70 g for grading
What is Target Age for Long-Term? Consensus that R 28 (20 hour PAV) is not severe enough Research now using 40 hour PAV Limited field data equating either 20 or 40 hour PAV to field properties SHRP A 369: 20 hr PAV ~ 4 to 8 years Erskine, et al. 2012: 40 hr PAV ~ 8 years AAPTP Project 06-01: No change to R 28 WRI Fundamental Properties of Asphalts and Modified Asphalts III : ALF, and AZ Braden Smith
Analysis of LTPP SPS 8 Sites New pavements on roads with limited truck traffic Two sections 4 in AC on 8 in of aggregate base 7 in AC on 12 in of aggregate base 15 sites constructed Distresses monitored every 1 to 2 years
Transverse Cracking in SPS 8 Sections 45 40 Length of Transverse Cracks, m 35 30 25 20 15 10 5 AR CA MS NM NC MO NY OH WI 0 0 2 4 6 8 10 12 14 16 18 20 Pavement Age, yrs
Practice Related T 240 Conditioning Issues Uniformity of the film and how well it is renewed is viscosity dependent Some modified binders tend to crawl out of the bottle Shape of the bottle makes recovery of the binder and cleaning difficult Procedure does not address WMA
Short-Term Alternates Modified German Rotating Flask Stirred Air Flow Test Universal Simple Aging Test Rotating Cylinder Ageing Test Ageing Profile Test
Short-Term Considerations Quantity of binder Number of binders per run Conditioning time Improves film uniformity Eliminates crawling from container Suitable for crumb rubber binders Simulate HMA and WMA temperatures Improves binder recovery Standard available Equipment availability Equipment cost Training cost
Short-Term Selections Modifications to t 240 made in the U.K. Ageing Profile Test Thicker Film USAT Around 0.8 mm rather than 0.3 mm to increase yield
AAC-1 @ 163 C for 85 min 3.50 AAC-1 Pan Aged RTFOT Original G*/sinδ at 58 C, kpa 3.00 2.50 2.00 1.50 1.00 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 Thickness, mm
AAF-1 @ 163 C for 85 min 3.50 AAF-1 Pan Aged RTFOT Original G*/sinδ at 64 C, kpa 3.00 2.50 2.00 1.50 1.00 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 Thickness, mm
Practice Related R 28 Conditioning Issues Conditioning is not severe enough Service life that is simulated is not well defined
Long-Term Alternates Rotating Cylinder Ageing Test Ageing Profile Test Universal Simple Aging Test Extended Time PAV Thinner Film PAV Increased Temperature PAV Mixing in PAV Ultrasonic Resonant Acoustic
Long-Term Considerations Quantity of binder Number of binders per run Conditioning time Conditioning temperature Atmosphere (air vs oxygen) Pressure Correlated to field aging Standard available Equipment availability Equipment cost Training cost
Long-Term Selection Thinner Film PAV Film Thickness, mm Surface Area Required, cm 2 Verification (75 g assumed) Grading (105 g assumed) 3.18 233 330 1.59 465 660 0.8 925 1313 0.3 2467 3500
AAF-1 Master Curve Parameters 3.00 AAF-1, 20 hrs AAF-1, 40 hrs 2.80 Rheological Index 2.60 2.40 2.20 2.00 0.80 mm 1.08 mm 1.59 mm 0.80 mm 1.08 mm 3.18 mm 1.59 mm 3.18 mm 1.80 1.60 0.01 0.10 1.00 10.00 100.00 ωc, Rad/sec
AAF-1 Master Curves 1.0E+09 1.0E+08 1.0E+07 1.0E+06 G*, Pa 1.0E+05 1.0E+04 1.0E+03 1.0E+02 1.0E+01 40 hr 0.8 mm 40 hr 3.18 mm 20 hr 1.08 mm 20 hr 3.18 mm 1.0E+00 Reduced Frequency, rad/sec
ATS 167 Dimensions in mm 203 140 Original Prentex 203 167 420 140 305 225 197
Example PAV Pan for 0.8 mm Film 117.0 mm 167.0 mm 3.18 mm 3.18 mm
Proposed Phase 2 Experiments Short-Term Final Selection Short-Term Calibration PAV Thickness, Time, Temperature Long-Term Calibration Sensitivity Study
Short-Term Selection Make final selection of short-term procedure Thin film aging (0.8 mm) UK mixing screw NCHRP 9-61 improved mixing screw Compare binder conditioning procedures to binder recovered from short-term oven aged mixtures NCHRP 9-52 recommendations HMA 2 hours at 135 C WMA 2 hours at 116 C
Short-Term Selection Aging Methods Neat PG 52-34 Polymer (Terpolymer) PG 64-34 Neat PG 64-22 Polymer (SBS) PG 76-22 GTR ASTM D 6114 WMA HMA WMA HMA WMA HMA WMA HMA HMA AASHTO T 240 X X X X X X X X X UK Mixing Screw X X X X X X X X X NCHRP 9-61 Mixing Screw X X X X X X X X X Static Thin Film (0.8 mm) X X X X X X X X X Recovered, NCHRP 9-52 Oven Aging X X X X X X X X X Response variables: High temperature continuous grade Master curves CS+SO GPC for modified binders
Short-Term Calibration Calibrate the selected procedure (varying conditioning time) to reproduce properties of binder recovered from short-term conditioned loose mix NCHRP 9-52 recommendations HMA 2 hours at 135 C WMA 2 hours at 116 C High Temperature Continuous Grade
Short-Term Calibration Mix Temp WMA HMA Binder Properties Mix Properties Low 19 mm 9.5 mm SMA Binder Aging Temp Diabase with Type Index Sandstone Limestone Grade Limestone Filler Neat -34 or -28 Low X X X High X X X -22 or -16 Low X X X High X X X Modified -34 or -28 Low X X X High X X X -22 or -16 Low X X X High X X X Neat -34 or -28 Low X X X High X X X -22 or -16 Low X X X High X X X Modified -34 or -28 Low X X X High X X X -22 or -16 Low X X X High X X X
PAV Thickness, Time, Temperature Investigate how to reasonably simulate more aging using the PAV Vary thickness, time, temperature Compare rheological and chemical properties to recovered binders from ARC Arizona (hot,16 yrs) and Minnesota (cold, 11yrs) sections Binder master curves, carbonyl + sulfoxide
ALF Field Aging 4.0 Lab Aged 96 Month Ambient 96 Month Ambient + 8 Month Acclerated 3.5 Rheological Index 3.0 2.5 2.0 1.5 6.5 mm 6.5 mm 19 mm 48.5 mm PAV 61.5 mm RTFOT Original 1.0 0.0001 0.001 0.01 0.1 1 10 100 1000 10000 Crossover Frequency, rad/sec
ALF Master Curves 1.0E+09 1.0E+08 1.0E+07 1.0E+06 G*, Pa 1.0E+05 1.0E+04 1.0E+03 1.0E+02 1.0E+01 1.0E+00 6.5 mm 96 Month + 8 Month Accelerated 6.5 mm 96 month 19 mm 96 month 48.5 mm 96 month 61.5 mm 96 month Reduced Frequency, rad/sec
ARC AZ and MN Binders Site Grade Source Modification Arizona US PG 76-16 WTI/WTS blend Airblown 93 PG 76-16 Venezuelan N/A PG 76-16 Rocky Mountain N/A Blend PG 76-16 Canadian Blend N/a Rochester, PG 58-34 Canadian Blend Terpolymer MN PG 58-28 Canadian Blend N/A PG 58-28 Middle East Blend N/A PG 58-28 Venezuelan Blend N/A
Partial Factorial Temp, C 90 100 110 Thickness, Time, hrs mm 20 30 40 3.18 X 1.59 X X 0.80 X 3.18 X X 1.59 X 0.80 X X 3.18 X 1.59 X X 0.80 X Response surface experiment Process improvement experiments
Output of Thickness, Time, Temperature Experiment Film thickness Conditioning time Range of useable temperatures
Long-Term Calibration Using thickness and time from the previous experiment, vary the conditioning temperature to determine conditioning temperature that reproduces the properties of binder recovered from field cores Binder master curves, carbonyl + sulfoxide
Example 0 Change in log ωc -1-2 -3-4 -5-6 75 mm 6 mm 80 85 90 95 100 105 110 115 120 Conditioning Temperature, C
Available Original Binders and Cores From LTPP
Age Age, Years 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 Section Number
Degree Days 7000 6000 5000 Degree Days 4000 3000 2000 1000 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 Section Number
Regression Analysis of Conditioning Temperatures Factors Climate Age Depth in pavement Air voids Binder volume Use regression model to recommend final lab conditioning temperatures
Sensitivity Study M 320 and M 332 Grade several binders Current T 240 and R 28 Improved procedures developed in NCHRP 9-61 Materials with proven performance Newer materials 8 to 10 binders Information for the Industry Assessment