Asphalt Mix Performance Testing on Field Project on MTO Hwy 10 2 nd International Conference on Warm Mix Asphalt October 11 13, 2011, St. Louis, Missouri
Acknowledgements Presenter Paolo Visconti, Iterchimica Authors Coco Asphalt Engineering Selena Lavorato, Quality Systems Manager Steven Manolis, General Manager Coco Paving Inc. Andrew Pahalan, Quality Control Manager Ryon Reid, Product Development Specialist
Overview Introduction Job Scope HyperTherm Characteristics Mix Design and Binder Properties Performance Testing Rutting and Fatigue Resistance Moisture Sensitivity Dynamic Modulus Thermal Stress Restrained Specimen Test (TSRST) Low Temperature Flexural Creep Stiffness Field Performance Summary of Findings and Future Research Questions
Introduction Job Scope WMA paving project completed on Hwy 10 located in Toronto, Ontario, Canada Ministry of Transportation Ontario job 2010 2025. Work completed in month of September 2010. All mixes in project designed for Traffic Category D (10 to 30 million ESALs)
Sections of WMA and HMA on Hwy 10 Limits of contract extends from Highway 410 connection to Highway 10 northerly to Peel Road 9 (Kings Street)
Job Scope cont d Asphalt Cement utilized in job was PG 64 28 Polymer Modified for both sections. WMA was dosed with 0.2% HyperTherm warm mix additive. Both sections were SP 12.5mm FC2 (40mm in depth) over a SP 19mm HMA binder course (50mm in depth) PG64 28 PMA was utilized in binder course
HyperTherm Utilized in this field project Non aqueous chemical warm mix additive. Can be added at Terminal or at plant. No or minimal modifications needed to plant. Minimal effect on PGAC properties of binder. Known as QualiTherm in United States.
Mix Proportions Same proportions for both sections
Mix Properties Similar volumetrics obtained for both mixes
Production Site Coco Wolfedale Asphalt Plant HyperTherm dosed into AC at 0.2% at the Coco Millhaven Supply Terminal HMA ( o C) WMA ( o C) Plant Mixing Temperature 155 (311F) 130 (266F) Field Compaction Temperature 145 (293F) 110 (230F)
Binder Properties
Performance Testing Compared Performance Properties on plant produced field samples. Rut Resistance Asphalt Pavement Analyzer Fatigue Life 4 Point Bending Beam Flexural Fatigue Moisture Sensitivity Tensile Strength Ratio (TSR) Dynamic Mechanical Analysis Dynamic Modulus Low temperature cracking Thermal Stress Restrained Specimen Test (TSRST) Low Temperature Flexural Creep Stiffness
Rut Resistance Asphalt Pavement Analyzer (APA) AASHTO T340 Specimens compacted with gyratory compactor. Conditioned at 58C (136.4F) for a minimum of 6 hours prior to starting test. Wheel over pressurized hose and cycles back and forth for 8000 cycles. Rut Depth measured in mm.
Rut Resistance cont d Mix Rut Depth (mm) 12.5 mm FC2 WMA 5.25 12.5 mm FC2 HMA 4.57 WMA was more susceptible to rut however both mixes were within the limit of 8mm. Due to production temperatures, WMA was slightly more susceptible to rut since it was not as stiff.
Fatigue Life 4 Point Bending Beam Flexural Fatigue Test AASHTO T321 Material Testing System (MTS) test frame equipped with environmental chamber used to conduct test (20C (68F))
Fatigue Life Cont d Beams compacted using an Asphalt Vibratory Compactor (AVC) and then cut to size (62.5mm x 50mm x 375 mm). Cured for 5 days at 85C (185F) prior to testing. Samples are cycled through repeated sinusoidal loads with a 0.1 second load time and 0.4 second rest time. Fatigue life defined in terms of # of cycles required to reach 50% of initial beam stiffness.
Fatigue Life cont d Mix Initial Stiffness (MPa) Cycles to Failure (N f 50) 12.5 mm FC2 WMA 4,407 315,378 12.5 mm FC2 HMA 4,829 198,971 WMA shown an improvement of 58% in flexural fatigue. HMA more susceptible to fatigue, WMA was not as stiff. Due to production temperatures, WMA was more resistance to fatigue.
Moisture Sensitivity AASHTO T283 Tensile Strength Ratio (TSR) Minimum requirement in the province of Ontario = 80% HMA TSR = 92% WMA TSR = 82%
Dynamic Modulus AASHTO TP62 Dynamic Modulus (E*) is an indicator of stiffness of the mix. The absolute value of the peak to peak stress divided by peak to peak recoverable strain under sinusoidal loading. Phase angle (δ) describe the degree to which the mix is behaving as an elastic or viscous material. MTS test frame equipped with environmental chamber used to conduct testing over a range of temperatures and frequencies.
Dynamic Modulus Master Curve for 12.5mm FC2 for WMA and HMA
Thermal Stress Restrained Specimen Test (TSRST) AASHTO TP10 93 Samples conditioned over 5 days at 85C (185F). Initial tensile load applied and temperature is reduced at a rate of 10C (50F) per hour. (Samples conditioned at 5C (41F) for 6 hours prior to testing) Thermal contraction along vertical axis of beam is monitored. System incrementally re establishes the initial length of the beam by adjusting the end plants affixed to the sample. Process continues until internal stresses in samples increase to cause tensile fracture of specimen.
TSRST Cont d Average Fracture Temperature WMA = 21.6F ( 29.8C) HMA = 13.7F ( 25.4C) WMA Improved temperature cracking properties. Due to lower mixing temperatures during plant production.
Low Temperature Flexural Creep Stiffness Flexural creep stiffness at low temperature using the Bending Bend Rheometer (BBR). Asphalt mixture beams used. Cured for 5 day at 185F (85C) to simulate long term aging prior to testing. WMA lower Creep Stiffness values than HMA. Average Creep Stiffness @ 0.40F ( 18C) and 60s (MPa) HMA 12.5mm FC2 8,200 WMA12.5mm FC2 7,667
Field Performance WMA May 2011 HMA May 2011
Findings WMA and HMA both achieved acceptable APA rut testing results with HMA exhibiting nominally better rutting resistance than WMA. WMA exhibited significantly improved flexural fatigue properties than HMA in 4 Point Bending Beam Flexural Fatigue Test.
Findings con td WMA achieved 4.4 degrees C improvement over HMA in low temperature cracking performance with TSRST. WMA exhibited improved low flexural creep stiffness properties than HMA with thin beams of mix tested in BBR. Field Performance both mixes are performing well after 13 months including one winter in service.
Future Research Performance testing on different mixes. Evaluation of field performance of WMA versus HMA over time.
Thank you! Any Questions??