Innovative Research in Asphalt Pavements University of Massachusetts Dartmouth Highway Sustainability Research Center Field and Laboratory Evaluation of Plant Produced Highly Modified Thin Lift Overlay Mixtures Incorporating RAP Thursday 9:00 AM By: Professor Walaa S. Mogawer, P.E., F.ASCE Professor of Civil & Environmental Engineering Director - Highway Sustainability Research Center University of Massachusetts Dartmouth
Definitions High Performance Overlays (HiPO) - Pavement preservation strategy - Thickness equal to 1 inch or less - Used in applications requiring higher levels of rutting and fatigue resistance
Definitions Highly Modified Asphalt (HiMA) - A new SBS polymer technology developed by Kraton Polymers - The SBS polymer loading is more than twice that of ordinary modified asphalt, yet mixes are readily workable and easy to lay in the field.
Pilot Specifications - A pilot regional specification for HiPO mixtures entitled Superpave 9.5 mm Highly Polymer-Modified Thin Overlay Specifications was developed based on input and recommendations from members of state transportation agencies of various regional pavement preservation partnerships, industry, and academia. Pilot specification on AASHTO TSP2 web site: http://www.tsp2.org/pavement/other-information/research-pavement/
Pilot Specifications The goal of the specification was to provide a guide that could be utilized to develop better performing preservation/ rehabilitation overlay mixtures that addresses reflective cracking, low temperature cracking, fatigue cracking, and rutting.
Project Scope 9.5mm HiPO Reclaimed Asphalt Pavement Highly Modified Asphalt (HiMA) Aggregates
2011 Field Trials - Minnesota Department of Transportation (MnDOT) had 1370 tons of HiPO incorporating 25% RAP placed on a 1-3/4 mile northbound section of Trunk Highway (TH) 100 west of Minneapolis (AADT = 64,000) - New Hampshire Department of Transportation (NHDOT) had 1,500 tons of the HiPO incorporating 25% RAP on Route 202 in Rochester, NH (AADT = 4,600) - The Vermont Agency of Transportation (VTrans) placed one mile of HiPO mixtures without RAP and one mile of HiPO incorporating 25% RAP on US Route 7 in Danby, VT.
2012 Field Trials - Field trial conducted in Oregon in June 2012. - Other trials planned during 2012 construction season.
2011 Field Trials Existing Condition - MN: Pavement exhibited bad transverse cracks and potholes were developing. Milling to a depth of 1.5 inch or 2 inch was completed prior to placement of the mixture. - NH: pavement was in poor condition and no milling was done prior to the placement of the mixture. - VT: Pavement in its 14 th year of service and in fair to good condition. Isolated areas of permanent deformation and some transverse cracking.
Project Objective! Using plant produced mixture, evaluate the effect of HiMA on mixture performance in terms of: Reflective cracking using the Texas Overlay Tester (OT) Fatigue cracking using the Flexural Beam Fatigue Thermal cracking using the Thermal Stress Restrained Test Specimens (TSRST) Rutting using the Asphalt Pavement Analyzer (APA) and Hamburg Wheel Tracking Device (HWTD)
Experimental Plan HiMa Binders 1. 52-34 + 7.5% Polymer 2. 200PEN + 7.5% Polymer Binder Testing Rheological Properties R = Rheological Index ω rm = Cross Over Frequency (rad/sec) T d = Defining Temperature (ºC) Superpave HiPO 9.5 mm Mixture Field Trials 1. Minnesota (MN) 2. New Hampshire (NH) 3. Vermont (VT) Plant Produced Mixtures Mix Design Verification Performance Testing Reclaimed Asphalt Pavement (RAP) Virgin Aggregates Cracking 1. Overlay Tester 2. Flexural Beam Fatigue 3. Thermal Stress Restrained Specimen Test (TSRST) Rutting 1. Asphalt Pavement Analyzer (APA) 2. Hamburg Wheel Tracking Device
Sieve Size MN* Mixture Information NH VT No RAP VT With RAP Pilot Spec. Pilot Spec. Production Tolerance 25.0 mm 100 - - - - - 19.0 mm 95.0 - - - - - 12.5 mm 83.0 100 100 100 100 ± 6 9.5 mm 62.0 98.8 99.0 98.0 90-100 ± 6 4.75 mm 50.0 68.4 83.0 81.0 90 ± 6 2.36 mm 35.0 49.9 55.0 55.0 32-67 ± 4 1.18 mm 24.0 36.8 34.0 35.0 - - 0.600 mm 13.0 26.2 21.0 21.0 - - 0.300 mm 6.0 15.2 11.0 11.0 - - 0.150 mm 3.3 8.0 6.0 6.0 - - 0.075 mm 4.0 4.8 3.7 3.7 2-10 ± 1 RAP % 25% 25% 0% 24% 25% max. - * Same gradation for MN control and HiPO mixtures.
Sieve Size MN* Mixture Information NH VT No RAP VT With RAP RAP % 25% 25% 0% 24% Total Binder Content, % Virgin Binder Content, % Expected Binder Contribution from RAP, % 5.3% 6.3% 6.8% 6.5% Pilot Spec. 25% max. 6.5% min. Pilot Spec. Production Tolerance 4.9% 5.3% 6.8% 5.5% - - 0.4% 1.0% n/a 1.0% - - - ± 0.3
Binder Information Base Binder PG Grade Target HiPO Binder Grade Mixing Temperature Compaction Temperature Superpave Design Gyrations MN* Control PG64-28 HiPO PG52-34 NH VT No RAP VT With RAP Pilot Spec. 200PEN 200PEN 200PEN - PG76-34 PG76-34 PG76-34 PG76-34 321-307ºF (161-153ºC) 272-265ºF (133-129ºC) 340ºF (171ºC) 300ºF (149ºC) 351-311ºF (177-155ºC) 310-291ºF (154-144ºC) 351-311ºF (177-155ºC) 310-291ºF (154-144ºC) PG76-34 or PG82-28 90 75 65 65 - - * Same temperatures for MN control and HiPO mixtures.
Mixture Design Verification of Volumetric Properties MN Control MN HiPO NH VT No RAP VT With RAP Pilot Specification (Refer to AASHTO M323 Table 6) Air Voids,% 4.9 3.8 2.0 3.2 2.7 4.0% VMA, % 16.5 15.4 16.3 n/a n/a 15.0% min. VFA, % 70.5 75.4 87.9 n/a n/a 65-75
Mixture Design & Volumetric Properties! MN gradation did not meet pilot specification (9.5mm). MN followed 12.5mm specification.! NH and VT mixtures did not meet all volumetric targets.
Reflective Cracking - Overlay Tester - Test Temperature = 15ºC (59ºF) - Test Termination at 2,000 cycles or 93% Load reduction - Testing in accordance with Tex-248-F Diagram from: Zhou et al. Overlay Tester: Simple Performance Test for Fatigue Cracking Transportation Research Record: Journal of the Transportation Research Board, No. 2001, Transportation Research Board of the National Academies, Washington, D.C., 2007, pp. 1 8.
Mixture Overlay Tester Results Average Overlay Test (OT) Cycles to Failure Pilot Spec. 2 MN Control 133 300 MN HiPO 434 300 NH 2,000* 300 VT No RAP 2,000* 300 VT With RAP 1,144 300 * Mixture did not meet test failure criteria at the conclusion of 2,000 cycles in OT. 2 Mixtures containing RAP shall exhibit average overlay test cycles to failure (93% load reduction) within ± 10 percent of the overlay test cycles to failure of control specimens without RAP.
Overlay Tester - Conclusions! MN mixtures exhibited low cycles to failure. May be a result of mixture designed utilized (12.5mm) which had a lower asphalt content than the specification recommended.! The NH and VT No RAP mixture performed well as they did not meet the failure criteria after 2,000 cycles.! The VT RAP mixture results indicated that the addition of RAP reduced the number of cycles to failure in the OT.
Fatigue Cracking 4pt Flexural Beam Fatigue - Testing and Analysis in accordance with AASHTO T321 - Test Temperature = 15ºC (59ºF) - Pilot specification states that strain level should be equal to the strain in the existing HMA layer. - If existing strain unknown, use: 750 micro strain for PG76-34 500 micro strain for PG82-28
Mixture Fatigue Cracking Results Strain Level Average N f * Pilot Spec. MN Control 750µε 27,349 >100,000 MN HiPO 750µε 329,096 >100,000 NH 750µε 312,068 >100,000 VT No RAP 750µε 1,081,030 >100,000 VT With RAP 750µε 420,656 >100,000 * N f = Number of cycles to 50% reduction in initial stiffness using method outlined in AASHTO T321.
Fatigue Cracking - Conclusions! All mixtures incorporating the HiMA binder met the generic criteria of 100,000 cycles to failure.! Field strain levels needed to confirm that 750µε level correctly represents field condition.! MNDOT Control mixture fabricated with PG64-28 binder showed lower fatigue life as compared to the mixtures with the HiMA binder.
Mixture Low Temperature Cracking - TSRST - Cooling Rate of -10ºC/hour - Testing in accordance with AASHTO TP10-93
TSRST Mixture Low Temperature Cracking Results Mixture MN Control MN HiPO NH VT No RAP VT With RAP Average Low Cracking Temp. -32.2ºC -31.8ºC -33.1ºC -30.1ºC -27.8ºC Pilot Spec. ± One PG Grade From Low Temperature PG of Binder ± One PG Grade From Low Temperature PG of Binder ± One PG Grade From Low Temperature PG of Binder ± One PG Grade From Low Temperature PG of Binder ± One PG Grade From Low Temperature PG of Binder
TSRST - Conclusions! All mixtures cracked at a warmer temperature than the required low temperature grade of the binder (-34ºC), but normally within -3ºC.! The VT mixture with RAP showed the lowest average low cracking temperature (-27.8ºC).! No trend regarding the impact of the inclusion of RAP on the low temperature cracking of the mixtures was noted.
Rutting Asphalt Pavement Analyzer - Test Temperature of 60ºC (140ºF) - Testing in accordance with AASHTO T340 - Test Length of 8,000 cycles
Rutting - Hamburg Wheel Tracking Device (HWTD) - HWTD testing conducted in accordance with AASHTO T324 - Water temperature of 50ºC (122ºF) - Test duration of 20,000 cycles
APA and HWTD Rutting Results Mixture APA Average Rut Depth 4mm at 8,000 Cycles HWTD Average Rut Depth at 10,000 Cycles (mm) HWTD Average Rut Depth at 20,000 Cycles (mm) MN Control 6.20 mm 2.11 mm 10.53 mm MN HiPO 5.92 mm 1.60 mm 20 mm NH 5.16 mm 4.20 mm 20 mm VT No RAP 2.03 mm 2.55 mm 8.98 mm VT With RAP 2.87 mm 1.26 mm 2.70 mm
Rutting Conclusions! The MN and NH mixtures exhibited average rut depths outside of the pilot specification range of less than 4mm.! The HWTD rut data showed similar rutting trends at 20,000 cycles.
Summary! Reflective cracking data laboratory indicated that the HiPO mixtures are resistant to reflective cracking, but this resistance could be decreased when RAP is incorporated into the mixture.! Low temperature cracking laboratory data and field observations suggested the HiPO mixture has a high resistance to low temperature cracking.
Summary Beam fatigue laboratory data suggested the HiPO mixture has a high resistance to fatigue cracking, even with the incorporation of up to 25% RAP. APA and HWTD rut testing indicated similar rankings of rut resistance of the HiPO mixtures.
Summary Overall, realizing that the performance period of one year is short, the projects will be monitored continuously for the next three years to confirm the validity of the pilot specification and the performance of the mixtures.
Acknowledgements The following people have been instrumental in completing the research presented here: Dr. Bob Klutzz Kraton Polymers Commercial Asphalt Co. Minnesota Pike Industries - New Hampshire Continental Paving - Vermont
THANK YOU!