Warm Mix Asphalt (WMA) Update

Transcription

1 Warm Mix Asphalt (WMA) Update Thomas Bennert, Ph.D. Research Professor Rutgers University Center for Advanced Infrastructure and Transportation ()

2 Presentation Outline National Perspective New Jersey Perspective Moving Forward Other Uses

3 WMA Benefits Reduced Emissions and Fumes Reduced Energy Consumption Improved Workability Extending Paving Window Cold Weather Paving Compaction Aid/Improve Compaction Quality

4 WMA Technologies In 2005

5 WMA Technologies At the end of

6 Technologies Currently Marketed in U.S. Material Processing (LEA) Organic Additives (Waxes, Zeolite) Chemical Additives (Surfactants) Foam Processing (Water Injection, Zeolite) Hybrid Systems (Water+Surfactant)

7 Information on Technologies

8 More Information WMA Best Practices, 3 rd Edition Technologies Stockpile Handling Burner Adjustments Aggregate Drying/Baghouse Temps Drum Slope/Flighting RAP Usage Placement Changes

9 NATIONAL PERSPECTIVE

10 Researching WMA on National Level - NCHRP

11 NCHRP Project 9-43 Appendix to AASHTO R35 to conducting WMA specific mixture design Requires designing the WMA, with RAP and WMA technology, at anticipated temperatures Uses Superpave guidelines Includes performance testing, coating and workability evaluation

12 NCHRP Project 9-47A Evaluated 14 in-place and newly constructed WMA projects all having companion HMA Various technologies Evaluated loose mix performance Field density Field performance (limited to the time frame of the project < 5 years)

13 Fuel Savings Comparative fuel usage reported for 15 projects representing six WMA technologies Theoretical calculations indicate a 50 F reduction in production temperature should result in an 11% reduction in fuel usage Observed savings ranged from a 15.4% increase to 77% reduction, with an average savings of 24% Heat losses and other inefficiencies believed to account for increased savings over theoretical calculations Energy can also be conserved by simply using dryer aggregates!

14 Preliminary Data from NCHRP 9-47A Project Technology Average Production Temp. F Walla Walla, WA Average Fuel Usage, DTH/ton Reduction, % HMA NA AQUABlack Foam Rapid River, MI HMA NA Advera Evotherm 3G Baker, MT HMA NA Evotherm DAT Griffith, IN HMA NA Ultrafoam GX Evotherm DAT Wax

15 NCHRP 9-47A Lab Findings Same in-place densities as HMA Lab rutting higher for WMA than HMA TSR s 40% of time lower, rest the same Lab stiffness lower for WMA than HMA Lab fatigue resistance better for WMA than HMA Slightly better resistance to low temperature cracking for WMA in lab

16 NCHRP 9-47A Field Findings Projects 2.5 to 5.5 Years Old (3 200 ft sections) All sections showed some distress No cracking in 1 or 5 projects Max crack length 1310 ft (St. Louis) Zeolite Max rutting of 6 mm (0.24 inches) Projects < 1 Year old (3 200 ft sections) No cracking in 5 of 6 projects No rutting in 3 of 6 projects Max crack length of 14 ft Max rutting of 2.5 mm (0.1 inches)

17 NCHRP 9-47A Mix Design All field projects evaluated used a drop in method for WMA Project also looked at AASHTO Appendix to R35 Average optimum AC% decreased almost 0.3% for WMA compare to HMA Lower rutting resistance for lab-produced material

18 NCHRP 9-47A - Summary Continue to use drop in procedure Reduction in AC% is resultant of extra compactability due to WMA - tricking gyratory Superpave mixes dry enough already Field showed excellent rutting resistance although lab testing does pick up initial differences Do these differences quickly disappear with inservice life?

19 National Perspective On-going research building on these findings Moisture Damage Established Long Term WMA Pavement Performance sections Short-term aging in plants Long-term aging in the field

20 NJDOT PERSPECTIVE

21 NJDOT Perspective Conducting both laboratory research and pilot program evaluation Laboratory Research Polymer Degradation Appendix R35 for NJ mixes General rutting and fatigue cracking performance Pilot Program Plant produced WMA and companion HMA Rutting, fatigue, stiffness, and moisture damage

22 Polymer Degradation? WMAT 1 Polymer Peak Binder Peak M n M w M n M w Original RTFO at 133 C RTFO at 163 C WMAT 2 Polymer Peak Binder Peak M n M w M n M w Original RTFO at 133 C Drop in molecular weight represents a degradation in polymer RTFO at 163 C PG Polymer Peak Binder Peak (Control) M n M w M n M w Original RTFO at 133 C RTFO at 163 C

23 Molecular Weight Polymer Peaks Drop in molecular weight represents a degradation in possible polymer

24 Molecular Weight Results All binders showed a reduction in Molecular Weight going from 133C to 163C (current RTFO standard) conditioning 42% for Evotherm 13% for Sasobit 29% for normal Evidence that reduced production temperatures may help in reducing polymer degradation

25 NJDOT Appendix to R35 Looked at NJDOT Approved JMF 2 RAP contents Normal (315F mixing) Advera, Sasobit, Evotherm (275F mixing) 0 and 25% RAP contents Determined Optimum asphalt content Rutting resistance, fatigue resistance, and TSR

26 NJDOT - Appendix R35 For virgin mixes, an average 0.45% reduction in optimum AC% was found Function of extra lubricity in the mixture due to the WMA technology For 25% RAP mixes, no change was found Does this mean the 25% RAP mixes were underasphalted if same level of lubricity occurred in both mixes?

27 How to Ensure Not Under- Asphalted in Field Allow mix to cool, or condition, at expected and slightly lower compaction temperatures Example: Sampled from back of truck at 280 o F, allow to cool to 265 to 260 o F prior to gyratory compaction Reduce low end of allowable air voids to 2.5% (currently 3 to 5% during production) Specify no adjustment (taking out AC%) to increase compacted air voids

28 NJDOT Appendix to R35 Mixture Performance - Rutting Rutting resistance in similar for WMA mixtures HMA mixtures higher All WMA mixtures achieved higher Flow Number than minimum required for respective traffic level <3 N.A. 3 to < to < Traffic Level, Million ESAL's Minimum Flow Number

29 NJDOT Appendix to R35 Mixture Performance Fatigue Cracking When using WMA, all fatigue cracking results improved 0% RAP at HMA temperatures were found to be statistically equal to 25% RAP at WMA temperatures Based on optimum AC% found during mixture design 25% RAP WMA were approximately 0.5% higher in asphalt content

30 NJDOT Appendix to R35 Mixture Performance Moisture Damage (T283) Moisture Damage Resistance: TSR values were all found to meet the minimum 80% requirements 2 just under but would meet requirements when considering repeatability of test Tensile strengths lower for WMA mixtures

31 NJDOT WMA Specification (Pilot)

32 NJDOT Pilot Projects Seven (7) WMA projects were evaluated from 2012 paving season 4 Evotherm, 4 Foamed Rt M64 Rt M64 I M76 Rt M64 (3 sections) (WMA-SMA) - Fiberless (WMA-SMA) (WMA-SMA) - Fiberless

33 Summary of NJDOT WMA Pilot Studies Moisture Damage (T283) All projects had passing TSR values except 1 both HMA and WMA failed HMA = 74.5%; WMA = 42.4% Rutting Resistance (Flow Number) HMA has shown higher rutting resistance, but similar to NCHRP study, WMA mixtures met the minimum Flow Number per traffic level Fatigue Resistance (Overlay Tester) All WMA except 1 project had superior Overlay Tester results Was same project as failed TSR

34 MOVING FORWARD OTHER USES FOR WMA

35 Emissions Reduction Looked at quantifying emissions reduction at paver with and without WMA Used portable emissions tester mounted to railing on back of paver (where workers would stand)

36 Example of Typical Emissions at Paver (AR-OGFC on I-78)

37 Rapid River, MI Evotherm 3G Advera WMA

38 Rapid River, MI Stack Emissions - % Reduction Emission Condensables, lb/hr Advera WMA Evotherm 3G CO 2, % 11 6 CO, lb/ton SO 2, lb/ton NO x, lb/ton 11 1 VOC, lb/ton 47 45

39 THIN LIFT PAVEMENTS PREVENTATIVE MAINTENANCE

40 General Thin-Lift HMA Cooling (MultiCool 3.0) Placed Immediately Over PCC Air and Pavement Temperature = 45F 1-Inch Thick 2-Inch Thick Temperature (F) minutes 25 minutes Time After Placement (minutes)

41 REDUCTION OF CRACK/JOINT SEALANT SWELLING

42 Paving Over Crack/Joint Sealants Due to high temperatures associated with HMA, crack/joint sealants generally soften and swell causing bumps in pavement Reducing temperatures below softening point can elevate problem.

43 Paving over Crack Sealant West Bend Airport WMA with 20% RAP Photos c/o Payne and Dolan

44 ELIMINATING FIBERS FROM SMA & OGFC MIXTURES

45 Removing Fibers in WMA Addition of fibers required to resist draindown of asphalt binder in gap-graded mixes Complaints regarding handling issues and proper distribution of fibers in the mix

46 Draindown Test (AASHTO T305) g minutes Temperatures Plant 15 C (27 F) above Criteria max. 0.30%

47 Draindown Laboratory Evaluation 325F with Fibers = 0.08% Draindown 325F without Fibers = 0.19% Draindown

48 Draindown Laboratory Evaluation 290F without Fibers = 0.08% Draindown 255F without Fibers = 0.06% Draindown

49 Draindown Results Mixture ID Temperature (F) Percent Mixing Testing Draindown Normal SMA WMA SMA #1 (No Fibers) WMA SMA #2 (No Fibers) WMA SMA #3 (No Fibers)

50 WMA to Eliminate Fibers WMA technology used to reduce temperatures and achieve density Reduction of production temperature increases viscosity of binder Increased viscosity adheres to aggregate better resulting in lower draindown

51 Summary Enough national and regional research to indicate WMA can perform as well as HMA Laboratory testing able to pick up differences but do how long do these differences exist Continue to monitor sections in NJ NCHRP 9-47A and NJDOT research indicates no need to have specific WMA mix design procedure Continue with drop in procedure WMA also has potential to help with other specific needs in NJ Thin-lift mixes, eliminating fibers in SMA, reducing emissions/odors of asphalt rubber mixtures

52 Thank you for your time! Thomas Bennert, Rutgers U.