Warm Mix Asphalt The Material of Today

Transcription

1 Warm Mix Asphalt The Material of Today Jason Dietz Pavement & Materials Engineer Office of Technical Services FHWA Resource Center, Lakewood, CO Tyler Francis Technical Marketing Manager KS/NE/CO Ingevity Pavement Technologies

2 Key Topics of Discussion What is WMA? WMA Technologies WMA Mix Design Production and Placement of WMA Resources 2

3 WMA Investigation and Implementation Premise Although there are many factors driving the development and implementation of WMA technologies globally, in order for WMA to succeed in the U.S., WMA pavements must have equal or better performance when compared to traditional HMA pavements. 3

4 What is WMA?

5 Warm Mix Asphalt (WMA) Asphalt Binder Aggregate Recycled Asphalt Pavement or RAP (Optional) Additives (Optional) Polymers, Shredded Rubber, etc. = Warm Mix Asphalt (WMA) Produced at lower temperatures (30 to 100 o F). 5

6 FHWA Definition Warm Mix Asphalt (WMA) is the generic term for a variety of technologies that allow producers of Hot Mix Asphalt (HMA) pavement material to lower temperatures at which the material is mixed and placed on the road. 6

7 Why WMA? **Advantages will only be realized by optimizing production operations and utilizing best practices Potential Advantages** Energy Savings Decreased Emissions Visible and Non-Visible Decreased Fumes Decreased Binder Ageing Extended Paving Season Long Haul Distances Compaction Aid Increased RAP usage 7

8 Why WMA? **Advantages will only be realized by optimizing production operations and utilizing best practices Potential Advantages** Energy Savings?? Decreased Emissions Visible and Non-Visible Decreased Fumes Decreased Binder Ageing?? Extended Paving Season Long Haul Distances Compaction Aid Increased RAP usage?? 8

9 Why WMA? **Advantages will only be realized by optimizing production operations and utilizing best practices Potential Advantages** Energy Savings?? Decreased Emissions Visible and Non-Visible Decreased Fumes Decreased Binder Ageing?? Extended Paving Season Long Haul Distances Compaction Aid Increased RAP usage?? Potential Risks Incomplete Aggregate Drying Premature Rutting RAP/RAS Blending Production Concerns Burner tuning Emissions Fuel Baghouse Production rate Best practices Mix Design 9

10 Why WMA? **Advantages will only be realized by optimizing production operations and utilizing best practices Potential Advantages** Energy Savings?? Decreased Emissions Visible and Non-Visible Decreased Fumes Decreased Binder Ageing?? Extended Paving Season Long Haul Distances Compaction Aid Increased RAP usage?? Potential Risks Incomplete Aggregate Drying Premature Rutting?? RAP/RAS Blending Production Concerns Burner tuning Emissions Fuel Baghouse Production rate Best practices Mix Design 10

11 WMA Technologies

12 Where have we been? Number of named WMA technologies in the U.S.? Number of named WMA technologies in the U.S.? 12

13 U.S. Technology Market** KOLO Mathy Tech. & Eng. Services and Paragon Technical Services, Inc Lake Asphalt of Trinidad and Tobago **FHWA does not endorse any particular proprietary product or technology. 13 Other named technologies are also available in the market.

14 WMA TECHNOLOGIES Water-based additive Foaming process: water, which is added to the hot binder, turns into steam allowing the expansion of the binder. This allows the viscosity of the foamed binder to be significantly reduced. WMA-Foam and the Double Barrel Green Water-bearing additive induce foaming mechanisms in the asphalt binder using water bearing additives Aspha-min and Advera Organic additive Sasobit, Sasoflex and Asphaltan B Chemical additive reduction of internal friction between the asphalt binder, aggregate Evotherm DAT, Evotherm 3G, and REVIX 14

15 How Does WMA Work? WMA technologies reduce the viscosity of the asphalt binder so that aggregates can be coated at lower temperatures. The key is the addition of additives (water-based, water-bearing, organic, chemical, or hybrids) to the asphalt mix. The additives allow the asphalt binder and aggregates to be mixed at lower temperatures. Reducing the viscosity also makes the mixture easier to manipulate and compact at lower temperature. 15

16 Foaming Additives/Processes Astec s Double Barrel Green System Gencor Green Machine Ultrafoam GX Aspha-Min Advera 16

17 Double Barrel Green System It is a drum plant that is retrofitted with a multinozzle foaming device. This system requires no additives as it directly inject hot asphalt with cold water particles. To be more specific, as the asphalt binder is flowing through the foaming chambers in the multi-nozzle foaming device, cold water is injected into it through a series of stainless steel injectors located above these foaming chambers. 17

18 Reported WMA Foaming Device 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Chemical Additive % Additive Foaming % Plant Foaming % Organic Additive % NAPA 18

19 EXAMPLE FOAMING DEVICE 19

20 Foaming Warm Mix Process Counterflow Drum Existing AC Pump Expansion Chamber Water Tank Water Pump Existing AC pipe Foam Injection pipe running along side existing AC pipe 20

21 Refer to product manufacturer for dosage rates Ensure injection systems are cleaned and calibrated regularly for accurate dosing WMA Dosing 21

22 Double Barrel Green System The injection of cold water causes the asphalt binder to expand; thus, creating what is known as foamed asphalt. The amount of water injected into the asphalt binder is controlled through a positive displacement piston pump which accurately measures the amount of water going into the system. Temperature reduction around 30 o F. 22

23 EXAMPLE FOAMING NOZZLE

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25 EXAMPLE 25

26 Gencor Green Machine Ultrafoam GX It is an asphalt foaming system that can be attached to asphalt plants. Usually attached to the 3 or 4-inch asphalt injection line already present in drum plants. The system injects water into the asphalt causing to foam. The system is jacketed with a hot oil jacket that would preserve the temperature of the heated asphalt binder during production. 26

27 Gencor Green Machine Ultrafoam GX 27

28 Aspha-Min It is a synthetic zeolite that contains approximately 20 percent of crystallized water within its structure. Introduced during the mixing process shortly after or at the same time the asphalt binder is added into the mixing chamber. As the temperature of Aspha-min gradually increases, the water contained inside its structures starts to release in the form of steam causing the asphalt binder to foam. 28

29 Aspha-Min As a result of this foaming process, the viscosity of the asphalt binder is reduced; thus, facilitating the use of lower than traditional production temperatures. Recommended dosage is 0.3% by weight of total mix. A special distribution unit is needed to ensure uniform dispersion of Aspha-Min during mixing. 29

30 Aspha-Min Temperature reduction of 50 o F is expected. 30

31 Plant Addition of Aspha-min 31

32 Advera Another synthetic zeolite that contain about 18 percent of crystallized water, by total weight, inside its structure. Similar to Aspha-Min; however, Advera has smaller particle size (i.e., passing sieve #200). 32

33 Advera 33

34 Organic/Chemical Additives Sasobit Evotherm Rediset LQ SonneWarmix 34

35 Sasobit It is a synthetic wax that is produced through the coal gasification process. Blended with the asphalt binder prior to mixing. Sasobit reduces the viscosity of the asphalt binder at temperatures above its melting point (i.e., 239 o F). At ambient temperatures it forms a crystalline structure that might improve mix fatigue resistance. 35

36 Sasobit The optimum Sasobit dosage ranges between 3 to 4 percent by weight of asphalt binder. Temperature reduction between 15 to 50 o F. 36

37 Plant Addition of Sasobit 37

38 There are three different types of Evotherm: Evotherm Evotherm Emulsion Technology (ET) Evotherm Dispersed Asphalt Technology (DAT) Evotherm Third Generation (3G/Revix) 38

39 Evotherm Emulsion Technology Facilitates producing WMA through introducing water-based emulsion into the hot aggregate during mixing. Contact with hot aggregates will turn the water-based emulsion into steam; thus, forcing the asphalt to expand. 39

40 Evotherm uses natural chemicals derived from pine trees. Additives are comprised of specialty surfactants derived from pine trees. Specifically developed for use in asphalt applications Heat stable High flash point Asphalt Low odor Hydrophillic head Hydrophobic tail 40

41 Evotherm Dispersed Asphalt Technology Evotherm DAT is similar to Evotherm ET in the sense that it also uses waterbased asphalt emulsion However, this technology inject the emulsion directly into the asphalt line within a plant. 41

42 Chemical Additives May be added at the asphalt terminal or added at the plant Dosage rates depend on the selected additive 42

43 Evotherm 3G/Revix Utilizes a water-free chemical additive package that does not reduce the viscosity of the asphalt binder. This chemical additive only works on reducing the internal friction of the mixture; thus, allowing the asphalt binder to behave as if it was heated to a high temperature. 43

44 Evotherm Optimum dosage of any of the Evotherm technologies ranges between 0.4 to 0.7% by total weight of asphalt binder. Temperature reduction between 50 to 100 o F. 44

45 Rediset LQ Another chemical that can be used to produce asphalt mixture at lower than traditional. Utilizes surfactants contained in it to reduce surface tension of the asphalt binder. This enables coating the aggregates at lower temperatures. 45

46 Rediset LQ Optimum dosage of Rediset LQ ranges between 0.25 to 0.75 percent by weight of effective asphalt binder content. Temperature reduction ranges between 40 to 60 o F. 46

47 Rediset LQ Video 47

48 SonneWarmix A wax-based WMA additive that is composed of paraffinic hydrocarbons. Can be pre-blended with the asphalt binder at the binder terminal or directly introduced into the liquid binder stream at the suction pump while utilizing the pump to do the required mixing. 48

49 SonneWarmix Similar to Sasobit in terms of mechanism for producing WMA. The optimum dosage rate ranges between 0.5 to 1.5 percent by total weight of asphalt binder. Temperature reduction of 50 o F. 49

50 WMA Mix Design

51 WMA Mix Design The procedure for selecting the aggregate gradation and optimum binder content for WMA is similar to that of HMA. Performance of the two mixture might be significantly different. Therefore, there is a need to evaluate rutting, fatigue cracking, and moisture susceptibility of WMA mixtures. Refer to NCHRP Report 691 for more information. 51

52 WMA Mix Design Many state DOT s allow the use of Chemical WMA in lieu of Liquid Anti-Strip and Lime if TSR s requirements are met. Nebraska Dept of Roads, Kansas DOT, and more Pikes Peak Regional Transportation Authority CDOT has slightly different procedure for moisture susceptibility vs AASHTO T

53 WMA Mix Design Certain WMA additives may impact viscosity of the binder, gradation of the mixture (P200), or PG grade of the virgin binder Most designs can be built at HMA temperatures. Many suggest mixing & compaction temperatures should be ~250F. Chemical WMA designs have been built when volumetrics did not change when mixed & compacted from 190F to 240F to 310F. 53

54 WMA Mix Design SMA & OGFC mixtures have been designed without fibers when using low temperature WMA. Rutgers & Clemson research With lower temperatures, binder viscosity increases allowing reduced or eliminated drain-down Balance between coating and drain-down 54

55 Virgin PG Grade may be adjusted when using WMA Reduced binder oxidation Higher recycle content may be allowed DOT s are changing specifications allowing more recycle or not requiring a binder grade dump when mix is produced below 275F. TXDOT --- specification in place Iowa DOT --- draft WMA Mix Design 55

56 CDOT WMA Requirements Revision of Section 403 HMA Spec does not change established CDOT bid items Allows use of any APPROVED WMA WMA Approval Process in CO Process 59 Detailed Product Description Performance History / Contractor Experience Mix Design Considerations Plant & Production Considerations Contact Information Checklist for CP-59: facilitates initial review of all submittals 56

57 CDOT WMA Mix Design Mix Design & Approval: HMA Design with WMA drop-in if low absorption WMA Design if high absorption Technologies are CDOT-approved for unlimited tonnage after field performance is documented Technologies with tonnage limits may become unlimited after required performance is documented 57

58 Expansion of NCHRP 9-43 Mix Design Study to Higher Absorption Mixtures Original Project 9-43 Binder Absorption limited to % ETG Work Item: Expansion to Higher Absorption Mixtures 2.0% Includes High Absorption Lab Foamed Mix Completed by Dr. Ray Bonaquist, AAT Confirmed impact of WMA on mixture volumetrics and performance during design and AASHTO R 35 WMA Appendix 58

59 Mix Design Considerations WMA 240 F HMA 330 F 59

60 CDOT WMA Mix Design Binder Supplier Certification Requirements were revised requiring certified binder suppliers to have in place QC procedures, when introducing WMA additives at their load-out facilities CP-59 WMA Approval Procedure improved over the years to clarify the following: Required performance documentation for unlimited use of WMA Process for setting AC & Voids targets when WMA is used 60

61 WMA Technology Selection WMA mix design requires the producer to select WMA product/technology Planned production temperature Planned field compaction temperature Producer should consider Past performance and technical support Cost Useful temperature range Production rates Plant Operation and Modifications 61

62 WMA Technologies Conventional Hot Mix Surfactant WMA 350ºF 300ºF 250ºF 200ºF Foamed Asphalt Wax WMA Ambient 62

63 CDOT WMA Technology 13 WMA Technologies currently approved 10 Additives (5 having tonnage limits) 3 Foam (2 having tonnage limits) 15 Contractors certified for WMA production 5 are foam only All others are certified for additives 63

64 AASHTO R35 Key Differences: Materials Selection Item HMA WMA WMA Process NA Producer Selected Gradation AASHTO M323 AASHTO M323 Aggregate AASHTO M323 AASHTO M323 Binder Selection PG Grade AASHTO M323 PG Grade AASHTO M323 RAP AASHTO M323 Compaction Temp 64

65 AASHTO R35 Key Differences Design Item HMA WMA Viscosity Mixing & Compaction Temperatures Specimen Preparation Optimum Binder Content Standard AASHTO M323 Volumetrics Coating Compactability Process specific AASHTO M323 Volumetrics 65

66 WMA Mix Design Categories Additive added to the binder Wet aggregate mixtures Additive added to the mixture Foamed asphalt mixtures 66

67 Additional Equipment? Mechanical Mixer Low Shear Binder Mixer Laboratory Foaming Equipment 67

68 Commercially Available Laboratory Foaming Devices Wirtgen, WLB 10 S PTi THE FOAMER InstroTek, Inc. AccuFoamer 68

69 AASHTO R35 Key Differences: Evaluation Item HMA WMA Coating Viscosity AASHTO T195 Compactability Viscosity Measured Moisture Sensitivity AASHTO T283 AASHTO T283 Rutting Resistance None Flow Number Test 69

70 AMPT Flow Number standardization Published as Appendix within AASHTO TP Determining the Dynamic Modulus and Flow Number for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT) 70

71 Production and Placement of WMA

72 WMA Construction Differences? Similar to HMA Uses same equipment and practices Some WMA need additional equipment Little to no difference in the delivery, hauling, laydown, and placement of WMA from HMA Construction best practices are the same and the key to performance 72

73 WMA Construction Suggestions Start hot & reduce after a few loads This will help heat up equipment Plant Trucks MTV / Pick up device Paver In order to reduce temperature contractor may increase production and/or reduce burner Watch amps on drag slat, coaters, etc Be observant of coating visual inspection Tarp trucks 73

74 WMA Construction Suggestions Reduction in stack emissions Total Organic Material reduced Drops Benzene Soluble Matter below detectible level Better environment for workers 50F-70F cooler than traditional HMA 74

75 WMA Construction Differences? Improved compaction Time available to meet density is increased Allows for longer haul Improved workability in low air & pavement temperature Numerous CDOT project examples of success using WMA Reduction in bumps from crack seal with thin lift overlays 75

76 HMA at 50ºF 19 Minutes HMA has only 19 minutes of paving time until the minimum compaction temperature is reached. 76

77 WMA at 50ºF 35 Minutes WMA has 35 minutes until the minimum compaction temperature is reached. > 80% Increase in compaction time 77

78 WMA at 1ºF 21 Minutes It would have to be 1 F outside for WMA to behave like HMA at 50 F! 78

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82 WMA Construction Differences? WMA is NOT a cure for bad construction practices. 82

83 Resources

84 Where have we been? No. of WMA Technical Working Groups? No. of WMA Technical Working Groups? 84

85 Stakeholder Engagement: WMA Technical Working Group Established in 2005 Adjourned in 2012 NIOSH FHWA NAPA Co-Chairs: Matthew Corrigan Labor Industry Ron White AASHTO State DOT NCAT State APA

86 Where have we been? No. of WMA International Conferences? No. of WMA International Conferences? 86

87 International WMA Conferences 1 st Conference on November 11-13, 2008 in Nashville, TN Processes, Mix Production & Placement, Energy consumption, Mix Design, Material Properties 2 nd Conference October 11-13, 2011 in St. Louis, MO Lab & Field Properties, Design & Performance, Health & Environment, RAP w/ WMA, Binder & Mix Properties, Moisture Susceptibility, Construction, etc.

88 FHWA International WMA Scan Tour Joint Program with FHWA, AASHTO, NCHRP, and Industry Publication FHWA-PL Scan Final Report.pdf available at /pubs/pl08007/index.cfm

89 Where have we been? Number of WMA NCHRP Research Projects? Feb 2017 Number of WMA NCHRP Research Projects? 89

90 NCHRP Projects funded as a result of WMA TWG efforts: Mix Design Practices for WMA $522,501 completed -Engineering Properties, Emissions, and 9-47 Field Performance of WMA Technologies $79,000 completed -Properties and Performance of WMA 9-47A $1,121,000 completed Technologies -Performance of WMA Technologies: 9-49 $450,000 completed Stage I--Moisture Susceptibility -Performance of WMA Technologies: 9-49A Stage II--Long-Term Field Performance $900,000 completed -Short-Term Laboratory Conditioning of 9-52 Asphalt Mixtures $800,000 completed -Properties of Foamed Asphalt for Warm 9-53 Mix Asphalt Applications $700,000 completed -Long-Term Aging of Asphalt Mixtures for 9-54 $800,000 Phase 2 Underway Performance Testing and Prediction -Recycled Asphalt Shingles in Asphalt 9-55 $600,000 Phase 2 Underway Mixtures with WMA Technologies -Effects of Recycling Agents on Asphalt 9-58 Mixtures w/high RAS & RAP Binder Ratios $1,500,000 Oct Development of a WMA (311) Tech. Evaluation Program $50,000 completed -Increasing WMA Implementation (01) by Leveraging State-of-Knowledge $150,000 Jan 2018

91 NCHRP Projects funded as a result of WMA TWG efforts: Mix Design Practices for WMA $522,501 completed -Engineering Properties, Emissions, and 9-47 Field Performance of WMA Technologies $79,000 completed -Properties and Performance of WMA 9-47A $1,121,000 completed Technologies -Performance of WMA Technologies: 9-49 $450,000 completed Stage I--Moisture Susceptibility -Performance of WMA Technologies: 9-49A Stage II--Long-Term Field Performance $900,000 completed -Short-Term Laboratory Conditioning of 9-52 Asphalt Mixtures $800,000 completed -Properties of Foamed Asphalt for Warm 9-53 Mix Asphalt Applications $700,000 completed -Long-Term Aging of Asphalt Mixtures for 9-54 $800,000 Phase 2 Underway Performance Testing and Prediction -Recycled Asphalt Shingles in Asphalt 9-55 $600,000 Phase 2 Underway Mixtures with WMA Technologies -Effects of Recycling Agents on Asphalt 9-58 Mixtures w/high RAS & RAP Binder Ratios $1,500,000 Oct Development of a WMA (311) Tech. Evaluation Program $50,000 completed -Increasing WMA Implementation (01) by Leveraging State-of-Knowledge $150,000 Jan 2018

92 Products: NCHRP Project Appendix to AASHTO R35 with commentary Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA) WMA Mix Design Workshop/Training Module Chapter on WMA Mix Design for the NCHRP Project Mix Design Manual Standard Practice For Measuring Properties of Warm Mix Asphalt (WMA) for Performance Analysis Using the AASHTO MEPDG (AASHTO PavementME Software) 92

93 NCHRP 20-07/ Task 311 Development of a Warm Mix Asphalt Technology Evaluation Program Myers McCarthy Consulting Engineers, LLC y.asp?projectid=3075 AASHTO NTPEP Program for evaluating WMA technologies was developed 93

94 WMA s Newest 2017 NCHRP Project NCHRP (01) Increasing WMA Implementation by Leveraging State-of- Knowledge Myers McCarthy Consulting Engineers, LLC PI: Leslie Myers McCarthy, Ph.D, P.E. y.asp?projectid=588 94

95 Where have we been? Number of WMA Best Practices Publications? Number of WMA Best Practices Publications? 95

96 Quality Improvement Series rd Edition Stockpile Moisture Management Burner Adjustments and Efficiency Aggregate Drying and Baghouse Temperatures Drum Slope and Flighting Combustion Air RAP usage Placement Changes 96

97 The following references detail specifics related to plant modifications and operational changes in order to maximize the benefits of WMA production: Quality Improvement Series 125 (QIP 125), Warm Mix Asphalt: Best Practices, Quality Improvement Series 126 (QIP 126), Energy Conservation in Hot Mix Asphalt Production Environmental Council 101 (EC-101), Best Management Practices to Minimize Emissions During HMA Construction The Fundamentals of the Operation and Maintenance of the Exhaust Gas System in a Hot Mix Asphalt Facility (IS-52) 97

98 Where have we been? Number of AASHTO Standards on WMA? Number of AASHTO Standards on WMA? 98

99 Appendix to AASHTO R35 with commentary Special Mixture Design Considerations and Methods for WMA Approved by AASHTO Subcommittee on Materials and published: Standard Specifications for Transportation Materials and Methods of Sampling and Testing (32nd Edition, 2012) 99

100 Course Number: FHWA-NHI

101 Where have we been? Number of WMA tons produced annually? 2015 Number of WMA tons produced annually? 101

102 Information Series th Annual Asphalt Pavement Industry Survey on Recycled Materials and Warm-Mix Asphalt Usage: 2015 (release pending) Product of FHWA & NAPA Cooperative Agreement Contract 102

103 WMA Usage in HMA/WMA Percentage of Total Mix Production in USA Total asphalt mix: (million tons) 35% 30% 25% 20% 15% 10% 5% 0% 2006 WMA trials begin % 11% 30% 32% 33% % 24% (million tons) Total WMA Produced 103

104 State DOT WMA Usage in HMA/WMA Percentage of State Mix Production in USA Total asphalt mix: (million tons) 40% 35% 30% 25% 20% 15% 10% 5% 0% 2006 WMA trials begin % 12% 35% 35% 37% % 26% (million tons) Total WMA Produced 104

105 WMA Usage by Technology Percent of market for WMA production in USA Plant Foaming Chemical Additive Additive Foaming Organic Additive 105

106 Where have we been? Number of WMA projects evaluated by FHWA? Number of WMA projects evaluated by FHWA? 106

107 What questions do you have? 107

108 Thank you! For Questions/Comments: 108