warm mix asphalt “the material of today” - rmaces · warm mix asphalt “the material of...

Warm Mix Asphalt “The Material of Today”

Jason Dietz Pavement & Materials Engineer

Office of Technical Services – FHWA Resource Center, Lakewood,

CO [email protected]

Tyler Francis Technical Marketing Manager –

KS/NE/CO Ingevity Pavement Technologies –

[email protected]

Key Topics of Discussion What is WMA?

WMA Technologies

WMA Mix Design

Production and Placement of WMA

Resources

2

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.

WMA Investigation and Implementation Premise

3

What is WMA?

Warm Mix Asphalt (WMA)

+ +

Aggregate Recycled Asphalt Pavement

or RAP (Optional)

Additives (Optional)

= Warm Mix Asphalt (WMA)

+

Asphalt Binder

Polymers, Shredded Rubber, etc.

Produced at lower temperatures (30 to 100oF). 5

• 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.

FHWA Definition

6

• 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

Why WMA? **Advantages will only be realized by optimizing production operations and utilizing best practices

7

• Potential Advantages** – Energy Savings?? – Decreased Emissions


Ageing?? – Extended Paving Season – Long Haul Distances – Compaction Aid – Increased RAP usage??


8





• Potential Risks – Incomplete Aggregate

Drying – Premature Rutting – RAP/RAS Blending – Production Concerns

• Burner tuning – Emissions – Fuel

• Baghouse • Production rate • Best practices

– Mix Design 9





• Potential Risks – Incomplete Aggregate

Drying – Premature Rutting?? – RAP/RAS Blending – Production Concerns

• Burner tuning – Emissions – Fuel

• Baghouse • Production rate • Best practices

– Mix Design 10

WMA Technologies

Where have we been?

2004-05 Number of named WMA technologies in the U.S.?

2014-16 Number of named WMA technologies in the U.S.?

12

KOLO

Mathy Tech. & Eng. Services and Paragon Technical Services, Inc

**FHWA does not endorse any particular proprietary product or technology. Other named technologies are also available in the market.

Lake Asphalt of Trinidad and Tobago

U.S. Technology Market**

13

http://www.pqcorp.com/pqhome.asp

http://www.meekerequipment.com/index.htm

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

• 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.

How Does WMA Work?

15

• Astec’s Double Barrel Green System

• Gencor Green Machine Ultrafoam GX

• Aspha-Min

• Advera

Foaming Additives/Processes

16

• It is a drum plant that is retrofitted with a multi-nozzle 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.

Double Barrel Green System

17

Reported WMA

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

2009 2010

Chemical Additive %Additive Foaming %Plant Foaming %Organic Additive %

NAPA

Foaming Device

18

EXAMPLE FOAMING DEVICE

19

Foaming Warm Mix Process

Expansion Chamber

Water Pump

Existing AC Pump

Counterflow Drum

Water Tank Foam Injection pipe running along side existing AC pipe

Existing AC pipe

20

WMA Dosing • Refer to product

manufacturer for dosage rates

• Ensure injection systems are cleaned and calibrated regularly for accurate dosing

21

• 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 30oF.

Double Barrel Green System

22

EXAMPLE FOAMING NOZZLE

EXAMPLE

25

• 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.

Gencor Green Machine Ultrafoam GX

26

Gencor Green Machine Ultrafoam GX

27

• 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.

Aspha-Min

28

• 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.

Aspha-Min

29

• Temperature reduction of 50oF is expected. Aspha-Min

30

Plant Addition of Aspha-min

31

• 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).

Advera

32

Advera

33

• Sasobit

• Evotherm

• Rediset LQ

• SonneWarmix

Organic/Chemical Additives

34

• 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., 239oF).

• At ambient temperatures it forms a crystalline structure that might improve mix fatigue resistance.

Sasobit

35

• The optimum Sasobit dosage ranges between 3 to 4 percent by weight of asphalt binder.

• Temperature reduction between 15 to 50oF.

Sasobit

36

Plant Addition of Sasobit

37

• There are three different types of Evotherm:

– Evotherm Emulsion Technology (ET)

– Evotherm Dispersed Asphalt Technology (DAT)

– Evotherm Third Generation (3G/Revix)

Evotherm

38

• 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.

Evotherm Emulsion Technology

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 – Low odor

Hydrophillic head

Asphalt

Hydrophobic tail

• Evotherm DAT is similar to Evotherm ET in the sense that it also uses water-based asphalt emulsion

• However, this technology inject the emulsion directly into the asphalt line within a plant.

Evotherm Dispersed Asphalt Technology

41

Chemical Additives • May be added at the

asphalt terminal or added at the plant

• Dosage rates depend on the selected additive

42

• 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.

Evotherm 3G/Revix

43

• 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 100oF.

Evotherm

44

• 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.

Rediset LQ

45

• 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 60oF.

Rediset LQ

46

Rediset LQ Video

47

• 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.

SonneWarmix

48

• 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 50oF.

SonneWarmix

49

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.

WMA Mix Design

51

• 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-283

WMA Mix Design

52

• 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.

WMA Mix Design

53

• 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

WMA Mix Design

54

• 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

• 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 – www.cdot.gov/business/apl/asphalt-warm-mix.html – 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

CDOT WMA Requirements

56

http://www.cdot.gov/business/apl/asphalt-warm-mix.html

• 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

CDOT WMA Mix Design

57

• Original Project 9-43 – Binder Absorption limited to 0.5 - 1.0 %

• 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

Expansion of NCHRP 9-43 Mix Design Study to Higher Absorption Mixtures

58

HMA

330°F

WMA

240°F

Mix Design Considerations

59

• 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

CDOT WMA Mix Design

60

• 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

WMA Technology Selection

61

WMA Technologies

62

Conventional Hot Mix

250ºF

200ºF

350ºF

300ºF

Ambient

Surfactant WMA

Wax WMA

Foamed Asphalt

• 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

CDOT WMA Technology

63

AASHTO R35 Key Differences: Materials Selection

64

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

AASHTO R35 Key Differences Design

65

Item HMA WMA Mixing & Compaction Temperatures

Viscosity Coating Compactability

Specimen Preparation

Standard Process specific

Optimum Binder Content

AASHTO M323 Volumetrics

AASHTO M323 Volumetrics

WMA Mix Design Categories

Additive added to the binder

Additive added to the mixture

Wet aggregate mixtures

Foamed asphalt mixtures 66

Additional Equipment?

Low Shear Binder Mixer

Laboratory Foaming Equipment

Mechanical Mixer

67

Commercially Available Laboratory Foaming Devices

InstroTek, Inc. – AccuFoamer

PTi – THE FOAMER

Wirtgen, WLB 10 S

68

AASHTO R35 Key Differences: Evaluation

69

Item HMA WMA Coating Viscosity AASHTO T195 Compactability Viscosity Measured Moisture Sensitivity AASHTO T283 AASHTO T283

Rutting Resistance None Flow Number Test

Published as Appendix

within AASHTO TP 79-13

AMPT Flow Number standardization

Determining the Dynamic

Modulus and Flow Number for Asphalt Mixtures

Using the Asphalt Mixture

Performance Tester (AMPT)

70

Production and Placement of WMA

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

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

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

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

HMA at 50ºF

HMA has only 19 minutes of

paving time until the minimum compaction

temperature is reached.

19 Minutes

76

WMA at 50ºF

35 Minutes

WMA has 35 minutes until the

minimum compaction

temperature is reached.

> 80% Increase in compaction

time

77

WMA at 1ºF

21 Minutes

It would have to be 1°F

outside for WMA to

behave like HMA at 50 °F!

78

WMA Construction Differences?

WMA is NOT a cure for bad construction practices.

82

Resources

Where have we been?

2004-05 No. of WMA Technical Working Groups?

2014-16 No. of WMA Technical Working Groups?

84

Stakeholder Engagement: WMA Technical Working Group

FHWA

NAPA

Industry

State DOT

State APA NCAT

AASHTO

Labor

NIOSH

Co-Chairs: Matthew Corrigan

Ron White

Established in 2005 Adjourned in 2012

http://warmmixasphalt.com/Default.aspx

Where have we been?

2004-05 No. of WMA International Conferences?

2014-16 No. of WMA International Conferences?

86

International WMA Conferences 1st Conference on November 11-13, 2008 in

Nashville, TN Processes, Mix Production & Placement, Energy consumption, Mix Design, Material Properties

2nd 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.

FHWA International WMA Scan Tour • Joint Program with FHWA, AASHTO, NCHRP, and Industry • Publication FHWA-PL-08-007 • Scan Final Report

– .pdf available at

http://international.fhwa.dot.gov/pubs/pl08007/index.cfm



Where have we been?

2004-05 Number of WMA NCHRP Research Projects?

Feb 2017 Number of WMA NCHRP Research Projects?

89

9-43 $522,501 completed 9-47 $79,000 completed 9-47A $1,121,000 completed 9-49 $450,000 completed 9-49A $900,000 completed 9-52 $800,000 completed 9-53 $700,000 completed 9-54 $800,000 Phase 2 Underway

9-55 $600,000 Phase 2 Underway

9-58 $1,500,000 Oct 2017 20-07 (311) $50,000 completed 20-44 (01) $150,000 Jan 2018

NCHRP Projects funded as a result of WMA TWG efforts: -Mix Design Practices for WMA

-Engineering Properties, Emissions, and Field Performance of WMA Technologies -Properties and Performance of WMA Technologies -Performance of WMA Technologies: Stage I--Moisture Susceptibility -Performance of WMA Technologies: Stage II--Long-Term Field Performance -Short-Term Laboratory Conditioning of Asphalt Mixtures -Properties of Foamed Asphalt for Warm Mix Asphalt Applications -Long-Term Aging of Asphalt Mixtures for Performance Testing and Prediction -Recycled Asphalt Shingles in Asphalt Mixtures with WMA Technologies -Effects of Recycling Agents on Asphalt Mixtures w/High RAS & RAP Binder Ratios -Development of a WMA Tech. Evaluation Program -Increasing WMA Implementation by Leveraging State-of-Knowledge

http://www.trb.org/default.asp

• Products: – 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 09-33 Mix Design Manual – “Standard Practice For Measuring Properties

of Warm Mix Asphalt (WMA) for Performance Analysis Using the AASHTO MEPDG” (AASHTO PavementME™ Software)

NCHRP Project 09-43

http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=977 92

• NCHRP 20-07/ Task 311 Development of a Warm Mix Asphalt Technology Evaluation Program – Myers McCarthy Consulting Engineers, LLC – http://apps.trb.org/cmsfeed/TRBNetProjectDispla

y.asp?ProjectID=3075

• AASHTO NTPEP Program for evaluating WMA technologies was developed www.ntpep.org

93

http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=3075


http://www.ntpep.org/

• NCHRP 20-44 (01) Increasing WMA Implementation by Leveraging State-of-Knowledge – Myers McCarthy Consulting Engineers, LLC – PI: Leslie Myers McCarthy, Ph.D, P.E. – http://apps.trb.org/cmsfeed/TRBNetProjectDispla

y.asp?ProjectID=588

WMA’s Newest 2017 NCHRP Project

94



Where have we been?

2004-05 Number of WMA Best Practices Publications?

2014-16 Number of WMA Best Practices Publications?

95

Quality Improvement Series 125

3rd Edition – Stockpile Moisture

Management – Burner Adjustments and

Efficiency – Aggregate Drying and

Baghouse Temperatures – Drum Slope and Flighting – Combustion Air – RAP usage – Placement Changes

96

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

Where have we been?

2004-05 Number of AASHTO Standards on WMA?

2014-16 Number of AASHTO Standards on WMA?

98

Approved by AASHTO Subcommittee on Materials and published: Standard Specifications for Transportation Materials and Methods of Sampling and Testing (32nd Edition, 2012)

Appendix to AASHTO R35 with commentary “Special Mixture Design Considerations and Methods for WMA”

99

100

Course Number: FHWA-NHI-131137

Where have we been?

2004-05 Number of WMA tons produced annually?

2015 Number of WMA tons produced annually?

101

Information Series 138

www.asphaltpavement.org/recycling

6th Annual Asphalt Pavement Industry Survey on Recycled

Materials and Warm-Mix Asphalt Usage: 2015 (release

pending)

Product of FHWA & NAPA Cooperative Agreement Contract

102

WMA Usage in HMA/WMA Percentage of Total Mix Production in USA

0%5%

10%15%20%25%30%35%

2009 2010 2011 2012 2013 2014 2015

5% 11%

30% 32% 33%

16.8 41.1

19%

68.7 86.7 2006

WMA trials begin

Total asphalt mix: (million tons)

24%

358.4 359.8 366.0 360.3 350.7

106.4 113.8 (million tons)

352.0

Total WMA Produced

119.8

364.9

103

State DOT WMA Usage in HMA/WMA Percentage of State Mix Production in USA

0%5%

10%15%20%25%30%35%40%

2009 2010 2011 2012 2013 2014 2015

5% 12%

35% 35% 37%

8.6 20.0

20%

34.6 46.4 2006

WMA trials begin

Total asphalt mix: (million tons)

26%

169.2 172.5 175.3 179.1

160.1

55.7 56.9 (million tons)

160.2

Total WMA Produced

60.9

163.6

104

Organic AdditiveAdditive Foaming

Chemical AdditivePlant Foaming

0

20

40

60

80

100

2009 2010 2011 2012 2013 2014 2015

WMA Usage by Technology Percent of market for WMA production in USA

105

Where have we been?

2004-05 Number of WMA projects evaluated by FHWA?

2014-16 Number of WMA projects evaluated by FHWA?

106

What questions do you have?

107

Thank you!

For Questions/Comments:

108

warm mix asphalt “the material of today” - rmaces · warm mix asphalt “the material of...

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