Panel Discussion: Tack Coat- Storage and Handling- Sampling and Testing2018 SCAPA Winter Conference

Bob Horan, PEAsphalt Institute

Timothy OwingsAssociated Asphalt

James RossBlacklidge Emulsions

•Why is tack coat a “must have” for asphalt pavement construction?

•NCHRP Synthesis: “Tack Coat Specifications, Materials and Construction Practices”•Authored by AI•Publication spring 2018

•Panel Discussion (questions and answers)•Storage and handling best practices•Sampling best practices

Our Visit Today

Tack Coat Workshops 2015-2016

2700 attendees in 47 workshops; 3100 in 35 presentations

SCDOT Tack Coat Workshop – November 2015

• The purpose of tack is to bond the asphalt pavement layer being placed to the underlying layer

• Good bonding is important during compaction and for long-term performance of the pavement

• “Must Have” for compaction process• A good tack coat prevents slippage during

compaction to “confine” the layer being constructed which helps to obtain density

• “Must Have” for long term performance• This bond is essential to obtain a long-life

pavement

• The consequences of a loss of bond is early pavement distress

• Early distress means shorter-than-desired service life

Why Is Tack Coat a “Must Have”?

• Layer independence•Slippage•Delamination•Reduced fatigue life• Increased rutting

•Compaction difficulty•Mat is not “confined”

Consequences of Poor Bonding

Direction of traffic?

Tack Coat Application

Biggest Challenge: Consistently getting uniform coverage

Conclusion

Right materials, Right handling & storage, Right application rate, Uniform coverage

are “Must Haves” for a Well Performing Pavement

Sections of the Synthesis

• Introduction

• Literature Review

• Survey Results

• Case Examples

• Conclusions

• Appendices

Sections of the Synthesis

• Introduction

• Literature Review

• Survey Results

• Case Examples

• Conclusions

• Appendices

What Exactly Is a Synthesis?

• A report that assembles and disseminates information on a topic of current highway practice.

• Tack Coat Synthesis:

• Authored by Asphalt Institute

• Develops along with technical panel

• Publication spring 2018

Survey - excellent response rate

41 Questions • Tack Coat Payment Specs

− 2 questions

• Tack Coat Materials− 4 questions

• Tack Coat Application− 28 questions

• Tack Coat Evaluation− 7 questions

7 Provinces

50 States

66%

34%

Individual Pay Item

Incidental to Paving

How is tack paid for?

Why is this important?Little incentive for sufficient tack application if not a direct pay item

Percentage of Materials Used

0.4%

79.4%

0.0%

20.2%

0%10%20%30%40%50%60%70%80%90%

100%

Top 5 Emulsions Used – State Survey

1.CSS-1h (52%)2.Non-standard* (48%)3.SS-1h (46%)4.SS-1 (36%)5.CSS-1 (28%)

* Non-standard means that a state has come up with its own nomenclature for an emulsion, outside those specified in AASHTO M 140 (Anionic Emulsions), M 208 (Cationic Emulsions), or M 316 (Polymer-Modified Cationic Emulsions)Examples: SS-1hp, CRS-2h, EBL

SCDOT Tack Materials

Tack Material % of Total

CRS-1; CRS 1h 30%

HFMS-1; HFMS-2 30%

CRS-2 30%

Generic Reduced Track 9%

PG 64-22 1%

Based on response NCHRP Tack Coat Synthesis and discussions with SCDOT

OGFC may require hot applied trackless tack to promote bondand reduce raveling (special provision)

Sections of the Synthesis

• Publication• Spring 2018

Panel Discussion

•Questions and Answers:

•Feel free to ask any question related to tack coat materials, application, etc.

•Focus on two important factors that suppliers are asked about a lot:•Handling and storage of emulsified asphalt• Proper storage and handling is important• Follow suppliers recommendations

•Sampling and testing of emulsified asphalt•Where should samples be taken?• Follow agency and suppliers recommendations

• Long-term storage.

•Vertical generally preferred.

•Heated.•Store toward lowest pumpable temperature

•Agitation.• Low-shear •Minimize frequency

•Hoses.•Keep clean

Storage Tanks

18

•Short-term storage.

•Generally not heated.

•Generally can not agitate.

Tanker Storage

19

•Short-term storage

•Heated

•Pump circulation

Distributor Storage

20

Questions?

What are average application rates?