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?