Panel Discussion: Tack Coat - Storage and Handling - Sampling and Testing 2018 SCAPA Winter Conference Timothy Owings Associated Asphalt James Ross Blacklidge Emulsions Bob Horan, PE Asphalt Institute
Our Visit Today 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
Tack Coat Workshops 2015-2016 2700 attendees in 47 workshops; 3100 in 35 presentations SCDOT Tack Coat Workshop November 2015
Why Is Tack Coat a Must Have? 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
Consequences of Poor Bonding Layer independence Slippage Delamination Reduced fatigue life Increased rutting Compaction difficulty Mat is not confined 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
How is tack paid for? 34% 66% Individual Pay Item Incidental to Paving Why is this important? Little incentive for sufficient tack application if not a direct pay item
Percentage of Materials Used 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 0.4% 79.4% 0.0% 20.2%
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 Based on response NCHRP Tack Coat Synthesis and discussions with SCDOT 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% OGFC may require hot applied trackless tack to promote bond and 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
Storage Tanks Long-term storage. Vertical generally preferred. Heated. Store toward lowest pumpable temperature Agitation. Low-shear Minimize frequency Hoses. Keep clean 18
Tanker Storage Short-term storage. Generally not heated. Generally can not agitate. 19
Distributor Storage Short-term storage Heated Pump circulation 20
Questions?
What are average application rates?