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Tack Coat Specifications, Materials, and Construction Practices (2018)

Chapter: Appendix A - Survey Questions for U.S. and Canadian Agencies

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Page 85
Suggested Citation:"Appendix A - Survey Questions for U.S. and Canadian Agencies." National Academies of Sciences, Engineering, and Medicine. 2018. Tack Coat Specifications, Materials, and Construction Practices. Washington, DC: The National Academies Press. doi: 10.17226/25122.
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Suggested Citation:"Appendix A - Survey Questions for U.S. and Canadian Agencies." National Academies of Sciences, Engineering, and Medicine. 2018. Tack Coat Specifications, Materials, and Construction Practices. Washington, DC: The National Academies Press. doi: 10.17226/25122.
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Suggested Citation:"Appendix A - Survey Questions for U.S. and Canadian Agencies." National Academies of Sciences, Engineering, and Medicine. 2018. Tack Coat Specifications, Materials, and Construction Practices. Washington, DC: The National Academies Press. doi: 10.17226/25122.
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Page 88
Suggested Citation:"Appendix A - Survey Questions for U.S. and Canadian Agencies." National Academies of Sciences, Engineering, and Medicine. 2018. Tack Coat Specifications, Materials, and Construction Practices. Washington, DC: The National Academies Press. doi: 10.17226/25122.
×
Page 88
Page 89
Suggested Citation:"Appendix A - Survey Questions for U.S. and Canadian Agencies." National Academies of Sciences, Engineering, and Medicine. 2018. Tack Coat Specifications, Materials, and Construction Practices. Washington, DC: The National Academies Press. doi: 10.17226/25122.
×
Page 89
Page 90
Suggested Citation:"Appendix A - Survey Questions for U.S. and Canadian Agencies." National Academies of Sciences, Engineering, and Medicine. 2018. Tack Coat Specifications, Materials, and Construction Practices. Washington, DC: The National Academies Press. doi: 10.17226/25122.
×
Page 90
Page 91
Suggested Citation:"Appendix A - Survey Questions for U.S. and Canadian Agencies." National Academies of Sciences, Engineering, and Medicine. 2018. Tack Coat Specifications, Materials, and Construction Practices. Washington, DC: The National Academies Press. doi: 10.17226/25122.
×
Page 91
Page 92
Suggested Citation:"Appendix A - Survey Questions for U.S. and Canadian Agencies." National Academies of Sciences, Engineering, and Medicine. 2018. Tack Coat Specifications, Materials, and Construction Practices. Washington, DC: The National Academies Press. doi: 10.17226/25122.
×
Page 92

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88 Tack Coat Specifications, Materials, and Construction Practices 14. Does your agency specify when traffic is allowed on the applied tack coat surface? If so, when? _________ a. before the emulsion breaks (color change from brown to black) _________ b. after the emulsion breaks _________ c. after the emulsion has set (all the water has evaporated from the emulsion) _________ d. after a specific time delay (for example, 30 minutes)—please state the delay time _________ e. traffic not allowed on fresh tack between distributor and paver _________ f. does not specify 15. Does your agency specify when the paver is allowed to place asphalt on an emulsified tack coat? If so, when? _________ a. before the emulsion breaks (color change from brown to black) _________ b. after the emulsion breaks _________ c. after the emulsion has set (all the water has evaporated from the emulsion) _________ d. after a specific time delay (for example, 30 minutes)—please state the delay time _________ e. does not specify 16. What is the maximum time tack coat can be exposed before it must be covered by asphalt? _________ a. hours – Write in (Required) _________ b. days – Write in (Required) _________ c. no limit _________ d. other, please specify – Write in (Required) _________________________ 17. What is the maximum distance the tack coat can be applied in front of the paver? _________ a. enter distance in feet – Write in (Required) _________ b. no specification regarding maximum distance _________ c. other, please specify – Write in (Required) _________________________ 18. Which methods does your agency use to minimize/prevent pickup of tack coat materials? (Check all that apply.) _________ a. tack coat must break (color change from brown to black) before any type of traffic can be placed on the tack coat _________ b. tack coat must set (all the water has evaporated from the emulsion) before any type of traffic can be placed on the tack coat _________ c. requires the use of reduced-tracking tack materials _________ d. allows the use of reduced-tracking tack materials _________ e. requires the use of spray pavers _________ f. allows the use of spray pavers _________ g. sanding of tack coat materials after application _________ h. allows wetting/dampening of pavement before application of tack _________ i. other method, please specify – Write in (Required) ___________________ _________ j. tracking or pickup continues to be a problem 19. On average, what percentage of the pavement surface do you estimate is tacked on your projects, given that improper tacking (application was attempted on the entire pavement surface, but stripes or untacked areas resulted) will result in less than 100% coverage? _________ a. 100% coverage _________ b. 90+% coverage _________ c. 70%–90% coverage _________ d. 50%–70% coverage _________ e. < 50% coverage

Survey Questions for U.S. and Canadian Agencies 89 20. Do you require tack before every lift of overlay (100%—every lift has the underlying surface tacked)? If your agency sometimes waives a requirement for every lift to be tacked before- hand, what percentage of surfaces do you estimate are tacked prior to being overlaid with an asphalt mixture? _________ a. 100% (every lift has the underlying surface tacked) _________ b. > 75% _________ c. 25%–75% _________ d. < 25% 21. If your agency sometimes waives its typical requirement for tack coat, under what circum- stances would the requirement be waived? (Check all that apply.) _________ a. second lift on “fresh” material _________ b. asphalt pavement surface was milled prior to paving _________ c. PCC pavement surface was milled prior to paving _________ d. environmental conditions were deemed too poor _________ e. nighttime paving _________ f. other reason, please specify – Write in (Required) ___________________ _________ g. not applicable 22. If environmental conditions was one of your reasons above, please indicate which situations keep tack coat from being applied. _________ a. minimum ambient temperature (°F) – Write in (Required) ____________ _________ b. maximum ambient temperature (°F) – Write in (Required) ____________ _________ c. minimum pavement surface temperature (°F) – Write in (Required) ______ _________ d. maximum pavement surface temperature (°F) – Write in (Required) ______ _________ e. wet pavement surface _________ f. damp pavement surface _________ g. impending rainfall _________ h. time of year _________ i. other reason, please specify – Write in (Required) ___________________ _________ j. not applicable 23. How often do you require calibration of a tack coat distributor? _________ a. never _________ b. annually _________ c. monthly _________ d. per job _________ e. other, please specify – Write in (Required) _________________________ 24. If calibration of the distributor is required, what method is required? _________ a. ASTM D 2995a _________ b. ASTM D 2995b _________ c. agency standard, please specify – Write in (Required) ________________ _________ d. not applicable 25. If calibration is required, who performs the calibration? (Check all that apply.) _________ a. The agency _________ b. The contractor _________ c. Independent testing firm _________ d. Distributor manufacturer _________ e. Other – Write in ______________________ _________ f. Not applicable

90 Tack Coat Specifications, Materials, and Construction Practices 26. During construction, how is the tack coat application rate checked? (Check all that apply.) _________ a. ASTM D 2995a _________ b. ASTM D 2995b _________ c. mass applied calculation _________ d. volume applied calculation _________ e. agency standard, please specify – Write in (Required) ________________ _________ f. application rate is not checked 27. Which of the following are specified by your agency for spray application of tack coat materials? (Check all that apply.) _________ a. spray without overlap of emulsion streams on the application _________ b. spray with double overlap of emulsion streams on the application _________ c. spray with triple overlap of emulsion streams on the application _________ d. minimum height (inches) of the spray bar – Write in (Required) ________ _________ e. maximum height (inches) of the spray bar – Write in (Required) ________ _________ f. minimum angle (degrees) nozzle angle relative to the spray bar – Write in (Required) __________________________ _________ g. maximum angle (degrees) nozzle angle relative to the spray bar – Write in (Required) __________________________ _________ h. clean nozzles _________ i. uniform nozzles _________ j. Other – Write in ______________________ _________ k. none 28. If the tack coat is not uniform, what steps are employed to correct the problem? (Check all that apply.) _________ a. make the contractor reapply tack coat at the same rate _________ b. make the contractor reapply tack coat at a reduced rate _________ c. penalize the contractor, please describe – Write in ___________________ _________ d. require the contractor to do better on subsequent applications, but do not require a reapplication of tack or enforce any penalty on the current application _________ e. require the contractor to clean nozzles _________ f. do nothing _________ g. other steps not offered here, please describe – Write in (Required) ________ 29. Do any of the following conditions cause the specified residual asphalt tack coat application rate to change? (Check all that apply.) _________ a. time of year _________ b. time of day (day vs. night) _________ c. type of roadway _________ d. pavement surface condition _________ e. ambient temperatures _________ f. overlay thickness _________ g. other, please specify – Write in (Required) _________________________ _________ h. no 30. Do your specifications and/or plan notes clearly state to apply the tack coat some distance beyond the planned mat width (to help confine the longitudinal joint)? _________ a. yes _________ b. no 31. Does your agency allow the use of spray pavers? (If no, proceed to question 36.) _________ a. yes _________ b. no

Survey Questions for U.S. and Canadian Agencies 91 32. If so, on what percentage of your agency’s projects do you estimate they are used? _________ a. 81%–100% _________ b. 61%–80 % _________ c. 41%–60% _________ d. 21%–40% _________ e. 0%–20% 33. Does your agency require a different type of tack coat to be used with spray pavers than on projects without spray pavers? _________ a. yes _________ b. no 34. If so, what tack material(s) is specified for use with spray pavers? Material – Write in (Required) ________________________________ Material – Write in (Required) ________________________________ Material – Write in (Required) ________________________________ Material – Write in (Required) ________________________________ Material – Write in (Required) ________________________________ 35. Does your agency require any specific methodology to ensure that the tack coat applied by spray pavers is uniform and at the proper application rate? _________ a. yes: please describe the methodology (required) ______________________ _________ b. no Tack Coat Application Evaluation 36. Does your agency perform interface bond strength testing? (If no, proceed to question 42.) _________ a. yes _________ b. no 37. When does your agency perform interface bond strength testing? (Check all that apply.) _________ a. routinely on every asphalt project for quality assurance/acceptance _________ b. by special provision _________ c. for product evaluation _________ d. as part of forensic investigations _________ e. other – please elaborate (required) _______________________________ 38. What type/style of interface bond strength testing does your agency perform? (Please indi- cate test specification destination as applicable.) _________ a. lab shear testing – (name of test/standard designation and pass/fail criteria) (Required) _____________________________ _________ b. field shear testing – (name of test/standard designation and pass/fail criteria) (Required) _____________________________ _________ c. lab torsion testing – (name of test/standard designation and pass/fail criteria) (Required) _____________________________ _________ d. field torsion testing – (name of test/standard designation and pass/fail criteria) (Required) _____________________________ _________ e. lab tension testing – (name of test/standard designation and pass/fail criteria) (Required) _____________________________ _________ f. field tension testing – (name of test/standard designation and pass/fail criteria) (Required) _____________________________ _________ g. other testing – (name of test/standard designation and pass/fail criteria) (Required) _____________________________

92 Tack Coat Specifications, Materials, and Construction Practices 39. Is the stress applied: _________ a. in a creep load (constant; neither increasing nor decreasing) to failure – please indicate the magnitude of any normal load (psi) ____________________ _________ b. in a monotonically increasing stress or displacement rate to failure (constant rate of loading to failure) – please state rate to failure (in./min, mm/min, etc.) ____________________ _________ c. cyclical: please describe the cycle _________________________________ _________ d. other, please describe – Write in __________________________________ 40. If a normal load is applied, is it required or optional? _________ a. required _________ b. optional _________ c. not allowed 41. What minimum bond strength value do you require for your agency’s test method(s)? State test method and minimum bond strength required, including units. ________________________________________________________________________ 42. Does your agency require any tests, either in the lab or in the field, to evaluate tack coat materials in lieu of or in addition to bond strength? _________ a. yes, please specify (Required) ____________________________________ _________ b. no 43. For what types of pavement failures do you consider tack coat as a potential cause? _________ a. Slippage of the surface layer _________ b. Delamination of pavement layer _________ c. Fatigue cracking _________ d. Top-down cracking _________ e. Rutting of the pavement _________ f. Other distress(es), please describe (Required) _______________________ 44. Does your agency have any completed, ongoing, or planned research on tack coat materials or performance? Please describe or provide links to the projects or their reports. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ 45. Do you have additional comments regarding any aspect of tack coats you would like to include? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

93 Tack Coat Payment Specifications 2. How is tack coat paid for on your contracts? 66% (33/50) – individual pay item 34% (17/50) – incidental to paving 3. If it is paid as an individual item, how is it measured? (Check all that apply.) (8 of the 33 states pay by two measures, so percentages add up to > 100% 3% (1/33) – volume of residual asphalt 3% (1/33) – mass of residual asphalt 58% (19/33) – volume of undiluted emulsion 36% (12/33) – mass of undiluted emulsion 12% (4/33) – volume of diluted emulsion 6% (2/33) – mass of diluted emulsion 6% (2/33) – other – write in (required): square yards Tack Coat Materials 4. Which types and grades of asphalt materials are commonly used for tack coat on your agency’s paving projects AND what percentage of your agency’s total tack coats do you estimate use the material? Use as many spaces as you need. Material types include results for agencies that only provided material type, percentages are based on the total of all materials (binders, emulsions, reduced-tracking) with agency-reported estimated percentages, and include weighted results for only those agencies that provided both material type and percentage used. PG Binders Emulsified Asphalts Cutback Asphalts Reduced-Tracking Materials PG 58-22: 0.0% Non-standard: 9.5% RC-70: NR* AE-NT: 2.1% PG 58-28: NR* CQS-1h: 2.1% CBC-1H: 0.1% PG 64-22: 0.2% CRS-1: 1.6% CBC-1HT: 0.4% PG 64-28: 0.0% CRS-2: 1.2% Cleanbond: NR* PG 67-22: NR* CRS-2p: 0.1% CNTTC: NR* CSS-1: 8.4% CRS-1h: NR* CSS-1h: 18.4% EM-50-TT: 0.2% HFMS-1: NR* NTCQS-1HM: NR* HFMS-2h: NR* NTCRS-1HM: 0.4% A P P E N D I X B Summary of Survey Results (U.S.) (continued on next page)

94 Tack Coat Specifications, Materials, and Construction Practices PG Binders Emulsified Asphalts Cutback Asphalts Reduced-Tracking Materials MS-2: NR* NTCRS-1HSP: NR* RS-1: 13.4% NTHAP: NR* SS-1: 5.8% NTQS-1HH: 1.0% SS-1h: 17.5% NTSS: 0.4% NTSS-1HM: 5.3% PATT: 0.2% PennDOT NT: NR* RS-1h: 11.1% Ultrafuse: 0.5% * NR signifies that at least one agency reported using the material but did not report a percentage used. 5. Check all that apply if your agency specifies a specific tack coat material for nighttime paving: a. PG Binders: Florida, South Carolina only b. Reduced-tracking material: Delaware, Florida, South Carolina only c. Other – Write in (Required): standard emulsions – South Carolina only 6. Does your agency specify different application rates for different surface types? Please supply the target or target range of the RESIDUAL ASPHALT application rates for each surface type. The table below represents the consultants’ best efforts to compile the responses. Surface Type Tacked Residual Asphalt Application Rate (gal/sy) Average Low Average High Average Target New Asphalt 0.027 0.043 0.035 Existing (Old) Asphalt 0.034 0.051 0.043 Milled Asphalt 0.041 0.058 0.049 New or Existing PCC 0.042 0.062 0.052 Milled or Diamond Ground PCC 0.047 0.057 0.067 Comments Five agencies do not specify different rates for different surface types. 18 respondents have a single rate or a single range of rates for all surface types. Six respondents have value or range for New Asphalt, and a single rate or a single range of rates for all other surface types. One agency lumped all asphalt and all PCC into single values (0.03 for AC and 0.12 gsy for PCC). Four states specify application rates for milled surfaces in general, but do not have separate requirements for milled asphalt surfaces vs. milled PCC surfaces. Six states differentiate between new or old asphalt and PCC, but do not consider whether or not the surfaces are milled. Seven states treat new asphalt differently than old asphalt and PCC is a different rate too. The remaining four have some combination as follows: —New asphalt has two different singular application rates (0.03 or 0.05 gsy) dependent on if the second lift is the same day as the previous lift or not. Then for old asphalt, 0.05 to 0.08 gsy, and 0.07 to 0.08 for milled asphalt and all PCC surfaces. —Singular values for new asphalt, old asphalt, milled asphalt, or milled PCC, but a range for any other PCC surfaces. —Singular values for new or old asphalt, for milled asphalt, and all PCC milled or not. —New asphalt, old asphalt, and milled asphalt each have unique singular values. PCC surfaces all get a range of values, which is the same whether milled or not. 15 agencies call for single values, 28 use ranges, and three use single values for some surfaces but a range for others. The other five are those that did not say.

Summary of Survey Results (U.S.) 95 7. Who decides what the tack coat type and application rate will be? 62% (31/50) a. agency or agency representative 16% (8/50) b. contractor 0% (0/50) c. supplier 22% (11/50) d. other, please specify: Mostly contractor selects material, agency selects rate Tack Coat Application 8. What is required by your agency’s specifications for cleaning the pavement? 42% (21/50) a. Power brooming or street sweeper 0% (0/50) b. Air blowing or vacuum sweeper 28% (14/50) c. Both A and B 34% (17/50) d. Other – Write in (Required): Mostly required clean, but did not specify method 1% (2/50) e. Nothing 9. (Check all that apply.) Do your agency’s specifications and/or plan notes clearly state whether the application rate is for: 15% (7/48) a. residual asphalt 38% (18/48) b. undiluted emulsion 17% (8/48) c. diluted emulsion 17% (8/48) d. does not specifically state? 15% (7/48) multiple answers by same agency 10. Is dilution of an emulsified tack coat allowed? 48% (24/50) a. yes 52% (26/50) b. no 11. If dilution is allowed, where is it allowed? (Check all that apply.) 88% (21/24) a. at the asphalt supplier’s terminal? 33% (8/24) b. at the contractor’s storage tank? 46% (11/24) c. in the contractor’s distributor? 0% (0/24) d. in another location? (please specify) – Unspecified by respondents 12. How is the dilution rate of an asphalt emulsion verified? (Check all that apply.) 46% (11/24) a. certification by the asphalt supplier 8% (2/24) b. certification by the contractor 29% (7/24) c. sample taken and tested from the contractor’s storage tank 46% (11/24) d. sample taken and tested from the distributor 8% (2/24) e. visual observation during the dilution process 33% (8/24) f. dilution rate is not verified 0% (0/24) g. other method, please specify – Write in (Required) ________________ 13. How often is the dilution rate verified? 8% (2/24) a. daily 0% (0/24) b. monthly 50% (12/24) c. by project 21% (5/24) d. never 21% (5/24) e. other, please specify – summary below: Three verify once per some volume, 10,000, 25,000, or 50,000 gallons, respectively. One said 1/tank of material. One said 1/100 tons. Two accept a certification from the supplier on a project basis. One said 1/lot but did not state what a lot constitutes. One said it varies.

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TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 516: Tack Coat Specifications, Materials, and Construction Practices provides state agencies across the United States with guidance as they reevaluate their tack coat specifications, the materials they use, and the practices by which the tack coats are placed. Pavement thickness design assumes that pavement works together as one layer, rather than a stack of individual layers working independently. Tack coats function as bonding agents between each lift of a pavement section to create the desired monolithic pavement structure. A tack coat is a sprayed application of asphalt material upon an existing asphalt or Portland cement concrete (PCC) pavement prior to an overlay, or between layers of new asphalt concrete.

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