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60 A P P E N D I X A State Survey Questionnaire Synthesis 49-05 Impact of Asphalt Lift Thickness The Transportation Research Board is preparing a synthesis on the Impact of Asphalt Materials Lift Thickness on Pavement Quality. This survey is part of the information gathering on that topic. Your cooperation in completing this survey will be greatly appreciated. There are 16 main questions in the survey, most of which only require clicking on the appropriate response(s). Some answers will lead to follow-up questions for clarification or additional information. We estimate the survey will take 15-20 minutes or less to complete. Click on >> to move forward and << to move backwards through the survey. In this survey, NMAS means nominal maximum aggregate size (one sieve size larger than the first sieve to retain more than 10%) and PCS means primary control sieve (from Table 5) as defined in AASHTO M 323. Please complete this questionnaire by March 16, 2018. If you prefer, you may respond to these questions using the PDF attached to the email invitation; this can be returned to Rebecca McDaniel, the consultant for this project, by email at firstname.lastname@example.org. If you have any questions about the survey, you may contact Dr. McDaniel by email or by phone at 765/463-2317 ext 226. Thank you! Please provide your contact information so that we know who has completed the survey. Name Position/Title Agency Address City State Email Address Phone Number May we please contact you for more information or clarification? o Yes o No o Please contact this person instead (name, phone and email).
State Survey Questionnaire 61 1. Does your organization have established policies or guidelines regarding appropriate asphalt lift thicknesses relative to the nominal maximum aggregate size (NMAS) of the mixture? o Yes o No o Unsure If yes, how are these policies or guidelines enacted? (Please click all that apply.) o Pavement Design Manual o Design Memo o Specifications o Other (Please specify) Please provide a link to the guidance document (or send copy to email@example.com). 2. What are the minimum lift thicknesses specified (or typically used if not specified) for different types and sizes of mixtures by your agency? You may use whatever unit is most convenient â inch, mm, number Ã NMAS (example 4ÃNMAS). Please insert âNoneâ for mix sizes or types that you do not use (blank cells suggest unanswered questions). N/A may be used to indicate mixes that you do use but which do not have minimum lift thicknesses. If you do not differentiate between fine and coarse dense-graded mixtures, please record the minimum lift thicknesses in the fine column and insert âSameâ in column for coarse mixtures. You may do the same for SMA or open-graded mixes. (You will have a chance later to indicate what types of mixtures are most commonly used.) Fine Dense Graded Coarse Dense Graded Stone Matrix Asphalt (SMA) Open-Graded 4.75-mm NMAS Mixture 9.5-mm NMAS Mixture 12.5-mm NMAS Mixture 19.0-mm NMAS Mixture 25.0-mm NMAS Mixture 37.5-mm NMAS Mixture
62 Impact of Asphalt Thickness on Pavement Quality 3. Do you specify different maximum lift thicknesses depending on mixture size and/or type? o Yes o No, do not specify a maximum or have one maximum regardless of mixture size (please specify maximum value). If yes, what are the maximum allowable lift thicknesses? You may use whatever unit is most convenientâinch, mm, number Ã NMAS (example 4ÃNMAS). Fine Dense Graded Coarse Dense Graded Stone Matrix Asphalt (SMA) Open-Graded 4.75-mm NMAS Mixture 9.5-mm NMAS Mixture 12.5-mm NMAS Mixture 19.0-mm NMAS Mixture 25.0-mm NMAS Mixture 37.5-mm NMAS Mixture 4. Are there situations in which your agency may grant exceptions to these allowable lift thicknesses? o Yes o Maybe o No If yes or maybe, when and why would you consider making exceptions? 5. What are your agencyâs target density requirements for dense-graded mixtures? o Please provide a link to your specifications or click the appropriate button below. (For PWL specs, please indicate minimum density required for 100% pay.) o <92% of mix theoretical maximum specific gravity (Gmm) o 92% of mix maximum theoretical specific gravity (Gmm) o 93% of mix maximum theoretical specific gravity (Gmm) o >93% of mix maximum theoretical specific gravity (Gmm) o Other (please specify) 6. Are target densities the same if compaction is limited to static mode? o Yes o No (Please specify)
State Survey Questionnaire 63 8. Have you observed paving contractors having more difficulty in obtaining required field densities since implementing the Superpave mix design system? o Yes, initially but less so now o Yes, continuing to be difficult o Yes, with certain mixes or applications o No o Unsure o Have not implemented Superpave If you selected Yes, initially but less so now: If the situation has improved, what changed? (Please click all that apply.) o Lift thicknesses have been increased o Density requirements have been revised after implementing Superpave o Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS) o Mix design parameters (gyration level, minimum binder content, etc.) have been revised o Smaller NMAS mixtures are used in certain lifts (ex., 9.5 mm instead of 12.5 mm) o Other (please specify) If unsure, are there other current or previous members of your organization who may know? (Please provide contact information.) When your state implemented Superpave, did you keep the same density requirements or did you change the density requirements for Superpave mixtures? o Kept same density requirements o Changed density requirements when Superpave was implemented o Have not implemented Superpave 7. How is pavement density measured by your agency? (Please click all that apply.) o Nuclear density gauge o Non-nuclear density gauge o Cores o Other If you use cores, how does your agency determine the bulk specific gravity (Gmb) of cores? o AASHTO T 166, Standard Method of Test for Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-Dry Specimens o AASHTO T 275, Standard Method of Test for Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Paraffin-Coated Specimens o AASHTO T 331, ASTM D6752, Standard Method of Test for Bulk Specific Gravity (Gmb) and Density of Compacted Hot Mix Asphalt (HMA) Using Automatic Vacuum Sealing Method o State test method (please specify) o Other (please specify)
64 Impact of Asphalt Thickness on Pavement Quality 9. Has your agency changed recommended or required lift thicknesses since implementing the Superpave mix design system? o Yes o No o Unsure o Have not implemented Superpave If yes, what was the reason for the change? (Please click all that apply.) o Observed difficulties with achieving required field density o Increased pavement permeability o Other observed pavement performance problems (please specify) o Other statesâ issues and recommendations o Recommendations from research (such as NCHRP Report 531 or other) o Other (please specify) 10. Does your agency use these tests or technologies for asphalt materials/placement? Yes, routinely Yes, experimentally or occasionally No Workability o o o Permeability o o o Mat temperature variation (i.e., thermal segregation) o o o Intelligent compaction o o o Other factor related to density o o o If yes, what test method(s) or parameters do you evaluate? o Workability o Permeability o Mat temperature variation o Intelligent compaction o Other factor related to density
State Survey Questionnaire 65 11. Have you observed contractors having increased difficulty obtaining adequate density in mixtures with certain components or in certain applications? (Please click all that apply.) o Reclaimed asphalt pavements (RAP) o Recycled asphalt shingles (RAS) o Polymer-modified binders o Ground tire rubber (GTR) o Certain binder grades (please specify grades) o Highly angular aggregates o Certain aggregate types (please specify) o Thin lifts o At low base or mix temperatures o When placing asphalt over concrete o Other (please specify) If yes, have you adopted any strategies to address these issues? 12. Does your agency allow the use of warm mix asphalt technologies at conventional temperatures as a compaction aid? o Yes o No o Permissive spec or not monitored If yes, does the use of WMA as a compaction aid seem to improve the ability to get density? o Always o Frequently o Sometimes o Never 13. Have you observed any asphalt pavement performance problems that are perceived to be related in whole or in part to inadequate compaction during construction? (Please click all that apply.) o Postconstruction densification (rutting) o Increased cracking o Increased permeability o Decreased durability o Shortened pavement service life o Need for increased maintenance o Other (please specify) 14. Has your state conducted or sponsored any research related to asphalt pavement density and lift thickness (currently or in the past)? o Yes (please add reference, contact, or link) o Planning or considering the need o No o Unsure
66 Impact of Asphalt Thickness on Pavement Quality 15. Do you see a need for additional research into any of the following? (Please click all that apply.) o Field validation of recommended ratios of lift thickness to NMAS o Means of improving mix compactibility o Means of achieving adequate mat density o Improved test methods or technologies to ensure adequate compaction o Effects of mixture properties on compactibility o Other (please specify) 16. If you have any additional thoughts or information on your organizationâs experience with the effects of asphalt lift thickness on pavement performance, please describe briefly here or indicate if you are willing to be contacted for further information. This completes the survey. Thank you for your time and information. Survey results will be summarized and shared with all respondents.