Thin Asphalt Concrete Overlays (2014)

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29 appendix a Survey Questionnaire 1. What is your agency’s definition of “thin” asphalt concrete overlay? Check all that apply. May be greater than 1.5 inches 1 inch to 1.5 inches 0.75 to 1.5 inches Less than 1 inch Less than 0.75 inches Other (please specify): 2. What investigation is done to determine when to use thin asphalt concrete overlays ? (If you check more than one item, please provide a comment indicating where the different criteria are used.) No investigation is done Cores are taken to determine what rehab may be needed A structural analysis is done to determine adequate structure is provided The surface is typically milled to remove top-down cracking Other (Please specify): 3. Where are thin overlays used? Interstate Primary & secondary routes

30 Local routes Low traffic volume routes Only for certain types of pavement distress (please specify): 4. How does your agency determine what mix type will be used [based on Nominal Maximum Aggregate Size (NMAS)] for thin overlay applications? (If you check more than one item, please provide a comment indicating what criteria are used.) Based on traffic volume or functional classification Based on thickness/NMAS ratio of 2:1 Based on thickness/NMAS ratio of 3:1 Based on economic conditions/budget constraints Other (please specify): 5. Is this mix typically used even when there are sufficient funds to place a thicker layer? Yes No 6. Under what pavement conditions would you NOT use thin asphalt concrete overlays? (Describe severity level at which thin overlays would not be used.) No restrictions Roughness/poor ride

31 Loss of surface texture/low friction Raveling Rutting Cracking (fatigue, block, or thermal) 7. What requirements are used for aggregates used in thin asphalt concrete overlays? (Attach specification if you prefer.) Superpave Criteria (AASHTO M323) SMA Criteria (AASHTO M325) Agency specific Other (please specify): 8. Is the same asphalt binder grade used for thin asphalt overlays as would be used on the same project for thicker overlays? Yes No 9. Are modified asphalt binders used? If so, under what conditions? Modified binders are not used Based on classification/function (Interstate, primary route, etc.)

32 Based on traffic volume or ESAL; specify criteria Based on condition of existing pavement Other (please specify): 10. Are Recycled Asphalt Pavement (RAP) and/or Reclaimed Asphalt Shingles (RAS) allowed in thin asphalt concrete overlays? If so, what amounts (or under what conditions) may RAP and RAS be used? RAP/RAS not allowed in thin overlays RAP limited to 15% in thin overlays RAP limited to 25% in thin overlays RAP limited to 50% in thin overlays RAS limited to 5% in thin overlays RAS limited to <10% in thin overlays RAP/RAS limited based on recovered binder properties Other (please specify): 11. If RAP/RAS are used, how is the amount of binder contribution determined? Solvent extraction Ignition oven Based on a percentage of the recovered binder Back-calculated using the Gmm value Other (please specify):

33 12. What mix design method is used? Superpave (AASHTO R 35/T 312) SMA (AASHTO R46) Marshall (AASHTO T245) Hveem (AASHTO T 246) California Kneading Compactor (AASHTO T 247) Other (please specify): 13. What air void level, or range of air void levels, is used to determine optimum asphalt content? <3.5% 3.5–4.5% 4% 4%–5% 4%–6% Other (please specify): 14. What laboratory performance tests are typically required? (If different from AASHTO, please provide a copy.) Moisture Susceptibility (AASHTO T 283) Rutting Susceptibility (AASHTO T 340—Asphalt Pavement Analyzer) Rutting Susceptibility (AASHTO T 324—Hamburg)

34 Flow Number (AASHTO TP 79) Dynamic Modulus (AASHTO TP 79) Other (please specify): 15. Are there restrictions on placing thin layers during cold weather? If the restrictions are different for “hot” and “warm” mix, explain. No restrictions Must be above freezing >45 degrees F >55 degrees F Other (please specify): 16. What tack application rates (based on residual) are used for thin lifts? 0.02–0.06 gal/sq yd 0.02–0.08 gal/sq yd 0.04–0.08 gal/sq yd Other (please specify): 17. Is there a minimum thickness based on NMAS? 1.5 × NMAS 2 × NMAS

35 3 × NMAS 4 × NMAS 18. How is density specified? % of control strip % of laboratory density % of theoretical Density not measured—compact to satisfaction of engineer Density not measured—type rollers and number of passes specified 19. What mixture/pavement properties are used for acceptance? Asphalt content Gradation Plant lab air voids Roadway density Smoothness Spread rate Other (please specify): 20. Approximately how many tons of thin overlay mixes do you place each year? Less than 100,000 100,000–500,000

36 500,000–less than 1 million >1 million 21. If special procedures are used to maintain surface condition (texturing, grinding, fog seal, etc.), how is it determined when those activities should be applied? No special activities are used Based on type and level of distress Based on condition rating Based on smoothness Automatically scheduled at periodic intervals Other (please specify): 22. How is the optimal application rate for fog seals or rejuvenating agents determined? No fog seals or rejuvenators are used Agency standard rate is used Based on type and level of distress Other (please specify): 23. What is the actual service life of thin asphalt concrete overlays? <5 years 5–8 years 8–10 years

37 10–12 years >12 years 24. If there is a large range in service life (more than one answer checked in previous question), is there an explanation for the large range? Condition of existing surface at time of overlay Amount of surface preparation Large fluctuations in traffic volume from project to project Variation in construction quality Other (please specify): 25. How is pavement service life monitored/verified? Manual condition surveys Video records of condition Deterioration curves based on condition/serviceability are updated annually Threshold values are used to determine when action is needed Other (please specify): 26. Are annualized cost comparisons per mile available for thin asphalt overlays versus other pavement maintenance/preservation treatments? Yes. (If so, please provide the basis for those comparisons.) No

38 27. Are warranties required for thin asphalt concrete overlays? Yes. (If so, attach specification.) No 28. Do you have example projects of thin asphalt overlays that have far exceeded expectations? Yes No Comments/Explanation: 29. Do you have example projects of thin asphalt overlays that have significantly failed to meet expectations? Yes No Comments/Explanation: 30. List any suggestions/recommendations for “successful practices” you have observed during project selection, mix design, construction, and maintenance/preservation that have been helpful in extending the service life or overall performance of thin asphalt overlays.