Thin Asphalt Concrete Overlays (2014)

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40 appendix c Survey Responses Response of agencies is listed by their postal abbreviation. Private industry responses are listed as follows: EB = E & B Paving GC = Granite Construction HE = Heritage Research OC = Old Castle PC = Paving Contractor PRC = Prairie Construction SS = Silver Star Constr. WG = Wiregrass Construction 1. What is your agency’s definition of “thin” asphalt concrete overlay? Check all that apply. May be greater than 1.5 inches AK, IL, MT, ND, NM, OH, UT 1 inch to 1.5 inches CA, ID, KY, MN, MO, ND, NE, NH, NV, OR, RI, VT, WI, GC, OC 0.75 to 1.5 inches CO, ID, IL, IN, LA, MA, MD, NJ, PA, RI, TX, VT, OC, HE, PRC, SS Less than 1 inch AL, AZ, DE, GA, ID, ME, MS, NC, OK, SC, TN, VA, VT, WA, WV, HE, OC, PC Less than 0.75 inches AR (UTBWC), KS, MD, MN, TN, VT Other (please specify): AK—2” min.; FL—Not defined; GA—1.0–1.5” is normal, not thin; KY—1.25–1.5”; MN— HMA = 1.5”, UTBWC = <0.75”; MT—1.8–2.4”; OH—<2”; PA—0.75–1.25; UT—<2”; WI—<1.5” 2. What investigation is done to determine when to use thin asphalt concrete overlays? No investigation is done ID, IL, KS, ND, NH, OH, OK, PA, TN, WV, PRC Cores are taken to determine what rehab may be needed AL, AZ, CA, FL, GA, IN, MA, MD, MO, MS, NE, NJ, NM, NV, RI, UT A structural analysis is done to determine adequate structure is provided AL, AK, CA, CO, GA, MA, MD, MS, NE, NM, NV, TX, GC The surface is typically milled to remove top-down cracking AL, FL, GA, IL, KY, LA, MA, MN, NE, NV, OH, OK, PA, RI, SC, HE, OC, SS Other (Please specify): DE—Visual; GA—Roads visually rated each year; KY—Pavement Management System generates list of candidates; OH—Use decision tree; VA—Visual survey and maintenance history 3. Where are thin overlays used? Interstate AK, AZ, GA, ID, IL, KS, KY, LA, MA, MN, MT, NH, NJ, NM, OH, OK, TX, VA, VT, GC, OC, PRC Primary & secondary routes AK, AZ, DE, FL, GA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MN, MO, MS, MT, NC, ND, NE, NH, NM, OH, OK, PA, RI, TN, TX, UT, VA, WV, EB, GC, HE, OC, PC, SS Local routes AL, CA, GA, ID, IL, IN, KY, LA, MD, ME, MN, MS, MT, NC, NE, NH, NM, NV, RI, SC, TX, UT, VA, HE, OC Low traffic volume routes AL, CA, CO, DE, GA, ID, IL, IN, LA, MD, ME, MN, MS, MT, NC, ND, NE, NH, NV, OH, RI, SC, TN, TX, UT, VT, WA, PC, SS Only for certain types of pavement distress (please specify): PA—Low to moderate raveling; NJ—Used for minimal distress, 7–10 years old Comments GA—1.25–1.5” has been standard overlay for years; IL—2” mill & fill & UTBWC used on interstates; IN—Discontinued use on interstates due to low friction/macrotexture; OR—Only being used experimentally 4. How does your agency determine what mix type will be used (based on Nominal Maximum Aggregate Size (NMAS) for thin overlay applications? Based on traffic volume or functional classification AL, AK, CA, GA, LA, MA, MO, MS, NC, OH, TN, WV Based on thickness/NMAS ratio of 2:1 ID, ME, NV Based on thickness/NMAS ratio of 3:1 CO, DE, IL, KY, MA, MD, MO, MS, NE, NH, NJ, NM, OK, OR, SC, UT, VA,WA, WI, GC, PC, SS Based on economic conditions/budget constraints CA, IN, MA, MS, NC, ND, NJ, RI, TX, VT, OC

41 Other (please specify): AR—Use UTBWC; AZ—≤1” use rubberized OGFC; FL—Use 3 × NMAS for dense-graded & 1.5 × NMAS for OGFC; IL—UTBWC does not follow NMAS ratio; KS—Use UTBWC; LA—12.5 mm used for OGFC and coarse graded > 700 ADT; MA—Function of many factors—OGFC for limited access, 9.5 at 1.25” thick for low volume, 1.25” gap graded rubber mix for high volume; MO—Traffic & function determine treatment type, but thickness based on NMAS; MT—0.75” used for most overlays; PA—9.5 mm mix for 1.0–1.5” thickness, 6.3 mm experimented with for 0.75–1.25”; WI—12.5 mm NMAS is smallest size used; GC—minimum of 3:1 NMAS ratio 5. Is this mix typically used even when there are sufficient funds to place a thicker layer? Yes AK, AR, CA, DE, FL, GA, IN, KS, KY, LA, MA, MS, MT, ND, NE, NH, NJ, OH, OK, RI, SC, TN, VT, WV, HE, OC, PC, PRC No CO, ID, IL, MD, ME, MN, MO, NC, NV, OR, PA, UT, WA, GC, SS 6. Under what pavement conditions would you NOT use thin asphalt concrete overlays? No restrictions DE, GA, KY, ND, NE, RI, TX, VT, PC Roughness/poor ride AK, KS, RI, WA, WV Loss of surface texture/low friction NC Raveling AZ, MA, NC, PA, RI, SC, TN, UT, VA, WA, WI, GC Rutting AZ, CA, ID, IL, IN, KS, MA, ME, MS, NC, NM, NV, PA, RI, SC, TN, VA, WA, HE, OC, PRC Cracking (fatigue, block, thermal) AL, AK, CA, CO, ID, MA, MD, ME, MO, MS, MT, NC, NH, NJ, NM, NV, OH, OK, OR, PA, RI, SC, TN, UT, VA, WA, WI, EB, GC, HE, OC, PRC, SS (Comment: FL does not place an overlay without milling to remove distresses.) 7. What requirements are used for aggregates used in thin asphalt concrete overlays? Superpave Criteria (AASHTO M323) AL, AR, CO, DE, FL, GA, ID, KY, MA, MD, ME, MN, MO, MS, MT, NC, ND, NE, NH, NM, OR, PA, VT, WA, WV, EB, HE, OC, PRC, WG SMA Criteria (AASHTO M325) GA, LA Agency specific AK, AZ, CA, GA, IL, IN, KY, LA, MD, MN, NJ, NV, OH, RI, SC, TN, UT, VT, GC, PC, SS Other IL—Aggregate requirements based on polish resistance; KS—Superpave specs for 4.74-mm mix, agency specific for UTBWC; LA—Micro Deval of 18 8. Is the same asphalt binder grade used for thin asphalt overlays as would be used on the same project for thicker overlays? Yes (All agencies/private industry except for the “No” agencies/industry below) No KS, NJ, RI, TX, PRC 9. Are modified asphalt binders used? If so, under what conditions? Modified binders are not used AL, IN, MD, ME, NC, WG Based on classification/function (Interstate, primary route, etc.) AZ, CO, DE, GA, KY, MA, MO, MT, RI, TN, HE, OC, SS Based on traffic volume or ESAL; specify criteria CA, DE, FL, GA, ID, IL, KY, MO, MS, MT, ND, NE, OR, SC, TN, VT, OC, PC, PRC Based on condition of existing pavement MA, RI, TN, VT Other (please specify): AR—For UTBWC; CA—Climate; FL—Also used in areas with history of rutting problems; ID—Based on LTPPBind program for ESAL & climate; KY—All interstates and routes > 30 million ESALs; LA—all surface mixes; MT—All roads > 50 daily ESALs; NH—Application specific (ramps, intersections, high traffic vol- ume); NJ—Always required for thin overlays; NV—Based on climate, location; OR—High traffic volume > 10 million ESALs; PA—Same as for thicker layers; RI—All thin overlays; TX—Use modified asphalt for optimum performance; UT—All thin overlays; WA—Based on climate zone; WV—All thin overlays 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 AK, AZ, LA, NJ, OK, PA, RI, TX, PRC, SS RAP limited to 15% in thin overlays CA, MA, MT, NV, OH, TN, WV

42 RAP limited to 25% in thin overlays AL ≤ 20%, DE, FL ≤ 20%, KY, MS, ND ≤ 20%, NE, OH, OR, SC, UT, VT, WA ≤ 20%, HE, OC, PC RAP limited to 50% in thin overlays GA ≤ 40%, NC, NM ≤ 35% RAS limited to 5% in thin overlays AL, GA, KY, OH, PA, SC, HE, OC, PC RAS limited to < 10% in thin overlays (No responses) RAP/RAS limited based on recovered binder properties CO, MD, NC, NH, PA, WA Other (please specify): ID—No RAS: RAP not limited except for aggregate angularity; IN—RAS ≤ 25% binder replacement: RAP ≤ 40% binder replacement; MA—≤10% for gap graded rubber mixes; ME—Up to 30% based on RAP properties; MN—Based on binder replacement; MS—No RAP in 4.75-mm mix; NH—RAS ≤ 0.6 binder replacement: RAP/RAS ≤ 1.5% total binder contribution; SC—≤30% aged binder of total binder from RAP/RAS; VT—No RAP in UTBWC; HE—RAP not allowed in >10 million ESAL due to limestone in RAP; WG—Total RAP/ RAS ≤ 20%, RAS ≤ 5% 11. If RAP/RAS are used, how is the amount of binder contribution determined? Solvent extraction CA, IL, IN, KY, MA, ME, MN, MO, MS, NV, OH, TN, WA, GC, HE, OC, PC Ignition oven AL, DE, FL, IN, KY, KS, MA, MN, MT, NC, NE, NM, OR, SC, TN, UT, WV, GC, OC, PRC Based on a percentage of the recovered binder AL, CO, GA, MA, MD, ND, VT, WI Back-calculated using the Gmm value AL Other (please specify): GA—gives partial credit (75%); ID—Ignition oven correction factor correlated to solvent extraction; MA—RAS not given 100% credit; MN—Solvent extraction for mix design, ignition oven for production; OH—RAS binder set at 18%; PA—If ≤15% RAP or ≤5% RAS use solvent or ignition: If >15% RAP or both RAP and RAS used, use solvent 12. What mix design method is used? Superpave (AASHTO R 35/T 312) AL, CO, FL, GA, ID, IL, IN, KS, KY, LA,MA, MD, ME, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, OH, PA, SC, UT, VT, WA, WI, GC, HE, OC, PRC, SS, WG SMA (AASHTO R46) GA, OH Marshall (AASHTO T245) AK, MO, OH, RI, TN, WV, PC Hveem (AASHTO T 246) CA, NV California Kneading Compactor (AASHTO T 247) CA Other (please specify) AZ—Agency specific; RI—Added 150 mm stability requirements; TX—Agency specific; VT—Agency specific for UTBWC 13. What air void level, or range of air void levels, is used to determine optimum asphalt content? <3.5% (No responses) 3.5–4.5% CO, MD, MT, NE, NJ (3.5), SC, UT, VT, PC 4% AL, CA, DE, FL, GA, ID, IL, KS, KY, MA, ME, MN, MO, MS, ND, NM, NV, OH, OK, OR, PA, TN, WA, WI, HE, SS, WG 4%–5% (No responses) 4%–6% MS (not for 4.75 mm), NC, RI, WV, OC, PRC Other (please specify) AR—≥10% for UTBWC; AK—3–5%; GA—4–7% for 4.75 mm; IN—5%; MN—4% for sur- face, 3% for non-surface; NH—3–5.5%; OH—4% for high truck volume, 3.5% for low truck volume; TX—20% for OGFC (PFC) 14. What laboratory performance tests are typically required? (If different from AASHTO, please provide a copy.) Moisture Susceptibility (AASHTO T 283) AL, AR, CA, CO, GA, IL, IN, KY, LA, MA, MN (Modified), MO, MT, NC, NE, NH, NJ, NM, NV, OH, OK, OR, PA, SC, VT, HE, OC, PRC, SS, WG Rutting Susceptibility (AASHTO T 340—Asphalt Pavement Analyzer) AK, GA, ID, NC, NJ, OH, OR, PA Rutting Susceptibility (AASHTO T 324—Hamburg) IL, LA, MA, MT, OK, PA, TX, VT, WA, OC, PRC, SS Flow Number (AASHTO TP 79) (No responses) Dynamic Modulus (AASHTO TP 79) (No responses)

43 Other (please specify): FL—Some areas of state use APA during mix design; GA—Hamburg, FN, E* for research info; ID—Use ASTM D 1075 instead of AASHTO T 283; MS—APA typical, but not required; ND—None; RI—None; TN—TSR by ASTM D 4867; TX—Overlay Test (TX 248-F) 15. Are there restrictions on placing thin layers during cold weather? If the restrictions are different for “hot” and “warm” mix, explain. No restrictions (No responses) Must be above freezing CA, MO, MT, WA, >45 degrees F DE, GA, IL, KY, MA, MD, NJ, NV, SC, TN, UT, HE, OC, PC, >55 degrees F AR, CO, KS, MS, OK, SS Other (please specify) AZ->70; FL->50 if <1”, >40 if >1”, >45 if PG > 64 or ARB; GA->55 ≤1” or OGFC; ID->60 for surface; IN->60; LA->50; ME-Seasonal (May 15–Sat after Sept. 15) and >50; MS->40 for WMA; NC->40; ND->40; NE-≥40; NH->50; NJ->35 for WMA; NM->60; OH-1.5”–2.9” = 40, 1.0”–1.4” = 50, <1” = 60; OR->60; PA-Calendar Dates by Region ≥ 40 for 9.5 mm, 50 for 6.3 mm; RI->50; TX->70; VT-≥50; WV->50; PCR->60 16. What tack application rates (based on residual) are used for thin lifts? 0.02–0.06 gal/sq yd CA, FL, IL, MD, ME, MN, MS, MT, NV, WV 0.02–0.08 gal/sq yd CO, ID, ND, NE, NJ, NM, PA (0.02–0.07), WG 0.04–0.08 gal/sq yd AK, GA, KY, LA, MA, MO, NC, NE, OR, UT, VT, HE, OC, PC, PRC, SS Other AZ-PG = 0.06–0.08, Emulsion = 0.08; DE-0.08–0.17; GA-0.06–0.08 for OGFC, 0.04–0.06 for others; KS-0.03 for 4.75 mm, 0.13 for UTBWC; LA->0.12 for OGFC; MN-0.2 for UTBWC; NH-0.02–0.05; RI-0.08; SC-0.05–0.15; TN-0.05–0.1 for non-milled surface, 0.08–0.12 for milled surface; TX-0.04–0.16 17. Is there a minimum thickness based on NMAS? 1.5  NMAS FL (OGFC), GA, IN, LA, PRC 2  NMAS AL, CA, ID, MD, MN, MT, TX, OC, SS 3  NMAS AK, CO, DE, FL, IL, KY, MA, MN, MO, MS, ND, NE, NJ, NM, NV, OR, SC, UT, VT, WA, GC 4  NMAS HE 18. How is density specified? % of control strip GA, ID, OH, VT % of laboratory density DE, MN, NH, WA % of theoretical AK, CA, CO, FL, GA, IL, KY, MA, MD, MO, MT, NC, ND, NE, NJ, NM, NV, OH, PA, UT, WV, OC, PRC, WG Density not measured—compact to satisfaction of engineer AL, KS, LA, MS, NC, RI, SC, TN, TX, SS Density not measured—type rollers and number of passes specified AR, AZ, IN, KS, ME, OK, OR, TN, VT 19. What mixture/pavement properties are used for acceptance? Asphalt content AK, AR, AZ, CA, CO, DE, FL, GA, IN, KY, LA, MA, ME, MN, MO, MS, MT, NC, NE, NH, NM, NV, OH, OR, PA, RI, SC, TN, VT, WA, WV, HE, OC, PR, PRC, SS, WG Gradation AK, AR, AZ, CA, CO, DE, FL, GA, IN, LA, MA, ME, MN, MO, MS, MT, NC, ND, NH, NM, NV, OH, OR, PA, RI, SC, TN, VT, WA, OC, PR, PRC Plant lab air voids AL, CO, DE, FL, ID, IL, IN, KY, MA, ME, MN, MS, MT, NC, NE, NH, NJ, NM, OR, PA, RI, TX, VT, WA, WV, HE, OC, PR, PRC, SS, WG Roadway density AK, CA, CO, DE, FL, GA, IL, KY, MA, MD, MN, MO, MT, NC, ND, NH, NJ, NM, NV, OH, PA, WA, WV, OC, PR, WG Smoothness AK, AR, CA, CO, DE, FL, GA, IL, IN, KY, LA, MA, MD, MN, MO, MS, MT, NE, NH, NJ, NM, NV, OH, OR, WA, WV, OC, PR Spread Rate AL, FL, RI, SC, PRC, WG Other ID—VMA; IL—VMA; KS—Varies by mix type; LA—Gmm variation; MS—VMA; HE—VMA

44 20. Approximately how many tons of thin overlay mixes do you place each year? Less than 100,000 AK, CA, CO, DE, IN, MD, MS, NC, NE, NJ, NV, OR, PA, RI, UT, WA, WI, WV, HE, PR, PRC, SS, WG 100,000–500,000 AL, AZ, ID, IL, KS, MA, MN, MT, ND, NH, NM, SC, TN, TX, VT 500,000–Less than 1 million ME >1 million FL, GA, KY, OH, MO, OC 21. If special procedures are used to maintain surface condition (texturing, grinding, fog seal, etc.), how is it deter- mined when those activities should be applied? No special activities are used AL, CO, FL, GA, ID, IL, KS, KY, LA, MT, ND, NJ, RI, TN, TX, VT, WA, WV, SS Based on type and level of distress AK, AZ, DE, IN, MN, MO, MS, NC, NE, NH, NM, NV, OR, PA, SC, UT, OR, PR, PRC Based on condition rating CA, IN, MN, MO, MS, NC, NM, NV, PA, SC, UT, OC Based on smoothness CA, IN, MN, MO, NM, NV, HE Automatically scheduled at periodic intervals CA, IN, MO Other OH—Decision Tree; MN—Determined by District; HE—Micromilling 22. How is the optimal application rate for fog seals or rejuvenating agents determined? No fog seals or rejuvenators are used AK, AL, FL, GA, ID, IL, KS, KY, LA, MA, MD, MN, MT, ND, NH, OH, OR, PA, RI, SC, TN, TX, HE, PC Agency standard rate is used CA, MO, MS, NC, NE, NM, NV, OK, UT, VT, WA Based on type and level of distress AZ, CA, CO, IN, NV, WV Other GA—Testing on one project; SC—Concerns due to loss of friction initially; VT—Only on FDR with cement stabilizer 23. What is the actual service life of thin asphalt concrete overlays? <5 years AK, CO, MD, MN, NC, NE, NM, TX 5–8 years AL, CA, GA, ID, IL, KS, MA, MD, MN, MO, ND, NE, NH, OK, PA, SC, TN, TX, UT, VT, WA, WV, PC 8–10 years AL, AZ, CA, DE, GA, IL, IN, KS, KY, MA, MN, MO, NJ, NV, OH, TX, OC 10–12 years AL, CA, GA, IL, KY, MN, MS, MT, NH, NV, OH, RI, TX >12 years FL, GA, KY, MN, MT 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 AL, AZ, CA, CO, GA, IL, KS, KY, MA, MN, MO, MS, NE, NV, PA, SC, VT, WA, WV, OC Amount of surface preparation AL, GA, IL, MN, MO, NV, SC, VT, WA Large fluctuations in traffic volume from project to project AZ, CA, CO, GA, KY, MN, MT, NH, OK, WA, WV, OC Variation in construction quality AZ, GA, KY, MD, MN, MO, NV, SC, TX, VT, WA, WV Other CA—Weather; FL—Geographic location; GA—Roads needing rehab were only mill/fill due to cost or other factors; NH—Variation in construction standard (Interstate vs. secondary roads); NV—Environment; OH—Regional materials and construction quality 25. How is pavement service life monitored/verified? Manual condition surveys AL, AZ, CA, FL, GA, IN, KS, KY, MA, MO, MS, NC, NE, NH, NM, OH, OR, RI, TX, VT, OC, PRC Video records of condition AK, AL, CA, ID, IL, KS, MA, MD, MN, MO, MS, ND, NE, NM, OR, PA, VT, WA, HE, OC Deterioration curves based on condition/serviceability are updated annually KS, LA, MA, MN, NJ, TN, WA Threshold values are used to determine when action is needed AK, CA, GA, IN, KS, MA, NC, NE, NJ, OH, TN, UT Other MT—Automated vehicles; PA—video logs annually on high-class project, every 2 years on lower-class projects

45 26. Are annualized cost comparisons per mile available for thin asphalt overlays versus other pavement maintenance/ preservation treatments? Yes GA, MT, TN No All agencies responded no except for yes responses. 27. Are warranties required for thin asphalt concrete overlays? Yes FL (3 years), WV No All agencies responded no except for FL and WV. 28. Do you have example projects of thin asphalt overlays that have far exceeded expectations? Yes GA, KS, LA, MN, OH, RI, TX, PC, PRC No All agencies responded no except for the yes responses listed above. 29. Do you have example projects of thin asphalt overlays that have significantly failed to meet expectations? Yes AZ, GA, KS, MO, OH, RI, PC No All agencies responded no except for the yes responses listed above. Comments GA—Led to placing two test sections at NCAT test track to try to retard reflective cracking; OH—Poor construction, not following decision tree, unforeseen loading 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. CA—Select the right candidate. GA—Make sure the correct maintenance treatment is applied to balance cost and manpower. KY—Avoid overly coarse mix designs with low AC-less durable, proper construction of longitudinal joint. MA—Surface prep and adequate tack coat are critical, improper project selection can be catastrophic. MD—Struggled with friction for 4.75 mm, changed from 4% to 5% VA for design and added fineness modulus of 3.30 to build more macrotexture. MO—Need adequate tack coat, limit visual segregation. MS—Condition of existing pavement structure and surface conditions are critical to success. MT—Must level adequately to fill ruts and improve smoothness before thin overlay, increased leveling quantities resulted in better smoothness and performance; where there is crack sealant place 0.8 in. layer to isolate crack sealant before thin overlay (eliminates the bumps). NJ—Thin overlays used successfully for pavement preservation, select road in good to fair condition; there is little improvement in smoothness because of thin layer. Can pave later in the season with WMA. NV—Material selection and construction quality control. OH—Target resurfacing after life of most recent activity is exhausted, but before structural failure occurs. Resurfacing too early is not cost-effective. PA—Sound structure and good density. RI—1.5–2.0 in. in mill-and-fill operations works well; modified binders (rubber or polymer) provide more service life; using AASHTO M19, specify E grade for preservation and V grade for 2 in. mill and fill. SC—Ensure road is not rutted and is sound structurally before paving (this may be different than when project was set up), placement rates too low may cause drag marks and other issues. TN—Never place over sections with cracks > 3⁄16 in. or areas significantly raveled or rough. TX—Use appropriate amount of tack coat for adequate bonding; may need tandem rollers for thin overlays. VT—Need well-trained construction inspectors and continual spec. improvement based on experience. OC—Proper tack coat is essential for long life; placement rate is too thin in many cases, an additional 25 LB/y2 would help achieve density and smoothness for longer life. WG—Avoid < 1 in. on slow moving urban roads; turn lanes and intersections do not perform as well.