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Impact of Asphalt Thickness on Pavement Quality (2019)

Chapter: Appendix C - Tabulated State Survey Responses

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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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Suggested Citation:"Appendix C - Tabulated State Survey Responses." National Academies of Sciences, Engineering, and Medicine. 2019. Impact of Asphalt Thickness on Pavement Quality. Washington, DC: The National Academies Press. doi: 10.17226/25498.
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72 A P P E N D I X C Tabulated State Survey Responses This section summarizes the responses to the survey as reported by the state and provincial agencies. Numbers in brackets or on Totals line in tables are the number of responses for each option [U.S. + Canadian]. Not every respondent answered every question, so totals may not match from question to question. 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? Agency Yes/Unsure/No If yes, how are these policies or guidelines enacted? AL Yes Other (Guidelines for Operations (GFO)) AK Unsure AZ Yes Pavement Design Manual, Design Memo AR Yes Pavement Design Manual CA Yes Specifications CO Yes Pavement Design Manual CT Yes Other (Guidance Document) DE Yes Specifications, Other (401699 (Exempt reasons)) FL Yes Pavement Design Manual, Specifications GA Yes Design Memo, Specifications (Section 400 of Supplemental Spec Book) ID Yes Other (Materials Manual Section 240.05.02) IL Yes Specifications IN Yes Pavement Design Manual, Specifications IA Yes Other (HMA mix selection guidelines) KS Yes Specifications KY Yes Design Memo LA Yes Specifications ME Yes Pavement Design Manual, Specifications MD Yes Pavement Design Manual MI Yes Pavement Design Manual, Specifications MN Yes Design Memo MS Yes Specifications MO Yes Specifications MT No NE Yes Specifications, Other (3 times nominal maximum size, in specifications not to exceed 2 in. in the top lift) NV No NH No NJ Yes Specifications NM Yes Pavement Design Manual, Other (LTPPBind Software) NY Yes Pavement Design Manual OH Yes Pavement Design Manual OR Yes Pavement Design Manual PA Yes Pavement Design Manual, Specifications RI Yes Design Memo

Tabulated State Survey Responses 73 (continued on next page) Agency Yes/Unsure/No If yes, how are these policies or guidelines enacted? SC No SD Yes Other (Pavement Design Engineer) TN Yes Pavement Design Manual TX Yes Specifications UT Yes Specifications VT Yes Pavement Design Manual VA Yes Specifications WA Yes Pavement Design Manual, Specifications WV Yes Pavement Design Manual, Other (Design Directive) WI Yes Specifications WY Yes Specifications AB Yes Design Memo, Specifications BC No MB Yes Design Memo, Other (As per the tender documents) NB No ON Yes Other (Reference a figure from FHWA and NAPA "HMA Pavement Selection Guide," information Series 128 in our guidelines.) Totals [Yes = 40+3; Unsure = 1; No = 4+2] 2. What are the minimum lift thicknesses specified (or typically used if not specified) for different types and sizes of mixtures by your agency? Note: The following tables show the minimum and maximum specified or typical lift thicknesses for various mix sizes (4.75, 9.5, 12.5, 19.0, 25.0, and 37.5 mm) and types (Fine and Coarse Dense-Graded, SMA, and Open-Graded) as reported by the survey respondents. Same means the same as for a fine, dense mix of that size. None means the agency does not use. N/A means the agency uses that size but does not specify a minimum and/or maximum. DNA means does not apply (the agency does not use that mix). Several agencies reported that they either do not specify a maximum lift thickness or they have one maximum regardless of mix size or type. These agencies are indicated by an asterisk in the following tables. Details are provided under Question No. 3. 4.75-mm Mixes Agency Fine Dense-Graded Coarse Dense-Graded SMA Open-Graded Min Max Min Max Min Max Min Max AL 0.72 in. 1 in. Same Same None None None None AK AZ N/A N/A AR CA ≥3 MAS Same CO 0.75 in. 1.50 in. Same Same Same Same None None CT 6.35 mm: ≤1 in. * 6.35 mm: ≤1 in. * None * None * DE N/A FL 0.5 in. (dev. spec) 0.75 in. None None None None None None GA ¾ in. 1 ⅛ in. Same Same ID 3×NMAS desired; 2.5×NMAS recommended when relaxed in construction; 2×NMAS minimum when relaxed in construction * Same * 4XNMAS when used * Not used *

74 Impact of Asphalt Thickness on Pavement Quality IL 0.75 in. 1.25 in. Same Same None None None None IN 0.28 0.56 Same Same None None None None IA None * None * None * None * KS 3×NMAS * None * None * None * KY LA None None Same None None None None None ME 2×NMAS * * * * MD 0.5 1 0.5 1 None None None None MI N/A N/A N/A N/A N/A N/A N/A N/A MN ¾ in. * Same * None * None * Agency Fine Dense-Graded Coarse Dense-Graded SMA Open-Graded Min Max Min Max Min Max Min Max MS 0.5 in. 0.75 in. Same Same None None None None MO 0.75 in. * 0.75 in. * N/A * N/A * MT * * * * NE 1 in. * Same * Same * Same * NV N/A * Same * None * None * NH 1-1.25 in. * 1-1.25 in. * NA * NA * NJ 1 in. 1.25 in. NM NY None None None None None None None None OH DNA * DNA * DNA * DNA * OR None None Same Same None None None None PA 0.625 in. 0.75 in. 0.625 in. 0.75 in. None None None None RI 1 * 1 * * * SC ¾ in. 1 in. N/A N/A N/A N/A N/A N/A SD 1 * None * None * None * TN ⅝ in. Same None None TX N/A N/A Same N/A N/A N/A N/A N/A UT 3×NMAS * 3×NMAS * 3×NMAS * * VT ¾ in. ¾ in. same same None None None None VA 2.5×NMAS 4×NMAS 2.5×NMAS 4×NMAS WA None None None None None None None None WV * * * * WI None None None None None None None None WY None None None None None None None None AB None None None None None None None None BC None * None * None * None * MB None * None * None * None * NB None * None * None * None * ON N/A 19 mm None 19 mm None None None None

Tabulated State Survey Responses 75 9.5-mm Mixes Agency Fine Dense-Graded Coarse Dense-Graded SMA Open-Graded Min Max Min Max Min Max Min Max AL 1.25 in. 2 in. Same Same Same Same 0.81 in. 0.81 in. AK AZ N/A N/A 0.5 in. over AC and 1 in. over PCCP 0.5 in. over AC and 1.0 in. over PCCP AR 1.5 in. 3.0 in. 1.5 in 3.0 in. CA ≥3 MAS Same CO 1.125 in. 2.50 in. Same Same Same Same None None CT 1.25 in. * 1.25 in. * None * None * DE 1.25-2 in. Same Same FL 1.0 in. 1.5 in. None None None None None None GA Type 1 ⅞ in., Type 2 1⅛ in. Type 1 ¼ in., Type 2 1½ in. Same Same 1⅛ in. 1½ in. 55 psy Spread Rate Spread Rate of 65 psy ID * * * * IL 1.25 in. None Same None None None None None IN 1 2 Same Same 1 2 1 2 IA 1 in. * Same * None * None * KS 3×NMAS * 3×NMAS * None * None * KY 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS 3xNMAS 4.5×NMAS LA None None Same None None None None None ME 3xNMAS * 1.5 in. * * * MD 1 2 1 2 1 1.5 None None MI 165 psy 220 165 psy 220 165 psy 220 N/A N/A MN 1.5 in. * Same * None * None *1 MS 1 in. 1.5 in. Same Same 1 in. 1.5 in. 0.75 in. 1 in. MO 1.25 in. * 1.25 in. * 1.25 in. * N/A * MT 0.10 ft * 0.10 ft * * * NE 1.5 in. * Same * Same * Same * NV N/A * Same * None * N/A * NH 1-1.25 in. * 1-1.25 in. * NA * NA * NJ 1.5 in. ¾ in. NM NY 1½ in. 2 in. Same Same None None None None OH 1 in. * 1 in. * DNA * DNA * OR 1 in. 3 Same Same None None None 3 PA 1 in. ≤1.5 in. 1.5 in. 2 in. 1.5 in. 1.5 in. None None RI 1.5 in. * 1.5 in. * 1 in. * * SC 1.25 in. 2 in. N/A N/A N/A N/A N/A N/A SD 1.5 in. * None * 1.25 in. * None * TN ¾ in. Same None None TX 1.25 in. 2 in. Same Same 1.25 in. 2 in. N/A N/A UT 3×NMAS * 3×NMAS * 3×NMAS * * VT 1½ in. 1½ in. Same Same None None None None VA 2.5×NMAS 4×NMAS 2.5×NMAS 4×NMAS 2.5×NMAS 4×NMAS WA 0.10 ft 0.15 ft Same Same None None None None WV * * * * WI 1.5 in. 2 in. 1.5 in. 2 in. 1.5 in. 2 in. None None WY 1 in. 2 in. 1 in. 2 in. None None None None AB 20 mm 30 mm Same Same None None None None BC None * None * None * None * MB None * None * None * None * NB None * Min 38 mm; typical 50 rehab, 38 new * Min 38mm * None * ON N/A 25 mm None 37.5 mm None N/A None None

76 Impact of Asphalt Thickness on Pavement Quality 12.5-mm Mixes Agency Fine Dense-Graded Coarse Dense-Graded SMA Open-Graded Min Max Min Max Min Max Min Max AL 1.50 in. 2.5 in. Same Same Same Same None None AK AZ 1-2 in. for 409 Mix N/A N/A AR 2.0 in. 4.0 in. 2.0 in 4.0 in. CA ≥3 MAS Same CO 1.50 in. 3.00 in. Same Same Same Same None None CT 2 in. * 2in. * None * None * DE 2-2 in. Same Same FL 1.5 in. 2.5 in. None None None None 0.75 in. 0.75 in. GA 1⅜ in. 2½ in. Same Same 1⅜ in. 3 in. 85 psy 110 psy ID * * * * IL None None None None 2.0 in. None None None IN 1.5 in. 3 in. Same Same 1.5 in. 3 in. None None IA 1.5 in. * Same * None * None * KS 3×NMAS * 3×NMAS * None * None * KY 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS LA 1.5 in. 2.0 in. Same Same 1.5 in. 2.0 in. ≤1.5 in. None ME 3×NMAS * 1.75 in. * * * MD 1.5 in. 3 in. 1.5 in. 3 in. 1.5 in. 2 in. None None MI 220 275 220 275 220 220 N/A N/A MN 2 in. * Same * 2 in. * None * MS 1.5 in. 2.5 in. Same Same 1.5 in. 2.5 in. 1 in. 1.25 in. MO 1.75 in. * 1.75 in. * 1.75 in. * N/A * MT 0.12 ft * 0.12 ft * * * NE 1.5 in. * Same * Same * Same * NV N/A * Same * None * N/A * NH 1.5 in. * 1.5 in. * NA * NA * NJ 2 in. 2 in. 1.25 in. NM NY 1.5 in. 2 in. Same Same None None None None OH 1.5 in. * 1.5 in. * 1.5 in. * DNA * OR 2 in. 3 in. Same Same None None 1.5 in. 3 PA 2 in. 3 in. 2 in. 3 in. 2 in. 2 in. None None RI 2 in. * 2 in. * 1.5 in. * * SC 2 in. 2 in. 2 in. 2 in. N/A N/A 1.125 in. 1.4 in. SD 1.5 in. * None * 1.5 * None * TN 1.25 in. 1.5 in. Same None 1 1/4in. TX 1.5 in. 3 in. Same Same 1.5 in. 3 in. N/A N/A UT 3×NMAS * 3×NMAS * 3×NMAS * * VT 2 in. 2 in. Same Same None None None None VA 2.5×NMAS 4×NMAS 2.5×NMAS 4×NMAS 2.5×NMAS 4×NMAS WA 0.15 ft 0.35 ft Same Same None None None None WV * * * * WI 1.75 in. 2.5 in. 1.75 in. 2.5 in. 1.75 in. 2.5 in. None None WY 1.5 in. 3 in. 1.5 in. 3 in. None None None None AB 40 mm (typical) 70 mm Same Same None None None None BC 2.5×NMAS * 2.5×NMAS * None * None * MB None * None * None * None * NB None * None * None * None * ON 40mm 50 mm 50 mm 75 mm 40 mm 60 mm None None

Tabulated State Survey Responses 77 19.0-mm Mixes Agency Fine Dense-Graded Coarse Dense-Graded SMA Open-Graded Min Max Min Max Min Max Min Max AL 2.25 in. 3.15 in. Same Same Same Same None None AK AZ 2-2.5 in. 416 & 417 Mix 5.0 in. in Trench and 4.0 in. in overlay N/A N/A AR CA ≥3 MAS * Same * * * CO 2.25 in. 3.50 in. Same Same Same Same None None CT None * None * None * None * DE 2.25-4 in. Same N/A FL 2.0 in. 4.0 in. None None None None None None GA 1¾ in. 3 in. Same Same 1¾ in. 3 in. ID * * * * IL 2.25 in. 4.0 in. Same Same None None None None IN 2 in. 4 in. Same Same 2 in. 4 in. 2 in. 4 in. IA 2 in. * Same * None * None * KS 3×NMAS * 3×NMAS * None * None * KY 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS LA 2.0 in. 3.0 in. Same Same 1.5 in. 2.0 in. ≤1.5 in. None ME 3×NMAS * 2.5 in. * * * MD 2 in. 4 in. 2 in. 4 in. 2 in. 2.5 in. None None MI 330 410 330 410 N/A N/A N/A N/A MN 3 in. * Same * None * None * MS 2.25 in. 3.5 in. Same Same 2.25 in. 3.5 in. None None MO 2.25 in. * 2.25 in. * N/A * N/A * MT 0.15 ft * 0.15 ft * * * NE 2 in. * Same * Same * Same * NV N/A * Same * None * None * NH 1.5-2 in. * 1.5-2 in. * NA * NA * NJ 3 in. NM NY 2 in. 3 in. Same Same None None None None OH 1.75 in. * 1.75 in. * DNA * DNA * OR 3 in. 3 in. Same Same None None 2 in. 3 in. PA 2.5 in. 4.5 in. 2.5 in. 4.5 in. None None None None RI 3 in. * 3 in. * * * SC 2.5 in. 3 in. 2.5 in. 3 in. N/A N/A N/A N/A SD * None * None * None * TN None None None None TX 2 in. 4 in. Same Same 2.25 in. 4 in. N/A N/A UT 3×NMAS * 3×NMAS * 3×NMAS * * VT 3 in. 3-1/4 in. Same Same None None None None VA 2.5×NMAS 4×NMAS 2.5×NMAS 4×NMAS 2.5×NMAS 4×NMAS WA 0.22 ft 0.35 ft Same Same None None None None WV * * * * WI 2.25 in. 3 in. 2.25 in. 3 in. None 3 in. None None WY 2 in. 3 in. 2 in. 3 in. None None None None AB 80 mm 100 mm Same Same None None None None BC 2.5×NMAS * 2.5×NMAS * None * 2.5×NMAS * MB 50 mm typical * None * None * None * NB None * * None * None * ON 50 mm 70 mm 50 mm 75 mm None None None None

78 Impact of Asphalt Thickness on Pavement Quality 25.0-mm Mixes Agency Fine Dense-Graded Coarse Dense-Graded SMA Open-Graded Min Max Min Max Min Max Min Max AL 3.00 in. 3.15 in. Same Same Same Same None None AK AZ N/A N/A AR 3.0 in. 5.0 in. 3.0 in. 5.0 in. CA ≥3 MAS * Same * * * CO 3.00 in. 4.00 in. Same Same None None None None CT 3 in. * 3in. * None * None * DE 3-6 in. SAME N/A FL None None None None None None None None GA 3 in. 5 in. Same Same ID * * * * IL None None None None None None None None IN 3 in. 6 in. Same Same None None 3 in. 6 in. IA 3 in. * Same * None * None * KS None * None * None * None * KY 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS LA 2.5 in. 4.0 in. Same Same None None None None ME * * * * MD 3 in. 5 in. 3 in. 5 in. None None None None MI 435 550 435 550 N/A N/A N/A N/A MN None * Same * None * None * MS 3 in. 4 in. Same Same None None None None MO 3.00 in. * 3.00 in. * N/A * N/A * MT * * * * NE None * None * None * None * NV N/A * Same * None * None * NH 3 in. * 3 in. * NA * NA * NJ 4 in. NM NY 2½ in. 4 in. Same Same None None None None OH DNA * DNA * DNA * DNA * OR None None Same Same None None None None PA 3 in. 5.5 in. (for binder course only) No max (as required) for base course 3 in. 5.5 in. (for binder course only) No max (as required) for base course None None None None RI * * * * SC 3 in. 4.5 in. 3 in. 4.5 in. N/A N/A N/A N/A SD None * None * None * None * TN 2¼ in. 2¾ in. Same None None TX 2.5 in. 5 in. Same Same N/A N/A N/A N/A UT 3×NMAS * 3×NMAS * 3×NMAS * * VT 3.5 in. 4 in. Same Same None None None None VA 2.5×NMAS 4×NMAS 2.5×NMAS 4×NMAS WA 0.30 ft 0.35 ft Same Same None None None None WV * * * * WI 3 in. 4 in. 3 in. 4 in. None None None None WY None None None None None None None None AB None None None None None None None None BC None * 2.5×NMAS * None * 2.5×NMAS * MB None * None * None * None * NB None * None * None * None * ON 80 mm 100 mm N/A 100 mm None None None None

Tabulated State Survey Responses 79 37.5-mm Mixes Agency Fine Dense-Graded Coarse Dense-Graded SMA Open-Graded Min Max Min Max Min Max Min Max AL None None None None None None None None AK AZ N/A N/A AR 4.0 in. 12.0 in. 4.0 in. 12.0 in. CA CO None None None None None None None None CT None * None * None * None * DE N/A N/A N/A FL None None None None None None None None GA Same Same ID * * * * IL None None None None None None None None IN None None None None None None None None IA None * Same * None * None * KS None * None * None * None * KY 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS 3×NMAS 4.5×NMAS LA 4.0 in. 4.0 in. Same Same None None None None ME * * * * MD 4 in. 6 in. 4 in. 6 in. None None None None MI N/A N/A N/A N/A N/A N/A N/A N/A MN None * Same * None * None * MS None None Same Same None None None None MO N/A * N/A * N/A * N/A * MT * * * * NE None * None * None * None * NV None * Same * None * None * NH NA * NA * NA * NA * NJ NM NY 3 in. 5 in. Same Same None None None None OH 4 in. * 4 in. * DNA * DNA * OR None None Same Same None None None None PA 4.5 in. No max (as designed) 4.5 in. No max (as designed) None None None None RI * * * * SC N/A N/A N/A N/A N/A N/A N/A N/A SD None * None * None * None * TN 3 in. 4 in. Same None 3 in. drainable base TX 3 in. 6 in. Same Same N/A N/A N/A N/A UT 3×NMAS * 3×NMAS * 3×NMAS * * VT 5.5 in. 5.5 in. Same Same None None None None VA WA None None None None None None None None WV * * * * WI 4.5 in. 4.5 in. 4.5 in. 4.5 in. None 4.5 in. None None WY None None None None None None None None AB None None None None None None None None BC None * None * None * None * MB None * None * None * None * NB None * None * None * None * ON 100 mm 150 mm N/A 150 mm None None None None

80 Impact of Asphalt Thickness on Pavement Quality 3. Do you specify different maximum lift thicknesses depending on mixture size and/or type? Yes [26+2] No, do not specify a maximum or have one maximum regardless of mixture size (please specify maximum value). [17+3] AL, AZ, AR, CO, DE, FL, GA, IL, IN, KY, LA, MD, MI, MS, NJ, NY, OR, PA, SC, TN, TX, VT, VA, WA, WI, WY, AB, ON CA, CT, ID, IA, KS, ME, MN, MO, MT, NE, NV, NH, OH, RI, SD, UT, WV, BC, MB, NB Comments: ID – 0.3 in. is generally the maximum thickness used. IA – 3 in., could be more if contractor can demonstrate they can achieve acceptable density. KS – 2-in. surface lifts, 4-in. base lifts. MN – 3 in. MO – MoDOT does not specify maximum lift thicknesses, but would not by design purposely specify a lift thickness for smaller NMAS mixes (045, 095, 125) much greater than the minimum, if for no other reason than because of their higher cost. MT – We don’t specify a maximum value. NV – Max 3 in. (75 mm). NH – Only one thickness is specified, not a range. RI – We will specify on plans. UT – 3×NMAS. MB – 50 mm is typical, 40 mm would be minimum. 4A. Are there situations in which your agency may grant exceptions to these allowable lift thicknesses? Yes [30+3] Maybe [9] No [4+1] AL, AR, CO, DE, GA, ID, IL, IN, KS, KY, LA, ME, MI, MO, MT, NE, NV, NJ, OH, OR, PA, RI, SC, SD, UT, VT, VA, WA, WV, WI, AL, BC, ON CT, FL, IA, MD, MN, NH, NY, TN, TX AZ, CA, MS, WY, NB 4B. If yes or maybe, when and why would you consider making exceptions? AL – For Constructability, Grade Restrictions, or Drainage Restrictions 0.25 in. to 0.5 in. may be added to the max to maintain where necessary longitudinal profile. AR – Correcting cross slope in superelevation; Raising grade on existing pavement in vertical curve. CO – The 4.74-mm mix is usually a leveling course and may go thinner depending on the depth of the ruts. For functional overlays used in preventive maintenance or other treatments, thinner lifts are allowed. The 25-mm mix should not be used as a surface layer. The 19- and 25-mm mixes may be thicker for full depth patching. CT – We may consider making an exception for the 12.5-mm mix to allow 1.5 in. DE – Wedge/weird circumstances when violate on either upper or lower end we waive compaction requirements. FL – Isolated instances of constructability concerns concerning drop off criteria with limited lane closure times. GA – Spec. 400 has a proposed changes concerning lift thicknesses including maximum total thicknesses. ID – See response to question 2 and Section 240.05.02 of the ITD Materials Manual. Response to Question 2: Contractors want to split lifts to get higher smoothness bonuses so allowances were made to let the Resident Engineer reduce the lift thickness if they felt it was needed but they have to consider the items outlined in the Material Manual. IL – Level binder applications on some projects have variable depth designations in IL.

Tabulated State Survey Responses 81 IN – For the situation described below, where 19.0 mm is substituted for 25.0-mm base. We “unofficially” would allow the 19.0 intermediate to be laid up to 6 in. thick, instead of the normal 4- in. maximum. If QC/QA-HMA 19.0-mm over QC/QA-HMA 25.0-mm mixtures are specified, QC/QA- HMA 19.0-mm mixture may be considered as a substitute for the QC/QA-HMA 19.0-mm and QC/QA-HMA 25.0-mm mixtures upon a written request by the Contractor. The request for the substitution shall be prepared in advance of the work. A computation will be made in order to obtain a unit price for the QC/QA-HMA 19.0-mm mixture. The quantity and amount for QC/QA- HMA 19.0-mm mixture shall equal the sum of the contract quantities and amounts shown for QC/QA-HMA 19.0-mm and QC/QA-HMA 25.0-mm mixtures. The unit price for QC/QA-HMA 19.0- mm mixture shall be equal to the sum of contract amounts divided by the sum of contract quantities. Payment for the QC/QA-HMA 19.0-mm mixture will be made at the unit price per ton for QC/QA-HMA 19.0-mm mixture. No payment will be made for additional work or costs which may result due to this change. IA – Base mixes of a full depth pavement if the contractor demonstrates they can achieve density. KS – If 4.75-mm or 9.5-mm fine dense-graded mixes are used for single lift overlays then they are typically specified as ¾ in. thick and 1 in. thick, respectively. KDOT has specified 1-in.-thick leveling courses or “scratch coats” with 12.5-mm fine dense-graded mixes. KY – Maintenance surfacing projects or shoulder applications. LA – Deep Patching. Confined, so density is typically not an issue. Time constraints on lane closures. ME – We have a ¾-in. overlay surface with a 9.5-mm NMAS mixture. We also use ultrathin bonded wearing surface (NovaChip) which are designed to one stone thick. MD – Sometimes we allow to construct ±1 in. for construction convenience mostly for base course layers. MI – Unique situations where it is justified. MN – Sometimes in wedge paving or paving a widening block. Typically do not pave greater than 3 in. on mainline paving. MO – When used for leveling under a wearing course. MT – If approved by the project manager. NE – If they need to place a “scratch course” to smooth out rough existing base material. If they are doing superelevation slope correction. NV – In certain situations, e.g., patching with limited lane closure durations possible, etc., 4-in. max. thickness may be permitted upon request. This allowance is only permitted upon demonstration of adequate density throughout the thickness, verified by core densities of top and bottom of thickness. NH – Thin lifts are typically on maintenance overlay projects. Out-of-shape roads may need greater thickness due to dragging. NJ – Depending on the geometry of the roadway some areas may have to be paved thicker but the overall average should be very close to the design thickness. NY – Superelevation issues. OH – Construction project constraints unforeseen. OR – Leveling in localized areas … up to 4 in. thick and leveling to 0 in. In some situations, especially with traffic mobility challenges, when paving in a slot (mix contained at both longitudinal edges), up to 4 in. thick, requiring lower-frequency, higher-amplitude settings on the rollers. PA – Different minimum and maximum lift thickness if the NMAS was used for a scratch or leveling course (see Pub. 242 Pavement Policy Manual, Table 10.5). Bridge Decks (see Pub. 242, Section 2.6). There may be an exception to the minimum thicknesses in Pub. 242, Table 10.4, where there is a parking lane and where curb reveal is critical. In these cases, the wearing course may be tapered to a 1-in. depth at the curb (only within the parking lane). RI – Maximum lift thickness is used to ensure rideability and adequate compaction during warm weather. SC – We are experimenting with placing a 12.5 intermediate (coarse graded) mixture in up to 7 in. at one time using WMA tech (chemical) with 25% to 30% RAP. This is a possible solution to our rapid deep repairs needed to fix failures we are seeing on our interstates. The ability to close a lane and do 10- 12 in. mill and fill with two lifts in one night and return to traffic by 6:00 a.m. - The mix must be confined ... i.e., I-85 Spartanburg and 2018 NCAT Test Track. SD – Some mixes are compacted by specified roller coverage not in place density specification. TN – To meet design structural numbers cost-effectively. Considering increasing lift thickness of 4.75 mixes based on recent NCAT Test Track experience.

82 Impact of Asphalt Thickness on Pavement Quality TX – Not allowed in the specification, but area office may consider to accommodate speed of construction (i.e., intersection construction that would allow for thicker base HMA layers). However, this creates additional caveats in testing for in-place air voids, and considered the exception to the rule. UT – Transition zones or asphalt as a base. VT – Shim/leveling courses with ⅜ mix (½ in. to ¾ in. thick). VA – Occasionally the project engineer will allow higher lift thicknesses if the contractor can show that they can achieve density. Allowing the contractor to place a single 5-in. lift of BM-25.0 rather than two 2.5-in. lifts for example. Also, for 4.75 mm, pavement design guide recommends 0.75 to 1.0 in. thick (layer thickness but don't think we have two lifts for 4.75 to get 1 in.). WA – In situations where the minimum thickness is not feasible such as bridge decks where dead load limits the lift thickness. Where existing conditions require a thinner lift to match into adjacent pavement or structures. For economy when project budgets are insufficient. WV – Where political pressures and paving budgets do not align. WI – Lower layers are allowed thicker. Temporary pavement may be placed in one lift. AB – Mill and inlay greater than 70 mm: would allow one lift to be placed versus two lifts. Superelevation correction on curves. Site-specific constructibility concerns—not a formal documented process. BC – Entirely project and mix dependent. Mainly (but infrequently) done where grade adjustments are required on construction projects—not on repaving projects. ON – Use of new compaction technologies and other trials. Miscellaneous paving and leveling. 5. What are your agency’s target density requirements for dense-graded mixtures? (For PWL specs, please indicate minimum density required for 100% pay.) Specified Target Density Agency <92% of mix theoretical maximum specific gravity (Gmm) [3+0] KS, NH, WY 92% of mix theoretical maximum specific gravity (Gmm) [17+1] AR, CO, CT, ID, IN, IA, LA, MD, MO, NV, NJ, OR, PA, SD, TN, VA, WA, BC 92.5% of mix theoretical maximum specific gravity (Gmm) [2+1] MI, NE, NB 93% of mix theoretical maximum specific gravity (Gmm) [5+0] AZ, FL, MT, RI, SC >93% of mix theoretical maximum specific gravity (Gmm) [3+0] NY, OH, UT Other [13+2] AL, CA, DE, GA, IL, ME, MN, MS, NH, TX, VT, VA, WI, AB, ON Comments: AL – Greater than 94%. CA – 91-97% of Gmm. CO – CDOT uses PWL. Therefore, minimum density is 92% Gmm with a zero standard deviation. DE – ≥92% Gmm for surface courses and ≥90% for base and binder courses. FL – Section 334, http://www.fdot.gov/programmanagement/Implemented/SpecBooks/January2018/ Files/118eBook.pdf. GA – See email; The targeted maximum Pavement Mean Air Void content for all Superpave and Stone Matrix Asphalt mixtures is 5.0%; therefore 95% of mix maximum theoretical specific gravity. ID – We use 91% minimum when using nuclear gauge to account for variability. New specification increased it to 92%. IL – PFP (http://www.idot.illinois.gov/Assets/uploads/files/Doing-Business/Specialty-Lists/Highways/ Design-&-Environment/BDE-Special-Provisions/80347.pdf). QCP (http://www.idot.illinois.gov/Assets/uploads/files/Doing-Business/Specialty-Lists/Highways/ Design-&-Environment/BDE-Special-Provisions/80383.pdf). IN – http://www.in.gov/dot/div/contracts/standards/book/sep17/4-2018.pdf, line 714. IA – https://iowadot.gov/erl/current/IM/content/510aa.htm. KS – http://www.ksdot.org/Assets/wwwksdotorg/bureaus/burConsMain/specprov/2015/PDF/15- 06007.pdf (for PWL specs the LSL is 91.00% of Gmm for lifts that are 2 in. thick or less and 92% of Gmm for lifts that are greater than 2 in. thick. LA – http://wwwsp.dotd.la.gov/Inside_LaDOTD/Divisions/Engineering/Standard_Specifications/ Standard%20Specifications/2016%20Standard%20Specifications%20for%20Roads%20and%20Bridg es%20Manual/09%20-%202016%20-%20Part%20V%20-%20Asphalt%20Pavements.pdf. ME – http://maine.gov/mdot/contractors/publications/standardspec/docs/2014/div400.pdf [95.0±2.5%].

Tabulated State Survey Responses 83 MD – https://policymanual.mdot.maryland.gov/mediawiki/index.php?title=504_ASPHALT_PAVEMENT. MI – 92.5% min., PWL spec (recently raised from 92%). MN – 92% when mix has 4.0% design voids. 93% when design voids are 3.0%. MS – 1. For leveling lifts where full lane width is paved and a minimum thickness requirement as specified in the table in Subsection 401.02.4 is met, the required lot density shall be 92.0 percent of maximum density. For all other leveling, no density shall be required but the pavement shall be rolled to refusal densification. 2. For all single lift overlays, with or without a leveling lift and/or milling, the required lot density shall be 92.0 percent of maximum density. 3. For all multiple lift overlays of two (2) or more lifts excluding leveling lifts, the required lot density of the bottom lift shall be 92.0 percent of maximum density. The required lot density for all subsequent lifts shall be 93.0 percent of maximum density. 4. For all pavements on new construction except shoulders that are untreated, the required lot density for all lifts shall be 93.0 percent of maximum density. For all pavements on shoulders that are untreated, the required lot density for all lifts shall be 92.0 percent of maximum density. MO – http://www.modot.org/business/standards_and_specs/highwayspecs.htm (Sec 403.5.2). MT – Incentive for 94% to 95%. NE – 92.5% Gmm. NV – PWL, 92% Min. Section 402.03.06 https://www.nevadadot.com/doing-business/contractors- construction/contract-services/standard-specifications-and-plans, 92-96% Gmm. NH – Section 401.3.12 https://www.nh.gov/dot/org/projectdevelopment/highwaydesign/ specifications/documents/2016NHDOTSpecBookWeb.pdf. NJ – 92-98% Gmm. OH – http://www.dot.state.oh.us/Divisions/ConstructionMgt/OnlineDocs/Pages/2016-Online-Spec- Book.aspx See Section 446. OR – For any granted late season Paving (after 10/01), 93% of Gmm minimum. PA – Previous link to Pub. 408 and Section 409 is older Superpave specifications with highest minimum density for overlays placed on stable bases (i.e., what we call RPS Construction) is individual sublot density cores ≥92% of mix maximum theoretical specific gravity for Superpave Wearing Courses and all individual sublot cores ≥93% of mix maximum theoretical specific gravity for SMA Wearing Courses. For the past 2+ years, PennDOT has been using full PWL specifications and highest density requirements (RPS construction) has PWL lower and upper limits for density at 92.0% and 98.0% of mix theoretical maximum specific gravity. PWL specification is currently not included in Pub. 408, but is included in contracts by Standard Special Provision. SC – see SC M 400 the SCDOT specification dated 1-1-18. 105% > 94.0 % Gmm. SD – 92.0 to 96.0 PWL. TN – https://www.tn.gov/tdot/tdot-construction-division/transportation-construction-division- resources/transportation-construction-2015-standard-specifications.html. TX – Not sure if this is in-place or lab molded density. Reference item 341 in txdot specification book: http://ftp.dot.state.tx.us/pub/txdot-info/des/specs/spec-book-jan-june-15-letting.pdf. UT – http://www.udot.utah.gov/main/uconowner.gf?n=31730316757114651. VT – PWL Based 92.5% to 96.5% range (97% for base courses). VA – ≥92.5% Gmm for SM 9.5A and 12.5A, ≥92.2 % Gmm for other SM, IM, BM. WA – WSDOT is currently transitioning from 91% minimum to 92% minimum of theoretical maximum. WI – 93% for surface in most situations, lower for layers placed on gravel and shoulders, <92% of mix theoretical maximum specific gravity (Gmm), http://wisconsindot.gov/rdwy/stndspec/ss-04- 60.pdf#ss460. AB – The majority of our mixes are Marshall mixes, for these, target densities are based on % Marshall Density, and are dependent on lift thickness or location (ie., top or lower lift). Target for Superpave mixes is >93% and is based on % Gmm. http://www.transportation.alberta.ca/images/Standard_Specifications_for_Highway_Construction _2013.pdf. BC – www2.gov.bc.ca/gov/content/transportation/transportation-infrastructure/engineering-standards- guidelines/standard-specifications-for-highway-construction. NB – ≥92.5%. ON – 92% is the lower limit for Superpave mixes and 93% is the lower limit for SMA mixes. Use PWL. 100% pay for PWL of 90 and up.

84 Impact of Asphalt Thickness on Pavement Quality 6. Are target densities the same if compaction is limited to static mode? Yes [30+4] No [10+0] AL, AZ, AR, CA,CO, CT, IL, IN, IA, LA, ME, MD, MI, MS, MO, MT, NE, NV, NH, NJ, NY, RI, SC, TN, TX, UT, VT, WA, WI, WY, AB, BC, NB, ON DE, FL, GA, KS, MN, OH, OR, PA, SD, VA Comments: DE – Waive spec if direct to static roll. GA – Static mode is only used of areas where utility structures may be damaged. KS – An approved rolling procedure (in static mode) is required for lifts that are less than 1.5 in. thick. Density specs are not applicable. MN – Oftentimes no density requirement when static mode is used. OH – Project level decision and negotiated with contractor. OR – Method Spec minimum 4 coverages, plus additional as directed when limited to static mode. PA – If project location or conditions warrant individual project specifications that restrict vibratory roller compaction, such as in towns with aging utilities beneath pavements, density is typically accepted by optimum rolling pattern using the allowed compaction methods (i.e., static mode). VA – Yes, in general. For 4.75 and 9.0 (thin) mixes, can be accepted based on peak nuclear density from roller pattern and control strip. Cores are not taken for density. 7A. How is pavement density measured by your agency? (Please click all that apply.) Agency Nuclear Density Gauge Non-Nuclear Density Gauge Cores Other AL • AK AZ • AR • • CA • CO • • CT • DE • FL • GA • • ID • • IL • IN • IA • KS • • KY • LA • • • • ME • MD • MI • MN • MS • • MO • MT • NE • • NV • • • NH • NJ • • • NM NY • • • OH • OR • • PA • • • • RI • • •

Tabulated State Survey Responses 85 Agency Nuclear Density Gauge Non-Nuclear Density Gauge Cores Other SC • • • SD • • TN • • TX • UT • VT • • • • VA • • WA • WV WI • • WY • AB • BC • MB NB • ON • Totals 21+0 7+0 39+4 6+0 Comments: ID – We use cores to correlate the Nuclear Density Gauge during the Acceptance Test Strip. LA – Moving to nondestructive QA. Currently QA: Core; QC: Gauge. NV – Nuclear gauge correlated to test strip cores. OR – Core correlated nuclear gauges on all projects over 12,500 tons. PA – Predominantly, pavement cores are used for density acceptance, followed by optimum rolling pattern using nuclear or nonnuclear density gauges. RI – Cores for more than 5,000 tons. VT – Agency acceptance by cores only (Contractor QC by gauges calibrated by select cores).

86 Impact of Asphalt Thickness on Pavement Quality 7B. If cores are used, how does your agency determine the bulk specific gravity (Gmb) of cores? AASHTO T 166, "Standard Method of Test for Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-Dry Specimens [25] AR, CO, DE, IL, IN, LA, ME, MD, MI, MS, MO, MT, NE, NH, NJ, NY, OH, RI, SC, SD, TN, UT, VT, WI, WY AASHTO T 275, Standard Method of Test for Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Paraffin-Coated Specimens [1] CA 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 [1] CT State test method [9+2] o AZ – State method ARIZ 415. o FL – FM 1-T 166. o IA – IM 321. o KS – KT-15 Procedure III (Similar to T 166). o MN – Use T166 for most mixes. But Require ASTM D6752 when 45% or less pass the #4 sieve. Require ASTM D6752 on SMA. o NV – Nev T336. o PA – PTM No. 715 (modification of AASHTO T 166) and PTM No. 716 (modification of AASHTO T 275). o TX – Tex-207-F, allows for multiple options depending on absorption and mixture type. o VA – VTM-6. o AB – ATT-7: Saturated Surface Dry (immersion) similar to AASHTO T 166. o ON – MTO Laboratory Standard 262. Other [2+2] o AL – T 166 is used where absorption is less than 2%. For mixes where absorption is >2% then Contractor choice on T 275 or T 331. o GA – All of the above plus GDT-39 for State method. o BC – ASTM D2726. o NB – ASTM D2726, AASHTO T 209.

Tabulated State Survey Responses 87 8A. Have you observed paving contractors having more difficulty in obtaining required field densities since implementing the Superpave mix design system? Agency Yes, initially but less so now Yes, continuing to be difficult Yes, with certain mixes or applications No Unsure Have not implemented Superpave AL • AK AZ • AR • CA • CO • CT • DE • FL • GA • ID • IL • IN • IA • KS • KY • LA • ME • MD • MI • MN • MS • MO • MT • NE • NV • NH • NJ • NM NY • OH • OR • PA • RI • SC • SD • TN • TX • UT • (continued on next page)

88 Impact of Asphalt Thickness on Pavement Quality Agency Yes, initially but less so now Yes, continuing to be difficult Yes, with certain mixes or applications No Unsure Have not implemented Superpave VT • VA • WA • WV WI • WY • AB • BC • MB NB • ON • Totals 16+0 2+0 4+1 11+2 6+0 3+1 Comment: VA – Wanted to say “NO,” but changed density requirements, mix design parameters (gyration level, design AV, gradation, etc.).

Tabulated State Survey Responses 89 8B. If the situation has improved, what changed? Agency Response AL Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Mix design parameters (gyration level, minimum binder content, etc.) have been revised. AR Other: Contractors have learned to perform compaction on mat at proper temperatures. Have adjusted rate of paving train to accomplish. CO Density requirements have been revised after implementing Superpave. Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Other: The Contractors have made adjustments to roller patterns and are using better and heaver equipment (when needed). CT Lift thicknesses have been increased. DE FL Lift thicknesses have been increased. Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Other: In addition to increasing minimum lift thicknesses, FDOT began measuring density with cores instead of nuclear density gauges. The contractors started using more effective compaction methods (vibratory and rubber-tire). More recently (2005) we gave the contractor the option to place coarse or fine graded mixtures. Then (around 2010) we eliminated coarse graded mixtures altogether. GA Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Mix design parameters (gyration level, minimum binder content, etc.) have been revised. Other: Permeability in Spec 828. ID Other: ITD was a Hveem state and we used ¾-in. NMAS almost exclusively. Started Superpave using them and then reduced size. ME Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Mix design parameters (gyration level, minimum binder content, etc.) have been revised. Smaller NMAS mixtures are used in certain lifts (e.g., 9.5 mm instead of 12.5 mm). MD Other: Adjusted roller patterns. NH Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Other: Gradations have migrated to become more similar to our Marshall mixes. NY Mix design parameters (gyration level, minimum binder content, etc.) have been revised. OH Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Other: They figured it out but we went to lower gyrations also. RI Other: Minimum design VMA 1.5% greater than M 323, all mixes designed at 50 gyrations, minimum binder contents specified, rutting is not an issue due to the use of PG 64E-28 and all manufactured aggregate. SD Lift thicknesses have been increased. Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Mix design parameters (gyration level, minimum binder content, etc.) have been revised. UT Other: Industry has adapted to the change. VT Density requirements have been revised after implementing Superpave. Finer mixes (gradation above primary control sieve, PCS) are now more common than coarse (below PCS). Mix design parameters (gyration level, minimum binder content, etc.) have been revised. Smaller NMAS mixtures are used in certain lifts (e.g., 9.5 mm instead of 12.5 mm). VA Other: Changed density requirements, mix design parameters (gyration level, design AV, gradation, etc.). 8C. When your agency implemented Superpave, did you keep the same density requirements or did you change the density requirements for Superpave mixtures? Kept the same density Requirements [17+2] Changed density requirements when Superpave was implemented [18+1] AL, AR, CA, CT, LA, MD, MI, MS, MT, NE, NH, NY, OH, PA, WA, WI, WY, AB, NB AZ, CO, FL, GA, IL, IN, IA, KS, ME, MN, MO, NJ, OR, RI, TX, UT, VT, VA, ON

90 Impact of Asphalt Thickness on Pavement Quality 9A. Has your agency changed recommended or required lift thicknesses since implementing the Superpave mix design system? Agency Yes No Unsure Have not implemented Superpave AL • AK AZ • AR • CA • CO • CT • DE • FL • GA • ID IL • IN • IA • KS • KY • LA • ME • MD • MI • MN • MS • MO • MT • NE • NV • NH • NJ • NM NY • OH • OR • PA • RI • SC • SD • TN • TX • UT • VT • VA • WA • WV WI • WY • AB • BC • MB NB • ON • Totals 13+1 15+2 10+0 3+1

Tabulated State Survey Responses 91 9B. If yes, what was the reason for the change? (Please click all that apply.) Agency Observed difficulties with achieving required field density Increased pavement permeability Other observed pavement performance problems (please specify) Other states’ issues and recommendations Recommendations from research (such as NCHRP Report 531 or other) Other AZ • CT • FL • GA • • IL • IA • • MI • PA • • • RI • VT • • WA • WI • • WY • ON • Totals 4+0 2+0 1+0 1+0 7+0 4+1 Comments: GA – 25 mm SP has been increased from 4in. to 5in. to allow one lift placement of 5 in. IL – IL identified that 19.0-mm binder mixtures would perform better with extra lift thickness of 0.5 in. As a result, 19.0-mm binder mixture minimum thickness was increased from 1.75 to 2.25 in. IA – Noted some crushing of aggregate on the surface of the lift. PA – Segregation and raveling, especially with initial Superpave mixtures being more coarse graded especially on higher-volume roadways. Asphalt industry pushing for thicker pavement layer thicknesses for easier compaction. Also, increased for less opportunity for industry complaints and claims regarding pavement issues and layer thicknesses. ON – Use of mixes with different nominal maximum aggregate sizes.

92 Impact of Asphalt Thickness on Pavement Quality 10. Does your agency use these tests or technologies for asphalt materials/placement? R = Routinely, E = Experimentally or Occasionally Agency Workability Permeability Mat Temperature Intelligent Compaction Other Factor AL E E AK AZ E AR R CA E E E CO E R E R CT E DE FL GA R E E ID E E IL E E E IN E IA E KS R KY E LA E E E ME E E MD E R MI MN E R R MS E MO E E E MT NE E NV E R NH R NJ E E NM NY E E R OH OR E E PA E E E R RI E R SC E SD TN R R TX R R UT VT E E VA R E E WA R WV WI E E E WY AB BC MB NB R E ON E Totals 0+1 R, 2+0 E 2+0 R, 8+1 E 7+0 R, 18+1 E 3+0 R, 19+0 E 7+0 R, 3+0 E Blank cells = test or technology not used or (rarely) no answer.

Tabulated State Survey Responses 93 Comments on Workability: NY – Warm Mix technology, TN – Allow WMA to be used. NB – Visual - checking, cracking, pushing, shoving. Comments on Permeability: GA – GDT-1, Measurement of Water Permeability of Compacted Asphalt Paving Mixtures. IL – IL Modified Field Permeability Test (based on NCAT Report No. 99-1 Method). LA – Falling Head, Effective Porosity. MN – NCAT Permeameter. MO – Evaluated asphalt water permeameter. NE – Early on, we performed permeability testing and its relation to in place density. VA – VTM-120, Method of Test for Measurement of Permeability of Bituminous Paving Mixtures Using a Flexible Wall Permeameter. Comments on Mat Temperature: AL – Temperature differential greater than 25° - just experimental now. AR – Require Materials Transfer Devices on all pavement operations. CO – Variance of 25°F across the width of the mat. GA – Infrared camera. ID – ITD purchased a thermal camera to evaluate mat temperature but have no requirements. IL – Infrared Thermal Imaging using MOBA PAVE-IR unit on pavers. LA – Pave IR. ME – Infrared scanner being used experimentally. MN – Paver Mounted Thermal Profile to measure surface temp. of mat behind the screed during mix placement. MO – Evaluated MOBA Pave- (IR) Infrared Scanner System. NV – Mandate use of heated material transfer device (MTV). NJ – Pilot Project. OR – Segregation. SC – Moba - on OGFC projects to check for thermal segregation and time trucking operation (paver stops). TN – Require Shuttle Buggies/MTV to be used on all mixes. TX – Test Procedure for Thermal Profile of Hot Mix Asphalt Tex-244-F. VT – Have used and currently occasionally use IR mounted equipment on paver. WA – Temperature differential using an infrared thermometer or thermal camera. Comments on Intelligent Compaction: AL – Pilot project under way. AZ – In-place voids. CA – Coverage and mat temperature. CT – Number of passes and temperature. ID – ITD hosted an Intelligent Compaction workshop but have not required Contractors to use the technology. IL – IC equipped breakdown rollers for level binder applications. LA – Pass tracking. MN – IC to continually monitor compaction effort during paving. MO – AASHTO PP 81-17, Intelligent Compaction Technology for Embankment and Asphalt Pavement Applications, using VETA software. NJ – Pilot project. NY – Pass coverage. OR – Coverage. RI – Used on gap graded friction course where density is difficult to measure. TN – Began implementation of IC – looking at roller passes, locations and temperatures. VT – Have used and currently occasionally use IC package.

94 Impact of Asphalt Thickness on Pavement Quality 11A. Have you observed contractors having increased difficulty obtaining adequate density in mixtures with certain components or in certain applications? (Please click all that apply.) Agency RA P RA S PM B G TR Ce rt ai n Bi nd er G ra de s H ig hl y A ng ul ar A gg re ga te s Ce rt ai n A gg re ga te Ty pe s Th in L ift s A t l ow b as e or m ix te m pe ra tu re W he n pl ac in g ov er co nc re te O th er AL • • • AK AZ • AR CA • • • CO • CT • • DE • FL • GA • • • ID • IL • • • • IN • • • • • IA KS • • • KY • • LA • • • • ME • • • MD • MI • MN • • • MS • MO MT • NE • • • • • • NV • • • NH NJ • NM NY • • • OH • • • • OR • • • • • • • PA • • • • RI • • • • • • • SC • • SD • • TN TX • • UT Comments on Other Factors Related to Density: CO – Minimum mix temperature at discharge and delivery. IN – Superpave 5. KS – Segregation Check Using the Nuclear Gauge (http://www.ksdot.org/Assets/wwwksdotorg/ bureaus/burConsMain/Connections/ConstManual/2018/5.8.3._Segregation_Check_Nuke_Gauge.p df). MD – Contractors use density gauges for QC in-place density, but cores are used to pay. NH – Use of material transfer vehicle wherever possible to reduce temperature and particle segregation. NY – Pavement density using cores and density gauges. PA – Material Transfer Vehicle. TX – Design of Bituminous Mixtures, Tex-204-F.

Tabulated State Survey Responses 95 Agency RA P RA S PM B G TR Ce rt ai n Bi nd er G ra de s H ig hl y A ng ul ar A gg re ga te s Ce rt ai n A gg re ga te Ty pe s Th in L ift s A t l ow b as e or m ix te m pe ra tu re W he n pl ac in g ov er co nc re te O th er VT • • • • • VA • • WA • WV WI • • WY AB • • • • • BC • MB NB • • • ON • • • Totals 13+0 5+0 12+3 2+1 5+2 10+0 3+0 12+1 18+4 3+0 12+1 Comments on Binder Grades: CA – RHMA-G mixes that use asphalt rubber binder (wet process) are harder to place and compact. NE – Highly polymerized binders. OH – 88-22, 76-22 at first. OR – PG76 binders and ER binders.... Have to get on them hot or you are done. VT – PG 76-34. AB – PG 64-28, 64-34, 70-28, etc. NB – PG 58-34, PG 70-28. Comments on Aggregate Types: MI – Higher volume mixes. OR – Unstable mixes that still meet minimum rut testing, tender mixes ... often due to aggregate source (e.g., quartz in aggregate source). VT – Natural sands. Comments on Other Factors: DE – N/A. ID – Nothing Significant. IN – High gyration mixes. KS – Dry mixes. LA – Soft subgrade. MT – ⅜-in. mixes for some contractors/sources. NV – Some WMA and temperature combinations. PA – On existing unstable base pavements. On nonuniform base pavements, on existing pavements with widening in their previous history or different cross sections. On pavements with edge deterioration or minimal shoulder width. RI – First lift of base course on subbase when fine grade is not adequate. TX – Bridge decks that prevent the use of vibratory rollers and tight areas that need hand work. VA – With HiMA mix (High Polymer Mix). WA – On bridge decks with static rolling.

96 Impact of Asphalt Thickness on Pavement Quality 11B. If yes, have you adopted any strategies to address these issues? AZ – None. CA – Contractor option to use WMA technologies. CO – CDOT developed a thin lift density specification. FL – Contractors have expressed concerns with 1.0-in. lifts. The data indicate that they can achieve density on these lifts, but may struggle a little more in cooler months. Based on industry concerns, FDOT does not allow vertical vibratory compaction on 1.0-in. lifts and has lowered the target density to 92% Gmm. GA – On 9.5-mm SP Type II, we added #7 stone to coarsen up the middle. The #7s added more intermediate stone to stable the mix and create a less tender mix that is more prone to compact. Concerning RAP, we instituted a corrected optimum asphalt content. IL – Adjusted temperature requirements for polymer-modified mixtures. Allow oscillatory roller use in certain applications. IN – We removed our 125 Ndes gyration mixtures. Now 75 or 100, depending on ESAL category. KS – KDOT is not specifying 9/125/205 revolution mixes on high-volume routes with a 20-year design lane traffic of greater than 30 million ESALs; KDOT is specifying 8/100/160 revolution mixes on these routes. There have been issues with compaction on high RAP mixes (greater than 40%), so RAP is now limited to 15%, 25%, or in some instances 40% maximum. LA – It is the contractor’s responsibility to bid and build the roadway to specification. LADOTD does not tell the contractor how to build the road. ME – Using WMA for compaction aid. MD – We developed the thin lift specification (please refer to the link below in section 504.03.13) https://policymanual.mdot.maryland.gov/mediawiki/index.php?title=504_ASPHALT_PAVEMENT MI – N/A. MN – No strategies. NE – Using WMA additives as a compaction aid. NV – Strict enforcement of mix composition (adequate virgin binder content), enforce minimum temperature requirements by binder grade, and enforce max. temp. drop from plant discharge to paver of 20°F (401.02.02). NY – Increase workability for angular aggregates and use WMA technology and increase temperatures for HMA. OH – Contractors figured out most of the issues. OR – Hit the mix when it is hot with the rollers ... tandem rolling ... staying off of the mix in the tender zone, trying to reduce mix with quartz and other slick aggregates in the stockpile, warm mix technology ... sometimes used in hot mix applications (e.g., foaming hot mix). PA – Specify 100% use of WMA. For WMA by mechanical foaming, further limit the minimum mixture temperature compared to minimum mixture temperatures for chemical or organic WMA technologies. Restrict paving season or calendar dates for Wearing Courses specified with higher design life ESALs (≥10 million) and/or specified with polymer modified asphalt binders. Unstable or nonuniform pavements are specified with lower density requirements for acceptance by pavement cores (i.e., what we call Standard construction) or specified with density acceptance by optimum roller pattern or nonmovement under the roller. Specified Material Transfer Vehicle (MTV) for better mixture uniformity (both gradation and temperature). Also, piloting e-ticketing between asphalt mixture plant, haul trucks, and project sites to improve coordination of paving operations (initially seems to help identify issues or better track operations to review for issues). RI – The first lift on soil only requires 92% of TMD. SC – Limit RAP/Contractor choice to use RAP if seeing compaction issues dealing with excess stiffness. SD – RAP design procedure modified to fewer gyrations. VT – Design and field strategies. VA – Instituted min base and ambient temps of 50°F and rising for SMA mixes. WA – Using smaller NMAS mixes, higher density requirements, requiring tarped loads, warm mix, no RAP, pneumatic rollers. WI – Many of the issues have gone away with regressed air voids (design to 4.0% AV, add virgin AC to 3.0%). AB – We no longer use GTR. Penalties for failing to achieve target density are smaller for thin lifts compared to regular thickness lifts. BC – Our EPS specs allow us to penalize for mixes that don't meet spec, and if they are far enough out of spec, they are rejected. NB – Meetings with contractors. Evaluating different methods for evaluating density within a lot. ON – Compaction aids and Warm mix additives are permitted. Have been using Asphalt Multi -Integrated Roller (AMIR) on bridge decks.

Tabulated State Survey Responses 97 12. Does your agency allow the use of warm mix asphalt technologies at conventional temperatures as a compaction aid? Agency Yes No Permissive spec or not monitored If yes, does the use of WMA as a compaction aid seem to improve the ability to get density? Always Frequently Sometimes Never AL • AK AZ • • AR • CA • CO CT • • DE • • FL • • GA ID • IL • • IN • IA • • KS • • KY • LA • ME • • MD • • MI • • MN • • MS • • MO • MT • • NE • • NV • • NH • • NJ • NM NY • OH • OR • PA • • RI • • SC • • SD • • TN • • TX • • UT • • VT • • VA • • (continued on next page)

98 Impact of Asphalt Thickness on Pavement Quality Agency Yes No Permissive spec or not monitored If yes, does the use of WMA as a compaction aid seem to improve the ability to get density? Always Frequently Sometimes Never WA • WV WI • • WY • AB • BC • • MB NB • • ON • Totals 32+2 0+0 10+2 2+0 11+0 13+2 0+0 Comments: ID – Contractors achieve density. Not sure if it is all due to WMA. MN – Contractors have sometimes mentioned that the specified lift thickness is too thin to adequately densify the pavement. MT – Our lift thicknesses can cause difficulty achieving optimum compaction; however, the desire to earn incentives based on ride quality often trumps the problems of inadequate density. OH – More lift thickness certainly helps density but economics drives thickness for us. OR – Our experience has been that the nationally recommended lift minimums and maximums hold true for the mixes in our state, for the most part. We have done informal research on 4-in. lifts placed in a slot by taking cores and verifying that the density profile is consistent throughout the lift. I believe Oregon DOT switched to Superpave in the late 1990s, when I was still in college, so I am unaware of what transition pains took place in achieving density when the change was made. I know at some point we switched from a target density as a percentage of maximum achieved in the control strip. RI – I’ve always been of the opinion that smaller is better when it comes to NMAS and thicker is better for lift thicknesses. But what are reasonable (cost-effective?) limits for each of these parameters? Feel free to contact me. Good survey. TN – Issues with density when first considering implementing Superpave due to high gyration levels and low A/C content. Generally not an issue with our current Marshall designs and mix design requirements. VT – Would be interested in thoughts on any differences between Contractor mix designs vs Agency mix designs. Would be interested in thoughts on balanced mix designs (or performance-related specifications) on any perceived or real effects on field compaction. VA – How much we can go up for the max lift thickness (especially for thin lays). Some studies show increasing layer thickness OK, though. WI – 0092-15-09 & WHRP 03-02 are reports related to the subject. BC – We have made slight adjustments to our mix specs over the years that have addressed most of our concerns and allowed us to place thin lifts (37.5 to 40 mm); we only use Marshall mix design methods and have moved away from Superpave after less-successful projects in the early 2000s. These have included adjusting target air voids in the colder regions to 2.5% while reducing the NMAS of our medium mix everywhere to 16 mm. In general, we have received good performance from these mixes and compaction and segregation concerns have been reduced to only very occasional problems.

Tabulated State Survey Responses 99 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.) A ge nc y In cr ea se d Ru tti ng In cr ea se d Cr ac ki ng In cr ea se d Pe rm ea bi lit y D ec re as ed D ur ab ili ty Sh or te ne d Se rv ic e Li fe In cr ea se d M ai nt en an ce O th er AL • • • • AK AZ • • • • • AR • • • CA • • • CO • CT • • • • • DE • FL • GA • • • • • • ID IL • • • • • IN • • • • IA • • KS • • • • KY • • • • LA • • • • • ME • • • MD • MI • • • • • MN • • • • • MS • • • MO • • • • MT • • • • NE • • NV • • • NH • • • • • NJ • • NM NY • • • • • OH • • • • • OR • • • • • • • PA • • • • • • RI • • • SC • • • SD • • • • TN • • • • TX • • • VT • • • • • • VA • • • • • WA • • • • • WV WI • • • • • WY • • • AB • • • • BC • • • • MB NB • • • • ON • • • • • Totals 4+0 23+1 23+4 31+4 32+4 28+4 13+0 UT

100 Impact of Asphalt Thickness on Pavement Quality Comments: CO – CDOT has not studied this issue. DE – N/A. FL – Visually segregated areas with low density have raveled prematurely. FDOT instituted a segregation specification to address this issue. IA – Permeability around longitudinal joints. MD – Raveling due to end of load segregation. We did not measure any other performance measure related with density. NV – Increase reveling and fatigue cracking, loss of durability. NH – Listed items are mainly related to thin lifts on maintenance overlay program. OR – Early raveling. PA – Increased longitudinal pavement joint deterioration. TN – Raveling, longitudinal joint failures. VT – Routinely follow with preventive maintenance project (typically bonded wearing course). WA – Raveling. 14. Has your agency conducted or sponsored any research related to asphalt pavement density and lift thickness (currently or in the past)? Yes [10+1] AL, AZ, CO, FL, ID, IL, MS, TN, TX, WI, ON Planning/Considering [7+0] IN, KY, LA, MO, NE, NJ, RI No [16+2] AR, CT, DE, GA, ME, MI, MN, NH, NY, OH, SC, SD, VT, VA, WA, WY, AB, NB Unsure [9+1] CA, IA, KS, MD, MT, NV, OR, PA, UT, BC Comments: AL – Long time back with NCAT - I don’t have the reference but will try to locate if needed. The work may not have been directly for us but national. AZ – Upcoming Test Section on Enhanced Durability of Asphalt Pavements through Increased In-Place Pavement Density. CO – Increased Density performance through NCAT and FHWA. Our contact is Tim Aschenbrener. FL – It is actually upcoming at the next NCAT Test Track to be constructed this summer (density variability study). We have also done some work at our HVS test track. The contact is Wayne Allick or Bouzid Choubane. ID – ITD did a research project on nonnuclear density gauges. IL – IL participates in the National Road Research Alliance (NRRA) research efforts. MI – Research performed by Burns Cooley Dennis in October 2009, “Evaluation of Hot Mix Asphalt (HMA) Lift Thickness.” TN – FHWA Enhanced Durability through Increased In-Place Density test section this spring/summer. TX – https://library.ctr.utexas.edu/Presto/content/AdvancedSearch.aspx?ctID=OWE3NjYzNTktYzJmNC0 0ZTAwLThmMjItYzhmNzNiYTFmNzdh. WI – http://wisconsindot.gov/Pages/about-wisdot/research/flex-pave.aspx.

Tabulated State Survey Responses 101 15. Do you see a need for additional research into any of the following? (Please click all that apply.) Agency Field validation of t/NMAS Means of improving mix compactibility Means of achieving adequate mat density Improved compaction tests or technologies Effects of mixture properties on compactibility Other AL • • AK AZ • • • AR • • CA • • CO • • CT • DE • FL GA • • ID • IL • • • • IN • • • IA KS • • KY • LA • • • ME • MD • • MI • MN • • • • • MS • • MO • • • MT NE • • • • NV • • • NH NJ • • NM NY • OH • • OR • • • • PA • • • • • RI • • • • • SC • SD • TN • • TX • • • UT • VT • • • • • • WA • • • • • WV WI • • WY • • AB • • BC MB NB • • ON • • • Totals 12+0 13+0 16+2 23+2 26+1 6+2 VA • • • •

102 Impact of Asphalt Thickness on Pavement Quality Comments: DE – N/A. GA – New equipment like lightweight deflectometer. ID – Nonnuclear density options. MD – Maryland does not have many problems in achieving the densities desired. PA – Research to improve efficiency of using newer IC tools (i.e., real-time data analysis). VT – All of the above simply for validation or for a means of improvement. AB – Methods to determine uniformity of compaction (longitudinally and transversely). ON – Improved test method to measure reduced surface permeability. 16. If you have any additional thoughts or information on your organization’s 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. OH – More lift thickness certainly helps density but economics drives thickness for us. OR – Our experience has been that the nationally recommended lift minimums and maximums hold true for the mixes in our state, for the most part. We have done informal research on 4-in. lifts placed in a slot by taking cores and verifying that the density profile is consistent throughout the lift. You may contact me in the future. I believe Oregon DOT switched to Superpave in the late 1990s, when I was still in college, so I am unaware of what transition pains took place in achieving density when the change was made. I know at some point we switched from a target density as a percentage of maximum achieved in the control strip. MN – Contractors have sometimes mentioned that the specified lift thickness is too thin to adequately densify the pavement. MT – Our lift thicknesses can cause difficulty achieving optimum compaction; however, the desire to earn incentives based on ride quality often trumps the problems of inadequate density. RI – I've always been of the opinion that smaller is better when it comes to NMAS and thicker is better for lift thicknesses. But what are reasonable (cost-effective?) limits for each of these parameters? Feel free to contact me. Good survey. TN – Issues with density when first considering implementing Superpave due to high gyration levels and low A/C content. Generally not an issue with our current Marshall designs and mix design requirements. VA – How much we can go up for the max lift thickness (especially for thin lays). Some studies show increasing layer thickness OK, though. VT – Would be interested in thoughts on any differences between contractor mix designs vs agency mix designs. Would be interested in thoughts on balanced mix designs (or performance-related specifications) on any perceived or real effects on field compaction. WI – 0092-15-09 and WHRP 03-02 are reports related to the subject. Feel free to follow up with other questions. BC – We have made slight adjustments to our mix specs over the years that have addressed most of our concerns and allowed us to place thin lifts (37.5 to 40 mm); we only use Marshall mix design methods and have moved away from Superpave after less-successful projects in the early 2000s. These have included adjusting target air voids in the colder regions to 2.5% while reducing the NMAS of our medium mix everywhere to 16 mm. In general, we have received good performance from these mixes and compaction and segregation concerns have been reduced to only very occasional problems.

Next: Appendix D - Tabulated Industry Survey Responses »
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TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 537: Impact of Asphalt Thickness on Pavement Quality documents transportation agency policy for lift thickness and minimum compaction requirements on resultant asphalt pavement quality.

To achieve expected pavement performance, it is important that asphalt concrete (AC) have adequate density. A critical factor in achieving this density is the ratio of lift thickness to nominal maximum aggregate size (t/NMAS).

The information in the report is designed to help make agencies aware of a range of practices other agencies use to achieve a desired t/NMAS ratio, ensuring that density of AC is adequate to meet expected pavement performance.

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