1. Micro-milling The Economics A Rehabilitative Strategy for Savings Presented By: Sheila Hines Georgia Department of Transportation

2. Talking Points GDOT rationale for micromilling Specification Development and Verification Projects and Economics Conclusions

3. GDOT Rationale for Micro-milling

4. Standard Pavement Structure for Interstates 12.5 mm SMA PFC

5. Micro-milling Specification Development and Verification The Key Points

6. Rough Milling VS Micro Milling Rough Milling Ridge-to-ridge pitch ~ 25 mm Ridge-to-valley Depth ~ 10 mm Micro Milling Ridge-to-ridge pitch ~ 9 mm Ridge-to-valley Depth ~ 3 mm

7. Section 432: Mill Asphaltic Concrete Pavement (Micromill) Specification The use of the micromilled pavement as a temporary riding surface shall be for a maximum of ___ days Difference between ridge and valley of the mat surface shall not exceed 1/16 in (1.6 mm) Target, 1/8 in (3.2 mm) Correction 1000 ft. test section Laser Road Profiler acceptance testing measured indices must meet 0f 825 mm/km Target, 900 mm/km Correction *Conventional milling must meet Laser Road Profiler acceptance testing me measured indices 0f 1025 mm/km Target and 1175 mm/km Correction on interstates

8. Verification Objectives Verify specification for micro-milled surface texture in order to meet short- and long-term performance requirements Confirm that requirements can be determined via routine quality acceptance procedures Confirm that requirements are achievable and that benefits of micro-milling are cost- effective using current technology

9. Verification Approach Select appropriate instruments for measuring ridge-to-valley (RVD) milled surface texture depths Measure milled surface texture depths in 8 test sections Analyze data to determine compliance with RVD specifications Evaluate performance of PEM overlay on micro- milled surface

10. First Project -Specification Verification I-75 Near Perry Georgia

11. I-75 Near Perry Georgia 12.5 mm OGFC Surface Mix 15 years +

12. Severe Testing Using APA Under Water @ 64º C Existing OGFC Removed and Testing Performed on Underlying Dense- Graded Surface Mix

13. Ultra Light Inertia Profiler (ULIP) and Circular Track Meter (CTM) 150 ft

14. RVD Data Provided by ULIP (I) ULIP measured surface texture depth at 0.5 mm intervals and with 0.01 mm accuracy Base length unit (100 mm) selected, and maximum RVD within base length unit captured by software 450 RVD values collected for each 150-ft. measurement run

16. Typical Micromilled Surface Profile (100 mm base length) 2.1 mm

17. RVD Results from ULIP Section ID Mean Profile Depth (mm) RVD Data, mm Meanp90p95 Conventional Milling3.355.175.80 S1-10.912.243.904.41 S2-20.320.841.341.58 S3*-1.622.542.98 S4-1* - 1.772.823.27 S4-2* - 1.732.733.19 S5-10.661.872.893.30 S5-20.681.923.023.47 S60.611.632.412.78 S70.681.892.933.33 S80.611.622.522.87

18. Estimation of Maximum RVD Values Section ID Maximum Direction Ratio From CTM Estimated Maximum RVD, mm Meanp90p95 C (1)1.444.847.448.35 S1-11.312.935.115.78 S2-21.251.051.681.98 S3 (2)1.452.353.684.32 S4-1 (2)1.111.963.133.63 S4-2 (2)1.192.063.253.80 S5-11.452.714.194.79 S5-21.262.423.814.37 S61.302.123.133.61 S71.112.103.253.70 S81.061.722.673.04

19. Laser Road Profiler

20. I-75 The Economics Project Let April 2007 o Original Estimated Rehabilitation Cost $70 million Project Completed December 31, 2007 o Final Payment Statement $8.1 million GDOT projected savings $3.1million per year over 20 year design life  Currently $ 21.7 million savings

22. I-95 Near I-16

23. Micromilled Surfaces on I-95

24. Mean RVD & IRI for Each Lane: I-95 Project LaneNB1SB1NB2SB2NB3SB3 Mean RVD, mm Average2.62.42.62.32.42.2 High3.43.2 3.02.6 Low1.8 2.01.72.01.8 IRI, mm/km Average602515588555644633 High724742781719842753 Low498383494443472512

25. I-95 – The Economics Project Let February 2009 o Original Estimated Rehabilitation Cost $31.3 million Project Completed May 2011 o Final Payment Statement $ 11.8 million GDOT projected savings $975,000 per year over 20 year design life  Currently $ 3.4 million savings

27. I-285 Project

28. Run Type Final State Route Contract ID B34041-11-000-0 Total Lane Miles 28.0 Project limits 6.430 miles of milling, inlay and plant mix resurfacing on I-285/SR 407. Beginning at Ashford Dunwoody RD. Contractor E.R. Snell Contractor, Inc. PROJECT AVERAGES Mix OGFC Preconst.NewResurface Contractor Code: 2SN250 Spec. Target 750 Spec. Corrective 825 MTV % Change Test Limits Direct. M/F Direct. M/F Direct. M/F Direct. M/F East West FromToLane1Tar.Corr.DateLane2Tar.Corr.DateLane1Tar.Corr.DateLane2Tar.Corr.Date 0.01.0464MM7/24/10496MM8/7/11434MM7/24/10418MM7/31/11 1.02.0456MM7/24/10454MM8/7/11439MM7/24/10409MM7/31/11 2.03.0497MM7/24/10482MM8/7/11547MM7/24/10450MM7/31/11 3.04.0535MM7/24/10606MM8/7/11520MM7/24/10446MM7/31/11 4.05.0515MM7/24/10638MM8/7/11478MM7/24/10448MM7/31/11 5.06.0472MM7/24/10534MM8/7/11528MM7/24/10444MM7/31/11 6.07.0522MM7/24/10616MM8/7/11478MM7/24/10456MM7/31/11 M = MEETS F = FAILS SI = SMOOTHNESS INDEX

30. 64.3 Lane Miles 1 Mile Section Failed to Meet 3.2 mm Correction Tolerance Severe Cracking Observed in Milled Area

31. I-285 – The Economics Project Let April 2011 o Original Estimated Rehabilitation Cost $32 million Project Completed December 31, 2011 o Final Payment Statement $12.2 million GDOT projected savings $990,000 per year over 20 year design life  Currently $ 2.97 million savings

33. SR 400 Dawson County

34. SR 400 DAWSON/FORSYTH COUNTIES MICRO MILLING PROJECT Mile Post36.1-36.636.6-37.037.0-37.537.5-38.038.0-38.538.5-39.039.0-39.539.5-40.040.0-40.540.5-41.041.0-41.541.5-42.042.0-42.542.5-43.043.0-43.543.5-44.044.0-44.544.5-44.7 NB LN 1 OGFC IRI448417468451565422538470526488 M MILL IRI991724908979639788732835962730638625765807688981758849 M MiILL RVD3.02.93.0 3.13.22.83.12.42.12.52.61.62.83.32.62.51.6 NB LN 2 OGFC IRI414415424452444441418409 M MILL IRI633558633815687837772778614766800877854702630769768876 M MILL RVD3.01.63.23.12.7 3.03.53.42.9 2.21.82.93.22.70.8 Mile Post36.1-36.636.6-37.037.0-37.537.5-38.038.0-38.538.5-39.039.0-39.539.5-40.040.0-40.540.5-41.041.0-41.541.5-42.042.0-42.542.5-43.043.0-43.543.5-44.044.0-44.544.5-44.7 SB LN 1 OGFC IRI449481626473506461548591505458 M MILL IRI779669880859733896651854756679860933687847786763805804 M MILL RVD2.2 2.52.42.12.02.12.72.02.22.52.62.22.52.32.52.32.1 SB LN 2 OGFC IRI460474480486526449473482525457 M MILL IRI679761777853759580590774721742519564600631920723553681 M MILL RVD2.03.83.53.42.12.8 2.72.93.03.22.92.11.83.03.1 2.5

35. SR 400 – The Economics Project Let June 2012 Project Completed November 2012 o Final Payment Statement $3.6 million

37. Conclusions Three projects have verified Specifications o One project (SR 400) has displayed early raveling Micro-milling provides a smooth textured platform for new drainage course Careful project selection is necessary to assure successful micro-milling outcomes Savings associated with micro-milling have resulted in a change of business practice for GDOT o Interstate projects now let with anticipated future micro-milling Mica schist—Materials defined in ASTM C 294 as phyllite or schist. Use GDT 104 to analyze these materials. (Use this requirement for Interstate Construction, SMA mixes, OGFC mixes and all surface mixes on roadways ≥ 25,000 ADT).

38. Questions Sheila Hines State Bituminous Construction Engineer Georgia Department of Transportation (404) 608-4856 shines@dot.ga.gov