SW Chapter Minnesota Society of Professional Engineers

1. SW Chapter Minnesota Society of Professional Engineers Bituminous Topics Presenter – Joe Thomas, P.E.

2. Will cover today…. • Bituminous Unit personnel • From the Audit Director • Asphalt Binder Prices • Specification items/changes • Special Provisions • Preliminary PG xx-34 report • Ride update • For the future • Warm Mix Asphalt • Intelligent Compaction on HMA

3. MnDOT Bituminous Unit Personnel • John Garrity 651-366-5577 • Joe Thomas 651-366-5464 • Greg Johnson 651-366-5497 • Dave Linell 651-366-5459 • Bituminous Lab • Ray Betts 651-366-5469 • Lynnette Nadeau 651-366-5468

4. From the Audit Director

5. Asphalt Binder Prices

6. 2008 Bituminous Specification • The 2005 Specification Book does not contain the most current Bituminous Specification. • Designers should insert most current specification by special provision or reference the most current 2008 specification. • www.mrr.dot.state.mn.us/pavement/bituminous/bituminous.asp

7. -Minimum allowable lift thickness. -Magnesium sulfate soundness. -Mix design review clarification. -Mixture aggregate requirements. -Minimum add binder/total binder requirement for mixtures with RAP/shingles. -Gyration requirement changes. -Mix design documentation section rearrangement. 2008 Specification Changes

8. 2008 Specification Changes -Laboratory and calibration requirements. -Production aggregate specific gravity testing. -Asphalt binder sample testing clarification. -JMF adjustment request modification. -Air Void penalty change -Small quantity paving clarification. -Basis of Payment Change

9. Minimum Allowable Lift Thickness Gradation Aggregate Minimum DesignationSize Lift thickness 5* (-3/8”) 1/2 inch A, 4* (-1/2”) 1 inch B, 3* (-3/4”) 1 ½ inch C, 2* (-1”) 2 ½ inch * Marshall Designation

10. The magnesium sulfate soundness loss at 5 cycles on the coarse aggregate fraction (material retained on the 4.75 mm [#4]) shall not exceed the following for any individual source used within the mix: * a) No more than 14 % loss on the 19 mm [3/4 inch] to 12.5 mm [1/2 inch] and larger fractions. b) No more than 18% loss on the 12.5 mm [1/2 inch] to 9.5 mm [3/8 inch] fraction. c) No more than 23% loss on the 9.5 mm [3/8 inch] to 4.75 mm [#4] fraction. d) No more than 18% for the composite loss. (Applies only if all three size fractions are tested). New Wording: Coarse aggregate that exceeds the requirements listed above shall not be processed for use as minus 4.75 mm [#4] material. Old Wording: An aggregate proportion which passes the 4.75 mm [#4] sieve and exceeds the requirements listed above on the coarse aggregate fraction is prohibited from use in the mixture. Magnesium Sulfate Soundness

11. Mix Design Review -clarification • Clarification regarding where to send mix designs. • Review of mixture designs will be performed in the District Materials Laboratory where the Project is located.

12. Mixture Aggregate Requirements

13. RAP/Shingle Mixes • Table 2360.3‑B2a --Mixture Aggregate Requirements Traffic Level 4 & 5 mixtures • When shingles are included as part of the allowable RAP percentage the ratio of added new asphalt binder to total asphalt binder shall be 70% or greater ((added binder/total binder) x 100 >= 70). • A minimum of 1 spotcheck per day per mixture blend is required to determine new added binder.

14. Design Gyrations • Nmax vs. Ndes • Back calculate to Ndes • NCAT and FHWA recommend gyrating to Ndes.

15. Gyratory Mixture Requirements • Mixtures will be gyrated to Ndes • No longer gyrate to Nmax and back calculate to Ndes. • Mix Design Report adjustments will be handled by request for JMF change. • In most cases, redesign not necessary.

16. Laboratory Requirements • Records of calibration for each piece of testing equipment shall be kept in the same facility as the equipment.

17. Aggregate Specific Gravity • At the discretion of the District Materials Engineer, aggregate stockpiles will be sampled and tested to verify aggregate specific gravity.

18. Asphalt Binder Sampling • Included the following language: Contact the Chemical Laboratory (Jim McGraw; 651-366-5548) for disposition of failing asphalt binder samples.

19. JMF Request for Adjustment • Unless otherwise authorized by the District Materials Engineer, no adjustments are allowed using aggregates or materials not part of the original mix design.

20. Payment Schedule for Individual Test Results

21. Payment Schedule for Moving Average Test Results

22. Small Quantity HMA Paving • The Department will obtain samples, as determined by the Engineer, to verify mixture requirements of Table 2360.3‑B2a and Table 2360.3-B2b .

23. Basis of Payment • Specification provided for reduced payment of mixture when density > 160 lb/ft3. • Change: • Apply reduced payment only when mixture includes steel slag as one of the aggregate proportions.

24. Confusion about 2360 ?? • Need Help, Contact: • State-Aid • District Materials • Bituminous Unit

25. Special Provisions • The best way to do something is yet to be found. – “UDOT” The only thing that is constant is change!

26. MnDOT Special Provisions for 2008 • Asphalt Film Thickness - Required • Pavement Density Modification - Required • Tack Coat - Required • Mixture Sampling Modification - Optional

27. Asphalt Film Thickness • AFT is a calculation – not a test • Is to be included as a Standard Provision for use on all 2008 MnDOT Projects. • Very likely, AFT will be included in local government (County) projects in 2009.

28. Asphalt Film Thickness • Why AFT? • VMA does not ensure adequate film thickness. • F/A is a design consideration only and there is not necessarily a correlation between F/A and AFT.

29. Why AFT? • The minimum VMA requirement is based on the maximum aggregate size • There is little correlation between the maximum aggregate size and overall gradation, or aggregate surface area (SA)

30. Some Methods to Increase AFT: • Reduce the % passing the #30, #50, #100 and/or #200 sieves • Increase the amount of crushed material • Waste the baghouse fines • Completely redesign the mixture

31. AFT – Quality Assurance Change • The allowable tolerance between the Contractor and Mn/DOT test result for the #200 sieve is 1.2% (instead of 1.5%).

32. AFT – Gradation/Tolerance Issues • Accurate gradation is critical to determining surface area. • AFT = effective asphalt volume/aggregate surface area • Laboratory Manual test standard for gradation is to “hand wash” sample. • When there are tolerance issues between agency and industry gradation: • MnDOT will verify gradation through hand wash.

33. Pavement Density - Special Provision • Will be standard on all MnDOT projects in 2008. • Replaces entire section of 2360.6 Pavement Density in the specification • Provision Purpose: Improve density at joints and increase randomness of core testing. • Evaluate density at longitudinal joint. • Obtain companion cores for every density core. • Use new criteria to compare core tolerances between agency and industry.

34. Pavement Density Provision • Longitudinal Joint Requirements: • In approx. 1 density lot/day evaluate both mat density and longitudinal joint density. • For joint cores, cut cores on right and left side of the mat within 6 inches from the edge of the top of the mat. • Engineer will randomly determine, at the end of the day, which lot(s) will be evaluated for LJ density. • Minimum joint density requirements are reduced depending on confined vs. unconfined joints. • Mat Density Modification: • No cores taken within 12 inches of longitudinal joint. • Combined Pay Factor for Density

35. “Black Gold” Bituminous Cores

36. General Know the allowable tolerance between the Contractor and Mn/DOT test results. Look for “trends”, in addition to just the allowable tolerance.

37. Contractor vs. Agency Companion Core Gmb Results Anytime the Gmb difference between companion cores is 0.050, or greater, something is wrong. Either one of the cores was damaged, the cores were not companions, or someone made an error in the testing or computations. If this occurs, the problem should be brought to the attention of the Project Engineer, investigated, and recoring may be necessary.

38. Probability

39. What is the probability of drawing four diamonds with replacement? 1 out of 256 times

40. Chance of Occurrence vs. Z-Score

41. Pavement Density Special Provision • Companion Core Requirements • Requires Agency companion cores for every Contractor density core. • Total 4 cores taken in lots where only mat density is evaluated. • Total 8 cores taken in lots where mat density and longitudinal joint density evaluated. • Density Core Testing Requirements • MnDOT will, typically, select one of the two Agency companion cores per lot to be tested. • However, MnDOT may elect to test all companions to provide a direct verification of all individual and daily average test results

43. Increasing stationing

44. Core Tolerances • Two tolerance comparisons required: • 1) Compare individual core bulk specific gravities for Agency and Contractor. • 2) Compare the days’ average core bulk specific gravities for Agency and Contractor cores.

45. Core Tolerances (first comparison) • Individual Core Comparison (1): • 1) Compare individual core bulk specific gravities for Agency and Contractor. Tolerance for individual cores is 0.030. • If the tolerance is exceeded, the Agency’s result will be substituted for the Contractor’s result.

46. Core Tolerances (second comparison) Days’ Average Core Tolerances: • Compare the days’ average core bulk specific gravities for Agency and Industry cores. • For those tests that meet the 0.030 tolerance, compare the average of the Contractor specific gravities with the average of the Agency specific gravities. • Tolerance will be variable depending on how many samples are compared. • Tolerance equals 0.030 divided by the square root of the number of samples compared (0.030/√n) • If this tolerance is exceeded, all the Agency’s test results will be substituted for the Contractor’s results for that day’s paving. See handout

47. EXAMPLE CORE SUBSTITION* Per special provision – Pavement Density Modification for Construction Season 2008 Prepared by: T. Nordstrom/J. Thomas, 3/14/2008 • This example does not apply when there is a failing individual bulk SpG tolerance(s) test between the contractor and Mn/DOT. • The allowable individual SpG test tolerance between the contractor’s core and Mn/DOT’s companion core is 0.030. • Per the special provision, the allowable tolerance for more than one test is: 0.030 / n ½ • .030 / 41/2 =0.015 • Contractor Average Bulk SpG is 2.239 • Mn/DOT Average Bulk SpG is 2.223 • 2.239 – 2.223 = 0.016 • 0.016 > 0.015 ; which is a failure and the contractor’s bulk SpG’s values shall be substituted with Mn/DOT’s bulk SpG’s values

48. Tack Coat Soon to be addressed in a Tech Memo • 2357 Tack Coat Specification has been updated. • Tack will be an incidental item on most MnDOT Contracts in the 2008 construction season (pilot provision). • Application rates included in provision for: • Undiluted tack and, • Diluted tack (diluted at asphalt supplier 1 part emulsion to 1 part water) • RC’s not allowed

49. Mixture Sampling Modification Purpose: Increase randomness of mixture testing. Optional provision on MnDOT Contracts for 2008 Piloted last year in: District 2 – Bemidji District 7 – Mankato

50. Mixture Sampling Provision Provision Requirements: • Field Inspector immediately retains possession of the Department portion of each split sample (QC/QA). • At the end of the day, the Field Inspector will randomly submit a minimum of one sample, on a daily basis, to the District Laboratory for Verification testing.