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Higher RAP Mixes in New Jersey

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Higher RAP Mixes in New Jersey

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    1. Higher RAP Mixes in New Jersey – Changes in Mix Design and Production Thomas Bennert Rutgers University

    3. Fatigue Cracking Potential

    4. Increased Potential for Fatigue Cracking Rutgers tested 14 different mixes containing various RAP contents 3 different suppliers 3 different nominal aggregate sizes Fatigue cracking tests indicate in all cases, the addition of RAP increased fatigue cracking potential of the mix

    5. Overlay Tester

    6. Overlay Tester Results (NJDOT B-10 Procedure)

    7. Average Results for Overlay Tester (NJDOT B-10 Procedure) 0% RAP = 138 cycles 15% RAP = 40 cycles 20% RAP = 38 cycles 25% RAP = 40 cycles 30% RAP = 24 cycles (only 1 mix – 19mm) Laboratory results similar to national trends (NCAT LTPP Study, 2009)

    8. SPS-5 Project Locations

    9. NCAT LTPP SPS-5 RAP Study

    10. NJ SPS-5 Cracking – 2 Inch Overlay Section (Milled)

    11. NJ SPS-5 Cracking – 2 Inch Overlay Section (No Mill)

    12. NJ SPS-5 Cracking – 5 Inch Overlay Section (No Mill)

    13. Need for Determining “Actual” AC% of RAP

    14. Determining “Actual” AC% of RAP Common to assume or use the ignition oven to determine AC% of RAP Issue: what correction factor to use if ignition oven used? Should I use same correction factor as my virgin aggregates? To accurately determine, extraction required!

    15. Total Binder Content of RAP Mix Wrong determination of RAP AC% resulting in an under-asphalted mixture

    16. Collected PANYNJ Data – RAP AC% Extracted Ignition Difference Plant #1 5.75% 6.99% -1.24% Plant #2 4.62% 5.31% -0.69% Plant #3 5.27% 6.17% -0.90% Plant #4 4.38% 5.46% -1.08% Plant #5 5.43% 6.25% -0.82% Average = -0.88%

    17. Increased Stiffness of RAP Binders

    18. Increased Stiffness of RAP Binders The aged RAP binder significantly stiffer than commonly used binders in NJ Examples: Tilcon, Oxford Plant: PG94-10 Weldon: PG94-04 Therefore, if RAP binder is blending with virgin binders (i.e. – PG64-22 or PG76-22), it is obvious that both the high PG grade and low temperature PG of the resultant (blended) asphalt binder will change High temp PG increased (OK for rutting) Low temp PG increased (not good for intermediate and low temperature cracking!)

    19. Reasons for Poorer Performance with Higher RAP Lack of blending between RAP binder and virgin binder Results in lower effective binder contents Not knowing exact AC% of RAP for use in asphalt binder calculations and ignition oven correction factors Results in lower effective binder contents Increased stiffness of RAP binder Decrease in in-place compacted air voids

    20. NJDOT Five Higher RAP Pilot Projects in 2009

    21. Five Higher RAP Pilot Project Summary Rt 206 – production and construction data met specifications Now holding water I-80 – issues with volumetrics throughout first half of project I-78 – compaction issues resulted in high in-place air voids and poor ride South Jersey Maintenance Roadway Repair Contract (#1) Could not get mix verified through plant South Jersey Maintenance Roadway Repair Contract (#2) Only project not to report issues

    22. NJDOT Procedure for Using Higher RAP Percentages

    23. NJDOT Procedure for Using Higher RAP Percentages Main Goal: To achieve RAP mixtures that provide equal to (or better) performance than virgin asphalt mixtures Procedure developed to resolve: Lower effective asphalt contents High stiffness of RAP binders Poor compactability of RAP mixes

    24. Step 1. Determine Variability of RAP Stockpile Variability of aggregate gradation and asphalt content Min. stockpile size is amount required for one week production Obtain 10 samples Calculate standard deviation for gradation and AC% Utilize HMA Tools Excel Spreadsheet to determine allowable RAP % (based on variability) Four “Tabs” in spreadsheet that must be filled in

    25. HMA Tools – RAP Variability

    26. HMA Tools – RAP Binders

    27. HMA Tools – RAP Aggregates

    28. HMA Tools – Blended Binders

    29. Where to Download HMA Tools http://www.abatech.com/NCHRP933Info.htm http://lazerpro.com/projects/advanced-asphalt/manual/

    30. Step 1. Continued Obtain Letter of Concurrence from contractor accepting high RAP Send letter and RAP stockpile results to Regional Materials Engineer, with a copy to Regional Construction Engineer, Resident Engineer, and Eileen Sheehy (Manager of Bureau of Materials)

    31. Step 2. Dropping Gyration Level Supplier agrees to provide 75 gyration (M) mixture when 100 gyration (H) is specified

    32. 3. Determination of New Ignition Oven Correction Factor RAP binder and aggregate gradation initially needs to be determined by extraction and recovery Ignition oven allowed for use after NJDOT approved determined correction factor Use 5 split samples from Step 1 Correction factor for final mix with RAP calculated upon RAP and virgin material

    33. Step 4. RAP Binder Credit Research indicates not all of RAP binder mobilized and blending with virgin binder 50 to 80% blends with virgin binder, remainder is “Black Rock” Actual degree of blending is production, RAP source, time at elevated temperature dependent 50% available RAP binder is being used as a “starting point” during first year of implementation APA and Overlay Tester will be used for final acceptance of higher RAP mixture

    34. Step 5. Plant Specific Designs Higher RAP mix designs are plant and mix type specific and may not be produced in other plants without validation i.e. – Asphalt Plant A, 9.5M76 25% RAP

    35. Step 6. Independent Testing NJDOT will independently test RAP stockpiles immediately prior to production Supplier will assist in sampling of stockpiles 5 random samples procured for testing by NJDOT Variability of gradation and asphalt content of RAP Correction factor for RAP RAP binder stiffness

    36. Step 7. Plant Verification 2 weeks prior to start of paving, mix produced through plant for mixture validation 9 77mm tall gyratories to be compacted to between 6.5 and 7.5% air voids at plant’s QC lab APA: AASHTO TP63, 64C, 100 psi hose pressure, 100 lb wheel load (test 6 samples) Performance requirement based on NCHRP 9-33 recommendations Overlay Tester: NJDOT Procedure B-10, 25C, 0.025 inch displacement (test 3 samples) Samples must obtain minimum of 100 cycles before failure

    37. Step 8. Failing Lots During production, if there are 2 failing samples in the Lot, revert to current specified RAP percentages i.e. – surface 15% or less; intermediate/base 25% or less

    38. Step 9. HMA Tools for QC For on-going QC, continue RAP sampling at a rate of one sample per day of production RAP sampling analyzed using HMA Tools Same procedure as Step 1 If variability of RAP increases, the allowable percentage of RAP shall decreased as determined using HMA Tools ME may direct additional performance testing during production Corrective action must immediately be taken when failing results obtained

    39. NJDOT RAP Tier #1 10 to 15% RAP Asphalt binder grade for the mixture is selected for the environmental and traffic conditions the same as required for a mixture with all virgin materials. RAP limited to 15 percent or less, it is not necessary to determine the properties of the RAP binder. No grade adjustment is made to compensate for the stiffness of the asphalt binder in the RAP.

    40. NJDOT RAP Tier #2 16% to 25% RAP Selected binder grade for the new asphalt binder is one grade lower for both the high and low temperature than the grade required for a virgin asphalt binder. i.e. - PG 64-22: the required grade for the binder in the recycled mixture would be a PG 58-28. If the specified binder grade for a virgin mixture is PG 76-22, the required grade for the binder in the recycled mixture would be a PG 70-28

    41. NJDOT RAP Tier #2 - continued 16% to 25% RAP The asphalt binder grade can also be selected using an appropriate blending chart if the supplier chooses to adjust the binder selection to compensate for the stiffness of the reclaimed asphalt binder. Extraction and recovery of RAP binder with binder testing required. Regardless of the method used to select binder grade, adjust binder grade as necessary to meet mixture performance requirements.

    42. NJDOT RAP Tier #3 26% to 40% RAP The binder grade for the new asphalt binder is selected using an appropriate blending chart for high and low temperatures. Extraction and recovery of RAP binder and testing is required on a minimum of 5 samples. Adjust binder grade as necessary to meet mixture performance requirements.

    43. NJDOT Higher RAP General Requirements - Summary

    44. Thank you for your time! Questions?

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