MnPavement Rehabilitation Best Practices LRRB Inv 808 Gene Skok (UofM) Shongtao Dai (MnDOT( MnDOT) 12 th Minnesota Pavement Conference February 14, 2008 Mn/DOT Office of Materials and Road Research
Outline Objectives Literature Review Types of Reclamation Definition of Factors Decision Checklists Criteria Recommendations
Pavement Rehabilitation (LRRB INV 808) Objective Laying out the Best Practices for the selection of asphalt concrete recycling techniques: Full-Depth Reclamation (FDR) Cold In-place Recycling (CIR) Mill/Overlay (M&O).
Why Mill and Overlay? Low Initial Cost Minimize clearance/grade issues Construction time minimized Covers up reflective cracks
Rehabilitation Decision Factors Existing Conditions (PQI) Ride (RQI) Surface Rating (SR) Transverse Cracks (0.01, 0.10, 0.20) Long. Cracks & Deter. (0.02, 0.03, 0.04).
Rehabilitation Decision Factors (cont.) Multiple Cracking (0.15) Alligator Cracking (0.35) Rutting (0.15) Raveling & Weathering (0.02) Patching (0.04) PQI = (RQI X SR) 1/2
STRUCTURAL ADEQUACY TONNAGE PAVEMENT THICKNESS DESIGN Soil Factor (GE vs HCADT) R-Value (GE vs ESAL s) Mn/PAVE (Thickness vs Load Spectra)
Pavement Rehabilitation Database Location Original Pavement Construction Pre-Rehab Rehab Post-Rehab
Pavement Rehabilitation Database
MN Rehabilitation Projects Surveys District 2 District 1 CIR (37) District 4 District 3 FDR (41) M&O (25) District 8 Metro District 7 District 6
SR Values Pre-Rehab. SR Values 4 for C.I.R. Projects 3.5 3 2.5 SR 2 1.5 FDR Average 1 0.5 0 Project
Pre Rehabilitation SR Value for FDR SR Values 4 Projects 3.5 3 2.5 SR 2 1.5 FDR Average 1 0.5 0 Project
Pre-Rehabilitation SR Value for Mill and Overlay Projects SR levels 4 3.5 3 SR 2.5 2 1.5 M&O Average 1 0.5 0 Project
SR Values before and Degradation Curves after Rehabilitation 4.5 4 3.5 SR 3 2.5 2 1.5 CIR FDR Med. M&O Thick M&O 1 0.5 0-20 -15-10 -5 0 5 10 15 20 Year from rehab
Surface Rating (SR) Degradation Rates Rehabilitation Procedure Cold In-Place Recycling Full Depth Reclamation Thin Mill & O.L. Medium Mill & O.L. Thick Mill & O.L. Deterioration Rate 0.040 0.021 0.040 0.065 0.021
SR Values for Individual Degradation curves FDR Projects SR Before/After (FDR) SR 4 3.5 3 2.5 2 1.5 1 0.5 0-15 -10-5 0 5 10 15 Year Relative to Rehab 4 5 8 9 10 12 13 15 27 28 31 32 33 48 30
Transverse Cracking IWD. for FDR Projects Condition Histories Transverse IWD Transverse Distress (CIR) 9 8 7 6 5 4 3 2 1 0-20 -15-10 -5 0 5 10 15 20 Year Relative to Rehab 1 2 16 17 18 19 20 21 22 25 40 41 42 43 45 46 47 49
Transverse Cracks I.W.D. for S.R. Level TC effect on SR 9 9 8 8 7 7 Transverse Crack IWD 6 5 4 3 6 5 4 3 CIR FDR M&O Typical 2 2 1 1 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 Overall SR
Decision Check Lists 1. Geometrics 2. Pavement Condition (s) 3. Review Figure 3.7 (PQI < 2.5) 4. Structural Adequacy a. Pavement Thickness b. Tonnage c. Falling Weight Deflectometer
Geometrics Checklist Clearances Shoulder Width Grading Width Curb and Gutter Constructability
Geometrics 3.6 GEOMETRIC CONSIDERATIONS NOTE: Official State Aid rules can be found directly at http://www.revisor.leg.state.mn.us/bin/getpub.php?pubt ype=rule_chap&year RULE_CHAP&year=current&chapter=8820 OR by browsing to www.leg.state.mn.us and then selecting: Statues, Session Laws, and Rules Under the Minnesota Rules section on the main page, Retrieve an entire chapter Enter in the number 8820 and click Get Chapter
Table 3.6. Pavement Condition(s) ) Checklist Ride Quality Index (RQI) 1.Methoda. Pavement Conditions 1. Using Mn/DOT Van 2. Rating Panel Checklist Critical Value 2. Rated by a panel Surface Rating (SR) Condition Individual Weighted Distress (IWD) 1.Rut Depth 2.Transverse Cracking a.low Severity b.medium Severity c. High Severity Total T.C. IWD 3. Long. Cracking/ Joint Det. 4. Alligator Cracking 5. Raveling, Weather, Patch Total IWD SR PQI Discussion
Selection of Rehabilitation Procedure based on Surface Procedure Selection Ratings Selection of Rehabilitation Procedures based on Surface Conditions For SR =< 2.5 IWD(Mult) > 5 and/or IWD(Trans) > 5 HMA > 4 FDR CIR Expected Life (see Table 3.3 and 3.6) HMA < 4 FDR IWD(Mult) < 5 and IWD(Trans) < 5 RQI > 3.0 Thin M&O RQI < 3.0 Med. or Thick M&O
Structural Adequacy Table 3.7 Summary of Structure Adequacy. PAVEMENT THICKNESS 1. Design Procedure: a. Soil Factor, R-Value R, Mechanistic b. Soil Type (Classification) AASHTO Class R- Value Measured Estimated Resilient Modulus Measured Estimated c. Traffic (20 year Predicted): AADT HCAADT ESAL s d.required Thickness (Granular Equivalent Thickness) Soil Factor Procedure R-Value Procedure Mn PAVE NOTES
SPECIFIC CRITERIA 1. Is existing HMA thickness adequate to support CIR equipment? (3.5 in.)? 2. Is existing subgrade stiffness adequate to support CIR equipment? (5000 psi)? 3. Consider SR degradation rate.
Criteria Continued 4. If not structurally adequate then CIR should NOT be used without additional overlay 5.If SR < 2.5 and IWD for multiple cracking or T.C. > 5.0: - Mill and OL should not be used - if existing HMA > 3.5 in. use FDR or RIC - if existing HMA < 3.5 in. use FDR only
Criteria Continued more 6. If the SR < 2.5 and Mult.. or Transverse cracking IWD is < than 5.0, use mill & overlay 7. Finally, cost/benefits should be considered along with decay rates in the final decision. NOTE: T.C. IWD = 5.0 for a pavement with all medium severity T.C. represents a crack count of 50 cracks per 100 ft. An IWD = 5.0 for a pavement with all high severity T.C. represents a crack count of 25 cracks per 100 ft.
RECOMMENDATIONS Determine ride (RQI) periodically with Mn/DOT IRI correlation(s) ) or panel Determine IWD and SR using Mn/DOT Distress Manual periodically Run FWD periodically to determine: - Tonnage - Subgrade Stiffness - GE of pavement section
RECOMMENDATIONS (cont.) 4. Continue documenting performance information from 1., 2., and 3. in the rehabilitation database (?) - include RQI, SR (IWD s( IWD s), GE, Soil Stiffness. This could be part of the PMS or Mn/ROAD database (s).
Summary Types of Reclamation Decision Factors Database Development Decision Checklists Criteria Recommendations
Acknowledgements Minnesota Local Road Research Board Technical Advisory Committee Mn/DOT, Dave Janisch, Erland Lukanen, Graig Gilbertson,Perry Collins Counties, Brian Noeltzman,Wayne Olson,Milt Hagen,Brad Wentz,Brian Shepard,Kathy Jaschke,Darrell Pettis, Curt Bolles,, Guy Kohnlhofer, Midwest Construction, Tom Olson,American Engineering, Dave Rettner,, SEM Materials,Dan Wegman,
THANK YOU!, Any Questions?