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Block 33 HMA Overlays c SP 13

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  • 1. Rehab & Maint. HMA Overlays 1HMA OverlaysOver PCC PavementsFlexible Pavement Maintenance andRehabilitation

2. Rehab & Maint. HMA Overlays 2Slab Preparation Techniques Crack and seat (JPCP) Break and seat (JRCP) Rubblize (JPCP, JRCP, CRCP) Saw and seal 3. Rehab & Maint. HMA Overlays 3PCCReflection Cracking By far, the biggestproblem in HMAoverlays of PCCpavement Caused by movementat PCC joints andcracksLoad-inducedmovementJoint ClosesHMASlabs Contract Joint OpensSlabs ExpandReflection crack 4. Rehab & Maint. HMA Overlays 4Cracking and Seating Shortens effective slab length Standard practice in many States Not generally recommended for use on poorsubgrades Design methods (overlay thickness) 5. Rehab & Maint. HMA Overlays 5Cracking and SeatingOverlaySubgrade SoilSubbase Firm FoundationCracksShort slablength (~2)Goodgranularinterlock 6. Rehab & Maint. HMA Overlays 6Cracking and Seating 7. Rehab & Maint. HMA Overlays 7Cracking and Seating 8. Rehab & Maint. HMA Overlays 8Cracking and Seating - crackpattern 9. Rehab & Maint. HMA Overlays 9Cracking and Seating 10. Rehab & Maint. HMA Overlays 10What is rubblization? Fracturing: Eliminates slab action Destroys bond between concrete andsteel Rubblized base responds as a tightlykeyed, interlocked high-density, unboundlayer Layer cannot crack; already fractured 11. Rehab & Maint. HMA Overlays 11Why Rubblize? Fracturing PCC to segments less than 9precludes reflection of: Joints Cracks Faults Production Rates up to 1 lane-mile/day 12. Rehab & Maint. HMA Overlays 12HMAPCCLarger Pieces = Larger Movement = Cracking 13. Rehab & Maint. HMA Overlays 13HMAPCCSmaller Pieces = Smaller Movement = No Cracking 14. Rehab & Maint. HMA Overlays 14Benefits Time savingsChoose work hoursHigh production rates Economic SavingsReduce user delay costsReduce construction costs 15. Rehab & Maint. HMA Overlays 15 Environmentally friendlyReduce landfillReduce fuel consumption/air pollution SmoothnessEliminate reflection cracking/faultingBenefits (continued) 16. Rehab & Maint. HMA Overlays 16Construction Procedure Install/replace existing edge drainage system asrequired Remove existing overlay (if present) Remove existing HMA patches, replace withaggregate base as required Fracture the concrete pavement Roll Place HMA overlay (multiple lifts) 17. Rehab & Maint. HMA Overlays 17Resonant Pavement Breaker 18. Rehab & Maint. HMA Overlays 18Multi-Head Breaker (MHB) 19. Rehab & Maint. HMA Overlays 19Rolling 20. Rehab & Maint. HMA Overlays 20Particle Size PCC fractured into 9in.-minus pieces Most pieces are 1- 4in. diameter Aggregate interlockmaintained beneathsurface Rolling knits togethersurface particles 21. Rehab & Maint. HMA Overlays 21Sawing and Sealing Joints Concede appearance of reflection cracking Objective: control rate of deterioration Reduces spalling of reflection cracks Candidates should have well-defined joints Sawcut must be directly above the underlying joint 22. Rehab & Maint. HMA Overlays 22Sawing and Sealing JointsReflection crackOverlayOld pavementSealantInitial sawcut1/3 depthHorizontalopeningJoint reservoirSubgradeVerticaldifferentialmovement 23. Rehab & Maint. HMA Overlays 23Sawing and Sealing Joints 24. Rehab & Maint. HMA Overlays 24Questions?

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