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Chip Seal and Scrub Seal Best Practices May 28, 2014


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Presentation delivered at the CalAPA San Diego Technical Committee meeting May 28, 2014 by Kevin Donnelly, Director of Pavement Preservation, Western Emulsions. Topic: Chip Seal and Scrub Seal Best Practices.

Published in: Engineering, Business, Technology

Chip Seal and Scrub Seal Best Practices May 28, 2014

  2. 2. What is Pavement Preservation? •  By applying a series of cost- effective treatments over the life of a pavement, agencies can treat more lane miles, preserve their system and increase customer satisfaction. •  The cumulative effect of systematic, successive preservation treatments is to postpone costly rehabilitation and reconstruction. Pavement Preservation is "a program employing a network level, long-term strategy that enhances pavement performance by using an integrated, cost-effective set of practices that extend pavement life, improve safety and meet motorist expectations." Source: FHWA Pavement Preservation Expert Task Group
  3. 3. Developing A Healthy Transportation Network Pavement Management Pavement Preservation Pavement Recycling Preservation of good roads with low cost treatments saves big money– cost savings is then used to repair poor roads. Recycling with Engineered Emulsions saves 30% to 50% the cost over traditional methods allowing more roads to be repaired with same to better performance expectations over traditional approach Roadway inventory, condition assessment, deterioration and work history allows agencies to track performance, develop political support of treatments and build accurate models for future planning.
  4. 4. Treatments Rejuvenating Fog Seal Slurry Seals / Micro Surfacing Chip Seal / Scrub Seal Cape Seals Scrub Membrane Interlayer Recycles (CIR / CCPR) Recycles (FDR) Pavement Preservation Toolbox 70-100 60-80 25-70 25-70 20-50 0-50 0-40 Sound structural section Sound structural section Sound structural section Fairly sound structural section Fairly sound structural section Fairly sound structural section Failed / Partially failed structural section PCI Use on 3-5 yrs 5-7 yrs 5-10 yrs 7-12 yrs 10-15 yrs 15-20+ yrs Life Extension
  5. 5. Chip Seals and Scrub Seals are placed as: •  A “wearing course” meaning vehicles drive directly upon it; •  Part of a “cape seal” meaning a chip seal is first placed, then covered by slurry seal or microsurfacing; •  An “interlayer” meaning a layer between distressed underlying asphalt pavement and a new asphalt or rubberized asphalt surface.
  6. 6. What exactly is a scrub seal? •  A scrub seal is a more advanced and aggressive multi-purpose chip seal. This rapid crack fill technique utilizes a specialized emulsion which is a polymer modified rejuvenating emulsion (PMRE) as the chip binder and rejuvenator in conjunction with a mechanized scrub broom that forces the optimum amount of emulsion into the cracks. The emulsion is not only highly polymerized which adds flexibility, toughness and durability but contains a recycling agent that conditions the aged surface while restoring the asphaltenes and maltenes balance.
  7. 7. Why Do Agencies Scrub Seal? •  Cost effective surface treatment •  Eliminates the need to crack seal -Less neighborhood disruption •  Protects underlying pavement •  Waterproofs the pavement surface •  Seals cracks and imperfections •  Provides a new wearing surface •  Restores surface friction •  Improves Aesthetics and lane delineation •  Extends the service life
  8. 8. Mechanics
  9. 9. Some Common Types of Chip Seal Oils CRS-2 CRS-2P PMCRS-2H HFRS-2 CHFRS-2 CHFRS-2P PMRE ARE PASS CR STYRAFLEX
  10. 10. TESTING OF EMULSIONS Composition • Particle Charge • Density • Distillation Storage and Handling • Storage Stability • Sieve • Saybolt Viscosity Reactivity •  Demulsibility Residue Tests •  Float Test •  Penetration •  Dynamic Shear Rheometer
  11. 11. Benefits of Polymer Modified Emulsions or PME Improved adhesion (less chip loss) Improved resistance to flow at high temps Improved flexibility at low temps Longer service life
  12. 12. Chip seal failures usually occur in two forms: stripping (loss of cover stone) and bleeding (excess asphalt on the road surface). Many in the industry believe chip seals fail because emulsion and aggregate are not well suited to each other. Certain emulsions do work better with certain aggregates, but seldom - if ever - is the degree of compatibility between any emulsion and aggregate so poor that the asphalt will not coat the rocks. Most failures result from issues related to one of the following six aspects of chip seal construction, listed here with easy solutions: Aggregate and emulsion spread rates. Spread rates must be tailored to each project. Construction techniques. Properly adjusted and maintained equipment, proper timing, and good teamwork ensure quality chip seals. Weather. Hot, dry weather is best for proper emulsion setting and curing. Surface preparation. Repair and clean the road surface: fill potholes, level ruts, seal large cracks, repair broken edges, and scarify and recompact or stabilize an aggregate base, if necessary. If you chip seal over any of these problems, expect these problems to reappear in short time. Traffic control. Keep traffic under 25 mph until after the emulsion sets, the rolling has been done, and the first brooming is completed. Materials. Aggregate should be clean and dry, otherwise the emulsion won't adhere. Source
  13. 13. Chip Seals and Scrub Seals are excellent Stress Absorbing Membrane Interlayer for subsequent treatments •  Slurry Surfacing •  Micro-surfacing •  PME Chip Seals •  Thin Blanket HMA Overlays •  Warm Mix Asphalt Overlays •  Ultra-Thin Bonded Wearing Course
  14. 14. Think Remaining Service Life (RSL) when selecting roads
  15. 15. Double Chip Seal Red Rover Mine Road
  16. 16. Pre-Construction Discussion Ordering Materials Material requirements § Min-max application temps Weather Limitations Surface Preparation Cure Times Sweeping tips techniques Broom set up Broom maintenance Attaching to distributor Adjustments to broom Amount of material to carry in the broom How to work start/stops Bridges Joining passes
  17. 17. Pre-Construction Discussion Striping tips Aggregate application construction sequence § How far between roller/spreader Spray bar issues Traffic control Speed and weight effects on broom Rolling techniques
  18. 18. Equipment Needed to Perform a Chip Seal Asphalt Distributor Truck Aggregate Distributor Dump Trucks Pneumatic Tire Rollers Brooms Tabs Traffic Controls
  19. 19. Caltrans District 8 Maintenance Hwy 74
  20. 20. PASS CR 5/16” Scrub Cape Seal w/ Type II Slurry
  21. 21. Micro Mill, 5/16” RAP Scrub Seal with Type II RAP Micro Surfacing Escondido Canyon Road - Acton, CA
  22. 22. Micro Surfacing on Scrub Seal Stunt Road
  23. 23. Recycled Asphalt Pavement (RAP) Chip •  Cost effective with best quality •  Produce multiple products if possible •  Single stones and conglomerations •  Residual asphalt content will vary by sample
  24. 24. Crushed and screened 5/16” Rap aggregate
  25. 25. Thank you. Kevin Donnelly, APM Director, Pavement Preservation 805-886-0900