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Bonded Wearing Course

Page history last edited by PBworks 16 years, 5 months ago
Bonded Wearing Course
 
Bonded Wearing Course is a high-performance surface course for preventive maintenance or new construction over either asphalt or concrete pavements. The one-pass construction process consists of a heavy application of polymer modified asphalt emulsion membrane followed by an ultrathin HMA, both placed by a single machine.
 
Bonded Wearing Course combines the strength of hot mix with the flexibility of thin maintenance treatments. It provides a durable, drainable wearing surface on an existing flexible or rigid pavement. By using Type O or Type G rubber mix and terminal-blend rubber materials, it can be placed over the highly modified membrane, thus allowing superior bonding that resists raveling and delamination.
 
Bonded Wearing Course also can be used as the final wearing course on reconstruction, rehabilitation or resurfacing projects. The thick polymer membrane seals and protects the surface and provides superior bonding of the ultrathin mix to the pavement. High quality aggregate is designed to create a durable macro-texture surface. Polymer modified asphalt binder in the mix is selected for climate and traffic. The ultrathin mat (3/4 inch) optimizes the use of the high quality aggregates, while maintaining overhead clearances and curb reveal. The one pass construction process moves quickly, allowing quick traffic return and minimal user delay.
 
The unique system has the best attributes of both stone matrix asphalt (SMA) and open-graded friction course (OGFC) mixes. The polymer membrane migrates into the mix during construction, resulting in an asphalt-rich mix with strong stone-on-stone structure at the interface with the old pavement. Gradation, angular aggregate and asphalt content in the mix are very similar to an SMA. At the surface, the mix is open, with high permeability for water to drain to the sides of the pavement. This open surface has durable skid resistance, reduces noise and improves visibility by reducing backspray in wet weather.
 
What is Bonded Wearing Course?
A single pass surface for preventive maintenance and new construction
  1.  Thick polymer modified emulsion membrane
Ø       Elastomeric polymer
Ø       0.13 - 0.3 gal/yd2
  1.  Ultrathin high performance hot mix
Ø       High-quality aggregate
Ø       Total thickness: 5/8” to 1”
Ø       Mix designed specially for process
Ø       Polymer asphalt binder selected for climate and traffic
  1.  Placed with special equipment
Ø       Applies both emulsion and hot mix in single pass
Ø       Special combination tamping bar - vibratory screed
 
Bonded Wearing Course Advantages
  •  Protects pavement
Ø       Seals out water
Ø       Superior bonding – resists raveling and delamination
Ø       Durable skid resistance
  •  Reduces user delays
Ø       Fast construction
Ø       Night construction
  •  Retains clearances, curbs
  •  Lowers life-cycle cost
 
  • Combines the benefits of both Stone Matrix Asphalt and Open-Graded Friction Courses
SMA high binder content at interface with existing pavement and SMA-type gradation
Ø       Resists wear and rutting up to 10 years or longer with crack sealing
OGFC open surface
Ø       Reduces noise
Ø       Reduces backspray
 
Where should Bonded Wearing Course be placed?
  • Structurally sound concrete or asphalt pavements
  • Distresses listed below not to exceed medium severity as defined by SHRP distress manual:
Ø       Rut depth < 1/2”
Ø       Transverse or longitudinal cracking
Ø       Block, edge or reflective cracking
Ø       Bleeding
Ø       Patches or potholes (both should be repaired)
Ø       Spalling of longitudinal and transverse joints
Ø       Corner breaks
  •  Map cracking and scaling should not exceed 10 m2 in any 100 m2 area
  •  “D” cracking should not exceed low severity
  •  Blowups should not be present
  •  Water bleeding and pumping should not be present
  •  Faulting of transverse joints and cracks should not exceed 9.5 mm
  •  Raveling may be high severity
  •  Polished aggregate may be present
  •  Bonded Wearing Course system is applicable to all traffic levels
 
Bonded Wearing Courses have been placed on numerous city streets and highways in California, as well as on very high to low traffic streets and highways throughout the U.S. The earliest projects are giving over 10 years of excellent performance, and most projects have exceeded expectations. The Bonded Wearing Course ultrathin polymer modified hot mix overlay system should be placed on a structurally sound base. It is not designed to bridge weak spots or to cover underlying pavement deficiencies. Prior to project selection, existing pavement conditions should be evaluated. The pavement conditions and severity levels can be identified by the Distress Identification Manual for the Long-Term Pavement Performance Project (SHRP-P-338, the Strategic Highway Research Program of the National Research Council, 1993). Potential candidates should exhibit satisfactory structural condition and uniform crown.
 
Contact
your local SemMaterials representative for specific details on Bonded Wearing Course project selection, for more information or for other solutions for your paving needs.
 
Phone: 800.365.6656
 
© August 2005 SemGroup, L.P.
 
 
 

Highway 50, Caltrans Pilot Project
Started in the fall of 2002 and completed in the spring of 2003, over 90 Lane Miles of Highway 50 were paved with Bonded Wearing Course. Elevations ranged from 3500 ft to over 7300 ft and tire chain damage was a major concern. This project used Caltrans SP- 39-700 as the specification. The recently completed Caltrans Maintenance Technical Advisory Guide includes an addendum with detailed information on Bonded Wearing Course.

 
“The main performance benefits associated with using a BWC are improved skid resistance, reduced traffic noise, increased ride quality and spray reduction.” Technical Advisory Guide (TAG) For Bonded Wearing Course Pilot Projects, Caltrans , October 2003
 
“BWC retains good skid resistance characteristics over time.” Technical Advisory Guide (TAG) For Bonded Wearing Course Pilot Projects, Caltrans , October 2003
 
“BWC’s rate well in comparison to other surface treatments.” Technical Advisory Guide (TAG) For Bonded Wearing Course Pilot Projects, Caltrans , October 2003
 
“Bonded wearing courses have been estimated to last 7 to 12 years.” Technical Advisory Guide (TAG) For Bonded Wearing Course Pilot Projects, Caltrans , October 2003
 
”Significantly higher pavement surface friction numbers compared to dense-graded HMA wearing course.” National Center for Asphalt Technology (NCAT) Report 97-5
 
“Ideal for use in urban areas and high traffic volume areas where other preventive maintenance treatments pose problems.”
TXDOT Research Project 553
 
“a unique and very desirable method for placing a thin lift of hot mix on an existing surface.”
Louisiana Transportation Research Center Technical Assistance Report No. 12
 
“superior bond to the surface and is the longest lasting of the surface treatments.”
Pavement Magazine, Feb. 2000
 
“I’m constantly looking at methods and materials to save us maintenance dollars in the long run, so I’m really excited about this” CDOT Maintenance Superintendent, Rocky Mountain Construction, July 28, 2003.
 
“The project and its performance have met all performance expectations. The process was efficient with minimal traffic disruption. . . the noise reduction is very noticeable.”, CDOT Materials Engineer, Roads & Bridges, April 2004.
 
“We had never found a surface treatment that protects PCC until this”, ALDOT Chief Engineer, Roads & Bridges, 2003.
 

 

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