TRH3 Design and Construction of Surfacing Seals

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TRH3 Design and Construction of Surfacing Seals

• PROGRESS

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Background

• Current Draft released 1998
• Workshops
• Feedback from individuals
• Asphalt Academy Courses
• Circulation of Chapter 7 (Design and Construction
  of seals)

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Summary of Feedback Changes
.Comments - continue

• Guidance required on
• Geotextile seals
• Graded aggregate seals
• Use of rejuvenators and diluted emulsion
  application
• Application and interpretation of
• Ball penetration testing
• Sand patch measurement
• Slurry seal design for different conditions
  (lately)
• Omit all references to tar
• Reference latest SA publications
• Provide more practical hints
• Graphs
• Improve quality in general
• allow higher traffic volume read-off
• Guidance for min and max
• Check list for construction
• Other minor improvements

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Geotextile Seals

• Tack for Geotextile (Mod emulsion)
• gt15000 ELVs 0.5 l/m2 residual binder
• lt 15000 ELVs 1.1 l/m2 residual binder
• Volatiles (prefer no cutters or wait)
• Design seal according to TRH3
• Cor Ball pen 1mm
• No texture adjustment
• Add 30 binder to compensate for movement of
  stone
• Cover spray preferred
• Construction Hints

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Summary of Feedback Changes
.Comments - continue

• Guidance required on
• Geotextile seals
• Graded aggregate seals (Otta seals,
  recommendations for use in SA)
• Use of rejuvenators and diluted emulsion
  application
• Application and interpretation of
• Ball penetration testing
• Sand patch measurement
• Slurry seal design for different conditions
  (lately)
• Omit all references to tar
• Reference latest SA publications
• Provide more practical hints
• Graphs
• Improve quality in general
• allow higher traffic volume read-off
• Guidance for min and max
• Check list for construction
• Other minor improvements

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Summary of Feedback Changes
.Comments - continue

• Guidance required on
• Geotextile seals
• Graded aggregate seals (Otta seals,
  recommendations for use in SA)
• Use of rejuvenators and diluted emulsion
  application
• Application and interpretation of
• Ball penetration testing
• Sand patch measurement
• Slurry seal design for different conditions
  (lately)
• Omit all references to tar
• Reference latest SA publications
• Provide more practical hints
• Graphs
• Improve quality in general
• allow higher traffic volume read-off
• Guidance for min and max
• Check list for construction
• Other minor improvements

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Rejuvenation Fogsprays

• Appropriate products and application for specific
  uses
• Typical problems and solutions

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DE to reduce aggregate loss
DE for enrichment
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Summary of Feedback Changes
.Comments - continue

• Guidance required on
• Geotextile seals
• Graded aggregate seals (Otta seals,
  recommendations for use in SA)
• Use of rejuvenators and diluted emulsion
  application
• Application and interpretation of
• Ball penetration testing
• Sand patch measurement
• Slurry seal design for different conditions
  (lately)
• Omit all references to tar
• Reference latest SA publications
• Provide more practical hints
• Graphs
• Improve quality in general
• allow higher traffic volume read-off
• Guidance for min and max
• Check list for construction
• Other minor improvements

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Texture Depth (Sand patch)

• 500 ml sand
• Box, squeegee, hand
• Wheel track and in-between

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Corrected Ball Penetration

• Mid day
• Two blows
• Measure each blow
• Check
• Embedment
• Crushing
• Displacement

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Summary of Feedback Changes
.Comments - continue

• Guidance required on
• Geotextile seals
• Graded aggregate seals (Otta seals,
  recommendations for use in SA)
• Use of rejuvenators and diluted emulsion
  application
• Application and interpretation of
• Ball penetration testing
• Sand patch measurement
• Slurry seal design for different conditions
  (lately)
• Omit all references to tar
• Reference latest SA publications
• Provide more practical hints
• Graphs
• Improve quality in general
• allow higher traffic volume read-off
• Guidance for min and max
• Check list for construction
• Other minor improvements

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Improvements
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Summary of Feedback Changes
.Comments and concerns

• Conventional binder designs
• Single seals OK (provision for construction
  tolerance)
• Double seals Bit high (Use estimated ALD
  Large ½ of small ALD for design ALD) as
  suggested in document
• Modified binders
• Single seals (10 15 too low binder)
• Rationale discussed not generally supported
• Double seals
• Too high application for Polymer Modified binder
• Too low for Bitumen Rubber
• No provision for combination of binders
• Climate adjustments (not applicable to modified
  binders)
• Methodology not applicable to modified emulsion
  seals

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Summary of Feedback Changes
.Comments and concerns

• Conventional binder designs
• Single seals OK (provision for construction
  tolerance)
• Double seals Bit high (Use estimated ALD
  Large ½ of small ALD for design ALD) as
  suggested in document
• Modified binders
• Single seals (10 15 too low binder)
• Rationale discussed not generally supported
• Climate adjustments (not applicable to modified
  binders)
• Methodology not applicable to modified emulsion
  seals
• Double seals
• Too high application for Polymer Modified binder
• No provision for combination of binders
• Too low for Bitumen Rubber

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Modified and Combination Double seals

• Too high application
• Feedback from several practitioners
• Back calculation to achieve good performing seals
• Solutions
• Design as 2 single seals (ignore texture for
  second layer)
• Use current conventional method (ALD1 ALD 2)

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19 Double 6.7 seal
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Summary of Feedback Changes
.Comments and concerns

• Conventional binder designs
• Single seals OK (provision for construction
  tolerance)
• Double seals Bit high (Use estimated ALD
  Large ½ of small ALD for design ALD) as
  suggested in document
• Modified binders
• Single seals (10 15 too low binder)
• Rationale discussed not generally supported
• Double seals
• Too high application for Polymer Modified binder
• Too low for Bitumen Rubber
• No provision for combination of binders
• Climate adjustments (not applicable to modified
  binders)
• Methodology not applicable to modified emulsion
  seals

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ADJUSTMENT FOR MOD BINDERS

• Lower embedment
• Orientation of aggregate
• Design
• use 1/2 embedment on design graphs
• .... adjustment due to orientation based on Elv
  and ring and ball softening point

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ADJUSTMENT FOR MODIFIED BINDERS
DUE TO

• Aggregate matrix (Lower embedment)
• Orientation of aggregate (More voids)
• Design
• use 1/2 embedment on design graphs
• adjustments as for conventional binder seals
• adjustment due to orientation, based on elv and
  ring and ball softening point

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USE OF DESIGN CHART FOR MODIFIED BINDERS
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Approach to solve

• Report current best practice
• Move towards simple conversion from conventional
  to modified
• Investigations
• Gautrans curves
• MBS approach
• Australia New Zealand approaches

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Non- Homogenous (Single)

• Minimum 1.8 l/m2 (Summer Grades)
• Minimum 1.6 l/m2 (Winter Grades)
• Maximum 3.2 l/m2
• Conversion factors
• 1.4 2.0 times Conventional binder (SA, NZ, Aus)
• Approx 1.8 times min TRH3 conventional for SA

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Homogenous (Single)

• Minimum 1.2 l/m2
• Maximum 2.6 l/m2 (Dependent on Aggregate size)
• Conversion factors
• 1.2 1.8 times Conventional binder (SA, NZ, Aus)
• Approx 1.45 times min conventional for SA
• Additional fog spray close to winter

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Results

• One conversion factor not good enough
• Highly dependent on aggregate application
• Viscosity of binder at time of application
• Orientation of stone (Heavy vehicles) play a role

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Best fit to current practices

• Adjustment to existing factors
• Indication 1 1.8 at Softening point of 55

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Outstanding

• Finalisation of Single Modified binder conversion
• Bitumen Rubber double seal design
• Slurry design for different conditions

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Way forward ?

• Distribute current version
• Workshop on modified binder design
• Research required
• Impact of speed/ gradient/ tyre pressure
• 3D load cell
• Ball penetration vs embedment
• Update of C Marais study
• Cost-effectiveness of seals
• Select and prioritise maintenance strategies