Slurrybound Macadam as Surfacing Option

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Slurrybound Macadam as Surfacing Option
Johan Hattingh
May 2005
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Index

• Introduction
• Overview on the recent development of the Macadam
  Technology
• Research Work 3.1 Laboratory test3.2 Improved
  construction techniques
• Conclusion

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1. Introduction

• Report back on research work
• To date limited to layerworks
• Existing laboratory tests not suitable for the
  slurrybound macadam surfacing option
• Design and specifications more a mog dit troffe
  approach
• Riding quality / Equipment

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Brief overview on recent development of the
Macadam Technology
Theme From base technology using ballast /
coarse aggregate to surface technologies

• Slurry armoring on WB-base. Seaslope
  Interchange. (Roux / Otto CSIR)(Early 90s)

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• Filler sand substituted by bituminious
  slurry.Thick slurrybound Macadam layers using
  railway ballast.Baragwanath Hospital (Potgieter,
  Hattingh).Bus bays in Mohlakeng (1993).

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• Slurrybound Macadam with reduced bitumen content
  in penetration slurry 37mm stone mix (Doornkop
  Soweto).(1994).

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• Composite Macadam (37mm stone bottom / 26mm top
  with rich slurry)gt200km street network
  constructed.Masabeni Street, Springs /
  Attridgeville / Mamelodi / Kagiso / New Brighton
  etc.SABITA-award, 1995.

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• 50mm Slurrybound Macadam (26mm stone
  size)Mamelodi / Attridgeville / Kagiso gt 200km.
  (1995 1997).
• 15mm 25mm thick Slurrybound Macadamgt
  200km.Leroro / Kagiso / Mamelodi

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• Overlay applications with varying
  thicknesses.Marakele National Park / Makapan
  Tower Road / Kagiso

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• Introduction of the spinning beam on
  guiderailsSoweto(2004)

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Research work
3.1 LABORATORY
Current tests all base (layerwork) related
Materials Grading, ALV, PI, etc. Density Ronda
vel tests Strength parameters CPA-method /
Stability / Binder Content on slurry only
Challenges
- Densification of the Marshall
briquette - Penetration of the slurry without
disturbing the stone skeleton - The use of a
bitumen emulsion in the preparation of the
briquette (CPA-method Emulsion substituted by
pen-grade binder)
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Proposed revised briquette preparation

• Mount a Proctor-mould to a vibratory table.
• Fill the mould with the coarse aggregate to half
  32mm.
• Place the Marshall hammer as loose weight on the
  coarse aggregate and vibrate (using the table)
  for 60 seconds.
• Wet the aggregate using either water or a
  bitumen-emulsion 1
• Mix the slurry to specified consistency using the
  flow-plate 2
• Place the determined 3 volume slurry on top of
  the coarse aggregate with the Marshall hammer as
  loose weight on top and allow the table to
  vibrate for 60 seconds.
• Repeat the above to achieve 60mm briquette
  thickness.
• Cure the briquette in the mould before stripping.
• Densify briquettes (30 blows) with Marshall
  hammer after preheating.
• Briquettes ready for further Marshall tests.

1 Deduct volume used from optimum emulsion
content. 2 Optimum slurry mix and consistency is
a separate exercise. 3 Determined in terms of
volumetric principles through experimentation
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Wet aggregate 1 layer 1 Cement 8 net Binder
slurry flowable
Wet aggregate 1 layer 1 Cement 8 net Binder
slurry flowable
Wet aggregate 1 layer 1 Cement 8 net Binder
slurry flowable
Compaction Vibrated without surgarge weight
then level and vibrated with surgarge weight
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Test results on SB-briquettes
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3.2 IMPROVED CONSTRUCTION TECHNIQUES
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3.2 IMPROVED CONSTRUCTION TECHNIQUES (continued)
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3.2 IMPROVED CONSTRUCTION TECHNIQUES (continued)
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4. Conclusion

• Research, design and specifications now
  scientific using Marshall principles
• High quality construction with improve riding
  quality
• Workforce at least three times higher than
  conventional

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5 point scale
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