Ultra Thin Continuously Reinforced Concrete - Modelling

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Ultra Thin Continuously Reinforced Concrete -
Modelling Testing under APT

• Louw Kannemeyer (SANRAL)
• Bryan Perrie (CCI)
• Pieter Strauss (Consultant)
• Louw du Plessis (CSIR)

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34 Less Than 5 Years
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RSA Primary Network Summary

• Problems
• Ageing Network Strengthening Requirement
• Environmental Legislation Materials
  Availability
• Traffic Increased Growth, Increased Heavy,
  Increased Tire Pressures
• Solutions
• Increased Budgets
• Innovative Pavement Repair Strategies
• Must be able to be applied to an existing road
  surface with minimal preparation works required
  to the existing road surface or structures (in
  other words an Inlay or Thin Overlay)
• Must be able to be constructed with road
  construction equipment generally available in
  South Africa
• Must be able to be opened to traffic within 48
  hours
• Must have structural life expectancy in excess of
  30 years with minimal maintenance requirements
  during this period
• Must be able to successfully withstand increased
  axle loads and tyre pressures of modern heavy
  vehicles
• Must be able to meet all functional requirements
  to ensure a safe road surface under all
  conditions
• Must enhance utilisation of materials and labour,
  and
• Must be cost affective.

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Potential Innovative Solution

• Ultra Thin Continuously Reinforced Concrete
  Pavement
• 20 to 60 mm Layer Thickness
• 50 x 50 mm (Ø5mm to Ø8mm) Welded Mesh
• 4.5 versus 0.6 Steel for Traditional CRCP
• Ultra High Strength Cement (UHSC) Paste
• WC Ratio 0.27- 0.30
• Steel- and polypropylene fibres.

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UTCRCP Testing

• Short Term Pavement Performance (STPP)
• APT (HVS) Test Sections at Heidelberg TCC
• Long Term Pavement Performance (LTPP)
• Actual Traffic on Heidelberg TCC Screener Lane

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UTCRCP - HVS Sections Layout

• 60 m

HVS429A5
40 mm UTCRCP
20 mm AC
150 mm G7 (CBR 15 )
3.7 m
HVS428A5
HVS426A5
HVS427A5
1.0mm (40 kN) Surface Deflection Before Overlay
40 mm UTCRCP
HVS431A5
20 mm AC
150 mm C4

• 3.7 m

HVS430A5
150 mm G7
0.3mm (40 kN)
0.6mm (40 kN)
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UTCRCP - Construction
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UTCRCP - Max Deflection (40kN)
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UTCRCP APT - Instrumentation
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UTCRCP - APT Testing
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UTCRCP Sections at Failure
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UTCRCP HVS Repetitions

• Tire Pressure 800 kPa (Truck), 1400 kPa
  (Aircraft)
• Speed 9.0 km/h,
• Load Application Canalized bi-directional
• Aircraft Wheel Used for wheel loads above 100kN
• Shaded Areas Surface Water Added Continuously

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UTCRCP APT Test Conclusions

• Cement Type CEM I products had performance
  differences of up to 50 - worst was used for
  the UTCRCP APT Test
• Layer Placement The use of Asphalt paver
  required very low slump, and with high steel mesh
  content - steel was not completely covered by the
  cement paste
• Steel Fibre Type The drawn wire steel fibres
  used - incorrect in terms of length and shape,
  and
• Steel Bar Spacers 10mm diameter steel bar
  spacers on top of the AC layer to support the
  asphalt paver, acted as crack inducers.

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UTCRCP Finite Element Model

• FE Model developed to predict APT observations
• FE Model Then used to investigate
• Amount Position of steel mesh
• Thickness Stiffness of UTCRCP layer
• Bond Impact of Void
• Substructure Stiffness
• Load Speed

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UTCRCP Conclusions to date

• Different chemical reaction between additives and
  different CEMI cements used
• Do not use spacer bars or asphalt paver for
  placement
• Debonding between UTCRCP and support layers a
  reality in presence of water increase in
  stress
• Curling and presence of anchors did not have a
  major impact
• Steel fibre length and shape do impact
  performance optimum 30 mm x 0.5mm hook end
  fibre
• UTCRCP Thickness and presence of crack/joint is
  critical to performance optimum 50 - 60 mm
• Relative position of steel not crucial, closer to
  top better for reducing compressive stress in
  crack or joint lower spalling and water access
  risk
• Amount of steel not that crucial according to FE
  model, but lab test indicate optimum to be - Ø
  5.6mm _at_ 50x50mm current HVS tests in progress
  to verify this.

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UTCRCP Future

• Reconstructed APT Test Section 1
• Different Steel Mesh (max Ø 5.6mm _at_ 50x50mm),
  Steel Fibre and Concrete Mix Options
• Placed by Hand
• HVS testing currently in progress
• Postulated Alternative
• Introduce as postulated alternative on projects
  Jan 2007

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New test sections
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UTCRCP HVS testing Phase II Update

• First Test (Danish mix design) finished
• Contec-APS binder
• 50 x 50 mm steel mesh, Y 5.6 mm
• Test lasted 1 355 657 reps at mostly 80kN
• (Roughly 30 mil E80s using 4.5 power factor)

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UTCRCP HVS testing Phase II Update

• Second Test (SA mix design 3) just started
• 80kg/m3 steel fibers mix (UP designed binder)
• 50 x 50 mm steel mesh
• R 4 mm steel wire

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Field mix Compressive strengths
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Field mix Flexural Beam strengths
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Thank You