Ultra Thin Continuously Reinforced Concrete - Modelling &Testing under APT

1. Ultra Thin Continuously Reinforced Concrete - Modelling &Testing under APT Louw Kannemeyer (SANRAL) Bryan Perrie (C&CI) Pieter Strauss (Consultant) Louw du Plessis (CSIR)

2. 34 % Less Than 5 Years

3. 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.

4. 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.

5. 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

6. 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)

7. UTCRCP - Construction

8. UTCRCP - Max Deflection (40kN)

9. UTCRCP APT - Instrumentation

10. UTCRCP - APT Testing

11. UTCRCP – Sections at Failure

12. 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

13. 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.

14. 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

15. 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 @ 50x50mm – current HVS tests in progress to verify this.

16. UTCRCP Future • Reconstructed APT Test Section 1 • Different Steel Mesh (max Ø 5.6mm @ 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

17. New test sections

18. 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)

19. 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

20. Field mix: Compressive strengths

21. Field mix: Flexural Beam strengths

22. Thank You