1. Updated mechanistic design method for rigid pavements cncPave

2. Scope Background Research Outcomes Major changes Demonstration Future research

3. Background

4. cncRisk –Predicted risk of failure cncPave –Predicted extent of failure i.t.o. cracking, pumping, faulting and crack spacing for CRCP –Inputs included shrinkage and crack/joint width

5. Recent research

6. Recent Research HVS tests on trial sections at Hilton HVS tests on inlay at Town Hill FWD tests on N2 Postgrad research – shrinkage and strength Thin concrete pavements at Roodekrans Ongoing monitoring of existing roads: –N4 Witbank – Middleburg –N1 Ben Schoeman

7. Recent Research HVS tests on trial sections at Hilton –Four sections, dowelled and undowelled with two aggregate types –Aggregate interlock and dowel load transfer –Effect of crack width, temperature, shrinkage etc HVS tests on inlay at Town Hill –Determine remaining life –Development of punchouts FWD tests on N2 –Effect of temperature on crack movement and load transfer –Effect of traffic on load transfer Postgrad research: –Relationship between compressive, flexural and indirect tensile strengths

8. Outcomes

9. Reports on Gautrans website shortly –Construction –Level 1 analysis - Hilton –Level 1 analysis - Inlay at Town Hill –Level 2 analysis - Hilton and Town Hill MSc – Shrinkage at Wits MSc – Strength at UP

10. Major changes to cncPave

11. Changes Replaced shrinkage value with modified RILEM prediction model Uses RH, cement type, content, water content, temperature etc to predict shrinkage Shrinkage used to predict crack width Long term change in load transfer for dowels and aggregate interlock

12. Changes cont. Inputs –Changed variables –Increased constants –Included cost of support Outputs –Deterioration with time –What-if feature more user friendly

16. Demonstration

17. www.cncipave.org.za www.cnci.org.za

18. Further research

19. Effect of environment – Proposal from Wits Subbase erosion – UP Bond between concrete and support layer