Progress Report on O’Hare Modernization Plan

1. Progress Report on O’Hare Modernization Plan Concrete Mix Designs University of Illinois Department of Civil and Environmental Engineering February 8, 2004

2. Concrete Mix Design Team • Prof. David Lange • Concrete materials / volume stability • High performance concrete • Prof. Jeff Roesler • Concrete pavement design issues • Concrete materials and testing

3. Graduate Research Assistants • Cristian Gaedicke • Concrete mix design / fracture testing • Sal Villalobos • Concrete mix design and saw-cut timing • Rob Rodden • testing, instrumentation, shrinkage • Zach Grasley • Concrete volume stability

4. Overview of Project Objectives • Mix Design • Minimize cracking potential • Short and long-term • Minimize Shrinkage • Joint Enhancement • Aggregate Interlock • Targeted dowel placement

5. Completed Activities • Survey of Existing Concrete Mixes • Initial Mix and Testing Methods Evaluation • Technote: Shrinkage Reducing Admixtures in Concrete Pavements • Technote: Fiber-Reinforced Concrete Pavements

6. Survey of Existing Mixes

7. Survey of Existing Mixes

8. Initial Mix Evaluation • Mix used in previous projects at O’Hare • Revised Mix #1905 (2000)

9. Common Strength Tests Compressive strength and Concrete elastic modulus 3rd Point Loading (MOR)

10. Standard Concrete Shrinkage Concrete shrinkage prism ASTM C157 Mortar Bar shrinkage ASTM C596

11. Initial Mix Evaluation • Compressive strength  4470 psi @ 7days • Modulus of Rupture  380 psi @ 7days • Drying shrinkage  440 mm • Autogenous shinkage 170 mm • Instrumented cube (measurement of RH and Temp.)

12. Fracture vs. Strength Properties Brittle s Tough / ductile Deflection MOR • Peak flexural strength (MOR) same but fracture energy (GF) is different • Avoid brittle mixes GF

13. Fracture Test Setup Notched Beam Test Wedge Split Test

14. Wedge Split Test Result ft GF = Area under the Curve Cracking Area • The concept of GF • Wedge split Gf and lch =EGf/ft2

15. Effect of Aggregate Type on GF

16. Benefits of SRA in Pavements • Reduced Shrinkage and Cracking Potential • Near 50 –60% reduction • Increased Joint spacing Brooks et al. (2000)

17. Problems of SRA in Pavements • Technical • Early age strength loss • Delay in set time • Interaction with air entrainment admixture • Potentially washout with water • Economic • Cost

18. Fiber-Reinforced Concrete Pavements • Application of low volume, structural fibers

19. Benefits of FRC Pavements • Increased flexural capacity and toughness • Thinner slabs • Increased slab sizes • Limited impact on construction productivity • Limits crack width • Promotes load transfer across cracks (?)

20. Use of FRC in Pavements • Fiber-reinforced concrete • Final cost: reduction of 6% to an increase of 11%

21. Testing Program • Variables- Phase I • Proposed Variables- Phase II

22. Testing Factorial • Where: • fc’7 = compressive strength at 7 days • E 7 = modulus of elasticity at 7 days • Gf 7 = energy release rate at 7 days • sfl 7 = flexural strength at 7 days • ssp 7 = splitting strength at 7 days • esh = drying shrinkage • eas = autogenous shrinkage • 28-day properties • Fracture Energy

23. Joint Type Selection h • Are dowels necessary at every contraction joint?

24. Aggregate Interlock Joint • Dummy contraction joint • No man-made load transfer devices • Shear transfer through aggregate/concrete surface • aggregate type and size; joint opening

25. Joint Design • Saw-cut timing • Aggregate Interlock • Targeted Dowels

26. Joint Design • Promote high shear stiffness at joint • High LTE • Larger and stronger aggregates • Increase cyclic loading performance • Predict crack or joint width accurately

27. Effect of Concrete Mix on GF 38mm Trap Rock 38 mm Gravel 25mm Trap Rock 25mm Gravel 25mm Gravel 25mm Limestone

28. GF and Shear Load Transfer • Shear load transfer depends on GF at 28 days. • Concrete with high GF at 28 days provides good shear load transfer across cracks/joints.

29. AGGREGATE TYPE TRAP ROCK > RIVER GRAVEL > LIMESTONE

30. AGGREGATE GRADATION Gradation doesn’t have much impact.

31. AGGREGATE SIZE LARGE BETTER THAN SMALL (38MM) (25MM)

32. Other significance of GF • GF better characterize the effect of CA on concrete performance. • w/c = 0.49  fc’ (12 hrs) = 3.80 – 4.20 MPa  fc’ (28 days) = 31.7 – 38.1 MPa  GF (12 hrs) = 52.7 – 194.5 N/m  GF (28 days) = 93.7 – 573.3 N/m

33. Saw-cut Timing and Depth a d • Notch depth (a) depends on stress, strength, and slab thickness (d) • Stress = f(coarse aggregate,T, RH)

34. Requirements for Saw-cut Timing Stress Strength s • Stress = f(thermal/moisture gradients, slab geometry, friction) • Strength (MOR,E) and fracture parameters (Gf or KIC) with time Time

35. Project Goals • Crack-free concrete (Random) • Specification for shrinkage • Specification for GF • Specifiction for MOR • Optimal joint type • Aggregate Specification • Stabilized base • Saw-cut timing • Cost effective! • Minimum Quantity of Cement • Improvement of Aggregate Interlock

36. Concrete Mix Design • Minimum strength criteria (MORmin) • Minimum fracture energy (GF) • Max. concrete shrinkage criteria (sh) • Aggregate top size (Dmax) • Strong coarse aggregate (LA Abrasionmax) • Saw-cut timing table • Slow down hydration rates and temperature

37. Summary of Progress • Concrete Mix Survey Technote • FRC Technote • SRA Technote • Initial Mix Evaluation • Phase I - Testing Program • Saw-Cut Timing

38. Questions