1. Concrete (PCC) Mixture Designs for O’Hare Modernization Program Principal Investigators Prof. Jeff Roesler Prof. David Lange PROJECT GOAL Investigate cost-effective concrete properties and pavement design features required to achieve long-term rigid pavement performance at Chicago O’Hare International.

2. Acknowledgements Principal Investigators Prof. Jeff Roesler Prof. David Lange Research Students Cristian Gaedicke Sal Villalobos Rob Rodden Zach Grasley Others students Hector Figueroa Victor Cervantes

3. Project Objectives Develop concrete material constituents and proportions for airfield concrete mixes Strength volume stability fracture properties Develop / improve models to predict concrete material behavior Crack width and shrinkage Evaluate material properties and structural design interactions joint type & joint spacing (curling and load transfer) Saw-cut timing

4. Project Objectives Concrete properties Long-term perfor- mance at ORD Material constituents and mix design Analysis of existing concrete mix designs Laboratory tests Optimal joint types and spacing. Modeling Test for material properties

5. FY2005-06 Accomplishments Tech Notes (TN) - TN2: PCC Mix Design TN3: Fiber Reinforced Concrete for Airfield Rigid Pavements TN4: Feasibility of Shrinkage Reducing Admixtures for Concrete Runway Pavements TN11: Measurement of Water Content in Fresh Concrete Using the Microwave Method TN12: Guiding Principles for the Optimization of the OMP PCC Mix Design TN15: Evaluation, testing and comparison between crushed manufactured sand and natural sand TN16: Concrete Mix Design Specification Evaluation TN17: PCC Mix Design Phase 1 www.cee.uiuc.edu/research/ceat

6. FY2006 Accomplishments Tech Notes (TN) - TN21: An Overview of Ultra-Thin Whitetopping Technology TN23: TN23: Effect of Large Maximum Size Coarse Aggregate on Strength, Fracture and Shrinkage Properties of Concrete TNXX: Effects of Concrete Materials and Geometry on Slab Curling TNYY: Concrete Saw-Cut Timing Model TNZZ: Functionally Layered Concrete Pavements www.cee.uiuc.edu/research/ceat

7. Presentation Overview Large-sized coarse aggregate mixtures Saw-cut timing model Slab Curling Field Demo Project Recycled Concrete Aggregate

8. Crack width, cw Dowels deemed necessary Aggregate Interlock Joints Reduced LTE with small maximum size CA

9. Larger maximum size CA Larger aggregate top size increases aggregate interlock and improves load transfer Crack width, cw Aggregate Interlock Joints

10. Why Larger Size Coarse Aggregate? Potential benefits Less paste  lower cementitious content  Shrinkage Higher toughness  Fracture and crack propagation resistance Increase roughness of joint surfaces  Increased load transfer between slabs  Reduced # of dowels Durability (??)  D-cracking Cost - Effectiveness

11. Experimental Design Effect of aggregate size (1.0” vs. 1.5”) Effect of 1.5” coarse aggregate: Total cementitious content:  688 lb/yd 3, 571 lb/yd 3, 555 lb/yd 3 and 535 lb/yd 3 Water / cementitious ratio:  0.38 versus 0.44 Fly Ash / cementitious ratio:  14.5% versus 0% Effect of coarse aggregate cleanliness

12. Mix Design Results

13. Phase II Mix Summary Larger-size coarse aggregate Effect of larger-size coarse aggregate on strength

14. Drying Shrinkage – Phase II Effect of larger-size coarse aggregate on shrinkage

15. Fracture Energy Results-Phase II Age = 28-days Effect of larger-size coarse aggregate on fracture properties

16. PCC Mix Design – Phase II Summary* Larger aggregates reduce strength by 20%, but… 28-day G F similar  similar cracking resistance Larger aggregates reduce concrete brittleness 1-day fracture energy  with larger MSA  greater joint stiffness / performance No significant shrinkage difference TN23 – April 2006 *Roesler, J., Gaedicke, C., Lange, Villalobos, S., Rodden, R., and Grasley, Z. (2006), “Mechanical Properties of Concrete Pavement Mixtures with Larger Size Coarse Aggregate,” accepted for publication in ASCE 2006 Airfield and Highway Pavement Conference, Atlanta, GA.

17. Saw-Cut Timing Model Concrete E and fracture properties(c f,K IC ) at early ages. Develop curves of nominal strength vs notch depth for timing. d a Notch depth (a) depends on stress, strength, and slab thickness (d) Stress = f(coarse aggregate,  T,RH)

18. Saw-Cut Timing and Depth Saw cut depth / timing – EXPERIENCE Fracture properties at early ages Critical Stress Intensity Factor (K IC ) Critical Crack Tip Opening Displacement (CTOC C ) form this type of specimen Wedge Splitting Test (WST)  need geometric factors d a

19. Saw-Cut Timing and Depth Objectives Develop a FEM Model for WST specimens Integrate measured fracture properties with a Size Effect Model  (after Zollinger et al. 2001) Effect of coarse aggregate size, cementitious content and age on timing/depth Determine saw cut depth for different pavement thicknesses

20. Saw-Cut Timing and Depth Process FRACTURE PROPERTIES Wedge Split Test FEM Model Saw Cut Depth Model Concrete Mix Aggregate sizeAggregate size Cementitious contentCementitious content Crack Propagates

21. WST setup and specimen 30mm 57mm 2mm Notch detail  = a/b 200 mm 205mm 200 mm 80mm 40mm 80mm a b t Wedge Split Testing

22. FEM Model Special Mesh around crack tip Q8 elements Symmetry and BC considerations 200 mm 100 mm Saw-Cut Timing and Depth

23. Saw-cut timing and depth FEM Model Results Determination of Fracture parameters

24. Saw-cut timing and depth FEM Model Results Determination of Fracture parameters

25. SEM Model (Bazant) Saw-Cut Depth Model Nominal Strength vs Notch Depth Chart

26. Concrete Saw-cut timing and depth Mix proportions Aggregate gradations

27. Concrete Fracture Properties Critical Stress Intensity Factor (K IC ) Critical Crack Extension (c f )

28. Westergaard Slab Curling Curling Stress in Concrete Slab Saw cut Depth

29. Saw Cut Depth Charts Low Cementitious Content

30. Saw Cut Depth Charts High Cementitious Content

31. Summary of Notch Depth Requirements

32. Saw-cut timing and depth Summary Saw cut depth increases with concrete age  dramatic increase in depth after 10 to 12 hr. Larger maximum aggregate size increases saw cut depth  High cementitious materials especially

33. Curling Questions How does shrinkage effect slab size? What are the combined effect of moisture/temperature profile? What is the role concrete creep? How do other concrete materials behave – FRC & SRA?

34. Slab Curling Effects of materials and slab geometry on moisture and temperature curling       Time Stress after Grasley (2006) & Rodden (2006)

35. Field vs Lab Field Lab

36. RH Profile - Lab

37. STD Cube Moisture Stresses

38. Summary of Curling Moisture profile effects Temperature Set temperature Shrinkage Reducing Admixtures Fiber Reinforced Concrete

39. Joint Type Analysis How can we choose dowel vs. aggregate interlock joint type & joint spacing? Need to predict crack width & LTE Shrinkage, zero-stress temperature, creep Aggregate size and type (G F ) Slab length & base friction If we use aggregate interlock joints there is a significant cost savings h

40. Field Demo Project

41. Joint Opening Measurement

42. Two week joint opening

43. Concrete Free Shrinkage

44. Dong/Zach formula

45. Slab Lift-Off (Curling)

46. Step 1: Predict crack opening, w Step 2: Predict differential deflection, δ diff Step 3: Determine LTE Inputs: RH, T, L, E, , C Inputs: w, CA topsize,  Step 4: Acceptable LTE? Inputs: δ free, δ diff,  Inputs: FAA recommendation Base friction Curling (thermal and moisture) Steel reinforcement Crack spacing Drying shrinkage Temperature drop Restraints *after Zollinger Crack Width Model Approach

47. Recycled concrete aggregate (RCA)

48. RCA Slight strength reduction Higher shrinkage potential Lower modulus Lower concrete density Potential cost saving ++ Can RCA (coarse) provide similar mechanical properties for airfield rigid pavements as virgin aggregates?

49. Use of RCA for OMP RCA may lead to cost savings Disposal, trucking, aggregate costs RCA may increase shrinkage? RCA less stiff than natural aggregate RCA can shrink more than natural aggregate Shrinkage may be same or reduced if RCA is presoaked to provide internal curing

50. UIUC First Trial RCA from Champaign recycling plant Concrete came from pavements, parking garages, etc. Mix of materials with unknown properties Material washed, dried, and sieved to match natural fine aggregate Soaked for 24 hrs, surface dried, and then 100% replacement of natural fine aggregate

51. Saturated RCA vs Lab Aggregates Similar autogenous shrinkage curves

52. Mechanical Property Test Plan Simple lab crusher Three Point Bend (TPB) test  Fracture properties (Spring 2006) Full-scale crushing at contractor Fracture / strength properties Shrinkage (Summer 2006)

53. Sample Preparation 1. Crush Process

54. Sample Preparation (Con’t) 2. Gradation3. Mixture Design

55. Sample Preparation (Con’t) P 50 mm CMOD 600mm 700mm 150mm 80 mm 4. Dimensions

56. Sample Preparation(Con’t) 3 beams Tested 7 day Position control displacement CMOD = 3 Max 3 Cycles Load – CMOD curve

57. Test

58. Plain Concrete Fracture Behavior PCC RCA

59. FRC Fracture Behavior FRC RCA w/ Fibers

60. Fracture Energy

61. Results (Con’t) RCA Virgin RCA Virgin

62. Results

63. RCA vs FRCA

64. Summary of Fracture Properties

65. Fracture Energy

66. Initial Findings RCA reduce the concrete fracture energy by 50% RCA does not affect the fracture energy in fiber reinforced concrete (peak load still less)

67. Summer 2006 RCA Concrete Mixtures Type of Coarse AggregateVirgin (V)Recycled (R)V & R FibersYesNoYesNo Mix IDVFVPRFRPMP Mix date7.11.06 7.21.06 7.24.06 Mixturelb/yd 3 Water308 Cement Type I607 Coarse Aggregate1645 Fine Aggregate1360 Synthetic Fibers3---3 BSG SSD = 2.42 AC = 5.7%

68. RCA Tests Fresh properteis Slump, Density, Air Compressive Strength (7 days) Split Tensile (7 days) Three Point Bending at 7days G F G f CTOD c Drying Shrinkage – 28 days

69. RCA Summary to Date Optimization of RCA gradation may lead to reduction in overall shrinkage Other concerns: Reduced concrete strength and modulus Potential for ASR from RCA? Source of chlorides to cause corrosion of dowels? Future work - use RCA with known properties Try different gradations Measure strength/fracture properties also

70. Work remaining for FY2006 Joint type and size analysis – con’t Saw-cut timing model - TN Materials and geometry effects on curling - TN Functionally-layered concrete pavements - TN Recycled concrete aggregate – con’t P h Botto m layer Top layer aoao h1h1 h2h2

71. QUESTIONS www.cee.uiuc.edu\research\ceat Thanks!