Progress Report on Concrete Mix Designs for O’Hare Modernization Plan

1. Progress Report on Concrete Mix Designs for O’Hare Modernization Plan University of Illinois Department of Civil and Environmental Engineering July 14, 2005

2. Project Goal Investigate cost-effective concrete properties and pavement design features required to achieve long-term pavement performance at Chicago O’Hare International.

3. Project Objectives • Develop material constituents and proportions • Characterize strength, volume stability,and fracture properties of airfield concrete mixes • Develop / improve models to predict material behavior. • Evaluate material properties and structural design interactions, e.g., • joint spacing • joint types • Saw-cut timing

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

5. 2005 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

6. TN2: PCC Mix Design

7. Survey of Existing Mixes

8. Tech Note 3 • Fiber Reinforced Concrete for Airfield Rigid Pavements • Final cost: reduction of 6% to an increase of 11%

9. Tech Note 4 • Feasibility of Shrinkage Reducing Admixtures for Concrete Runway Pavements • Reduced Shrinkage and Cracking Potential ~ 50% reduction • Cost limitations (?) Figure 1. Unrestrained shrinkage of mortar bars, w/c = 0.5 (Brooks et al. 2000)

10. Tech Note 11 • Measurement of Water Content in Fresh Concrete Using the Microwave Method • Strengths: quick, simple, and inexpensive • Limitations: need accurate information on • cement content • aggregate moisture and absorption capacity

11. TN 12: Guiding Principles for the Optimization of the OMP PCC Mix Design • 1st order: • Strength, workability • 2nd Order: • Shrinkage, fracture properties • LTE & strength gain

12. Tech Note 15 • Evaluation, testing and comparison between crushed manufactured sand and natural sand • Gradation • physical properties

13. Manufactured vs Natural Sand 4mm 500mm 4mm 500mm • Visual evaluation • Material retained in the #8 sieve shows difference in the particle shape • The Manufactured sand shows a rough surface and sharp edges due to the crushing action to which it was subjected. Sieve No. 8 Sieve No. 50

14. Tech Note 16 • Concrete Mix Design Specification Evaluation • Preliminary P-501 evaluation • Strength, shrinkage, and material constituent contents

15. 2005 Accomplishments • Specification Assistance • On-site meetings at OMP headquarters • Continued specification recommendations: • Material constituents (aggregate type and size, SCM, etc.) • Modulus of rupture and fracture properties of concrete • Shrinkage (cement content, w/c ratio limits,etc.) • Saw-cut timing, spacing and depth • Pavement design

16. TN17: PCC Mix Design Phase 1 • Develop mix design factorial and verify fresh and hardened concrete properties • More later …

17. Project Tasks and Progress Status Done, TN2, 3, 4, 15 • Literature Review • Survey of existing mix designs • Review of mix design strategies • Volume Stability Tests • Drying and Autogenous shrinkage • Optimization of concrete mixes to reduce volumetric changes • Strength Testing • Modulus of rupture, splitting and compressive strength • Fracture energy and fracture surface roughness Done, TN 12 In progress, TN 12 and TN 17. In progress, TN 12 and TN 17 Start tests in July

18. Project Tasks and Progress • Joint Type Design • Slab size and jointing plans: productivity, cost, performance. • Optimization of concrete aggregate interlock to ensure shear transfer. • Joint (crack) width prediction model for concrete materials. In progress, TN 3. Requires fracture results. In progress, TN 12. Fracture tests In progress, need shrinkage/creep results.

19. Project Tasks and Progress Review in progress, requires fracture results. • Saw-cut timing and depth • Saw-cut timing criteria for the expected materials • Analytical model / Validation • Fiber Reinforced Concrete Materials • Overview of structural fibers for rigid pavement Literature Review done, TN 3.

20. PCC Mix Optimization – Phase I • Factor Levels • Three variables changed independently: • Coarse aggregate top size • ¾” and 1.5” top sizes • Total cementitious content • 588lb/yd3 versus 688lb/yd3 • Water / cementitious ratios • 0.38 versus 0.44 • Phase I was used to develop Phase II mixes.

21. PCC Mix Optimization – Phase I • Mix Design • Five mixes proposed to investigate 3 variables: • Water reducer was added as necessary

22. PCC Mix Optimization – Phase I • Results • Values within range for a typical O’Hare mix

23. PCC Mix Optimization – Phase II • Phase II mix objectives: • Mechanical Properties • Meet specified strength, air content, workability, etc • Maximize fracture resistance & ductility • Volume Stability • Minimize shrinkage • Load Transfer • Maximize aggregate interlock

24. PCC Mix Optimization – Phase II • Experimental Design • Primary factors of interest: • Max. aggregate size, w/c ratio, cement content and fly ash /cementitious ratio. • No water reducers are added in Phase II

25. PCC Mix Optimization – Phase II • Mix Design • Mixes identical to Phase I with the addition of two mixes to investigate O’Hare specification extremes • No water reducers are added in Phase II

26. PCC Mix Optimization – Phase II • Testing • Fresh concrete properties • Slump, Air Content, Unit Weight • Mechanical Testing • Compressive strength at 7 and 28 days • Modulus of Elasticity at 7 and 28 days • Split tensile strength at 7 and 28 days • Modulus of Rupture at 7 and 28 days • Stability Testing • Drying and Autogenous Shrinkage trends for 28+ days • Fracture tests • Early-ages (<48 hrs) • Mature age (28 days)

27. PCC Mix Optimization • Preliminary Strength Summary

28. Toward a shrinkage specification • How much shrinkage is acceptable? • Little information in the literature • State of California Materials and Research Lab • ASTM C157-64 used • Three classes defined • Class A: <320 microstrain • Class B: <480 microstrain • Class C: <640 • Shrinkage over 735 microstrain is considered very severe

29. Toward a shrinkage specification • Other recommendations Non standard test: 8x8x2” specimens Sealed 2 d, air dried 26 d, soaked 4 d, initial measurement taken, oven dried at 122 F and 17% RH Building research station (UK), “Shrinkage of natural aggregates in concrete”, Build. Res. Stat. dig., no. 35, 1963.

30. Toward a shrinkage specification • Do we know exactly how much shrinkage is acceptable? • Not exactly • We know when a material is really bad and when a material is really good • Bad materials should be avoided, and strategies should be examined for approaching low shrinkage concrete at minimal cost

31. PCC Mix Optimization – Phase II • Shrinkage Results • All mixes show similar drying shrinkage • As expected, mixes 688.44 and 688.38 that have a higher amount of cementitious material (688 lb) show higher shrinkage compared to mix 588.38 (588lb of cementitious material) • The water cemen-titious ratio is not a significant factor so far.

32. PCC Mix Optimization – Phase II • Shrinkage Results • All mixes show similar drying shrinkage • As expected, mixes 688.44 and 688.38 that have a higher amount of cementitious material (688 lb) show higher shrinkage compared to mix 588.38 (588lb of cementitious material). • The w/c ratio is not a significant factor so far.

33. PCC Mix Optimization – Phase II • Shrinkage models vs. experimental results • ACI Model • Cement content • Fine/Total agg. • Entrapped air • Volume/Surface • Relative humidity • This model underestimates the experimental results during the first 28 days for the mixes done so far.

34. PCC Mix Optimization – Phase II • Shrinkage models vs. experimental results • FIB 2000 Model • fc at 28 days • Volume/Surface • Relative humidity • Type of cement • This model fits the experimental results during the first 28 days for the mixes done so far.

35. Concrete Shrinkage Summary - 1.5” max aggregate size *units in microstrain

36. Fracture Properties • The relationship between Fracture Energy and Joint Performance • Fracture Energy is characterized using GF • The Shear Stiffness is a good indicator of Joint Performance

37. Fracture Properties • Wedge Splitting Test • Test configuration • Low self weight effect • Ideal for early age testing • Similar to beam test • Load vs. CMOD curve

38. Fracture Properties ft GF = Area under the Curve Cracking Area • Obtaining the Fracture Energy • Calculation of area under the curve

39. Fracture Properties • Effect of aggregate size on Fracture Energy • Larger coarse aggregate and higher Crushing Value increase Fracture Energy

40. Fracture Properties • Effect of Aggregate Type on GF

41. Fracture Properties • Other significance of GF • GF better characterize the effect of coarse aggregate on concrete performance. • For w/c = 0.49 • f’c (12 hrs) = 3.80 – 4.20 MPa • f’c (28 days) = 31.7 – 38.1 MPa • GF (12 hrs) = 52.7 – 194.5 N/m • GF (28 days) = 93.7– 573.3N/m

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

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

44. Tasks for FY 2006 • PCC Mix Optimization • Fracture testing (finish Fall 2005) • Alternative cementitious materials/admix. (Phase III) • FRC, HVFA, Slag • Manufactured Sand (?) • Design and Construction Issues • Saw-cut timing (Dec. 2005) • Joint (crack) width prediction (Summer 2006) • Slab curling analysis* (Summer 2006)

45. Proposed New Ideas • Two-layer concrete pavements • Multi-functional rigid pavement • Cost saving • GREEN-CRETE • Recycled concrete aggregate • Effect of recycled aggregate on mechanical and volumetric properties of concrete • Experimental pavement section and pavement instrumentation

46. Multi-layer concrete pavements Porous Concrete Friction/Noise Layer h1, E1, υ1, α1, k1, ρ1, D1 No fibers h2, E2, υ2, α2, k2, ρ2, D2 fB = 0.1% Shrinkage Resistant Layer h3, E3, υ3, α3, k3, ρ3, D3 fA = 0.25% Fatigue Resistant Layers h4, E4, υ4, α4, k4, ρ4, D4 fA = 0.5% Support Layers T, RH P Functions Wear Resistant h E(z), υ(z), α(z), k(z), ρ(z), D(z) Shrinkage Resistant Fatigue Resistant z Support Layers • Multi-functional rigid pavement: • Volume stability and fracture resistance maximized independently • Skid resistance, aggregate interlock • Reduced slab curling

47. Preliminary Testing of Two-layer Concrete P d Mixture 1 h1 CMOD Mixture 2 h2 a0

48. Recycled Concrete Aggregate

49. Recycled Concrete Aggregate • Advantages of RCA • Performance • Improves strength of base when used in base layer • Potential to minimize D-cracking and ASR • Economic • Limited haul distance • Reduced disposal costs • Lower aggregate cost = lower concrete cost • Overall project savings • Resource Conservation (RCAC is a green material) • Reduced land disposal and dumping • Conservation of virgin aggregates • Reduced impact to landscapes G. P. Gonzalez, H. K. Moo-Young, “Transportation Applications Of Recycled Concrete Aggregate”, FHWA State of the Practice National Review September 2004.

50. Recycled Concrete Aggregate • Some potential disadvantages • Reduced strength and modulus • Particularly with a large amount of recycled fines • Higher drying shrinkage • The reduced stiffness of aggregates reduces the restraint to paste shrinkage • Part of the RCA is just hydrated paste… this will also shrink when dried