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Chapter 2. Using Silica Fume in Concrete

Chapter 2. Using Silica Fume in Concrete. Enhancing Mechanical Properties Improving Durability Enhancing Constructability Producing High-Performance Concrete Bridges. Silica Fume is Not a Cement Replacement Material!. Enhancing Mechanical Properties. Chapter Outline.

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Chapter 2. Using Silica Fume in Concrete

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  1. Chapter 2. Using Silica Fume in Concrete • Enhancing Mechanical Properties • Improving Durability • Enhancing Constructability • Producing High-Performance Concrete Bridges

  2. Silica Fume is Not a Cement Replacement Material!

  3. Enhancing Mechanical Properties Chapter Outline

  4. Increased Concrete Strength Enhancing Mechanical Properties • High-rise columns • Precast bridge beams

  5. Silica-Fume Concrete: Typical Strengths 15% 10% 5% 0% Control mixture cement: 658 lb/yd3 w/c: 0.41 air: 5% 0 3 7 28 60 Age, days

  6. SI Silica-Fume Concrete: Typical Strengths 15% 10% 5% 0% Control mixture cement: 390 kg/m3 w/c: 0.41 air: 5% 0 3 7 28 60 Age, days

  7. High-Strength Silica-Fume Concrete cement: 950 lb/yd3 silica fume: 150 lb/yd3 w/cm: 0.220 air: 1.1%

  8. SI High-Strength Silica-Fume Concrete cement: 564 kg/m3 silica fume: 89 kg/m3 w/cm: 0.220 air: 1.1%

  9. Why Use High-Strength Concrete? Column design load = 10,000 kips

  10. SI Why Use High-Strength Concrete? Column design load = 50 MN

  11. Increased Modulus of Elasticity Enhancing Mechanical Properties • High-rise columns

  12. Key Bank Tower Cleveland, Ohio High-strength (12,000 psi), high-modulus (6.8 million psi) concrete columns were specified at the corners of this structure to stiffen against wind sway.

  13. SI Key Bank Tower Cleveland, Ohio High-strength (83 MPa), high-modulus (47 GPa) concrete columns were specified at the corners of this structure to stiffen against wind sway.

  14. Improving Durability Chapter Outline

  15. Decreased Permeability for Corrosion-Resisting Concrete Improving Durability • Parking structures • Bridge decks • Marine structures

  16. Silica-Fume Concrete:Corrosion Protection • 5-10% silica fume added by mass of cement • Mixture may include fly ash or slag • w/cm < 0.40: use HRWRA • Total cementitious materials < 700 lb/yd3 • Permeability estimated using ASTM C 1202

  17. SI Silica-Fume Concrete:Corrosion Protection • 5-10% silica fume added by mass of cement • Mixture may include fly ash or slag • w/cm < 0.40: use HRWRA • Total cementitious materials < 415 kg/m3 • Permeability estimated using ASTM C 1202

  18. Silica-Fume Concrete: Typical Values Silica fume RCP Compressive Strength (by mass of cement) 0% > 3,000 coulombs = 5,000 psi 7-10% < 1,000 coulombs > 7,000 psi >10% < 500 coulombs > 9,000 psi Don’t fall into strength trap!

  19. SI Silica-Fume Concrete: Typical Values Silica fume RCP Compressive Strength (by mass of cement) 0% > 3,000 coulombs = 35 MPa 7-10% < 1,000 coulombs > 50 MPa >10% < 500 coulombs > 65 MPa Don’t fall into strength trap!

  20. What About Simply Reducing w/cm to Achieve Durability? “The results clearly indicate that silica fume was effective in reducing the [Rapid Chloride Permeability Test] values regardless of the curing regimes applied. Moreover, silica fume enhanced chloride resistance more than reducing w/cm. This effect was confirmed by the diffusion tests.” -- Hooton et al. 1997

  21. w/cm reduction versus adding silica fume w/cm % sf RCP Diffusivity (coulombs) (m2/s E-12)

  22. w/cm reduction versus adding silica fume

  23. Capitol South Parking Structure Columbus, OH 5,000 parking spaces

  24. Bridge Deck Overlay Ohio DOT

  25. Increased Abrasion Resistance Improving Durability

  26. Kinzua Dam Western Pennsylvania

  27. Abrasion-erosion damage to the stilling basin of Kinzua Dam

  28. Improved Chemical Resistance Improving Durability

  29. Silica-Fume Concrete: Chemical Resistance Days to 25% Mass Loss 1% HCl 1% Lactic Acid 5% (NH4)2SO4 5% Acetic Acid 1% H2SO4

  30. Silica-Fume Concrete: Chemical Resistance Cycles to 25% Mass Loss 1% 5% 5% 5% H2SO4 Acetic Formic H2SO4

  31. Enhancing Constructability Chapter Outline

  32. Improve Shotcrete Enhancing Constructability

  33. Silica-fume shotcrete

  34. Benefits of Silica Fume in Shotcrete • Reduction of rebound loss up to 50% • Increased one-pass thickness up to 12 in. (300 mm) • Higher bond strength • Improved cohesion to resist washout in tidal rehabilitation of piles and seawalls

  35. Increase Early StrengthControl Temperature Enhancing Constructability

  36. Nuclear Waste Storage Facility Hanford, WA

  37. These massive walls include portland cement, fly ash, and silica fume to reduce heat and to provide early strength for form removal.

  38. Fast-Track Finishing Enhancing Constructability

  39. Producing High-Performance Concrete Bridges Chapter Outline

  40. Why Use High-Performance Concrete in Bridges? High strength -- girders and beams High durability -- decks, sidewalks, parapets, piles, piers, pier caps, and splash zones

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