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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!: 

Silica Fume is Not a Cement Replacement Material!

Enhancing Mechanical Properties: 

Enhancing Mechanical Properties Chapter Outline

Increased Concrete Strength: 

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

Silica-Fume Concrete: Typical Strengths: 

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

Silica-Fume Concrete: Typical Strengths: 

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

High-Strength Silica-Fume Concrete: 

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

High-Strength Silica-Fume Concrete: 

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

Why Use High-Strength Concrete?: 

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

Slide11: 

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

Increased Modulus of Elasticity: 

Enhancing Mechanical Properties Increased Modulus of Elasticity High-rise columns

Slide13: 

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.

Slide14: 

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.

Improving Durability: 

Improving Durability Chapter Outline

Decreased Permeability for Corrosion-Resisting Concrete: 

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

Silica-Fume Concrete: Corrosion Protection: 

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

Silica-Fume Concrete: Corrosion Protection: 

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

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! Silica-Fume Concrete: Typical Values

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! Silica-Fume Concrete: Typical Values

What About Simply Reducing w/cm to Achieve Durability?: 

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

w/cm reduction versus adding silica fume: 

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

w/cm reduction versus adding silica fume: 

w/cm reduction versus adding silica fume

Slide29: 

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

Slide30: 

Bridge Deck Overlay Ohio DOT

Increased Abrasion Resistance: 

Improving Durability Increased Abrasion Resistance

Slide32: 

Kinzua Dam Western Pennsylvania

Slide33: 

Abrasion-erosion damage to the stilling basin of Kinzua Dam

Improved Chemical Resistance: 

Improving Durability Improved Chemical Resistance

Silica-Fume Concrete: Chemical Resistance: 

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

Silica-Fume Concrete: Chemical Resistance: 

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

Enhancing Constructability: 

Enhancing Constructability Chapter Outline

Improve Shotcrete: 

Enhancing Constructability Improve Shotcrete

Slide42: 

Silica-fume shotcrete

Benefits of Silica Fume in Shotcrete: 

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

Increase Early Strength Control Temperature: 

Enhancing Constructability Increase Early Strength Control Temperature

Slide45: 

Nuclear Waste Storage Facility Hanford, WA

Slide46: 

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

Fast-Track Finishing: 

Enhancing Constructability Fast-Track Finishing

Producing High-Performance Concrete Bridges: 

Producing High-Performance Concrete Bridges Chapter Outline

Why Use High-Performance Concrete in Bridges?: 

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

Why High-Strength HPC?: 

Why High-Strength HPC? Longer spans Increased beam spacings Shallower sections for same span

“The use of high-strength concrete in the fabrication and construction of pretensioned concrete girder bridges can result in lighter bridge designs, with corresponding economic advantages, by allowing longer span lengths and increased girder spacings for standard shapes.” -- B. W. Russell PCI Journal: 

“The use of high-strength concrete in the fabrication and construction of pretensioned concrete girder bridges can result in lighter bridge designs, with corresponding economic advantages, by allowing longer span lengths and increased girder spacings for standard shapes.” -- B. W. Russell PCI Journal

Slide53: 

Ohio HPC Bridge

Slide54: 

New Hampshire HPC Bridge

Slide55: 

Colorado HPC Bridge

For High-Strength Bridges, You Must Consider:: 

For High-Strength Bridges, You Must Consider: Design issues: Larger diameter strand Take advantage of strength of high-durability concretes

For High-Strength Bridges, You Must Consider:: 

Concrete materials and proportioning issues: Random approach to trial mixtures may not be best approach Conduct full-scale testing of selected mixture For High-Strength Bridges, You Must Consider:

For High-Strength Bridges, You Must Consider:: 

Construction issues: Bed capacities Curing temperatures Transportation and erection limitations For High-Strength Bridges, You Must Consider:

Why High-Durability HPC?: 

Why High-Durability HPC? Reduced maintenance costs Longer life “Life-cycle costing”

“The results of this study indicate that there are no fundamental reasons why use of silica fume concrete in bridge deck applications should not continue to grow as ‘high-performance concretes’ become an increasingly important part of bridge construction.” -- Whiting and Detwiler NCHRP Report 410: 

“The results of this study indicate that there are no fundamental reasons why use of silica fume concrete in bridge deck applications should not continue to grow as ‘high-performance concretes’ become an increasingly important part of bridge construction.” -- Whiting and Detwiler NCHRP Report 410

One approach to improving the durability of concrete bridge decks exposed to chlorides in service is to reduce the rate at which chlorides can enter the concrete.: 

One approach to improving the durability of concrete bridge decks exposed to chlorides in service is to reduce the rate at which chlorides can enter the concrete.

Silica-Fume Concrete: Long-Term Performance: 

Silica-Fume Concrete: Long-Term Performance Illinois State Route 4, bridge over I-55 Constructed 1973 October, 1986: southbound lane repaired with dense concrete, w/cm = 0.32 March, 1987: northbound lane repaired with silica-fume concrete, w/cm = 0.31, sf = 11%

Illinois State Route 4, Bridge over I-55: 

Percent chloride by mass of concrete Illinois State Route 4, Bridge over I-55

What About Cracking of HPC Silica-Fume Concrete Bridge Decks?: 

What About Cracking of HPC Silica-Fume Concrete Bridge Decks?

NCHRP Project 18-3: 

NCHRP Project 18-3 Silica-fume concretes tend to crack only when they are insufficiently moist-cured. If silica-fume concrete mixtures are given 7 days of continuous moist curing, there is then no association between silica fume content and cracking.

New York State DOT Review: 

New York State DOT Review Since April, 1996, NYSDOT has used HPC concrete in its bridge decks to reduce cracking and permeability. Class HP concrete: Portland cement 500 lb/yd3 Fly ash 135 lb/yd3 Silica fume 40 lb/yd3 w/cm 0.40

New York State DOT Review: 

New York State DOT Review Since April, 1996, NYSDOT has used HPC concrete in its bridge decks to reduce cracking and permeability. Class HP concrete: Portland cement 300 kg/m3 Fly ash 80 kg/m3 Silica fume 25 kg/m3 W/CM 0.40

New York State DOT Review: 

84 HPC bridge decks were inspected -- 49% showed no cracking “Results indicated that Class HP decks performed better than previously specified concrete in resisting both longitudinal and transverse cracking.” New York State DOT Review

Slide69: 

Interstate 15 rebuilding project in Salt Lake City 144 bridges, all with silica-fume concrete decks!

Slide70: 

Need more information on HPC for Bridges?

Slide71: 

PCA’s new HPC Bridge Booklet

Can HPC Reduce the Life-Cycle Cost of a Bridge?: 

Can HPC Reduce the Life-Cycle Cost of a Bridge? High-strength HPC -- Possibly High-durability HPC -- Probably

End of Chapter 2: 

End of Chapter 2 Main Outline