Chapter 2. Using Silica Fume in Concrete

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
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
High-Strength Silica-Fume Concrete
cement 564 kg/m3 silica fume 89 kg/m3 w/cm
0.220 air 1.1
9
(No Transcript)
10
Why Use High-Strength Concrete?
Column design load 10,000 kips
11
Why Use High-Strength Concrete?
Column design load 50 MN
12
Increased Modulus of Elasticity
Enhancing Mechanical Properties

• High-rise columns

13
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.
14
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.
15
Improving Durability
Chapter Outline
16
Decreased Permeability for Corrosion-Resisting
Concrete
Improving Durability

• Parking structures
• Bridge decks
• Marine structures

17
(No Transcript)
18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
Silica-Fume ConcreteCorrosion Protection

• 5-10 silica fume added by mass of cement
• Mixture may include fly ash or slag
• w/cm lt 0.40 use HRWRA
• Total cementitious materials lt 700 lb/yd3
• Permeability estimated using ASTM C 1202

22
Silica-Fume ConcreteCorrosion Protection

• 5-10 silica fume added by mass of cement
• Mixture may include fly ash or slag
• w/cm lt 0.40 use HRWRA
• Total cementitious materials lt 415 kg/m3
• Permeability estimated using ASTM C 1202

23
(No Transcript)
24
Silica-Fume Concrete Typical Values
Silica fume RCP
Compressive Strength (by mass of cement)
0 gt 3,000 coulombs 5,000
psi 7-10 lt 1,000 coulombs gt 7,000
psi gt10 lt 500 coulombs gt 9,000 psi
Dont fall into strength trap!
25
Silica-Fume Concrete Typical Values
Silica fume RCP
Compressive Strength (by mass of cement)
0 gt 3,000 coulombs 35 MPa 7-10
lt 1,000 coulombs gt 50 MPa gt10 lt
500 coulombs gt 65 MPa
Dont fall into strength trap!
26
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
27
w/cm reduction versus adding silica fume
w/cm sf RCP
Diffusivity
(coulombs) (m2/s E-12)
28
w/cm reduction versus adding silica fume
29
Capitol South Parking Structure Columbus,
OH 5,000 parking spaces
30
Bridge Deck Overlay Ohio DOT
31
Increased Abrasion Resistance
Improving Durability
32
Kinzua Dam Western Pennsylvania
33
Abrasion-erosion damage to the stilling basin of
Kinzua Dam
34
(No Transcript)
35
Improved Chemical Resistance
Improving Durability
36
Silica-Fume Concrete Chemical Resistance
Days to 25 Mass Loss
1 HCl 1 Lactic Acid 5
(NH4)2SO4 5 Acetic Acid 1 H2SO4
37
Silica-Fume Concrete Chemical Resistance
Cycles to 25 Mass Loss
1 5 5
5 H2SO4 Acetic Formic H2SO4
38
(No Transcript)
39
(No Transcript)
40
Enhancing Constructability
Chapter Outline
41
Improve Shotcrete
Enhancing Constructability
42
Silica-fume shotcrete
43
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

44
Increase Early StrengthControl Temperature
Enhancing Constructability
45
Nuclear Waste Storage Facility Hanford, WA
46
These massive walls include portland cement, fly
ash, and silica fume to reduce heat and to
provide early strength for form removal.
47
Fast-Track Finishing
Enhancing Constructability
48
(No Transcript)
49
Producing High-Performance Concrete Bridges
Chapter Outline
50
Why Use High-Performance Concrete in Bridges?

• High strength -- girders and beams
• High durability -- decks, sidewalks, parapets,
  piles, piers, pier caps, and splash zones

51
Why High-Strength HPC?

• Longer spans
• Increased beam spacings
• Shallower sections for same span

52
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
53
Ohio HPC Bridge
54
New Hampshire HPC Bridge
55
Colorado HPC Bridge
56
For High-Strength Bridges, You Must Consider

• Design issues
• Larger diameter strand
• Take advantage of strength of high-durability
  concretes

57
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

58
For High-Strength Bridges, You Must Consider

• Construction issues
• Bed capacities
• Curing temperatures
• Transportation and erection limitations

59
Why High-Durability HPC?

• Reduced maintenance costs
• Longer life
• Life-cycle costing

60
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
61
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.
62
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

63
Illinois State Route 4, Bridge over I-55
Percent chloride by mass of concrete
64
What About Cracking of HPC Silica-Fume Concrete
Bridge Decks?
65
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.

66
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

67
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

68
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.

69
Interstate 15 rebuilding project in Salt Lake
City 144 bridges, all with silica-fume concrete
decks!
70
Need more information on HPC for Bridges?
71
PCAs new HPC Bridge Booklet
72
Can HPC Reduce the Life-Cycle Cost of a Bridge?

• High-strength HPC -- Possibly
• High-durability HPC -- Probably

73
End of Chapter 2
Main Outline