3-MThomas-short - EcoSmart Concrete

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Concrete Containing High Volumes of Concrete Containing High Volumes of Supplementary Cementing Materials: Supplementary Cementing Materials:

Special ConsiderationsSpecial Considerations

Michael ThomasMichael ThomasUniversity of New BrunswickUniversity of New Brunswick

•• Benefits of Using HVSCM ConcreteBenefits of Using HVSCM Concrete

•• Potential Problems with HVSCM Potential Problems with HVSCM ConcreteConcrete

•• Proposed Clause 8.8 on HVSCM Proposed Clause 8.8 on HVSCM Concrete in CSA A23.1Concrete in CSA A23.1

Supplementary cementing material (SCM) - a material that, when used in conjunction with portland cement, contributes to the properties of the hardened concrete through hydraulic orpozzolanic activity, or both.

CSA A3001CSA A3001--0303 Supplementary CementingSupplementary CementingMaterials Materials –– SCM’sSCM’s

• Natural Pozzolans

• Fly AshFly Ash

•• Silica FumeSilica Fume

•• Slag (GGBFS)Slag (GGBFS)

Supplementary CementingSupplementary CementingMaterials Materials –– SCM’sSCM’s

• Natural Pozzolans

• Fly AshFly Ash

•• Silica Fume

•• Slag (GGBFS)Slag (GGBFS)

Materials considered for use inMaterials considered for use inHighHigh--Volume Supplementary Volume Supplementary Cementing Material ConcreteCementing Material Concrete

-- HVSCM ConcreteHVSCM Concrete

• Fly Ash > 30%• Slag > 40%

Concrete with a High-Volume Supplementary Cementing Material

HVSCM ConcreteHVSCM Concrete

What amount constitutes a “high volume”?

(by mass of total cementing material)

Proportion of fly ash = x 100% = 40%120180 + 120

In concrete containing:180 kg/m3 of Portland cement

+120 kg/m3 of fly ash

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The appropriate use of SCM’s can:The appropriate use of SCM’s can:

Improve rheological properties making it easier to pump, place &Improve rheological properties making it easier to pump, place &finish concretefinish concrete

Increase the strength of concreteIncrease the strength of concrete

Reduce permeability to water (& other fluids)Reduce permeability to water (& other fluids)

Increase the resistance to chloride ionsIncrease the resistance to chloride ions

Decrease the corrosion rate of embedded steelDecrease the corrosion rate of embedded steel

Increase the resistance to sulphate attackIncrease the resistance to sulphate attack

Increase the resistance to acid attackIncrease the resistance to acid attack

Suppress deleterious expansion due to alkaliSuppress deleterious expansion due to alkali--silica reaction (ASR)silica reaction (ASR)

Minimize the risk of delayed ettringite formation (DEF)Minimize the risk of delayed ettringite formation (DEF)

EcoSmart™ Concrete


If some is good …If some is good …


If some is good …If some is good …

… more must be better!… more must be better!

Thames Barrage, U.K. (~ 1970)Thames Barrage, U.K. (~ 1970)

50% Fly ash used in caissons to provide temperature control and resistance to estuarine environment

Sewage Works, Sewage Works, WincantonWincanton, UK , UK -- 19841984

C + F

F/(C+F)

W/(C+F)

Strength

=

=

=

=

382 kg/m3

54%

0.43

66 MPa at 6 years

GrangetownGrangetown Link, Cardiff, UK Link, Cardiff, UK -- 19871987

C + F

F/(C+F)

W/(C+F)

Strength

=

=

=

=

430 kg/m3

40%

0.35

66 MPa at 3 years

3

DidcotDidcot Power Station, UK Power Station, UK -- 19821982

C + F

F/(C+F)

W/(C+F)

Strength

=

=

=

=

400 kg/m3

56%

0.37

47 MPa at 91 days

Mumbles Slipway, Swansea, UK Mumbles Slipway, Swansea, UK -- 19831983

C + F

F/(C+F)

W/(C+F)

Strength

=

=

=

=

348 kg/m3

52%

0.40

61 MPa at 7 years

Queen Elizabeth II BridgeQueen Elizabeth II Bridge

70% slag in support piers70% slag in support piers(50% in deck and towers)(50% in deck and towers)

Wet Wet Sleddale Sleddale DamDam70% Slag

Ashford Rail Bridge70% slag in piles50% slag in structuresFor resistance to chloride ion attack

Waitrose, Cheltenham85% slag in secant piling

Concrete Durability Concrete Durability Problems in CanadaProblems in Canada

AlkaliAlkali--Silica ReactionSilica Reaction

4

Corrosion of EmbeddedCorrosion of Embedded--Steel ReinforcementSteel Reinforcement

FreezeFreeze--Thaw Damage &Thaw Damage &DeDe--IcerIcer Salt ScalingSalt Scaling

Portland cement only

25% Fly Ash

1m1m33 Blocks with 25% flintBlocks with 25% flintsand after 8 years exposuresand after 8 years exposure

0.00

0.05

0.10

0.15

0.20

0.25

0 20 40 60

SCM Level (%)

Exp

ansi

on a

t 2 Y

ears

(%)

Class C Fly Ash

Slag

Class F Fly Ash

Effect of SCM’s on Expansion due to ASREffect of SCM’s on Expansion due to ASR

Role of Chlorides

The presence of chlorides at the reinforcing steel can lead to a break down of the protective layer that forms on the steel. This, in turn, leads to corrosion of the steel.

Sources of Chlorides

• Deicing salts• Admixtures• Seawater• Aggregates

Protective layer (γ -Fe2O3)

ClCl

5

BRE Marine BRE Marine Exposure SiteExposure Site

0.330.40K9.959.74Na1.501.20Mg0.410.40Ca2.542.60SO4

17.818.2ClAtlanticBRE

Composition (g/L)IonsAnalyzed

C35 OPC Concretes

0.0

1.0

2.0

3.0

4.0

5.0

0 10 20 30 40Depth (mm)

Chl

orid

e (%

cem

ent) 28 days

1 year

2 years

4 years

10 years

C35 Concretes - 50% Fly Ash

0.0

1.0

2.0

3.0

4.0

5.0

0 10 20 30 40Depth (mm)

Chl

orid

e (%

cem

ent) 28-days

1 year

2 years

4 years

10 years

Carbonation of Fly Ash ConcreteCarbonation of Fly Ash Concrete CarbonationCarbonation--Induced CorrosionInduced Corrosionat Electricity Switching Stationat Electricity Switching Station

Courtesy of BRE

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CarbonationCarbonation--Induced CorrosionInduced Corrosionon Building Facadeon Building Facade

Courtesy P. Harwood

Outdoor CarbonationOutdoor Carbonation

Courtesy of BRE

Freshly fractured surfaces sprayedwith phenolphthalein indicator todetermine the depth of carbonation

Courtesy of BRE

• Strength grade

• Duration of moist curing

• Storage condition (indoor vs. outdoor)

• Fly ash content

• Relative humidity of early storage (i.e. post-curing)

• Temperature of moist curing

• Temperature of early storage

Carbonation at time, Carbonation at time, tt, influenced by:, influenced by:

Incr

easi

ng in

fluen

ce

0

10

20

30

40

0 10 20 30 40 50Fly Ash Content (%)

10-Y

ear O

utdo

or C

arbo

natio

n (m

m)

.

Fly Ash Content vs. Outdoor CarbonationFly Ash Content vs. Outdoor Carbonation

45-MPaConcrete

Fully Carbonated

1-day cure3-day cure7-day cure

7

0

10

20

30

40

0 10 20 30 40 50Fly Ash Content (%)

10-Y

ear O

utdo

or C

arbo

natio

n (m

m)

.


35-MPa

45-MPa

Fully Carbonated

0

10

20

30

40

0 10 20 30 40 50Fly Ash Content (%)

10-Y

ear O

utdo

or C

arbo

natio

n (m

m)

1-day cure 3-day cure 7-day cure


25-MPa

35-MPa

45-MPa

Fully Carbonated

t

Dep

th o

f Car

bona

tion,

d

tkd ⋅= k increases as:• SCM increases• W/CM increases• Strength decreases• Curing decreases

1.861.231.280.287

2.642.022.080.713

3.872.972.802.39145

4.833.203.282.447

5.853.903.733.063

6.385.174.934.85135

7.105.324.604.917

8.376.176.295.843

10.188.258.286.82125

5030150

Fly Ash ContentCuring(days)

Cube Strength

(MPa)

Carbonation Rates, k (mm/y0.5)

Use of HighUse of High--Volume Fly Ash Volume Fly Ash Concrete at York UniversityConcrete at York University

For Class F-2 exposure CSA A23.1-00 requires:

Minimum cover to steel = 40 mmMinimum strength = 25 MPaMaximum W/CM = 0.55

Minimum curing = 3 days (at ≥ 10oC) or until 40% of f’c

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1.861.231.280.287

2.642.022.080.713

3.872.972.802.39145

4.833.203.282.447

5.853.903.733.063

6.385.174.934.85135

7.105.324.604.917

8.376.176.295.843

10.188.258.286.82125

5030150


Cube Strength

(MPa)


~ 5 mm/y0.5




For Portland cement concrete (without SCM) – the time to corrosion, tc, if

depth of cover, dc = 40 mm, and carbonation rate, k = 5 mm/y0.5 is:-

tkd ⋅= yearskdt 64

540 22

=

=

=

Requirements of Existing Canadian StandardRequirements of Existing Canadian Standard

1.861.231.280.287

2.642.022.080.713

3.872.972.802.39145

4.833.203.282.447

5.853.903.733.063

6.385.174.934.85135

7.105.324.604.917

8.376.176.295.843

10.188.258.286.82125

5030150


Cube Strength

(MPa)


~ 8 mm/y0.5




For HVSCM concrete (with 50% fly ash) – the time to corrosion, tc, if depth

of cover, dc = 40 mm, and carbonation rate, k = 8 mm/y0.5 is:-

tkd ⋅= yearskdt 25

840 22

=

=

=

Requirements of Existing Canadian StandardRequirements of Existing Canadian Standard

Fly ash concrete generally carbonates at a faster rate than Portland-cement concrete of the same water-cementitious material ratio. The difference becomes more marked as:

• The level of fly ash increases (especially > 30%)

• The W/CM increases (i.e. strength decreases)

• Period of moist-curing decreases

• Curing

• Achieving the desired cover to the steel

• Maintaining a low W/CM

If reinforced concrete is placed with a high-volume of fly ash and the concrete is exposed to moisture, particular attention must be paid to:

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1.861.231.280.287

2.642.022.080.713

3.872.972.802.39145

4.833.203.282.447

5.853.903.733.063

6.385.174.934.85135

7.105.324.604.917

8.376.176.295.843

10.188.258.286.82125

5030150


Cube Strength

(MPa)


1.861.231.280.287

2.642.022.080.713

3.872.972.802.39145

4.833.203.282.447

5.853.903.733.063

6.385.174.934.85135

7.105.324.604.917

8.376.176.295.843

10.188.258.286.82125

5030150


Cube Strength

(MPa)


Extend curing

1.861.231.280.287

2.642.022.080.713

3.872.972.802.39145

4.833.203.282.447

5.853.903.733.063

6.385.174.934.85135

7.105.324.604.917

8.376.176.295.843

10.188.258.286.82125

5030150


Cube Strength

(MPa)


Increase Strength

WWet burlap & plasticet burlap & plastic

X

Curing MembraneCuring Membrane

X

DeDe--IcerIcer Salt ScalingSalt Scaling

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Laboratory Deicer Salt Scaling Test Laboratory Deicer Salt Scaling Test –– ASTM C672ASTM C672

Surface is ponded with - 4% CaCl2

50 cycles of freezing and thawing

Visual rating used to assess condition of exposed surface after test.

6(v)-4 Photo: Courtesy of PCA

Scaling Performance vs. W/CMWhiting, 1989

0

1

2

3

4

5

0.4 0.5 0.6W/CM

Visu

al R

atin

g

50% Fly Ash

25% Fly Ash

Control

CanadaOntarioAlberta

U.S.A.MichiganMinnesotaWisconsin

Field Survey Port Washington G.S., Wisconsin – pavement concrete placed in 1993

50% Class C Fly Ash used in the concrete

Pleasant Prairie G.S., Wisconsin – pavement concrete placed ~ 1985

70% Class C Fly Ash used in the concrete

20% Class C Fly AshPlaced in 1990

50% Class F Fly AshPlaced in 1991

Pleasant Prairie G.S., Wisconsin

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Age

(yea

rs)

Fly Ash Content (%)

456

2023

123456

10

10 20 30 40 50 60 700

Class C Fly Ash

Class F Fly Ash

ExcellentSatisfactoryUnsatisfactory

Condition:

Field Performance of Fly Ash Concrete

The lab.

versusthe field

Trial Paving Sections at Pleasant Prairie G.S. – built in Fall 1990 High Volume Fly Ash Pavement, Wisconsin(Naik et al, 1995)

Constructed - Fall 1990

PC FA W/CM Visual Mass Loss(kg/m3) (kg/m3) Rating (kg/m2)

218 146 F(40%)

0.36 2+ 0.61

287 66 C(20%)

0.34 - 0.40 1 - 2 0.51

177 177 C(50%)

0.34 - 0.37 4 2.30

Appearance after 6 years Appearance after 6 years

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Appearance after 6 years Parking area somewhere in Wisconsin – placed in 1992

Parking area somewhere in Wisconsin – placed in 1992

40% Class F Fly Ash

Placed & finished with a paving machine

Placed & finished by hand

Portage Avenue, Winnipeg (April 2001)Portage Avenue, Winnipeg (April 2001)

SlipSlip--formform

FixedFixed--formform

Portage Avenue, Winnipeg (April 2001)Portage Avenue, Winnipeg (April 2001)

FixedFixed--formform

SlipSlip--formform

ConclusionsConclusions

Properly designed & cured HVSCM concrete will have an exceptionally high resistance to chloride ion penetration

Early-age resistance can be enhanced by incorporating silica fume in HVSCM concrete

Low grade (high W/CM) HVSCM concrete may be vulnerable to carbonation when poorly cured

HVSCM concrete can be produced to have a high resistance to deicer salt scaling – particular attention should be paid to W/CM and finishing of HVSCM concrete exposed to deicing salts

With appropriate design and production practices, HVSCM concrete could be used in a wide range of applications

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8.8 Concrete made with (HVSCM)8.8 Concrete made with (HVSCM)

New Clause:-

CSA A23.1CSA A23.1--04: Clause 8.8 Concrete made with (HVSCM)04: Clause 8.8 Concrete made with (HVSCM)

HVSCM-1: Fly Ash > 40% or Slag > 45%HVSCM-2: Fly Ash > 30% or Slag > 35%

8.8.1.1

Summary of RequirementsClause


Materials must meet CSA A30018.8.1.2


8.8.1.1



Maximum W/CM reduced by 0.05 for HVSCM-1 in freeze-thawSpecified strength at 56 days (not 28 days)

8.8.1.3



8.8.1.1



When cover to steel < 50 mmW/CM ≤ 0.40 for HVSCM-1W/CM ≤ 0.45 for HVSCM-2

8.8.1.4


8.8.1.3



8.8.1.1



Trial Mixes must be performed8.8.1.5


8.8.1.4


8.8.1.3



8.8.1.1


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Extended curing - wet curing for HVSCM-18.8.1.6



8.8.1.4


8.8.1.3



8.8.1.1




Curing Plan must be submitted8.8.1.7



8.8.1.4


8.8.1.3



8.8.1.1




Curing Plan must be submitted8.8.1.7



8.8.1.4


8.8.1.3



8.8.1.1


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3-MThomas-short - EcoSmart Concrete