Developing Fly Ash for Use in Concrete:Developing Fly Ash for Use in Concrete:Overview of UK University Research

R.K. Dhir* and M. J. McCarthy+yUniversity of Dundee, UK

* Emeritus Professor of Concrete TechnologyEmeritus Professor of Concrete TechnologyDirector, Applying Concrete Knowledge

+ Senior Lecturer

Forty Years Fly Ash Research at Dundee

Main ResearchersMain Researchers

Prof. R. K Dhir: 40 years Dr. M. R. Jones: 28 years Dr. M. J. McCarthy: 22 years

Main Thrust of Research1 D l i i l F d t l C t

y y

1. Developing simple Fundamental Concepts2. Developing Challenging Fly Ash Applications3 Di i ti f N K l d3. Dissemination of New Knowledge

Main Thrust of Dundee Research1. Developing Simple Fundamental Concepts

1.1 Fly Ash1 1 1 BS 3892:Part 1 PFA1.1.1 BS 3892:Part 1 PFA1.1.2 EN 450 Fly Ash1.1.3 Conditioned/Lagooned Fly Ash1.1.4 Stockpiled/Landfilled Fly Ashp / y1.1.5 Co- Combustion Fly Ash

1.2 Enabling Low CO2 Emission cements1.2.1 Low Energy Cements

h l l h1.2.2 High Volume Fly Ash Cements1.3 High performance Fly Ash

2. Developing Challenging Fly Ash Applications2 1 General Use in Concrete2.1 General Use in Concrete2.2 High Performance Concrete2.3 Chloride resistant Concrete2.4 Minimising ASR with EN 450 / CFA2.4 Minimising ASR with EN 450 / CFA2.5 Fly Ash Mortar2.6 Foam Concrete2.7 Sulfate resisting Grout2.8 Activated Sand2.9 Lime Stabilised Soils with Fly Ash

3. Multi Blend Cements with Fly Ash

1.1 What is Fly Ash?

• Fly Ash (FA) is the particulateFly Ash (FA) is the particulate materials produced at coal fired power stations.

• Spherical particles, in range < 1 μm to 150 μm.

• Pozzolanic materials, reactingPozzolanic materials, reacting with water and lime to form cementitious compounds.

1.1.1 Fly Ash: All Grades and BS3892, Part 1 PFA

Strength Development with AgeStrength Development with AgeStrength Development with AgeStrength Development with Ageh

Fly ash

PCh

Fly ash

PC

Stre

ngth PC

Stre

ngth PC

Strength development with

Age, days3 7 28 90

Designed at equal 28 d t th

Age, days3 7 28 90

Designed at equal 28 d t th

Enhanced long-term strength development

Strength development with additional fly ash in concrete mixes

28 day strength28 day strength

Standards

1965: BS 3892. FA as fine aggregate.1965: BS 3892. FA as fine aggregate.

1982: BS 3892,Part1. FA as cement component.

1995: BS EN 450. Wide range FA, in particular fineness, as cement component.

2000: BS EN 197-1. Wide range materials as cement component.

2005: BS EN 450 (revised). Includes co-combustion FA.

1.1.2 BS EN 450 Fly Ash

Single and Multiple SourcesSingle and Multiple Sources

4570% PC / 30% PFA;

PFA 1-4, 6m

2 Single Source Classified

40PFA 8(a)-(g)PFA 9(a)-(h)

GTH

, N/m

m

35

STR

ENG

30

28 D

AY

Multiple Source

0 5 10 15 20 25 30 35 40 4525

Binder content - 350 kg/m 3

PFA FINENESS, % 45um sieve ret.

1.1.2 BS EN 450 Fly Ash Appropriate and Sustainable use of PFA, based on Equal Performance

Higher GradeHigher Grade

MaterialsTo achieve

Equalityq y

BENCH MARK MATERIAL100%

To achieve Important Considerations

• Mix DesignEquality

Lower Grade

Materials

• Cost

• Performance

1.1.2 BS EN 450 Fly Ash

Achieving Equal Performance

Bulk Engineering Properties such as, Strength, Modulus of Elasticity, Creep, Shrinkage, Durability Related

REN

GTH

y, p, g , yProperties, such as, Permeation, Chloride Ingress, Carbonation, Sulfate Resistance, Abrasion, Freeze/ Thaw

Reduce water content/Increase binderCR

ETE

STR

BS3892 Part 1 BS EN 450

Increase binder content/Combine theseCO

NC

5 10 15 20 25 30 35 40 450

PFA FINENESS, % 45 mm sieve retentionPFA FINENESS, % 45 mm sieve retention

1.1.3 Conditioned and Lagooned Fly Ash

WorkabilityWorkability Compressive Compressive PermeationPermeationWorkabilityWorkability ppStrengthStrength

PermeationPermeation

100 Nominal 75 mm 70mm

²

90

60

80

mm

Dry FA0 months6 months

Nominal 75 mmfor dry FA

5028 d

ay),

N/m

70/s x

10

-2

40

60

SLU

MP,

m

30

REN

GTH

(2

50

A-1

0, m

l/m²/

Increasing

0 35 0 45 0 55 0 65 0 750

20

0 35 0 45 0 55 0 65 0 7510C

UB

E ST

R

0 35 0 45 0 55 0 65 0 7530

ISAg

storage

0.35 0.45 0.55 0.65 0.75

W / C RATIO

0.35 0.45 0.55 0.65 0.75 0.35 0.45 0.55 0.65 0.75

30% FA levelFine FA (10% moisture)

1.1.4 Stockpiled and landfilled Fly Ash

Overview of Fly Ash Processing System4. Froth 4. Froth

FlotationFlotationFrothFroth

1. Pre1. Pre--ScreeningScreening

3. Primary 3. Primary SeparationSeparation

OverflowOverflowAirAir

FeedFeed

4a. 4a. Column Column FlotationFlotation

OverflowOverflowFeedFeed

Clean Clean WaterWater

TailsTails

FrothFroth

2. 2. SlurrificationSlurrification

UnderflowUnderflow

WaterWater

4b. Mechanical 4b. Mechanical FlotationFlotation

TailsTails

5. Lamella Hydraulic5. Lamella Hydraulic

SlurrificationSlurrification

CenospheresCenospheres

FlotationFlotation

UnderflowsUnderflows

5. Lamella Hydraulic 5. Lamella Hydraulic ClassificationClassification

U4U4 U3U3 U1U1U2U2U5U5UltrafineUltrafine

1.1.5 Co-Combustion Fly Ash

Effect on Fly Ash and Concrete StrengthEffect on Fly Ash and Concrete Strength60

mm

²

CEMENT CONTENT,FINENESS

40

50

NG

TH, N

/m

350 kg/m³FINENESS,

% ret. 45 µmLOI, %

CO-FUELCA CCA CCACA

30

40

BE

STR

EN

Meat/Bone Meal

P lt D

25.8 26.2

25 3 29 2

6.4 7.1

4 9 5 9

20

DAY

CU

B

Coal-fired FA SeriesCo-fuel FA Series

Poultry Dung

Cocoa Shells

25.3 29.2

23.0 21.1

4.9 5.9

4.0 4.2

0 5 10 15 20 25 30 35 40 451028

Sewage Sludge 28.0 27.0 7.0 7.2

FA FINENESS, % 45 µm sieve retention

Enabling Low CO Emission CementsEnabling Low CO2 Emission Cements

1.2.1 Low Energy Cements

80 Development of Concrete StrengthDevelopment of Concrete Strength

70

N/m

m² PC

PC / PFA 45%RHC / PFA 45%

60

REN

GTH

, RHC / PFA 45%

50

SIVE

STR

MC+/ high PFA contentto enhance early and

30

40

OM

PRES

S to e a ce ea y a dlong-term strength

Coarse and conditionedPFA can regulate early

20

30

CO PFA can regulate early

reactions

1 10 100 1000AGE, days

MC+ Mineralised Clinker

1.2.1 High Volume Fly Ash Cements

Effect on Engineering PropertiesEffect on Engineering PropertiesCEMENT TYPE

PROPERTY DESIGN STRENGTH, N/mm2

PC MC+/45FA

Effect on Engineering PropertiesEffect on Engineering Properties

PC MC+/45FA

1Modulus of Elasticity, kN/mm2

35 25.0 25.550 28.5 29.070 33.0 35.5

2Drying Shrinkage, Microstrainy g S age, c ost a35 490 46550 560 54570 600 600

1Creep, Microstrain50 1200 600

1 test carried out at 28 daystest carried out at 28 days2 12 month result

MC+ Mineralised clinker

High Performance Fly Ash

Improved Fresh/Hardened Concrete Performance

180 MPa

m140

160

180

PC

10% SF10% SFFA

ngth

, M

100

80

UM

P, m

100

80

120

ve S

tre

60

SLU

60

40

80

mpr

essi40

20

PC 10% SF

10% SFFA

5% SF

5% SFFA

20

015% SFFA

Com

1

Age da3 7 28 56 56

0

SF SFFASF SFFA SFFA Age, day

2. Developing Challenging Fly Ash Applications in ConcreteApplications in Concrete

Construction

2.1 General Use in Concrete

•• Improved fresh Improved fresh propertiespropertiespropertiesproperties

•• Improved engineering Improved engineering propertiespropertiesp pp p

•• Improved durabilityImproved durabilityImproved durabilityImproved durability

2.2 High Performance Concrete 2.2 High Performance Concrete

PROJECT Year(s) Location Combination, Strength, Main % N/mm2 Requirement

PacificFirst Centre

1989 United Statesof America

PC/FA9/SF6 124/56day Ultra high long-term strengthFirst Centre of America g

Petronas Twin Towers

1995 Malaysia PC/FA18/SF10 80 High early and long-term strengthstrength

Tsing Ma Bridge

1997 Hong Kong PC/FA25/SF5 50 Chloride/ permeability resistance

Storebaelt Crossing

1998 Denmark PC/FA10/SF5 - Chloride / sulfate / freeze-thaw

Bandra Worli On-going India PC/FA25/SF7 60 Chloride inBandra Worli Sealink

On-going India PC/FA25/SF7 60 Chloride in marine exposure

Burj Dubai 2004-2009 United Arab Emirates

PC/FA25/SF7PC/FA13/SF10

6080

Chloride / sulfateSt th /Emirates PC/FA13/SF10 80 Strength /

workability

2.3 Development of Chloride Resistant Concrete

Cement W/C Total

Designed w/c, water and cement contents for XS3 exposure

PCEstimate StrengthEstimete D

Mix constituents, kg/m3Class designation Class description

Chloride exposure classes (BS 8500)

Combination W/C Water Total

Cement PC FA

PC 0.40 180 45045010% FA 0.40 174 435390 4530% FA 0 47 160 340240 100

PC Savings

60210

Strength N/mm2

535138

cm2/s×109

6.03 0

15.0– –

designation

Seve

rity

Chlorides other than from sea waterXD classesModerate humidityXD1Wet, rare dryXD2Cyclic wet and dryXD3 30% FA 0.47 160 340240 100

50% FA 0.44 150 340170 170210280

3833

3.01.5

S Cyclic wet and dryXD3Chlorides from sea waterXS classes

Not in direct contact with sea waterXS1Permanently submergedXS2Tidal splash and spray zonesXS3Se

verit

y

Relative cement cost analysis:550 110Tidal, splash and spray zonesXS3S

Group 4 CEM I CEM I+(6% 20%)FA

FA cements grouping with respect to chloride exposure

ost,

%

450

500

550

90

100

110

kg/m

3

Concrete required for XS3

Group 4 CEM I, CEM I+(6%-20%)FAGroup 5 CEM I+(21%-35%)FAGroup 6 CEM I+(36%-55%)FA

e C

emen

t Co

300

350

400

60

70

80

nt C

onte

nt, k

Total cement content

Cement Combination

Max. w/c

Min. Strength

Min. Cement kg/m3

PC (Group 4) 0.40C50 380

qwith nominal cover = 50 + c

Rel

ativ

200

250

300

40

50

60

Cem

en PC content Relative cement cost

( p )10% FA (Group 4) 0.40C50 38030% FA (Group 5) 0.50C35 34050% FA (Group 6) 0.50C30 340

FA content, %

1500 10 20 30 40 50 60

30

Assume Part 1 PFA price = 50% of PC price

Fly Ash: Durability of Concrete

E i t l d E i C id tiE i t l d E i C id ti

y yImproving Chloride Resistance

For equal chloride diffusion ffi i t

100910009 100910009

Environmental and Economic ConsiderationsEnvironmental and Economic Considerations

coefficient:

PC Concrete: 70 MPa(m2 /s

ec× 1

09

2 MP

cm2 /s

×10

25 MPa concrete(m2 /s

ec× 1

09

2 MP

cm2 /s

×10

25 MPa concrete PC Concrete: 70 MPa (w/c=0.30, PC=550kg/m3, PFA=0kg/m3)

10

effic

ient

(D )

c 25 MPa concrete

35 MPa concrete

10

cien

t, D

, 25 MPa concrete

35 MPa concrete

10

effic

ient

(D )

c 25 MPa concrete

35 MPa concrete

10

cien

t, D

, 25 MPa concrete

35 MPa concrete

PC55/FA45 Concrete: 25MPa(w/c=0 60 PC=145kg/m3, FA=125kg/m3)

1

usio

n C

oe 35 MPa concrete

50 MPa concrete1

on C

oeffi

50 MPa concrete1

usio

n C

oe 35 MPa concrete

50 MPa concrete1

on C

oeffi

50 MPa concrete(w/c 0.60, PC 145kg/m FA 125kg/m )

Potential for Cement Saving:0.10 10 20 30 40 50 60

Diff

u

60 MPa concrete70 MPa concrete

0.10 10 20 30 40 50 60

Diff

usio

60 MPa concrete70 MPa concrete

0.10 10 20 30 40 50 60

Diff

u

60 MPa concrete70 MPa concrete

0.10 10 20 30 40 50 60

Diff

usio

60 MPa concrete70 MPa concrete

g275 kg/m3

0 10 20 30 40 50 60% Fly Ash Content

0 10 20 30 40 50 60% Fly Ash Content

0 10 20 30 40 50 60% Fly Ash Content

0 10 20 30 40 50 60% Fly Ash Content

RKD1

Slide 21

RKD1 R K Dhir, 19/05/2009

2.4 Minimising ASR with EN 450 FA/CFA

h

Test Method Test Method –– ASR Expansion of ConcreteASR Expansion of Concrete0.20

in le

ngth

All dry FAs30% FA level

BS 812BS 812--123123

0.15

cha

nge Alkali content = 7.0 kg/m²

Gravel aggregate, max. size 20mm

Exposure: 38°C sealed above water

0.10ee

ks),

%

Exposure: 38°C, sealed above water

Expansion, PC Control=0.42%

0.05

(104

we p ,

0

ANSI

ON

(

0 10 20 30 40 50 60FA FINENESS, % 45 µm sieve retentionEX

PA

2.5 Properties of Fly Ash Mortar

Concrete StrengthConcrete Strength

120 35

60Equivalent flowFresh Concrete PropertiesFresh Concrete Properties

%

100

120Mortar designation II 30

35

TIVI

TY, %

40

50

mm

²

DEM

AN

D,

60

80

20

25E

RET

ENT

30

GTH

, N/m

WAT

ER D

40

60

10

15

SIST

ENC

E

20

STR

EN

W

20 5

10

CO

NS

0

10PCFA 30%FA 50%

400FA 50%MORTAR

PC FA 30%0

PC FA 30% FA 50%MORTAR

0 0 100 200 300

AGE, days

0

2.6 Foamed Concrete

Cube Strength, N/mm²Cube Strength, N/mm²Efflux Efflux Time, Time,

Foamed Foamed Concrete Concrete

1.91.91.91.91.71.71.41.41.21.25050PC RefPC Ref

90 d90 d56 d56 d28 d28 d7 d7 d3 d3 d,,

SecondSecondbbMixMixaaaa Fly ash was used to Fly ash was used to replace sand at 50% by replace sand at 50% by massmass

3 93 93 73 73 23 21 81 81 51 52020U2U22.72.72.62.62.22.21.61.61.31.32020U1U13.43.43.23.22.82.81.71.71.41.42525Raw AshRaw Ash

mass.mass.

bb <60 seconds: mix is <60 seconds: mix is flowing and selfflowing and self--3.93.93.73.73.23.21.81.81.51.52020U2U2 compactingcompacting

2.6 Foamed Concrete

Effect of Fly Ash on Density/ Strength RelationshipEffect of Fly Ash on Density/ Strength Relationship

55

60

Void-fill FC (Moorfield, 1994)Sand Mixes 28 days

40

45

50

/mm

²Sand Mixes, 28 daysFA Mixes, 28-daysFA Mixes, 56 days

25

30

35

Stre

ngth

, N/ W/C 0.30

15

20

25

ompr

essi

ve S

0

5

10Co

1400 1600 1800Design Plastic Density, kg/m³

2.7 Sulfate Resisting Fly Ash Grout0.10

STRENGTH*, N/mm²Exposure: Class 5

0.08

l len

gth

G1 34 5

G0 = 57.0Class 5

* 28 day lime water cured(70.7 mm cube)

0.06

% o

f ini

tial

G2 = 19.5

G1 = 34.5

0.04

NSI

ON

, %

G3 = 13.0SRC G0 = 55.0

0.02EXPA

N

G5 = 6.5

0G10 = 3.5

12 240 631

EXPOSURE PERIOD, months (log scale)

2.8 Conditioned Fly Ash Activated Sand

70PC 450 k / ³ CPFA

Strength PerformanceStrength Performance

60

PC: 450 kg/m³ CPFA

CPFASand

50CPFA

PC: 350Sand

30

40 CPFAPC: 250

Sand

20

0

1010% sand replacement0 10 20 30 40 50 60 70 80 90

AGE, days

0 replacement

2.9 Lime Stabilization of Soils with Fly Ash

15

3% lime, 1 day mellowing, 7 days in water at 40ºC

15

G, %

_ 3% lime, 1 day mellowing, 7 days in water at 40ºC

10

WE

LLIN Kimmeridge Clay, SO3 = 1.0%

FA3-1, fine5ETR

IC S

W

Generally accepted safe limit

FA7, coarse

Generally accepted safe limit

5

VO

LUM

E FA, fine

FA coarseGGBSGGBS0

0 6 12 18 24

V FA,coarseGGBS

ADDITION CONTENT, %

3. Multi-Blended Cements with Fly Ash

STRENGTH N/mm2

CEMENT w/c 0.65 w/c 0.55 w/c 0.45

PC / 30%FA 22.5 29.0 39.5

PC / 25%FA / 5%LS 22 0 28 0 39 0PC / 25%FA / 5%LS 22.0 28.0 39.0

PC / 25%FA / 5%MK 23.5 30.5 42.0

PC / 25%FA / 5%SF 25.0 33.0 45.0

3. Multi-Blended Cements with Fly Ash

8

PC and PC/PFA controlWater

5

6

7 PC and PC/PFA control

PC/GBS/SF

Water cured

3

4

5

20 N/mm 260 N/mm 240 N/mm 2

1

2

3

0

1

CONCRETE MIX

Concluding Remarks

The CTU model of working in partnership with all the g p pstakeholders, including government and industry, has made it possible for University research to be p yinnovative and practical and thereby facilitate maximising the use of fly ash as a valuable resource in g yconcrete construction and, in so doing, it can claim to be a major player in enabling sustainable use of cement j p y gin concrete construction, in terms of reducing significantly its carbon footprint and enhancing concrete g y p gdurability.