Effect of SCMs on hydration kinetics of cementitious systems

International Summit on Cement Hydration Kinetics 1

Ecole Polytechnique Fédérale de Lausanne

Swiss Federal Institute of Technology in Lausanne

Effect of SCMs on hydration kinetics

of cementitious systems

Laboratory of Construction Materials

Vanessa KOCABA and Karen SCRIVENER


↓ CO2

Cement industry

Clinker

Natural pozzolanSilica fumeFly ash

Process optimisation ↓ clinker factor

Gypsum Cement

SCMs

same or higher performance

[Hogan et al., 1981]

40% slag

No slag

Slag

Effect of SCMs on hydration and microstructure

Introduction


OPC + water C-S-H + CH + other hydrates

Hydraulic reaction

Pozzolanic reaction

Pozzolan + CH + water C-S-H + other hydrates

Rate influenced by:

Surface area: fine

pozzolan (e.g. silica fume)

react more rapidly

Glass composition:

high-calcium fly ash reacts

more quickly

Temperature

pH: glass phases are

more soluble at high pH

and reacts more quickly.

Strong influence of the

concentration of alkalis

More space available

More surface for C-S-H

precipitation

CH

CH

Definitions-Hydraulic & pozzolanic reactions

Mainly responsible for strength

Impermeability of concrete

More strength

slag + water C-S-H + other hydrates

Reactions where water is combined increase the solid volume, fill pores, increase strength


SiO2

Portland Cement

Al2O3CaO

Slag

Fly Ash

C

Natural pozzolan

SilicaFume

Limestone

Metakaolin

F

Chemical composition of various SCMs



IncreasingCalciumContent

Nature of the reaction of different SCMs

Pozzolanic effect Hydraulic effect

Silica fume

Type F-Fly ash-Low CaO

Fly ash-Medium CaO

Type C Fly ash-High CaO

Slag

Metakaolin, clay

Cement


International Summit on Cement Hydration Kinetics

Impact of SCMs on Hydration

Impact of SCM on Hydration of Cement:

FILLER EFFECT

1. more space due to dilution by SCM

2. Surface acts as nucleation site for hydrates

As most SCM react little in the first day these effects can be studied by calorimetry

Reaction of SCMs themselves

Measurement is the big issue

6


FILLER EFFECT 1 – particles similar size to cement grains

Cement with and without 30% fine ground quartz

(d50=15 µm) (assumed non reactive),

7

Heat

evolu

tion

time 1 day 20 days

Cum

ula

tive h

eat

referencewith 30% quartz

Thesis Rodrigo Fernadez 2009normalised by cement content


FILLER EFFECT 1 – particles similar size to cement grains

8

Heat

evolu

tion

time 1 day 20 days

Cum

ula

tive h

eat

Acceleration part not affected:minimal influence of quartz surface on nucleation and growth

Time to peak extended,

more space for hydrates delays onset

of decceleration

Enhancement of cement hydration

Typically +5%At long ages

Thesis Rodrigo Fernadez 2009


0 5 10 15 20 25 30 35 40 45 500

1

2

3

4

5

6

7

100% Cement

90% Cement-10% SF

Heat

(mW

.g-1 o

f cem

en

t)

T ime (hours)

SCM acts as nucleation sites for C-S-H growth

FILLER EFFCT 2 – fine particles, silica fume

Enhances kinetics in acceleration period

surface for nucleation

[V.Kocaba, 2008]


Reaction of Slag. Thesis Vanessa Kocaba,

10


Isothermal calorimetry

Filler effect?Influence of slagon clinker reaction:-Enhancement of hydration evolution of C3S -Impact on aluminatephases


Phase assemblage: model cement properly sulfated

P 92/8_ 4.1G


Phase assemblage: model cement properly sulfated

M 92/8_ 4.1G


Impact of slag

Small evidence of filler effect 1 (extra space)

No evidence of extra nucleation, filler effect 2

Large evidence of “aluminate” reaction

– varies with cement type

16


Effect of slag on cement hydration at early ages

0 10 20 30 40 50 60 70 800.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5N

orm

ali

sed

heat

(mW

.g-1of

cem

en

t) B

B-S1

B-S1-1% Gypsum

B-S1-2% Gypsum

B-S1-3% Gypsum

B-S1-4% Gypsum

Time (hours)

Calorimetry with Gypsum addition to separate peaks


0 10 20 30 40 50 60 70 800,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5N

orm

ali

sed

hea

t

(mW

.g-1of

cem

ent)

B-S1-2% Gypsum

Time (hours)

Aluminate from cement?Or from slag?

Silicate


Calorimetry with Gypsum addition to separate peaks



0 10 20 30 400

1

2

3

Time (hours)

Heat

(W

.kg

-1)

Corundum

Rutile

Quartz

[Le Saout, Ibausil, 2006]

Filler effect

Filler effect also with other powders


Additions have different effects on the nucleation of the

calcium silicate and calcium aluminate hydrates.

Most additions seem to have minor impact on calcium

silicate nucleation and growth (exception is silica fume)

Nearly all fillers seem to have a major influence on second

reaction period of aluminates

(maybe by affinity to absorb sulfate)

20


Measurement of degree of reaction

Vanessa Kocaba, CP4

21


How to measure the reactivity of slag

• Selective dissolution

• Recrystallisation by DSC

• SEM-Image analysis on BSE and

mapping

• Isothermal calorimetry

• Chemical shrinkage


A -S8 1 day 71.6 ± 1.8 -79.0 ± 4.4 63.5 ± 4.4

B-S8 1 day 66.5 ± 1.8 -66.3 ± 4.6 76.2 ± 4.6

C-S8 1 day 65.2 ± 5.8 -63.1 ± 14.6 79.4 ± 14.6

A -S8 90 days 72.8 ± 4.2 -82.0 ± 10.5 60.5 ± 10.5

B-S8 90 days 77.4 ± 3.5 -93.5 ± 8.8 49.0 ± 8.8

C-S8 90 days 70.1 ± 4.0 -75.1 ± 9.9 67.4 ± 9.9

Samples

U ndissolved

materials

(%)

(%init ial slag-%undissolved materials)

%init ial slag

D egree of hydrat ion of slag

[Luke et al., 1987]

Corrected

Selective dissolution: results

Remaining undissolved phases of cement

(even after some modifications of the procedure)

Position [°2 CuKα]

10 20 30 40 50 60

Ca

lcit

e +

C-S

-H

C2S

C2S

C2S

CH

CH

CH

CH

CH

CHC

alc

ite

C2S

C2S

Cement B 90 days

C2S

Ca

lcit

e +

C-S

-H

C2S

Cement B-Slag 8 90 days after SD

Mo

no

carb

o

Me

lili

te

Me

lili

teM

eli

lite

Me

lili

te

Me

lili

te

Me

lili

te Me

lili

te

C2S

Hy

dra

talc

ite

CH

CH

C2S

CHC

2S

CH

CH

C2S

CH

CH

Position [°2 CuKα]

10 20 30 40 50 60

Ca

lcit

e +

C-S

-H

C2S

C2S

C2S

CH

CH

CH

CH

CH

CHC

alc

ite

C2S

C2S

Cement B 90 days

C2S

Ca

lcit

e +

C-S

-H

C2S

Cement B-Slag 8 90 days after SD

Mo

no

carb

o

Me

lili

te

Me

lili

teM

eli

lite

Me

lili

te

Me

lili

te

Me

lili

te Me

lili

te

C2S

Hy

dra

talc

ite

CH

CH

C2S

CHC

2S

CH

CH

C2S

CH

CH

XRD results SEM results


Selective dissolution: conclusion

Not able to dissolve

all cementitious phases

except slag

Selective dissolution






mapping




Recrystallisation by DSC: principle

Recrystallise slag at high temperatures (>800°C)

Hypothesis: all amorphous slag recrystallises

Quantify the corresponding peak

Slag 1 Slag 2 Slag 3

MgO 4.7 8.4 8.2

Al2O3 14.6 12.2 11.9

SiO2 33.9 33.6 35.1

CaO 44.5 42.5 42.8

Na2O 0.24 0.26 0.3

S 0.33 1.7 0.37

K2O 0.62 0.45 0.61

TiO2 0.69 0.49 0.59

MnO 0.66 0.55 0.37

FeO <0.1 0.12 0.09

Melilite(C2AS + C2MS2)

Merwinite(C3MS2)

[Regourd, 1980]


Recrystallisation by DSC: results

Results


296 J/g DH= 0%


Results



8 J/g DH= 93%

A-S8 7d

unrealistic!

Results


Recrystallisation by DSC: conclusion

DSC

All amorphous slag does not recrystalliseInterference with belite






mapping




Image analysis of BSE

0 50 100 150 200 250

AN

Slag 8 CH

CSH

For Cements-Slag 1& 8

Slag 8 CH

Overlap between CH and Slag 8 grey levels

Grains of slag as a function of

its chemical composition

Isolate Slag 8 and CH?Similar BS coefficients

Different chemical elements

Degree of hydration

Reactivity of slag-SEM-IA-mapping

Map of Mg

Needs fast detector to be practical


0 5 10 15 20 25 30 35 200 400 6008000

10

20

30

40

50

60

70

80

90

100

A-S1

A-S8

Degre

e o

f re

acti

on

of

slag (

%)

T ime (days)

0 5 10 15 20 25 30 35 200 400 6008000

10

20

30

40

50

60

70

80

90

100

Degre

e o

f re

acti

on

of

slag (

%)

T ime (days)

B-S1

B-S8

0 5 10 15 20 25 30 35 200 400 6008000

10

20

30

40

50

60

70

80

90

100

C-S1

C-S8

Degre

e o

f re

acti

on

of

slag (

%)

T ime (days)

For all the Cementitious systems, the slag S8 is always more reactive than slag S1

Reactivity of slag-SEM-IA-mapping

Degree of reaction of slag


Outline

SEM (BSE-IA-mapping)

→ gives realistic range with errors which be reduced with

new EDS detector


→ gives realistic range

→ needs more investigation on calibration (enthalpy of

slag or external method)

Recrystallisation of slag by DSC

→ problematic due to huge background contribution

How to quantify the degree of reaction slag?

C-S-H composition: indicator of reactivity






mapping




Isothermal calorimetry: use of inert filler

Tests on B systems with an inert filler (quartz)as a reference

0 4 8 12 16 20 24 280

100

200

300

400

500

600

700

800

C

um

ula

tiv

e h

eat

(J.g

-1 o

f cem

en

t)

T ime (days)

100% B

60% B-40% Q

Filler effect


0 4 8 12 16 20 24 280

100

200

300

400

500

600

Cu

mu

lati

ve h

eat

(J.g

-1 o

f cem

en

t)

T ime (days)

100% B

60% B-40% Q

60% B-40% S1

60% B-40% S8

Filler effect

Contribution of S1 S8

Method: subtract filler effect to blended curve in order to isolate

the contribution of the slag

Reactivity of slag-Isothermal calorimetry



0 5 10 15 20 25 30 35 400

1

2

3

4

Heat

(W.k

g-1 o

f cem

en

t)

T ime (hours)

100% B

60 % B-40% Q

60 % B-40% S1

60 % B-40% S8

0 4 8 12 16 20 24 280

100

200

300

400

500

600

Cu

mu

lati

ve h

eat

(J.g

-1 o

f cem

en

t)

T ime (days)

100% B

60% B-40% Q

60% B-40% S1

60% B-40% S8

0 4 8 12 16 20 24 280

50

100

150

200

250

300

350

400

Time (days)

Su

btr

ated

cu

mu

lati

ve h

eat

curv

es (

J.g-1

of

cem

ent)

B-S1

B-S8

Early age to treat

with deconvoltion

approach to isolate

the contribution of

different phases

System A



0 5 10 15 20 25 30 35 400

1

2

3

4

5

6

7

8

Heat

(W.k

g-1 o

f cem

en

t)

T ime (hours)

100% A

60 % A-40% Q

60 % A-40% S1

60 % A-40% S8

70 % A-30% FA1

70 % A-30% FA2

90 % A-10% SF

0 4 8 12 16 20 24 280

100

200

300

400

500

600

Cu

mu

lati

ve h

eat

(J.g

-1 o

f cem

en

t)

T ime (days)

100% A

60% A-40% S1

60% A-40% S8

60% A-40% Q

0 4 8 12 16 20 24 280

50

100

150

200

250

300

350

400

Time (days)

Dif

fere

nce o

f cu

mu

lati

ve h

eat

cu

rves

(J.g

-1 o

f cem

en

t)

A-S1

A-S8

System B



0 5 10 15 20 25 30 35 400.0

0.5

1.0

1.5

2.0

2.5

3.0

Heat

(W.k

g-1 o

f cem

en

t)

T ime (hours)

0 4 8 12 16 20 24 280

100

200

300

400

500

600

Time (days)

Cu

mu

lati

ve h

eat

(J.g

-1 o

f cem

en

t)

100% C

60% C-40% S1

60% C-40% S8

60% C-40% Q

70 % C-30% FA1

70 % C-30% FA2

70% C-30% Q

90% B-10% SF

0 4 8 12 16 20 24 280

50

100

150

200

250

300

350

400

Time (days)

Su

btr

ate

d c

um

ula

tiv

e h

eat

cu

rves

(J.g

-1 o

f cem

en

t)

C-S1

C-S8

System C


Outline

SEM (BSE-IA-mapping)

→ gives realistic range with errors which be reduced with

new EDS detector


→ gives realistic range

→ needs more investigation on calibration (enthalpy of

slag or external method)

Recrystallisation of slag by DSC

→ problematic due to huge background contribution

How to quantify the degree of reaction slag?

Combine both to calibrate the calorimetry curves

C-S-H composition: indicator of reactivity


Reactivity of slag-Isothermal calorimetry calibrated by SEM

Method to calibrate isothermal calorimetry curves

0 4 8 12 16 20 24 280

50

100

150

200

250

300

Time (days)

Dif

fere

nce o

f cu

mu

lati

ve h

eat

cu

rves

(J.g

-1 o

f cem

en

t)

0

5

10

15

20

25

30

35Slag 1 D

egre

e o

f reactio

n o

f slag

from

SE

M/IA

-map

pin

g (%

)

0 4 8 12 16 20 24 280

50

100

150

200

250

300

350

400

Time (days)

Dif

fere

nce o

f cu

mu

lati

ve h

eat

cu

rves

(J.g

-1 o

f cem

en

t)

0

10

20

30

40

50

60

70

Degre

e o

f reactio

n o

f slag

from

SE

M/IA

-map

pin

g (%

)

Slag 8


Isothermal calorimetry: conclusions

Gives continuous measurements of

realistic degrees of reaction of the slag


But several hypotheses!The difference of cumulative curves of filler and slag

is attributed only to the contribution of slag

The heat of solution of slag concerns pure slags and does not correspond to the one activated by alkaline






mapping




Isothermal Calorimetry(TAM Air, Thermometric) at a temperature of 20.0 0.1ºC

Ex-situ mixing

8 samples / 60 k$ instrument

Chemical Shrinkage(Dilatometry)

20 samples / 5 k$ instrument

Backscattered electron/Imageanalysis (BSE/IA)

1 sample / 300 k$ instrument

Methodology


Chemical shrinkage-results

0 4 8 12 16 20 24 280.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

Ch

em

ical

shri

nk

age

(mL

/g o

f cem

en

t)

T ime (days)

100% A

60% A-40% S1

60% A-40% S8

0 4 8 12 16 20 24 280.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

Ch

em

ical

shri

nk

age

(mL

/g o

f cem

en

t)

T ime (days)

100% B

60% B-40% S1

60% B-40% S8

0 4 8 12 16 20 24 280.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.11

Ch

em

ical

shri

nk

age

(mL

/g o

f cem

en

t)

T ime (days)

100% C

60% C-40% S1

60% C-40% S8

S1>S8 S1<S8

S1<S8 Discrimination between 2 slags but needs to be corrected by filler effectFind a method of calibration to link the curve to degree of reaction of slag


Conclusions: How to measure the reactivity of slag?

Selective dissolution does not work

DSC does not recrystallise completely the slag

Combine both to calibrate the calorimetry curves

SEM (BSE-IA-mapping) gives realisticrange but large errors which will berefined

Isothermal calorimetry gives realisticrange but needs more investigation oncalibration

Chemical shrinkage give continuousmeasurements but needs to becalibrated with an external method

In progress, check on calorimetry


Summary

SCMs similar in size to cement effect of silicate is

mostly dilution

Effect on alumino sulfate reactions dramatic and

not completely explained

Very fine fillers, e.g. Silica fume indicate

enhanced nucleation effect

To study kinetics of SCM, challenge is

measurement

Calorimetry and chemical shrinkage look promising as continuous methods, questions of calibration

48


www.nanocem.org

http://www.nanocem.org/


www.conmod10.org

21-22 June

Users workshop

Also hopefully 2nd ½ July in North America

http://www.conmod10.org/pages/conditions.html

http://www.conmod10.org/

Effect of SCMs on hydration kinetics of cementitious systems

Documents

Transcript of Effect of SCMs on hydration kinetics of cementitious systems