GEOPOLYMERISATION POTENTIAL OF METALLURGICAL SLAGS … · Geopolymers from plasma treated APC residues APC residues FLY ASH AIR POLLUTION CONTROL (APC) RESIDUES INCINERATOR BOTTOM

GEOPOLYMERISATION POTENTIAL OF METALLURGICAL SLAGS AND PLASMA TREATED APC RESIDUES

K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman, P. Moldovan, A. Boccaccini

Content:

Geopolymers from FeNi slag

Geopolymers from lead slag

Geopolymers from plasma treated APC residues

Conclusion

28/04/20112Second International Slag Valorisation Symposium│

K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman, P. Moldovan, A. Boccaccini

28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,

P. Moldovan, A. Boccaccini3

Geopolymers from FeNi slagFeNi slag

Electric arc slag is produced at LARCO S.A. ferronickel plant in Greece

Annual slag production reaches 1,700,000 t; cement industry uses 450,000 t

Slags are currently disposed of on surface heaps or under the sea

Slag was dried and crushed (-120 μm and d50: -12 μm) to increase surface area

% % %

Fe2O3 43.83 Cr2O3 3.07 C 0.11

SiO2 32.74 MgO 2.76 Ni 0.1

Al2O3 8.32 Mn3O4 0.44 Co 0.02

CaO 3.73 S 0.18



Geopolymers from FeNi slagSynthesis

Activating solution

Na2SiO3 + KOH pellets + water

Pulverised slagHomogeneous

paste+

The paste was cast in moulds (5 cm edge)

Specimens were pre-cured at room temperature for 2 days before heated at 80 oC for 48 hours

Aging took place for 7 days at room temperature



Geopolymers from FeNi slagTests

Long term durability:- immersion in distilled, seawater, acid rain and 0.05N HCl solutions for a max period of 8 months

- pH, Eh, EC and metal ion concentration were monitored monthly

- weekly freeze-thaw cycles (-15 and +60 oC) and high temperature heating up to 800 oC

Compressive strength was measured using an MTS 1600 load frame

Elucidation of geopolymerisation mechanisms by analytical techniques (XRD, SEM, FTIR, TG)



Geopolymers from FeNi slagResults and discussion

Evolution of the compressive strength of geopolymers immersed in various solutions or subjected to freeze-thaw cycles over 8 months

0

10

20

30

40

50

60

70

Control 1 2 4 6 8

Months

Co

mp

ress

ive

stre

ngth

, M

Pa t

t

Control Freeze-thaw Distilled waterSeawater Acid rain HCl 0.05N




Evolution of the compressive strength of geopolymers vs. temperature

0

15

30

45

60

0 100 200 300 400 500 600 700 800

Temperature, oC

Com

pre

ssiv

e st

rength

, M

Pa

Control

8 Μ ΚΟΗ, 8% Na2SiO3 - 2d, 80 οC, 48 h, 7 d




pH vs. time when geopolymers are immersed in various solutions

1

3

5

7

9

11

0 1 2 3 4 5 6 7 8

Months

pH

Distilled water SeawaterHCl 0.05N Acid rain

0

30

60

90

120

150

180

0.06 0.5 1 2 3 4 5 6 7 8

Months

mg

/L

0

500

1000

1500

2000

2500

3000

mg

/L

Mn Fe Ca Ni Mg Al Si Cr Na K

HCl 0.05N

Dissolution of Mn, Fe, Ca, Ni, Mg, Cr, Na, K, Al and Si (mg/L) when geopolymers are immersed in 0.05N

HCl solution




XRD patterns of geopolymers subjected to high temperature heating (P80, P200 and P800 heated at 80, 200, 800 oC, respectively)

(Q: quartz, K: kaolinite, M1: magnetite, M2: maghemite, F: fayalite, CSH: calcium silicate hydroxide, D: diopside, T: tridymite, H: hematite, N: NaAl11O17)

2-Theta - Scale

5 10 20 30 40 50 60

P80

P200

P800

Q

QM1

M2M1M1

M1

M2M2

M2

M1

M1

M1

M1

K

K

D

D

D

H

H

CSH

CSH

F

FT

M2

D

D

DD

HN




Potassium Iron

AluminumSilicon

Slag-glass geopolymer 50% w/w

G: glass grainsS: slag grainsB: geopolymeric gel




FTIR spectra of slag, glass and G80 glass-based geopolymer, SG80 slag-glass geopolymer

glass

slag

763

3713

G80

458

530

1002

SG801402

1627

2338

3455

350 850 1350 1850 2350 2850 3350 3850

Wavelength, cm-1

Infrared absorption bands identification of bonds

Asymmetric stretching vibration T–O–Si (T:Si ή Al) [950-1200 cm-1]

In plane Si–O bending and Al–O linkages [460-465 cm-1]

Atmospheric carbonation or/and Na2CO3 [1410-1570 cm-1]

Geopolymers from lead slagIntroduction

Production of lead slag:

Fly ash is also used in order to compensate the small amount of Si-, Al- source in lead slag

Production of fly ash:


K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman, P. Moldovan, A. Boccaccini12

Lead concentrate

OXIDATION IN AUTOCLAVE Oxidised

lead concentrate

MELTING

Leadslag

Lead

COMBUSTIONLignite

Fly ash

Bottom ash

Energy

Gaseous wastes

Solid wastes

Geopolymers from lead slagMaterials



0.1 1 10 100

0

10

20

30

40

50

60

70

80

90

100 slag (m):

d10=4.6

d50=37.1

d90=116.3

cum

ula

tive (

%)

size (m)

slag

fly ash

fly ash (m):

d10=0.5

d50=4.4

d90=32.2

Slag Fly ash

Litharge, PbO Quartz, SiO2

Wuestite, FeO Gehlenite, Ca2Al2SiO7

Sodium aluminium

silicate, Na6Al4Si4O17

Magnetite, Fe3O4

Magnetite, Fe3O4 Anorthite, CaAl2Si2O8

Sodium zinc silicate,

Na2ZnSiO4

Anhydrite, CaSO4

SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O SO3 PbO

Slag 21.58 1.71 35.9 2.78 0.2 15.83 0.3 8.3 13.4

Fly ash 51.4 23.5 7.73 9.21 1.69 0.89 1.45 2.66 -

Mixture Fly ash Slag SS SH S/W Si/Al

GL28 71.8 28.2 25.4 20.8 3.59 5.04

GL51 48.9 51.1 22.0 15.7 4.31 5.97

GL70 29.8 70.2 19.4 11.5 5.19 7.63

GL86 13.8 86.2 17.2 8.0 6.31 11.3

Geopolymers from lead slagSample preparation



GRINDING MIXING CASTING CURINGmaterials

SH

SS

GLS(below 125µm)

Geopolymers from lead slagResults and discussion: Crystalline phases



10 20 30 40 50 60 70

Pb

SA

S

SLC

H

Ma

SZ

S

SLC

H

Wu

SA

SW

u

Li

Li

Li

Li

Li

Li

SLC

H

anhy

drite

Ma

Ma

Ge

Ca

Ant

Qu

QuQu

Qu

Fly ash

Slag

Inte

nsit

y, a

.u.

2theta, (o)

GLS100

GLS70

GLS51

GLS0

Qu-quartz , An-anorthite , Ma-magnetite, Ge-gehlenite Ca-calcite, Li-litharge , SAS-sodium aluminium silicate

Wu- wuestite , SZS-sodium zinc silicate, Pb-lead

Fly ash

Phase Before After

Anorthite Y Y

Gehlenite Y Y

Magnetite Y Y

Quartz Y Y

Anhydrite Y N

Calcite N Y

Slag

Phase Before After

Litharge Y traces

Wüstite Y Y

Sodium aluminium silicate Y Y

Magnetite Y Y

Sodium zinc silicate Y Y

Sodium lead carbonate hydrate (after storing)



1000 3000 4000

GLS51

GLS100

GLS70

Fly ash

GLS0

Slag

Tra

nsm

itta

nce

%

Wavenumber, cm-1

•The sharpening and shifting of the main band for the geopolymer with 100% fly ash, attributed to asymmetric stretching vibrations of Si – O – Si and Al – O – Si, indicates the formation of the aluminosilicate gel•When only lead slag was used, the FTIR pattern of the geopolymers produced appears almost identical to the raw material•For specimens produced using both fly ash and lead slag as the percent of slag in the body increases, the IR patterns resemble more the 100% slag geopolymer

Geopolymers from lead slagResults and discussion: Bonds characteristics

Geopolymers from lead slagResults and discussion: physical properties



20 30 40 50 60 70 80 90

10

20

30

40

50

60

Compressive strength, MPa Flexural strength, MPa

Slag, wt.%

Co

mp

ress

ive

stre

ng

th,

MP

a

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

Flex

ural stren

gth

, MP

a

20 30 40 50 60 70 80 90

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

Slag, wt.%

Bu

lk d

en

sity

, g/c

m3

16

18

20

22

24

26

28 Density, g/cm

3 Water absorption%

Wate

r ab

sorp

tion

,%

Geopolymers from lead slagResults and discussion: Microstructure



GL

GL

GL

GL

GL

GL

GL

Fe oxide

Q Q Q

Q

GL

Pb Fe oxide

100 μm

GLS51 GLS51

GLS70GLS70

Geopolymers from lead slagResults and discussion: Leaching



5 6 7 8 9 10 11 12 13

0

20

40

60

80

100

Pb (

ppm

)

pH

Pb AA

Pb raw

5 6 7 8 9 10 11 12 13

0

5

10

15

20

25

Al (p

pm

)

pH

Al AA

Al raw

Decreased leaching

5 6 7 8 9 10 11 12 13

0.1

1

10

100

1000

10000

Na (

ppm

)

pH

Na AA

Na raw

5 6 7 8 9 10 11 12 13

1

10

100

Si (p

pm

)

pH

Si AA

Si raw

Increased leaching

Geopolymers from plasma treated APC residuesAPC residues

FLY ASH

AIR POLLUTION CONTROL (APC)

RESIDUES

INCINERATOR BOTTOM ASH (IBA)

APC RESIDUES

•Hazardous waste from cleaning gaseous emissions

•Mixture of lime, fly ash and carbon

•Fine particles removed by high efficiency filters

•Issues with APC residues are:

•Heavy metals

•High alkalinity

•High soluble salt content, particularly leachable chloride (Cl-)

SELCHP Energy from Waste facility, London

http://upload.wikimedia.org/wikipedia/commons/9/9f/SELCHP.jpg

Geopolymers from plasma treated APC residuesAPC residue plasma derived glass

DC plasma treatment of APC residues blended with SiO2

and Al2O3 → Volume reduction ~70–75%

Amorphous aluminosilicate glass

Dark green colour

Inert material

cms

Research aim: Use APC glass as raw material for geopolymer’s production

Geopolymers from plasma treated APC residuesPreparation of geopolymers

Activating Solution

Water

Alkali Source (NaOH)

Silicate Source(Sodium silicate solution)

1. Preparation of activating solutions:

2. Preparation of mix:

Mixing BowlAPC glass (SiO2 = 41.1%, CaO = 32,6%, Al2O3 = 14.8%)

Activating Solution

3. Mixing for 10min

4. Casting in rectangular moulds

5. Curing in the moulds for 24hr

6. Samples ready for further curing

80x25x25 mm

(Compressive strength sample 40x25x25 mm)

Geopolymers from plasma treated APC residuesResults and discussion

Strong and dense geopolymers over a wide range of S/L ratios

Process highly affected by:

Particle size distribution of APC glass: Fine particles improve early compressive strength

Broad particle size distribution of APC glass powder improves later strengths

NaOH concentration in the activating solution: [NaOH] up to 10M → High strength geopolymers

Geopolymers from plasma treated APC residuesResults and discussion

Optimum APC glass geopolymer’s composition: Si/Al = 2.6

S/L = 3.4

[NaOH] = 6M in the activating solution

Properties of APC glass geopolymers: Very high strength (110 MPa @ 28 days)

High density (2300 kg/m3)

Low porosity and water absorption

No leaching of heavy metals

High acid resistance

High freeze-thaw resistance

Not a pure geopolymer

Geopolymers from plasma treated APC residuesComposite microstructure of APC glass geopolymers

Material resembles a particle reinforced composite

Geopolymer-glass composite

Unreacted APC glass have a strengthening and toughening effect

Crack deflection

mechanism

Geopolymers from plasma treated APC residuesBinder phase characterisation

APC glass geopolymer contains both geopolymer gel incorporating calcium and hydration products

High compressive strength can be attributed to:

Calcium present in the material

Microstructure with the unreacted APC glass particles acting as rigid inclusions.

Similarities with both metakaolin and GGBFS geopolymers

Geopolymers from plasma treated APC residuesPotential applications

Properties similar or better than concrete, cement geopolymer and some types of tiles

Potential applications:

Replacement of cement or concrete in non-structural applications (eg. Pre-cast products, paving blocks)

Tile production

Hazardous and toxic waste management (Further research)

Further testing is required for commercial applications

Geopolymers from plasma treated APC residuesCarbon footprint

Carbon footprint assessment based on Greenhouse Gas Protocol

Comparison with similar material prepared with Portland cement

Plasma process: Higher energy consumption than alternative APC residues management

options

Proven technology which maximises resource efficiency

DC plasma process on-site WtE plant: On-site solution for APC residues

Minimises carbon footprint of process (renewable energy used)

Economically attractive. Cost of process independent of energy price variations

Geopolymers from plasma treated APC residuesCarbon footprint

CF of APC glass geopolymer and PC material is affected: Additional materials used

Milling (if required)

Reuse of APC glass in geopolymers → Savings in use of natural resources

Carbon footprint

0,598

0,676

0,54

0,56

0,58

0,6

0,62

0,64

0,66

0,68

0,7

APC glass geopolymer Portland cement material

To

nn

es C

O2/

ton

ne o

f p

rod

uct

~12% CO2 savings

Reuse of APC glass in geopolymers helps to mitigate climate change as CO2

emissions are significantly lower compared to Portland cement use



Conclusions

Geopolymerisation potential of low Ca FeNi slags (high compressive strength ~60 MPa is seen for optimum Si/Al ratio)

Geopolymers exhibit very good behaviour in various aggressive environments, over a period of 8 months- sustain temperature variations between -15 & 60 οC

- immersion in distilled water does not practically affect strength

- immersion in seawater, acid rain or 0.05N HCl solutions decreases strength gradually but still remains above 30 MPa after 8 months

Analytical techniques (XRD, SEM, FTIR, TG) may be used to elucidate mechanisms involved



Geopolymers from FeNi slagConclusion

Geopolymers can be made from 100% fly ash, 100% lead slag and mixtures of them

The main change occurring after geopolymerisation revealed by XRD and IR is that litharge and calcium sulphate dissolve and a new amorphous aluminosilicate gel phase is formed.

The system of larger particles originating from lead slag in a geopolymeric matrix mainly derived from fly ash, behaves as a composite structure, where the larger particle act as rigid inclusions and contribute in crack deflection during crack propagation.



Geopolymers from lead slagConclusion

Geopolymers from plasma treated APC residuesConclusion

Plasma treated APC residues is a raw material suitable for geopolymers’ production

Formed amorphous, high strength geopolymer-glass composites

Unreacted APC glass particles are embedded in the binder phase and provide reinforcement

The binder phase contains both geopolymer gel incorporatingcalcium and hydration products

Existence of both phases contributes to the excellent properties of the material

Carbon footprint of APC glass geopolymers in ~12% lower than similar products from Portland cement

Documents

GEOPOLYMERISATION POTENTIAL OF METALLURGICAL SLAGS … · Geopolymers from plasma treated APC residues APC residues FLY ASH AIR POLLUTION CONTROL (APC) RESIDUES INCINERATOR BOTTOM