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
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini4
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
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini5
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)
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini6
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
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini7
Geopolymers from FeNi slagResults and discussion
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
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini8
Geopolymers from FeNi slagResults and discussion
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
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini9
Geopolymers from FeNi slagResults and discussion
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
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini10
Geopolymers from FeNi slagResults and discussion
Potassium Iron
AluminumSilicon
Slag-glass geopolymer 50% w/w
G: glass grainsS: slag grainsB: geopolymeric gel
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini11
Geopolymers from FeNi slagResults and discussion
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:
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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
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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
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GRINDING MIXING CASTING CURINGmaterials
SH
SS
GLS(below 125µm)
Geopolymers from lead slagResults and discussion: Crystalline phases
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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)
28/04/2011Second International Slag Valorisation Symposium│
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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
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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
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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
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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
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
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini30
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
28/04/2011Second International Slag Valorisation Symposium│ K. Komnitsas, I. Kourti, S. Onisei, Y. Pontikes, C. Cheeseman,
P. Moldovan, A. Boccaccini31
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.
28/04/2011Second International Slag Valorisation Symposium│
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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