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Fly ash in cement and concrete composition
Zbigniew Giergiczny
Silesian University of Technology, Gliwice, PolandTechnological Center Betotech , Ltd.
April, 24–25 2014, Moscow
Subject of presentation
• Definition of fly ash• Classification of fly ash• Fly ash as a cement component• Fly ash as an additive for concrete• Summary
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Fly ashFly ash – is one of the residues resulted from hard coal or brown coal dust combustion in various types of furnaces in the power or heat and power plants.
FLY ASHZ b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Classification of fly ash
Fly ash can be classified according to:• chemical composition,• amorphous and crystalline phase content,• fineness (sieve residue),• unburned carbon content (loss on ignition).
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Classification of fly ash
FLY ASH
SILICEOUS
SILICEOUS - ALUMINOUS
CALCAREOUS(siliceous - calcareous)
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Fly ash as a cement component
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Fly ash according to cementitious standard EN 197-1
Fly ash is obtained by electrostatic or mechanical precipitation of dust-like particles from the flue gases of furnaces fired with pulverised coal. The ash obtained by other methods should not be used in the cement according to EN 197-1. Siliceous fly ash (V) is a fine powder of mostly spherical particles having pozzolanic properties.It consists essentially of reactive silicon dioxide (SiO2) and aluminium oxide (Al2O3). The remainder contains iron oxide (Fe2O3) and other compounds.Requirements:• reactive calcium oxide (CaO) max. 10,0 %• reactive silicon dioxide content min. 25,0 %• content of loss on ignition (unburned carbon):
• cat. A ≤ 5,0 %,• cat. B ≤ 7,0 %,• cat. C ≤ 9,0 %.
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Siliceous fly ash (V)
• Spherical grains of a high content of the glassy phase• High fineness (specific surface area from 250.0 to 450.0 m2/kg)• Pozzolanic properties
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
• Very fine powder having pozzolanic properties and/or hydraulic,• It consists of reactive calcium oxide (CaO ≥ 10 %), silicon dioxide
(SiO2) and aluminium oxide (Al2O3). The remainder contains iron oxide (Fe2O3) and other compounds,
• It contains more phases than siliceous fly ash.
Calcareous fly ash (W)
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Fly ash with high content of calcium compoundsPOZZOLAN-HYDRAULIC ACTIVITY OF CALCAREOUS FLY ASH
FROM CONVENTIONAL FURNACES
Temperature [°C]
Tim
e o
f h
yd
rati
on
[d
ay
s]
Specific surface of grund fly ash
[m2/kg]
Compressive strength [MPa] after:
3 days 7 days 28 days 90 days
559 3,4 2,4 5,2 5,2
744 9,3 9,9 11,5 13,8
A1 – unground ash
A2 – ground ash
Time [days]
Com
pres
sive
str
engt
h [M
Pa]
70 % of siliceous fly ash (specific surface 540[m2/kg]70 % of calcareous fly ash (specific surface 556[m2/kg]
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Characteristics of fly ash
Morphology of fly ash grains
calcareous siliceous
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Common cements contain fly ash as a main component
1) Most often this type of cement includes fly ash and blastfurnace slag, but also may include pozzolan, silica fume,burnt shale and ground limestone.2) The cement includes usually a mixture of pozzolans and fly ash or fly ash.3) The cement includes pozzolans, blastfurnace slag and siliceous fly ash.
Type of common cement The content of mineral constituent, % mass
Portland-fly ash cement
CEM II/A-VCEM II/B-V
6-2021-35
CEM II/A-WCEM II/B-W
6-2021-35
Portland-composite cement1) CEM II/A-MCEM II/B-M
6-2021-35
Pozzolanic cement2) CEM IV/ACEM IV/B
11-3536-55
Composite cement3) CEM V/ACEM V/B
18-3031-50
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Properties of cements containing fly ash
0
5
10
15
20
0:002:00
4:006:00
8:0010:00
12:0014:00
16:0018:00
20:0022:00
11:35
9:05
7:05
6:05
4:25
20:05
14:50
12:20
8:14
6:15 Final setting timeInitial setting time
Time, h : min
Tem
pera
ture
, C
Setting time of CEM II/B-V 32,5R depending on ambient temperature
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
2 dni 7 dni 28 dni 90 dni 180 dni0
10
20
30
40
50
60
70
23.9
37.4
46.7
52.455.5
14.1
25.8
42.3
57.461.3
CEM I 32,5RCEM II/B-V 32,5R
Com
pres
sive
str
engt
h [M
pa]
Increase of compressive strength
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Properties of cements containing fly ash
Compressive strength development of cements (standard mortars)
2 7 28 56 900
10
20
30
40
50
60
15.2
26.7
43.8 47
.9 50.1
10.4
25.1
47.5 51
.3
56.7
15.5
27.3
47.2 50
.9 54.9
CEM II/B-M(S-V) 32,5RCEM III/A 32,5N -LHCEM V/A(S-V) 32,5R - LH
Time [days]
Co
mp
res
siv
e s
tre
ng
th [
MP
a]
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Pozzolanic activity
Pozzolanic reaction rate depends on: • chemical and mineral composition of fly ash,• temperature and time of reaction,• pressure,• amount of water,• fly ash / Ca(OH)2 ratio,• fly ash specific surface,• presence of chemical admixtures
FLY ASH(reactive SiO2 and Al2O3)
Ca(OH)2
hydrated calcium silicates(C-S-H)
hydrated calcium aluminateshydrated calcium sulfo aluminate
H2O
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Amount of Ca(OH)2 in hardened cement paste
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
CEM I 32,5R CEM III/A 32,5NPermeability of concrete
CEM II/B-S 32,5R CEM II/B-V 32,5R
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Chemical composition of calcareous fly ash
Specimen No
Chemical composition [%]
loss on ignition SiO2 Al2O3 Fe2O3 CaO CaOw MgO SO3 K2O Na2O
PL W1-0’ 2,56 33,62 19,27 5,39 31,32 2,87 1,85 4,50 0,11 0,31
PL W4-0’ 2,67 45,17 20,79 4,58 20,60 1,18 1,49 2,96 0,19 0,23
PL W5-0’ 3,58 38,63 27,92 6,62 19,01 0,76 1,90 1,57 0,16 0,14
ST 2008 2,91 42,94 17,24 4,31 25,89 1,40 2,04 3,47 0,26 0,13
P 34 2,01 41,27 16,54 4,59 28,47 3,00 1,45 3,40 0,25 0,23
P 35 1,63 34,38 15,85 4,74 33,55 2,53 1,61 5,84 0,27 0,29
P 36 1,59 28,71 14,72 4,65 36,35 1,20 1,72 9,68 0,28 0,45
P 13 3,87 34,35 13,14 3,78 37,14 5,16 1,76 3,38 0,19 0,33
P 33 3,60 56,90 18,20 3,17 14,11 0,95 0,94 1,60 0,14 0,11
P 8 6,11 28,70 9,76 4,00 43,42 5,01 1,74 3,03 0,13 0,22
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Phase composition of calcareous fly ash
Mineral constituent Phase composition [%]
PL W1-0' PL W5-0' PL W4-0' ST 2008 P34 P35 P36 P13 P33 P8
Amorphous phase 30,6 64,4 48,6 58,7 20,0 26,5 52,4 3,1 42,0 39,1Quarz SiO2 11,6 6,3 16,8 10,3 24,3 11,3 4,2 11,1 31,9 5,0Mullite Al6Si2O13 2,3 5,6 4,4 2,4 3,8 2,2 1,4 2,3 6,5 2,2Free CaO 5,0 1,2 1,6 1,4 4,5 6,3 3,3 7,2 0,9 6,4Anhydrite CaSO4 5,5 1,8 3,9 4,5 5,0 8,9 10,4 4,0 1,4 3,1Larnite 2CaO · SiO2 12,8 1,9 4,0 4,2 14,4 16,4 11,6 17,8 4,2 21,2Gehlenit Ca2Al2SiO7 10,5 6,8 5,6 5,2 9,4 9,3 5,1 7,8 3,7 6,1Anorthite CaAl2Si2O8 8,9 5,9 11,1 8,4 8,0 6,1 2,0 6,0 6,4 3,4Ca3Al2O6 6,4 1,6 2,4 2,2 6,0 6,9 4,8 8,1 1,5 9,3Hematite α-Fe2O3 1,7 1,2 0,6 0,9 1,4 1,2 0,8 0,5 0,6Brownmillerite Ca2(Al,Fe)2O5
1,3 2,0 0,1 3,1 3,7 2,2 3,2 0,6 3,0
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Pozzolanic activity of mineral additives
2 7 28 90 180 3600
20
40
60
80
100
70% W
70% W+
70% V
70% S+
70% V+
Time [days]
Act
ivity
ind
ex
[%]
+ - ground components
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
2 7 28 90 180 3600
20
40
60
80
CEM II/B-W+
CEM II/B-M (V-W+)
CEM II/B-M (LL-W+)
CEM II/B-M (S-W+)
CEM II/B-S 32,5R*
CEM II/B-M (V-LL) 32,5R*
Time [days]
Co
mp
ress
ive
str
en
gth
[MP
a]
Compressive strength of Portland – composite cement
- cements industrially produced
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Production scheme of CEM II/B-M (V-W) 32,5R
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
2 7 28 90 1800
10
20
30
40
50
60
70
80
CEM II/B-M (V-W) 32,5R
CEM I 42,5R
CEM II/B-S 32,5R
Time [days]
Co
mp
ress
ive
str
en
gth
[MP
a]
Compressive strength of CEM II/B-M(V-W) 32,5R
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Results of conducted research
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
SILICEOUS FLY ASH AS A CONCRETE
COMPONENT
Chemical composition of fly ash according to EN 450-1
ComponentAllowed content
Fly ash received from coal combustion only
Fly ash received from co-combustion only
Loss on Ignition category A category B category C
5,0 %≤ 7,0 %≤ 9,0 %
Chlorides 0,10 %SO3 3,0 %
CaO free 1,5 %1)
CaO reactive 10,0 %SiO2 reactive
Determination ofthe content is not
necessary
It is assumed that the requirement has been met
≥ 25,0 %
Sum of oxides: SiO2, Al2O3, Fe2O3 70,0 %
Content of MgO 4,0 %Sum of alkalis expressed in Na2Oeq 5,0 %
Content of soluble phosphate compounds expressed in P2O5
100mg/kg
1) Fly ash, in which the free CaO content is higher than 1.5% by mass may be accepted provided the soundness - Le Chatelier's test at ≤ 10 mm
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Phisical properties of fly ash according to EN 450-1 Property Requirement
Fineness, sieve residue with 0,045 mm of mesh sieve acc.to PN-EN 451-2
category N category S
40 % 12 %
Pozzolanic activity index: after 28 daysafter 90 days
75 % 85 %
The soundness(test necessary when content of CaOfree
below 1,5 %
max. 10 mm
Consistent densityMaximum difference
200 kg/m3 compared to the one declared by the producer
Initial setting time of paste containing 25% of fly ash and 75% of Portland cement CEM I
Not longer that 120 minutes compared to the setting time of applied Portland
cement CEM I
Water demand (determined for fly ash of S category)
95% of water demand of Portland cement CEM I used in tests
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
PropertyASTM C618 CAN/CSA –A23.5-98
Class F Class C Class F Class CI Class CH
Total content of CaO ≤ 10% ≥ 10% ≤ 8% 8 – 20% ≥ 20%
Loss on ignition, maximum, % 6* 12 6
Fineness (sieve residue 45 μm), maximum, %
34
Water demand, maximum, % 105% –
SO3 content, maximum, % 5
Oxides sum content(SiO2, Al2O3, Fe2O3)
> 70% > 50% - - -
Activity index after 7 and 28 days 75%** 68%**
Autoclave soundness, % 0,8*- it is allowed till 12% under the condition of suitability verification** - can not be compared because of the different compositions of mortars fineness and density of fly ash can vary by up to 5% of the declared value
Requirements set against fly ash in the standards ASTM and CAN-CSA
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Fly ash Fly ash Loss on ignotion – 1,79 % - category A Loss on ignotion – 8,48 % - category C Fineness – 1,0 % - category S Fineness – 27,5 % - category N
Microscope image of fly ash
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
10.5 30.660
65
70
75
80
85
90
95
100
105
110
Fineness [%]
Wa
ter
de
ma
nd
[%
]
Correlation of water demand and fineness of fly ashwith similar loss on ignition (4,78% and 4,99%)
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
4.99 9.5660
70
80
90
100
110
120
Loss on ignition [%]
Wa
ter
de
ma
nd
[%
]
Correlation of water demand and loss on ignitionof fly ash with similar fineness (30,6% and 29,8%)
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Fly ash with different contents of loss on ignition (unburned carbon)
Type of fly ash Slump test [cm]Amount of
superplasticizer [% mass of cement]
Air content [%]
Fly ash I(2,2% loss on ignition)
18 cm 0,87 1,7
Fly ash II(17,9% loss on ignition)
18 cm 2,1 1,7
Fly ash – loss on ignition 2,2% Fly ash – loss on ignition 17,9%
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Effect of fly ash particle size on the amountin concrete mixing water at constant consistence [acc. Lindon K.A. Sear]
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Concrete with the addition of fly ash
Lower total porosity
Lower share of the capillary pores
Larger share of the gel pores
Microstructure
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
The diffusion coefficient of chloride ions in the concrete with fly ash and slag cements
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
relative to the witnesses relative to the strength af-ter 28 days
0
20
40
60
80
68.6
61.2
26.9
16.2
non-air-entrained concrete
air-entrained concrete
The
decr
ease
in s
tren
gth
[%]
20 % - limit strength loss rela-tive to witnesses
28 days
relative to the witnesses relative to the strength af-ter 28 days
0
20
40
60
80
49,0
43.6
17.8 5.1
Th
e d
ecr
ea
se in
str
en
gth
[%
]
56 days
Frost resistance of concrete (F150); start test after 28, 56 and 90 days Cement (30% of fly ash); 350 kg/m3; w/c = 0.5
relative to the witnesses relative to the strength af-ter 28 days
0
20
40
60
80
18.8
10.74.2 3,0
The
dec
reas
e in
str
engt
h [
%]
90 days
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
The change in temperature inside of the concrete block (volume 15 m3)
Z b i g n i e w G i e r g i c z n y. V I n t e r n a t i o n a l C o n f e r e n c e ASHES FROM TPPS
Conclusions
1. Fly ash, as a by-product of coal combustion, is an interesting mineral additive which should be widely applied in industrial practice, specially, in the production of cement and concrete
2. Used in the production of cement and concrete shall comply with the following standards:– PN-EN 197-1 „Cement — Part 1: Composition, specifications
and conformity criteria for common cements”
– PN-EN 450 „Fly ash for concrete — Part 1: Definition, specificationsand conformity criteria”
3. Fly ash applied in the above technologies should be characterized by: homogeneity, stability of physical characteristics, appropriate activity and spherical shape of the grains
Thank you for your attention