Fly ash in cement and concrete composition

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Fly ash in cement and concrete composition

• Zbigniew Giergiczny
• Silesian University of Technology, Gliwice,
  Poland
• Technological Center Betotech , Ltd.

April, 2425 2014, Moscow
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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

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• Fly ash

Fly 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.
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• 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).

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• Classification of fly ash

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Fly ash as a cement component
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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 .

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• 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

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Calcareous fly ash (W)

• 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.

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• Fly ash with high content of calcium compounds

POZZOLAN-HYDRAULIC ACTIVITY OF CALCAREOUS FLY
ASH FROM CONVENTIONAL FURNACES
Specific surface of grund fly ash m2/kg Compressive strength MPa after Compressive strength MPa after Compressive strength MPa after Compressive strength MPa after
Specific surface of grund fly ash m2/kg 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
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Characteristics of fly ash
Morphology of fly ash grains calcareous
siliceous
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Common cements contain fly ash as a main component
Type of common cement Type of common cement The content of mineral constituent, mass
Portland-fly ash cement CEM II/A-V CEM II/B-V 6-20 21-35
Portland-fly ash cement CEM II/A-W CEM II/B-W 6-20 21-35
Portland-composite cement1) CEM II/A-M CEM II/B-M 6-20 21-35
Pozzolanic cement2) CEM IV/A CEM IV/B 11-35 36-55
Composite cement3) CEM V/A CEM V/B 18-30 31-50
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.
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Properties of cements containing fly ash
Setting time of CEM II/B-V 32,5R depending on
ambient temperature
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Properties of cements containing fly ash
Increase of compressive strength
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Compressive strength development of cements
(standard mortars)
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• Pozzolanic activity

hydrated calcium silicates(C-S-H) hydrated
calcium aluminates hydrated calcium sulfo
aluminate
FLY ASH(reactive SiO2 and Al2O3)
Ca(OH)2
H2O

• 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

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Amount of Ca(OH)2 in hardened cement paste
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Permeability of concrete
CEM III/A 32,5N
CEM I 32,5R
CEM II/B-S 32,5R
CEM II/B-V 32,5R
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Chemical composition of calcareous fly ash
Specimen No Chemical composition Chemical composition Chemical composition Chemical composition Chemical composition Chemical composition Chemical composition Chemical composition Chemical composition Chemical composition
Specimen No 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
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Phase composition of calcareous fly ash
Mineral constituent  Phase composition Phase composition Phase composition Phase composition Phase composition Phase composition Phase composition Phase composition Phase composition Phase composition
Mineral constituent  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 39,1
Quarz SiO2 11,6 6,3 16,8 10,3 24,3 11,3 4,2 11,1 31,9 5,0
Mullite Al6Si2O13 2,3 5,6 4,4 2,4 3,8 2,2 1,4 2,3 6,5 2,2
Free CaO 5,0 1,2 1,6 1,4 4,5 6,3 3,3 7,2 0,9 6,4
Anhydrite CaSO4 5,5 1,8 3,9 4,5 5,0 8,9 10,4 4,0 1,4 3,1
Larnite 2CaO SiO2 12,8 1,9 4,0 4,2 14,4 16,4 11,6 17,8 4,2 21,2
Gehlenit Ca2Al2SiO7 10,5 6,8 5,6 5,2 9,4 9,3 5,1 7,8 3,7 6,1
Anorthite CaAl2Si2O8 8,9 5,9 11,1 8,4 8,0 6,1 2,0 6,0 6,4 3,4
Ca3Al2O6 6,4 1,6 2,4 2,2 6,0 6,9 4,8 8,1 1,5 9,3
Hematite a-Fe2O3 1,7 1,2   0,6 0,9 1,4 1,2 0,8 0,5 0,6
Brownmillerite Ca2(Al,Fe)2O5 1,3 2,0   0,1 3,1 3,7 2,2 3,2 0,6 3,0
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Pozzolanic activity of mineral additives
- ground components
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Compressive strength of Portland composite
cement
- cements industrially produced
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Production scheme of CEM II/B-M (V-W) 32,5R
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Compressive strength of CEM II/B-M(V-W) 32,5R
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Results of conducted research
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SILICEOUS FLY ASH AS A CONCRETE COMPONENT
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Chemical composition of fly ash according to EN
450-1
Component Allowed content Allowed content
Component 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   ? 5,0 7,0 9,0
Chlorides ? 0,10 ? 0,10
SO3 ? 3,0 ? 3,0
CaO free ? 1,5 1) ? 1,5 1)
CaO reactive ? 10,0 ? 10,0
SiO2 reactive Determination of the content is not necessary   It is assumed that the requirement has been met 25,0
Sum of oxides SiO2, Al2O3, Fe2O3 Determination of the content is not necessary   It is assumed that the requirement has been met ? 70,0
Content of MgO Determination of the content is not necessary   It is assumed that the requirement has been met ? 4,0
Sum of alkalis expressed in Na2Oeq Determination of the content is not necessary   It is assumed that the requirement has been met ? 5,0
Content of soluble phosphate compounds expressed in P2O5 Determination of the content is not necessary   It is assumed that the requirement has been met ? 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 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 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
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Phisical properties of fly ash according to EN
450-1
Property Property Requirement
Fineness, sieve residue with 0,045 mm of mesh sieve acc.to PN-EN 451-2 category N category S 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 days after 90 days ? 75 ? 85
The soundness (test necessary when content of CaOfree below 1,5 The soundness (test necessary when content of CaOfree below 1,5   max. 10 mm
Consistent density Consistent density Maximum 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 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) Water demand (determined for fly ash of S category) ? 95 of water demand of Portland cement CEM I used in tests
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Requirements set against fly ash in the standards
ASTM and CAN-CSA
Property ASTM C618 ASTM C618 CAN/CSA A23.5-98 CAN/CSA A23.5-98 CAN/CSA A23.5-98
Property 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 6 12 6 6
Fineness (sieve residue 45 µm), maximum, 34 34 34 34 34
Water demand, maximum, 105 105
SO3 content, maximum, 5 5 5 5 5
Oxides sum content (SiO2, Al2O3, Fe2O3) gt 70 gt 50 - - -
Activity index after 7 and 28 days 75 75 68 68 68
Autoclave soundness, 0,8 0,8 0,8 0,8 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 - 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 - 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 - 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 - 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 - 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
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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
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Correlation of water demand and fineness of fly
ashwith similar loss on ignition (4,78 and
4,99)
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Correlation of water demand and loss on
ignitionof fly ash with similar fineness (30,6
and 29,8)
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Fly ash with different contents of loss on
ignition (unburned carbon)
Fly ash loss on ignition 17,9
Fly ash loss on ignition 2,2
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
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Effect of fly ash particle size on the amountin
concrete mixing water at constant consistence
acc. Lindon K.A. Sear
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Microstructure
Concrete with the addition of fly ash
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The diffusion coefficient of chloride ions in the
concrete with fly ash and slag cements
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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
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The change in temperature inside of the concrete
block (volume 15 m3)
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Conclusions

• 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
• Used in the production of cement and concrete
  shall comply with the following standards
• PN-EN 197-1 Cement Part 1 Composition,
  specificationsand conformity criteria for common
  cements
• PN-EN 450 Fly ash for concrete Part 1
  Definition, specificationsand conformity
  criteria
• Fly ash applied in the above technologies should
  be characterized by homogeneity, stability of
  physical characteristics, appropriate activity
  and spherical shape of the grains

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Thank you for your attention