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World of Processsed Fly ash and its Importance in Concrete
By Mayur PathakG.M. - Product Technology
An AMBUJA Cements Ltd company.
An AMBUJA Cements Ltd company
What is fly ash?
typically spherical, diameter ranging from less than 1µm up to 150 µm.Fly ash is a by-product of the combustion of pulverized coal
in thermal power plants.
The dust collection system (electro static precipitators) removes the fly ash as a fine particulate residue, from the combustion gases.
Fly ash particles are typically spherical, diameter ranging from less than 1µm up to 150 µm.
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The Pozzolana Fly ash exhibits pozzolanic activities. A
pozzolana is defined as “a silicious or aluminous material which itself possesses little or no cementitious value but which will, in a finely divided form and in the presence of moisture, chemically react with Calcium hydroxide, at ordinary temperature to form compounds possessing cementitious properties.
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Chemical Benefits 1. It contains reactive silica. 2. It reduces heat of hydration. 3. It forms secondary CSH Gel. 4. It improves delayed strength. 5. It protects concrete from salt and
sulphate attacks. 6. It makes concrete impermeable.
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Fineness : Scanning electron microscope (SEM) and particle size analysis have shown that particles are spherical and rounded.The size of particles varied from 1 µm to 150 µm. Typically, the size less than 10 µm contributes to the pozzolanic activities. The size above 45 µm hardly contributes to pozzolanic activities. In the power station the raw fly ash is found which varies drastically from 1% retention on 45 micron sieve in the last row to 92% retention on the same sieve.Specific gravity of fly ash varies widely but it is taken as 2.15-2.35.
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• Bogues Compounds
C3S = Tricalcium Silicate• C2S = Dicalcium Silicate
C3A = Tricalcium Aluminate C4AF = Tetracalcium Alumino Ferrite
Boring Concrete Chemistry
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Ca(OH)2 + SiO2(fly ash) + H --->C3S2H3 C-S-H gel
Tri-calcium silicate 2(3CaO.SiO2)+6H2O- 3CaO.2SiO2.SiO2.3H2O+3Ca(OH)2
In short 2C3S+6H - C3S2H3 + 3Ca(OH)2Corresponding molecular weights involved are 100 + 24 -- 75 + 49
Di-calcium silicate2(2CaO.SiO2) +4H20- 3CaO.2SiO2.3H2O + Ca(OH)2In short 2C2S + 4H -- C3S2H3 + Ca(OH)2
Corresponding molecular weights involved are 100 + 21 -- 99 + 22
1 . Fly ash particles are perfectly spherical in shape.
2 . Particles size smaller than cement.3. Fly ash reduces water demand due to
ball bearing effect.4. Fly ash makes mix cohesive and
facilitates pumping.5. Fly ash helps in slump retention.
Physical BenefitsPhysical Benefits
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SEM Pictures
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Necessity of processed fly ash
1 2 3 4 5 6 7 8 9 100
10
20
30
40
50
60
2022
34
55
38
20
28
45
2219
Run Off Station Ash Quality
ROS 45
Week No
ROS% 45
MICRON
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Standard Pozzocrete Comparision
Test
Min/Max ASTM C-618 EN-450 BS-3892 IS-3812 P30 P40 P60 P63 P100 Category Sr No Unit Max S N
1 Fineness-Specific surface by m2/kg MinNot specified
320 Not 280 320 400 600 Blaines Air- Permeability specified
2 ROS 45 Micron % Max 34.0 12.0 40.0 12.0 34.0 34.0 25.0 18.0 10.0 0
3 Loss On Ignition % Max 6.0 7.0 7.0 5.0 3.0 2.5 2.5 2.5 2.5
5Water Requirement(Max of control) % Max 105.0 95.0 not specified 95.0 not speci 105.0 100.0 96.0 95.0 95.0
6 Moisture Content % Max 3.0 Not Specified 0.5 2.0 0.5 0.5 0.5 0.5 0.57 Soundness By Autoclave Max 0.8% 10mm 0.8% 0.2% 0.2% 0.1% 0.1% 0.1%
8Compressive strength at 28 Days % % Min 75.0 75.0 80.0 80.0 75.0 80.0 85.0 90.0 95.0
of plain cement mortar, 9 Lime Reactivity N/mm2 Min Not specified 4.5 Not Speci 4.5 5.0 5.5 7.0
Chemical analysis 1 Sio2+Al2O3+Fe2O3 % Min 70.0 70.0 Not 70.0 90.0 90.0 90.0 90.0 90.02 SiO2 % Min Not specified Not Specified Specified 35.0 50.0 50.0 50.0 50.0 50.03 Reactive Silica % Min 25.0 20.0 20.0 20.0 20.0 20.0 20.04 Cao % Max 10.0 10.0 not speci 5.0 5.0 5.0 5.0 5.05 Mgo % Max Not specified 4.0 4.0 4.0 4.0 4.0 4.0 4.06 SO3 % Max 4.0 3.0 2.0 3.0 2.0 2.0 2.0 2.0 2.07 Na2O % Max Not specified 5.0 Not speci 1.5 1.5 1.5 1.5 1.5 1.58 Total Chlorides % Max Not specified 0.1 0.1 0.05 0.05 0.05 0.05 0.05 0.05
Product Confirming to Standards ASTM-C618 ASTM-C618 ASTM-C618 ASTM-C618 ASTM-C-618
EN450-Ncat EN450-Ncat EN450-N cat EN450-N cat EN450-N cat
IS-3812 Part-
1IS-3812 Part-
1IS-3812 Part-
1
EN450-S cat EN450-S cat
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Water Requirement of Various Grades of Pozzocrete
P10 P20 P30 OPC P40 P60 P63 P83 P1000
20
40
60
80
100
120 108 104.8 102 100 99.2 96 94 91.2 88
%compared with OPC Linear (%compared with OPC)Various Grades of Pozzocrete
Wat
er r
equi
rem
ent %
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Strength factors of Various Grades of Pozzocrete %
0
20
40
60
80
100
120
6472 78
90 94 99 100 105 108
P10P20P30P40P60P63OPCP83P100Linear (P100)
Product Series
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Pozzocrete for ConcreteI. Pozzocrete 10- As a filler material and partial
sand replacement.II. Pozzocrete 30 and 40 – widely used for mass
concrete for partial cement replacement up to 70%.
III. Pozzocrete 60 and 63- concrete Ranging from M15 to M45.Partial cement replacement.(fineness 320 m2/kg to400 m2/kg).
IV. Pozzocrete 100- For High performance concrete M50 and above up to M100.(Replacement of Micro silica)
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Regular Cement Replacement Application
I. 1.For R.C.C. structures 15% to 35% IS 1489 & IS 456.
II. For Mass concrete structures ,cement replacement can be up to 70-75%.
III. For brick work and plaster.30-40%.IV. For flooring and dado.30-40%.
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Particulars Control mix Pozzocrete 60 mix
OPC 400 300
Pozzocrete 60 0 140
Water 160 158
Admixture dosage 1.2% 1.2%
w/c 0.4 0.36
Slump
Initial 150 180
30 min 120 140
60 min 80 120
90 min 100
3 days in Mpa 28 26
7 days in Mpa 35 34
28days in Mpa 44 46
Comparative Trials with Pozzocrete 60 as 32% cement replacement
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Fly ash as a Substitute for Microsilica
Superfine fly ash – Pozzocrete 100
ROS on 45 microns – zeroROS on 25 microns – 0.25, maxSSA by Blaine – 625 m2/kg, min
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Pozzocrete 100 – Particle Size Distribution
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Particulars Control mix Pozzocrete 100 mix
OPC 440 kg 445 kgMicrosilica 45 kg 0Pozzocrete 100 0 50Pozzocrete 60 120 kg 110Water 169 lit 136 litAdmixture dosage 1% 1%w/c 0.28 0.24Initial Slump collapse collapse180 min 200 mm 200 mm1 day in Mpa 25.23 24.443 days in Mpa 55.25 64.77 days in Mpa 65.55 71.1928days in Mpa 96.44 94.89RCPT (28d) in
coloumbs950 1000
Comparative Trials with P100
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Material Quantity Rate Amount
OPC 440 6 2640
Micro silica 45 26 1170
P100 0 0 0
P60 120 3.0 360
Total 4170
Quantity P100 Rate P100
OPC 445 6.0 2670
Micro silica 0 26 0
P100 50 10 500
P60 110 3.0 330
Total 3500
P100 Mix Cost Comparison of Binder
• Approximate Cost Saving – 16%
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Fly ash as Sand Replacement
Different type of fly ash – coarse Fly Ash (P10) .
P10 specificationsIn the range of 65% to 90% ROS on 45
micronsLOI – Maximum 2.5%
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Modifications in Mix Design Using P10• P10 is 100% passing through 600 micron sieve.• Reduction of total fines in a mix from 5 to 15% .• Replace 10 to 20% sand by P10• Total binder content may be reduced around 5% to
10%.• OPC Fly ash proportion should be kept same.• The water demand is reduced by 3 to 5%.
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Parallel Trials Conducted for M25
Material (M3)Control mix Sand replacement mixQuantity (kg) Quantity (kg)
OPC 53 UT 263 263
Fly ash 87 87
Water 165 165
20mm 697 818
10mm 231 273
N.S 741 786
C.S 231 0
P10 0 139
Admixture 3.5 3.5
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Workability Comparison Control mix P10 mix
Slump readings mm mm
Initial 120 180
30min 100 150
60min 130
90min 120
120min 100
150min
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Compressive Strength
Designation 7 Days Mpa 28 Days w/c Sand
replacement by P10 33.5 48.5 0.47
Control mix 28.09 40.27 0.47
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Conclusions• Use of P10 as a partial sand replacement gives flexibility to use coarse
sand in mix of any grade.• It reduces segregation problems and makes mix cohesive and hence
pumpable mix for even lower grades of concrete.• It reduces water cement ratio and increases retention time, acts as
mineral admixture.• It reduces fine aggregate content and increases coarse aggregate
content.• The reduction of water cement ratio and increase of CA content results
in increased strength and hence reduced cement content. • Due to reduced water cement ratio and increase CA content we get
increased strength and hence reduced cement content.
.
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Some Prestigious Projects with PozzocreteAn AMBUJA Cements Ltd company
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Dijibouiti Kempinski hotel
Kuwait Boubyan Sea Port Project
Burj Khalifa Kuwait Al-Hamara Tower
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Dij
Ghatghar Dam
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DIRK India produces a range of POZZOCRETE grades by mechanical air classification of raw Pulverized Fuel Ash
DIRK India Nashik facility
Product range:POZZOCRETE 40POZZOCRETE 60POZZOCRETE 63POZZOCRETE 10
POZZOCRETE 100
Pozzocrete - A Boon To Construction Industry
•Client•Consultant•Contractor•& Most Importantly ……….
It offers innumerable benefits to various
parties like:-
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The Mother EarthEvery ton of cement produced has CO2
Emissions of 0.8to 1 Tons so every Ton of
Pozzocrete replacing cement prevents equal
amount of CO2 emissions in atmosphere.
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To summarize: Mr.Adam Neville says that “ importance of fly ash cannot be exaggerated : It is no longer a cheap substitute for cement, nor an “extender” or an addition to the mix. Fly ash bestows important advantages upon Concrete, and it is, therefore, essential to understand the role and influence of fly ash”.
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No Fly ash no ConcreteTo end up, let us repeat what E.A.Abdun-
Nur said about the fly ash“In the real world of modern
concrete, fly ash is as essential an ingredient of the mixture as are Portland Cement, aggregate , water and chemical admixtures. In most concretes, I use it in larger amounts (by volume) than Portland Cement , and therefore it is not an admixture. Concrete without fly ash and chemical admixtures should only be found in museum showcases.
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