High volume fly ash concrete is a concrete where a replacement of about 35% or more of cement is made with the usage of fly ash. Fly ash concrete is an eco-friendly construction material in which fly ash replaces a part of Portland cement.

1. PROPERTIES OF
HIGH VOLUME
FLY ASH CONCRETE
- VIBHANSHU SINGH
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2. OVERVIEW
INTRODUCTION
PROPERTIES OF FRESH HVFA CONCRETE
PROPERTIES OF HARDENED HVFA CONCRETE
CONCLUSION
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3. INTRODUCTION
Fly ash concrete is an eco-friendly construction material
in which fly ash replaces a part of Portland cement.
But IS:456 – 2000 and ACI:318 allows replacement of
OPC by Fly ash up to 35% only as binding material.
High volume fly ash concrete is a concrete where
a replacement of about 35% or more of cement is
made with the usage of fly ash.
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4. WHAT IS FLY ASH?
Fly ash is a finely divided byproduct resulting from the
combustion of coal in power plants.
It contains large amounts of silica, alumina and small
amount of unburned carbon, which pollutes
environment.
It is grey in colour and alkaline in nature.
The particle size ranges between 1-100 microns.
The specific gravity of FA lies between 1.9 and 2.8
(generally 3.15 for Cement)
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5. The surface area is typically 300–500 m2/kg, although
some FA can have a surface area as high as 700
m2/kg ( around 330 m2/kg for Cement )
The mass per unit volume including air between
particles ( density ) can vary from 540 to 860 kg/m3.
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6. Classification of Fly Ash
Two classes of fly ash are defined by ASTM C618:
Class F fly ash
Class C fly ash
This classification is based on the chemical
composition of FA i.e. the sum of silica, alumina and
iron oxide percentages in the FA, being :
 minimum of 70% for a Class F
 minimum 50% for a Class C
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7. 7
SOURCE:
www.caer.uky.edu/kyasheducation/flyash.sht
ml
SOURCE: www.gradjevinarstvo.rs

8. ISSUES WITH OPC
 Conventional Portland Cement is the most consumed
commodity in the world after water.
 It is also the most energy intensive material
 Cement production leads to high carbon-dioxide emission.
CO2 is the primary green house gas that causes global warming
manufacturing of cement accounts for 6 to 7% of the CO2 that
humans produce.
It is produced by calcination of limestone and burning of fossil
fuels
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9. WHY TO USE FLY ASH?
being a pozzolanic, it can actually replace a part of
Portland cement
results in more durable concrete
high ultimate strength
improves workability
improves cost economy of concrete
reduction in heat of hydration
decreases density of concrete
 more environment friendly concrete.
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10. EFFECT OF HIGH VOLUME OF FLY ASH
ON PROPERTIES OF FRESH CONCRETE
1. WORKABILITY
2. SETTING TIME, BLEEDING AND SEGREGATION
3. HEAT OF HYDRATION
4. DENSITY
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11. WORKABILITY
The inclusion of high volume of fly ash increases the
workability as the content of FA is increased.
The increment in the slump height is about 40%
and 54% with the inclusion of 45% and 50% FA,
respectively.
generally higher substitution of Portland cement by
fly ash reduces the water requirement for
obtaining a given workability
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12. . Effect of fly ash fineness & % on
water demand of concrete
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13. WORKABILITY
 reduction in water requirement is mainly due to three mechanisms:
 Fly ash gets absorbed on the surface of oppositely charged
cement particles and prevent them from flocculation, releasing
large amounts of water, thereby reducing the water-demand for a
given workability.
 The spherical shape and the smooth surface of fly ash particles
help to reduce the interparticle friction and thus facilitate mobility
 Due to its lower density and higher volume per unit mass, fly ash is a
more efficient void-filler than Portland cement.
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14. Contributions of enhanced workability:
Light weight concrete is easier to pump as pumping
requires less energy.
Improved finishing
Reduced segregation and bug holes
Reduced Bleeding
Less sand is needed in the mix to produce required
workability.
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15. SETTING TIME
High volume of fly ash extends both the initial and
final setting time of concrete
The impact of fly ash on the setting behavior of
concrete is dependent on:
composition and quantity of fly ash used
amount of cement
water - to – cementitious material ratio
concrete temperature
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16. Effect of FA content on penetration resistance of
setting concrete mixture
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17. Bleeding and Segregation
The inclusion of high volume of fly ash in the
mixture reduces the bleeding and segregation.
Reason:
the rate and amount of bleeding decreases due to
the reduced water demand.
The reduction of bleeding and segregation may be
related to the lubricating effect of the glassy spherical
FA particles.
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18. HEAT OF HYDRATION
Both the maximum rate of heat evolution and the
cumulative heat evolution decrease with the
inclusion of 45% FA during the first 72 hours.
The inclusion of 45% FA results in 36% reduction in
the cumulative heat evolution.
In addition, the time of reaching the maximum rate
of heat evolution delays.
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19. Effect of fly ash on heat of hydration19
Source: optimizing-the-use-of-fly-ash-in-concrete – by
Michael Thomas (www.cement.org)

20. Effect of fly ash on temperature rise20
Source: optimizing-the-use-of-fly-ash-in-concrete – by Michael
Thomas (www.cement.org) Back…

21. DENSITY
Inclusion of high volume of fly ash in the mixture
decreases its density which leads to a reduction in
the dead weight of the constructed element.
Reason:
This reduction in the density could be attributed to the
lower specific gravity of FA (1.9 to 2.8) as compared to
cement (3.15)
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22. EFFECT OF HIGH VOLUME OF FLY ASH ON
PROPERTIES OF HARDENED CONCRETE
1. COMPRESSIVE STRENGH
2. DURABILITY
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23. COMPRESSIVE STRENGH
TEST
5 mixtures were considered , 3 of them with OPC
and varying FA content, and 2 control pastes using
100% OPC or 100% BC.
conducted using 40%, 60% and 80% FA
replacement by volume of cement
 maintaining the w/b by mass constant at 0.42
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24. MIXTURE PROPORTIONS OF THE PASTES
Mixture ID
Cement
(kg/m3)
Fly ash
(%)
Fly ash
(kg/m3)
Water
(kg/m3)
OPC 1359.7 0 0.0 571.1
BC 1307.5 0 0.0 549.1
40-F 864.4 40 434.5 545.5
60-F 594.0 60 671.7 531.6
80-F 306.4 80 924.0 516.7
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SOURCE: Felipe Rivera, Patricia Martínez, Javier Castro, Mauricio López “Massive volume fly ash
concrete”, Cement and Concrete Composites, Volume 63, October 2015

25. The cement pastes were prepared in a mechanical mixer
50-mm cube specimens were cast (3 specimens per age)
At the age of 24 h, the specimens were demolded and
placed in vacuum sealed plastic bags in a moist room,
(95 ± 3)% RH and (23 ± 2)˚C, until the age of testing.
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26. 26
SOURCE: Felipe Rivera, Patricia Martínez, Javier Castro, Mauricio López “Massive volume fly ash
concrete”, Cement and Concrete Composites, Volume 63, October 2015
The compressive strength gain after 3 d, 7 d, 28 d and 90 d for each mixture

27. The compressive strength of the 40-F paste is similar
to that of the OPC paste at any age
while that of the 60-F paste is very similar to the BC
paste at early ages (3 d and 7 d) and higher at 28 d
and 90 d.
The compressive strength of the 80-F paste is lower
than that of the BC paste at any age; its strength can
reach up to 22 MPa at 28 d and 35 MPa at 90 d.
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28. 28
Source: optimizing-the-use-of-fly-ash-in-concrete – by Michael Thomas
(www.cement.org)

29. Rate of strength gain
The rate of strength gain in the FA-F pastes
increases with the replacement level.
Between 28 d and 90 d, the strength gain of OPC
paste is similar to that of the BC paste but lower
than that of the 80-F paste (≈0.21 MPa/d).
For the 40-F and 60-F pastes, the strength gains are
the lowest (≈0.07 MPa/d and 0.08 MPa/d,
respectively), between 28 d and 90 d.
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30. DURABILITY
Abrasion Resistance
The mix containing 70% FA exhibits a slightly lower abrasion
value than the concrete containing 50% FA and OPC
concrete
although 70% FA exhibits a higher abrasion value below a
certain compressive strength.
The abrasion resistance is mainly dependent on the
compressive strength of concrete.
It is assumed that C-S-H of 50% FA or OPC provide better
cohesion to the aggregate-sand-paste and therefore better
resist the action of surface shear forces.
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31. Permeability and Resistance to Penetration of Chlorides
Fly ash reduces permeability of concrete to water and
gas provided the concrete is adequately cured, due to a
refinement in the pore structure.
Through pozzolanic activity, fly ash chemically combines
with water and CaOH2 – forming additional cementitious
compounds, therefore :
it is not subject to leaching
it decreases bleed channels, capillary channels and void
spaces and thereby reduces permeability.
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32. With the use of fly ash, concrete becomes nearly impermeable to
chlorides and the rate of chloride penetration decreases
significantly.
32
Source: optimizing-the-use-of-fly-ash-in-concrete – by Michael Thomas (www.cement.org)

33. Alkali- Silica Reaction
 Class F fly ash is capable of controlling alkali – silica reaction
in concrete even at moderate levels of replacement (20% to
30%)
 Reason : concentration of alkali hydroxides is reduced in the
pore solution when fly ash is present
 The level of fly ash required to suppress expansion of
concrete increases with:
Increased calcium and alkali content of fly ash;
Decreased silica content of fly ash;
Increased aggregate reactivity;
Increased alkali availability from Portland cement and
environment
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34.  There is low risk of concrete expansion occurring in the field
when very high volume fly ash concrete with 50% or more fly
ash is used.
34
Source: optimizing-the-use-of-fly-ash-in-concrete – by Michael Thomas
(www.cement.org)

35. Sulfate Resistance
HVFA concrete specimens exhibit higher sulfate
resistance. The specimens containing 60% FA as
cement replacement exhibited better performance
in lactic/acetic and sulfuric acid
FA induces three phenomena which improves
sulfate resistance:
consumes the free lime resulting it unavailable to react
with sulfate,
reduces permeability which prevents sulfate penetration,
and
by replacing cement, the reactive aluminates are reduced.
reduced.
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36. Carbonation and Corrosion Resistance
When concrete specimens are exposed to different
methods of carbonation, the results show a reduction in
the carbonation resistance of concrete specimens with
the inclusion of 50% FA as cement replacement.
Therefore there is increase in the carbonation depth of
concrete specimens
in areas prone to carbonation, particular attention must
be paid to ensure suitable:
concrete mix proportions,
period of moist curing, and
depth of cover
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37. 37
Source: optimizing-the-use-of-fly-ash-in-concrete – by Michael Thomas
(www.cement.org)

38.  Resistance to Cyclic Freezing and Thawing, and Deicer Salt Scaling
 Concrete can be resistant to cyclic freezing and thawing provided:
 it has sufficient strength
 an adequate air void system
 the aggregates are frost resistant.
This holds true for fly ash concrete
 concrete containing fly ash is less resistant to scaling when
subjected to freezing and thawing in presence of deicer salts.
 For fly ash concrete structures exposed to de-icing salts the
following observations have been made:
 scaling increases as the w/cm increases
 scaling mass loss increases with fly ash content
 the use of curing compounds reduces scaling
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39. CONCLUSION
 Use of high volume fly ash concrete in construction is one big step
in natural resource conservation and it needs to be promoted all
over the world.
 In fact, we can call high volume fly ash concrete as a green
concrete, since it can protect the environment from global warming
and at the same time from pollution.
 There may be some negativity attached to it like slower
construction rates as it gains strength slowly and gives lower early
strengths.
 But, the same can be ignored as the later strengths (90 days or
more) and durability of high volume fly ash concrete is much better
than plain concrete.
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40. Clearly there is no one replacement level best suited for
all applications.
The inclusion of high volume fly ash in the mixture
causes :
Reduced the heat of hydration, bleeding, segregation,
density, but increased workability and setting time.
Decreased the mechanical strength especially at early
ages with increasing FA content.
Increased durability of concrete
reduced resistance against Deicer Salt Scaling.
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41. Product Comparisons
 High Volume Fly Ash
Concrete
 Less energy intensive
manufacture
 Higher ultimate strength
 More durable
 Uses a waste by-product
 Less global warming gases
created
Conventional Concrete
Energy intensive
manufacturing
Weaker ultimate strength
Less durable
Uses virgin material
More global warming
gases created

42. REFERENCES
 (i) Alaa M. Rashad, A brief on high-volume Class F fly ash as cement
replacement – A guide for Civil Engineer, International Journal of Sustainable Built
Environment, Volume 4, Issue 2, December 2015, Pages 278-306, ISSN 2212-6090
 (ii) Felipe Rivera, Patricia Martínez, Javier Castro, Mauricio López, “Massive
volume fly ash concrete: A more sustainable material with fly ash replacing
cement and aggregates”, Cement and Concrete Composites, Volume 63,
October 2015, Pages 104- 112, ISSN 0958-9465
 (iii) Vanita Aggarwal, S. M. Gupta and S.N. Sachdeva, “HIGH VOLUME FLY ASH
CONCRETE: A GREEN CONCRETE”, Journal of Environmental Research And
Development Vol. 6 No. 3A, Jan-March 2012,Pages 884-887
 (iv) http://www.cement.org/docs/default-source/fc_concrete_technology/is548-
optimizing-the-use-of-fly-ash-concrete.pdf
 (v) http://flyash.com/data/upfiles/resource/
TB%206%20Fly%20Ash%20Decreases%20the%20Permeability%20of%20Concrete
%202015.pdf
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