-
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i>l
TechnicalReportSL-95-9
April1995
US
Army
Corps
of
Engineers
WaterwaysExperiment
Station
Use
ofLarge
Quantities
ofFly
Ash
n
Concrete
by ToyS .Poole
Approved
ForPublicRelease;Distribution
sUnlimited
9 9 5 6 5
2 6
DTXG
QULETrcr Gx**
Prepared
fo r
Headquarters,
U.S.
Army
Corps
of
Engineers
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Thecontentsof
this
eport
are
not
tobeusedoradvertising,
publication,
or
promotionalpurposes.Citation
oftrade
names
doesnot
constituteanofficial
endorsement
or
approval
of
the
use
ofsuchcommercialproducts.
juew- ---
fl
PRINTED
ON RECYCLEDPAPER
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Technical
Report
SL-95-9
April
1995
Use
of
Large
Quantities
ofFlyAsh
n
Concrete
by
T oy
S.Poole
U.S.
ArmyCorps
of
Engineers
Waterways
ExperimentStation
3909
Halls
FerryRoad
Vicksburg,M S
39180-6199
inal
report
for
public
release;
distributionis
unlimited
for
U.S.
ArmyCorpsofEngineers
Washington,
DC
20314-1000
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USrmyCorps
of
Engineers
Waterways
Experiment
Station
HEAD0UAH1EP.S
BULONG
FO R
INFORUMION
C ONT AC T
PUBLICAFFAIRSOFFICE
U.S.
ARMYENGINEER
WATERWAYSEXPERIMENTSTATION
3909
HAUS
FERRYROAD
V1CKSBURG,ISSISSIPPI9180-S1BS
PHONE:
601)634-2502
A HA
OF
RESERVA TION. Z.7 sqkj
Waterways
Experiment
StationCataloging-in-PublicationData
Poole,T oy
S.
(Toy
Spotswood),
1946-
Useof
argequantitiesofflyashinconcrete
/
by
T oyS.Poole
prepared
fo r
U.S.Army
Corps
of
Engineers.
42p. ll. 28cm .--(Technicalreport;SL-95-9)
Includes
bibliographicreferences.
1 .Flyash.2.Concrete-Additives.
.
UnitedStates.Army.
Corps
of
Engineers.I.
U.S.
Army
Engineer
Waterways
Experiment
Station.
II.
StructuresLaboratory(U.S.
Army
Engineer
WaterwaysExperimentSta-
tion)
V.
Title.
.Series:
Technical
report
(U.S.
ArmyEngineerWater-
waysExperiment
Station);SL-95-9.
T A7W34no.SL-95-9
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Contents
Preface
v
Conversion
Factors,
Non-SI
toSIUnits
ofMeasurement
1Introduction
2Effects
of
LargeQuantities
of
Fly
Ashon
Properties
of
Fresh
Concrete
Time
of
Setting
Workability,WaterRequirement,nd
Bleeding
Air
Entrainment
3Effects
ofLarge
Quantities
ofFly
Ash
onProperties
ofHardened
Concrete 1
Strength
1
Heat
of
Hydration
8
Creep
3
Drying
Shrinkage 3
Curing 5
4Effects
ofLarge
Quantities
of
Fl y
Ashon
Durability
of
Concrete...
6
Resistance
to
Freezing
and
Thawing
6
Sulfate
Resistance 7
Alkali-SilicaReaction
7
Resistanceto
Chloride-Ion
Penetration
8
5ResearchNeeded
9
6Conclusions
1
References 2
in
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Preface
This
reportreviewssomeof
theliterature
pertaining
to
th e
use
of
large
amounts
offlyashnconcrete.
Th e
report
waspreparedby
th e
Structures
Laboratory
SL),U.S .
Army
Engineer
Waterways
Experiment
Station
(WES),
forHeadquarters,
U.S.
Army
Corps
of
Engineers
HQUSACE),
under
Civil
WorksInvestigationalStudy
WorkUnit
32423,Optimizing
Cementand
Pozzolan
Quantities
n
Concrete.
Dr.
TonyLiu
wasthe
HQUSACE
Technical
Monitor.
The
report
was
writtenby
Dr.
To y
S.
Poole,
Concrete
Technology
Division
CTD),SL.
Th e
work
was
onducted
under
the
supervision
of
Dr.
Lillian
D.
Wakeley,
ActingChief,Materials
Engineering
Branch,
M r.
WilliamF.
McCleese,
ActingChief,
CTD,ndM r.
Bryant
Mather,
Director,SL.
At
th e
time
ofpublicationofthisreport,Director
ofWESwas
Dr.Robert
W.
Whalin.
Commander
was
COL
Bruce.
Howard,EN .
Th e
contents
ofthisreportare
not
to
be
used
foradvertising,
publication,
or
promotional
purposes.itationoftradenames
does
not
constitute
an
official
endorsement
or
approval for
the
use
ofsuch
commercialproducts
IV
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Conversion
Factors,
Non-SI
toS I
Unitsof
Measurement
Non-SI
units
ofmeasurement
used
in
this
report
can
be
converted
to
SIunits
as
follows:
Multiply By
To
Obtain
calories
per
gram
4186.8
joules
perkilogram
Fahrenheit
degrees
5/9
Celsius
degrees
orkelvins
1
inches
25.4
millimetres
poundsper
square
nch
0.006894757
megapascals
pounds
force)
4.448222
newtons
pounds
mass)
0.4535924
kilograms
poundsmass)per
cubic
yard
0.5932764
kilograms
per
cubicmetre
1
ToobtainCelsius
C )
emperatureeadings
rom
Fahrenheit
F)eadings,
use
he
following
formula: C
5/9)
F-
32).
Toobtain
kelvin
K)
eadings,
use:
K 5/9)(F
-
32)
+73.15.
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Introduction
Pozzolansare
materials
whichhave
little
or
nonherent
cementit ious
properties,bu t
which
develop
cementitious
properties
n
th e
presence
of
calcium
hydroxide(lime)
an d
water.Pozzolansh a v ebeenused
ince
Roman
t imesasngredients
of
l ime
mortars.
Such
pozzolans
were
usually
derived
fromnaturaldeposits,principallyvolcanic
ash.
Manymodernpozzolansar e
still
derived
ro m
natural
deposits,
bu t
th e
great
bulk
of
pozzolan
currently
n
usein
th eU SA
sderivedfromh e
combustionofpowderedoa lduring
electric
power
generation.
This
product
s
commonly
alled
ly
ash.
Th e
term
coallyash s
actually
morecorrect,
ince
othersourcesof
fly
as h
exist,
but
ar e
rarelyused
n
th e
construction
ndustry.
The
term
pulverized
fuelas hpfa)
s
usedn
Great
Britain.
There
arecurrently
three
classesof
pozzolandefined
by
th e
American
Societyfor
Testing
an d
Materials
ASTM):
ClassN,
ClassC ,
nd
Class
F.
Class
N
arenaturalpozzolans: calcinedhale,
alcined
volcanic
ash,
etc.
Class
F
s
fl y
as h
nominally
produced
ro manthracite,bituminous,
nd
om e
sub-bituminous
coals.
Its
required
to
show
t
least
7 0percent
SiOo
+Al
o
3
+
Fe-,0
3
on
chemical
analysis.
Class
C
s
nominally
produced
from
ly
as hderivedro m
combustion
of
ligniteand
om esub-bituminous
coals
ands
only
equired
o
showat
east5 0percent
SiOo
+
AUOj+
Fe^Oj
on
chemicalanalysis. Al l
ClassF
fly
ashalsomeetsClassCequirements.
Although
no t specificationequirement,CaOcontentof
fly
ash
sprobably
moreindicative
ofitsperformanceproperties
than
s
SiOo+
AloC^
+
Fe^C^.
C aO
contentsof
Class
C
ly
ashesarehigherthanClass
F
fly
ashes.This
C aO
often
forms
chemically
active
compounds
h atoftenconsiderablyaffect
performance
nportland-cement
concrete.
Many
Class
C
ly
ashesar e
hydraulic.
Class
N
pozzolansarerarelyused
nth eUSconstructionndustry,
largelybecauseof
th eseverelycompetit ivemarketpresentedbyth ecoal
ly
as h
ndustry.
Flyas hsanextremely
abundant
material. Total
U SA
production
n
9 8 3
w as52.4mill iontons,of
which3.6
mill iontonsw as
used
n
cement
an d
concrete
products
Mehta
1 985 ) . An
additional
5 .3
mill ionon s
w as
used
for
other
things,uch
as
m udstabilization,
agriculture,
ndawmaterialor
cement
manufacture,
h e
remaindergoing
to
an d
fillsDiamond
984 ) .
Not
al lly
as hs
ofsufficient
quali tyto
be
suitable
fo r
use
as
concreteingredient
but,except
n
temporarynstances,
here
s
no
shortage
of
quality
fly
ash.
Chapter Introduction
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Although
much
oncrete
is
still
madethatdoes
not
contain
fly
ash,
arelyis
fly
ash
prohibited
from
being
included.
Fly
ash
s
a
much
cheapermaterial
thanportlandcement,
o
thatlargereplacements
an
result
in
significant
economic
savings.
Dolen
(1987 )
estimatedthata
25
percentsavings
n
materials
ost
was
realized
n
the
constructionof
the
Upper
Stillwater
Dam
through
use
of
large
amounts
offlyash.
Fly
ash
was
first
usedin
concrete
inth eUSAin
th e
1932
Mielenz
1983).
Thefirstlargescaleuse
of
fly
ash
batched
as
aseparateingredientwas
in
th e
Hungry
Horse
Dam,
built
by
th eBureau
of
Reclamation
from
1948
to
1953 .
This
earlyuse
was
almost
exclusively
ofClassFfly
ash.
Class
C
flyash
has
becomeparticularly
abundant
in
recentyearsdueto
increased
use
of
lower
grade
coals
for
electric
power
production.Althoughthere
are
circumstances
where
a
particular
Class
C
flyash
maynot
be
appropriate,uc haswith
alkali-
reactiveaggregates,
or
in
high-sulfateenvironments,or
in
massconcrete,
th e
limits
of
his
material
are
nowreasonably
well
defined
see
EM
1110-2-2000)
anditis
nowmuch
morefrequentlyused
in
concrete.
Formany
years,
ommon
practicewas
to
use
fly
ash
as
part
of
th e
cementing
medium
n
concrete
(Mather
1968) .
Th e
Corps
ofEngineers
published
guidance
in1960(E M
1110-1-2007,
Leber1960)
indicating
that
pozzolan
shouldbe
usedwithcement
forpurposes
of
maximizing
economy.
At
one
time,
he
Corps
ofEngineers,n
EM
1110-2-2000(15Dec
65 ,
Table
V,
p.
60),
pecifiedClassF
fly
ash
replacements
forportlandcement
up
to
35
percent
(by
volume)
n
interior
mass
concrete
andup
to25
percent
inexterior
mass
concrete. Class
N
pozzolan
was
allowed
at
30
percent
and20
percent
replacement
levels,
espectively.
Thisguidance
was
modified
nth e1985
edition
of
th e
Standard
Practice,leavingth e
exactpozzolan
level
to
th e
judgement
of
th e
design
engineer.
Current
guidance
is
that
maximum
economic
advantage
of
fly
ash
should
be
usedwithin
th e
constraints
of
good
engineeringpractice.
Fly
ash
levels
in
Corps
ofEngineers'projects
have
largelyremained
t
about
30percent.
Iflargeramountscould
beused
withoutdetriment
to
engineeringpropertiesofconcrete,
then
considerable
moneycouldbesaved
onmaterialssinceth ecostof fly
ashislargelygovernedbytransportation
costs.
Also,
th e
recycling
of
a
wasteproduct
is
a
desirable
result.
R.E.
Davis,
who
was
one
of
th eearly
proponentsof
use
of pozzolan
in
concrete,
ecommended
hat
upto50
percent
replacement
ofportlandcement
might
be
suitable
forsome
flyash
Davis1950).Workat
th eWaterways
Experiment
Station
in
th e
1950's
(described
n
detail
below)
supported
th e
feasibility
of th e
use
oflargeamounts
of
fly
ash
n
lean
concretes
for
mass-
concreteapplications.Details
of
this
work
will
be
discussed
n
later
sections
of
this
report.
Since
then,there
appears
to
have
been
a
reluctance
withinth e
Corps
ofEngineers
to
incorporatehighlevels
offly
ash
replacement.
Thisis
probably
atleastpartially
aresultofanatural
aution
engineers
sometimes
exhibittowardsth euse
of
novelmaterialsorprocedures
in
circumstances
n
which
th ecost
of
failure
isvery
high.
However,
basedon
publishedreports
Chapter Introduction
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of
Corps
of
EngineersworkMather
1956)
nwhichlyash
was
used
or
as
much
s
60
percent
ofthe
cementing
mediumnmass
concrete,
om e
structures
werebuilt
nwhich
t
was
requiredthat
fly
shbe
50
percent
of
th e
cementingmedium.
On e
such
tructure
was
th eRevelstokeDambuilt
by
British
ColumbiaHydro.
The
purpose
of
this
eport
is
to
summarizeexperience
with
high
fly
ash
concrete,
both
asreported
from
aboratory
studies
and
frompublished
summaries
of
experience
in
construction.
Areas
n
whichncreased
research
is
necessary
will
be
identified
nd
a
tentative
outline
ofaprocedure
will
be
identified.
Chapter
Introduction
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2
ffects
of
Large
Quantities
of
F ly
Ash
on
Properties
of
Fresh
Concrete
Timeof
Setting
Setting
is
defined
s
th e
onset
ofrigidityin
fresh
oncrete
(Mindessand
Young
1981) .
Although
pecificevents
are
defined,.e .
nitialndfinal
setting,
he
processs
actuallycontinuouswithout
apparently
abrupt
changes
that
conform
to
theseevents.Initialnd
final
etting
arearbitrarilydefined
leveis
of
resistance
to
penetrationbyacalibrateddevice. However,they
are
usefulparameters
n
that
they
do
conform
to
approximate
properties
of
th e
concrete
thathavemeaning
with
respect
to
placing
and
finishing.Initial
time
ofsetting
approximatelyrepresents
theendof
theworkableperiod. Final
time
ofsettingapproximatelyrepresents
th e
time
whenmeasurable
strength
develops.
Specifications
seta
minimum
evel
or
initial
time
of
setting,
to
guaranteea
minimum
workingtime,
nd
set
amaximumevel
or
final
time
of
setting
of
Portland
ement,
o
guarantee
that
finishingandotherwork
canbe
continued
on
a
reasonableschedule.
Factorsthat
cause
small
hanges
n
time
ofsetting
may
not
be
ofimportance,
bu t
large
changesmay
cause
considerable
inconvenience
inplacing
andfinishing
schedules.
Portland
ement
s
th e
principalactive
ingredient
in
concrete
that
causes
setting.
For
purposesof
specification-compliance
testing,time
of
setting
is
measuredonpaste
specimens
according
to
ASTM
C
9 1ndC
266.
These
testsare
performedt
specifiedwater-cement
ratios,
onsequently
their
results
are
useful
or
comparative
purposesbu tmaynot
directly
ndicate
the
time
of
settingofa
concrete
made
with
th e
same
materials. Time
ofsettingis
strongly
affected
by
factors
whichoften
vary
nfield
practice,bu twhichare
held
onstant
by
these
test
methods,
uch
s
temperature,water-cementratio,
cement-aggregate
ratio,nd
hemical
nteractions
among
th e
ingredients
ofth e
concretemixture. Thesepaste-basedmethodsareuseful
or
detecting
changes
in
cementitioussystems
ndesults
are
probablycorrelated
with
changes
in
Chapter2
Effects
ofLarge
Quantities
of
FlyAshon
Properties
ofFreshConcrete
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concrete.
Time
of
setting
of
concrete
s
measured
according
to
ASTM
C
403,
whichuses
th e
mortarfraction
of
th e
concretefo r
testing.
Fiyas husually
has
tendency
to
retardth e
t imeof
setting
of
cement
relative
to
similarconcrete
made
withoutfly
ash.This
phenomenon
has
on g
beenecognizedbu tconsideredobeinconsequential
t
th e
levels
of
fl yas h
conventionally
used.
This
etardation
stems
ro m
t
least
tw o
apparently
independent
causes.
First,
eplacement
ofportland
cement
with
ly
as h
effectively
dilutesth ecement,
esultingn longer
hydration
t ime
necessary
for
th e
hydration
products
of
cementgrains
to
makeinterconnections.
Second,herem aybe
a
chemical
effect
onsettingt ime
that
results
fromth e
introduction
of
th efly
ash
nto
th esystem.This
beingth e
case,
t
would
appear
that
high
eplacements
of
portland
cement
byfl y
as h
would
causean
even
greater
ncreasen
settingt ime
relative
toconcreteswithmore
conventionaleplacements.
Not
agreat
dealof
work
has
been
published
describing
th eeffectof
high
flyas hcontents
on
t ime
of
setting.
These
ar esummarized
below.
Naik
1 9 8 7 )
examined
h e
effectof
35o55percentbymass)of
ClassC
fly
as h
ontime
of
setting.
Initial
im e
of
setting
increased
about
hr
for
each
10
percent
increasein
fl y
as h
content.
Final
im e
of
setting
increased
about
9 0m infor
every
10
percent
ncrease
in
fly
as h
content.
This
effect
w as
es s
pronouncedfor
rich
mixtures.
Ravina
and
Mehta1 9 8 6 )eported
ncreases
n
t ime
of
setting
from
few
minutes
o
fewhours.
The
effect
w as
most
pronouncedn
high-replacement
concretesm adewithClassC
fly
ashes.
Sivasundaram,
Carette,
an d
Malhotra
1990 )
nvestigated
tw o
ClassF
fl y
ashes
used
t
60percentbymass)of
total
cementitiousmaterial
t
a
w /c
of
0.31.They
found
that
nitialim e
of
setting
w as
notchanged
elative
to
control,bu tthatfinalim eofsetting
anged
ro m
to1hr,
which
w asabout
3
hr
morethan
controls.
Mukherjee,Loughborough,
an d
Malhotra
(19 82 )
found
that
37
percent
Class
F
fl yas h
bymass)
caused
m ax im u m
delayn
t imeof
setting
of
3hr.
Majkond
Pistilli
1 9 8 4 )eportedextensivetime-of-settingdata
forClass
C
based
mixtures
containing
upto
36
percent
fly
ash.
Control
setting
t imes
of
6to h r
depending
on
mixture)were
extended
up
to
2 .5
h r
at
th e
maximum
replacement.
W h e n
water-reducing
admixture
w asused
n
th e
mixtures,
setting
t imeswereextended
upto
6
hrfo r
th ehigherflyas hcontent
mixtures.
Ravina
an dMehta
1 9 8 6 )eported
ettingt ime
for
bothClass
C
an d
Class
F
based
mixturescontaining
up
to
5 0percentfl y
ash.
Initial
im eof
setting
w asncreased,elativetocontrol,
by
from
20m into4h r
an d
finalimeof
settingw as
ncreased
ro m o5hr,
with
th e
greatest
ncreases
occurring
at
Chapter
2 Effects
of
Large
Quantities
of
F ly
Ash
on
Properties
of
Fresh
Concrete
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higherreplacementsnd
with
he
ClassCashes. Leanermixtures
also
had
longer
setting
t imes.
Th eeffectof
replacementevel
w as
examined
t
W ESunpublished
data)
fromesultsoftesting
for
several
miscellaneousprojects
usingpastemethods
(ASTM
C
191 ,
C266 ) .
These
were
no t
controlled
experiments
nthat
variety
of
flyashes
ar e
represented
nd
each
w as
no t
epresented
t
each
replacementevel . Consequently,
conclusionsaredrawn
from
ess-than-
rigorous
analysis.
Results
ar e
expressed
s percentage
of
control
oput
resultson
a
morecomparable
basis. Th encrease
in
nitialim eofsetting
averagedessthan5 0percentof
control
or
ow
about
20
percent)an d
moderate35to
4 0
percent)eplacements,bu tncreasedo meanof
about
300percentof
control fo rhigh
about
7 0percent)eplacements.
However,
th e7 0percentconditionsw asepresentedbyonlytw o
ly
ashes. Th eeffect
onfinalim eof
setting
w as
omewhatess. Th encrease
averaged
about
25
percent
for
lowan d
moderateeplacementevelsan d
about
100
percent
fo r
th ehigh
eplacement
evels.
Figure.
Time
of
setting
versus
emperature,
woevels
of
cement
replacement
Fly
as h
eplacementevelprobablysignificantlynteracts
with
emperature
in
ts
effectof
t ime
of
setting.
Som e
llustrationof
th eimportance
of
this
interactionw asevealed
nother
unpubl i shed
work
conducted
tW ES
involvingt imeof
settingof
concreteASTMC403) .
Results
ar e
llustratedn
Chapter2
Effects
ofLargeQuantitiesofFly
Ash
on
PropertiesofFresh
Concrete
-
7/23/2019 Ada 294706
14/45
Figure.
Increasingamountsof
fly
ash
esulted
n
ncreasedimesof
initial
setting,whichwere
alsoaffected
by
temperature. Th efinalim e
of
setting
datawere
more
strongly
nfluencedby
both
lyashamount
an d
temperature.
Therehave
been
nstances
n
Corpsof
Engineers'
experiencewhenuse
of
large
quantities
of
Class
C
ly
as h
acceleratedh e
t imeof
setting
to
th epoint
where
placing
th e
concrete
w as
mpossible.
This
phenomenon
s
completely
opposite
to
th e
com m on
behavior,
which
s
to
delay
t ime
of
setting.
Little
s
knownabout
this
phenomenon,
bu t
since
ClassC
fly
as h
will
probably
increaseinuseinconcrete,thouldprobablybeinvestigatedfurther.
In
summary,hereappears
to
beno
doubtthat
t ime
of
settings
normally
delayed
byth ereplacement
ofportlandcementwithlyash
n
concrete,
bu t
th e
effect
is
no tlarge
fo r
low
tomoderatereplacementevels.
Th e
effect
appearsto
be
quite
large
for
high
eplacement
evels,
bu t
this
depends
argely
on
materials,
emperature,
nd
mixture
proportions.
Itsecommended
h at
preconstruction
testing
be
done
whenargereplacementsof
portland
cement
with
fly
as h
ar e
contemplatedo
determine
th e
magni tude
of
an y
t ime-of-
setting
problem.
Workability,
Water
Requirement,and
Bleeding
Theeffectof
large
amountsof
fly
ash
on
heworkability
of
cementitious
systems
sdifficulttoaddress
since
tscommonpract iceto
proportion
mixtures
to
desired
evelofworkability. When
th e
adjustment
nvolves
changingth ewater
content,
h e
relevantmeasurable
property
s
water
requirement.
Waterrequirement
sth eamountof
waterneededoobtain
defined
evel
of
workability,
expresseds percentageof
control.
Thus
workability
an d
waterrequirement
tend
obe
differentsidesof
th e
same
phenomenon. Theliterature
s
ather
extensiveon
th e
effects
of
fly
ash
on
theseproperties
fo r
conventional
evels
offlyashcontent,
bu tt
s
no t
so
extensive
forveryh igh
ly
ash
evels.
Water
requiredorconstantworkability
s
usually
ower
fo rtlyash-
containingmixtures,
bu tth e
amountof
watereductionvariesamong
ly
ashes.
At
conventionaleplacementevels,
Class
C
ashesgenerally
tend
o
affect
greaterwaterreduction
than
do
Class
F
ashesGeber
an d
Klieger
1 986 ) .
Valuesor
th e
formertendounclose
to9 0
percentofcontrol,
whi le
values
for
th e
latter
generallyunabove
9 5
percent
of
control. There
have
been
reports
of
fl yashesfrom
Australia
an d
ndia
that
cause
an
ncrease
n
water
demand
elative
to
control
Berry
1 979 ) ,bu tthese
are
apparently
uncommon.
Studiesdescribinghigh-flysh
concreteoften
tend
oeportworkability
effects
nqualitative
terms.
In
general,
here
seemsto
be
no
undueconcern
abouteitherworkability
or
water
requirementwithhigh-flyas hmixtures,bu t
differencesn
behavior
relativetoower-flyashcontents
have
beennoted.
Dodson1 9 8 8 )discussesh owwater-reducingadmixtureseem
o
ac t
n
Chapter
2
Effects
of
LargeQuantities
of
FlyAshon
Properties
of
Fresh
Concrete
-
7/23/2019 Ada 294706
15/45
reverse
ofnormalactionwhen
used
n
high-fly-ash
concrete. Someworkers
report
agluey Mukherjee.
Loughborough.
ndMalhotra
9 8 2 )
or
sticky.
consistency,
bu tth eeffect
w as
no t
severeenougho
nterferewithplacing.
Dunstan
nd
Joyce1 9 8 7 )eportedh at
th e
compactabil i ty
of
a5 0
percent
ClassFmixture
w as
little
more
sensitivetowater
content
than
th e
comparable
portland
cement
mixture,
bu t
no t
to
th e
point
of
constituting
a
practicalproblem. Ravinaan d
Mehta1 9 8 6 )used trowelingtest
an d
ound
ageneral
mprovement
nworkability
withncreasing
fly
ashcontents.
Th e
maximum
sh
content
examined
w as
50
percent.Thismprovements
probablydue
to
th e
effects
ofa
higher
volume
of
paste
n
hetly
ashmixtures
thatresulted
ro m
h e
mixtureproportioningtechnique.Tynes1966 )
reported
that
a
lean2 .5sack)
52
percent
fly
ash
mixture
tookonger
to
consolidatethan comparablecontrol
mixture.
Joshi
et
al .1 9 8 7 )foundhat
workabilityof
a
5 0
percent
mass)
eplacement
mproved ,
whenmeasured
by
th eVebe
AC I
1 992)
test,or
eight
fly
ashes
tudied.
For
ly
ashes
t
5 0
percentreplacementbymass) ,
They
foundh atthere
w as
considerable
variationamong
ly
ashes
n
effect
of
water-reducingadmixtures
on
l u m p .
For
high-fly
ashconcrete,water
requirement
decreases
withncreasing
fl y
as h
nea nmixtures,bu t
tends
to
ncrease
with
ncreasingflyas h
content
n
richermixtures
Cook
1 983 ) .
Mather1956 )found
reductionofwater
demand
with
ncreasing
ly
sh
contentorboth
0.5nd
0
w /c
mixtures
(Table
1) .
Table
Water
Requirement(lb/yd
3
)
or
EqualSlumpandAirContent
w/c
0.5,ich
0.8,
ean
no
ly
ash
265
281
30
ly
ash
247
261
45 ly
ash
235
261
60
ly
ash
236
254
Flyas hcouldpotentiallyaffect
bleeding
throughn
ncrease
nwater
demand
or
adelaynetting
t ime.
There
seemso
be
no
general
consensus
about
th eeffects
of
fly
ash
on
bleeding
either
at
conventional
eplacement
levels
or
at
higherreplacement
evels. Ravina
nd
Mehta1 9 8 6 )eport
that
there
isno
impleelationship
between
percent
ly
ash
nd
bleeding,bu t
that
th e
phenomenon
varies
with
source
of
fly
ash.
Verycoarse
fly
ashes
generallyperform
poorly
nthis
egard.
Tynes
1962 ,
966)
eported
no
problemswithbleedingthatcould
beattributedo
fly
ash. Som eofth e37
mixtures
examined
contained
more
than60percentflyash. Sivasundaram,
Carette,
an d
Malhotra1 9 8 9 )eportednobleeding
n
mixturescontaining60
Chapter2
Effects
of
Large
Quantities
of
Fly
Ash
on
Properties
of
FreshCone
-
7/23/2019 Ada 294706
16/45
percentClass
F
fly
ash,bu t
th e
w/c
was
low.Incontrast,McCoy
and
Mather
(1956)reported
that,
na45
percentfly
ashmixture,
bleeding
was
greater
thanin
control
mixtures
9percentv s.4 .5percent).
In
summary, workability,waterrequirement,
nd
bleeding
behaviortend
tobe
material
pecific
and
can
sometimesbea
problemwith
high-fly
ash
mixtures,
bu t
they
donot
appear
to
be
problems
nherent
to
such
mixtures.
As
withtimeofsetting,
preconstructiontesting
is
recommended.
AirEntrainment
Itis
well
known
that
th e
carboncontent
offlyashcan
have
an
impact
on
th e
air-entraining
admixture
dosage
required
for
a
desired
ai r
content.
Carbon
contentisrarelymeasured
on
flyash,bu t
is
approximately
indicatedbyloss
onignition(LOI)at
7 5 0
C .
Th e
general
belief
isthat
target
ai r
contents
can
beachieved
atalmost
anylevel
of
LOI,
bu tfor
fly
ashes
whose
LOI
exceeds
6
percent,
fairly
small
fluctuations
can
cause
problems
n
controlling
air.
The
effect
of
fly
ashreplacement
level
on
th eLOI-AEA
dosagerelationshipis
notwelldescribed.
DunstanandJoyce(1987 )
mentionedthat
control
ofai r
was
a
problem
in
a
50
percentflyashpavingmixture,bu t
this
was
not
quantitativelyrelated
to
th elevel
offly
ash.
oshi
et
al.
19 8 7 )
reported
significant
variationAEAdosage
requirementamong
several
fly
ashes
in
mixtures
containing
5 0
percentfly
ash,
but,
again,
t
was
notdemonstrated
thatthiswas
causedbyth ehighreplacement
level
and
thisphenomenonis
known
eveninmixtures
with
relatively
low
flyash
contents.
Mather
(1954)gavedata
on
air-entraining
admixture
demand
of
0.5
and
0.8
w /c
concrete
with
45
percent
replacement
ofeach
offour
Class
F
fly
ashes
having
carbon
contents
of
0.43,
3.17 ,
11.13,
and7.22
percent
respectively,when
used
with
tw odifferent
portlandcements.Whileth e
range
in
amount
ofadmixture
was
from
14 6to1214
mL/yd
3
,twas
noted
thatth e
rangedue
simply
to
change
in
cement
and
water-cement
ratio
was
from14 6
to
4 8 5 .
See
Table
2.
Chapter2 EffectsofLargeQuantitiesofF ly
Ash
on
Properties
of
Fresh
Concrete
-
7/23/2019 Ada 294706
17/45
Tab le
2
Air-entrainingAdmixtureDemandandDryingShrinkage
of
F ly
AshConcrete.
FromMather(1956)
Typeof
Cement
Water-
Cement
Ratio
Amount
of
Neutralized
VinsolResinRequiredoProduce6.0 .5
percent
Air
n
Concrete
with
-in
Aggregate,
L
per
cu
yd
No
Fl y
Ash
45
of
cement
eplacedbylyash
Fl y
Ash
0.43
carbon
Fl y
AshI
3.17
carbon
Fl y
Ash
V
7.22
carbon
F ly
Ash
II
11.13
carbon
II
II
a
a
0.5
0.8
0.5
0.8
485
265
248
146
348
242
248
162
647
410
531
339
886
500
732
428
1214
688
1026
601
Drying
Shrinkageof
Concrete
after
Storage
at
50 RH
and73.4
o80-DaysAge,
as
Thousandths
of
percent
of4-Day
Length
II
II
l
a
l
a
0.5
0.8
0.5
0.8
58
56
56
46
52
46
49
45
56
46
49
45
55
45
55
50
62
47
58
45
a
high-alkali
10
Chapter
2Effects
of
Large
Quantities
ofFly
Ashon
Properties
of
Fresh
Concrete
-
7/23/2019 Ada 294706
18/45
3
ffects
of
Large
Quantities
ofF lyAsh
onProperties
of
Hardened
Concrete
Strength
Strength
s
usually
a
property
of
concrete
of
interest,
eitherbecauseof
load-bearing
considerations
orbecause
of
th e
constraintlow
early
strength
developmentcanmpose
onconstruction
schedules.
Strength
s
oneof
th e
properties
ofconcreteon
which
flyashhas
notable
effect,
bu t
th esize
of
th e
effect
is
strongly
dependent
on
th ew/c.
Whenflyash
s
used
s
a
replacementfor
portlandement,
eductions
nearly
strength
elative
to
th e
pure
portland-cement
concrete
arecommon.
When
flyashsused
as
an
addition
(in
effect
a
replacement
for
fine
aggregate),
thisearly
reduction
is
commonly
not
evident.
A
third
procedure
is
to
replace
part
of
th e
portland
cement
andpart
of
th e
fineaggregate
withflyash. Also,considerable
adjustments
tostrength
development
can
be
made
by
modifying
water
to
cementratioscombined
with
us e
ofwater-reducing
admixtures.
When
used
sa
replacement
for
portland
ement,
lyash
basicallyacts,
at
earlyages,
s
diluent
of
portland
ement,
ontributing
little
directly
to
strengthdevelopment. However,
here
is
evidence
that
tly
ash
or
other
finely
divided
material)doesaccelerateth eearly
hydration
of
someportland-cement
phases
Beedie
et
al.98 9 ,
Domone1989) ,
othat
th e
observed
trength
s
somewhat
greater
thanexpected
from
the
volumetric
fraction
ofportland
cementpresent
n
the
mixture. Evenso ,
th e
strength
reduction
caused
by
replacement
of
portlandcement
by
flyash
s
approximately
linearly
related
to
th e
amount
ofthat
replacementup
to
th erangeof
60
to70
percent
replacement
see
Figures
2
nd
3) .
Therefore,
th e
prediction
of
early-age
strengthfor
aparticular
replacement
evel
s
relatively
simple
from
relatively
small
amount
of
data.
Th e
timeat
which
th e
tlyashbegins
tocontribute
to
strength
also
depends
on
th e
kindof
th e
flyash.
This
varies
from few
days
or
sooner,
for
Class
C
fly
ashes,
o
a
few
weeks,
or
Class
F
flyashes.
Strengths
then
gradually
increasewith
espect
to
the
control.
Whetherthe
strength
of
th e
fly
Chapter
3
Effects
of
LargeQuantities
of
FlyAsh
on
Properties
of
Hardened
Concrete
11
-
7/23/2019 Ada 294706
19/45
7,000
6,000
5,000
h lfe
2,000
1,000
0
10
20 30 40 50 60 70
PercentReplacement
Figure
2. Strength
versus
percent
eplacement
ofcement
with
ly
ash
w/c = 0.5
3,000
2,500
2,000
a,1,500
c
s
3 5
1,000
50 0
\
jdn
,
X^JSOdv
\ dy
\
\
\28diy
N.
\7diy
X
O
111
0 1020 30 40 50 60 7
Percent
Replacement
Figure
3. Strengthversuspercent
eplacement
of
cement
with
ly
ash,
w/c
= 0.8
12
Chapter
Effects
ofLarge
Quantities
of
Fly
Ash
on
Properties
of
Hardened
Concrete
-
7/23/2019 Ada 294706
20/45
ash-port landementmixturesultimately
equals
or
exceeds
that
of
th e
control
mixturewithout
fly
ash
depends
on
th emixture
designprocedure,h etype
of
fly
ash,
nd
h e
water-cement
atio.
W h e nth ereplacement
s
with
ClassF
fly
ash,
ult imate
strengthsrarely
reachthose
of
th e
control
mixtures
unless
th e
percenteplacement
sow
(about
15
percent)
Mather
1 968 ,
Cook
9 8 3 ,
Sivasundaram
et
al .
1990 ) ,
Joshi
et
al .9 8 7 ) .
Inth e
case
of
high
eplacements,
h e
ult imatestrength
m ay
no t
exceed 0
percent
ofth e
control
mixture,
sllustratedn
Figures
2nd3 ,
taken
from
Mather
1965) .
Thiss
probably
dueto depletion
of
calcium
hydroxiden
th e
system.
Thiseffects
no t
apparent
whenow
water-cement
ratios
are
used,ssdescribed
below
n
th e
considerableliterature
on
uchof
mixtures.
Flyas heacts
with
calcium
on
n
th e
poresolution
ofconcrete
an d
water
toformhydrationproductsC S H )thatcontributetostrength.Th
ecalcium
hydroxide
comesro mh e
hydratingportland
cementfractionof
th emixture
an d
m aybeinimited
upply .
Helmuth
1 9 8 7 )calculatedhat,
now-calcium
(Class
F)
flyas hmixtures
containingsittle
asabout
22percent
fly
ashby
mass) ,
h efl yash consumesllof
th ecalciumhydroxide
produced Dodson
( 1 9 8 8 )
calculated
thisfigure
to
be20percent
fly
ash,
bu t
th eexactfigure
probably
varieswithcementince
cementchemistryaffects
th eamount
of
calciumhydroxideproduced.
No
matterwhichportlandcement
sused,ts
probablethat
calcium
hydroxide
would
becomeimitingthigheplacement
levels.
Class
C
ly
ashes
ypicallycontain
ubstantial
quantities
of
calcium
compoundsndheseoftenesultnconsiderable
amounts
of
l imebeing
introduced
ntoth e
system
elativetoClass
F
fly
ashes.
Therefore.
Class
C-based
mixtureshould
no t
become
o
easily
im e
estricted
nd
ultimatestrengthsof
high-replacement
mixturesarelikelytobehigherfo r
Class
C-based
mixtures
han
or
Class
F-based
mixtures.
Berryet
al .
1 9 9 2 )
also
discussest
om e
ength
h emechanism
by
which
high-flyas hconcretesgaintrengthtearlyages,
apparentlybeyondhe
level
expectedro m
h e
portland
cementraction They
conclude
thatchemical
reactions
between
th e
pore
flu ids
an dhe
amorphoussilico-aluminateglasses
occurstoappreciable
degreeeventearlyagesan d
with
argereplacementsof
portland
cementwith
ly
ash.
Calciumhydroxidecontinued
o
be
abundant
through8 0days,h e
last
ag e
data
were
collected,
ndicatingno
imitat ion
n
reactiondue
to
depletion
ofthis
phase.
In
Part
2
of
th e
same
work.Zhang
etal .
1 9 9 2 )
concludedh at
ly
sh
actss react ivemicroaggregatean d
h at
completehydrationofth e
fly
ash
particlesdoes
no t
occur.
Also
n
he
case
of
ClassF
ly
ashes,
here
appears
to
be
a
etardationof
strengthdevelopment
beyondhatexpected
ro mimple
dilution
ofth e
portland
cementduringth e
first
clay
or
two.
whichhendisappearsafter fe w
days .
This
appears
s
negative
trend
n
h e
strength-versus-time
curve
when
strengthsexpressed
s percentageof
th e
controlFigure4 ).
Chapter
3
Effects
of
Large
QuantitiesofFlyAsh
on
PropertiesofHardened
Concrete
13
-
7/23/2019 Ada 294706
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110
10 0
,o
y
c
o
)
c
k
c^
.--''
S
e
h
p
/
Class
F
g >70
to
to
C D
Q.
E
o
60
/
w
y
6/
50
)
20
40
Age(t
Figure4. Strength
percent
of
control)
versusag eforfour
fly
ashesat
30percenteplacement
of
cement
Dunstan19 8 1A ,9 8 3 )
nvestigated
he
elationshipsbetweenw /cnd
strength
change
with
he
substitutionof
a
argequantitiesof
fly
ash.
Changing
th ew /c
has stronger
effect
on
cement-fly
as hmixtureshan
t
does
on
pure
portland-cement
mixtures.
For
example,
above
a
w /c
of
0.54,
60percent
fly
as hw asoundomakenocontributionostrengtht
7
days .
At
w/c'sgreater
than0.70.
ly
ash
makesnocontributiontostrengthuntil
28
days .
In
summary,
simple
eplacement
of
portland
cement
withly
as h
causes
predictablereductionsn
early
strength
ndom eeductions
non g
term
strength,
bu t
with in
eason,
strengths
an
be
engineered
or
most
ly
ash
levels
by
choice
of
fly
ash,
manipulation
of
w/c,
ndcementit iousmaterials
content
ofth econcreteaccording
tobasicconcrete
principles.
Considerable
laboratory
work
m aybe
requiredo
dentify
th e
patternsor
a
given
etof
materials. Such
aboratorywork
squite
expensive
toexecutewhen
performed
onconcretes.
However,
tsikelythatfo r
a
given
et
of
materials,concrete
and
mortarstrengthswill
becorrelated. Ifreasonably
accurate
estimates
of
regression
coefficients
anhe
made
by
makingonly
14
Chapter
Effects
ofLargeQuantitiesof
FlyAshon
Properties
ofHardenedConcrete
-
7/23/2019 Ada 294706
22/45
fe wconcretemixtures,
henconsiderableexplorationof
th e
effects
of
variationsnmixturedesign
on
trengthanbemadeusingmortarsnd
t
very
ittlecost.
This
approach
wouldbeparticularlyattractiveftturnedou t
that
th e
relationshipsbetweenmortar
nd
concrete
properties
were
inear.
Thenvery
few
concrete
mixtureswould
be
required
ocalibrate
th e
relationship.
Followingare
brief
summaries
of
strength
tudies
an d
ummaries
of
construction
projects
that
nvolved
concretecontaining
highvolumesoffly
ash.
S o m e
ofth every
early
work
on
th e
effect
ofhighcement-replacement
levels
withpozzolans
on
elatively
ean
concretesw as
conducted
t
W ES
during
th e
1950's. McCoy
an d
Mather1956 )eported
esultsof
field-scale
concrete
tests
5
t
by
ftby
10ft
blocks)
fo r
mixturescontaining45
percent
Class
F
fly
ash
by
solid
volume)
using n.nd
6
n.aggregate. Total
cementit ious
materials
contents
were
about
200
b/yd
3
ndhew /cw as
0.80.
Strengths
t
7 ,
28 ,nd9 0dayswereabout600
psi .
150psi.
nd9 10
psi .
respectively. These
were
31ercent.
5 8
percent,
nd0percent
of
control,
respectively.
Aggregatesize
had
ittle
effect
on
trength. Suchstrengthswere
onceconsideredo
be
reasonablyadequatefo r
mass
concrete(Tynes
962) ,
although
higherstrengthsar e
no w
usually
specified.
Tynes1966 )eportedcompressive
strengths
of
laboratorymixtures
containing
9 4
b
of
cement
and
additional
Class
F
fly
asho
that
th e
flysh
rangedro m
52
o71percentbymass)of
th e
total
cementit iousmaterial
(totalcementitiousmaterials
variedro m
9 4
to
319
b/yd
3
). Control
mixturescontained
8 9
b/yd
3
of
cement. Strengths
t
daystendedobe
substantiallyower
thancontrol
t
3days
about
60
percent)
bu t
strengthst
9 0
days
had
exceeded
control
t
9 0
days .
The
range
of
3-day
strengths
among
ll
ly
as h
mixturesw as
5 9 0
ps i
o
60
psi.
Th e
range
of
90-day
strengthsw as2480
to
3 0 7 0
psi .
Water-cement
atiosangedro m
0.4
to0.6.
Strengthstendedoncreaseateachag e
with
ncreasing
amountsof
fly
ash.
except
for
th e71
percentmixture,
whichhowedom e
strength
oss. The
strength-increase
patternprobably
esulted
ro mh eincrease
n
paste
fraction
dueto
ncreased
ly
ash
contentand
educedwater-cementatio. Th e
decrease
at
th e
highest
ly
ash
percentage
w as
attributed
oim e
deplet ion.
Tynes1966 )
further
reportedh at
ield
blocksmade
with
hese
same
mixtures
gavesomewhatowerstrengths
than
hesamemixturen
aboratory
tests(
-
7/23/2019 Ada 294706
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16
aw /cof
0.8. Strengths
weremeasured
o
0yrs. At60percent
eplacement
with
ClassF
flyash,
trength
elat iveto
control
varied
ro m
about
30
percent
at
early
agesaew
days)
toabout60
percent
t
tenyears. Generally,
strengthsof
al l
ly
ashcontaining
mixtures
were
es sthan
control,
event
0
years.
This
work
t
W ES
w as
directed
primarily
t
exploring
use
of
pozzolan
replacements
or
mass
concreteapplications. It
w as
concludedh at
even
relativelyhigheplacement
evelswerereasonablefo rthisapplication,
bu t
apparently
no
structureswereconstructed
usingsubstantially
more
thanh e
30
to
35
percentm ax im u m
ecommended
by
Corpsof
Engineersguidance
until
n
th e1980'swhen4 0to
50
percent
ly
ashw as
usedn
constructionof
th e
Ol d
RiverControlAuxiliaryStructurean d
neveralnavigat ionstructures
on
th e
Re d
River,
ll
n
Louisiana.
The
earliest
use
of
high
ly
sh
contents
w as
eported
byM.R.E.
Dunstan
( 1 9 8 1 B )for
use
nroller-compacted
concrete
and
orth e
structural
concrete
used
n
th e
slip
formingof
th eexterior
concreteused
n
this
typeof
construction. Rollercompacted
concretes
relatively
owwater-cement
atio
material
hatmust
contain
high
paste
fraction
oradequatebondingbetween
layers. High
eplacementevels
of
portlandementwithly
ash,or
other
pozzolan,ar e
thennecessarywhenh istechnology
s
used
n
mass-concrete
applications
to
control
heat
of
hydrat ion.
Mixture
design
workpursuantto
construction
of
Milton
BrookDam
ndicatedh at
flysheplacements
of
7 0
to 0
percent,
by
volume,nd
otalcementitious
materials
of
4 5 0
b/yd
3
o
be
optimum
Dunstan
983 ) .
In
collateral
aboratory
nvest igat ions
concerned
withuse
of
highly
as h
replacements
n
structuralconcrete,
Dunstan
1 9 8 3 )
found5 0
percent
replacement
evels
not
toohigh
o
yield
easonable
early
trength
e.g.
4200
psi
t
days).
Such
strengths
areachieved
hrough
reasonably
high
paste
fractionan d ow
w /c
about
0.25),
equiring
use
of
a
high-range
water
reducer.
Dolen1 9 8 7 )documentedheroller-compactedconcrete
used
nth e
constructionofUpperStillwaterDam. Fly
ash
Class
F)
comprisedup
to
65
percent
of
th e
cementit iousmaterial .
Early
strengthw as
considerably
lowerthanforth eequivalentpureportland-cementconcrete,
bu t
ater
strengthswerehigher. Inthistypeof
constructiontechnology,
ow
early
strengths
arenotmportant
because
higher
early-strengthconcretes
used
or
thefacingmaterial
h atservess formorth elower-strength
ill. Lower-
than-expectedstrength
gain
w as
experienced
during
on e
construction
eason.
which
w asattributedohecoarsenaturelargepercentageetained
on
45-sieve)of
someof
th eflyshused.
Recent
aboratory
tudies
havefocused
on
ways
o
use
arge
quantitiesof
fl y
as h
bu tyet
stillget
high
earlystrengths.
These
have
mostly
exploitedow
water-cementitious
materials
atios.
Chapter Effects
of
Large
Quantities
of
Fly
Ash
on
Properties
of
Hardened
Concrete
-
7/23/2019 Ada 294706
24/45
Majkoan d
Pistil
i
1 9 8 4 )
eported
he
effectsof
replacingvarious
proportionsof
portland
cement
on
mass
basis)
with
Class
C
ly
ash.
For
equivalent
cementplus
fly
ashcontents,approximatelyequal
strengths
were
obtainedegardless
of
th e
flyashpercentage.
This
generalizationappearedo
holdortotal
cementit iouscontentscementplus
ly
ash)
n
th erangeof
4 00
to600
b/yd
3
. Higherreplacement
mixturesequired
ower
w/c's
to
achieve
this
equivalency,
bu tth e
amount
of
W RA
equired
w as
constant.
Apparently
water
reducingeffectscontributedby
he
flyashallowedh e
additionalwater-
reductionwithoutadditional
WRA.
Probably
because
of
th e
relativelyow
water-cementatiosrangedro m
0.34
to0.46),strengthsabove1000
ps i
t
1
day
an d
above
3000
ps i
t
28dayscouldbeachieved
with
widerangeof
cement-flyas hproportions.
Much
higherstrengthsthan
hese
wereachieved
at
th ehighestcementplus
ly
ash
contentsand
t
th e
lowest
water-cement
ratios. The
opt imumly
ash
percentage,
defined
s
thatpercentage
thatgives
th ehigheststrength
t
given
age,
appeared
o
differ
with
h e
presence
or
absence
of
W R A .
Naik
1 9 8 7 )
conducted
aboratory
nvestigationon
series
ofmixtures
usingTypeportlandcementndClassC
ly
ash.
Fly
ashcontentswere
0
percent
to
60
percent
bymass).
Total
cementitious
materials
content
w as
nominally450,550 ,
an d
65 0b/yd
3
,
although
h isvaried
om e
with
ly
as h
levels. Strengths
ncreased
with
cementplus
fly
ash
content,
sexpected.
However,very
ow
early
strengths3
and
days)
were
measured
t
th e
highestcement-replacement
evels5 0,60percent).Thiseffect
appeared
o
getworse
at
th e
highest
total
cementit ious
materials
contents. Th eauthor
attributedh is
to
th e
cylindersbeing
green when
tested.
For
th e
65 0lb/yd
3
mixtures,h isgreenperiodpersistedteastthrough
days .
Thesemixtures
then
gained
strength
very
apidly
once
they
passed
hegreen period.
Malhotra
an d
associates
havepublished
esults
of
several
tudies
concerningstrength
n
high-fly
sh
concretes.
Malhotra
an dPainter
1 9 8 8 )
investigated
strengthdevelopmentof
portland
cement-fly
shmixturesn
which
h e
fly
as h
proportion
variedro mabout4 0percentto
60
percentby
mass .
ClassF
fly
as h
w as
used. Portlandcementcontent
w as
held
constant
at
15 0
kg/m
3
262
b/yd
3
). Watercontent
w as
also
heldconstant.
Cement-fly
as hproportionswere
realized
byimple
addit ion
of
flyash. This
design
procedurethennecessarilyesulted
nhighertotal
cementitious
materials
contents
an d
ower
w/c's
spercent
fly
ashw as
ncreased. Water-cement
ratioswere
kept
lo w0.28-0.42)
usinghigh-range
water
educer.
Three-day
strength
varied
ro m
100
ps io
2300
psi. Twenty-eight-daystrengths
varied
from
2300
ps i
o
5300
psi. Ninety-one-day
strengthsvariedrom2 8 3 3
psi
o
6700
psi .
In
each
case,
h e
higher
range
of
strength
w as
obtained
t
th e
highest
fl yas hcontent,
which
w as
alsoth eowestw/c.
In
anotherstudyMukherjeeet l.
1 9 8 2 )examined
concretecontaining
37
percentClass
F
fly
ash,by
mass ,
usinghigh-range
water
reducer
to
get
a
water-to-cementitious-materials
atioof0.35. Strengthswere
7 0
percentof
control
t
7
days
and
9 0percentof
control
t
28
days .
Chapter3
Effects
of
Large
Quantities
of
Fly
Ash
on
Properties
of
Hardened
Concrete
17
-
7/23/2019 Ada 294706
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18
Langley,
Carette,
ndMalhotra1 9 8 9 )
examined56percent
ly
sh
concrete. Earlystrengthswereowerthancontrol,bu ttherew
asignificant
strength
gain
after days. Propertiesof
th e
tly
ash
allowed
om ewater
reduction,
which
contributed
o
trength
properties.
Sivasundaram
et
l.1 9 8 9 )
conducted
s imi lar
studyat
60percentfly
as h
an d
noted
h at
strength
of
cement-fly
sh
mixtures
w as
ess
than
control
even
at
on e
year.Theyattributed
om e
ofthis
to
greater
sensitivity
of
these
mixtures
o
moist
curing.
In
other
work,
h e
same
authors
Sivasundaram
et
al .990)
concludedhat
highly
ash
contents
worked
well
bu t
thatthere
w asconsiderablevariationamongly
ashes,
strengthswerenot
critically
dependent
on
otal
cementit ious
materials
contents
ateast
at
th e
low
w /c
used
in
these
studies),
ndveryh igh
dosages
of
high-rangewaterreducerwere
required
t
th e
low
w/c's
usedn
thistudy
0.22
nd
0.33).
Giaccio
an d
Malhotra1 9 8 8 )ooked
tth eeffect
of
beneficiationof
th efl y
ash
removal
ofmaterial
arger
than
45
microns)
on
strength
developmentof
lo ww /c0.32),
high
lysh56
percent
bymass)concretes. ClassF
fly
asheswere
used.
Strengthsweregoodwith
ll
lyashesandhere
did
not
appear
to
bemuch
effect
on
trength
duetobeneficiation. They
also
eport
flexural
ndsplittingtensilestrengths.
Sivasundaram,Carette,
nd
Malhotra
1 990)ooked
t
ong-term
trength
using
corestaken
rom
cube
of
concrete
1.5
.5
.5
m ). Th e
mixture
contained
5 8 0
b/yd
3
ofcement
+
lysh
5 6percentClass
Ffly
ash
by
mass)
t
a
w /cof
0.28.
Th e
concrete
eached
3
percent
of
ts3 .5
year
strength
(~
10,000psi)by9 0days. Modulus-of-elasticity,pulse-velocity,
nd
temperature-rise
datawere
alsoeported.
Joshi
et
al .
1 9 8 7 )
ooked
t
lyashes
t
5 0
percent
replacement,
by
mass .
Class
C
based
mixtureshowed
ult imate
strengths
thatwere
higher
thancontrol. Class
F
based
mixtureshowed20to
30
percent
ess
strength
than
controlst
ate
ages.
Mixtures
containing
H R W R
andAEA
howed
ess
strengthh anmixtureswithouttheseadmixtures .
In
work
on
om eof
th e
samely
ashes.
Da y
1990A)
nvestigated
he
effects
of
curing
emperature
and
evaluatedos t
actors
associated
with
replacement
evel. Strength
of
fly
sh
mixtures
esponded
moretoearly
elevated-temperature
curing
han
did
controls,
bu t
fly
ashmixtureswere
more
retarded
noldh anwerecontrols. Th e
cost
of
makingconcretetendsto
decrease
withncreasing
fly
sh
content,
whetherthisscalculatedon
a
per-
yard
basis
or
on
n
equivalent-strength
basis
se e
Figures
nd
6).
Heat
of
Hydration
Theheatevolvedduringhydration
of
cementitious
materials
s
mportantn
mass-concreteconstructionbecause
of
th e
thermaltressesthat
ca n
develop.
Chapter Effects
of
Large
Quantities
of
FlyAshon
Properties
of
HardenedConcrete
-
7/23/2019 Ada 294706
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65
60
55
u
.O
3
u
8
S50
u
45
40
VS.
} 10 20 30 40 50 60
%
F ly
Ash
(Mass)
FlyAshl RyA*h2
Figure
5.
Cost
of
concreteat
various
fly
as h
contents
1. 7
1. 5
1. 3
K
o
n
\
20
0
0
%By
Ash
(Mass)
RyAh1
Fl y
As h
2
50
0
Figure
6.
Cost
of
concretepe rM Pa
at28
days
at
various
fly
as h
evels
Chapter
3
Effects
ofLarge
Quantities
of
Fly
Ash
on
Properties
of
Hardened
Concrete
19
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7/23/2019 Ada 294706
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Corps
of
Engineersguidance
has
sought
to
controlthis
byeither
setting
limits
on
th e
heat
of hydration
of
th e
portlandcement
or
by
recommending
use
of
ClassFflyash
in
th emixture,orsome
combination
of
thesetw oapproaches.
Controlling
th e
thermal
tress
problem
is
more
complicated
than
setting
limits
on
materials.
This
phenomenon
is
dependent
notonly
on
th e
heat
evolved
by
th ecementitious
materials,
bu t
also
on
th eamount
of these
materials
n
th e
concrete,
th e
placing
and
curing
temperatures,
nsulation,
dimensions
of
th e
placement,
heat
capacity
ofaggregates,nd
coefficient
of
thermal
expansion
ofth econcrete.
Analytical
approaches
to
thiscomplex
problem
exist,
bu t
they
are
somewhat
expensive
touse.
Practice
has
been
to
useth eheat
of
hydration
of
th eportlandcement
at
7days
asth e
standard
for
determining
whether
a
cement
is
adequate
for
use
in
mass
concrete
construction.
This
specification
is
generallyset
at
7 0calories
per
gram
of
cement,s
perASTMC
150.
Someproject
specificationshave
allowedthis
to
beincreased
to8 0
calories
per
gram
fClassF
flyash
is
included
as
a
partialportland-cement
replacement
in
th e
concretemixture.
Therationalefo r
this
modification
isthat
ClassF
flyash
replacement
of
portland
cement,nth e
amounts
conventionallyused
(2 0
to30
percent),
will
usually
result
in
a
heat
of hydration
of
th e
combined
ementitious
materials
of
lessthan7 0
cal/gif
th e
cement
evolves
less
than
8 0
cal/g.
Other
project
specifications
maintain
th e
requirement
of70
cal/g
fortheportland
cement
and
thenfurtherspecifyuse
of
Class
F
fly
ash,
othatth eheat
of
hydration
of
th ecombined
materials
s
less
than
7 0
cal/g.Sometimesportlandcements
showconsiderable
variation
in
heat
of
hydration,
o
that
when
replaced
at
30
percent
byClassF
flyash,
th e
resulting
heatofhydration
of
th e
mixture
m ay
beas
low
as
50
cal/g.
Early
strength
gain
is
often
aproblemwith
such
mixtures.
No
heat
of
hydration
requirements
are
pu t
on
fly
ash
even
though
some
ClassC
fly
ashes
evolve
heat
comparable
to
portlandcement.
The
approach
taken
in
developingprojectspecifications
is
generally
to
determineth eeffect
on
heat
evolution
ofvarious
replacements
ofcementby
fly
ash.
This
s
done
alongwith
strength
gain
determinationsndthenan
optimum
eplacement
level
hosen.
Use
of
Class
Ffly
ash
in
largereplacements
was
investigated
by
Tynes
(1962,1966).Fly
ash
contentsvaried
from52
percent
(bymass)
to
71
percent.Table
3
summarizes
esults,
expressedas
percentof
control.
Table
3
Heat
of
HydrationofHigh-FlyAshMixtures,%
of
Control
Reference
%
F ly
Ash
3
D ay
28
D ay
365D ay
Tynes
1962)
52
71
51
48
67
53
Tynes1966)
52
71
70
39
66
49
20
Chapter
3
Effects
of
Large
Quantities
of
Fly
Ash
on
PropertiesofHardenedConcrete
-
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The
results
eportedn
these
tw o
tudies
ar e
consistent
n
that
arge
reductionsnheat
evolution
wereobtained
with
arge
fly
sh
contents
an d
thesereductionscontinued
obeexpressed
taterages. There
w as
considerablevariationamongcondit ionsconcerninghowth
erelativeamount
ofheatevolvedchanged
with
ime. There
appeared
o
be
little
t ime
dependence
fo r
some
mixtures
whi le
others
howed
n
elative
ncrease
n
heat
evolvedwith
ime.
Som e
ofthis
ambiguitym ay
be
due
to relatively
arge
experimentalerror.Replicate
data
were
not
reported,
o
that
experimental
errorcouldnotbeest imated. Th emethod
ormeasur ingheat
of
hydration
(ASTMC18 6 )snherently
quite
variableas
t
scurrentlydescribed,
an d
w as
purportedly
morevariable
at
he
t ime
whenthese
studieswere
completed.
Unlesssome
compensationor
this
arge
error
s
employed,uchs
comparingaverages
of
replicate
data,
esults
anappearnconsistent.
Reinhold
et
al .1 9 8 6 )eported -
nd
28-dayheat
of
hydrationdatafo r
10
pozzolansblended
with
2
cements
Type
nd
I)t
30
percent
an d
60
percentreplacements,
by
volume.
Th epozzolans
ncluded
6Class
F
fly
ashes,2ClassClyashes, i l ica
fumes,
nd lassNpozzolan. There
w as
considerable
variation
among
pozzolansn
contribution
o
heatevolution.
Multiple
regression
analysis
of
th eeffectsof
th e
properties
of
th e
fly
as h
on
relative
heat
of
hydration
percent
of
control)
showed
h atpercent
replacement,C aOcontent,
and
Blaine
fineness
accountedormostof
th e
variation
among
materials. Th eregressionequations
ar eas
follows:
HH
ldm
{
%
c
ontrol) 6 .72/? MCaO
0.00027
HH
Mav
( control)
4
0.56/?0.62G/O0.0030B
whereR
sth epercenteplacementof
portland
ement
by
pozzolan,by
volume,
ndBs
th e
Blainefinenesscm
2
/
g). Th e
mult iple
correlation
coefficient
r)
w as
0 .82orth e
7-daydata
an d
0.89or
th e
28-daydata.
The
tw oequationsaresimilarexceptorth ecoefficientrepresentingth
eeffectof
percentreplacement. Thiseffect
w as
much
strongerat daysthant
28
days.
Thiss
easonable
since
many
pozzolans
eact
very
ittleatearly
ages,
acting
verymuchs s imple
diluent
ofth eportland
cement.
Pozzolans
with
very
high
C aO
contents
evolved
about
s
much
heat
as
th e
portland
cement.
For
example, ClassC
ly
ashwith
29
percent
CaO
evolvedheatequalo
9 9
percent
of
controlt7daysan d9 6
percentof
control
at
28
dayswhen
t
30
percenteplacement,
nd
0 1
ercentofcontrol
t
7
days
an d
7
percentof
control
t
28
dayswhen
t
60percent
eplacement.
Similar
esults
wereobtainedwithdifferent
materials
by
Pooleet
al .
1990 ) .
Chapter3
Effects
of
Large
Quantities
ofFly
Ash
on
Properties
of
Hardened
Concrete
21
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Inunpubl i shed
worktW ES
hat
examined
heat
of
hydrationtearlier
ages,
t
w as
foundh at
even
or
high-CaOflyashes,
om e
eduction
nheat
w as
achieved
ton e
an d
hree
clays,
whi le
7-day
esults
were
comparable
o
control
values. Th e
relationship
between
eduction
nheat
of
hydrationnd
flyas hcontentw asinearatearly
ages
fo ral lmaterialstudied. Thisinearity
tendedodisappear
with
age,
irst
nhecase
ofth eClassC
ly
ashesnd
then
with
h eClass
F
ashes
Figure
7 ).
80
70
1 5
6
c
r o
-a
>,
X
o 50
C D
C D
40
30
v
-Q.,
N
~~ o
~Q
Class6
7
da y
Class
F
~ ~ .
da y
10 20 30 40 50
%FlyA sh
(b yvolume)
60
Figure7 .
Heat
ofhydrations
percent
flyash,
comparison
of
a
Class
an dClassflyas h
In
summary,
heat
of
hydration
measurementsar eno t
completely
adequate
to
describe
early
thermal
behavior
of
concrete,
bu tthey
are
a
useful
guide
to
relativethermal
behaviorof
materials.
Th e
effect
offly
ashon
he
heatof
hydration
of
portland
cement
ystems
varies
with
properties
of
th e
fly
ash.
Fly
ashes
with high
CaO
content
orthatar e
very
inelydiv ided
contribute
significant
amounts
of
heat
by
days.
Low-calciumly
ashes
continue
to
provide
reductions
n
heat
evolut ion
t
ater
ages.
Heat
evolut ion
of
high-fly
as hmixtures
appears
tobe
reasonablyepresentedby
n
extrapolation
of
behavior
oflower-fly
ash
mixtures.
22
Chapter
Effects
of
Large
Quantities
of
FlyAsh
on
Properties
ofHardened
Concrete
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Creep
Th e
effect
offlyasheplacement
ofportland
ement
oncreep,th eslow
continueddeformation
under
loadLea
1970),
does
not
appear
tobe
well
documented.
In
general,
onditions
that
increase
drying
shrinkageand/or
reduce
strength
development
rate
tendto
ncrease
creep
Mindess
and
Young
1981 ;
Lea
1970).
However,
herearea
number
ofqualifiers.Th e
tendency
of
a
given
concreteto
creeps
nota
static
property,
bu t
varies
withage,
im e
ofloading,emperature,
nd
uring.
Therefore, general
tatement
about
th e
effects
of
fly
ash
maybe
difficult
to
develop.
Onlythree
citations
were
found
that
addressed
reep
n
high
flyash
concretes.
In
Reinhold
et
al.
1986) ,
Class
C
and
ClassFflyash
were
examinedt30
percent
and
60
percent
replacement
evels.
Th e
specific
creep
increased
with
ncreasing
flyash
eplacement
when
specimens
were
loadedat
7days. ClassF-basedmixtures
howed
slightly
morecreep
thanClass
C-
based
mixtures.
When
thespecimens
were
loaded
t
28days,there
was
no
increasein
creep
of
fly
ash
specimenselative
tocontrols.
Swamy
and
Mahmud19 8 9 )
found
essentially
no
effect
due
to
fly
ashn
50percentClass
F
concretes.
Da y(1990B)examined
Class
F
and
2
ClassC
fly
ashesat
up
to50
percentof
cementitious
materials
bymass).
Specimens
were
loadedn
both
wet
anddrycondition. Hefoundthat
creep
was
reducedrelative
to
controls.
DryingShrinkage
Summarizing
earlyexperiencewith
concrete
tests,Davis
1950)
reported
that
fly
ash
generally
causes
an
ncrease
in
drying
shrinkage,
except
when
it
is
ofalow
carbon
contentand
high
fineness.
Berry(1979 )
reported
that
fly
ash
in
practical
proportions
doesnot
significantly
nfluence
drying
shrinkage
of
concretes. These
apparent
discrepancies
maybe
due
to
differences
n
methods
or
mixture
properties.
Helmuth
19 8 7 )
