Fracture Mechanics of Concrete and Concrete Structures High Performance, Fiber Reinforced Concrete, Special Loadings and Structural Applications- B. H. Oh, et al. (eds)
ⓒ 2010 Korea Concrete Institute, ISBN 978-89-5708-182-2
Experimental research on high-fluidity and super high-early strength
concrete for cement pavement repairing
*
D.P. Chen & C.L. Liu
Anhui University of Technology, Ma’anshan, China
C. X. Qian
Southeast University, Nanjing, China
ABSTRACT: The concrete for pavement repair must have very high-early strength for opening to traffic as
soon, good anti-shrinkage and anti-cracking performance, interfacial bond between old and new concrete
surface besides the basic pavement performance. High fluidity is also needed for simplifying repairing
operation and for guaranteeing the repair quality. In a sense, high fluidity is conflict with super high-early
strength. In this paper, focusing on the early flexural strength, interfacial bond, shrinkage and cracking
performance, the preparing and testing of high-fluidity and super high-early strength concrete (HFESC) for
pavement repair was investigated. The repair concrete material, which prepared with Sulphoaluminate
cement, Amino-superplasticizer and RF admixture, has 3.5MPa 5h-flexural strength, 20MPa 5h-compressive
strength and 200mm slump value. The laboratory test and field pavement repairing results revealed that the
concrete has high fluidity and good mechanics performance and durability, which can be used in rapid repair
of concrete pavement.
1 INSTRUCTIONS
Cement concrete pavement (CCP in short) is
possessed of traffic safety, stability and durability
comparing with asphalt pavement. Besides which,
the comprehensive cost especially maintenance
expanse of CCP is lower than that of asphalt
pavement. While the rehabilitation of pavement
surface distress, once it occurs, must be conducted in
time for avoiding the serious pavement damage.
Along with the increasing of pavement service life,
driving speed, especially the road traffic volume and
axle load, more and more CCP was destroyed in
different degree in China (Li et al. 1998, Xie 2000).
The local damage is the main type of pavement
failure results form nature disaster and the
deficiencies involving pavement design, materials,
construction technology, management and quality
control. The further deterioration of local damage in
pavement will affect the ride comfort even destroy
vehicles which may result in traffic accidents. It is
very important to investigate feasible rapid repair
materials and methods for the use and development
of CCP. The rapid repair concrete for pavement
must have many performances including very highearly strength for opening to traffic with 3.5MPa
flexural strength and 20MPa compressive strength
(Wang & Li 2006), good anti-shrinkage and anticracking performance (Yang et al. 2000, Morgan.
1996), interfacial bond between old and new
concrete surface for long term repair effect besides
the basic properties (Morgan 1996). High fluidity is
also needed for simplifying repairing operation and
for guaranteeing the repair quality (Palacios et al.
2009, Yang et al. 2000). Considering the stress
characteristics of CCP and the actual specifications
of cement concrete pavement design, flexural
strength was used as control index and compressive
strength as reference one in experiment test.
In a sense, high fluidity is conflict with super
high-early strength (Chen et al. 2006). In this paper,
focusing on the early flexural strength, interfacial
bond, shrinkage and cracking performance, the
preparing and testing of concrete with high-fluidity
and super high-early strength for pavement repair
was investigated. Based on the all kinds of
experiments relevant with compatibility of cement
and addictives, strength, interfacial bond and freezethaw durability, HFESC was prepared and applied
for pavement damage repair. Many kinds of
materials, such as Sulphoaluminate cement,
magnesia-phosphate cement, early strength agent,
fiber and polymers etc (Chung 2004, Yang et al.
2000, Huang et al. 2004), can be used for concrete
pavement repairing. In this paper, the concrete
repairing material was prepared with
Sulphoaluminate cement, Amino-superplasticizer
(ASS in short) and RF admixture. The repair
J = − D ( h, Tpossessed
) ∇h
materials
of 3.5Mpa 5h-flexural strength,
(1)
20MPa 5h-compressive strength and 200mm slump
value
could meet demand
for D(h,T)
traffic recovery.
Theand
proportionality
coefficient
is called
The
laboratory
test
and
field
pavement
moisture permeability and it is a nonlinearrepairing
function
results
revealedhumidity
that theh concrete
has highT (Bažant
fluidity
of the relative
and temperature
and
good
mechanics
performance
and
durability,
& Najjar 1972). The moisture mass balance requires
which
be used
in of
rapid
repair mass
of concrete
that thecan
variation
in time
the water
per unit
pavement.
volume of concrete (water content w) be equal to the
divergence of the moisture flux J
2 ∂EXPERIMETN PROGRAM
(2)
− = ∇•J
∂
2.1 Basic materials
TheCement
water content w can be expressed as the sum
2.1.1
water, water
of
the
evaporable
we (capillary
Industrial blended water
Portland
cement, produced
by
vapor, andPortland
adsorbed
water)andandmixing
the non-evaporable
grinding
clinker
with up to 3
1966,
(chemically
water
wn (Mills
mass%
gypsumbound)
and about
6 mass%~15
mass%
of
Pantazopoulo
& Mills(type
1995).PO42.5
It is reasonable
the
mixing materials
according to
assume that the
evaporable
a function
of
GB175-1999)
in the
Tianjin water
cementisWorks
(PO in
relativewas
humidity,
degree
of hydration,
αc, and
short)
used inh, this
study.
Rapid hardening
degree of silica fume
reaction,
Sulphoaluminate
cement
(SA inαshort)
s, i.e. wwas
e=walso
e(h,αused
c,αs)
= experiment.
age-dependent
sorption/desorption
isotherm
in
The basic
performance indexes
of
(Norling
Mjonell
1997).
Under
this
assumption
and
cements were listed in Table 1.
by substituting Equation 1 into Equation 2 one
Table
1. Basic performance indexes of cements.
obtains
w
t
______________________________________________
Performance
SA
PO
∂w
∂w
∂w ∂h
______________________________________________
e
e
e
α& +
α&s + w1&n
+ ∇ • ( D ∇h ) =
−
(3)
Fineness
sieve
h residue),
∂α % c 1.5
∂α
∂h ∂(80µm
t
c
s
Volume stability
qualify qualify
Initial setting, min
40
220
Final
setting,
min
100
380
where ∂we/∂h is the slope of the sorption/desorption
Cement
strength,
MPa
isotherm
(also called moisture
capacity).
The
12h
flexural strength
6.4
- completed
governing
equation
(Equation
3)
must
be
12h compressive strength
39.7
byflexural
appropriate
1d
strengthboundary and initial
7.2 conditions.
The relation
between the amount
of- evaporable
1d compressive
strength
49.8
3d
flexural
water
andstrength
relative humidity 8.6
is called 5.1‘‘adsorption
3d
compressiveif strength
36.6 relativity
isotherm”
measured with-62.4
increasing
28d
flexural
strength
9.4
humidity
and ‘‘desorption
isotherm”
in54.8
the opposite
28d
compressive
strength
case. Neglecting their difference (Xi et al. 1994), in
_____________________________________________
the following, ‘‘sorption isotherm” will be used with
reference to both sorption and desorption conditions.
By theAggregates
way, if the hysteresis of the moisture
2.1.2
isotherm would
be taken
into account,
Crushed
limestone
aggregate
is usedtwoasdifferent
coarse
relation,
evaporable
water
vs
relative
humidity,
must
aggregate in concrete. Limestone is a natural stone
be
used
according
to
the
sign
of
the
variation
of
the
material composing of more than 97 mass% calcium
relativity
humidity.
The
shape
of
the
sorption
carbonate. The used coarse aggregate is continuous
isothermwith
for HPC
influenced
by many
grading
the issize
of 5~15mm.
Theparameters,
apparent
3
especially
those
that
influence
extent
and
rate
density of the coarse aggregate is 2470kg/m . of the
chemical
and, with
in turn,
determine
pore
The riverreactions
sand (quartz)
the fineness
modulus
3
structure
and
pore
size
distribution
(water-to-cement
of 2.5 and apparent density of 2610kg/m is used as
ratio,aggregate
cement inchemical
fine
the study.composition, SF content,
curing time and method, temperature, mix additives,
etc.). In
the literature various formulations can be
2.1.3
Water
found
to
the sorption
Tap waterdescribe
from municipal
pipe isotherm
network of
wasnormal
used
concrete
(Xi etofal.
1994). However, in the present
for
production
concrete.
paper the semi-empirical expression proposed by
Norling Mjornell (1997) is adopted because it
Proceedings of FraMCoS-7, May 23-28, 2010
explicitly
accounts for the evolution of hydration
2.2
Admixtures
reaction
and SF content. This sorption isotherm
2.2.1
Water reducing agent
reads
For insure the high fluidity of concrete, the
commercial water reducer agent of Amino⎡
superplasticizer was used
after being ⎤⎥selected
⎢
through
on the efficiency
) −
we (h α c comparative
α s ) = G (α c αexperiment
+
⎢
⎥
s
∞
(water
g α c −reducers.
α )h ⎥ The
and compatibility of different
⎢
c ⎦ water
e
⎣
(4)
experiment result of compatibility
between
∞ −section
reducer and binder will be⎡ given
in
⎤
(g α
α )h 3.1.
1
,
,
,
1
1
10
1
c
K (α c α s )⎢e
⎢
2.2.2 Early strength admixture
⎣
10
,
c −
1
1
⎥
⎥
⎦
1
Early strength admixture is the key to preparing
HFESC
pavement
repair
Considering
the
where the
first
term
(gelmaterial.
isotherm)
represents
the
requirement
that
HFESC
must
posses
both
high
physically
bound
(adsorbed)
water
and
the
second
fluidity
and super-high
early
strength,the numerous
term of
(capillary
isotherm)
represents
capillary
kinds
early
strength
admixtures
were
investigated
water.
This
expression
is
valid
only
for
low
content
by
comparative
test
on
the
early
strength.
The
result
of
of SF. The
coefficient
G1 represents the amount
showed
that
the
super
high-early
strength
of
water
per
unit
volume
held
in
the
gel
pores
at
100%
concrete
was impossible
be be
prepared
only(Norling
relying
relative
humidity,
and it tocan
expressed
on
some
one
early
strength
agent
without
weakening
Mjornell
1997)
as using Amino-superplasticizer as
the
fluidity
when
water reducer.c Fortunately
we have developed a
s
(
)
G
α
α
=
k
α
c
+
k
α
s
(5)
ternary
strength
admixture (named
c compound
s vg c early
vg
s
RF admixture) composing of active powdered
admixture
salts such as sulfate and
c and inorganic
ksvg are material
parameters.
the
where kwhich
vg andobviously
nitrite,
improved
the earlyFrom
strength
maximum
water per unit
that can
of
concreteamount
and alsoof guaranteed
the volume
high fluidity
of
fill
all
pores
(both
capillary
pores
and
gel
pores),
one
fresh concrete.
one obtains
canThe
calculate
K1 aseffect
improving
of RF on cement mortar and
concrete will be showed in section
3.2.
⎤
⎡
,
1
w
⎢
⎢1 −
1
⎢
⎣
α s + 0.22α s − G
− 0.188
c
Concrete mixture
s
⎛
10⎜
e
⎝
g α c∞ − α c ⎞⎟h ⎥
1
⎠
⎥
⎥
2.3
⎦ (6)
K (α c α s ) =
⎛
⎞
∞
Experiment investigation⎜ g αon −28
groups of concrete
⎟h
c α cmix
⎝
⎠ − proportion was
specimen with basic e different
carried out for further research
on sthe reasonable
g1 can
Theofmaterial
parametersfluidity
kcvg and
usage
RF admixture,
of kfresh
vg andconcrete,
be
calibrated
by
fitting
experimental
data
relevant
to
compressive strength and flexural strength based on
freeoptimizing
(evaporable)
water content
in concrete
the
experiments
and analysis
of the rawat
various ages
Luzio &preparation.
Cusatis 2009b).
materials
for(Di
concrete
Based on the
selected basic mix proportion form 28 groups, four
kinds
of concrete mixtures
were further investigated.
2.2 Temperature
Table
2 shows the evolution
mix proportions of concrete.
Note that, at early age, since the chemical reactions
Table
2. Composition
of concrete
mixturesand(kg/m
associated
with cement
hydration
SF 3).reaction
______________________________________________
are exothermic, the temperature field is not uniform
Mixture
PO SA systems
RF Water
ASS
for non-adiabatic
evenSand
if theGravel
environmental
______________________________________________
temperature
can be
PO
380 is- constant.
- 190 Heat656conduction
1090 42
described
in
concrete,
at
least
for
temperature
PO+RF 335 45 190
656 1090 37 not
SA
- 100°C
380 -(Bažant
190 &656Kaplan
1090 1996),
42 by
exceeding
SA+RF
335
45
190
656
1090
37
Fourier’s law, which reads
0
,
1
10
1
1
_____________________________________________
q
= − λ ∇T
(7)
where q is the heat flux, T is the absolute
temperature, and λ is the heat conductivity; in this
3 RESULTS AND DISCUSSION
3.1 Early strength of cement mortar using RF
The effect of RF admixture on early strength of
cement mortar was investigated by early flexural and
compressive strength based on the methodology
proposed in the GB/T 17671-1999: Method of
testing cements-Determination of strength. The
experiment results were showed in Figures 1-2.
8
7
6
5
4
3
2
1
0
a
P
M
/
h
t
g
n
e
r
t
S
l
a
r
u
x
e
l
PO
PO+RF
SA
SA+RF
F
10
24
Age /h
72
Figure 1. Early flexural strength of cement mortar using RF.
50
45
aP40
M
/ 35
thg30
ne
trS25
ev20
is
se15
rp10
m
o5
C
0
PO
PO+RF
SA
SA+RF
10
24
Age /h
72
Figure 2. Early compressive strength of cement mortar using
RF.
From the figures 1-2, we can see that the early
strength of cement mortar is obvious increased when
use RF admixture. The flexural strength using RF is
nearly 2-3 times of that without RF admixture, and
the compressive strength is nearly 3-5 times.
3.2 Compatibility between admixture and cement
The compatibility between binder (including cement
and RF admixture) and ASS was analyzed through
the time-dependent slump extension (Qin 2000).
Fluidity of cement paste was measured According to
GB 8077-2000: methods for testing uniformity of
concrete admixture.
J = − D ( h, T )∇h slump extension of
The results of time-dependent
cement paste without RF admixture were showed in
Figure 3, the results
cement paste coefficient
using RF D(h,T)
Theofproportionality
admixture were shown
in
Figure
4.
moisture permeability and it is a nonlinea
of the relative humidity h and temperature
& Najjar 1972). The moisture mass balanc
230
that the variation in time of the water mas
volume of concrete (water content w) be eq
220
divergence
of the moisture flux J
m
/m210
no
is
ne200
tx
e
p190
m
ul
S180
− ∂ = ∇•J
∂
w
t
The water content w can be expressed a
of
the evaporable
we (capillary wa
0.60%
0.80% water1.00%
vapor,
1.20% and adsorbed
1.40% water) and the non-e
(chemically
bound) water wn (Mil
170
Pantazopoulo & Mills 1995). It is reas
0
10 assume
20 that
30 the
40 evaporable
50 60 water
70 is a fu
T /min
relative humidity,
h, degree of hydration
, i.e. we=w
degree
of
silica
fume
reaction,
Figure 3. Slump extension of cement mortar
usingαsRF
= age-dependent sorption/desorption
admixture.
(Norling Mjonell 1997). Under this assum
by substituting Equation 1 into Equati
240
obtains
230
m220
m
/
no
is210
ne
tx
e200
p
m
ul 190
S
180
−
∂w ∂h
e + ∇ • ( D ∇h) = ∂we
h
∂α
∂h ∂t
∂w
α&c + e α&s + w
∂α
c
s
where ∂we/∂h is the slope of the sorption/
isotherm (also called moisture capac
governing equation (Equation 3) must be
by0.60%
appropriate0.80%
boundary and
initial conditi
1.00%
1.20%
1.40%
The relation between the amount of e
170
water and relative humidity is called ‘‘
0
10 isotherm”
20 30 if 40
50 60
measured
with 70increasing
/min‘‘desorption isotherm” in th
humidity Tand
case. Neglecting
(Xi et al.
Figure 4. Slump extension
of cement their
mortardifference
without RF
the following, ‘‘sorption isotherm” will be
admixture.
reference to both sorption and desorption c
By thegood
way,compatibility
if the hysteresis
Figures 3-4 shows
betweenof the
isotherm
be taken
account, two
ASS, RF admixture
andwould
cement.
The into
obvious
relation,byevaporable
water
relative humi
increasing of fluidity
using ASS
alsovs occurs
used according
the sign
of the varia
whether using RFbeadmixture
or not.to The
optimum
relativity
humidity.
The
shape
of the
dosage of ASS is 1.0 mass% of cement.
isotherm for HPC is influenced by many p
especially those that influence extent and
3.3 Early strength
of concrete
chemical
reactions and, in turn, determ
structure
and
size distribution
Early strengths of four kinds pore
of concrete
mixture (waterratio,
cement chemical
SF
(see Table 2) were
investigated
according composition,
to GB-T
curingfortime
method,
temperature, mix
50081-2002: Standard
testand
method
of mechanical
etc.). concrete.
In the literature
various
formulatio
properties on ordinary
The fluidity
of fresh
found
to
describe
the
sorption
isotherm
concrete was also measured according to GB-T
concrete
(Xi etforal. ordinary
1994). However,
50080-2002: Test
method
fresh in th
the semi-empirical
expression
concrete. And allpaper
the slumps
of them were
over pro
Norling
Mjornell
(1997)
is
adopted b
200mm.
Proceedings of FraMCoS-7, May 23-28, 2010
J
=The
− D (hresults
, T )∇h of early strength of concrete were
(1)
showed in Figures 5-6.
The
7.0 proportionality coefficient D(h,T) is called
moisture permeability and it is a nonlinear function
of the6.0relative humidity h and temperature T (Bažant
& Najjar
5.0 1972). The moisture mass balance requires
that the variation in time of the water mass per unit
4.0 of concrete (water content w) be equal to the
volume
divergence
of the moisture flux J
3.0
a
P
M
/
h
t
g
n
e
r
t
s
l
a
r
u
x
w
e
l
F
PO
PO+RF
SA
SA+RF
(2)
− ∂ 2.0
= ∇•J
∂
1.0
The
0.0 water content w can be expressed as the sum
of the evaporable
0
20water we40(capillary60water, water
80
vapor, and adsorbed water)Ageand/h the non-evaporable
(chemically
bound)
water
wn (Mills 1966,
Figure
5. Early flexural
strength
of concrete.
t
Pantazopoulo & Mills 1995). It is reasonable to
assume that the evaporable water is a function of
45 humidity, h, degree of hydration, αc, and
relative
degree
a 40 of silica fume reaction, αs, i.e. we=we(h,αc,αs)
= PMage-dependent
sorption/desorption isotherm
/ 35 Mjonell 1997). Under this assumption and
(Norling
ht 30
by gnesubstituting
Equation 1 into Equation 2 one
rt 25
obtains
s
ev 20
is
PO
se
∂
∂
∂w
w
w
rp 15
∂h
e α& + e α&PO+RF
&
+ ∇ • ( D ∇h ) =
− me
c
s + wn
h
∂α
∂α
∂oh10 ∂t
SA
c
s
C
(3)
5
SA+RF
0
where ∂we/∂h is the slope of the sorption/desorption
isotherm0 (also 20called moisture
capacity).
The
40
60
80
Age /h3) must be completed
governing equation (Equation
by appropriate
boundarystrength
and initial
conditions.
Figure
6. Early compressive
of concrete.
The relation between the amount of evaporable
waterIt and
relativetohumidity
is calledhigh
‘‘adsorption
is difficult
get super-early
strength
isotherm”
measured
with increasing
(with
in 10 ifhours)
using Ordinary
Portlandrelativity
Cement
humidity
and
‘‘desorption
isotherm”
in
the
opposite
even the RF admixture is added, the flexural
case. Neglecting
difference
et al.as1994),
in
strength
of it is nottheir
enough
to open(Xi
traffic
early as
the hours.
following,
‘‘sorption
isotherm”
will cement
be used such
with
10
While
using rapid
hardened
reference
desorption
conditions.
as
ASS, ittoisboth
easysorption
to open and
traffic
in 10 hours.
As to
By
the
way,
if
the
hysteresis
of
the
moisture
HFESC prepared with ASS and RF admixture, its 5isotherm
wouldstrength
be takenis into
different
hour
flexural
as account,
high as two
3.7MPa
and
relation,toevaporable
water vs relative humidity, must
enough
open traffic.
be used according to the sign of the variation of the
relativity humidity. The shape of the sorption
3.4
isotherm for HPC is influenced by many parameters,
those thatofinfluence
extentwasand used
rate of for
the
Sespecially
plitting strength
concrete
chemical reactions
and, inbond
turn,strength
determine
representing
the interfacial
basedpore
on
structure
and
pore
size
distribution
(water-to-cement
the methodology proposed in reference (Zhao et al.
ratio, cement
composition,
SF test
content,
1999).
Half ofchemical
the specimen
after split
was
curing time
and method,
mixHFESC
additives,
placed
in specimen
mouldtemperature,
and then cast
in
etc.). Inasthetheliterature
various
formulations
can for
be
mould
other half
of specimen
using
found to test.
describe
sorption isotherm
normal
splitting
Thethespecimen,
with theofsize
of
concrete (Xi et al. was
1994).placed
However,
present
150×150×150mm,
with inthetheold-new
paper theinterface
semi-empirical
by
concrete
vertical expression
after 28d’sproposed
curing for
NorlingFigure
Mjornell
(1997)
is adoptedresult.
because it
testing.
7 gives
the experimental
Interfacial bond strength
Proceedings of FraMCoS-7, May 23-28, 2010
explicitly accounts for the evolution of hydration
1.8 and SF content. This sorption isotherm
reaction
PO
reads1.6
PO+RF
1.4
SA
1.2
⎡
⎤
⎢
⎥
SA+RF
we (h1.0
α c α s ) = G (α c α s )⎢ −
+
⎥
∞
0.8
(g α
⎢
c − α c )h ⎥⎦ (4)
e
⎣
0.6
∞ − α )h ⎤
⎡
0.4
(g α
c
c − ⎥
⎢
K (α c α s ) e
0.2
⎢
⎥
⎣
⎦
0.0
10h
1d
3d
28d
90d
where the first term (gel isotherm)
represents the
Age
physically bound (adsorbed) water and the second
Figure
Interfacial bond
strengthrepresents
of concrete. the capillary
term 7.(capillary
isotherm)
water. This expression is valid only for low content
shows that Gthe
using of RF admixture
of Figure
SF. The7 coefficient
1 represents the amount of
increases
bond
strength
between
old
water per the
unitinterfacial
volume held
in the
gel pores
at 100%
concrete
and
new
repair
HFESC
especially
in
early
relative humidity, and it can be expressed (Norling
age.
The enhancement
of RF admixture on concrete
Mjornell
1997) as
early strength may result form the active effect of
early strengthccompound
s αins RF.
G (α c α s ) = k vg α c c + k vg
(5)
s
3.5
ksvg are of
material
parameters.
From for
the
wherefrost
kcvg and
The
resistance
concrete
is essential
maximumdurability,
amount ofespecially
water per in
unitthevolume
that can
concrete
area existing
fill
all
pores
(both
capillary
pores
and
gel
pores),
one
freeze-thaw circle. The freeze-thaw durability was
as
one
obtains
can
calculate
K
1
evaluated according to GB/T 50082 200×: Standard
for test method of long-term
performance⎤ and
⎛
⎞
∞
durability of ordinary concrete⎡⎢ (opinion
⎜ g α −α
c soliciting
c ⎟⎠h ⎥⎥
−
+
−G ⎢ −e ⎝
w
α
s
α
s
draft).
c
s
⎥
⎢
Figure
8
gives
the
freeze-thaw
circle experiment
⎦ (6)
⎣
K (α c α s ) =
⎛
⎞
∞
results.
⎜ g α − α ⎟h
a
P
M
/
1
h
t
g,
n
e
r
t
s
,
,
1
1
g
n
i
t
t
i
l
p
S
10
10
,
1
1
1
1
,
1
Freeze-thaw durability
10
0
0.188
0.22
1
1
1
,
1
10
3.0
e
⎝
1
c
c⎠
−1
PO
The
material
parameters
kcvg and ksvg and g1 can
2.5
SA
be calibrated by fitting experimental data relevant to
free 2.0
(evaporable)SA+AF
water content in concrete at
%
/
s
s
o
l
various ages (Di Luzio & Cusatis 2009b).
1.5
h
t
g
n
e
r
t
S
1.0
2.2 Temperature
evolution
Note0.5
that, at early age, since the chemical reactions
associated with cement hydration and SF reaction
0.0
are exothermic,
the temperature field is not uniform
for non-adiabatic
systems
even
environmental
0
50
100 if the150
200
temperature is constant.
Heat
can be
Freeze-thaw
circleconduction
times
described in concrete, at least for temperature not
Figure
8. Freeze-thaw
exceeding
100°C durability
(Bažantof concrete.
& Kaplan 1996), by
Fourier’s law, which reads
The experiment results reveal that Group SA
posses
the
q = − λ∇
T best frost resistance performance and the
strength loss of Group PO is the highest. All (7)
the
strength loss of concrete after 200 times freeze-thaw
where is qlower
is the
is the substitute
absolute
circle
than heat
30%. flux,
The 12T mass%
temperature,
and
λ
is
the
heat
conductivity;
in this
of cement with RF admixture lower the freeze-thaw
durability of concrete, which may result form the
resoluble salt in RF admixture.
4 CONCLUSIONS
Based on the experimental research on RF admixture,
water reducing agent, mechanical performance and
freeze-thaw durability of HFESC, we can draw some
conclusions as follows:
(1) Good compatibility between sulphate
aluminium cement, Amino-superplasticizer and RF
admixture makes the preparing of HFESC possible.
(2) The 5h flexural strength of HFESC is over
3.5MPa and 5h compressive strength over 2MPa.
HFESC, possessing both high fluidity and super
high-early strength, is qualified as an efficient rapid
pavement repair material. The application of HFESC
in actual pavement repair also verifies the high
performance of HFESC.
(3) The facts such as easy gain of materials for
and open to
preparing HFESC,
traffic as early as 5 hours make HFESC a suitable
pavement repair material. HFESC is worth
popularizing.
convenient construction
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1813.
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(wateroncontent
Zhao Z, Zhao G, Huang C of(1999).
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adhesivew) be eq
divergence
of
the
moisture
flux
J
splitting tensile behavior of young on old concrete.
Industrial Construction. 29 (11): 56-59, 50.
− ∂ = ∇•J
∂
w
t
The water content w can be expressed a
of the evaporable water we (capillary wa
vapor, and adsorbed water) and the non-e
(chemically bound) water wn (Mil
Pantazopoulo & Mills 1995). It is reas
assume that the evaporable water is a fu
relative humidity, h, degree of hydration
degree of silica fume reaction, αs, i.e. we=w
= age-dependent sorption/desorption
(Norling Mjonell 1997). Under this assum
by substituting Equation 1 into Equati
obtains
−
∂w ∂h
e + ∇ • ( D ∇h) = ∂we
h
∂α
∂h ∂t
∂w
α&c + e α&s + w
∂α
c
s
where ∂we/∂h is the slope of the sorption/
isotherm (also called moisture capac
governing equation (Equation 3) must be
by appropriate boundary and initial conditi
The relation between the amount of e
water and relative humidity is called ‘‘
isotherm” if measured with increasing
humidity and ‘‘desorption isotherm” in th
case. Neglecting their difference (Xi et al.
the following, ‘‘sorption isotherm” will be
reference to both sorption and desorption c
By the way, if the hysteresis of the
isotherm would be taken into account, two
relation, evaporable water vs relative humi
be used according to the sign of the varia
relativity humidity. The shape of the
isotherm for HPC is influenced by many p
especially those that influence extent and
chemical reactions and, in turn, determ
structure and pore size distribution (waterratio, cement chemical composition, SF
curing time and method, temperature, mix
etc.). In the literature various formulatio
found to describe the sorption isotherm
concrete (Xi et al. 1994). However, in th
paper the semi-empirical expression pro
Norling Mjornell (1997) is adopted b
Proceedings of FraMCoS-7, May 23-28, 2010