FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
& The Patent Rules, 2003
COMPLETE SPECIFICATION
1. TITLE OF THE INVENTION:
METHOD FOR OPTIMIZING STRENGTH DEVELOPMENT OF ULTRA-HIGH STRENGTH CONCRETE
2. APPLICANT:
Name: SAMSUNG C&T CORPORATION
Nationality: Republic of Korea
Address: (Seocho-dong) 14, Seocho-daero 74-gil, Seocho-gu,
Seoul 137-956, Republic of Korea.
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the
invention and the manner in which it is to be performed:
2
【DESCRIPTION】
【Technical Field】
The present invention relates to methods for optimizing
strength development of ultra-high strength concrete, and
more particularly, to methods for optimizing strength
development of ultra-high strength concrete that are capable
of optimizing the strength development of the ultra-high
strength concrete in the same mixture design with the same
mixing materials as each other.
【Background Art】
With the popularity of super high-rise buildings,
recently, much interest in ultra-high strength concrete has
been increased. Through the application of the ultra-high
strength concrete, the sections of elements like columns,
beams and so on can be reduced to decrease the frame costs,
and furthermore, a substantially large internal space is
ensured to provide efficient space utilization.
The ultra-high strength concrete means hardened
concrete from which the development of the compressive
strength of more than 120MPa is obtained. The ultra-high
strength concrete is made by adopting cement, silica fume,
blast furnace slag fine powder, fly ash, and gypsum as
binders and mixing the materials with a low water-binder
ratio. Recently, the mixture design of extremely high
strength concrete with the compressive strength of 200MPa has
been proposed.
On the other hand, since the ultra-high strength
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concrete has a low water-binder ratio, the mixing materials
are not mixed well, and thus, the concrete does not obtain
the compressive strength development as designed. Even
though the mixing is conducted to have a given designed
strength, it is hard to mix the mixing materials, which
causes the development of the strength lower than the given
designed strength thereof. In the same manner, also, the
200MPa ultra-high strength concrete with an extremely low
water-binder ratio has the development of the strength lower
than the given designed strength thereof.
【Disclosure】
【Technical Problem】
Accordingly, the present invention has been made in view
of the above-mentioned problems occurring in the prior art,
and it is an object of the present invention to provide
methods for optimizing strength development of ultra-high
strength concrete that are capable of improving the problems
in the strength development of the ultra-high strength
concrete with a low water-binder ratio in conventional
practices, thereby optimizing the strength development of the
ultra-high strength concrete in the same mixture design with
the same mixing materials as each other.
【Technical Solution】
To accomplish the above object, according to a first
aspect of the present invention, there is provided a method
for optimizing strength development of ultra-high strength
concrete with mixture design in which mixing materials
including water, cement, silica fume, blast furnace slag,
gypsum, sand, and gravels are mixed with compressive strength
of 120MPa or more and a low water-binder ratio of 20% and
less, the method characterized in that the mixture design of
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the ultra-high strength concrete is conducted with a slump
flow of 850±50mm.
To accomplish the above object, according to a second
aspect of the present invention, there is provided a method
for optimizing strength development of ultra-high strength
concrete with mixture design in which mixing materials
including water, cement, silica fume, blast furnace slag,
gypsum, sand, and gravels are mixed with compressive strength
of 120MPa or more and a low water-binder ratio of 20% and
less, the method characterized in that the mixture design of
the ultra-high strength concrete is conducted with an air
content between 1.0% and 2.0%.
To accomplish the above object, according to a third
aspect of the present invention, there is provided a method
for optimizing strength development of ultra-high strength
concrete with mixture design in which mixing materials
including water, cement, silica fume, blast furnace slag,
gypsum, sand, and gravels are mixed with compressive strength
of 120MPa or more and a low water-binder ratio of 20% and
less, the method characterized in that dry-mixing of the
gravels and the silica fume is conducted for 20 to 40 seconds
in the mixing process of the ultra-high strength concrete,
and mixing of the other mixing materials is conducted.
To accomplish the above object, according to a fourth
aspect of the present invention, there is provided a method
for optimizing strength development of ultra-high strength
concrete with mixture design in which mixing materials
including water, cement, silica fume, blast furnace slag,
gypsum, sand, and gravels are mixed with compressive strength
of 120MPa or more and a low water-binder ratio of 20% and
less, the method characterized in that final mixing of the
water is conducted for 150 to 200 seconds in the mixing
5
process of the ultra-high strength concrete, and after
conducting a stationing operation where the mixing operation
stops for 200 to 400 seconds, mixing is conducted for 150 to
200 seconds.
To accomplish the above object, according to a fifth
aspect of the present invention, there is provided a method
for optimizing strength development of ultra-high strength
concrete with mixture design in which mixing materials
including water, cement, silica fume, blast furnace slag,
gypsum, sand, and gravels are mixed with compressive strength
of 120MPa or more and a low water-binder ratio of 20% and
less, the method characterized in that self-compacting
casting of the ultra-high strength concrete is conducted.
To accomplish the above object, according to a sixth
aspect of the present invention, there is provided a method
for optimizing strength development of ultra-high strength
concrete with mixture design in which mixing materials
including water, cement, silica fume, blast furnace slag,
gypsum, sand, and gravels are mixed with compressive strength
of 120MPa or more and a low water-binder ratio of 20% and
less, the method characterized in that wet-curing is
conducted for 14 to 28 days after the casting of the ultrahigh
strength concrete and air dry-curing is then conducted.
【Advantageous Effect】
According to the present invention, there are provided
the methods for optimizing strength development of ultra-high
strength concrete having the following advantages.
First, the strength development of the ultra-high
strength concrete can be optimized in the same mixture design
with the same mixing materials as each other, through
appropriate methods, that is, the mixing method, the adding
order of the mixing materials, the casting method, and the
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curing method, which are simple and advantageously applicable
to the construction site.
Second, the strength development of the ultra-high
strength concrete can be optimized so that if an ultra-high
strength concrete building is constructed with the ultra-high
strength concrete according to the present invention, a high
degree of stability of the building can be expected through
the optimization of the strength development thereof.
【Description of Drawings】
FIG.1 is a graph showing the compressive strength
properties of ultra-high strength concrete in accordance with
slump flows.
FIG.2 is a graph showing the compressive strength
properties of the ultra-high strength concrete in accordance
with air contents.
【Best Mode for Invention】
The present invention proposes six methods for
optimizing strength development of ultra-high strength
concrete with mixture design in which mixing materials
including water, cement, silica fume, blast furnace slag,
gypsum, sand, and gravels are mixed with compressive strength
of 120MPa or more and a low water-binder ratio of 20% and
less.
In the following embodiment, it was checked that the
compressive strengths of the ultra-high strength concrete
according to the six methods were improved. Through the six
methods, therefore, it is understood that the strength
development of the ultra-high strength concrete can be
optimized, and further, if the six methods are applied at the
same time, the strength development thereof can be more
increased. Especially, the six methods are advantageously
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applicable in case of extremely high strength concrete of
more than 200MPa.
(1) Previous dry-mixing
Before mixing materials are mixed in a concrete mixer,
gravels and silica fume are first put and dry-mixed for 20 to
40 seconds, and the other mixing materials are then mixed to
the mixed materials. This allows the silica fume to be
evenly distributed and coated on the surfaces of the gravels
to increase the pozzolanic reaction of a transition zone (the
boundary surface between cement and gravels), thereby
improving the attachment capability between the gravels and
the cement paste. Through the dry-mixing results for 30
seconds according to the embodiment of the present invention,
it was found that the compressive strength of the ultra-high
strength concrete was increased.
(2) Stationing
When water is finally mixed after the other mixing
materials have been dry-mixed in the concrete mixer, the
mixing operation is conducted for 150 to 200 seconds, and
next, a stationing operation where the mixing operation stops
for 200 to 400 seconds is conducted. After that, the mixing
operation is conducted again for 150 to 200 seconds, and the
mixed materials are discharged from the concrete mixer. This
allows the initial hydration reaction to be accelerated and
improves the compacting capability of concrete. Through the
stationing operation according to the embodiment of the
present invention, it was found that the compressive strength
of the ultra-high strength concrete was increased.
(3) Slump flow control
The slump flow of the ultra-high strength concrete has a
close relation with the strength. That is, the higher the
slump flow is, the higher the compacting property of the
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ultra-high strength concrete is advantageously. Accordingly,
the slump flow of 850±50mm is provided in the embodiment of
the present invention. If the slump flow is less than
850±50mm, the compacting property is deteriorated to cause
the compressive strength to be lowered, and contrarily, if it
is over 850±50mm, the separation of the mixed materials may
occur. After checking the relation between the slump flow
and the strength in the mixing process of the ultra-high
strength concrete with a compressive strength of 200MPa in
the embodiment of the present invention, it was found that
the highest strength development occurred with the slump flow
of 850±50mm. On the other hand, the slump flow is
controllable by means of appropriate adjustment of amounts of
various chemical agents (water reducing agent, flowing agent
and so on) added, which give no influence on the mixture
design of the concrete.
(4) Air content control
The air content is controlled 2.0% and less. The air
content is inversely proportional to the strength, so that
the smaller the air content is, the higher the strength of
the ultra-high strength concrete is advantageously. After
checking the relation between the air content and the
strength in the mixing process of the ultra-high strength
concrete with a compressive strength of 200MPa in the
embodiment of the present invention, it was found that the
development of compressive strength was optimized in the air
content of 2.0% and less. On the other hand, the air content
is controllable by means of appropriate adjustment of amounts
of various chemical agents (foaming agent, antifoaming agent
and so on) added, which give no influence on the mixture
design of the concrete.
(5) Self-compacting casting
9
If the fluidity of concrete is good, self-compacting
casting is conducted. In case where vibration compacting is
performed by using a vibrator, material segregation or air
content increment occurs to cause the strength reduction. It
was in the embodiment of the present invention found that the
strength development in the self-compacting casting is better
than that in the vibration compacting casting. Especially,
if the slump flow of 850±50mm is provided, good fluidity is
made to allow the self-compacting casting to be conducted.
(6) Wet curing
After casting, the ultra-high strength concrete is wetcured
for 14 to 28 days and then air-dried. If the water
inside the ultra-high strength concrete is dried due to the
low water-binder ratio, an amount of water needed for
hydration reaction may be insufficient. Therefore, there is
a need for preventing the water inside the concrete from
being evaporated at the time when the hydration reaction
occurs actively, and in the embodiment of the present
invention, the ultra-high strength concrete is wet-cured for
14 to 28 days after casting. If the wet curing is kept
longer than the proposed period of the present invention,
however, the strength may be decreased, and accordingly, the
wet curing for 14 to 28 days is most preferable.
【Mode for Invention】
Hereinafter, the strength properties of the ultra-high
strength concrete according to the methods of the present
invention will be explained. In this case, however, the
embodiment as will be described below just explains the
present invention, and the scope of the invention is not
defined thereby.
[Embodiment] Strength properties of ultra-high strength
concrete according to the methods of the invention
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1. Experiment method
The influences on the compressive strength by
experimental variable were checked with the same mixing ratio
of 200MPa ultra-high strength concrete in the following Table
1. The experiments were performed in the state where the
other conditions except the respective experimental variables
were the same as each other.
Table 1
Ultra-high strength concrete mixing
W/B S/a Unit Weight (kg/m3)
W/B S/a W OPC Silica
Fume
Blast
Furnace
Slag
Gypsum Sand Gravel
12.5% 35% 150 660 240 240 60 392 736
2. Experiment result
(1) Strength properties of ultra-high strength concrete
in accordance with mixing condition
The strength properties of ultra-high strength concrete
in accordance with mixing condition were obtained as listed
in Table 2. As listed, it was found that the compressive
strength of the ultra-high strength concrete was improved if
the gravels and the silica fume were first dry-mixed.
Table 2
Strength properties of ultra-high strength concrete in
accordance with mixing condition
Division Compressive strength(MPa)
구분 7 days of
age
28 days of
age
91 days of
age
General dry-mixing 150.4 184.5 198.7
First dry-mixing of
gravels and silica
fume for 30 seconds
155.8 194.4 207.1
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(2) Strength properties of ultra-high strength concrete
in accordance with the existence of stationing
The strength properties of ultra-high strength concrete
in accordance with the existence of the stationing operation
in the mixing of water were obtained as listed in Table 3.
As listed, it was found that the compressive strength of the
ultra-high strength concrete was improved if the stationing
operation was conducted.
Table 3
Strength properties of ultra-high strength concrete in
accordance with the existence of stationing
Division Compressive strength(MPa)
구분 7 days of
age
28 days of
age
91 days of
age
No stationing 144.1 170.3 191.6
Mixing for 180
seconds and after
stationing for 300
seconds, mixing for
180 seconds
147.3 174.9 197.1
(3) Strength properties of ultra-high strength concrete
in accordance with slump flow
The estimation results of the ultra-high strength
concrete in accordance with the variations of the slump flows
were shown in FIG.1. As shown, it was found that the
compressive strength of more than 200MPa was obtained at the
slump flows between 800mm and 900mm and the compressive
strengths of less than 200MPa at the slump flows of less than
800mm.
(4) Strength properties of ultra-high strength concrete
in accordance with air content
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The estimation results of the ultra-high strength
concrete in accordance with the variations of the air content
were shown in FIG.1. As shown, it was found that the
compressive strength was drastically decreased as the air
content exceeded 2%.
(5) Strength properties of ultra-high strength concrete
in accordance with casting method
The strength properties of the ultra-high strength
concrete in accordance with the casting method were obtained
as listed in Table 4. As listed, it was found that the
compressive strength of the ultra-high strength concrete was
more improved at the self-compacting casting when compared
with the vibration compacting casting.
Table 4
Strength properties of ultra-high strength concrete in
accordance with casting method
Division Compressive strength(MPa)
구 분 7days of
age
28days of
age
91days of
age
Vibration
compacting
150.8 178.0 192.5
Selfcompacting
153.2 187.2 201.7
(6) Strength properties of ultra-high strength concrete
in accordance with curing method
The strength properties of the ultra-high strength
concrete in accordance with the curing method were obtained
as listed in Table 5. As listed, it was found that the
compressive strength of the ultra-high strength concrete was
remarkably improved when the water curing was conducted for
14 days.
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Table 5
Strength properties of ultra-high strength concrete in
accordance with curing method
Water curing period Compressive strength (MPa)
of 91 days of age
Air dried 179.6
Water curing for 3 days 191.4
Water curing for 7 days 202.5
Water curing for 14 days 212.0
Water curing for 28 days 211.9
Water curing for 91 days 189.2
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We claim:
【Claim 1】
A method for optimizing strength development of ultrahigh
strength concrete with mixture design in which mixing
materials including water, cement, silica fume, blast furnace
slag, gypsum, sand, and gravels are mixed with compressive
strength of 120MPa or more and a low water-binder ratio of
20% and less, the method characterized in that dry-mixing of
the gravels and the silica fume is first conducted for 20 to
40 seconds and the other mixing materials are put and mixed.
【Claim 2】
A method for optimizing strength development of ultrahigh
strength concrete with mixture design in which mixing
materials including water, cement, silica fume, blast furnace
slag, gypsum, sand, and gravels are mixed with compressive
strength of 120MPa or more and a low water-binder ratio of
20% and less, the method characterized in that the water is
finally put and mixed for 150 to 200 seconds, and after a
stationing operation where the mixing operation stops for 200
to 400 seconds is conducted, the mixing operation is
conducted for 150 to 200 seconds.
【Claim 3】
A method for optimizing strength development of ultrahigh
strength concrete with mixture design in which mixing
materials including water, cement, silica fume, blast furnace
slag, gypsum, sand, and gravels are mixed with compressive
strength of 120MPa or more and a low water-binder ratio of
20% and less, the method characterized in that the mixture
design of the ultra-high strength concrete is conducted with
a slump flow of 850±50mm.
15
【Claim 4】
A method for optimizing strength development of ultrahigh
strength concrete with mixture design in which mixing
materials including water, cement, silica fume, blast furnace
slag, gypsum, sand, and gravels are mixed with compressive
strength of 120MPa or more and a low water-binder ratio of
20% and less, the method characterized in that the mixture
design of the ultra-high strength concrete is conducted with
an air content between 1.0% and 2.0%.
【Claim 5】
A method for optimizing strength development of ultrahigh
strength concrete with mixture design in which mixing
materials including water, cement, silica fume, blast furnace
slag, gypsum, sand, and gravels are mixed with compressive
strength of 120MPa or more and a low water-binder ratio of
20% and less, the method characterized in that selfcompacting
casting of the ultra-high strength concrete is
conducted.
【Claim 6】
A method for optimizing strength development of ultrahigh
strength concrete with mixture design in which mixing
materials including water, cement, silica fume, blast furnace
slag, gypsum, sand, and gravels are mixed with compressive
strength of 120MPa or more and a low water-binder ratio of
20% and less, the method characterized in that after the
casting of the ultra-high strength concrete, wet curing of
the ultra-high strength concrete is conducted for 14 to 28
days and air dry curing is then conducted.
16
【Claim 7】
A method for optimizing strength development of ultrahigh
strength concrete with mixture design in which mixing
materials including water, cement, silica fume, blast furnace
slag, gypsum, sand, and gravels are mixed with compressive
strength of 120MPa or more and a low water-binder ratio of
20% and less, the method characterized in that two or more
steps are selected from the following steps of:
conducting the mixture design of the ultra-high strength
concrete with a slump flow of 850±50mm;
conducting the mixture design of the ultra-high strength
concrete with an air content between 1.0% and 2.0%;
conducting first dry-mixing of the gravels and the
silica fume for 20 to 40 seconds and conducting the putting
and mixing of the other mixing materials in the mixing
process of the ultra-high strength concrete;
conducting final mixing of the water for 150 to 200
seconds and after conducting a stationing operation where the
mixing operation stops for 200 to 400 seconds, conducting the
mixing for 150 to 200 seconds in the mixing process of the
ultra-high strength concrete;
conducting self-compacting casting of the ultra-high
strength concrete; and
conducting wet curing for 14 to 28 days after the
casting of the ultra-high strength concrete and conducting
air dry curing.
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【Claim 8】
The method for optimizing strength development of ultrahigh
strength concrete according to any one of claims 1 to 7,
wherein the mixture design of the ultra-high strength
concrete has the compressive strength of more than 200MPa.