Note: Descriptions are shown in the official language in which they were submitted.
7~7
-- 1
ADMIXTUR FOR COLD~WEATHER CONCRET~
_echnical Field
This invention is concerned with an admixture for cold-weather
concrete, which admixture possesses the superior characteristic that
early strength gain of concrete dt lOW t~nperatures is substantially
increased without adverse effects on the basic performance of con-
crete.
In cold-weather concreting, where concrete is placed in cold
weather when outside air temperature is at 0C or under, it is pre-
scribed for curing to be provided by heating or insulating in order
tha-t the concrete placed will not be subjected to frost damage during
the initial curing period until the concrete placed attains a compres-
sive strength (generally said to be 30 to 50 kg/cm2) suf-Ficient to
secure resistance against frost damage. However, it is not an easy
matter from the standpoint of work loads and facilities to provide
curing by insulation or heating at the jobsite where concrete has
been placed.
Meanwhile, it has been proposed that the above-mentioned curing
by insulation or heating during the initial curing period be elimina~ed
2n or reduced through the use of an admixture with a marked effect in
producing early strength gain of concrete at low temperature. Such
an admixture is called an antifreezing admixture and calcium chloride
is representative of the type. However, the anti-freezing admixtures
presently available are such that at the levels of addition at which
~5 effects as antifreezing admixtures can be demonstrated the additions
have various undesirable effects on concrete. One is that the basic
performance of concrete is greatly lowered. There are also antifreez-
ing admixtures which cause abnormal setting of concrete rapidly
impairing consistency after mixing to markedly lower workabilityO
By basic performance of concrete it is meant here the performance
which will be the basis for performance evaluation ancl design of
concrete which should be inherent to concrete. In tangible terms jt
3 ~7~
is the performance represented by eornpressive strength at 2~ da~s of
standard curing. Further, the effects of antifree~ing admixtures dS
antifree~ing admixtures are under question and ~here are few cases
of actual use~
Since such an antifree7ing admixture greatly lowers the basic
performances of concrete, there are countries (for example, Japan~
which prohibit large-scale use of antiFreezing admixtures.
As mentioned above, there are various problems about placing
cold-weather concrete, and except for special projects~ it is normal
at present for concrete placement work to be discontinued in the
cold season. This constitutes an obstruction to year-round construc-
tion which has been the long-cherished desire of the construction
industry, and poses great problems with regard to the economics and
construction per10d of the entire project.
Disclosure of the Invention
.
This invention has the effect of prominently improving initial
strength of concrete at low temperature without harming basic per-
formance, and comprises an admixture for cold-weather concrete which
does not induce abnormal setting even when added in large quantity,
which has been perfected upon numerous studies with the purposes of
dissolving the various problems of cold-weather concrete and facili-
tating year-round performance of concreting work, and which i~ is
possible to use at temperatures as low as -10C to -15C.
The admixture for cold-weather concrete of the present inven-
tion is of the following composition:
(i) One part by weight of a single compound or a mixture of
two or more compounds selected from a group consisting of
water-soluble salts of sulfonated melamine formalin conden-
sates (hereinafter abbreviated as SMF) and water-soluble
salts oF aromatic hydrocarbon sulfonate -formalin condensates
(hereinafter abbreviated as ARF), (hereinafter Component
No. 1), and
(ii) One to twenty parts by weight of a single compound or a
mixture of two or more compounds selected rrom a group
¢b!~
consisting of nitrates, nitrites (both water-soluble
salts) and urea (Component No. 2).
A water soluble salt of a sulfonated melamine formalin con-
densate (SMF) mentioned above is a compound of a structure where
melamine, of which amino group is partially sulfomethylated, is
condensed with formalin, and is a water-soluble powder of molecular
weight of approximately lO00 to 5000. This compound is described in
Australian Patent No. 263607~
As for water-soluble salts of aromatic hydrocarbon sulfonate
formalin condensates (ARF), they are the water-soluhle salts of
formalin condensates of sulfonated polycyclic aromatic hydrocarbon
such as naphthalene and anthracene, and these aromatic hydrocarbons
may be compounds with alkyl groups substituted, or an industrial
product which is a mixture of various aromatic hydrocarbons (for
1~ example, creosote oil).
These SMF and ARF are known as water-reducing admixtures for
concrete, while materials comprising the second component of this
invention are known as antifreezing admixtures For concrete. SMF
and ARF have the effects of reducing unit water contents required to
produce prescribed concrete slumps 7 and concretes to which these are
added will have their strengths increased in accordance with reductions
in un1t water contents, However, the water-reducing effects of SMF
and ARF tend to be reduced at low temperatures, and with the addition
of only a SMF or A~F, there is no noticeable eFfect of increased
early strength. The effect of addition of only the second component
of this invention is that of greatly impairing the basic performance
of concrete similarly to conventional antifreezing admixtures, and
the early strength-increasing effect is not necessarily great.
However, when Component No. l and Component No. 2 are added together,
synergistic effects which were wholly unexpected are seen in -that the
early strength gain effect at low temperature is markedly improved,
while the basic performance of the concrete is completely unimpaired.
Such a synergistic effect is especially prorninent when the ratio
between Component No. 1 and Component No. 2 is in the range of 1:1-20
(desirably, 1:3-lO). It is noted that there are many concrete water-
reducing admixtures other than SMF and ARF which are known. Examples
;
; . .
~ ~ ~ 7 ~ ~ ~
are lignosulfonates and hydroxy carboxylates. However, even though
such concrete water-reducing admixtures and Component No. 2 are used
togetherg such a prominent synergistic effect as seen with this in-
vention cannot be recognized.
The addition quantity of the admixture for cold~weather concr te
of this invention is suitable in the range of approximately l to lO~
as expressed in terms of percentages by weight based on c ment (dosage),
and the early strength gain effect is greater the higher the dosage.
Dosages considered as suitable will differ depending on the environ~
mental temperature of concrete placed, but to indicate general measures,
they are approximately l% at around 0 to -2C, approximately 2 to 3%
at around -5C, and approximately 7 to lO~O at around l5GC. In
general, when dosage is high it is desirable for a composition wi-th
a high ratio of Component No~ 2 to be selected. Further, it is
desirable for dosage and composition to be adjusted so that the
dosage of Component No. l will be not less than 0.2700
The admixture for cold-weather concrete of this invention is
added to concrete by introducing into the mixer when mixing concrete.
Introduction into the mixer may be accomplished in various forms: in
20 unmodified powder form, as an aqueous solution, or dissolved in
mixing water. Also, Component ~o. l and Component No. 2 may be
charged separately into the mixer.
With concrete to which the admixture for cold-weather concrete of
this invention has been added it will suffice to perform simple curing
25 to the extent of keeping it covered with a tarpaulin after concrete
placement, and it is unnecessary for special curing such as with
ordinary cold-weather concrete. During this curiny period there
; will be no adverse effects on the physical properties and strength
gain of concrete after freezing even if freezing of concrete occurs
30 during this curing period~
Through the use of the admixture for cold-weather concrete of
this inven~ion, it will become possible to perform cold-weather
concreting at temperatures as low as -10C (-lSC in cases) without
curing by thermal insulation or by heating. Cold weather concreting
35 has been made easy by this and it has become possible for concrete
placement to be performed throughout the year, something which had
been lony-sought by the construction industry.
Examples of irnplementation of this invention are shown belo~ but
this invention is not limited in any way to these examples.
Example 1
The effects in cases of using Component No 1 and Component No~ 2
individually are shown in this example, along with the effects of
conventional antifreezing admixtures.
~1) Concrete Materials Used
Cement: Onoda* Type 1 portland cem~nt
Fine Aggregate. Kinu River sand, specific ~ravity = 2.6~,
FM - 2.78
Coarse Aggregate: crushed sandstone, MS = 20 mm
(2) Admixtures
SMF- Melment concrete water-reducing admix-ture manufactured
by Showa Denko Co., Ltd.
Sodium salt of formalin condensate of naphthalene sulfonate
~abbreviated NSF): Kao Soap Co., Ltd.J concrete water-
reducing admixture, Mighty
Calcium chloride, ethylene glycol~ urea, sodium nitrate, sodium
ritrite- reagent extra pure
(3) Mix Proportions of Concrete
Water-cement ratio of 0.50 and sand-aggregate ratio of sla = 43
were maintained constant and the mix propor-tions were
determined for target values of slump oF 1~ cm and air
content of 4.5 plus or minus 0.5%.
(4) Mixing, Curing and Testing of Concrete
Mixing of concrete was performed in a room of approxi~ately 5C
usir,g a 4-cubic foot tilting mixer. Concrete was cast in molds
for cylinder specimens of 10-centimeter diameter by 20-centimeter
height and cured for the specified length of time at the speci-
fied curing temperature while kept in the molds (~rapped in ~inyl
bags~. Specimens finished curing were left standing in a room
of 20C for approximately 3 hours for tha~ling before per-formin~
compressive strength tests. Curing tempera-tures were of the
three levels of 20C, -5C and -10C.
(5) The test results are shown in Table 1.
* tr~de mark
.'
i;
--6--
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a .~ J r L~
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_ _ _ __ _ _ _ _ ._ _ _ _ _. _ _ ~_ _ _ _ _ _
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a~ _____ J
O ~ O o U C O o ~ o ~ o
; _~ . - ~ _ . r-- r~ r-- r-- . r~
O _ ___ _____________
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O 3 ~ . . - _ _ r~ .
O _____ ______________
_ CO CO ~ CO CO t:O CO X CO C O 9
X ~ ~ U~ ~ ~ ~O ~,,~ ~ ~O ~O ~ ~ ~ ~
___ ___~ ------------_______
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~__ _____ .------------_
.
'
--7-
As is clearly shown by the above table, the addition of a con
ventional antifreezing admixture (calcium chloride, ethylene giycol)
greatly impairs -the basic performance of concrete. (Comparison of
strength for 20C, 28 days with the value for the mix proportion not
using an admixture.) The same may be said for Component No. 2 of this
invention. Further, conventional antifreezing admixtures cause abnor-
mal setting to pose a serious problem in using -them. Component No. l
of this invention used alone has practically no early strength gain
effect at low temperature.
Best Mode for Carrying Out Invention
Example 2
This example shows the effect of admixtures for cold-weather
concrete of this invention consisting of mixtures of Component No. l
and Component No. 2.
lS The materials and testing methods used in testing were all
identical to those in Example l.
The proportions by weight of the components of the admixtures,
and the identification symbols of the admixtures are given in Table 2
and the test results in Table 3.
Table 2
Formulation1
I ~ ~ A 1 B 1 C 1 D 1 E 1 F
1Component ~
I_ \l I I L L~l
Sodium nitrate 1 9 1 1 1 1_4.5 _
_ od m nitrlte 1 1 9 L 8 1 1 4.5 1 9
Urea 1 ~ 9
SMF _ 1 1 1 l 1 2
NSF
u~ CO ~
o ~ ~ c~ ~ ~ c~ c~ c`J o ~
o _ _ ~ c:t ~ ~ ~ ~ ~ ~ ~ 'il cl
NE C~l >~ CO C~
~ 'lS I_ ~O ~ ~ CO O ~ ~D i~ ~ (:0
-- r-- C~ N C~J C~l ~1 ~'7 C~J C~J ~J C~l C~l
~ _ _ _ _ __ ~_ _ _ _ _ _ __ _ _ _
~ r~ ~D ~ ~ r~ C ~ ~ U~
~ ~ ,__ ~ , , ~ ~ ~ ~ ~ ,_ ~
C~
O ____ ~ O
~ ~ U~ O ~ ~ l-- ~- Ln ~ ~ O
"_ _ _ ~ _ _ _ _ _ _ _ _ _ _ _ _
~ ~ a~ l ~ O ~ CO
c~ ~ o r~ ,-- C~ ~ ~ ~ O O~ O ~O
~.) L~ _C`'_ _______.____
~ r~
~ ~ 7 ~ o o ~_
_ ._ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _
~ s_ _ ~n a:~ ~ o c~7 o o c~l Ln ~,
C _ _ _ _ _ ~ ~ ~ Ln ~t ~ Ln ~ ~ ~ ~
~ t ~ Ln o o o Ln o c Ln Ln o o
t ~ ~ O et L~ L~ d' d- L L~7 ~ L~ Lt Lt
r~_ ''o __ ~ __ ___________
I_ O E
._ U7 a7 ~7 a7 0 ~n ~) ~7 CO ~t N
~3 ~n 1-- t.7 1-- ~L7 1-- Ln ~ LD r-- ~
~__ _ ~ _ ~
CO ~
N LL7 ~1 LD O N LD N LD CO e:l'
O CJ~ L t 7 Ln '7 e~ ._ t~ Ln ~7 ~ N
___ _______ _______ ___
~ ,_ Lt7 0 L17 0 Ln C.7 0 Ln O Ln 0
L ~s5! N Ln C~l Ln N Ln Ln N L~7 N Ln
CO
~ O
. .~
c~ cr cr t~ C~ L~ LIJ L' LL
O
' __ L' ________.___
~J
Ln D r7 ~ n LD l X ~) O r N ~7
- ¦ Z '-- r~ ; r-- c~ N N N N
___ _______
~7S~
As is clearly seen in Table 3, the admixture for cold-weather
concrete of this invention has an early strength gain effect at low
temperature which is markedly greater than for the case of Component
No. 2 above, while moreover, the basic performance of oncrete is
not merely unimpaired, but rather, a remarkable effect of improvement
is indicated.
Example 3
This example is of tests varying the mix proportions of concrete
and the composition of the admixture.
(1) Mix Proportions and Materials of Concrete
Table 4
I W/C I s/a I C I W I S ¦ G ¦ Admx.
¦ (%) ¦ (%) ¦ (kg/m3) ¦ (kg/m3) ¦ (kg/m3) ¦ (kg/m3) ¦ Dosage ¦
I_ I . 1 . 1 . I . _1 1 _ I
1 47.1l 47 1 350 1 165 1 837 1 955 1 5~O
Except for fine aggregate consisting of sand from the Oi River
the materials used for concrete were all identical to those used in
the tests of Example 1.
(2) The admixture compositions were those given in Table 5.
Table 5
20 1 \ Formulation¦
\ ¦ G ¦ H ¦ I ¦ J ¦ K
IComponent ~ l l l l l l
1,. 1 . I _ I l . . I l
¦ Sodium nitrate _ I j 4 ¦ 2.4 ¦ 8
I Sodium nitrite 1 8 1 4 1 5-6 L .l 6
25 1 Urea I l l l I.
__
¦ SMF L 2 ¦ 2 ¦ 2 ¦ 2 _ ¦
¦ NSF l_ l _ l I . ¦ 1
i7~
The test results are shown in Table 6.
Table 6
Admixture 1 1¦Compressive Strength (kg/cm2)
lOO 1 20G
_ L _ l
1 Test 1 ¦Dosage¦Slump¦ Air
¦Number¦ Formulation 1 (%) ¦(cm) 1 (~O) 17 days128 days17 days¦28 days
~ I L L ~1_ L
24 1 G 1 5 1l6.0 ~ 3.7 1 78.6 1 l54 1 388 1 480
1 H 1 5 ¦l8.0 1 3.7 1 l20 1 222 1 375 1 47526 1 I 1 5 1l6.5 1 3.~ 1 llO 1 222 1 378 1 480
27 1 J 1 5 1l7.o 1 3.8 1 74.4 1 l4~ 1 389 1 ~9l
28 1 K 1 5 1l8.5 L4-Z I 76.3 1 l5l 1 394 _1 492
It may be seen in this example, sirnilarly to the case of Example 2,
that the admixture for cold-weather concrete of this invention pro-
duces excellent effects,
Industrial Applicability
This invention may be utilized wherever it is desired to prepare
concrete in cold temperatures.
