CA1187907A - Admixture for cold-weather concrete - Google Patents

Abstract

ADMIXTURE FOR COLD-WEATHER CONCRETE

Abstract of the Disclosure A hydraulic cement mix including hydraulic cement, aggregate, suf-ficient water to effect hydraulic setting of the cement, and an admix-ture comprising 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 condensates and water-soluble salts of aromatic hydrocarbon sulfonate formalin condensates, and one to twenty parts by weight of a single compound or a mixture of two or more compounds selected from a group consisting of nitrates, nitrites (both water-soluble salts) and urea said admixture being present in an amount of up to 10% by weight based upon the weight of the cement to thereby promote the cure of said hydraulic cement mix with no adverse effect on the physical properties and strength gain of the hydraulic cement mix.

Description

7~7 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;

_ ._ _ _ _ _ _ _ ~ N In ~ ~ ~ ~ ~l N a~
~ a~ ~ ~ r~ ~ O ~:S) O
ON ~) N ~ ~ t~C~l C~ Cl- ~ d-~I O ___ ____ ___ ____ a .~ J r L~
.:J ~ IC~ r~ O N ~N ~ ~ N N ~ N N
_Y __ _ _ _________ ___ >~ ~ ~ ~ . r~ 1~ 00 ~ O d- ~~
~~ -rJ O ~J ,~ O N ~) O N __ _ _ _ _ _ _ _ ._ _ _ .r, . ~ 0 ~1 , N ~ o ~ o ~
~ -- --- ~
O --a O N a~ ~ cs ~ N ~ r~ 00 CJ'~ N
O O Ct) ~-- r~ r~ r- ~
1~ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ >, O ~ O CO O 1~ ~C~ ~ ~ d ~ ~O
~J ~ N N ~ 1~ ~ ~ N
_ _ _ __ _ _ _ _ ._ _ _ _ _. _ _ ~_ _ _ _ _ _ r- tlJ ~ ~ C~ O O Irl O ~ ;~ O N ~ O
, a~
a~ _____ J
O ~ O o U C O o ~ o ~ o ; _~ . - ~ _ . r-- r~ r-- r-- . r~
O _ ___ _____________ ._ ~ ~ J G e:;- ~ ~t d' ~n N U~
O 3 ~ . . - _ _ r~ .
O _____ ______________ _ CO CO ~ CO CO t:O CO X CO C O 9 X ~ ~ U~ ~ ~ ~O ~,,~ ~ ~O ~O ~ ~ ~ ~
___ ___~ ------------_______ ~J) ?~ O O O151 O 1~) 0 N IU') ~1 U~
~ _ _ _ _ _ O ~ N Lt~ O O Cl O

c r O ~) CJ aJ
c~
~r- IIJ O ~~ r-E~ . s 1:7- v~) ~1 ~5 ~ r-- r r-Cl,1~
~1 . ~-1!) ~ ~ ~:1 ~ ~ 11_ L- 11_ r-- ~ O O O O S~ S V~ ~
_ _ _ _ _ _ _ _ _ _ _ _ _ __ ._ _ _ _ _ _ _ 1-- ~ ~ r~, ~__ _____ .------------_ .
' 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.

Claims (3)

What is claimed is:

1. A hydraulic cement mix including hydraulic cement, aggregate, suf-ficient water to effect hydraulic setting of the cement, and an admix-ture comprising:
(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 and water-soluble salts of aromatic hydrocarbon sulfonate formalin condensates, and (ii) one to twenty parts by weight of a single compound or a mixture of two or more compounds selected from a group consisting of nitrates, nitrites (both water-soluble salts) and urea, said admixture being present in an amount of up to 10% by weight based upon the weight of the cement to thereby promote the cure of said hydraulic cement mix with no adverse effect on the physical properties and strength gain of the hydraulic cement mix.

2. A hydraulic cement mix according to claim 1 wherein the admixture is present in an amount of between 1 and 10% by weight based upon the weight of the cement.

3. A hydraulic cement mix in accordance with claim 1 wherein the dosage of Component No. (i) is not less than 0.2% by weight based upon the weight of the cement.