Prevention of slump loss in fresh concrete

Slump loss in fresh concrete is prevented by adding a powdery or granular barium, magnesium, iron or aluminum salt of a .beta.-naphthalenesulfonic acid-formaldehyde condensate to the cement or concrete composition. About 0.01 to 10 parts by weight of the condensate per 100 parts by weight of cement, preferably Portland cement, are employed.

The present invention relates to concrete or cement compositions. More 
particularly, the present invention relates to preventing slump loss in 
fresh concrete by employing a powdery or granular Ba, Mg, Fe or Al salt of 
.beta.-naphthalenesulfonic acid-formaldehyde condensate (hereinafter 
referred to as .beta.-NSF) as an additive therein. 
The greater part of concrete used in Japan, as well as in many places 
throughout the world, comprises ready-mixed concrete. Non-hardened fresh 
concrete is usually prepared in a plant by mixing and is then carried to 
the job or work site by means of an agitating truck. After preparation, 
the viscosity and hardness of the fresh concrete increase with time 
because of the hydration reaction of cement with water, thereby reducing 
the fluidity thereof and thus degrading the workability of the concrete. 
This phenomenon is generally called the "slump loss" of concrete. Concrete 
having a seriously reduced workability is unusable, since the deposition 
thereof is very difficult. 
According to the specification of Japanese Industrial Standard A 1101, the 
longest carrying time of fresh concrete is limited to 90 minutes in 
consideration of the slump loss thereof. The phenomenon of slump loss is 
particularly notable with rick-mix concretes and hot-weather concretes. 
In order to eliminate the slump loss, processes have been proposed in the 
prior art wherein a cement dispersing agent is added in small portions, or 
is added thereafter (Japanese Patent Publications Nos. 15856/1976 and 
5691/1978). However, the slump loss cannot be prevented completely even by 
such processes. According to these procedures, the slump is temporarily 
increased by the addition of a dispersing agent but, thereafter, the slump 
diminishes with time. Therefore, in order to completely prevent such slump 
loss, it is required that the dispersing agent be added continuously. 
Thus, in fact, it is quite difficult to control the slump within a certain 
range. 
After intensive investigations, the present inventors have found an 
additive which is capable of overcoming the defects of the prior art. This 
finding constitutes the basis of the present invention. 
Accordingly, one of the objects of this invention is to provide a concrete 
admixture containing an additive which is capable of preventing slump loss 
in fresh concrete. 
Another object of the invention is to prevent slump loss effectively and 
efficiently in concrete, cement or like admixtures, for example, with 
aggregate. 
These and other objects and advantages of the invention will become 
apparent to those skilled in the art from a consideration of the following 
specification and claims. 
In accordance with the present invention, it has been found that powdery or 
granular barium, magnesium, iron or aluminum salts of 
.beta.-naphthalenesulfonic acid-formaldehyde condensate can be employed as 
an additive to prevent the slump loss in fresh concrete. The slump can be 
kept constant for a long period of time by mixing the powdery Ba, Mg, Fe 
or Al salt of .beta.-NSF of the present invention together with a concrete 
composition or by adding said additive to the composition while the latter 
is mixed, or even after mixing. Furthermore, the slump property can also 
be kept constant for a long period of time when a concrete comprising a 
cement previously blended with the additive of the present invention is 
used. 
The barium, magnesium, iron or aluminum salt of .beta.-NSF does not exert 
any harmful influence upon the physical properties of the concrete. In 
general, the additive of the invention is used in an amount of about 0.01 
to 10 weight percent, preferably about 0.1 to 1.0 weight percent, based on 
the weight of the cement. 
The term "powdery or granular salt" as used herein indicates the salt in 
the form of a powder, granules or coagulum. Preferred additives are those 
having particle diameters of about 10-10,000.infin.. 
The .beta.-NSF additive of the present invention may be prepared by 
condensing .beta.-sulfonated naphthalene with formaldehyde and converting 
the condensate into the salt. If necessary, it may further be 
copolycondensed with other compounds. As compounds to be copolycondensed 
therewith, there may be mentioned, for example, alkylnaphthalenes, phenol, 
anthracene, xylene, benzene, lignin, creosote oil and sulfonated products 
thereof, as well as amino compounds such as memamine and urea and 
derivatives thereof. 
The slump loss preventing additive of the present invention may be employed 
with any class of hydraulic cements including Portland cement, slag 
cement, alumina cement and the like. Portland cement is preferred among 
the hydraulic cements. 
In preparing the concrete composition, the dry ingredients, comprising 
cement, the inert filler material such as fine aggregate (commonly sand) 
and coarse aggregate (commonly stone) and the .beta.-SNF additive may be 
mixed with water in any conventional manner. The additive of the invention 
may be added in powdery or granular form as is, or it may be added as an 
aqueous solution.

The following Examples are given merely as illustrative of the present 
invention and are not to be considered as limiting. Unless otherwise 
noted, the percentages therein and throughout the application are by 
weight. 
EXAMPLE 1 
(1) Components of concrete: 
A mixture was prepared from the following components: 
Cement: Portland cement (Onoda) 
Fine aggregate (sand): 
Maximum size of 5 m/m 
(Source: Kinokawa River, Wakayama, Japan) 
Coarse aggregate (crushed stone): 
Maximum size of 20 m/m 
(Source: Takarazuka, Hyogo, Japan) 
Cement dispersing agent (as shown in Table 1): 
A. Na Salt of .beta.-NSF (hereinafter referred to as MY-150). 
B. Commercially available lignin sulfonate 
C. Commercially available melamine sulfonate/formalin condensate 
D. Powdery Fe salt of .beta.-NSF 
E. Powdery Al salt of .beta.-NSF 
F. Powdery Mg 1alt of .beta.-NSF 
G. Powdery Ba salt of .beta.-NSF 
H. Powdery Li salt of .beta.-NSF 
I. Powdery NH.sub.4 salt of .beta.-NSF 
J. Powdery K salt of .beta.-NSF 
K. Powdery Ca salt of .beta.-NSF 
L. Powdery Na salt of .beta.-NSF 
M. Powdery Zn salt of .beta.-NSF 
Dispersing agents D through M were pulverized and fractions of sizes in the 
range of 1190-2380 microns determined by means of standard sieves of JIS Z 
8801 were used. Experiments Nos. 5-11 in Table 1, The powdery dispersing 
agents were dissolved in water and then the solutions were added to a 
mixture of cement, fine aggregate and coarse aggregate. In Experiments 
Nos. 12-20, the powdery dispersing agents were directly added to a mixture 
of cement, fine aggregate and coarse aggregate. 
(2) Method of mixing concrete and test method: 
The components were weighed so as to make the total amount of the mixed 
product 40 liters. They were then mixed together in a tilting mixer for 3 
minutes. Rotation of the mixer was 24 r.p.m. (normal operation). The 
components were charged in the order of the coarse aggregate, fine 
aggregate, cement, powdery dispersing agent and water (Experiments Nos. 
12-20). In another embodiment, the components were charged in the order of 
the coarse aggregate, fine aggregate, cement and an aqueous solution of 
dispersing agent (Experiments Nos. 2-11). Each mixture was agitated for 3 
minutes. Agitating for 3 minutes, the concrete was once discharged from 
the mixer and the slump and amount of air were determined to obtain the 
values at the time of the completion of agitation. Then, the concrete 
composition was returned to the mixer and allowed to stand for the given 
period of time. Thereafter, normal operation was effected for 0.5 minute 
prior to the discharge of the composition from the mixer. The measurement 
was initiated when the contact of the cement with water was initiated. 
Slumps were determined after 90 and 120 minutes. Then the test pieces were 
collected and cured in water, and the compression strengths thereof were 
determined. The temperature of the concrete was 20.degree..+-.2.degree. C. 
The test results are shown in Table 1. It can be seen from this Table that 
the slump loss is hardly observed in the fresh concretes and that no 
harmful influence was exerted upon the strength of the resulting concrete 
according to the present invention, while the slump loss after 90 minutes 
was remarkable in the cases wherein the dispersing agents were not used, 
wherein commercial dispersing agents were not used, wherein commercial 
dispersing agents were used, wherein a solution of Fe, Al, Mg, Ba, Li, 
NH.sub.4 or K salt of .beta.-NSF was used and wherein powdery Ca, Na or Zn 
salt of .beta.-NSF was used. 
TABLE 1 
__________________________________________________________________________ 
Dispersing Slump (cm) Compressive 
Experi- Agent Mix Proportions (1) 
Directly 
After 
After 
After 
Air strength 
ment Dosage 
W/C 
S/A 
C.sub.3 
W.sub.3 
after 
30 60 90 Content 
(kg/cm.sup.2) 
No. Variety 
(%) (%) 
(%) 
(kg/m.sup.3) 
(kg/m.sup.3) 
mixing 
mins. 
mins. 
mins. 
(%) .sigma.7 
.sigma.28 
__________________________________________________________________________ 
Comparative 
Liquid 
1 -- -- 67.7 
45 300 203 18.7 14.5 
12.4 
10.0 
1.5 185 290 
2 A 0.60 
63.0 
43 300 189 18.1 12.2 
8.1 5.0 1.7 221 325 
3 B 0.25 
" " " " 18.8 13.5 
9.3 5.8 2.3 218 320 
4 C 0.50 
" " " " 17.0 11.5 
7.3 4.4 1.6 228 328 
5 D 0.25 
" " " " 16.8 11.9 
8.0 6.1 1.2 225 328 
6 E " " " " " 16.1 10.7 
7.1 4.9 1.3 231 329 
7 F " " " " " 18.2 12.4 
8.0 5.6 1.5 220 324 
8 G " " " " " 17.6 12.0 
8.6 4.3 1.5 208 328 
9 H " " " " " 16.9 10.9 
6.8 4.7 1.4 215 320 
10 I " " " " " 18.1 11.6 
7.5 4.0 1.2 213 314 
11 J " " " " " 17.4 12.1 
8.0 5.1 1.5 224 322 
Powder 
12 K " 59.7 
" " 179 18.3 13.2 
8.6 5.4 1.2 262 361 
13 L " " " " " 18.1 12.0 
7.7 5.1 1.5 257 353 
14 M " " " " " 17.5 12.1 
7.8 5.3 1.3 254 350 
Present 
Invention 
Powder 
15 D " 64.7 
" " " 17.5 17.8 
17.1 1.4 209 311 
16 D 0.50 
63.0 
" " 189 18.4 19.0 
18.3 
18.1 
1.3 220 328 
17 E 0.25 
64.7 
" " 194 17.3 17.6 
17.2 1.6 205 313 
18 E 0.50 
63.0 
" " 189 18.9 19.3 
18.5 
18.0 
1.2 223 324 
19 F 0.50 
" " " " 19.8 19.5 
16.8 
12.1 
1.5 224 319 
20 G 0.50 
" " " " 19.5 19.2 
16.3 
11.5 
1.1 222 320 
__________________________________________________________________________ 
(1)W;Water 
C;Cement 
S;Fine aggregate 
G;Coarse aggregate 
A;S + G 
EXAMPLE 2 
In the embodiment shown in Example 1, the dispersing agents were added and 
mixed together simultaneously. On the other hand, in this Example, the 
manner of the addition was changed and the slump losses were determined. 
(1) Components of concrete: 
Cement: Onoda normal Portland cement and a cement obtained by mixing Onoda 
normal Portland cement together with 0.56% of powdery .beta.-NSF-Fe salt 
(powders of particle diameters in the range of 4760-1190 microns according 
to a standard sieve) and storing the same in a closed vessel at 20.degree. 
C. for 14 days. 
Fine aggregate: 
Maximum size of 5 m/m 
(Source: Kinokawa River, Wakayama, Japan) 
Coarse aggregate (crushed stone): 
Maximum size of 20 m/m 
(Source: Takarazuka, Hyogo, Japan) 
Cement dispersing agent: Powdery Na or Fe salts of .beta.-NSF having 
particles sizes of 4760-1190 microns. 
(2) Method of mixing concrete and test method: 
The components were weighed so as to make the total amount of the mixed 
product 40 liters. They were then mixed together in a tilting mixer for 3 
minutes. Rotation of the mixer was 24 r.p.m. (normal operation). After 
completion of mixing, the slump and amount of air were measured to obtain 
a value of the slump immediately after the mixing. Then, the concrete 
composition was returned into a mixer and rotated therein at a rate of 4 
r.p.m. A first process for the addition of the dispersing agent comprises 
adding powdery Na salt of .beta.-NSF to MY-150/concrete mixture 30 minutes 
after the contact of the cement with water (Experiment No. 2) or adding 
powdery Fe salt of .beta.-NSF thereto (Experiment No. 4). In a second 
process, powdery Fe salt of .beta.-NSF is added after the determination of 
slump of the dispersing agent-free concrete directly after the mixing 
(Experiment No. 3). In a third process, cement incorporated with 0.56%, 
based on the cement, of Fe salt of .beta.-NSF is used (the cement being 
stored at 20.degree. C. for 14 days) (Experiment No. 5). The time elapsed 
was measured starting at the point when the cement was contacted with 
water. 
The results are shown in Table 2. It is apparent from Table 2 that the 
slump loss was remarkable in the dispersing agent-free concrete after 60 
minutes and that the slump was recovered when powdery Na salt of 
.beta.-NSF was added to MY-150 concrete after 30 minutes, but the slump 
loss was remarkable after 60 minutes. 
When the concrete additive of the present invention is added to the fresh 
concrete immediately after mixing or 30 minutes thereafter, there is 
essentially no slump loss, and no harmful influence is exerted on the 
strength of the concrete. 
TABLE 2 
__________________________________________________________________________ 
Dispersing 
Experi- agent Method Mix Proportions (1) 
ment Dosage 
of W/C S/A C W 
No. Variety 
(%) addition 
(%) (%) (kg/m.sup.3) 
kg/m.sup.3) 
__________________________________________________________________________ 
Comparative 
1 -- -- -- 67.0 
44 300 201 
NSF-Na MY-150 1.2 .beta. 
59.0 43 " 177 
.beta.-NSF-Na 
0.4 added 
after 
30 
mins. 
Present 
Invention 
3 .beta.-NSF-Fe 
0.56 .beta.-NSF-Fe 
" " " " 
added 
direct- 
ly 
NSF-Fe MY-150 1.2 .beta. 
" " " " 
.beta.-NSF-Fe 
0.56 added 
after 
30 
mins. 
5 .beta.-NSF-Fe 
0.56 Pre- " " " " 
blended 
with 
cement 
__________________________________________________________________________ 
Slump(cm) Compressive 
Experi- 
Directly 
After 
After 
After 
After 
After 
Air Strength 
ment after 
15 30 45 60 90 Content 
(kg/cm.sup.2) 
No. mixing 
mins. 
mins. 
mins. 
mins. 
mins. 
(%) .sigma.1 
.sigma.7 
.sigma.28 
__________________________________________________________________________ 
Comparative 
1 18.9 16.1 
12.0 
9.3 
7.9 
6.7 1.3 36 196 
302 
2 19.5 15.2 
10.9 
19.6 
15.3 
8.9 1.2 64 280 
387 
Present 
Invention 
3 6.7 20.5 
20.8 
18.2 
18.1 1.3 59 276 
379 
4 18.7 14.0 
9.7 18.7 
17.8 
17.8 
1.2 62 280 
386 
5 18.2 18.8 
18.4 
17.6 
17.3 1.3 60 273 
372 
__________________________________________________________________________ 
(1)W;Water 
C;Cement 
S;Fine aggregate 
G;Coarse aggregate 
A;S + G 
EXAMPLE 3 
The influence of the slump loss preventing additive of the present 
invention on rich-mix concrete and hot-weather concrete were examined. 
(1) Components of concrete: 
Cement: Onoda normal Portland cement. 
Fine aggregate: Fine aggregate of maximum size of 5 m/m. 
Coarse aggregate: Crushed stone of maximum size of 20 m/m. 
Cement dispersing agent: Powdery MY-150, dispersing agent C and Fe salt of 
.beta.-NSF as used in Example 1 with particle sizes in the range of 
4760-1190 microns. 
(2) Method of mixing concrete and test method: 
The components were weighed so as to make the total amount of the mixed 
product 40 liters. They were then mixed in a tilting mixer for 3 minutes. 
Rotation of the mixer was 24 r.p.m. (normal operation). After completion 
of the mixing, the slump and amount of air were measured to obtain a value 
of slump immediately after the mixing. Then, the concrete composition was 
returned into the mixer and rotated therein at a rate of 4 r.p.m. The 
dispersing agents were added to the concrete composition at the time of 
the mixing (Experiments Nos. 2, 3 and 5) or 30 or 45 minutes after the 
contact with water (Experiments Nos. 4 and 6). The time elapsed was 
measured starting at the point when the cement was contacted with water. 
The temperature of the concrete was 33.degree..+-.2.degree. C. 
The test resuls are shown in Table 3. It is apparent from Table 3 that the 
slump loss was hardly observed when the dispersing agents of the present 
invention were incorporated in fresh concrete and that no harmful 
influence was exerted on the strength of concrete thus obtained, while the 
slump loss was remarkable in dispersing agent-free concretes and concretes 
containing ordinary dispersing agents. 
TABLE 3 
__________________________________________________________________________ 
Dispersing 
Experi- 
agent Method Mix Proportions (1) - 
ment Dosage 
of W/C 
S/A 
C W 
No. Variety 
(%) addition 
(%) 
(%) 
(kg/m.sup.3) 
(kg/m.sup.3) 
__________________________________________________________________________ 
Comparative 
1 -- -- -- 44.4 
40 500 222 
2 MY-150 1.2 Added 35.0 
39 500 175 
at the 
time 
of 
mixing 
3 C 1.0 Added 36.1 
39 500 181 
at the 
time 
of 
mixing 
Present 
Invention 
4 Powdery 
1.2 0.15% 
MY-150 .beta.-NSF-Fe 
35.0 
39 500 175 
.beta.-NSF-Fe 
0.15 
added 
after 
30 mins. 
5 Powdery Added 
.beta.-NSF-Fe 
0.4 at the 35.0 
39 500 175 
time of 
mixing 
6 Powdery 
0.4 0.1% 
.beta.-NSF-Fe 
0.1 after 35.0 
39 500 175 
45 mins. 
__________________________________________________________________________ 
Slump (cm) Compressive 
Experi- 
Directly 
After 
After 
After 
After 
Air Strength 
ment after 
15 30 45 60 Content 
(kg/cm.sup. 2) 
No. mixing 
mins. 
mins. 
mins. 
mins. 
(%) .sigma.1 
.sigma.7 
.sigma.28 
__________________________________________________________________________ 
Comparative 
1 18.5 16.2 
14.6 
12.1 
10.0 
1.4 117 
359 
552 
2 19.0 16.8 
14.2 
10.8 
7.7 
1.3 230 
456 
664 
3 18.0 15.7 
13.9 
10.4 
7.2 
1.5 231 
462 
658 
Present 
Invention 
4 18.3 16.1 
13.8 
19.2 
18.8 
1.2 236 
454 
660 
5 3.0 19.5 
19.9 
18.8 
18.6 
1.3 237 
461 
659 
6 1.1 8.3 
9.5 
8.5 
17.6 
1.4 233 
451 
663 
__________________________________________________________________________ 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications are 
intended to be included within the scope of the following claims.