Ultra high-strength hydraulic cement compositions

Ultra high-strength hydraulic cement compositions with extremely low water-to-cement ratio of 10-30% and having high fluidity and improved capability of preventing slump loss, from which high-quality ultra high-strength hardened concrete and mortar can be obtained with superior workability, contain a binder composed of cement or a mixture of cement and a microscopic powder admixture, aggregates, water and a cement dispersion agent composed of water-soluble vinyl copolymers obtained by aqueous solution radical polymerization of five specified kinds of monomers at a ratio within a specified range The unit content of the binder is 400-1300kg/m.sup.3, the water-to-binder ratio is 10-30% and the content of cement dispersion agent is 0.1-2.0 weight parts for 100 weight parts of the binder.

BACKGROUND OF THE INVENTION 
This invention relates to ultra high-strength hydraulic cement compositions 
with significantly improved fluidity and workability adapted for use in 
the production of ultra high-strength concrete and mortar. 
In order to produce high-strength concrete, it has been known to reduce the 
water-to-cement ratio and to make up for the resultant lowering of its 
fluidity by using a cement dispersion agent such as condensation products 
of naphthalene sulfonic acid and formaldehyde, condensation products of 
melamine sulfonic acid and formaldehyde or water-soluble vinyl copolymers 
(U.S. Pat. No. 4,962,173 and Japanese Patent Application Tokkai 3-93660). 
For the purpose of production of high-strength concrete, it has also been 
known to reduce the water-to-cement ratio and to use a microscopic powder 
admixture such as silica fume or blast-furnace slag in addition to cement 
(Japanese Patent Publications Tokko 60-59182 and Tokkai 3-93660). 
If such a prior art method is used for the production of an ultra 
high-strength hydraulic cement composition from which high quality ultra 
high-strength hardened concrete with compressive strength greater than 
1100kgf/cm.sup.2 can be obtained by keeping the water-to-cement ratio 
extremely low, however, it is not possible to obtain sufficiently large 
fluidity, and the drop in its fluidity with the passage of time after the 
mixing (hereinafter referred to as the slump loss) is significantly large. 
In other words, only compositions with poor fluidity and workability, 
having no practical use, can be obtained. 
SUMMARY OF THE INVENTION 
The problem to be solved by the present invention is, as discussed above, 
that prior art methods for producing ultra high-strength hydraulic cement 
compositions cannot yield sufficient fluidity, but the slump loss is 
large, and only compositions with extremely poor fluidity and workability 
and having no practical use can be obtained. 
The present inventors discovered, as a result of their diligent research in 
order to find solutions to this problem, that use as cement dispersion 
agent should be made of a water-soluble vinyl copolymer obtained by 
aqueous solution radical copolymerization of five specified kinds of 
monomers at specified ratios of copolymerization and by setting the unit 
content of a binder, the water-to-binder ratio and the content of the 
cement dispersion agent with respect to the binder each within a specified 
range. 
DETAILED DESCRIPTION OF THE INVENTION 
This invention relates to an ultra high-strength hydraulic cement 
composition comprising a binder composed of cement or a mixture of cement 
and a microscopic powder admixture, aggregates, water and a cement 
dispersion agent, characterized wherein the unit content of the binder is 
400-1300kg/m.sup.3, the water-to-binder ratio is 10-30%, the content of 
the cement dispersion agent is 0.1-2.0 weight parts with respect to 100 
weight parts of the binder, and the cement dispersion agent is a 
water-soluble vinyl copolymer obtained by aqueous solution radical 
copolymerization of a first monomer shown by Formula (1) given below, a 
second monomer shown by Formula (2) give below, a third monomer shown by 
Formula (3) given below, a fourth monomer shown by Formula (4) given below 
and a fifth monomer shown by Formula (5) given below such that the ratio 
of constituent monomer units is (First monomer)/(Second monomer)/(Third 
monomer)/(Fourth monomer)/(Fifth monomer)=45-65/8-23/3-25/5-25/0.1-15 
(molar %) as converted to monomers, where: 
Formula (1) is 
##STR1## 
Formula ( 2 ) is 
##STR2## 
Formula ( 3 ) is 
##STR3## 
Formula ( 4 ) is 
##STR4## 
Formula ( 5 ) is 
##STR5## 
where R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.6 are each H or 
CH.sub.3 ; R.sup.5 and R.sup.7 are each an alkyl group with 1-3 carbon 
atoms; M.sup.1 is an alkali metal, an alkaline earth metal, ammonium or 
organic amine; m is an integer 1-30; n is an integer 5-25; X is --SO.sub.3 
M.sup.2 or an organic group shown by 
##STR6## 
where M.sup.2 is one selected from the group consisting of alkali metals, 
alkaline earth metals, ammonium and organic amines. 
The binder to be used according to the present invention is either cement 
or a mixture of cement and a microscopic powder admixture. Examples of 
cement which may be used include many kinds of portland cement such as 
ordinary portland cement, high early strength portland cement and moderate 
heat portland cement, fly ash cement, blast furnace cement, silica cement 
and many kinds of blended cement. Examples of microscopic powder admixture 
include silica fume, blast-furnace slag and fly ash. It is preferable, 
however, to use a mixture of cement and silica fume as the binder. In this 
situation, it is preferable if the content of silica fume is 1-30 weight % 
of the binder and it is even more preferable if it is 3-25 weight %. There 
is no particular limitation as to the kind or characteristics of the 
silica fume, but use is usually made of silica fume having hyaline silicon 
dioxide as its principal component and having average diameter of 0.01-1 
.mu.m. 
The water-soluble vinyl copolymer, serving as cement dispersion agent 
according to the present invention, is obtained by aqueous solution 
radical copolymerization of a first monomer shown by Formula (1), a second 
monomer shown by Formula (2), a third monomer shown by Formula (3), a 
fourth monomer shown by Formula (4) and a fifth monomer shown by Formula 
(5). Examples of the first monomer shown by Formula (1) include salts of 
alkali metals, salts of alkaline earth metals and alkanol amine salts of 
(meth)acrylic acid. Examples of the second monomer shown by Formula (2) 
include (i) methallylsulfonates such as alkali metal salts, alkaline earth 
metal salts and alkanol amine salts of methallylsulfonic acid; and (ii) 
p-methallyloxybenzene sulfonates such as alkali metal salt, alkaline earth 
metal salts and alkanol amine salts of p-methallyloxybenzene sulfonic 
acid. Examples of the third monomer shown by Formula (3) include 
polyethyleneglycol mono(meth) allylether and methoxy polyethyleneglycol 
(meth)allylether each with molar number of additive ethylene oxide within 
the range of 1-30 and preferably 5-25. Examples of the fourth monomer 
shown by Formula (4) include alkoxy polyethyleneglycol (meth)acrylates 
such as (meth) acrylates of methoxy polyethyleneglycol, ethoxy 
polyethyleneglycol, propoxy polyethyleneglycol and isopropoxy 
polyethyleneglycol each with the molar number of additive ethylene oxide 
within the range of 5-25. Examples of the fifth monomer shown by Formula 
(5) include alkyl(meth)acrylates such as methyl(meth)acrylate, 
ethyl(meth)acrylate, propyl(meth)acrylate and isopropyl(meth)acrylate. 
As explained above, the water-soluble vinyl copolymers, serving as cement 
dispersion agents according to the present invention, are obtained by 
aqueous solution radical copolymerization of first, second, third, fourth 
and fifth monomers respectively shown by Formulas (1), (2), (3), (4) and 
(5), but their copolymerization ratio (as converted to these monomers) is 
in the range of (First monomer)/(Second monomer)/(Third monomer)/(Fourth 
monomer)/(Fifth monomer)= 45-65/8-23/3-25/5-25/0.1-15 (molar %) and more 
preferably in the range of 50-62/10-20/5-20/7-20/1-12 (molar %). If the 
ratio of any of these monomers falls out of the given range, the 
water-soluble vinyl copolymer which is obtained cannot exhibit the desired 
effects as a cement dispersion agent. Among the water-soluble vinyl 
copolymers thus obtained, those with average numerical molecular weight 
within the range of 2000-20000 (Pullulan converted by GPC method) are 
desirable from the point of view of fluidity provided to ultra 
high-strength hydraulic cement compositions when this is used as a cement 
dispersion agent and the effect on prevention of slump loss. 
Of the five kinds of monomers shown by Formulas (1)-(5) above, the second 
and third monomers shown by Formulas (2) and (3) are particularly 
important. If methallylsulfonate and p-methallyloxybenzene sulfonate are 
used simultaneously as a second monomer shown by Formula (2), in 
particular, the water-soluble vinyl monomer thereby obtained can provide 
even more improved fluidity to cement compositions mixed with microscopic 
powder admixtures such as silica fume, blast-furnace slag and fly ash as 
binder. The third monomer shown by Formula (3) serves to provide high 
fluidity to ultra high-strength hydraulic cement compositions with 
extremely low water-to-cement ratio. 
The water-soluble vinyl copolymers to be used as a cement dispersion agent 
according to the present invention are obtained by aqueous solution 
radical copolymerization of the monomers described above at specified 
copolymerization ratios in the presence of a radical initiator. As for the 
method of copolymerization, it is important to use water or a mixture of 
water and a water-soluble organic solvent in an aqueous solution 
polymerization process. This may be done, for example, by first dissolving 
each monomer in water and preparing an aqueous solution containing each 
monomer with total content of 10-45%. Next, this aqueous solution is kept 
in a nitrogen gas, and a radical initiator is added for a radical 
copolymerization reaction at 50-70.degree. C. for 5-8 hours to obtain a 
water-soluble vinyl copolymer. There is no limitation as to the kind of 
radical initiator to be used for this purpose as long as it is dissociated 
at the temperature of copolymerization reaction to initiate radical 
polymerization, but it is preferable to use a water-soluble radical 
initiator. Examples of such water-soluble radical initiator include 
potassium persulfate, ammonium persulfate, hydrogen peroxide and 
2,2'-azobis( 2-amidinopropane) dihydrochloride. They can also be used as a 
redox initiator by combining with a reducing agent such as sulfites and 
L-ascorbic acid or an amine. 
Ultra high-strength hydraulic cement compositions according to the present 
invention are characterized not only as comprising a binder, aggregates, 
water and a cement dispersion agent but also wherein the unit content of 
the binder is 400-1300kg/m.sup.3, the water-to-binder ratio is 10-30%, and 
the content of the cement dispersion agent is 0.1-2.0 weight parts, or 
preferably 0.2-1.8 weight parts, per 100 weight parts of the binder. If 
the ultra high-strength hydraulic cement composition is a concrete 
composition, it is preferable to adjust the unit content of the binder to 
500-800kg/m.sup.3 and to make the water-to-binder ratio equal to or 
greater than 15% and less than 25%, or even more preferably in the range 
of 15-20%. If the unit content of the binder is less than 400kg/m.sup.3, 
desired ultra high-strength hardened concrete and mortar cannot be 
obtained. If it exceeds 1300kg/m.sup.3, on the other hand, the process of 
mixing by kneading itself becomes difficult. If the water-to-binder ratio 
is less than 10%, the process of mixing by kneading becomes difficult, and 
if it exceeds 30%, desired ultra high-strength hardened concrete and 
mortar cannot be obtained. If the content of cement dispersion agent per 
100 weight parts of the binder is less than 0.1 weight part, it is not 
possible to obtain desired ultra high-strength hydraulic cement 
compositions with sufficient fluidity and effects of preventing slump 
loss. If it exceeds 2 weight parts, on the other hand, setting retardation 
becomes great and affects the hardening process adversely. In some 
situations, there may even be an occurrence of segregation, and desired 
high-quality ultra high-strength hardened concrete and mortar cannot be 
obtained. 
In order to provide a desired level of ultra high strength to ultra 
high-strength hydraulic cement compositions of the present invention, it 
is important to adjust the amount of entrained air appropriately. 
According to the present invention, the amount of entrained air is 
generally less than 2% and, more preferably, adjusted in the range of 
0.7-1.5%. In order to adjust the amount of entrained air appropriately, 
ultra high-strength hydraulic cement compositions of the present invention 
may further contain an antifoaming agent. 
Examples of such antifoaming agent include polyoxyalkylene-glycol monoalkyl 
ethers and polyoxyalkyleneglycol monoalkenyl ethers such as those obtained 
by adding alkylene oxide such as ethylene oxide and propylene oxide to 
aliphatic alcohol with 12-20 carbon atoms, but those with alkylene oxide 
formed by block addition of ethylene oxide and propylene oxide are 
preferred. This invention does not provide limitations as to the molar 
numbers of added ethylene oxide and propylene oxide, but 2-10 moles of 
ethylene oxide and 30-50 moles of propylene oxide are usually added to one 
mole of aliphatic alcohol. Practical examples of antifoaming agent include 
polyoxyethylene (6 mole)/polyoxypropylene (40 mole) block oleyl ether. 
The content of the deforming agent should be as little as possible. It is 
generally adjusted to be less than 0.03 weight % with respect to the 
binder, or more preferably less than 0.02 weight %. Ultra high-strength 
hydraulic cement compositions of the present invention containing an 
antifoaming agent can produce even higher-quality ultra high-strength 
hardened concrete and mortar because unstable entrained air can be 
effectively eliminated. 
The invention will be described below by way of examples but these examples 
are not intended to limit the scope of the invention. In what follows, 
"parts" will mean "weight parts" and "%" will mean "weight %" except where 
the amount of air is considered.