Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2002-10-24
2004-02-24
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S693000, C106S695000, C106S712000, C106S735000
Reexamination Certificate
active
06695910
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a new sulfoaluminous clinker, its process of preparation and its use in binders, in particular in binders that are lightly tinted, lightly colored or white.
DESCRIPTION OF THE RELATED ART
Hydraulic binders (including cements) are mineral powders which react with water so as to form a malleable paste which hardens after several hours.
The terms “hydraulic binder” and “cement” are frequently confused. Generally speaking, the hydraulic binders are comprised of cements with mineral additives. The production of the cement consists in roasting a mixture, comprised of suitable materials, in a rotating kiln, at high temperature (higher than 1450° C.). The nodules obtained after roasting, called clinker nodules, are ground to a suitable fineness (or specific surface) so as to activate the affinity of the cement for water. The cement is thus a ground clinker, with possible mineral additions.
Cements are illustrated conventionally by two types, Portland cements and aluminous cements.
To facilitate explanation, the standard abbreviations used in the text that follows are as follows:
C represents CaO
{overscore (S)} represents SO
3
A represents Al
2
O
3
H represents H
2
O
S represents SiO
2
T represents TiO
2
F represents Fe
2
O
3
Cements of the Portland type are comprised by four principal phases, alite C
3
S (40-70%), belite C
2
S (up to 30%), tricalcium aluminate C
3
A (2-15%) and ferrite C
4
AF (up to 15%). Gypsum is conventionally added (up to 5%) during grinding the clinker.
Cements of the aluminous type cover a range of binders which includes monocalcium aluminate CA as the principal constituent. The other principal phases of this range of cements are the ferrite phase C
4
AF, and the calcium dialuminate phase CA
2
.
A new type of cement has been created in the past 70 years. It is characterized by one of its phases called calcium sulfoaluminate C
4
A
3
{overscore (S)} (Klein phase). The other phases are generally C
2
S, C
4
AF, CA, CA
2
, C
12
A
7
, C{overscore (S)} and free lime. Calcium sulfoaluminate hydrates differently as a function of the other phases present in the binder (binder=cement+addition of active minerals):
if C
4
A
3
{overscore (S)} is the only reactive hydraulic phase, the products of hydration are calcium monosulfoaluminate and aluminum hydroxide:
C
4
A
3
{overscore (S)}+18H→C
4
A{overscore (S)}H
12
+2AH
3
(1)
This reaction begins very slowly and the paste remains malleable for a fairly long period of time.
In the presence of gypsum (or other calcium sulfate phases) C
4
A
3
S gives place to ettringite as the lower ratio gypsum/sulfoaluminate is greater than 2, and gives ettringite and calcium monosulfoaluminate in contrary case:
2C
4
A
3
{overscore (S)}+2C{overscore (S)}H
2
+52H→C
6
A{overscore (S)}
3
H
32
+C
4
ASH
12
+4AH
3
(2)
C
4
A
3
{overscore (S)}+2C{overscore (S)}H
2
+34H→C
6
A{overscore (S)}
3
H
32
+2AH
3
(3)
Reactions (2) and (3) begin more rapidly than reaction (1), and after beginning, are fairly rapid. As a consequence, the C
4
A
3
{overscore (S)} base cements in the presence of calcium sulfate are the cements that set up rapidly with a period of malleability of more than 30 minutes. Moreover, with an excess of gypsum (molar ratio of calcium sulfate/calcium sulfoaluminate>2), they increase in volume.
Mixtures of C
4
A
3
{overscore (S)} and lime (calcium oxide) give place to a hydraugarnet phase (C
3
AH
6
) and to an Afm phase (C
3
A.½C{overscore (S)}.½CH.xH):
C
4
A
3
{overscore (S)}+7CH+2xH→C
3
AH
6
+2(C
3
A.½C{overscore (S)}.½CH.xH) (4)
Mixtures of C
4
A
3
{overscore (S)}, lime and calcium sulfate hydrate very rapidly to form ettringite:
C
4
A
3
S+8CSH
2
+6C+80H→3C
6
AS
3
H
32
(5)
Here again, properties of expansion can be obtained if lime and the calcium sulfate are in excess.
Reactions (4) and (5) are very rapid and lead very quickly to setting up (which is to say in several minutes) and give rise to cements that harden very rapidly. Lime can be present in the binder as a portion of the composition, or can be the result of the dissolution of another phase: the principal phase of Portland cement C
3
S, once in contact with water, liberates calcium hydroxide (the hydrated form of lime) which in turn accelerates the formation of hydrates according to reactions (4) or (5).
As a result, the kinetics of hydration of C
4
A
3
{overscore (S)} depend largely on the phases present in the binder. This leads to different applications according to whether it is desired to obtain rapid hardening, rapid setup and/or properties of expansion. Several examples are cited hereafter:
U.S. Pat. Nos. 3,251,701, 3,155,526, 4,419,136 and 3,857,714 disclose expanding binders produced from a clinker including the calcium sulfoaluminate content of the clinker which is mixed with other constituents (for example gypsum or Portland cement) so as produce ettringite (reaction (3) or (5)) with an excess of gypsum and/or lime. This clinker, containing not only C
4
A
3
{overscore (S)} but also lime and anhydrite, has limited application because of the long setup time (reaction (1)), which is required for numerous applications, is impossible to obtain.
U.S. Pat. No. 3,860,433 discloses a very high strength cement, with rapid setup comprised by 20 to 40% C
4
A
3
{overscore (S)}, 10 to 35% C{overscore (S)}, the rest being essentially C
2
S. Because the C{overscore (S )}content is high, the crushed clinker hydrates according to reactions (2) or (3). Obtaining a binder with a long setup time, such as reaction (1) favors, is impossible.
Ferro- and sulfoaluminous clinkers developed by CBMA (China Building Materials Academy) are comprised principally of C
4
A
3
{overscore (S)}, C
2
S and C
4
AF (see Table 1). They are very useful for general applications and specific applications such as construction in winter, the production of subterranean structures, marine construction and applications for reinforced concrete resistant to corrosion. However, their C
4
AF content is always greater than 3%. This gives them a dark color. It is thus not of interest to incorporate clinkers in binders that must remain lightly colored or pigmented, such as coatings.
TABLE 1
Compositions of ferro- and sulfoaluminous clinkers of CBMA
C
4
A
3
{overscore (S)}
C
2
S
C
4
AF
Sulfoaluminous
50-70%
10-25%
3-10%
Ferroaluminous
45-60%
10-20%
15-25%
WO 90/15033 discloses a clinker roasted between 1000 and 1200° C., comprised with a high content of C
4
A
3
{overscore (S)}, with a molar ratio A/F greater than 0.64. There thus exists a ferrite phase in this clinker. The roasting temperature being very low, free lime must be present in a substantial quantity in the clinker, which prevents its use for applications with long setup times.
The patent EP 0 181 739 also discloses a clinker having a high content of C
4
A
3
{overscore (S)}, with less than 1% free lime. However, this clinker includes iron (ferrite phase) which gives it a dark color (see Table 7 hereafter), and other phases such as CA
2
, CA and C
2
AS in large quantities (of the order of 20%).
It will thus be seen that each calcium sulfoaluminate base cement is adapted for limited uses. The producer must thus give users a range of sulfoaluminous clinkers of different types to suit various desired uses (short or long setup time, expansion, rapid hardening, high strength . . . ).
SUMMARY OF THE INVENTION
A first object of the invention is thus to provide a unique sulfoaluminous clinker, which permits, by combining it with calcium sulfate and/or Portland cement in suitable proportions, obtaining binders having desirable properties, particularly as to contraction/expansion, setup time, hardening and mechanical strength.
Another object of the invention is to provide a sulfoaluminous clinker of light color, even substantially white, which is to say in which the iron oxides or the other colored oxides such
Classen Bruno
Colombet Pierre
Ciments Francais
Green Anthony J.
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