Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2001-10-08
2003-03-25
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S693000, C106S694000, C106S695000, C106S722000
Reexamination Certificate
active
06537365
ABSTRACT:
FIELD OF THE INVENTION
This invention relates mainly to cement clinker and method for manufacturing the same, or cement composition containing the cement clinker, as well as method for treatment of waste containing alkali components for use as a cement raw material.
BACKGROUND OF THE INVENTION
In these years, recycling of wastes has arisen as a critical issue in view of global environment protection regardless of whether it belongs to government or industrial circle. Along with this situation, the cement industry has been positively promoting the recycling of wastes through the use of fly ash or blast-furnace slag as blended cement, or of various wastes as cement raw materials, and is expected to play an important role in the waste recycling.
Recently, there have been carried out various studies such as on “Eco-Cement” to use chlorine-containing waste such as municipal solid waste as a raw material for special cement, and “Completely-Recycled-Cement” to make up the recycling system which enables the manufacturing of cement by using only the recyclable materials as cement raw materials and the reuse of the same as cement raw materials after served.
However, the statistical fact is that 25 million tons of concrete waste is generated per year, of which 10 million tons are used as roadbed materials, while 15 million tons are thrown out. As a part of “Development of Techniques to Suppress Generation of Construction Byproducts and Recycle the Same” (1993-1994), a total technical development project of Japanese Ministry of Construction, a joint study on “Development of Utilization Technique of Recycled Concrete” was carried out, through which steady movement towards the recycling proceeds. However, there still remain numbers of problems on recycling of concrete waste as a recycled aggregate.
One of the problems arises in reusing fine particles worn out and removed from the surface of an aggregate during the recycling process for manufacturing a recycled aggregate of good quality. Considering the possibility to reuse fine particles as a cement raw material in the recycling method, it is appeared that the reusing of the fine particles as cement raw material is hardly achieved since alkali components contained in the fine particles deteriorate the flow ability of cement in association with the fact that the content of alkali components is 0.75% or less, a value prescribed by JIS.
Glass waste, sludge cake of bentonite used in building operations, or the like also poses a problem due to an excessive amount of alkali components contained therein when used as a cement raw material. Specifically, while an established system for reuse of glass waste by crushing it into cutlet exists, the reuse of colored glass is limited. Accordingly, there is a demand to the reuse of colored glass as cement raw material. However, these wastes also contain a large quantity of alkali components likewise the treatment of fine particles generated during manufacturing recycled aggregate, so that the a possibility to reuse these wastes as cement raw materials is greatly lowered.
SUMMARY OF THE INVENTION
It is an object of the present invention to suppress deterioration of the flowability, as well as simultaneously enhancing the hydration of belite or the like mainly comprised of C
2
S, when alkali components have been incorporated into cement, thereby attempting effective use of waste containing alkali components as a cement raw material.
Considering the utilization of an alkali component-containing waste as a cement raw material, there remains a possibility to reuse the same, as far as the conditions that (i) a reactive aggregate is not used when cement is used as mortar, concrete or the like, and (ii) the prescribed value of the content of alkali components in cement is relaxed are met. Particularly, the incorporation of the alkali component-containing waste into a cement raw material with a large quantity of belite formed therein increases the solid-solution amount of alkali components in belite during the firing operation, thereby improving an inherently low hydration reactivity of belite. This improvement of the hydration reactivity leads to enhancement of a middle- and long-term strength development of cement, and hence is considered as a reasonable solution.
However, where the content of alkali components in a normal belite cement is increased, although there is produced a positive effect that the hydration is enhanced by the solid solution of alkali in belite, the alkali solid solution simultaneously occurs in a calcium aluminate phase whose hydration reactivity is inherently high. Accordingly, the hydration reactivity in the calcium aluminate phase is increased. This poses a new problem of lowering the flowability of cement paste, mortar, concrete or the like in actual use.
The present inventors have repeatedly studied in earnest to solve the above problem, and found that through the adjustment of the mass ratio of Al
2
O
3
/Fe
2
O
3
in cement clinker, the ratio of the content of alkali components to the content of belite, and the ratio of Na
2
O to K
2
O in alkali within predetermined ranges suppresses the lowering of the flowability while enhancing the hydration reactivity of belite. Thus, the present invention has been achieved.
According to the present invention, there is provided cement clinker which is characterized in that it comprises Al
2
O
3
and Fe
2
O
3
wherein the mass ratio of Al
2
O
3
/Fe
2
O
3
is 0.05-0.62, and alkali components and C
2
S wherein the content Y (mass %) of alkali components and the content X (mass %) of C
2
S satisfy the formula: 0.0025X+0.1≦Y≦0.01X+0.8.
The content Y of alkali components and the content X of C
2
S are respectively represented in mass % of the content of alkali components and C
2
S to the total mass of the cement clinker.
According to another aspect of the present invention, there is provided cement clinker which is characterized in that it comprises Al
2
O
3
and Fe
2
O
3
wherein the mass ratio of Al
2
O
3
/Fe
2
O
3
is 0.05-0.62, and alkali components and C
2
S wherein the content Y (mass %) of alkali components and the content X (mass %) of C
2
S satisfy the formulae:
0.0025X+0.25≦Y≦0.01X+0.8 when 0.05≦Al
2
O
3
/Fe
2
O
3
≦0.3, (1)
and
0.0025X+0.25≦Y≦0.01X+0.65 when 0.3≦Al
2
O
3
/Fe
2
O
3
≦0.5. (2)
Also, in the cement clinker of the present invention, the mass ratio of Na
2
O to K
2
O of the alkali components preferably satisfies the formula: 0≦Na
2
O/K
2
O≦0.45
According to another aspect of the present invention, there is provided a cement composition which is characterized in that the aforesaid cement clinker is mixed thereinto.
According to still another aspect of the present invention, there is provided a method for manufacturing cement clinker that comprises incorporating Al
2
O
3
and Fe
2
O
3
at the mass ratio of Al
2
O
3
to Fe
2
O
3
being 0.05-0.62, incorporating alkali components and C
2
S with the content Y (mass %) of alkali components and the content X (mass %) of C
2
S satisfying the formula: 0.0025X+0.1≦Y≦0.01X+0.8, and firing the resultant.
According to another aspect of the present invention, there is provided a method of treating waste containing an alkali components, which is characterized in that it comprises incorporating Al
2
O
3
and Fe
2
O
3
at the mass ratio of Al
2
O
3
to Fe
2
O
3
being 0.05-0.62, incorporating alkali components and C
2
S with the content Y (mass %) of alkali components and the content X (mass %) of C
2
S satisfying the formula: 0.0025X+0.1≦Y≦0.01X+0.8, and firing the resultant.
In the method of the present invention, the mass ratio of Na
2
O to K
2
O in the alkali components preferably satisfies the formula: 0≦Na
2
O/K
2
O≦0.4.
It is possible to manufacture the cement clinker containing alkali components by incorporating alkali components into a cement raw material and firing the resultant. It is presumable that the alkali components in the cement clinker exist mainly in a soli
Akiyama Tatsushi
Ikabata Tatsuo
Kano Kazuhiro
Marcantoni Paul
Sumitomo Osaka Cement Co. Ltd.
Wood Phillips Katz Clark & Mortimer
LandOfFree
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