Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2002-07-23
2004-02-10
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S693000
Reexamination Certificate
active
06689207
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a method for making alumina cement and alumina cement.
Alumina cement is traditionally made from a mixture of bauxite and limestone. The components of this mixture are sometimes crushed and ground then homogenised. This depends on the type of furnace used.
BACKGROUND OF THE INVENTION
The batch composition thus obtained is baked at high temperature, close to 1500 degrees, in a furnace in order to form the clinker.
This clinker is then ground, whereas secondary constituents may be added to form the cement that is then routed to its place of usage.
We know that the clinker produced for the manufacture of alumina cement comprises alumina oxide Al
2
O
3
, represented in the abbreviated notation in the cement industry as A, and lime CaO represented in the same cement industry by the abbreviated notation C. This notation will be used at a later stage for easier reading of this text. The alumina oxide and the lime are crystallised partially in the form C
12
A
7
on the one hand and in the form CA on the other.
According to the nature of the initial mixture, the alumina cement is more or less ferriferous.
Alumina cement is considered in the building chemistry as a raw material that, associated with other components, provides ready-made products such as concrete, mortar, glue, binder and plaster for the manufacture of slabs or cast objects or more generally for any concrete, mortar or plaster.
Seeking improvement in the qualities of the ready-made products leads to the formulation of products that would associate, to alumina cement, lime, Portland cement, calcium sulphate, as well as a number of additives or assistants.
It has also appeared that the quality of the ready-made products highly depends on the properties and on the quality of alumina cement.
Optimised alumina cement enables extending the workability of a mortar, as well as increasing its fluidity, while maintaining very quick hardening kinetics.
SUMMARY OF THE INVENTION
In other words, the ready-made product using this kind of cement will be applicable for a longer time, but it will achieve final performances at least as rapidly.
The properties of alumina cements are more particularly expressed by the initial and final setting, the flow value in percentage, the resistance after 6 hours and the resistance after 24 hours.
The purpose of the invention is therefore the production of specific alumina cement whose properties enable the realisation of high quality ready-made products.
To this end, the invention concerns a method for making alumina cement as defined above wherein the concentration d3 in alumina Al
2
O
3
, —A— and the concentration d4 in lime CaO, —C— in the initial mixture are such that d3/d4 ranges between 1.15 and 1.40, and grinding produces a cement with size distribution as represented in a Rosin Rammler diagram that has a gradient ranging between 0.75 and 0.90. In the invention, the concentration d3 represents the percentage by weight of Al
2
O
3
in the initial mixture, and the concentration d4 represent the percentage by weight of CaO in the initial mixture.
The combination of the mineralogical properties of the initial composition and of the chemical properties of the clinkers with particular size distribution enables reaching the expected results, independently from the other conventional operating conditions of the process. Therefore, while improving the properties of alumina cement, higher quality ready-made products are obtained.
Controlling the relative concentration in alumina d3 and in lime d4 in the initial mixture, whereas the ratio of these concentrations d3/d4 ranges between 1.15 and 1.40 and the firing process takes place under oxidising atmosphere, enables low concentration of C
12
A
7
in the clinker.
The invention also relates to a plant for making alumina cement implementing the method defined above. Firing under oxidising atmosphere, if any, can take place in a reverberatory furnace, a rotary furnace or still an electric furnace. Conversely, the usual firing conditions are reducing conditions leading to high C
12
A
7
content.
The invention also concerns an alumina cement wherein the concentration d3 in alumina, —A— and the concentration d4 in lime, —C— are such that d3/d4 ranges between 1.15 and 1.40, and whose size distribution as represented in a Rosin Rammler diagram has a gradient ranging between 0.75 and 0.90.
The Blaine fineness of the cement ranges preferably between 2,000 and 5,000 cm
2
/g, advantageously around 3,500 cm
2
/g.
REFERENCES:
patent: 1643137 (1927-09-01), Spackman
patent: 3963508 (1976-06-01), Masaryk
patent: 4116707 (1978-09-01), Oborin et al.
patent: 4396422 (1983-08-01), Matsuno et al.
patent: 2 152 410 (1972-05-01), None
patent: 26 49 032 (1978-04-01), None
patent: 233 836 (1986-03-01), None
patent: 2 033 369 (1980-05-01), None
By J. Bensted, “High alumina cement—Present state of knowledge”,ZKG International, vol. 46, Sep. 9, 1993, pp. 560-566.
Bier Thomas
Espinosa Bruno
Klemanski Helene
LafargeSaluminates
Young & Thompson
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