AN IMPROVED MANUFACTURE OF CEMENT
Year: 1884

page_text: I, LUDWIG ROTH, of Wetzlar, Prussia, Germany, Engineer, do hereby declare
the nature of my invention for AN IMPROVED MANUFACTURE OF CEMENT, and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:
The experiments hitherto made for producing cement by burning a mixture of
furnace-slag, and lime or chalk, have generally failed to produce a material in every
respect equal to portland cement.
This invention has for its object to produce cement which is equal, and in some
respects superior in quality, to the best portland cement, by adding a further
ingredient to the above mentioned mixture.
The process is as follows:
Furnace slag as obtained as a bye-product in the production of pig-iron, and
lime stone, dolomite, or chalk, either raw or burnt, are finely pulverised and
thoroughly mixed.
This material is mixed with an aqueous solution of an alkali-salt, such as
potassic chloride, sodic chloride, rock salt, carnallite, saltpetre, soda, kainit, or
potash, and transformed into a mouldy paste.
This paste is then formed into bricks or balls which are dried, burnt and
comminuted in the manner usually applied in the production of portland cement.
The raw materials as enumerated above may be mixed when moist by means of
suitable stirring apparatus, and instead of the artificial solution of alkali-salts
natural brine may be employed.
If the natural brine does not contain sufficient alkali-salts in solution, it should
either be concentrated by evaporation, or strengthened by the addition of alkali
salts.
As regards the proportion in which the different raw materials form part of the
mixture, I prefer to fix the quantity of lime to be added, so that the finished
cement contains about an equal or even a larger quantity of lime than good
portland cement. The quantity of lime required for the mixture may easily be
calculated by means of a chemical analysis of the furnace-slag.
Cement produced by this process should generally contain from 60 to 65 per cent.
of lime, but exact limits for all cases can not be given.
The quantity of alkali-salts to be applied in the process should be fixed in each
individual case by experiments.

page_text: A comparatively small admixture of alkali-salt has already a favourable influenco
on the quality of the cement. A few parts of alkali-salt in a thousand parts of
the mixture exercise already a favourable influence on the product, and it is
advisable to increase the quantity of alkali-salts to 1 or more per cent., but not to
go far beyond this quantity because, if too much is added, the cement becomes very
hygroscopic, so as to absorb too large a quantity of water when stored for a longer
period.
By mixing for instance 100 kilogrammes of pulverized highly basic furnace-slag
(containing about 50 per cent: of lime and 35 per cent. of silicic acid), with
135 kilogrammes of lime-stone or chalk, and by adding to this mixture a solution
of 15 to 20 kilogrammes of carnallite or rocksalt, a superior quality of cement may
be produced by the process described.
If the furnace-slag is not rich in alumina (which exercises a great influence on
the quality of the cement), I recommend to add to the mixture of raw materials a
quantity of bauxit in the proportion set forth in the specification of the Euglish
Patent No 3702 A.D. 1882.
'
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is:
The manufacture of cement by burning and pulverizing a mixture of furnace slag
with raw or burnt lime-stone, chalk, or dolomite, and with alkali-salts, such as
potassic chloride, sodic chloride, rock-salt, carnallite, saltpetre, soda, kainit or
potash, eventually with the addition of bauxit.
Dated this 12th day of January 1884.
LUDWIG ROTH.
Per Herbert & Co., Agents.