Improvements in the Manufacture of Artificial Roman Cement.
Year: 1891

page_text: Date of Application, 30th Jan:, 1891
Complete Specification Left, 20th Oct., 1891-Accepted, 21st Nov., 1891
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Artificial Roman Cement.
I, CARL VON FORELL of Brunswick in the Duchy of Brunswick, and Empire
of Germany, Director of the Brunswick Cement Works, do hereby declare the
nature of this invention to be as follows:-
Nearly all Roman cements contain more or less uncombined lime. This lime
proceeds from the carbonate of lime, which was used as a raw material of the
mixture and which does not enter into chemical combination owing to the
comparatively low temperature at which the cement is burned in the furnace. I
have found that, if such Roman cement be mixed with a very finely powdered
material, which is rich in alumina in such proportions that the "hydraulic factors"
(silica, alumina and iron peroxide) stand to the lime in the proportion of 1 to 1.7,
an energetic action of the lime on the "hydraulic factors" takes place, as soon as
such cement is actually used, that is to say, as soon as the cement is moistened with
water. The whole mass in time then becomes stiff and hard.
Up to the present, it has been the custom in practice to convert aluminous marls
directly into Roman cement without the addition of mixings. The product
obtained has a good many drawbacks owing to the changing nature of its
composition. Above all things, it has only a small solidity.
According to the present invention, an artificial Roman cement is produced,
which forms a very uniform and solid article on account of its uniform composition
and owing to certain chemical reactions taking place in its application.
The chemical process, when adding aluminous materials to burned Roman cement,
can be explained in this way, namely
The burned lime contained in the burned Roman cement is slaked when
moistened and attacks, in this state, the silicates of alumina in exactly the same
manner as aqueous solutions of caustic alkalies. The lime combines with a portion
of the "hydraulic factors" which are contained in the silicates of alumina, and
causes hereby a chemical compound, which brings about a great solidity.
In the practical working of this process, I proceed thus :-
Marls rich in alumina are burned below the temperature of sintering, until all
the carbonic acid is driven off. The mass is then broken up to a very fine powder
by well known means. The accurate proportion of the lime to the "hydraulic
factors" is then determined by means of a chemical analysis, and so much of the
very finely powdered silicate of alumina is added that the mixture obtained
contains lime and the "hydraulic factors" in the proportion of 1-7 to 1.
exact proportion is of very great importance, especially as I have found that the
careful observation of the proportion mentioned yields a product which answers
the highest expectations as to mechanical solidity and chemical resistance, whereas
Roman cement of another composition yields a product of inferior quality.
Dated this 29th day of January 1891.
This
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Artificial Roman Cement.
I, CARL VON FORELL of Brunswick in the Duchy of Brunswick and Empire of
Germany, Director of the Brunswick Cement Works, do hereby declare the nature
Price 4d.1

page_text: of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
Nearly all Roman cements contain more or less uncombined lime. This lime
proceeds from the carbonate of lime contained in the raw material and which does
not enter into chemical combination owing to the comparatively low temperature at
which the cement is burned in the kiln.
Now according to this invention it has been found, that if such Roman cement
be mixed with a very finely powdered material which is rich in alumina, in such
proportions, that the "hydraulic factors" (silica, alumina and iron peroxide) stand
to the lime in the proportion of about 1 to 17 an energetic action of the caustic
lime on the hydraulic factors takes place as soon as such cement is moistened with
water. The whole mass then becomes very solid and hard after a longer or shorter
space of time.
Up to the present time it has been the custom in practice to convert aluminous
marls directly into Roman cement without the addition of mixings. The product
obtained bas a good many defects owing to the changing nature of its composition.
Above all things, it has only a small degree of solidity. According to the present
invention, an artificial Roman cement is produced which forms a thoroughly
uniform and very solid article on account of its uniform composition and owing to
certain chemical reactions taking place in its application.
The chemical process when adding aluminous materials to burned Roman cement,
can be explained in this way, namely―
The caustic lime contained in the burned Roman cement is partly slaked to
hydrate when moistened and attacks in this state the silicates of alumina in.exactly
the same manner as aqueous solutions of caustic alkalis. The hydrate of lime
combines with a portion of the "hydraulic factors" which are contained in the
silicates of alumina thereby causing a chemical compound which brings about
the higher solidity.
In the practical working of this process the following procedure should be
observed.
Marls rich in alumina are burned below the temperature of incipient vitrification
until all the carbonic acid is driven off. The mass is then pulverised to a very
fine powder by well known means. The accurate proportion of the 'lime to the
"hydraulic factors" is then determined by means of a chemical analysis and so
much of the very finely powdered silicate of alumina is added that the mixture
obtained contains lime and the "hydraulic factors" in the proportion of about
17 to 1. This exact proportion is of very great importance, especially as it has
been found that by carefully keeping to the proportion mentioned, a product can
be obtained which answers the highest expectations as to mechanical sólidity and
chemical resistance, whereas Roman cement deviating in its composition from this
approximate proportion yields a product of inferior quality.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what:1
claim is :-
-
A process for the manufacture of artificial Roman cement, in which the cement
forming materials after being heated below the temperature of incipient vitrification
till the carbonic acid is driven. off are mixed with very finely powdered aluminous
materials, for the purpose of causing an action of the lime on the silicates of
alumina, when the cement is used, that is to say, when the cement is moistened,
substantially as hereinbefore described.
Dated this 19th day of October 1891.
WM. 'P. THOMPSON & Co.,
Of Liverpool, Manchester, Nottingham, and London, Patent Agents.