IMPROVEMENTS IN THE MANUFACTURE OF CERTAIN CEMENTS
Year: 1854

page_text: LETTERS PATENT to Emile Dupont, of Boulogne-sur-Mer, in the Empire
of France, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
CERTAIN CEMENTS."
Sealed the 6th October 1854, and dated the 6th April 1854.
PROVISIONAL SPECIFICATION left by the said Emile Dupont at the
Office of the Commissioners of Patents, with his Petition, on the 6th
April 1854.
I, EMILE DUPONT, of Boulogne-sur-Mer, in the Empire, of France, do
hereby declare the nature of my said Invention for "IMPROVEMENTS IN THE
MANUFACTURE OF CERTAIN CEMENTS" to be as follows (that is to say):-
My improvements having reference to the manufacture of a hydraulic
cement, to be called the natural Portland cement of Boulogne-sur-Mer,
analogous to the artificial English Portland cement, are carried into effect
in the following manner:-The manufacturer selects in different soils, but
especially in the lower strata of the chalk formation, marls or limestones of a
homogeneous structure, containing from nineteen to twenty-two per cent. of
clay. The said clay should contain as little sand as possible, and in no case
more than a twentieth part of its weight. The proportion of silica and alumina
which compose it may vary without any disadvantage. In localities where
limestones are not found containing the exact quantity of clay which is
required, they may be replaced by employing various marls or calcareous
earths with different clayey bases, and which when united would include the

page_text: requisite proportions. Each of these substances being already combined with
a considerable quantity of clay, their simple juxtaposition and reduction by
trituration to a pasty consistence under vertical mills is sufficient to effect their
intimate mixing by a single operation, and without its being necessary to
reduce them to a liquid state, and proceed upon them by decantation, as is
indispensable in the artificial products obtained from different and distinct
elements, like chalk and clay. These limestones or marles may be baked
in ordinary lime kilns, or in ovens for pottery. They must be exposed for
a period of several hours to a good white heat, obtained slowly and progres-
sively. This temperature is considerably higher than that which is necessary
for the burning of lime, and much more of ordinary cements.
In this manner
is obtained a product having the following characteristics :-The baked matter
is sensibly contracted and shrunk within itself without having lost its primitive
form; it is, as it were, granular, and has the appearance of fritted lime; it has
taken a greenish or blackish grey colour, and its fracture is rough or corned.
It is indispensable to remove by a careful picking all the parts which shall
not have attained this degree of baking, inasmuch as their presence in the
mass would infallibly deteriorate its quality. The mass is pulverized by
the ordinary methods, and formed into a natural cement of an iron grey
colour, of which the quality, being always equal, yields in no respect to that
of the best artificial English Portland cement, composed by intimate mixtures
of clay and lime, obtained by long and expensive processes, in proportion
to the perfection of which the results differ considerably. It would be
impossible to depart, even to a slight amount, from the whole of the process
that has been detailed without altering the nature of the product. Thus,
by the simple ordinary bakings, the best chosen limestones would only furnish
an hydraulic lime. By the baking at a high temperature the limestones
containing least clay would give a lime that could be slacked; those which
contained more would furnish either a burned cement, baking much more
slowly, and of very inferior quality, the fracture of which, like that of clay
baked into gritstone, indicates an incipient softening, or else an inert matter,
having undergone a pasty fusion or vitrefaction. I claim the method of
producing a cement, which I call the natural Portland cement of Boulogne-
sur-Mer, by the employment of the substances and the processes here detailed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Emile Dupont in the Great Seal Patent Office on the
6th October 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, EMILE
DUPONT, of Boulogne-sur-Mer, in the Empire of France, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixth day of April, in the year of our Lord
One thousand eight hundred and fifty-four, in the sixteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Emile Dupont, Her special licence that I, the said Emile
Dupont, my executors, administrators, and assigns, or such others as I,
the said Emile Dupont, my executors, administrators, and assigns, should
at any time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for "IM-
PROVEMENTS IN THE MANUFACTURE OF CERTAIN CEMENTS," upon the condition,
amongst others, that I, the said Emile Dupont, by an instrument in writing
under my hand and seal, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within six
calendar months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Emile Dupont, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, that is to say:-
My said improvements have reference to the manufacture of a certain
cement, which I call Boulogne-sur-Mer natural Portland cement, the same
being of analogous composition to the English artificial Portland cement, of
which lime and clay are the constituents; but whereas the said artificial
Portland cement is formed by mixing suitable quantities of chalk and clay,
which require a very long and expensive treatment to obtain the proper
amalgamation of the lime and clay elements by the reduction to a liquid state,
and the decantation of the materials: now my said natural cement is formed
from a marl or limestone, or from a mixture of marls or limestones, naturally
containing a due proportion of the requisite ingredients in a condition to be
readily united by comparatively simple processes. For this purpose I select in
various soils, but especially in the lower strata of the chalk formation, lime-

page_text: stones or marls of a homogeneous texture, containing from nineteen to twenty-
two per cent. of clay. This clay ought to contain the smallest possible amount
of sand, and in no case more than a twentieth part of its weight. The propor-
tions of silica and alumina which enters into its composition may vary without
detriment. In localities in which limestones are not found containing the
exact proportion of clay, their place may be supplied by employing a mixture
of limestones or marls, having different clayey bases, which united together
will contain the requisite proportions. Each of these matters being already
combined with a considerable proportion of clay, their simple juxtaposition
and trituration with water, to reduce them to, a pasty state, is sufficient to
produce a perfect amalgamation of their constituent elements by a simple
process, without the operations above alluded to, as required to produce
artificial Portland cement. The above trituration may be performed in
vertical mills; but I prefer, in cases where mixed marls or limestones arc
employed, to subject them to the action of horizontal mills, similar to those
employed in grinding corn, adding enough water to facilitate the exit of the
materials from the mill, and obtain a paste sufficiently firm to form immediately
into bricks, which must be dried preparatory to the baking. The said
horizontal mills ought also to be employed in some cases where the cement is
to be made from single marls or limestones, when these are of certain kinds
which furnish upon analysis the due proportions of lime & clay, but from
not having in their texture the requisite homogeneity, fail to produce a cement
when triturated in the ordinary vertical mills. The paste obtained as above
may be baked in limekilns or in pottery kilns. It should be exposed during
several hours to a good white heat, obtained slowly and progressively, the
temperature being considerably higher than that required for lime, and still
more for ordinary cements. By this means a product is obtained which
presents the following characteristics:-The baked matter is sensibly shrunk
without losing its primitive form; it is, as it were, corned, and presents an
appearance like that of fritted lime; it has acquired a blackish or greenish
grey tinge, and its fracture is granular. From this product it is indispensable
to remove by a careful picking all the parts which are not sufficiently baked,
& the presence of which in the mass would infallibly make the quality
deteriorate. The bricks. or baked masses are then pulverised by the ordinary
methods & converted into a natural cement, which is of iron grey color,
and of which the quality is always uniform and equal to that of the best
English artificial cement, while the processes by which it is obtained are
considerably more economical.
My improvements having reference, secondly, to the manufacture of artificial

page_text: Portland cement, or that which is formed from chalk and clay separately
obtained, consists in applying to the trituration of the materials for the said
cement the same horizontal mills which I employ in producing my natural
Portland cement, in place of the vertical mills hitherto employed, and of
which the operation is less effectual.
Having now fully described the nature of my said Invention, and the
manner in which the same is to be carried out, I would have it clearly under-
stood that I do not by any means confine myself to the precise details herein-
before described, as the same might be varied without departing from the
general principle of these my said improvements; but that which I do claim
as new and of my said Invention is,―
Firstly, the formation of a cement, which I call the Boulogne-sur-Mer
natural Portland cement, obtained from natural marls or limestones, employed
singly or in combination.
Secondly, the employment of horizontal mills for grinding the materials
employed in forming the said cement in those cases where it is obtained from
a combination of marls or limestones, or where obtained from single marls
or limestones of a texture not sufficiently homogeneous.
Thirdly, the employment of the said horizontal mills in the manufacture of
the ordinary artificial Portland cement from chalk & clay separately obtained.
In witness whereof, I, the said Emile Dupont, have hereunto set my hand
and seal, this First day of October, in the year of our Lord 1854.
EMILE DUPONT. (L.S.)