IMPROVEMENTS IN THE MANUFACTURE OF CEMENT
Year: 1864

page_text: LETTERS PATENT to Henry Young Darracott Scott, of Chatham, in the
County of Kent, Lieutenant-Colonel in the Royal Engineers, for the
Invention of "IMPROVEMENTS IN THE MANUFACTURE OF CEMENT."
Sealed the 21st June 1864, and dated the 17th February 1864.
PROVISIONAL SPECIFICATION left by the said Henry Young Darracott
Scott at the Office of the Commissioners of Patents, with his Petition,
on the 17th February 1864.
I, HENRY YOUNG DARRACOTT SCOTT, of Chatham, in the County of Kent
Lieutenant-Colonel in the Royal Engineers, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF CEMENT," to be
as follows:-
My Invention of "Improvements in the Manufacture of Cement consists in
combining certain chemical earthy or natural substances with quick lime, and
operating upon the combination in such a manner as to produce a compound,
which when used shall form a hard and durable cement.
In carrying out my Invention I take any convenient quantity of quicklime,
and add thereto, say, five per cent., more or less, of any suitable and cheap
sulphate, such as sulphate of lime or sulphate of iron, the proportion of sulphate
to be added depending in a measure upon the quantity of argillaceous matter
contained in the lime. These substances may be mixed together in a pulverized
state, or they may be mixed in lump, and then ground together so as to
intimately amalgamate them] The lime is then submitted to the action of

page_text: steam for the purpose of slightly hydrating it. This operation may be effected
either before or after the addition of the sulphate, and in some cases even while
the lime is still in lump. Any convenient way of hydrating the lime by means
of steam may be employed, but I prefer to use an apparatus which may be
described as consisting of a pug mill or vertical chamber in which is mounted
an upright shaft provided with hollow horizontal arms, which are perforated so
as to allow of the emission of steam therefrom as they move round. It will be
evident that by the use of an apparatus of this kind the amount of hydration
of the lime may be regulated with accuracy and kept entirely under control.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Henry Young Darracott Scott in the Great Seal Patent Office
on the 17th August 1864.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
YOUNG DARRACOTT SCOTT, of Chatham, in the County of Kent, Lieutenant-
Colonel in the Royal Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Seventeenth day of February, in the year of our
Lord One thousand eight hundred and sixty-four, in the twenty-seventh year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Henry Young Darracott Scott, Her special license that I, the said
Henry Young Darracott Scott, my executors, administrators, and assigns,
or such others as I, the said Henry Young Darracott Scott, 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 "IMPROVEMENTS IN THE MANUFACTURE OF CEMENT,"
upon the condition (amongst others) that I, the said Henry Young Darracott
Scott, 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 Henry Young Darracott Scott, do
hereby declare the nature of my said Invention, and in what manner the

page_text: same is to be performed, to be particularly described and ascertained in and.
by the following statement (that is to say):-
My Invention for "Improvements in the Manufacture of Cements relates
to improvements in the mode of converting calcareous substances, ordinarily
termed limes, into what would in common language be called cements (that is
to say) into substances which when used for mortar or for plaster enter into
chemical combination with water in the act of setting, and do not previous to
setting exhibit that violent expansive action which occurs generally when
fresh quicklime in its ordinary condition is moistened. This violent expansive
action of quicklime, when acted upon by water, which it is the object of this
Invention to control, is best subdued by the union of three distinct agencies,
for none of which however, taken independently, is any claim of novelty here
advanced.
First, it is desirable that the lime employed should be of argillaceous
character, and that the argillaceous constitutents (meaning thereby the silex,.
the iron, alumina, and other bases not of calcareous or magnesian nature)
should amount to a quantity forming from fifteen to thirty per cent. of the
whole.
of
Second, it is of advantage to reduce the chemical avidity which ordinary
quicklime exhibits for water, by bringing about its partial hydration by means.
vapour of water or steam. I prefer allowing the hydration to proceed to
the extent of adding from two to five per cent. to the weight of the lime, more
or less, according to its nature, the more argillaceous limes requiring the
smaller of these per centages, and the less argillaceous limes the greater.
Third, together with the agencies above named, the presence of sulphuric
acid in chemical combination with some substance not injurious to the manu-
facture is essential. The proportion of sulphuric acid present may vary from
one to four per cent. according to the nature of the lime operated upon, and
here again the more argillaceous limes require the smaller proportion of the
ingredient introduced, and the less argillaceous the greater measure of it.
Lines of intermediate composition between the limits named as respects
argillaceous constituents, require intermediate proportions both of hydration
and of sulphuric acid, and it is of great importance that these controlling
agencies should be intimately and equably disseminated through the lime. It
is manifest that a process dependent on combinations of this nature admits of
many variations in the modus operandi, without departing from what consti-
tutes the Invention, viz., in combining the action of sulphate of lime (either
directly added, or resulting from the addition of some compounds, the elements
of which under the circumstances of the addition and the use to which the

page_text: material is put necessarily lead to the formation of sulphate of lime) with
such partial hydration by means of aqueous vapour as I have indicated. I do
not, therefore, confine myself to the precise methods herein-after explained, but
which I consider the best under the circumstances stated, nor yet do I
confine myself to the exact proportions named of any of the controlling
agencies employed, for as one of them is present in larger quantity, the others
may be diminished within certain limits without serious deterioration to the
material manufactured.
Having explained the principle upon which the Invention is based, I will
now describe the methods of operating which I find to be on the whole the
best with the generality of limes, and I will point out the modifications of
this general method of procedure which I have ascertained to be most
suitable for what I consider to be the three descriptions of hydraulic lime
best known in this country. For the general method I take quicklime
properly and tenderly burned, and roughly mix with it in lump from three to
six per cent. of gypsum, or a somewhat less proportion of plaster of Paris
according to the circumstances of the case as respects the argillaceous
constituent of the lime. I pass this mixture under crushers, such as are
frequently used in mills for grinding portland cement, and thence through a
grinding mill constructed on the principle of the ordinary flour mill. As the
pulverized material leaves the stones, I pass it into an apparatus somewha
resembling an ordinary pug mill in external form. In the conical chamber
or case of this mill is mounted an upright hollow shaft, provided with hollow
horizontal arms which are perforated so as to allow of the emission of steam
as they move round. The apparatus must be kept sufficiently full of the
pulverised mixture to ensure its upper horizontal arms being covered, and
the rate of the emission of the steamed mixture at the bottom must be so
regulated that the proper amount of hydration may be secured in its passage
through the pug mill. The amount of this hydration must, as has been stated,
be regulated by the character of the lime, and I find it convenient that the
apparatus should be about three feet in diameter, and three feet deep. The
steam may be conveyed to the upright hollow shaft from any convenient
steam boiler, and I find it best to use the steam with a pressure just sufficient
to keep the perforations in the revolving arms clear from lime. The hydrous
material as it is discharged through an opening at the bottom of the pug mill
will be found to have somewhat increased in bulk, to be somewhat lighter in
color, and to have a greatly diminished tendency to combine rapidly and
violently with water. As soon as cool the material is ready for use, and has
only to be made into mortar in the ordinary manner.

page_text: In dealing with the grey chalk lime of the London market, which slakes
with great violence when in its ordinary condition, I prefer to combine the
sulphate of lime with the quicklime in a more indirect manner through
the intervention of sulphurous acid, thus effecting the combination of the
sulphate with the lime by converting a portion of the quick lime itself into
the controlling ingredient or into its vehicle. The best method of effecting
this conversion for the purpose here required is to burn sulphur beneath it, or
in the same chamber with it, the lime being in lump and in a heated state,
sufficient air being admitted to carry on the combustion.
This method was described in a Patent granted to me on the Seventeenth
of April One thousand eight hundred and fifty-six (No. 915), and the
improvements resulting from the present Invention of a combination of the
action of the sulphate of lime as thus formed with partial hydration, consist in
greater cheapness of production arising from a saving of sulphur and a greater
certainty of action from the control exerted by the partial hydration over the
ready affinity of the compound for water. This modification of the first
described process I sometimes combine with that process for the sake of a
money saving, which in some cases may be found to result therefrom.
The direct addition of sulphuric acid to the quicklime, so as to convert a
portion of that lime into a sulphate, will evidently produce results similar in
kind to those which are produced by adding gypsum or sulphate of lime to the
quicklime, but since I do not find this method succeed so perfectly as those I
have or shall describe it is unnecessary to enter into the details of carrying the
plan into execution.
I
may
further vary the above process, and that for all limes, by passing the
vapour of water existing in the atmosphere through a chamber containing the
lime in lump arranged in any convenient manner, but this method cannot be
wholly followed with advantage to the material manufactured since all parts
of the lime are not thus equally affected, and exposure to the air injures the
setting properties of the lime through the carbonic acid gas which it contains.
Such exposure however carried to an extent only that will not sensibly affect
the quality of the lime may be advantageously used in combination with the
aqueous vapour obtained from the steaming apparatus above described in con-
verting grey lime containing small proportions of argillaceous constituents
into cement.
In dealing with certain limes of the class of the hydraulic limes from
the neighborhood of Halkin and Holywell, North Wales, I vary the
first described method by making use of a very soluble sulphate as the vehicle
of the sulphuric acid, such as sulphate of iron, or on account of its freedom

page_text: from color sulphate of magnesia, or I may use sulphuric acid of commerce
mixed with a small quantity of water. In this case I dispense with the
steaming apparatus, and proceed as follows to secure the proper hydration of
the lime:-I first break the lime into small lumps of the size of a walnut, and
over this I sprinkle from a rose head, or in any convenient manner, the
sulphate to be employed dissolved in as small a quantity of water as
possible. The action of the sulphate solution (or diluted sulphuric acid when
such is employed) generates with the lime considerable heat, and this vaporises
that portion of the water which does not at once pass into chemical combina-
tion, and the aqueous vapour thus formed, if it be allowed time to act (by
wholly or partially obviating its escape as may be required) will effect that
which in the first described method of carrying out the process is brought
about in the steam chamber with revolving arms. When the whole of the
water of the solution has either entered into chemical combination as water,
or having passed into the condition of steam has entered into combination with
the lime from that condition or escaped altogether (and this will generally be
the case with such limes as I have named in three hours) I grind the lime to
a powder, in the ordinary manner and the mixture is ready for use.
Sometimes again I find it convenient to avail myself of limes which after
calcination are found to contain notable quantities of sulphates derived from
elements existing in the limestone. Beds yielding limes of this nature are
sometimes met with in quarries of lias limestone, and by grinding. the limes
derived from them with other limes of ordinary composition from the same,
or from different quarries, in such proportions as to secure the proper per
centage of sulphate in the mixture, no other means of adding sulphuric acid
need be resorted to, and it is only necessary to pass the pulverised mixture
through the steaming apparatus above described in order to complete the
process and fit the material for the market.
As a further indication for deciding on the sulphates which it is best to
have recourse to in the absence of those which I have above described as the
most suitable for the cases named, I will add that I find sulphate of lime, either
as gypsum or plaster of Paris, suitable in all cases, sulphate of magnesia or
sulphate of zinc may also be used, but from the difficulty of mixing them as
solids it is of advantage with these salts to resort to the method of adding
them in a state of solution. Of other sulphates, I find those which are
insoluble to be always unsuitable and also sulphate of copper. Sulphate of
iron is unsuitable for grey chalk lime, and is also an unsuitable sulphate to
use with lias lime which already contains generally a considerable pro-
portion of iron. On the other band sulphate of iron gives the best results

page_text: with Halkin hydraulic limes which naturally contain very little iron. Sulphate
of alumina has a very feeble action comparatively, and sulphates of the alkalies
or combinations of these sulphates with alumina are also unsuitable in the
generality of cases, though they will answer with Halkin hydraulic limes
and generally with limes containing a very large proportion of clay, sulphites
of manganese and nickel may be classed in their action with sulphate of
zinc.
Having now set forth the nature of my Invention of "Improvements in the
Manufacture of Cements," and explained the most suitable methods of carrying
the same into effect according to the nature of the limes employed, I wish it
to be understood that under the above recited Letters Patent I claim, obtaining
a hydrous compound of quicklime and sulphate of lime in the manner and
for the purpose above described.
In witness whereof, I, the said Henry Young Darracott Scott, have
hereunto set my hand and seal, the Sixteenth day of August, in
the year of our Lord One thousand eight hundred and sixty-four.
Witness,
W. D. MARSH,
Capt. R. Eng.
Chatham.
HENRY Y. D. SCOTT. (L.B.)