IMPROVEMENTS IN THE MANUFACTURE OF CEMENTITIOUS SUBSTANCES
Year: 1863

page_text: · LETTERS PATENT to Henry Young Darracott. Scott, of Brompton Bar-
racks, near Chatham, in the County of Kent, Captain in the Royal
Engineers, for the Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
CEMENTITIOUS SUBSTANCES."
Sealed the 2nd October 1868, and dated the 28th April 1863.
PROVISIONAL SPECIFICATION left by the said Henry Young Darracott
Scott at the Office of the Commissioners of Patents, with his Petition,
on the 28th April 1863.
I, HENRY YOUNG DARRACOTT SCOTT, of Brompton Barracks, near Chatham,
in the County of Kent, Captain in the Royal Engineers, do hereby declare.
-the nature of the said Invention for "IMPROVEMENTS IN THE MANUFACTURE OF
*CEMENTITIOUS SUBSTANCES," to be as follows:-.
The object of this Invention is to produce from certain marly chalks and
limestones of analogous composition good and cheap cementitious substances
suitable for building in air or in water, and for moulding purposes.
The calcareous minerals to be used for the purposes of my Invention" are
those generally known as marly chalks, and are usually termed "soaps" by
the lime burners of Kent. These substances are generally carefully rejected
by lime burners, because they do not when calcined (as they calcine chalk)
fall abroad to a powder after being moistened. For this, reason lime con-
taining such sluggish portions does not command.a.sale-in-the-London market.
The-calcareous minerals used for the process should, however, after gentle

page_text: calcinations throw out sensible warmth when moistened, since beyond a certain
limit increase of deadness, as respects the action of water when so calcined,
shews them to be proportionately incapable of receiving that treatment which
secures the best results. Between the limits thus indicated, and which are
chiefly dependent on the proportion which the clay bears to the calcareous
ingredient all gradations in the proportions of these two constituents are admis-
sible, and the Invention consists in securing in the calcinations of the material
or the process of manufacture a graduated and partial hydration of the
calcined minerals according to such proportion, and also according to the
degree of calcination, which I vary according to circumstances.
In this manner I prepare valuable cementitious substances at a cheap rate,
and free from the dangerous, expansive, and otherwise inconvenient action
which would result if argillo-calcareous minerals of so widely different com-
positions (in respect of the relative proportions of carbonate of lime and of
clay) as occur in the chalk beds indicated were treated without previous
selection solely by the methods now in use for the preparation of cements, and
such selection would in most cases be impracticable.
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 27th October 1863.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
YOUNG DARRACOTT SCOTT, of Brompton Barracks, near Chatham, in the
County of Kent, Captain in the Royal Engineers and Brevet Major, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-eighth day of April, in the year of our
Lord One thousand eight hundred and sixty-three, in the twenty-sixth 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 MANU-

page_text: FACTURE OF CEMENTITIOUS SUBSTANCES," upon the condition (amongst others)
that 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 per-
formed, 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
same is to be performed, to be particularly described and ascertained, in and
by the following statement (that is to say) :-
"
My Invention of "Improvements in the Manufacture of Cementitious
Substances" relates to improvements in the treatment of such argillaceous
limes as do not slake to a powder when moistened, or which when so treated
fall abroad too imperfectly to be used advantageously in the preparation of
mortar without careful pulverization by mechanical means. Such limes, if
treated in the ordinary manner and without due precautions, frequently swell
after they have been made into mortar and have been employed in buildings,
and the effect of the treatment, which I claim as my Invention, is to do away
with this hurtful tendency, and enable them to be placed in the hands of the
builder in a condition requiring no slaking process, direct or indirect, in the
ordinary sense of the term to be employed by himself. Limes of the nature
.
indicated are moreover much improved by the process I apply.
In carrying out my Invention, I take lime such as I have described, and
which has been prepared by any of the ordinary methods, either. at a high or
a low temperature, and subject it to an atmosphere of steam so long as it
continues to increase in weight to an important extent. The steam entering
into the pores of the lime produces its hydration to a degree depending on its
chemical composition and the temperature at which it has been calcined. In
proportion as the per-centage of clay is greater, so the extent to which the
mineral will undergo hydration by such treatment as I employ diminishes, and
a similar diminution takes place also as the temperature at which the mineral
is calcined is increased. I have also noticed variations in respect of the water
chemically absorbed in the process, which are dependent on the relative
amounts of the constituents of the argillaceous ingredient. It is therefore
impossible to assign a definite quantity of water which would be applicable to
all cases.
It is also impossible to name a certain duration for the continuance
of the process, as this also is affected by several elements which-vary with
every sample, such as the chemical-composition of the lime, the closeness of its

page_text: texture, the form of apparatus employed, and the temperatare at which the
operation is carried out. The material, however, will not be injured by the
continuance of the process beyond what is absolutely necessary to destroy its
expansive properties, which is the object to be attained, and as some guide on
these points, I may mention that in the case of certain marly chalks, con-
taining from eighteen to twenty-four per cent. of clay, I have found that after
very gentle calcination they will increase from seven to ten per cent. in weight
by the process, and that when burned to incipient vitrification, as is done with
the mixture of chalk and clay used for Portland cement, they will absorb only
two or three per cent. of water by weight. In the case again of certain marly
chalks, containing from thirty to thirty-three per cent. of clay by weight, (which
run to a powder spontaneously on cooling if burned at a high temperature,)
I have found the limes yielded by gentle calcination absorb. from three to four
per cent. In respect of the duration of the process, I have found that marl
chalks derived from a pit in which the per-centage of clay present in the chalk
varies from fifteen to forty per cent., and which consists of alternating beds of
every intermediate composition between these limits, yield a lime which is
freed from all expansive tendency after six hours exposure to an atmo-
sphere of steam having a temperature of two hundred and twelve degrees
Fahrenheit.
In applying the steam, I confine myself to no particular temperature so long
as it is below that at which the combination of lime with water ceases to take
place, and above that at which the atmosphere of steam would be too rarified
to exert such an influence as is practically required, neither do I confine
myself to any particular form of apparatus. If much of the lime assumes a
powdery 'condition under the influence of the steam, I prefer to introduce it
into a cylindrical wrought-iron chamber having within it a sifting apparatus,
by means of which the powdered portions may be removed from the more
refractory portions, leaving these exposed to the free action of the steam. If,
however, the lime is of such a nature or has been so burned that little pul-
verization takes places from the action of the steam, the sifting apparatus may
be dispensed with.
In certain cases also when the steam does not throw the lime abroad to any
great extent, steam may be generated by the waste heat from the top of the
kiln in which the calcination of the lime is being carried on, and be led thence,
together with air heated to the temperature of boiling water to prevent
condensation to the lower end of the kiln to produce the effect required on
such portions of the charge as have sufficiently cooled down to admit of the
chemical combination of the steam with them. A separate chamber, however,

page_text: is to be preferred for the process, which can be kept at a temperature of two
hundred and twelve degrees Fahrenheit, and thus securely avoid any con
densation of water which might render the lime too moist to be pulverized
in the dry way in an ordinary grinding mill. After the completion of the
steaming operation, the grinding is proceeded with in the manner practised
with Roman or Medina cement stone after calcination, and all that is not
already in the state of powder is reduced to it.-
: In some cases instead of the above mode of operation I reduce the lime as
it comes from the kiln to pieces of the size of large walnuts, which I dip in hot
or cold water until they are saturated. For this operation I prefer boiling
water. I then allow the lime to remain in the moist condition produced by the
dipping process
for periods varying from ten or twelve hours to three or four.
days, according to convenience. It is next dried at a temperature of two
hundred and twelve degrees, employing great care not to allow the heat to
rise so high as to expel any of the water which has chemically combined with
it, and, when dry, the pulverization is completed by ordinary grinding apparatus,
such as is used to reduce. Roman and Medina cement to a fine powder. The.
drying operation is carried on as is practised with the-wet-mixtures of clay and
chalk used in the preparation of Portland cement, or in other suitable manner.,
It is to be observed that in this second method of operating my claim is not
for slaking lime by immersion, which has often been practised, but for the
combination of immersion or any other slaking process with a subsequent,
drying operation, so as to enable the slaked material to be ground to a fine dry
powder, and be sent into the market in that condition. The method has no
application with such limes as slake when moistened to a dry powder, but is of
especial value with the limes resulting from the calcination of such marl chalks.
as are termed "soap" by the lime burners of the Medway, and which are by
them rejected as far as possible on account of their imperfect mode of slaking.
These limes not only resist the slaking properties which water exercises upon
limes less, rich in clay, but when immersed in water retain, mechanically mixed,
moisture very tenaciously, so that a drying process is essentially necessary to
reduce them to powder by an ordinary cement mill.
It is to be observed further that though in the above description of my
process I have applied the term "limes" to the minerals which I consider
suitable for it, many of the calcareous substances included within the range
they take as respects the proportion of their argillaceous constituents may by
a properly regulated calcination be brought to that condition in which they
would be termed cements, requiring no slacking process_to_be-employed upon
them before using them.in-buildings.”

page_text: When the beds of limestone are of such uniform composition or of such
nature as can be depended upon for the production of cements, such as the
Roman, Medina, Mulgrave, and other cements, my process has no useful
application. Such cements, if made into mortar and used at once, should
have no dangerous expansive action, and my process is only applicable when
such action is to be feared. It may consequently be employed with advantage
in cases in which artificial preparations of the nature of Portland cement
exhibit this dangerous property after calcination, for these nearly resemble in
composition and in action "soaps" or marl chalks containing between eighteen
and twenty-four per cent. by weight of clay.
Having now described my Invention, and having explained the means of
carrying the same into effect (though I do not mean to confine myself to the
foregoing methods of attaining the object of the Invention so far as the
mechanical contrivances are concerned), I wish it to be understood that
I claim as the Invention secured to me by Letters Patent, as aforesaid, the
mode herein set forth of preparing cementitious substances from argillo-
calcareous minerals of the nature specified by the aid of partial hydration,
leaving the prepared substances dry and fit to pass through a mill so as to
complete their disintegration as a dry powder; I claim for effecting this in two
ways,―
First, by subjecting the calcined mineral to the action of steam purposely
applied, as above explained.
Secondly, by immersing the calcined mineral in water, or otherwise wetting
it with water, and subsequently driving off the surplus moisture, or that which
has not chemically combined with it, by means of heat purposely applied, and
over and above that which is generated by the action of the water on the
material.
In witness whereof, I, the said Henry Young Darracott Scott, have here-
unto set my hand and seal, the Twenty-sixth day of October, in the
year of our Lord One thousand eight hundred and sixty-three.