Improvements in the Method of Manufacturing Artificial Stone and Concrete.
Year: 1898

page_text: Date of Application, 6th Apr., 1898
Complete Specification Left, 4th July, 1898-Accepted, 20th Aug., 1898
PROVISIONAL SPECIFICATION.
Improvements in the Method of Manufacturing Artificial Stone and
Concrete.
We, LEWIS PETER FORD, Gentleman, of 72, Bishopsgate Street Within, and
THOMAS WALTER BARBER, Engineer, of 17 and 18, Tothill Street, Westminster,
both in the County of London, do hereby declare the nature of this invention to
be as follows:-
The invention relates to improvements in the method of manufacturing artificial
stone and concrete, and has for its object the removal of the air from the material
before it is slaked, in the moulds, the facilitating of the slaking process, and the
acceleration of the drying and indurating of the stone when made. It also
embodies improvements in the method of manufacturing colored and parti-colored
artificial stone, and in the method of obtaining rapid induration by the admixture
of hardening chemicals.
In carrying our invention into effect we utilize a closed vessel or chamber capable
of withstanding considerable pressure and of suitable form for the reception of
the moulds into which the dry material is placed.
The moulds, when filled, are placed within the said vessel or chamber, which is
then hermetically closed. The air is exhausted from the vessel or chamber, and
consequently from the material in the moulds, by means of an air pump attached
to the vessel, or by any other suitable means. Water, preferably hot, is then
admitted into the vessel or chamber for a certain time, after which steam is
admitted to the vessel and the water is allowed to escape.
The lime in the moulds is slaked, partly by the water first introduced, and partly
by the steam. The temperature of the chamber is maintained at a suitable level
by means of a steam coil or jacket, or in any other convenient manner.
The drying of the stone is effected partly by the introduction of dry steam, and
then by exhausting the vessel, in the manner above described, till the moulds
are ready for removal. This latter operation may be effected in a separato
chamber, and the stone or concrete may be removed from the moulds to accelerate
the drying process.
We have found by experiments that by first slaking the materials with hot water,
and then completing the process by steam, superior results are obtained, and a
considerable economy in time is effected, as compared with the system of slaking
entirely either by hot water or steam.
For small blocks of artificial stone we prefer to subject the dry mixed materials
in the moulds to a vacuum for about an hour, then to the action of hot water,
under a pressure of three to four atmospheres, for about the same period, and
then, after expelling the water, to the action of steam at a pressure of four to five
atmospheres for about five hours, after which we shut off the steam and again
create a vacuum, maintaining the closed vessel or chamber at a suitable tempera-
ture, by any convenient means, throughout the process and until the artificial
stone is dry. For very large blocks rather longer periods are necessary.

page_text: The materials employed in the manufacture of the artificial stone are lime and
sand. We are aware that these materials have previously been used, and we make
no claim in connection therewith.
In order to increase the hardness of the artificial stone or concrete, and to
accelerate the process of induration, we combine with the lime and sand, a certain
proportion of a- dry powdered alkaline silicate, or other chemical compound
possessing similar properties. We are aware that artificial stone, after manu-
facture, has been treated superficially with such chemical compounds in order to
cause induration, but it has been found that blocks so treated only become
indurated upon the surface, even after a considerable lapse of time. Our process
has the advantage of simplicity of manipulation and greater accuracy and
uniformity of results and takes place concurrently with the manufacture of the
stone.
By our process we are enabled to produce a homogenous artificial stone of equal
hardness throughout, having no air cracks or similar defects, in much less time
than by the present methods, and the stone, when removed from the moulds, is
dry and hard and is ready for use.
To color the stone we use dry powdered pigments mixed in with the other
ingredients. To make a parti- or multi-colored stone we first make blocks of
stone by our process of the various colors required. These blocks are immediately
broken up into small pieces of the required dimensions and then mixed in the right
proportions and, together with a fresh quantity of lime and sand or lime only
(colored or not), are placed in the moulds and made into solid blocks in the same
manner as herein before described.
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HARRIS & MILLS,
23, Southampton Buildings, London, W.C., Agents.
COMPLETE SPECIFICATION.
Improvements in the Method of Manufacturing Artificial Stone and
Concrete.
We, LEWIS PETER FORD, of 72, Bishopsgate Street Within, in the City of
London, Gentleman, and THOMAS WALTER BARBER, of 17 and 18, Tothill Street,
Westminster, in the County of London, Engineer, do hereby declare the nature
of this invention, and in what manner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement:-
The invention relates to improvements in the method of manufacturing artificial
stone and concrete, and has for its object the removal of the air from the material
before it is slacked, in the moulds, the facilitating of the slacking process, and the
acceleration of the drying and indurating of the stone when made.
It also embodies improvements in the method of manufacturing colored and
parti-colored artificial stones, and in the method of obtaining rapid induration
by the admixture of hardening chemicals.
In carrying the invention into effect a closed vessel or chamber capable of
withstanding considerable pressure and of suitable form for the reception of the
moulds is utilized, into which the dry material is placed.
The moulds, when filled, and the materials sufficiently rammed, are placed
within the said vessel or chamber, which is then hermetically closed.
The air is exhausted from the vessel or chamber, and consequently from the
material in the moulds, by means of an air pump attached to the vessel, or by any
other suitable means. This facilitates the entry of the slacking water and creates
a condition favorable for the production of silicate of lime.

page_text: Hot water under pressure is then admitted into the vessel or chamber for a
short period, say from about one to two hours, which perfectly hydrates the lime
and no more, after which steam under high pressure, is admitted to the vessel
and the water is allowed to escape.
This accelerates the formation of the silicate and maintains a suitable tempera-
ture without either denuding the mass of any of the water of hydration or drown-
ing it with surplus moisture, maintaining in fact, an ideal state of equilibrium.
The temperature of the chamber is maintained at a suitable level by means of
a steam coil or jacket, or in any other convenient manner.
The drying of the stone is effected by exhausting the vessel or chamber in the
manner above described till the moulds are ready for removal.
This latter operation may be effected in a separate chamber and the stone or
concrete may be removed from the moulds to accelerate the drying process.
It has been found by experiments that, by first slacking the materials with
hot water and then completing the process by steam and allowing the water to
escape, superior results are obtained and a considerable economy in time is
effected, as compared with the system of slacking entirely either by hot water or
steam, or by hot water followed by an injection of steam into the water.
For small blocks of artificial stone it is preferable to subject the dry mixed
materials in the moulds to a vacuum for about an hour, then to the action of hot
water under a pressure of three or four atmospheres for about the same period,
and then, after expelling the water, to the action of steam at a pressure of from
about four to five atmospheres for about five hours, after which the steam is shut
off and a vacuum again created, the closed vessel or chamber being maintained
at a suitable temperature by any convenient means throughout the process and
until the artificial stone is dry. For very large blocks rather longer periods are
necessary.
C
The materials employed in the manufacture of artificial stone are lime and
sand.
In order to increase the hardness of the artificial stone or concrete, and to
accelerate the process of induration, a certain proportion, say from 1 to 5 per cent.
of a dry powdered alkaline silicate or other chemical compound possessing
similar properties, is sometimes combined with the lime and sand.
It is known that artificial stone, after manufacture, has been treated superficially
with such chemical compounds, in order to cause induration, but it has been found
that blocks so treated only become indurated upon the surface even after a con-
siderable lapse of time.
The improved process has the advantage of simplicity of manipulation and
greater accuracy and uniformity of results, and the induration takes place con-
currently with the manufacture of the stone.
By this improved process, a homogeneous artificial stone of equal hardness
throughout, having no air cracks or similar defects, can be produced in much less
time than by the present methods, and the stone when removed from the moulds
is dry and hard and is ready for use.
To colour the stone, dry powdered pigments are used, mixed in with the other
ingredients.
To make a parti or multi colored stone, blocks of stone are first made by the
improved process of the various colours required. These blocks are thereupon (i.e.
before complete induration) broken up into small pieces of the required dimensions
and then mixed in the right proportions and, together with a fresh quantity of
lime and sand, or lime only (colored or not), are placed in the moulds and made
into solid blocks in the same manner as hereinbefore described.
It is highly essential for the production of a good stone, that the hydration be
be perfectly carried out. The induration of the lime, the most important period in
the formation of the mass, is delayed seriously when the materials are over
hydrated, and the enfeebling of the lime means a weaker product.

page_text: Having thus particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, it is remarked that no
novelty is claimed in the use of sand and lime for making artificial stone, nor the
use of alkaline silicate for accelerating induration, nor the use of moulds and
air-tight chambers, nor the use of an air pump, nor the use of water only, or
steam only, or water with steam injected therein, for slacking, but what is
claimed is:
1. The manufacture of artificial stone or concrete by the following process or
combination of steps:-1, placing the dry materials in a strong mould not hermeti-
cally sealed, 2, placing said moulds containing the materials in a vessel or chamber
capable of being closed hermetically and maintained at a suitable temperature,
3, creating a vacuum in said vessel or chamber, 4, introducing hot water under
pressure, 5, introducing steam under pressure and allowing the water to escape,
6, creating a vacuum in the vessel or chamber containing the moulds to accelerate
the drying operation, substantially as herein set forth.
2. The manufacture of artificial stone or concrete by the following process or
combination of steps:-1, placing the dry materials in a strong mould not
hermetically sealed, 2, placing said moulds containing the materials in a vessel or
chamber capable of being hermetically closed and maintained at a suitable tempera-
ture, 3, creating a vacuum in said vessel or chamber, 4, introducing hot water
under pressure, 5, introducing steam under pressure and allowing the water to
escape, 6, removing the moulds from the first vessel or chamber and placing the
blocks of stone therefrom in a second chambe", 7, creating a vacuum in said
second chamber maintained at a suitable temperature, substantially as herein
described.
3. The manufacture of parti or multi colored stone or concrete as follows:-
1, making blocks of stone or concrete of individual colors by the process herein-
before described, (or fragments of natural colored stone may be used), 2, breaking
these blocks before complete induration into fragments of suitable shape and size;
3, mixing the fragments in the desired proportions: 4, adding a further propor-
tion of lime and sand or lime only (colored or not colored), and then 5, subjecting
the mixture to the process of manufacture as already claimed, substantially as
herein described.
4. In the manufacture of artificial stone or concrete, the employment first, for a
short period, of hot water under pressure in a closed chamber, and, after the
removal of the water, of steam under pressure for a longer period, to slack the lime
in the moulds, substantially as herein described.
5. In connection with a process for making artificial stone such as is claimed in
the last preceding claim, the use of a proportion of dry alkaline silicate with the
quick lime, substantially as described."
Dated this 4th day of July 1898.
HARRIS & MILLS,
23, Southampton Buildings, London, W.C., Agents.