Improvements in the Manufacture of Cement.
Year: 1895

page_text: Date of Application, 8th June, 1895
Complete Specification Left, 28th Mar., 1896-Accepted, 2nd May, 1896
Date of Application on an
Complete Specification Left, 28th Mar., 1896-Accepted, 2nd May, 1896
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Cement.
I WILLIAM SLARK of Ashley House Caterham Valley Surrey and 6 Serle
Street Lincoln's Inn in the County of London Solicitor do hereby declare the
nature of this invention to be as follows:-
This invention relates to a process for manufacturing a cement which possesses
high hydraulic & binding properties.
Ordinary Roman cement stone is powdered to a greater or less degree depending
upon its quality. This powdered cement stone is added to a quantity of clay and
chalk which have been previously mixed. The proportions of these may vary
within certain limits depending upon the particular composition of each.
The mixture is then placed in a furnace and raised to a high temperature.
the whole has been thoroughly burnt it is ground in the usual manner.
By this process a cement is obtained which possesses very high binding and
be manufactured at a
hydraulic properties, while at the same time it can
comparatively small cost.
Dated this 8th day of June 1895
After
Improvements in the παπαιαν
I WILLIAM SLARK of Ashley House Caterham Valley in the County of
Surrey Solicitor, do hereby declare the nature 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 :-
The invention relates to a process for manufacturing a cement which possesses
high hydraulic and binding properties.
The best Portland cements have heretofore been made by mixing together clay
and chalk in such proportions that the lime is in the proportion of 1.7 to 1 of
hydraulic factors.
The chalk provides the lime and the clay the hydraulic factors which are silica,
alumina and ferric oxides.
"
1S
In manufacturing Portland cement according to the usual process the mixture of
clay and chalk is washed in a mill with sufficient water to reduce the mixture
to a fine condition when it is technically known as "slurry." This "slurry'
afterwards dried to deprive it of its added water and the mixture which up to this
time is a mere mechanical mixture is then fused in a kiln and reduced to a clinker.
This clinker when ground is the ordinary Portland cement of commerce.
Roman cement as heretofore manufactured is made from a natural stone known
רנס....מ

page_text: as Roman cement stone which is an indurated ferruginous marl. The stone is
broken up into pieces placed in a kiln and subjected to a sufficient heat to drive off
the carbonic acid gas and water of crystalization. The calcined product when
ground is Roman cement. Roman cement contains in ordinary samples lime and
hydraulic factors in about the proportions of 1.5 to 1.
It will be apparent that in Roman cement the hydraulic factors are present in
larger proportions than in Portland cement and the Roman cement does not possess
hydraulic or binding properties at all to be compared with the properties of the
best Portland cement.
According to my invention I prepare a cement which possesses very high binding
and hydraulic properties.
I prepare a "slurry" of clay and chalk in a similar manner to that adopted for
the preparation of Portland cement. The proportious of clay and chalk differ
however from those used for Portland cement as the "slurry " contains not only
sufficient chalk to combine with the clay to produce Portland cement but also
sufficient chalk to combine with the Roman cement stone which is to be subsequently
added so that the lime and hydraulic factors present in the whole mixture will be
in the proportions of about 17 to 1.
I dry the slurry and load it into the usual cement kilns together with the broken
Roman cement stone.
I find that I can with advantage mix together the slurry and the Roman cement
stone in any proportions from about half and half to 75 per cent. slurry and 25 per
cent. Roman cement stone the breaking strain of the cement increasing as the
proportion of slurry rises though at the same time the special qualities of the
cement are not lost. In preparing my cement when I use equal quantities of
slurry and Roman cement stone I generally load the kiln either in alternate layers
or mixed together but when I use only about 25 per cent. of Roman cement stone
I usually find it effects a saving of fuel to burn off the slurry first in the kiln and
then to load the Roman cement stone into the kiln when without further firing
there will be sufficient heat to burn off the Roman cement stone.
The calcining and fusing is carried out in the same manner as in the preparation
of Portland cement but I find that it is sufficient and gives a cement of excellent
quality if I burn the mixture until a bushel of the cement weighs about 112 lbs.
After burning the mixture I grind up the resulting clinker preferably to such a
degree of fineness that the cement will pass through a sieve having 2500 holes to
the square inch but I do not limit myself to any particular degree of fineness.
The cement is then ready for use.
I find that by preparing a cement in this manner I effect a considerable saving
in fuel and obtain a larger percentage of cement than by the ordinary Portland
cement process and that the cement produced according to my invention is cheaper
possesses high hydraulic and binding properties grinds up more easily and that
the breaking strain of the cement produced from equivalent mixtures of materials
in different kilns is much more even than is the case with ordinary Portland
cement.
It is of course obvious that it will not be departing from the nature of my
invention if instead of burning together Roman cement stone and a mixture o
chalk and clay as above described 1 burn together in the same manner Romar
'cement stone and such a quantity of chalk as will make the lime and hydraulic
factors in the proportions of about 17 to 1 but I prefer to adopt the process firs
above described.
It will not also be a departure from my invention if in lieu of Roman cemen
stone other calcareous stones of similar composition are used.
It will of course be understood that the proportions of 1.7 lime to 1 of hydrauli
factors produces in my opinion the best cement but my invention will not b
departed from if the proportions given are slightly varied."

page_text: 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 I
claim is :-
The process for manufacturing a cement having high hydraulic and binding
properties from Roman cement stone substantially as hereinbefore described.
Dated this Twenty-eighth day of March 1896.
ILLIAM SLARK