AN IMPROVED PROCESS FOR THE MANUFACTURE OF CEMENT
Year: 1878

page_text: LETTERS PATENT to William Savidge Akerman, of Bridgwater, in the County.
of Somerset, for the Invention of "AN IMPROVED PROCESS FOR THE
MANUFACTURE OF CEMENT."
Scaled the 4th February 1879, and dated the 22nd August 1878.
PROVISIONAL SPECIFICATION left by the said William Savidge Akerman at
the Office of the Commissioners of Patents on the 22nd August 1878.
WILLIAM SAVIDGE AKERMAN, of Bridgwater, in the County. of Somerset
IMPROVED PROCESS FOR THE MANUFACTURE OF CEMENT."
" AN
I take blue lias shales, or shales and bydraulic limestone, such as hitherto used in
making ground blue lias lime, or which have even been generally considered useless
both for that purpose and for the manufacture of natural Portland cement.
The shales or shales and limestone are first selected, according to the proportion
of lime, alumina, and silica they contain, so that when mixed together in certain
proportions, they will contain a certain average percentage. They are then placed
together in a kiln, and burnt to the inferior limit of calcination. The burnt product
is then ground between millstones or otherwise disintegrated.
While in bulk, or whilst contained in moulds, as preferred, as much water is added
as the powder will absorb, and it is allowed to remain until it sets or becomes
thoroughly dry and hard (which it does become without any mixing while in a wet
state, or without the aid of artificial heat), when it is again burnt, but this time to
the superior limit of calcination, ie., to the verge of vitrifaction, and afterwards
ground.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Savidge Akerman in the Great Seal Patent Office on the 21st
February 1879.
WILLIAM SAVIDGE AKERMAN, of Bridgwater, in the County of Somerset.
IMPROVED PROCESS FOR THE MANUFACTURE OF CEMENT."
"AN
The object of my Invention is the manufacture by a simple and economical process
from materials hitherto converted into articles of small commercial value (such as
lump and ground blue lias lime) of an bydraulic cement of good quality and
color.
I make careful and judicious selections of certain shales and limestones with a
view to their containing in the aggregate, after the preliminary calcination here-
after mentioned, the proportions of lime, alumina, and silica usually employed in
the manufacture of Portland cement, and I select by preference such shales and
limestones as do not vary widely from such proportions; for example, I should not
select by preference a stone so rich in lime and poor in alumina and silica that it
would take a shale with a largo excess of silica and alumina to bring up the relative
proportions to the usual average. I then burn the limestones and shales, either
separately or together, in ordinary lime kilns to the inferior limit of calcination. I
then cause the burnt product or products to be ground between ordinary millstones
to a fine powder, care being taken (more especially if the different shales and lime-
stones were not burnt together) that the burnt products are thoroughly mixed,
either before or during the grinding operation. The powder thus produced is then
allowed to drink in as much water as it will absorb (no mixing while in a wet state
being necessary), and after the hydration is completed, it will almost immediately
commence to set, and in a very few days become perfectly hard and dry without
the aid of artificial heat. The product is then again burnt, this time to the superior
limit of calcination, and ground, and is then fit for use as hydraulic cement.
Thus, by a judicious arrangement or mixing of certain shales and limestones, and
by converting them in the first part of my process into a product somewhat similar
to that known as ground blue lias (hydraulic) lime, I am enabled in the second part
of my process, by merely wetting the powder while in bulk, to produce a substance
which will become in a few days thoroughly hard, and which, without the aid of
artificial heat, will dry and become fit for reburning, and which, when reburnt and
ground, is a cement of good quality and color..
It is common in the manufacture of Portland cement from the blue lias limestone
to, 1st, calcine the stone and withdraw it from the kiln as lime; 2nd, slake it; 3rd,
mix with it a proportion of clay and an excess of water in a wash mill or mortar
nill, whence it is, 4th, conveyed to reservoirs or tanks, and allowed to settle, tho
water being afterwards drawn off, and the mixture of lime and clay allowed to
harden; it takes weeks to become sufficiently hard to be removed to, 5th, drying
sheds, where it is dried on bot plates. It is then burnt and ground.
By my improved process I effect a considerable saving, 1st, in labor, and, 2ndly,
in plant.
As regards the former, the first grinding between millstones is much more expe-
ditious and economical than the mixing in a wet state (after slaking) with clay in
wash mills or mortar mills, and the subsequent running or conveying the mixture
into reservoirs; the removal thence and drying on hot plates are altogether
avoided.
In the matter of plant, no wash mills or mortar mills, hot plates, or drying sheds
or reservoirs (the last-named occupying immense space in a manufactory of any
importance) are required.

page_text: Having described the nature of my Invention, and the manner of performing the
same, I declare that what I claim as my Invention to be protected by the herein-
before in part recited Letters Patent is, the improved process of manufacturing
hydraulic cement, substantially as herein described.
In witness whereof, I, the said William Savidge Akerman, have hereunto set
my hand and seal, this Nineteenth day of February, in the year of our
Lord One thousand eight hundred and seventy-nine.
W. SAVIDGE AKERMAN. (L.S.)