IMPROVEMENT IN THE MANUFACTURE OF BRICKS OF BLAST FURNACE SLAG
Year: 1871

page_text: LETTERS PATENT to Frederick Lürmann, of Georg Marien Hütte,
near Osnabrück, in the Kingdom of Prussia, for the Invention of
"IMPROVEMENT IN THE MANUFACTURE OF BRICKS OF BLAST FURNACE
SLAG."
Sealed the 26th February 1872, and dated the 8th November 1871.
PROVISIONAL SPECIFICATION left by the said Frederick Lürmann at
the Office of the Commissioners of Patents, with his Petition, on
the 8th November 1871.
I, FREDERICK LÜRMANN, of Georg Marien Hütte, near Osnabrück,
5 in the Kingdom of Prussia, do hereby declare the nature of the said
Invention for "IMPROVEMENT IN THE MANUFACTURE OF BRICKS OF BLAST
FURNACE SLAG," to be as follows:-
-
The slag or scoria of blast furnaces, after having been granulated by
running it into water, or pulverized by mechanical means, is formed

page_text: alone, or after being mixed with quicklime or other suitable caustic
materials or cement, into all kinds of bricks. The form of the bricks
may be produced either by hand or by casting the mixture into suitable
moulds, or by pressing with machines driven by hand, steam, or hydraulic
power. The bricks made of this material are hardened by exposure to
the air: it is not necessary to burn them.
SPECIFICATION filed in pursuance of the conditions of the Letters
Patent, and of an Order of the Lord Chancellor, by the said Frederick
Lürmann in the Great Seal Patent Office on the 14th May 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FREDERICK
LÜRMANN, of Georg Marien Hütte, near Osnabrück, in the Kingdom of
Prussia, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of November, in the year
of our Lord One thousand eight hundred and seventy-one, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Frederick Lürmann, Her special licenco
that I, the said Frederick Lürmann, my executors, administrators, and
assigns, or such others as I, the said Frederick Lürmann, 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
cxpressed, 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 "IMPROVEMENT IN THE MANU-
PACTURE OF BRICKS OF BLAST FURNACE SLAG," upon the condition (amongst
others) that I, the said Frederick Lürmann, my executors or adminis-

page_text: |trators, by an instrument in writing under my, or their, or one of
their hands and seals, 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 Frederick Lürmann, do hereby declare
the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by
the following statement :-
This Invention relates to improvements in the manufacture of bricks
of slag of blast furnaces. The slag or scoria of blast furnaces, after
having been granulated by running it into water or pulverized by
mechanical means, is formed alone, or after being mixed with quicklime
or other suitable caustic materials or cement, into all kinds of bricks and
building stones. It is important that the slag should be reduced to a
finely divided state. This may be done, as a rule, in a cheap and simple
way by running it from the furnace into a stream of water, when it
becomes granulated. Should a further reduction be wanted, the granu-
lated slag may be pounded or ground. Old slag may also be used for
the manufacture of bricks, and may be reduced by pounding or grinding.
Some kinds of slag have the peculiarity to fall to powder when exposed
to the atmosphere, such need little or no reducing. A great part of the
silicic acid of the slag is disposed to enter into a vigorous chemical
reaction when brought into contact with basic substances, and forming
thus hardening silicates. I have found the caustic materials most suitable,
on account of their price and efficiency, to be quicklime alone or in com-
bination with caustic magnesia. To these substances small quantities
of caustic alkali may be added. The choice and quantity of the caustic
materials to be added to the slag depend on the chemical qualities of the
latter, and on the degree of the reduction it has undergone, and must be
found out by experiments. If lime be used, I have found that slag from
a furnace making white or forge iron, being coarse grained when granu-
lated, requires about one-fifth lime slaked into powder. For slag from
furnaces making grey iron, about one-seventh lime is necessary. The
lime in these cases is presumed to be calcined shell limestone. If

page_text: bydraulic ime be used, the former slag requires about one-tenti, the fatter
about one-fourteenth. If slag and lime be ground, and lime very good,
one-eighteenth is sufficient. The lime may be added to the slag in a dry
state (slaked into powder), and the mixture may then be used forthwith,
being sufficiently damp. If however the lime be slaked into a thin
paste-like condition, the mixture of slag and lime will become more.
homogeneous; in this case it cannot be used at once, but has to stand
for some time to allow a certain quantity of water to evaporate.
bricks made of the latter mixture are generally the better ones.
The
The mixing operation may be performed in a similar way to that for
making mortar either by hand tools or machinery. I prefer the vertical
mill for this purpose. The quantity of water to be added depends upon
the consistency required of the mixture. If bricks are to be made in the
same manner as ordinary ones of clay, by simple hand moulds or more
complicated mechanical appliances, the mixture should be a little moist.
Should too much water have been added, the mass may lay for some
time to allow the water to evaporate. As soon as it shows signs of
hardening it should be used. If the bricks are to be made by casting
into moulds the mixture should be semi-fluid. Bricks of great hardness
and density are produced by grinding the mixture of slag and quicklime
into a fine thin liquid paste, which is afterwards cast into moulds.
process is similar to that when making objects of cement.
The
Having been made either by ordinary moulding or by casting, the
bricks should be stowed away, that they may not suffer from frost or
from too fast drying. They should be allowed to dry gradually, as
during a slow drying process a good deal of water is absorbed chemically
by forming silicates. The bricks suffer no harm by becoming wet, as by
rain. The alternate effects of rain and dry air quickens the hardening
process, especially as besides the forming of silicate that of carbonate of
lime takes place vigorously.
-
Having now set forth the nature of the Invention of improvements in.
the manufacture of bricks of blast furnace slag, I wish it to be under-
stood that under the above in part recited Letters Patent I claim, the
Having now set forth the nature of the Invention of improvements in.
the manufacture of bricks of blast furnace slag, I wish it to be under-
stood that under the above in part recited Letters Patent I claim, the
using of slag of blast furnaces in combination with caustic substances or

page_text: cement, when both are in a finely divided state, for the manufacture of
bricks and building stones.
In witness whereof, I, the said Frederick Lürmann, have hereunto
set my hand and seal, this Nineth day of May, in the year of our
Lord One thousand eight hundred and seventy-two.
Witness,
CARL ALUENS,
Georgs Marien Hüste.
FREDERICK LÜRMANN. (L.S.)