Improvement in the Manufacture of Artificial Building Materials.
Year: 1892

page_text: Date of Application, 1st Dec., 1892
Complete Specification Left, 29th Aug., 1893-Accepted, 1st Dec., 1893
PROVISIONAL SPECIFICATION.
Improvement in the Manufacture of Artificial Building Materials.
I, FRIEDRICH WILHELM LÜHRMANN, Engineer, of 16, Mozartstrasse,
Düsseldorf, in the German Empire, do hereby declare the nature of this invention
to be as follows:-
.
Solid or liquid blast furnace slag is placed on the hearth of a reverberatory
furnace (or open hearth furnace), preferably a gas-heated Siemens-Martin-Furnace,
although other reverberatory furnaces may be used which produce a sufficiently
high temperature; and other materials are added to the molten slag. The mass is
subsequently removed from the furnace and allowed to cool, slowly or rapidly,
according to requirements, for which purpose moulds may be employed, to impart
the desired shape.
The nature of the materials to be added to the slag, mentioned above, depends
on the nature of the slag and the properties of the product to be obtained. For
instance, if the slag is deficient in lime, the latter is added in any suitable shape;
the same is the case with silica, alumina etc.
Consequently, the following materials will be chiefly used as a flux or addition to
the molten slag; limestone, either raw or calcined, dolomite, clay, quartz, oxide of
iron etc. and combinations of these substances, whether found in nature, or produced
artificially, for instance, other kinds of slag.
This process may be used for producing from blast furnace slag, cement, building
stones, paving stones, and other building materials.
Dated this 1st day of December 1892.
FAIRFAX & WETTER,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvement in the Manufacture of Artificial Building Materials.
I, FRIEDRICH WILHELM LÜHRMANN, Engineer, of 16 Mozartstrasse,
Düsseldorf, in the German Empire, 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 :-
Solid or liquid blast furnace slag is placed on the hearth of a reverberatory
furnace (or open hearth furnace), preferably a gas-heated Siemens-Martin-Furnace,
although other reverberatory furnaces may be used which produce a sufficiently
high temperature; and other materials are added to the molten slag. The mass is
subsequently removed from the furnace and allowed to cool, slowly or rapidly,
according to requirements, for which purpose moulds may be employed, to impart
the desired shape.
The nature of the materials to be added to the slag, mentioned above, depends
on the nature of the slag and the properties of the product to be obtained. For
instance, if the slag is deficient in lime, the latter is added in any suitable shape;
the same is the case with silica, alumina etc.
Consequently, the following materials will be chiefly used as a flux or addition
to the molten slag; limestone, either raw or calcined, dolomite, clay, quartz, oxide
of iron etc. and combinations of these substances, whether found in nature, or
produced artificially, for instance, other kinds of slag.
The slag used in the iron, copper, and lead blast-furnaces, have already a great
importance as building material for use above or below ground, and for the

page_text: construction of roads. They are used, according to their composition, for mortar,
stones for building, and paving, either alone or mixed with limestone and
other fluxes.
In many cases, however, the further use of the slag is often prevented on account
of its chemical composition. This composition cannot be altered in the blast
furnace, being dependent on the quality or character of the metal to be obtained.
Only small changes of the composition of the slag are allowable, in consequence
of effecting sudden alterations of the composition of the metal. One is therefore
forced to give to the slag the proper composition for its being further used, after
leaving the blast furnace."
For attaining this purpose, by my invention, the slag will be brought again to a
blast-furnace and will be exposed therein until it melts, that is to such a degree,
that it is able to combine with certain quantities of flux, by which means the
desired composition will be obtained. At the same time, by this re-heating, there
takes place a partial oxydation of the sulphur, which improves the product.
In order to utilize the heat of the once melted slag, it is preferable to put it into
the reverberatory furnace when still fluid, but this is not absolutely necessary, for
the result will be the same, if the slag is placed in the reverberatory furnace in a
compact (cold) state, but care must always be taken, that the materials are well
mixed together.
After its exit from the reverberatory-furnace, the slag will be cooled either
slowly, and so as to impart to the same a moulded form; or the cooling will be done
rapidly by water, steam, or air, which produces a certain well-known disintegration.
This process may be used for producing from blast furnace-slag, cement, building
stones, paving stones, and other building materials.
The manner in which the proportions of the ingredients should be chosen, will be
explained by means of an example. It is well-known, that the composition of
cement as hitherto made, is not constant, but subject to variations which do not
materially affect the quality of the product.
Among many samples of cement analysed I choose the following;

page_text: When this limestone gets into the liquid slag, it loses the carbonic acid (CO₂),
and there remain from 100 parts of limestone 57-28 parts of burnt lime composed as
follows;
The proportions of the ingredients should always be chosen in such a manner, that
the mixture contains as much lime as the cement. The lime represents the
basicity, while according to experiences with the working of blast furnaces,
SiO, Al₂O, represent approximately the acidity. (See "Stahl und Eisen" 1892,
page 2).
We will suppose, that for producing 100 parts of cement there are required parts
of blast, furnace slag and y parts of burnt lime. Then we have
The percentage of lime in this cement is the same as in the cement chosen as an
example, while the quantity of silica is somewhat lower, and that of alumina slightly
higher, so that the basicity remains the same. If it is desired, to increase the
silica and to reduce the percentage of alumina, some pure quartz and limestone may
be added.
-
58%
For producing mortar, the percentage of lime is brought to about 56
For the manufacture of building and paving stones an acid slag bath is produced,
by introducing quartz and alumina etc. The limits, between which the percentage
of silica and alumina may vary in finished stones, are very wide. I prefer, to mix
the material in such a manner, that SiO, + Al,O, is over 55 %, up to 70 or 80 per
cent., although a smaller quantity may be used, if the stones are afterwards well
tempered. The mixture is calculated in the same manner, as described above.
Instead of the blast furnace slag assumed in the above example, almost any other
may be employed. The method of calculation remains the same, in each case it is
necessary, to know the composition of the materials which are at disposal.

page_text: In most cases, it will be advantageous in carrying out our process, to add to the
fused mixture a few per cents. of oxide of iron in any convenient form.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is ;-
1. The manufacture of a material suitable for building purposes by reheating
slag in a reverberatory furnace with suitable admixtures, substantially as
described.
2. The process for the manufacture of artificial building material, which consists
in reheating slag in a reverberatory furnace, with suitable admixtures in the
proportions described, removing the mass from the furnace and allowing it to cool,
substantially as described.
Dated this 29th day of August. 1893.