Improvements in the Manufacture of Cement and Building Blocks.
Year: 1898

page_text: Date of Application, 24th Feb., 1898-Accepted, 2nd Apr., 1898
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Cement and Building Blocks.
I, FRANZ JOSEF BERGMANN, of 5, Möḥnestrasse, Neheim on the Ruhr, in the
German Empire, Manufacturer, 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, that is to say :-
This invention relates to the manufacture of cement, and building blocks, bricks,
or the like, from ungranulated blast furnace slag, thereby overcoming the objections
to the use of granulated slag; dispensing with the costly granulation and drying
processes for the wet slag-sand, and producing á better and more valuable article.
The production of ganulated slag for clinkers or cement stones heretofore, has
been by running water directly on to the outflowing hot slag, thereby reducing the
same to a foamy glassy wet sand which, for making cement stones, must, previous
to grinding undergo an expensive drying process in special furnaces, since it only
dries very slowly in the air, and has a tendency to cake into large solid lumps or
masses when left for a length of time in a heap.
The slag sand retains its glass-like character, produced by the rapid chilling effect
of the water, also while being ground, and consequently such ground material
contains but little of that fine dust which is both desirable and necessary in the
manufacture of cement.
Now, according to my invention, I avoid both these disadvantages, and I use blast
furnace slag which is not first granulated, but is, while in its solid state, broken up
and ground, after having been allowed to cool slowly in the ordinary large slag
carrying boxes.
The costly drying of the wet slag sand, as well as the granulating, become, by my
invention, unnecessary, as the slowly cooled and consequently non-vitreous blast
furnace slag when ground in apparatus similar to that used for the granulated slag,
gives a better powder containing a larger quantity of fine dust.
The employment of solid blast furnace slag, absolutely free of water, has the
further advantage that a simultaneous grinding of slag and lime (which latter is
intensely hygroscopic and can only be ground in a highly dried state) is possible.
By this means of production, the cement clinkers have a more thorough mixing of
constituents which, for the subsequent burning process of the stone, is so very
essential and advantageous.
The fine dust obtained, as before described, from ungranulated slag and lime, is
formed into stone in the usual way, and is then burned and ground, and finally made
into a product as valuable as Portland cement.
By continuing the process herein characterized, up to the formation of the stone
from the admixture of the ungranulated ground slag and lime, and exposing this
stone without burning and allowing it to harden in the air, a useful material is
obtained for employment as blocks, bricks, or the like for building and like purposes
which, in comparison with the stone formed by running liquid slag into moulds
possesses greater hardness, durability and uniformity of structure, and in comparison
with stone manufactured from granulated slag is much cheaper.

page_text: In this manufacture of cement stones, I can use, besides milk of lime, a mixture
of coke dust and slag rich in silicates, such as cupoia slag, copper slag, or the like,
as a means for binding it, the coke dust facilitating the diffusion of heat in the
interior of the stone and ensuring a more uniform hardening of the same.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is :-
1. For use in the manufacture of Portland cement, clinkers or stones produced
from solid ungranulated blast furnace slag and lime, (with or without the addition
of a mixture of coke dust and slag rich in silicates, such as cupola slag, copper slag,
and the like) and then ground and formed into shape.
2. For use in the manufacture of building blocks, bricks, or the like, clinkers or
stones produced as above claimed, but hardened in the air instead of being burned.
Dated this th day of repruary, too.
ERNEST DE PASS,
Chartered Patent Agent,
78, Fleet Street, London, and 5A, Market Street, Nottingham,
Agent for the Applicant.
"