Improvements in the Manufacture of Hydraulic Cement for Building Purposes.
Year: 1892

page_text: Date of Application, 8th Apr., 1892-Accepted, 14th May, 1892
Improvements in the Manufacture of Hydraulic Cement for
Building Purposes.
I VERNER FREDERIK LASSO SMIDTH of 3 Amalievei Copenhagen, in the
Kingdom of Denmark, Civil Engineer, 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 object of this invention is to manufacture from ordinary cements, as offered
for sale, especially from Portland cement, an essentially cheaper cement from which
can be prepared mortar, having the high qualities of cementmortar but being in
cost of production equal to or lower than ordinary limemortar.
Ordinary cementmortar is prepared by mixing one part of cement with 1, 2, 3
or 4 parts of sand, and sometimes even larger quantities of sand are used. But in
preparing mortar, containing large proportions of sand, it is difficult to obtain an
even and uniform distribution of the two ingredients, and besides, the strength of
the mortar, when set, will be relatively small, because the quantity of cement is
insufficient to fill up the interstices between, and bind together, all the particles of
sand, which is necessary in order that the mortar shall form a firmly coherent
substance when set.
The object of my invention is, by grinding together ordinary cement (Portland
cement, Roman cement, or any other hydraulic cement) and a quantity of the same
admixture as that, which is generally used in the preparation of cementmortar
(generally sand, gravel or ballast), to produce a powder, called "sandcement," of a
similar degree of fineness as that of ordinary cement.
This sandcement is then to
be used in the same way as ordinary cement, mortar being prepared by mixing one
part of sandcement with.one or more parts of the ordinary admixture (sand, gravel
or ballast). By grinding together e.g. 1 part of ordinary cement and 3 parts of
sand, 4 parts of sand cement are produced, and from these a mortar can be prepared
in the proportion of 1 part of sandcement and 3 parts of sand, so that, out of the
1 part of ordinary cement 16 parts of mortar are prepared, when under ordinary
circumstances only 4-5 parts of mortar would have been prepared out of 1 part of
cement. Experiments giving satisfactory results have been made with even far
larger proportions of sand than that which has been named in this example.
By my invention is gained:
1. That for the filling up of the interstices between the particles of sand in
mortar, not only the expensive cement is used, but also the far cheaper ground
admixture.
2. That by the grinding together with the admixture the cement is absolutely
evenly distributed in this; by the preparation of mortar later on the cement will
therefore be adequately distributed in every part of this; no more sand, of course,
being used for the preparation of the mortar, than that the intervals between
the particles of same can be adequately filled with sandcement.
3. That in grinding the two ingredients together the cement will be further
pulverized, and thus will be capable of binding together larger surfaces of sand
than otherwise would be the case.
Numerous and comprehensive trials have sufficiently proved the utility of my
invention, and shewn that a very cheap mortar of superior strength can be
prepared from sandcement.

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 manufacture and use of a cement, produced by grinding together ordinary
Portland cement, Roman cement or any other hydraulic cement with sand, gravel, 5
ballast or any other admixture generally used in preparing mortar, to a degree
of fineness similar to that of ordinary cement.
Dated this 26th day of March 1892
V. F. L. SMIDTH.