Proceeding for the Production of Quick-setting (Hardening) Mortar of Hydraulic Gypsum.
Year: 1896

page_text: Date of Application, 6th June, 1896-Accepted, 29th Aug.,
1896
COMPLETE SPECIFICATION.
Proceeding for the Production of Quick-setting (Hardening)
Mortar of Hydraulic Gypsum.
LUDWIG MACK, Manufacturer residing at 17 Herdweg, Stuttgart in the
Kingdom of Württemberg, Empire of Germany, 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:-
gypsum.
The so called hydraulic gypsum is that modification of gypsum which is produced
by glowing the gypsum and which formerly whas called "dead-burnt
As a well known fact, this kind of gypsum, when treated with water is setting
within several weeks to a very hard mass, provided that the mass is prevented
from drying out too rapidly. This condition can in the building practice only be
performed in making floors by casting the hydraulic gypsum mortar upon a layer
of moist sand and rendering this mass as tight as possible by stamping or beating.
For this reason the hydraulic gypsum was until now only to be employed for the
said purpose.
The present improvement is founded upon the idea to prevent the said influence
of evaporation through the use of stuffs which are able to accelerate the setting of
the hydraulic gypsum. This purpose is attained by treating hydraulic gypsum.
with small quantities of salts or bases, which together with gypsum form
double salts or polyhalit directly or indirectly. Such salts or bases are :.
sulphate of potassium, sulphate of sodium, caustic kali or natron, carbonate of
sodium or potassium, sulphate of amonium, sulphate of magnesium and the like.
The first mentioned two kinds of salts act with the most energy, so that for
instance 400 grammes of crude calcinated sulphate of soda (Glauber's salt) are
sufficient to work 100 kilo. of hydraulic gypsum into mortar which sets within a
few hours. The said salts in the given proportion of weight are best ground
together with the gypsum stones as they come from the kiln (furnace) and this
mixture worked into mortar. The mortar may also be made in another way by
first dissolving the salts or bases in water and adding the hydraulic gypsum
afterwards.
Another modification of my proceeding consists in the glowing of small quantities
of the above mentioned saits together with raw gypsum in such a manner that the
salts begin to melt and become absorved by the glowing pieces of gypsum.
Hydraulic gypsum treated with the mentioned salts or bases shows the same
qualities as the so-called "Keene's cement" which is produced with much more
circumstantiality and expence. It is of course understood, that my said process
includes also the use of raw materials as for instance ashes, containing salts or
bases as above referred to.
By virtue of its absolute resistance against weather and of its hardness (which
can be considerably increased by stamping the mortar) my cement-gypsum
replaces with great advantage the much more expensive Roman-or Portland-
cement wherever its use is not required below water.
For the make of floors the quick setting of my mortar offers the advantage that
it may be cast also in dry layers and that the mass can be beaten finished and
polished almost immediately after being cast, whereas the old method requires a
great deal of time and depends upon a great many incidents.

page_text: The mortar prepared according to my direction admits also a considerable
addition of sand or slacks.
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 :
Proceeding for the production of quick setting (hardening) mortar of hydraulic
gypsum consisting
1stly. In the use of salts or bases which, together with gypsum form double
salts or polyhalit directly or indirectly.
2ndly. In the use of ashes or other raw materials containing the salts or bases
mentioned under No. 1.
Dated this 4th of June 190
LUDWIG MACK.