Additive for mortar and concrete

An additive for mortar and concrete composed of water-soluble, swellable polymeric substances, said water soluble, swellable polymeric substances being employed in a finely dispersed state in an aqueous solution of salt or organic solvents.

BACKGROUND OF THE INVENTION 
The present invention relates to a new and improved additive for mortar and 
concrete in the form of aqueous dispersions. 
Substances are already known to the art which improve the plasticity, the 
workability as well as the pumping properties of mortar and concrete. 
There are especially used derivatives of cellulose, such as methyl 
cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl 
cellulose. Also there have already been utilized ethylene oxide polymers, 
polyvinyl alcohol, polyglycol, sulfonated melamine formaldehyde resins, 
polyacrylic amide and similar substances for such purpose. 
What is disadvantageous is that all of the aforementioned products only can 
be utilized in a powder state. When using such products in powder form 
considerable difficulties arise since the substances are hygroscopic. The 
absorption of water from the air, which can amount to 45%, can bring about 
an adhesion or binding of the powder dosing installation. When using these 
substances in a dry state, there is additionally present the possibility 
of dust explosions. A further disadvantage resides in the fact that with 
the small additive quantities of about 50 grams per 2.5 tons concrete an 
exact dosing is associated with difficulties owing to the continuous 
absorption of water from the air. 
The aforementioned swellable additive substances are water-soluble polymers 
which owing to hydration of their structural layers gradually transform 
into highly viscous solutions. Owing to this property of forming with 
water highly viscous solutions, wherein it should be mentioned that in 2% 
solutions there have been measured viscosities up to 100,000 centipoises 
(cps) and for practically employed additives there are required 
concentrations of at least 10% and viscosities under 200 cps, these 
additive agents cannot be employed as solutions. 
SUMMARY OF THE INVENTION 
It is a primary object of the present invention to produce liquid 
preparations of such additives which can be easily and surely dosed. 
Now in order to implement this object and others which will become more 
readily apparent as the description proceeds, the invention contemplates 
producing aqueous dispersions of the swellable water-soluble substances, 
there being used as the dispersion agent a solution of salts or organic 
solvents, in which the substances are only partially soluble or insoluble. 
The proposed solution to this problem is based upon the properties of such 
substances that they are insoluble in aqueous solutions of salts, such as 
NaCL, Na.sub.2 SO.sub.4, MgSO.sub.4, Al.sub.2 (SO.sub.4) .sub.3, NaH.sub.2 
PO.sub.4 and so forth, as well as solvents, such as alcohol, glycol and so 
forth. The solution suitable for the production of a stable dispersion, 
the concentration and the nature of the electrolyte which is to be 
employed and the further dissolved substances, must be determined for each 
additive or additive agent. 
DETAILED DESCRIPTION OF THE INVENTION 
Now in order to further understand the basic aspects of the invention, 
there will be considered hereinafter a number of examples for the 
production of the dispersions according to the invention. The dispersions 
are highly fluid i.e. low-viscosity, good workable liquids. They possess a 
viscosity around 200 cps and are stable when stored. They can be thus used 
without difficulty in all conventional dosing devices for mortar and 
concrete additives.

EXAMPLE 1 
10 parts by weight hydroxyethyl cellulose are dispersed in 90 parts by 
weight of a 25% A;.sub.2 (SO.sub.4).sub.3 solution. In order to stabilize 
the obtained dispersion, there can be further added 1 part by weight 
bentonite. 
EXAMPLE 2 
20 parts by weight ethylene oxide polymer are dispersed in 80 parts by 
weight of a 15% Na.sub.2 SO.sub.4 solution and stabilized by the addition 
of 1 part by weight bentonite. 
EXAMPLE 3 
10 parts by weight hydroxypropyl cellulose are dispersed in 50 parts by 
weight propylene glycol and 40 parts by weight water. 1 part by weight 
bentonite is added for stabilization. 
While there are described present preferred embodiments of the invention, 
it is to be distinctly understood that the invention is not limited 
thereto, but may be otherwise variously embodied and practiced within the 
scope of the following claims.