ADDITIVES TO CONTROL THE RHEOLOGICAL PROPERTIES
OF UNSHAPED CASTABLES
I. D. Kashcheev
and K. G. Zemlyanoi
Translated from Novye Ogneupory, No. 9, pp. 44 – 48, September, 2005.
Original article submitted March 9, 2005.
Comparative test data are reported for additives (available from domestic and foreign manufacturers) that are
commonly used to control the rheological properties of castables. The domestic additives are shown to be ef
fective thinners for refractory castable compositions and provide conditions for adequate water demand of
castable mixes not inferior to those of foreign additives. The physicomechanical properties of refractory
castables conditioned by domestic superplasticizers are likewise not inferior to foreign analogs except perhaps
for the mechanical strength.
In the production technology of a new generation of re-
fractory castables (zero-cement, low- and ultralow-cement),
a major concern is to provide the required rheological pro-
perties at a minimum water demand. In the first place, this is
due to the fact that the physicomechanical properties of a
castable (porosity, strength, etc.) and, correspondingly, its
performance characteristics are directly related to the mois-
ture content (water demand) of the molding system. Numer
ous techniques have been developed to improve the effi
ciency of castables and to minimize their setting and harden
ing times. Attention was focused on the key parameters that
control the rheological behavior of castables: particle size
distribution, solid phase concentration, the nature of raw ma
terials and chemical additives (dispersants, surface-active
substances (SAS), viscosity modifiers, and others) [1 – 5]. In
recent times, much effort has been put into the development
of thinning (deflocculating, plasticizing or stabilizing) addi
tives which, properly used, make it possible to reach the re
quired flowability of castable mixes at a minimum water
content and to control the setting and hardening times.
In this work, we have studied the technological proper
ties of some additives currently widely used in the refractory
industry: (i) Castament FS-20 and Castament FW-10 (SWK
Polymers GmbH, Germany); (ii) ADW and ADS complex
additives (Alcoa); (iii) compositions under a conventional
generic name Polyplast (available from a domestic manufac
turer Polyplast Joint-Stock Co., Russia); (iv) castables pre-
pared using the aforesaid additives. Relevant data are given
in Table 1.
In step 1, the effect of an additive and its concentration
on the needed amount of mixing water and the cement set-
ting time was studied; VTs-70-grade alumina cement was
used for that purpose. In step 2, a refractory castable (based
on a sintered bauxite from China) and CA-270-grade high-
alumina cement (Alcoa) were used. The filler was RotaHD-
grade bauxite (available from a Chinese manufacturer) fired
in a rotary kiln at 1600°C. The bauxite contained 85 – 90%
, 2–4% SiO
, 2–4% TiO
, < 1% Fe
, 1.2 – 1.5%
MgO; the open porosity of grains was 3 – 4%; the castable
mix had a maximum grain size of 6 mm.
The cement paste was tested for moisture content
(amount of mixing water) and setting time as required by
State Standard GOST 310.3. In step 2, test specimens were
prepared from castable mixes with optimum concentration of
additives and heat-treated at 110, 800, 1100, and 1500°C,
and their physicochemical properties were determined. The
specimens of length and diameter 50 mm were prepared by a
vibromolding method using metallic built-up molds. The
green preforms were seasoned for strength for three days and
then subjected to heat treatment.
The standard cone test (GOST 24211) could not be used
considering that at an operating moisture content of 6 – 8%,
the castable mixes were a semi-dry loose material that could
flow only when vibration was applied to it.
Refractories and Industrial Ceramics Vol. 46, No. 5, 2005
1083-4877/05/4605-0325 © 2005 Springer Science+Business Media, Inc.
Ural State Technical University (UGTU – UPI), Ekaterinburg,