EFFECT OF COMPOSITE DEFLOCCULANT ON THE PROPERTIES
OF MEDIUM-CEMENT HEAT-RESISTANT CONCRETE
and R. Stonis
Translated from Novye Ogneupory, No. 11 pp. 45 – 48, November 2009.
Original article submitted April 28, 2009.
Comparative analysis is provided for the properties of medium-cement concrete based on mullite filler in rela
tion to different type of deflocculant. The effect of different deflocculants on concrete structure formation,
hydration, rheology, strength and heat resistance is discussed. It is proposed that in concrete with a composite
deflocculant it is possible to form nano-structures as a result of which there is a considerable increase in con
crete strength after drying at 110°C.
Keywords: medium-cement heat-resistant concrete, composite deflocculant, mullite filler, microsilica, ultra
sonic velocity, physicomechanical properties.
The possibility of controlling rheological properties of a
concrete mix by means of various plastifying additions
(deflocculants) is a subject of continuous scientific research
[1 – 3]. Currently there is a rich arsenal of such additions,
that are selected individually in relation to the type of con-
crete heat resistance, since individual deflocculants affect not
only the rheological properties of a concrete mix, but also
hydration of aluminate cement, and also concrete operating
properties [4 – 6]. Some widely used deflocculants differ
quite considerably in pH and electrical conductivity in aque
ous solution. For sodium triplyphosphate the pH = 8.5 – 9.3,
the electrical conductivity m = 0.9 – 1.3 mS/cm; for DARVAN
D811 pH = 7,9 – 8.1, m = 0.39 – 0.45 mS/cm; for polycarboxylate
ester Castament FS-20 pH = 4.3 – 4.6, m = 0.25 – 0.30 mS/cm. It
is understood that these properties of deflocculants are af
fected by pH and electrical conductivity of a concrete system
as a whole, and they are reflected in cement hydration. In
view of this it is quite interesting to use in heat-resistant con
crete composite (mixed) deflocculants, that expand the possi
bility of controlling hydration and material structure, and
thereby making it possible to improve the physicomechani
cal and other properties of concrete. Studies by S. Otroj 
have shown that due a mixed deflocculant (sodium triply
phosphate and polycarboxylate ester) it was possible to in-
crease the ultimate strength in compression of self-spreading
heat-resistant concrete with spinel fillers from 30 to 40 MPa
after drying at 110°C, and from 90 to 170 MPa after firing at
The aim of this work is a study of the effect of both indi-
vidual deflocculants (Castament FS-20, sodium triplyphos-
phate), and also combinations of them on the rheological
properties of medium cement concrete, hydration and forma
tion of an initial structure, and physicomechanical properties
after heat treatment.
The following materials were used for studies: micro
silica grade RW-Fuller from the German firm RW Silicium
96.1%), whose average particle size was about
150 nm (Fig. 1); alumina cement Gorkal-40 produced in Po
not less than 40%); mullite filler, prepared from
mullite refractory (Al
65%), by crushing and screening
on sieves; fine mullite, prepared by c]grinding in a laboratory
ball mill; deflocculants, i.e. Castament FS-20 produced by
BASF (Germany) and commercial grade anhydrous sodium
Measurement is carried out in this work of pH and elec
trical conductivity with a Mettler Toledo MPC227 instru
ment of a solution of composite deflocculant in water (0.1 g
FS-20, 0.2 g ST in 100 g distilled water) showed that this so
lution has pH = 7.6 and m = 2.13 mS/cm. It is apparent that
Refractories and Industrial Ceramics Vol. 50, No. 6, 2009
1083-4877/09/5006-0441 © 2009 Springer Science+Business Media, Inc.
Proc. International Conference of Refractory Workers and Metal
lurgists (Moscow 23 – 24 April, 2009).
Gediminas VTU Institute of Heat Insulation, Kaunas, Lithuania.