THE MATERIAL COMPOSITION AS A CENTRAL STRUCTURAL FACTOR
IN THE DESIGN OF HIGH-PERFORMANCE REFRACTORIES
A. S. Korolev
and M. Kh. Shaimov
Translated from Novye Ogneupory, No. 11, pp. 50 – 54, November, 2003.
Principles for the design of high-performance refractory composites are outlined using, as an example, sys
tems high-alumina cement – filler – mineral modifier and alkali alumina silicate bond – filler – modifier.
At present, refractory castables, bonds, and ceramic
castable mixtures are prepared using various combinations of
binding agents and fillers of different structural, material,
and granular composition. This procedure (mixture desing)
provides a route to durable refractory materials and makes
the development of unshaped refractory mixtures a promis-
ing challenge for modern refractory technology.
The judicious mixture desing would imply that in com-
posites, structurally made of continuous and discrete compo-
nents, a binding matrix, and a filler, the discrete component
is capable of exerting a modifying effect on the matrix. That
is to say, the filler should not be regarded as an inert compo-
nent since it is capable of displaying both surface and chemi-
cal activity depending on external factors and mixture com
In [1, 2], the effect of topological compaction of com
posite systems has been reported by which high-density
structures could be obtained through combining particles of
different dispersity. In this study, we discuss effects associ
ated with the self-compaction and internal stress relaxation
of composite systems under high-temperature conditions and
during solidification and incipient structure formation.
OF BINDING COMPOSITE SYSTEMS
The effect of self-compaction manifests itself as a short-
range structural anisotropy in the matrix of a composite. Ani
sotropy arises under the action of surface forces associated
with the filler and finely disperse inclusions. A variable po
rosity, or density, builds up in the direction from the surface
of a filler towards the center of a matrix interlayer, which re
sults in the occurrence of an integral compaction effect.
Structurally, the composite can be visualized as com
posed of a matrix, a filler, and a matrix/filler contact zone. In
various circumstances, under the action of filler’s surface
forces, self-compaction of the matrix of matrix/filler contact
zone can be observed. Three mechanisms for the composite
self-compaction can be envisaged: (i) a hydraulic mechanism
for water-dispersion binding systems (cements); (ii) an ad-
sorptive-polymerization mechanism for polymer systems
(asphalt-resinous and polymer composites); (iii) a mixed
mechanism for water-dispersion cement-polymer systems
(emulsion and water-silicate cement-polymer composites).
In the hydraulic mechanism of composite self-compac-
tion, the defective zone is the matrix/filler contact zone, and
the compacted zone is the matrix layer because the filler
shows a higher surface activity towards water. So, in the ce
ment stone, where the moisture becomes chemically bound
during hardening, the average size P of capillary pores (a
factor mainly responsible for the decrease in both strength
and impermeability) is expressed by the following relationship:
P = k
is the binder parameter (for the high-alumina ce
ment, it is 17.8 m
/kg); W/B is the water-to-binder ratio; k is
a factor that parametrizes the amount of the chemically
bound and adsorption-bound water scaled against the mass
of the binder, k = 0.4 – 0.46; a is the degree of hydration of
the binder, a = 0.5 – 0.8.
One will note that the average capillary pore size plotted
as a function of the W/B ratio is quite different for high-alu
mina cement stones without a filler and with a filler (Fig. 1).
In the composite stone at the same water content, a matrix
layer with a higher degree of compaction is formed:
is the composite compaction factor.
Refractories and Industrial Ceramics Vol. 44, No. 6, 2003
1083-4877/03/4406-0411$25.00 © 2003 Plenum Publishing Corporation
South Ural State University, Chelyabinsk, Russia; Mechel Joint-
Stock Co., Chelyabinsk, Russia.