FEATURES OF HIGH-ALUMINA SINTER SYNTHESIS
IN THE PRESENCE OF METASTABLE PHASES
I. D. Kashcheev,
M. A. Mikheenkov,
and K. G. Zemlyanoi
Translated from Novye Ogneupory, No. 12, pp. 15 – 18, December, 2013.
Original article submitted March 18, 2013.
Production of refractory cements by sintering is difficult as a result of the narrow temperature range for
sintering and high synthesis temperature. In order to expand the temperature range for sintering and reducing
firing temperature it is proposed to form an intermediate metastable phase in of high-alumina cement sinters.
Results are presented for synthesis of high-alumina cement sinters with formation within them of intermediate
metastable sulfatized phases.
Keywords: high-alumina cements, metastable phases, calcium sulfoaluminate.
One way of increasing the reaction capacity of raw mix
components in the manufacture of refractory cement clinker
is homogenization by combined grinding. In several works
Boldyrev [1, 2] indicated that mechanical activation of solid
crystalline materials improves their reaction capacity, pro-
viding a reduction in temperature for occurrence of solid-
phase reactions. An increase in reaction capacity of solid ma-
terials is connected with an increase in the number and type
of defects in their crystal lattice [3, 4], accumulating energy
and providing a change in Gibbs free energy.
In our work  it has been established that fuzed corun
dum, ground by different methods, has a greater degree of
amorphization and exhibits more defective surface (up to
emergence of atoms of a basic oxide from the lattice struc
ture itself), than untreated electrocorundum. A greater degree
of amorphization of fuzed electrocorundum leads to a change
in ceramic material properties. The material starts to sinter at
A raw mix for preparing clinker of refractory cements is
a multicomponent system, and therefore apart from increas
ing reaction capacity for each component it is necessary to
facilitate occurrence of solid-phase diffusion processes be
tween them. Synthesis of refractory cement clinker occurs
under conditions of solid-phase sintering without participa
tion of a liquid phase, and this limits diffusion processes, and
only in the concluding stage of synthesis is a liquid phase
It is possible to facilitate occurrence of solid-phase diffu-
sion processes in a raw mix by pressing at forces exceeding
the strength of crystals or raw mix hydrates. It has been dem-
onstrated in [7, 8] that pressing of raw mix leads to a reduc-
tion in temperature for the start of clinker synthesis.
A method for preparing cement using raw mix pressing is
protected by a patent .
Due to forming intermediate metastable phases in clinker
it is possible to increase its strength, and to increase the
sintering range and reaction capacity of clinker components.
The effect of metastable phases on synthesis of high-alumina
cement clinker has hardly been studied, and is almost not
used in cement manufacturing practice. In addition, in devel
oping a liquid phase during clinker synthesis under condi
tions for occurrence of phase transitions of the first order
many phases of cement clinker, formed under conditions of
solid-phase synthesis, become metastable with respect to
phases generated in a liquid phase. More stable phases
formed in a melt may differ with respect to composition from
decomposing metastable phase as a result of which under
boundary conditions of phase transition it is possible to form
an excess amount of free lime, or a shortage of it.
An excess amount of free lime forms when a decompos
ing metastable phase is a highly basic phase, and the stable
phase formed is low-basic. A shortage of lime forms when
the decomposing metastable phase is low-basic, and the
newly formed stable phase is highly basic. In this work syn
thesis of high-alumina cements is studied by forming a
metastable phase of calcium sulfoaluminate in clinker.
Refractories and Industrial Ceramics Vol. 54, No. 6, March, 2014
1083-4877/14/05406-0475 © 2014 Springer Science+Business Media New York
Proceedings of the International Conference of Refractory
Workers and Metallurgists (14 – 15 March 2013, Moscow).
FGAOU VPO Ural Federal University, Ekaterinburg, Russia.