SPECIFICATIONS FOR MOLDED MATERIALS
USED IN REFRACTORY LININGS
I. D. Kashcheev
Translated from Novye Ogneupory, No. 2, pp. 43 – 46, February, 2009.
Original article submitted August 21, 2008.
Basic specifications are formulated for the grain-size composition, binder content, and contents of fibers and
rheological additives that favor the formation of a dense and strong structure in molded materials (in the main
concrete). The effects are considered on the thermal resistance and cracking resistance.
Keywords: molded refractories, lining, structure, fiber reinforcement.
The refractory materials used in heating plant not only
serve to contain the heat source but also often participate di-
rectly in the technological process. For example, in metal
production they act on the reactions and heat balance in the
plant. New advanced technologies have reduced the total
volumes of refractory materials used in metallurgy and at the
same time have improved the quality, and there has been an
ongoing increase in the proportion of such refractories in the
The various elements of thermal-plant lining are subject
to heat and chemical processes characteristic of those parts.
For example, parts used in packing are subject to slight ef
fects over a thickness of 20 – 30 mm and should have high
thermal conductivity, whereas the walls and roof of a furnace
require refractory materials with minimal thermal conduc
In recent decades, there have been substantial changes in
the structure of the demand for refractory materials. There
has been an ongoing increase in the production and use of
these molded materials: concrete, spray coating masses, fill
ing and repair powders, and so on. The production and use of
these refractories has some advantages for the production
and the user . A major advantage is the lower thermal con
ductivity by comparison with an analogous lining made from
refractory bricks. As a rule, the lining made from molded
refractories is monolithic. The materials include self-adjust
ing concretes, which have good working properties. One can
raise the flow and mobility in combining ordinary concrete
blocks by increasing the amount of water, but that increases
the lining porosity.
The grain-size compositions of self-adjusting concretes
differ from those of ordinary standard ones in that the latter
consist of powders of particle size 0.088 mm, while the for-
mer are of 0.044 mm, i.e., the particles are smaller in size by
a factor 2 (and sometimes more). The finely divided particles
(in the limit, nanoparticles) lie between larger ones and fill
the cavities (Fig. 1), which reduces the friction and porosity
and requires less water.
A general trend in current refractory technology is de-
signed to produce high quality with the provision of mini-
mum consumption by users, which is offset by the high pro-
duction costs of the refractories.
These molded materials with their binders occupy an in
termediate position between ones showing liquid flow and
solid behavior. When the lining is made from them, one gets
a certain spatially strengthened structure arising from vis
The structure may be regulated by optimizing the
grain-size composition, since this influences the shrinkage
on heat treatment and use, as well as the thermal resistance
and temperature dependence of the strength. The size com
positions are polydisperse, which is determined by techno
logical requirements and working specifications.
The grain size may be chosen to produce the closest par
ticle packing in the lining. Figure 1 shows the scheme, which
indicates that the content of grains of a certain size should be
strictly regulated. In practice, such a scheme is difficult to re
alize because the grains of refractory powder are not spheri
cal, so in practice the number of grains of a certain size (the
fraction) and the size of it are determined by experiment,
e.g., from the maximum poured density on vibration. The
minimum porosity of the refractory lining is very often at
Refractories and Industrial Ceramics Vol. 50, No. 1, 2009
1083-4877/09/5001-0057 © 2009 Springer Science+Business Media, Inc.
Ural State Technical University and Ural Polytechnical Institute,