CRACK GENESIS IN REFRACTORIES
V. A. Perepelitsyn,
F. L. Kapustin,
K. G. Zemlyanoi,
L. V. Ostryakov,
L. P. Yakovleva,
I. G. Maryasev,
and L. M. Mikhailovskaya
Translated from Novye Ogneupory, No. 8, pp. 23 – 30, August, 2016.
Original article submitted January 22, 2016.
Genetic classification is given for cracks with respect to origin in all stages of refractory production and use.
Microcracks in refractories generate both due to external action and also due to internal thermal, mechanical,
physical and chemical stresses of the first and second order. External and internal energy stress generators cre
ate more than twenty genetic types of micro- and macrocracks.
Keywords: genesis, refractories “cold” cracks, “hot” cracks, pressure, stress.
Pores and cracks are almost permanent structural ele-
ments of all refractory materials, objects, and heating unit
linings. They may have both a favorable and negative effect
on various properties of refractory products. In the majority
of cases extremely developed micro- and especially
macro-cracking has an extremely unfavorable effect on
molded refractory wear resistance, and therefore these ob-
jects are scrapped.
Apart from content, the terms “pore” and “crack” are
mainly common, but there are marked differences. From a
geometric point of view pores not filled with solid substance
are part of the internal volume of material, having three mea
surements: length, width, and height (pores of arbitrary
shape) or one size (pores of cubic spheroidal, or isometric
Pores and cracks arise in many stages of the evolution of
a mineral substance, both during geological processes in na
ture (metamorphism, tectonic phenomena, etc.), and during
manufacture and service of refractories, abrasives, ceramics,
glass, petrographic, and other varieties of commercial stone.
In order to form cracks an obligatory condition is normally
mechanical stresses, i.e., energy action of high intensity of
different origin. In contrast to cracks, pores as a rule are ob
tained in the absence of external and internal mechanical
Within the composition of all contemporary molded
refractories (apart from eloms
, including unfired materials
based on organic binders, a mineral substance clearly pre-
dominates. As is well known, almost all natural minerals and
those similar to them with respect to properties of inorganic
compounds have increased brittleness, i.e., a property in-
verse to impact strength. In fact, brittleness and insignificant
ductility predetermine the intensity of crack formation within
a mineral product, both at normal and elevated temperature.
In spite of a sharp difference in conditions for pore and
crack formation, in between them there is an intermediate
morphological formation, so-called pore-cracks .
Pore-cracks are a transitional geometric form of three-di
mensional open pores with a two-dimensional crack. It
should be noted that in determining open porosity by a stan
dard method in the overall value of this property there are
both open pores and pore-cracks, and also open microcracks.
Actual open porosity is the overall volume of open pores and
all pores of open cracks. As many years of practice has
shown, in refractories of magnesia composition the propor
tion of microcracks in the index for open porosity is not less
than one quarter of the overall volume. In objects of other
substance composition, the relative development of cracking
varies over wide limits in relation to different process param
eters for manufacturing and service conditions of refractories
in heating units.
Currently there is no standard quantitative method for
determining total cracking of natural and technical grade
Refractories and Industrial Ceramics Vol. 57, No. 4, November, 2016
1083-4877/16/05704-0394 © 2016 Springer Science+Business Media New York
FGAOU VPO Ural Federal University Ekaterinburg, Russia.
OAO Pervoural’sk Dinas Plant, Pervoural’sk, Russia.
OAO Gruppa Magnezit, Satka, Chelyabinsk Region, Russia.
Eloms are elastic composite refractory materials prepared from
plastic organic mixes with a mineral filler.