PROCEDURAL ELEMENTS IN ESTIMATION
OF THE THERMAL SHOCK RESISTANCE OF DIFFERENT TYPES
OF REFRACTORY CONCRETE BASED ON CHAMOTTE FILLER
and R. Stonis
Translated from Novye Ogneupory, No. 2, pp. 47 – 51, January, 2010.
Original article submitted November 22, 2010.
A comparative analysis of the thermal shock resistance of refractory concrete based on chamotte filler, such as
traditional concrete, traditional concrete modified with the addition of microsilica, and medium-cement con-
crete, is performed. It is shown that the method employed to determine thermal shock resistance with the use
of cooling of the concrete samples with water cannot be applied to determine this indicator in the case of tradi-
tional and modified types of concrete due to the reaction of the water with minerals in the cement. The thermal
shock resistance of different types of concrete determined by means of ultrasonic equipment and the calcu-
lated thermal shock resistance criterion R
supplies the most accurate estimate of the thermal shock resistance
of the types of concrete studied here.
Keywords: refractory concrete, chamotte filler, thermal shock resistance, thermal shock resistance criterion
R?, thermal shock resistance criterion R
A number of different techniques that may be distin-
guished in terms of the method used to estimate the results,
the temperature to which the sample is heated, the method
employed in cooling the sample, etc. are used in different
countries to determine the thermal shock resistance of refrac-
tory concrete. These questions have been elucidated in detail
in . Many studies have shown that the results that are ob-
tained by different methods far from always coincide [2, 3].
As soon as new types of refractory concrete are discovered,
such as medium-cement, low-cement, cement-free, and other
types of concrete, such lack of correspondence is encoun-
tered more and more often .
Methods of determining the thermal shock resistance of
refractory concretes that utilize cooling of the concrete sam-
ples with water have been criticized due to the fact that the
tests are not in conformity with the actual conditions under
which concrete is used in heating plants and the unpredict-
able effect of water on the test material, as well as due to the
lengthy duration of the tests, since some types of concrete
withstand more than 100 heating-cooling cycles. However, it
should be noted that the estimate of the thermal shock resis-
tance that is ultimately obtained is understandable and
unique, i.e., it is the actual number of thermal cycles that
samples of concrete withstand which is determined.
Some methods  that make use of open-air cooling (or
cooling by means of cooled metallic surfaces) involve the
use of a small and fixed number of thermal cycles (e.g., five,
seven, or some other number). The residual velocity of the
ultrasonic pulse in the sample, which characterizes the ther-
mal shock resistance of the particular type of concrete, is
then determined. Inasmuch as concrete samples do not frac-
ture after a small number of thermal cycles, the indices that
are obtained are predictable and often do not differ very
greatly for different types of concrete. In such cases there
arises doubt when estimating the thermal shock resistance as
regards making a selection of the most appropriate type of
refractory concrete for particular operating conditions of the
thermal power plant.
Where there are difficulties in arriving at an interpreta-
tion of the results of studies of thermal shock resistance by
means of a specific technique, the use of such universal ther-
mal shock resistance criteria as R² or R
[5, 6], which are
generally used for different groups of materials, becomes
critical for refractory types of concrete as well. The criteria
are calculated by means of the following formulas
Refractories and Industrial Ceramics Vol. 52, No. 1, May, 2011
1083-4877/11/05201-0070 © 2011 Springer Science+Business Media, Inc.
Scientific Institute of Thermal Insulation, Gediminas Technical
University, Vilnius, Lithuania.