DEFORMATION OF NONFIRED REFRACTORIES BASED
ON PHOSPHATE BINDERS.* 5. CREEP SPECIFICS IN CEMENT MIXTURES
V. S. Bakunov
and U. Sh. Shayakhmetov
Translated from Novye Ogneupory, No. 5, pp. 47 – 51, May, 2007.
Original article submitted November 22, 2006.
The results of experimental studies of aluminosilicate cement are described identifying two temperature inter
vals of deformation, which differ in their creep regularities. The first range is typical of composites with an un
stable low-temperature structure (heat treatment up to 800°C), and the second interval is typical of relatively
stable high-temperature structures (> 1000°C). Two ranges of deformation are identified based on stress. In
the first range the deformation process is determined by sintering shrinkage under a load which is lower than
the surface tension; the second deformation range is typical of loads exceeding the surface tension.
Model experiments have been carried out on cement
composites of the finely-milled a-Al
course of deformation has been studied depending on stress,
testing temperature, and pretreatment temperature to estab-
lish creep regularities in the composites [13, 21, 24, 25].
Data are given on the effect of the degree of dispersion of
powder and the type and content of the phosphate
binder on creep. The main tests were carried out in 28-h iso-
thermal exposure under loading, of which 6 – 10 h corre-
spond to an unsteady stage. To calculate the creep rate in a
, we use data for a 16 h period, i.e., in the
course of exposure from 12 to 28 h. The duration of some
tests has reached 160 h; occasionally the tests lasted 12 –
We first determined the deformation temperature under
the standard load of 0.2 MPa. The model mixture demon
strated the softening temperature (0.6%) at 1285°C and 4%
deformation at 1345°C. Based on these data, we selected the
creep test interval from 900 to 1550°C. The data on deforma
tion under loading for heating at the rate of 4 deg/min to the
exposure temperature, as well as some characteristics of the
composites before and after creep tests, are given in Table 4.
It can be seen from Table 4 that in heating under a load rang
ing from 0.2 to 0.8 MPa the creep in isothermic conditions is
observed starting with 900°C. As the temperature increases
to 1100°C, the deformation within the unstable period grows
under all loads, especially under 0.8 MPa; at 1150°C under
the load of 0.4 and 0.8 MPa the deformation increase is even
more significant: 10 – 15-fold compared to the preceding
level. The deformation growth
is observed up to a tem-
perature of 1250°C and after that it grows monotonically and
insignificantly up to 1400 – 1550°C.
The kinetic curves for temperatures of 1100, 1150,
1250°C and loads of 0.2, 0.4 and 0.8 MPa are shown in
Fig. 20. At 1100°C and the load of 0.8 MPa (Fig. 20, curve
3 ) the deformation during the first 12 h is insignificant and
then we observe its abrupt increase in the unsteady mode,
which indicates a change in the deformation mechanism.
Presumably the diffusion-viscous flow plays a critical role in
the initial period and after 12 h the mechanism of grain slid
ing is activated and perceptibly intensifies the process. Under
higher temperatures (up to 1250°C Fig. 20b, c) the sliding
mechanism is the main factor in the formation of a liquid
phase. This mechanism is determined by the presence of alu
minum metaphosphate Al(PO
in the composite
above 900°C; the eutectic between them has the melting
point of 1212°C.
The rate of decomposition of Al(PO
below 1200°C is
low. For, instance, the weight loss per 1 h, as a consequence
of the reaction Al(PO
is equal to 0.35%
at 1000°C, 0.7% at 1100°C, and 1.2% at 1200°C. The P
released from the composite intensely retakes with Al
and forms AlPO
, which at the temperature of its deforma
tion slowly crystallizes (during at least 10 h). Under continu
ous heating of samples at the rate of 2 – 4 deg/min and their
subsequent exposure for 1 h, AlPO
can be identified by
Refractories and Industrial Ceramics Vol. 48, No. 2, 2007
1083-4877/07/4802-000128 © 2007 Springer Science+Business Media, Inc.
* Continuation. See beginning in Vol. 48, Nos.1–2,2007.
Joint Institute of High Temperatures of the Russian Academy of
BashNIIstroi State Company, Russia.