DEFORMATION OF UNFIRED PHOSPHATE-BOUND REFRACTORIES
PART 3. DEFORMATION OF HARDENED CEMENTS ON HEATING
V. S. Bakunov
and U. Sh. Shayakhmetov
Translated from Novye Ogneupory, No. 3, pp. 139 – 143, March, 2007.
Original article submitted October 12, 2006.
Deformation tests have been made on hardened cements. A difference from unhardened ones, which show
considerable plastic (viscous) deformation, is that the hardened ones show mainly elastic strain with a small
inelastic component at a temperature exceeding the preliminary heat treatment value.
The next stage in our research was testing hardened
alumophosphate cement compositions [19, 22]. The speci-
mens had been heat treated at 300 and 600°C (series 4 and 5
respectively ). After heat treatment, the cement contained
the hydrated phosphates 3AlPO
O and 2AlPO
a mixture of cristobalite and tridymite forms of AlPO
also an amorphous phase. The preliminary treatment temper-
ature was determined from the previously described experi-
ments, which showed that the solidification temperature of
this cement was at 200 – 220°C, as was evident from the in-
crease in the compressive strength from 0.95 to 26.6 MPa on
heating from 20 to 300°C. Above 120°C, the specimens con
tained the high-temperature form of the orthophosphate
(cristobalite), which had a positive effect on the
strength. The porosities and densities of specimens heat
treated at 300°C hardly altered after heating in the range
300 – 1200°C (Fig. 6, curves 2 and 3 ). The sharp increase in
strength (curve 1) and density, and the considerable reduc
tion in porosity in the interval 1300 – 1400°C, are due to
sintering of the alumophosphate cement stone.
The deformation curves for cement specimens solidified
at 300°C (series 4) were obtained with a primary heating
cycle up to 500°C and cooling without load or under loads of
0.3 and 0.6 MPa, and also we repeated heating-cooling
cycles unloaded for a specimen tested in the first cycle of
20 – 500 – 20°C under a load of 0.3 MPa, as shown in
Fig. 7a. Deformation curves 1 – 3 indicate certain deviations
from a linear dependence characteristic of thermal expan
sion. As the load is increased, the elongation of the speci-
mens was reduced, and at 500°C it was 0.58 and 0.47% at
loads of 0.3 and 0.6 MPa respectively; without load, it was
0.78% (maximal expansion). All the curves show kinks in
the range 200 – 300°C, which are due to dehydration and are
usually observed on primary heating associated with harden-
ing of the cement; only at the ends of curves 1 – 3 is there a
certain deviation from a linear dependence characteristic of
alumophosphate cement. On cooling, residual deformation
was observed only on specimens tested at a load of 0.6 MPa,
but it was slight and was only 0.05%. On repeating the heat-
ing-cooling cycle, the specimen without load (Fig. 7a, curve 4 )
after primary testing in a heating-cooling cycle at a load of
0.3 MPa showed expansion increasing to 0.62%, while resi
dual strain was not observed.
Refractories and Industrial Ceramics Vol. 48, No. 1, 2007
1083-4877/07/4801-0073 © 2007 Springer Science+Business Media, Inc.
* Continuation: start in Nos. 1 and 2 for 2007.
Joint High-Temperature Institute, RAS, and Bashkiria Construc
tion Research Institute, Russia.
300 700 1100 1500
Fig. 6. Effects of heat treatment temperature t on the compressive
(1 ), open porosity P
(2 ), and apparent density r
for series 4 specimens.