MODIFIED CORUNDUM LIGHTWEIGHT MATERIAL
BASED ON CRUDE UNGROUND ALUMINA
V. N. Sokov
and V. V. Sokov
Translated from Novye Ogneupory, No. 9, pp. 28 – 30, September 2010.
Original article submitted March 26, 2010.
Results are provided for a study of the possibilities of preparing corundum heat insulation objects based on
hydrophobized crude unground alumina; its content may reach 80%. The saving obtained is due to shortening
the service life, use of crude alumina without grinding, including drying of the unfinished product, trimming
and grinding of objects, and a reduction in raw material consumption for producing 1 m
Keywords: modified corundum lightweight material, crude alumina, microporous filler, hydrophobization,
Analysis of the production of corundum heat insulation
materials shows that their preparation technology is difficult,
energy consuming, and in the majority of cases it is far from
the optimum. Materials are prepared from finely ground
commercial grade alumina. A mix is poured into molds and
unfinished product drying lasts two days. After drying an ob-
ject is trimmed and ground, and the waste comprises up to
40%. Due to the high material content of objects (average
density 1300 kg/m
), considerable waste, a requirement for
fine grinding of alumina, and prolonged drying this technol
ogy is considered to be inefficient under market conditions.
Therefore, creation of an efficient and economic composition
for corundum lightweight materials with prescribed proper
ties by rational technology with simultaneous intensification
of production is an important and urgent task.
The actual method is introduction into a mix of micro
porous filler, within which it is possible to use crude un
ground commercial grade alumina, consisting of porous ag
gregates of spherolitic structure. The vibration ground alu
mina and microporous filler are considered as a single binder
of uniform chemical composition with low shrinkage on firing.
The essence of the method for preparing modified corun
dum heat insulation material includes the following. The
binder (ground alumina) and hydrophobized microporous
filler (unground commercial grade alumina) are mixed with
foamed polystyrene and mixed with an aqueous solution.
The casting mix obtained is poured into a closed perforated
mold and heated electrically. Above 80°C there is final foam
ing of the polystyrene granules; an excess pressure up to
0.4 – 0.5 MPa is created in the mold. Under the action of this
pressure there is removal of physically bonded moisture, and
this promotes compaction of the mix. After removing from
the mold on to a tray the unfinished product is dried and sent
In this work the possibility is evaluated of changing the
physicochemical properties of the surface layers consisting
of porous spherolites of the filler, in order to prevent mois-
ture absorption during preparation, shipment and charging
into a mold of the alumina-polystyrene. For this different wa
ter-repellent substances are used of the hydrophobic and
hydrophobizing types, not containing any subsidiary prod
ucts, which reduce corundum refractoriness.
Analysis of the effect of adding both forms on the capac
ity for changing the physicochemical properties of the sur
face layers of alumina particles showed that a hydrophob
izing substance, containing coarse asymmetrically arranged
polar molecules, is capable during absorption at a hydro
phyllic surface arranged in strict order to form by hydrocar
bon radicals, turned outwards, a hydrophobic layer. This
layer changes the force of the bond of alumina with water in
contrast to additions of the hydrophobic type, without react
ing with alumina and the rest of the mix in the form of me
It has been established that for normal mixing of hydro
phobized alumina with the rest of the components it is neces
sary that the hydrophobic shell on alumina particles is not
continuous, and has a network structure. Self-compaction
within a closed volume may be separated into two stages: an
initial stage, when under the action of foaming polystyrene
within the mix cavities disappear, and a final stage when
Refractories and Industrial Ceramics Vol. 51, No. 5, January, 2011
1083-4877/11/5105-0343 © 2011 Springer Science+Business Media, Inc.
Moscow State Construction University, Moscow, Russia.