A MULLITE-CORUNDUM MORTAR BASED ON ALUMINA
L. A. Babkina,
V. I. Drozd,
M. I. Prokopenko,
É. L. Karyakina,
I. A. Kutuzyan,
and N. A. Stepanyuk
Translated from Ogneupory i Tekhnicheskaya Keramika, No. 7, pp. 39 – 42, July, 2001.
A technology for production of a mullite-corundum alumina-based mortar has been developed and tested. The
newly developed mortar is recommended as a replacement for the standard MMK85-1-grade mortar based on
For the brickwork of heating units operating under
heavy-duty conditions (air heaters for blast furnaces, arc
furnaces, induction furnaces, glass-making furnaces, or soot
reactors), mullite-corundum components with an Al
content not less than 90 wt.% are used [1, 2]. For binding
up mullite-corundum components in the brickwork,
an MMK85-1-grade mullite-corundum mortar (TU
U 14-7-178–99 Specifications) is used that is prepared from
costly and not always readily available fused corundum and
clay that require an energy-intensive processing.
Therefore tests were conducted with a view to replacing
the fused corundum in the MMK85-1 mortar by a cheaper
and less scarce material.
In our tests, an alumina (State Standard GOST 6912–87),
a fused corundum (available from A. S. Berezhnoi Ukrainian
Research Institute for Refractory Materials Joint-Stock Co.),
and a clay (TU U 322-7-00190503-086–97 Specifications)
with an Al
content not less than 28 wt.% were used.
The mortars of experimental and standard (MMK85-1-
grade) compositions were prepared using an aqueous solu
tion of orthophosphoric acid. The quality of a mortar was
judged by inspecting the width of a joint formed by the mor
tar and by measuring the shear strength on mortar-bonded
test plates. Test plates with dimensions of 38 ´ 38 ´ 12 mm
cut out of a mullite-corundum refractory with an Al
tent not less than 88 wt.% were cemented with a mortar of
working consistency and calcined in a periodic kiln at
1580°C for 8 h.
It was established that addition of alumina to the mortar
left the width of the mortar joint virtually unaffected (0.6 –
0.8 mm for MMK85-1 and 0.5 – 1.2 mm for experimental
The shear strength, although showing a tendency toward
decreasing with an increase in alumina content and a de
crease in the corundum content, remained sufficiently high in
specimens cemented by the MMK85-1 mortar (18.7 MPa), in
specimens cemented by a mortar in which fused corundum
was partially replaced by alumina (12 MPa), and in speci-
mens cemented by a mortar free of fused corundum (7 MPa).
To see how a reducing medium may affect the strength
properties of mortar joints, the test specimens were calcined
at 1450°C for 4 h using a cryptol filler, or under conventional
conditions in a kiln fitted with silicon carbide heaters. No ad-
verse effect of the reducing medium on properties of test
specimens was established.
The essential feature required of the mortar is that it be
capable of bonding during the brickwork placement and dur
ing drying (heating). To that end, the adhesive strength of
alumina mortar, corundum-based mortar, and the MMK85-1
Refractories and Industrial Ceramics Vol. 42, Nos.7–8, 2001
1083-4877/01/0708-0294$25.00 © 2001 Plenum Publishing Corporation
A. S. Berezhnoi Ukrainian Research Institute for Refractory Ma
terials Joint-Stock Co., Kharkov, Ukraine.
Fig. 1. Photomicrographic picture of clay particles of the mortars
treated with H
and dried at 120°C for2h(´ 37,000).