CHROMIUM-BEARING CALCIUM HEXAALUMINATE FILLER
AND CONCRETES BASED ON IT
S. R. Zamyatin,
V. E. Gel’fenbein,
Yu. L. Zhuravlev,
and O. L. Babakova
Translated from Novye Ogneupory, No. 7, pp. 15 – 18, July, 2013.
Original article submitted April 22, 2013.
A new constant-volume high-alumina bonite filler has been created on the basis of calcined slag formed in the
production of metallic chromium. Calcining the slag at different temperatures increases its content of calcium
from 55 – 60 to 70% (calcination at 1450°C) and 90% (calcination at
1650°C). New compositions have been found for low-cement concretes based on the chromium-bearing
Keywords: chromium-bearing bonite, refractory filler, phase composition, thermomechanical characteristics,
Obtaining quality high-alumina fillers for refractory con-
cretes has become a serious problem in Russia in connection
with the lack of the raw materials (bauxites, andalusites)
needed for the fillers’ production. The prices of these materi-
als on the international market have climbed sharply in re-
cent years .
The solution is to develop an alternative high-alumina
raw material that does not depend on deliveries of raw mate
rials from China.
The companies “Almatis GmbH” (in Germany) and
Almatis Inc. (in the U. S.) have developed  and studied 
a synthetic refractory filler with an aluminate composition.
The content of CaO·6Al
in the filler ranges from 40 to
90%; the other mineral phases are corundum (a-Al
low-alumina calcium aluminates (CaO·Al
). The filler is characterized by a high density -
which reaches 90% of the theoretical density of CA
- and by
an apparent porosity of 5 – 15%. The synthetic filler is
known as bonite and has several unique properties, among
them being good refractoriness, low solubility in iron-bear
ing slags, good stability in reducing atmospheres (such as
CO), good chemical stability in alkaline media, and low
wettability by melts of ferrous metals and nonferrous metals.
This combination of properties makes bonite attractive for
use in the petrochemical, cement, and aluminum industries,
as well as ferrous metallurgy.
The technology used to obtain the sintered bonite filler is
based on the formation of briquettes from finely ground
low-impurity raw materials, subsequent sintering of the bri-
quettes at high temperatures, and crushing to the necessary
granulometric composition. In accordance with the phase di-
agram of the system CaO-Al
, heating of the initial charge
leads to successive formation of the following minerals and a
simultaneous increase in volume  due to the change in the
minerals’ density (Fig. 1):
12CaO + 7Al
(DV = + 25,6 %),
Refractories and Industrial Ceramics Vol. 54, No. 4, November, 2013
1083-4877/13/05404-0274 © 2013 Springer Science+Business Media New York
Experimental Refractories Plant (Verkhnyaya Pyshma, Russia).
Fig. 1. Melting point (———) and density (–––) of calcium