DEFLOCCULATED REFRACTORY CONCRETES
WITH A HIGH CEMENT CONTENT
D. E. Denisov,
M. E. Popova,
and M. V. Maksimov
Translated from Novye Ogneupory, No. 1, pp. 44 – 48, January 2008.
Original article submitted September 13, 2007.
Dependences are provided for the spreadability and mechanical characteristics of deflocculated concretes on
the content of microsilica, deflocculant and water. The effect of microsilica on hydration of calcium aluminate
cements is discussed.
The disadvantages of refractory concretes with a high
content of calcium aluminate cement are mainly caused by
the significant amount of water required for cement
hydration. On heating the hydrate formed during cement
hardening breaks down, and water leaves the concrete
forming pores; the concrete structure is loosened and the
strength is reduced. Technology free from these disadvan-
tages for low-cement concretes, in which part of the cement
is replaced by finely-dispersed corundum powder, reactive
alumina and microsilica (MS) exists, and it has already been
developed for several decades.
Deflocculation of low-cement and particularly ultralow-
cement concretes exhibit not only a dense and stable
structure, but also exceptional high-temperature properties
that are due to the low CaO content. However, for concretes
intended for operation at temperatures below 1300°C a
reduction in cement content is not mandatory. In this case it
is possible with success to use deflocculated concretes with a
high cement content exhibiting good rheological properties,
a dense and stable structure, as for low-cement concretes.
In addition, it is possible to expect from them certain
production advantages in laying, i.e. for example less sensi
tivity to overdosage of water .
Deflocculated concrete with a high cement content has
been the subject of a number of publications [1 – 3], but
dependence of its production properties (spreadability,
setting and hardening times, rate of strength increase) and
physicotechnical properties on the content of MS, defloc
culant, retardant and the amount of added water requires
further study. The aim of experiments described in this
article was clarification of these dependences.
The starting materials for test composites were granular
highly dense bauxite containing more than 90% Al
chamotte with a Al
content of 41%, finely ground
electrically melted corundum with an Al
content of more
than 99%, calcium aluminate cements Secar-71 (70% Al
Secar-51 (52% Al
), Ciment Fondu (40% Al
with an SiO
content of 96%. The deflocculant used was
sodium tripolyphosphate (STPP), and the retardant was citric
acid. Spreadability was determined by means of a cone 50 mm
high and a lower diameter of 100 mm. The cone was filled
with concrete, then the cone was removed making it possible
for the concrete to spread over the surface of a table fitted
with a shaking mechanism. The increase in concrete
diameter was determined after free spreading and subsequent
In the first stage simple rheological properties were
evaluated for the mix of cement and MS without adding
deflocculant. Results shown in Fig. 1 confirm the known fact
Refractories and Industrial Ceramics Vol. 49, No. 1, 2008
1083-4877/08/4901-0048 © 2008 Springer Science+Business Media, Inc.
OOO Aliter-Aksi, Russia.
Fig. 1. Water requirement (o), %, and spreadability with shaking
(u), %, for mixes of cement Secar-71 and MS without adding