Properties of alkali activated aluminosilicate ... - thermophysics.ru

on the correspondingly low value. The most probable reason for this behavior was the growth
of akermanite crystals on the seeds formed at lower temperatures which was promoted by the
high temperature environment. This statement is supported by XRD results in Fig. 7 where
the amount of akermanite phase was remarkably increased. The transition of the binder phase
was after heating to 1200 0 C apparently completed. As it is documented in the SEM image of
the binder-aggregate interface in Fig. 8, the cracks in the binder phase disappeared due to a
sintering process and the contact between aggregates and the new binder phase was
reestablished. Therefore, the improvement of mechanical properties was quite logical. The
difference in porosity and thermal conductivity as compared to the reference material was due
to the appearance of new binder phase on the basis of akermanite which had different
properties than the original CSH structure.
Fig. 8 SEM image of the aggregate-binder interface after heating to 1200 0 C
5. Conclusions
The results of measurement of basic, mechanical and thermal parameters of the
aluminosilicate material based on slag alkali activated by water glass after thermal load up to
1200 0 C in this paper revealed good perspectives of the material in practical applications. The
original CSH structure of the binder was after high-temperature exposure found to be
gradually replaced by a new structure based on akermanite which after heating to 1200 0 C
exhibited superior mechanical properties well comparable with the properties of the original
material not subjected to any thermal load. In addition, the porosity of the material was after
heating to 1200 0 C significantly increased. This makes very good prerequisites for using the
material in such applications where traditional cement based materials fail, for instance as fire
protection materials, or using it in the form of protective layers for the current reinforced
concrete structures, for instance in tunnels. Taking into account that the material is partially
based on waste materials, which serve as secondary raw materials for the forming of the
binder system, it is possible to consider it as a low-energy material, so that it meets a trend
common in recent production processes.
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