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Steel slags 185

geopolymeric binders. In this work, four binary mixtures of FA and EAFS (FA/EAFS
with mass ratio of 100/0, 80/20, 70/30 and 60/40) were prepared. An alkali activator at a
liquid to solid ratio of 0.77 was prepared by mixing sodium water glass ([SiO 2 ]/[Na 2 O] 5
3.2) with 10 M NaOH solution in a mass ratio of 1.5. The SiO 2 /Na 2 O ratio of the final
alkali solution was 1.23.
The authors observed that the addition of slag to AF affected of reaction product as
the silicate structure formed which leads to a highly polymerised structure and, therefore,
improves the properties of the geopolymeric binders.
Compressive strength and pore width were studied, and the EAFS replacement of FA
in up to 30% presented the best behaviour, improving the strength of the FA-based geopo-
lymer by 30% with respect to those mixtures where 0% of EAFS was applied. In this
work, all mixtures were heated and it was observed that the EAFS addition causes great
loss in strength after heating above 600 C due to the structural changes in the amorphous

gel phase.
The addition of EAFS in amounts between 20% and 30% presented good results in
mechanical behaviour, and it is possible to add this kind of SS in geopolymer production,
using fly ash as the main precursor.
3. The use of steel LFS in the formation of geopolymers may be appropriate since they pres-
ent a composition similar to GGBFS. The use of these waste as precursor material in geo-
polymer production can convert this product into a reusable resource, producing the
environmental benefits of reducing carbon dioxide emissions and transferring them to
landfills.

Bignozzi et al. (2013) studied the mix design and microstructure, as well as the
physical mechanical characterisations of the new systems based on metakaolin and
LFS in different amounts. This work highlighted the effects of ladle slag addition
on the activation and consolidation processes.
In this research, several mixtures of Metakaolin and LFS were performed and
positive behaviour was observed in those where 50% or 60% of LFS were mixed
with Metakaolin. Optimisation in terms of critical pore radius and compressive
strength were detected for G-MK50 and G-MK40 which showed the best values,
making these mixes the most promising solutions for future applications in civil
and industrial engineering fields.
In this work, the researchers concluded that ladle slag could be applied as a new
source for the alkali activation process which, when appropriately combined with
metakaolin, can lead to the production of innovative materials characterised by
interesting performances and sustainable features.

7.4.3 Future research lines of steel slags in geopolymer
production

Future research lines must be pursued to overcome problems with the thermal cur-
ing process which leads to very high costs and so preventing the large-scale appli-
cation of geopolymer concrete. The adoption of self-curing can eliminate the need
for an externally applied heat source.
There are several alternatives that could improve the production of geopolymers.
In some studies, OPC was used as an additive to make geopolymer concrete at