ALKALI ACTIVATION OF IRON-RICH FAYALITE SLAG FRESH, HARDENED AND DURABILITY PROPERTIES ACTA UNIVERSITATIS OULUENSIS C Technica 884
|Adeolu Idowu Adediran
Fayalite slag (FS) is an Fe-rich by-product generated during non-ferrous metallurgy refining
processes. Currently, the annual global production of FS is 58 million tons, and this is likely to
increase soon due to the increasing demand for non-ferrous metals for varied applications.
Regrettably, only a small fraction of FS is utilized in low value applications with most of it ending
up in landfills. The aim of this thesis is to fully utilize FS as precursor for alkali-activated materials
(AAMs). AAMs are alternative cementitious materials that could provide environmental benefits
compared to Portland cement concrete.
Although FS contains a large amount of iron (>50%) and low amounts of calcium, aluminium,
and amorphous material compared to blast furnace slag, which is a commonly used AAM
precursor, the results of this thesis show that this low reactive material can be used as a sole
precursor (aggregate and binder source) for AAMs. Furthermore, the mineralogical investigation
of different particle size fractions of FS revealed a variation in the amorphous content. Fine
fractions of FS had a higher amorphous content, and this resulted in higher reactivity and better
mechanical and microstructural properties compared to the coarse fractions of FS.
AAMs containing FS as an aggregate and binder had superior mechanical and microstructural
properties compared to those containing standard sand as aggregates. Further optimization of the
particle size distribution and elevated temperature curing improved the properties of FS-based
AAMs. To avoid the use of curing at elevated temperatures, the incorporation of co-binders into
the FS matrix was investigated as a means to improve the properties of FS-based AAMs at an
ambient temperature and facilitate their practical application. The incorporation of co-binders
significantly modified the gels formed and improved the fresh, hardened and durability properties
of FS-based AAMs when exposed to different aggressive environmental conditions and high
temperature. The outcome of this thesis work can provide detailed information on the full
utilization of FS with high potential for construction applications.
Keywords: alkali-activated materials, durability, fayalite slag, fresh properties,
geopolymer, thermal stability