Effect of additives on the compressive strenght of slag-based inorganic polymers

The present paper aims to assess the effect of various additives on the compressive strength
of inorganic polymers (geopolymers) synthesised using low Ca electric arc ferronickel slag
and alkali activating solutions. The main operating parameters include pre-curing (48 hours),
temperature (40 to 80 oC), heating time (24 or 48 h) and aging period (7 days). Addition of
kaolinite, pozzolan, fly ash, red mud or CaO in the initial mixture has a detrimental effect on
the final compressive strength. Addition of pulverised silica sand improves strength slightly,
whereas addition of commercial glass results in strength values exceeding 60 MPa. XRD
analysis was carried out to identify new formed phases and the degree of amorphicity, while
SEM and element mapping analysis were used to identify the morphology of the final
products as well as to elucidate to a certain degree the mechanisms involved in inorganic
polymer synthesis.