Alkali activated steel slag – oil composites: Towards resource efficiency and CO₂ neutrality

This study describes advances in high-performance construction material development using a minimum of primary resources while enabling simultaneous CO₂ sequestration capacities. Two so far unutilized Austrian steel slags were combined with metakaolin and vegetable oil to produce alkali-activated materials exhibiting high compressive and flexural strength of up to 94 MPa and 13 MPa, respectively. This approach enabled a reduction in primary mineral resources of up to 82 wt%, with an average reduction in global warming potential (GWP) of 52 % compared to a traditional high-performance Portland cement material. Oil addition led to the formation of mainly water unsolvable metal soap phases precipitating within the pore spaces without significantly altering the phase assemblage and chemistry of the binder matrix, but further reducing the GWP by 74 %. The (heavy metal) leaching behavior coincides with that of traditional concrete materials and was even further reduced by the addition of oil.