THE EFFECT OF CaO-RICH ADMIXTURES ON CONTROLLING DRYING SHRINKAGE OF ALKALI ACTIVATED MATERIALS

The worldwide production of Fe-Si-Ca rich residues is expected to increase and the development of suitable large-scale upcycling solutions is a pressing matter. Thus, alkali activation can be a viable valorization route and has attracted increasing attention. Still, alkali activated materials (AAM) are highly susceptible to shrinkage and as such can potentially limit their attractiveness for real-life applications. In cement industry, the swelling potential of oxide-based admixtures has been successfully used to counteract shrinkage effects. Nonetheless cement and AAM chemistry are entirely distinct and calcium compounds can affect the polymerization process and products formed.1 Further, the scarce existing literature on the use of oxide-based admixtures to control AAM shrinkage is focused on precursors with lowiron content;2,3 appreciable levels of the latter will infer with the polymerization reaction and increase the complexity of the reactions’ mechanisms involved. Hence, the present work assessed the feasibility of using CaO-based admixtures to mitigate drying shrinkage phenomena on Fe-rich AAM, while simultaneously investigated their impact on fundamental properties of fresh pastes and hardened specimens.