Enhancing the performance of MgO-activated slag-fly ash mixes by accelerated carbonation

Abstract This study focused on the development of reactive MgO (RM) activated-GGBS binders containing fly ash (FA). Performance of these binders was aimed to be improved by enhancing the hydration of RM and dissolution of GGBS and FA via high temperature pre-curing (HTPC); and conversion of unreacted phases into carbonates via carbonation. Spherical FA particles mitigated inter-particle surface frictions and improved flow. Although the use of HTPC accelerated the hydration of MgO, rapid precipitation of brucite hindered the dissolution of GGBS and FA and formation of associated hydration products. Transformation of RM into hydrated magnesium carbonates (HMCs) under carbonation led to significant improvements in sample performance via the pore filling effect and binding strength provided by HMCs, despite the degradation of ettringite and C-(A)-S-H during carbonation. Inclusion of 12 % FA resulted in comparable strengths to the control sample, highlighting the feasibility of incorporating FA within RM activated-GGBS samples without compromising performance.