Compressive strength and hydration process of sodium carbonate-activated superfine slag/marble powder binders

Abstract

Alkali-activated slag (AAS) attracted wide attention in low carbon cementitious materials. In this study, superfine slag was activated by sodium carbonate (SC), and marble powder (MP) was also used. The effect of MP on SC-activated slag binders were investigated in terms of fluidity, compressive strength , hydration heat and microstructure analysis. Additionally, carbon emissions of the binders were evaluated. Results showed that the compressive strength of SC-activated slag mortars was decreased with the addition of MP, but the strength was still at an acceptable level. The 7-day and 28-day strength of 5 % Na 2 O-E activated slag mortars was 52.0 MPa and 64.7 MPa, while that of the mortars containing 30 % MP was 21.9 MPa and 51.0 MPa, with an obvious decrease. The main hydration products of SC-activated slag/MP pastes were C-A-S-H, calcite, hydrotalcite and gaylussite, and MP seemed no hydration activity in this system. Moreover, carbon emissions of SC-activated superfine slag/MP binders were 104–126 kg CO 2 -e/t, and it seemed much lower than that of strong bases-activated slag system. Such results indicated that this kind of binders had great potential in low carbon cementitious materials. • Superfine slag was activated by sodium carbonate. • Marble powder was used as partial replacement of superfine slag. • Marble powder increased the fluidity but decreased the strength of mortars. • This kind of binders showed low carbon emissions.