Dissolution-precipitation Hydration Mechanism of Steel Slag Based on Ion Exchange of a Layered Alkali-Activator

This paper provided a new alkali activator for steel slag cementitious material -layered sodium disilicate (LSD), and focused on its dissolution-precipitation mechanism based on ion exchange capacity of LSD. The results showed that LSD could act as an effective activator for steel slag and the higher compressive strength of pastes (S3(14.9 MPa) and S10(22.3 MPa) increased by 222% and 332% respectively) were achieved and a matrix with much denser pore structure was formed. The pore solution analysis indicated LSD could play a role as ions transporter to facilitate the dissolution of steel slag (mainly C2S and C3S). Analysis of the hydration products showed that the addition of LSD increased the formation of C-S-H gels, CaCO3 and Mg(OH)2, but reduced the content of hydrotalcite-like phase. In addition, TEM and FTIR analysis indicated that the laminar C-S-H gel generated from LSD-activated steel slag had a higher SiO2 and Al content and a higher degree of silicate chain polymerization.