Accelerating the reaction kinetics and improving the performance of Na2CO3-activated GGBS mixes

This study aimed to accelerate the reaction kinetics and improve the performance of Na₂CO₃-activated ground granulated blast-furnace slag (GGBS) via the use of reactive MgO and hydromagnesite seeds. The effect of 3–10% MgO and 0.5–1% seeds on the reaction mechanisms of Na₂CO₃-activated pastes was evaluated by pH, isothermal calorimetry and setting time measurements. Compressive strength results were used to assess the mechanical performance of the Na₂CO₃-activated GGBS concrete. A thorough investigation involving XRD, TG-DTG, and ²⁹Si and ²⁷Al solid-state NMR was performed to investigate the evolution of different phases. The inclusion of MgO and seeds promoted the removal of CO₃²⁻, increasing the pH and accelerating the dissolution of GGBS. The improved reaction kinetics via the use of MgO and seeds led to samples with shortened setting times, increased hydration and enhanced performance (43 vs. 14 MPa at 28 days) when compared to the control sample.