Early reactivity of sodium silicate-activated slag pastes and its impact on rheological properties

The fast loss of fluidity of sodium silicate-activated slag (SS-AAS) systems have been widely studied in the literature. In this study, the rheology of these cements has been correlated with the evolution of the reaction products formed over time. For this purpose, a combination of experimental characterization techniques, to study the pore solution composition and microstructure of SS-AAS pastes and thermodynamic calculations have been applied. The initial precipitation of ill-defined N-A-S-H and C-N-A-S-H producta leads to a fast increase of the storage modulus after 40 min of reaction. These products are formed from the reaction of the Na+ ions and silicate ions of the activator with the Ca2+ and aluminate species dissolved from the slag. However, when a shear is applied, the structure breaks down and fluidity is recovered, that infers that the attractive forces between the particles are low at the early stages of hydration.

Automated summary

The rapid loss of fluidity in sodium silicate-activated slag (SS-AAS) systems has been extensively studied. This study correlates the rheology of these cements with the evolution of reaction products over time, finding that initial precipitation of N-A-S-H and C-N-A-S-H products leads to a significant increase in storage modulus. Application of shear force causes structural breakdown and recovery of fluidity, indicating low attractive forces between particles during early hydration stages.