Hydration kinetics and microstructure evolution of NaCl-mixed tricalcium silicate pastes

The hydration kinetics of tricalcium silicate (C3S) pastes mixed with different concentrations of NaCl solutions were investigated by performing isothermal calorimetry tests. At the same time, the Boundary Nucleation and Growth (BNG) model was used to analyze the calorimetry data. The model fitted well with the calorimetric results. C3S pastes mixed with NaCl solutions followed a similar reaction path to those prepared with DI water, with an accelerated reaction rate as the NaCl concentration increased. The specific parameters, such as the in-duction and acceleration durations, were quantified, and the relationship was established. The BNG modelling results indicated that the increasing NaCl concentration significantly increased the nucleation rate of the hy-dration products while decreasing their growth rate slightly. That was supported by the SEM and STEM obser-vations. The presence of NaCl modified the morphology of the early-age calcium silicate hydrates (C-S-H) to relatively shorter and thinner fibres, which had a more compact microstructure and higher micromechanical properties than those in pure C3S pastes.

Automated summary

The hydration kinetics of C3S pastes mixed with NaCl solutions were investigated, and the results showed that NaCl accelerated the reaction rate and modified the morphology of hydration products.