The influence of the chemical and physical properties of C-S-H seeds on their potential to accelerate cement hydration

The development of green cements and reduced cement contents in concrete for reducing CO2 emissions, often results in reduced hydration activity and strength, especially in early stages, which conflicts with economic interests and process requirements. Besides pozzolans like nano-silica, the performance of calcium silicate hydrate (C-S-H) nanoparticles has recently become a focus of research, due to their outstanding ability to accelerate cement hydration, without compromising the long-term strength of the seeded cement. Many C-S-H properties have been found to influence their accelerating performance, with controversial results having been published regarding the calcium to silicon ratio. While Alizadeh et al. have found that the hydration of C3S is accelerated more when C-S-H seeds richer in silicon are applied, Land et al. have found that seeds richer in calcium are better accelerators. Neither particle size nor respective surface area were kept constant in either work. Using stoichiometry within the stability range of C-S-H, this work aims towards a systematic investigation of the influence of the chemical and physical properties of C-S-H. The impact on cement hydration is examined using isothermal heat flow calorimetry as a screening method