集料化学特性对C-S-H成核和生长的影响

It is of great significance for the optimization and performance improvement of aggregates to investigate the influence of aggregate chemical properties on the nucleation and growth of calcium silicate hydrate (C-S-H)and its mechanism. In this work, limestone, quartz and magnesite were used as aggregates. The interactions between different aggregates and ions in a simulated solution were determined via zeta potential measurement. Also, the nucleation and growth of C-S-H on the surface of these aggregates were analyzed by scanning electron microscopy. The hydration heat of cement pastes with the micro-aggregates was examined to investigate the effect of aggregate chemical properties on the early hydration of cement. The results show that limestone surface has a strong adsorption of Ca²⁺ (i.e., chemical adsorption), leading to a high density of C-S-H nuclei and directional growth of C-S-H, and thus greatly promoting the hydration of cement. The adsorption of Ca²⁺ on quartz surface is due to electrostatic force, which is weaker than that due to the chemical adsorption. The density of C-S-H nuclei on quartz surface is thus much lower than that on limestone surface. In the case of magnesite, its surface has a high affinity for SO₄^2- rather than Ca²⁺, reducing the nucleation density of C-S-H on the surface of magnesite, and thus slowing down the early hydration of cement.