The first problem: concrete will produce some condensation structures and voids during mixing and solidification and hardening. In these condensed structures and gaps, a large amount of mixing water is wrapped, thus reducing the water required for cement hydration. When superfine minerals are added to concrete, they can fill the gaps between particles and those condensed structures, occupying the original water space, thus releasing a lot of water. On the other hand, although ultra-fine minerals need a lot of water because of their large surface area, compared with the water they can release, the water demand is still very small. Therefore, when preparing high-strength concrete cement-based materials, adding superfine mineral admixture can reduce the water-binder ratio.
Second question: Compared with active admixture, the main difference of hydration products after adding admixture in cement is that the active admixture in cement can undergo secondary hydration reaction under alkaline conditions, that is, the silica component in the active admixture reacts with calcium hydroxide to form C-S-H gel, thus obtaining more products.