Understanding the adhesion mechanisms between C-S-H and fillers

The adhesion mechanisms between C-S-H and fillers are of great significance when fillers are employed as a cement replacement. The affinity of a filler's surface towards ions in the pore solution of cement paste is reported in this work from the view point of the governing mechanisms. The discussion on various interactions is justified by results from zeta-potential measurements, and further supported by microscopic observations of hydration products on the filler's surfaces. The bond strength between the filler and hydrates is also evaluated. The C-S-H/filler adhesion appears due to the interactions between a filler's surface and calcium ions. In the case of calcite, the interactions between a filler's surface and calcium ions are predominantly determined by acid-base interactions which lead to the formation of a strong bond (most likely ionic-covalent bond). In the case of silica, the adhesion is found to be governed by an attractive ion-ion correlation force.