Structural build-up of cement pastes - Underlying mechanisms considering the particle packing, colloidal interactions and hydration kinetics

This study aims to investigate the decisive mechanisms of structural build-up of cement pastes. The structural build-up can be divided into three stages, with distinct developments in particle packing, colloidal interactions, and CSH bridges at each stage. Our model framework demonstrates that the first stage of structural build-up is influenced by heightened colloidal interactions and enhanced particle packing. The second stage is propelled by the strengthening of CSH bridges, while the third stage involves reinforced CSH bridges and increased particle packing. It should be noted that the impact of particle packing may be limited at low hydration levels. Upon examination, the physical-based structural build-up rates (Athix,f, ACA$H and ACSH) are identified as the results of enhanced colloidal interactions, increased particle packing and augmented CSH bridges, respectively. These parameters are validated as consequences of the initial particle packing parameter and rate factors, which denote the increase rate of van der Waals forces, the hydration rate at the beginning of hydration, and in the subsequent second and third stages. •Structural build-up is described by a three-stage model.•Structural build-up is attributed to the colloidal interactions, CSH bridges and particle packing.•Contributions of three driving forces to structural build-up was investigated.•The predominant mechanism governing structural build-up was clarified.