Interaction between calcium hydroxide and calcium-alumino-silicate-hydrate on micromechanical properties

Calcium-alumino-silicate-hydrate (C-A-S-H) and calcium hydroxide (CH) are the two primary hydration products that play crucial roles in the mechanical properties of cementitious materials , particularly in the viscoelastic behavior known as creep. This study used hydrated C 3 S and a mixture of the synthesized C-A-S-H and CH to identify the interactions between CH and C-A-S-H. The interactions that dominate the mechanical properties mainly operate from physical and chemical perspectives. CH exhibited a filling effect on C-A-S-H in the physical interactions, demonstrating multi-scale particle packing efficiency. The particle size of CH per unit volume of the mixture was proposed as a critical parameter for the filling effect. Regarding chemical interactions, the synthetic system exhibits interactions primarily through van der Waals forces through compaction. In contrast, the interaction in the hydration system primarily originates from the strong atomic bonding between C-A–S–H and CH at the nanoscale . • C3S hydration and mimic system were designed to investigated the interaction between CH and C-A-S-H. • CH exhibits the role of multi-scale filling in C-A-S-H, which has a significant impact on micromechanical properties. • At 40-60 % CH content, optimal initial packing density of CH and C-A-S-H affects final micromechanical properties. • The cohesive forces in the mimic and hydration systems are van der Waals and strong atomic forces, respectively.