Mechanical properties of calcium silicate hydrates

The dynamic mechanical properties of compacted samples of synthetic calcium silicate hydrate (C-S-H) were determined at variable stoichiometries (C/S ratio). The stiffness and damping properties of the C-S-H systems were monitored at various increments of mass loss from 11%RH following the removal of the adsorbed and interlayer water. The changes in the storage modulus (E') and internal friction (tan delta) were discussed in terms of the state of water present in the nanostructure of C-S-H, the evolution of the silicate structure and the interaction of calcium ions in the interlayer region. Results were compared to those for the hydrated Portland cement paste and porous glass. It was shown that the C-S-H in the hydrated Portland cement has a complex yet analogous dynamic mechanical behavior to that of the synthetic C-S-H. The response of these systems upon the removal of water was explained by a layered model for the C-S-H. A mechanistic model was proposed to describe the changes occurring at various stages in the dynamic mechanical response of C-S-H.