Young's modulus and creep of calcium-silicate-hydrate compacts measured by microindentation

In this paper, compacts of synthetic calcium silicate hydrate (C-S-H) with 0.8-1.5 calcium-to-silicon ratio (Ca/Si) and 30-80% porosity were prepared by one-direction cold pressing. The Young's modulus and the creep of C-S-H compacts were measured by microindentation. The degree of homogeneity achievable with the preparation method, the presence of cracks and their extent were investigated by scanning electron microscopy and X-ray tomography. The porosity significantly influences the Young's modulus and the creep of the compacts, while the Ca/Si has limited influence on the Young's modulus. The C-S-H compacts with higher Ca/Si exhibit lower creep than those with lower Ca/Si, however mainly due to the presence of portlandite at higher Ca/Si values. The calculated Young's modulus of C-S-H solids falls into the range 21-50 GPa. The contact creep modulus of C-S-H with similar porosity as in a hardened cement paste (close to 30%) is about 180 GPa.