Nanoindentation investigation of creep properties of calcium silicate hydrates

The creep properties of calcium silicate hydrates (C-S-H) are assessed by means of nanoindentation creep experiments on a wide range of substoichiometric cement pastes. We observe that, after a few seconds, the measured creep compliance of C-S-H is very well captured by a logarithmic time function. The rate of the logarithmic creep is found to scale in a unique manner with indentation modulus, indentation hardness, and packing density, independent of processing, mix proportions, indenter geometry and load history. The comparison with macroscopic creep experiments on concrete shows that minutes-long nanoindentations enable a quantitative assessment of the long-term creep properties of cementitious materials, orders of magnitude faster than macroscopic testing. Finally, we show that a strong analogy exists between this logarithmic creep behavior of C-S-H and that of soils, which suggests a granular origin of creep of geomaterials.