Nanomechanical properties of C-S-H gel/cement grain interface by using nanoindentation and modulus mapping

Abstract

Investigation on the mechanical properties of cement-based materials at micron and sub-micron scales is important for understanding its overall performance. Recent progress in experimental nanomechanics opens new access to nanoengineering of cement-based composites. In this study, nanoindentation and viscoelastic modulus mapping were employed to study the interfacial properties. The interface width measured by modulus mapping was around 250 nm as compared to a rough estimation of less than 5 μm by nanoindentation, due to the fact that 2 orders of magnitude increase in spatial resolution could be achieved by modulus mapping. Both the nanoindetation and modulus mapping results indicated that the modulus of the interface falls between 60–70 GPa. The packing density in the interface was non-uniform as two peaks of value were observed for the storage modulus distribution. This interface could be regarded as a dense hydration coating around cement grains, which was less permeable and hindered the further hydration of cement.