Comparative investigation on nanomechanical properties of hardened cement paste
Three types of nanomechanical methods including static nanoindentation, modulus mapping and peak force quantitative nanomechanical mapping (QNM) were applied to investigate the quantitative nanomechanical properties of the same indent location in hardened cement paste. Compared to the nanoindentation, modulus mapping and peak force QNM allow for evaluating local mechanical properties of a smaller area with higher resolution. Beside, the ranges of elastic modulus distribution measured by modulus mapping and peak force QNM are relatively greater than that obtained from nanoindentation, which may be due to a result of the shaper probe and local confinement effect between multiple phases. Moreover, the average value of elastic modulus obtained using peak force QNM were consistent with those obtained by modulus mapping, while the different in modulus probability distribution could be related to the different nanomechancial theories and contact forces. The probability distributions of elastic modulus measured using nanomechanical methods to provide a basis for the different types of phases existing in cement paste. Based on the observation with high spatial resolution, cement paste can be likely found as nanocalse granular material, in which different submicron scale or basic nanoscale grain units pack together. It indicates that the peak force QNM can effectively provide an effective insight into the nanostructure characteristic and corresponding nanomechanical properties of cement paste.