High-speed mechanical mapping of blended cement pastes and its comparison with standard modes of nanoindentation

The paper presents a new nanoindentation mode of accelerated property mapping (XPM) which is designed to access local mechanical property maps in the order of minutes, i.e. much faster than with standard modes of grid nanoindentation or modulus mapping. XPM is tested on three typical cementitious samples: cement paste, fly-ash and slag blended cement pastes. The results from the techniques were found quantitatively comparable in terms of local mechanical properties. The methods are characterized by different spatial resolution, different property fluctuations and acquisition times. High-speed loading in XPM brings strain rate effects that are not present in standard modes. The paper summarizes advantages and disadvantages of each technique and shows mutual comparisons for the tested composites. It is concluded that the new XPM mode brings an advantage of very fast characterization of heterogeneous composites with reasonably high spatial resolution. The quantitativeness of the method is disturbed by strain rate effects causing artificial shift of the properties towards higher values compared to static loading cases. Some parameters associated with longer acquisition times such as creep properties are not captured with XPM. XPM is especially suited for fast sensing of local differences between composite phases on smaller areas (approximate to 10(3) mu m(2)). Statistical data from larger sample areas (104 105 mu m2) are still easier obtainable from classical grid nanoindentation.