Micro-mechanical properties of cement paste measured by depth-sensing nanoindentation: a preliminary correlation of physical properties with phase type

A simple Portland cement paste with a water/cement ratio of 0.45 without aggregate was prepared and cured for a minimum of 1 month under water. One cube was then cut and a polished thin slice prepared using simple petrographic techniques. One sample was subjected to depth-sensing nanoindentation over a regular grid of 50 positions on the sample, each spaced at 50 μm. After this, the sample was imaged in an FESEM for the locations of the indents and the compositions of the phases that were indented. BSE imaging was applied and quantitative EDS analysis used to determine the compositions of the phases and mixtures of phases that were indented point-by-point. Representative samples of the major phases of hydrated cement paste were indented as well as several interfaces between phases. The compositional results were correlated with the mechanical data to elucidate the mechanical properties of individual cement paste constituents and phase mixtures. It is hoped that this approach will provide much needed data on the mechanical properties of cement paste on the micro- to nanoscale as an input to the development of microstructural modelling. This detailed approach will also make more sense of previous work looking at the results of micro-mechanical testing of cement paste that treated the paste as a continuous bulk medium.