Tensile strength of hydrated cement paste phases assessed by micro-bending tests and nanoindentation

Characterizing Strength and Failure of Calcium Silicate Hydrate Aggregates in Cement Paste under Micropillar Compression

“…These beams, however, are relatively large (20-μm length) compared with the length scales of individual C-S-H phases and may reflect the response of a heterogonous composite. In addition, use of relatively a high beam current in the final milling step [1 nA in Němeček et al (2016) compared with 0.1 nA in this study] might have led to a large amount of Ga þ implantation in the porous microstructure and an increase in measured tensile strength.…”

“…That study, however, did not consider the presence of porosity in C-S-H, which would be expected to reduce these values. Němeček et al (2016) used microbeam bending tests to estimate tensile strength of C-S-H intermixed with other hydration products in the range of 264-700 MPa. These beams, however, are relatively large (20-μm length) compared with the length scales of individual C-S-H phases and may reflect the response of a heterogonous composite.…”

“…Yet, few studies have explored the application of microcompression testing to granular and heterogeneous materials, which have a hierarchical microstructure like cement paste (Zhang et al 2010;Abousleiman et al 2016;Yilmaz et al 2015;An et al 2015;Dewers et al 2010;Han et al 2011;Luczynski et al 2015). Whereas one study used FIB-milled microbeams to assess the tensile strength of cement (Němeček et al 2016), uniaxial compression tests have never been performed on FIB-milled cement micropillars for assessing their compressive failure behavior. In this work, a new methodology is proposed to provide a quantitative portrait of the failure behavior of cement paste at Level 1.…”

Small scale tests of cement with focused ion beam and nanoindentation

“…However, current capabilities of the instrument do not allow to capture softening and the descending branch of the curves is not stable. Thus, the fracture energy was, in accordance with [6] assessed as supremum energy assuming that micro-beam behavior shows neither snap-back nor softening.…”

“…But until recently, it was not possible to access fracture properties of the small scale constituents. Němeček et al developed a methodology based on bending of FIB prepared micrometer sized specimens [6] where FIB allows preparation of geometrically precise microscopic samples and nanoindenter allows precise measurement of the bending response of the micro-beams.…”