ABSTRACT
The paper shows both experimental and numerical results for micro-scratching tests applied to main hydration products of cement paste at the scale of 10–100 μm. In the experimental part, micro-scratch tests were conducted along with scanning electron microscopy and acoustic emission measurements to reveal local fracture toughness of individual cement paste constituents. 3-D finite element model of the scratch process utilizing Griffith-type of a fracture-damage model for tension/compression failure was successfully used for replication of the experiments and identification of local cement paste strength. The tensile strength for the outer hydration product was identified as 54 MPa being about 5 times lower compared to FIB-produced microcantilevers at 3 μm scale (Němeček, Králík, Šmilauer, Polívka, & Jäger 2016) and about 3.6 times higher than at 500 μm scale (Zhang, Šavija, Figueiredo, & Schlangen 2017). The strong size effect can be attributed to a different number of internal defects in the cement paste microstructure.
