Abstract
Micro-scratch test was used to evaluate the fracture toughness of the main hydration products of ordinary Portland cement paste at the micro-scale. The evaluation was done with the aid of scanning electron microscopy and acoustic emission (AE) signals. Portlandite was found to be the only phase where AE detected elastic waves due to cracking during microindentation and micro-scratch test. Such behavior simplifies phase separation during the evaluation process of the micro-scratch test. The micro-scale fracture toughness results obtained from the tests were found in close agreement with other available experiments and models in the literature.