The visualization of microcracks in aged cement mortar using tomography

The investigation of microcracks formation and their evolution in cement mortars during hardening of Portland cement-based materials is still a challenging task. Microcracks play a fundamental role in transport processes and localization of deformation. Their growth impairs durability of composite materials such as mortars and concretes. Even if cementitious materials are extensively utilized for construction works, only limited amount of knowledge is available on the structural development at the micro-metric scale. Nowadays, very fine Portland clinker phases are utilized due to their faster reaction rates required to speed up construction works. However, rapid hardening of cements is associated with potential risks of accelerated formation of microcracks, that, after some time needed for their interconnection, may be responsible for the serious deterioration, especially in outdoor environment. X-ray computed microtomography was applied to visualize microcracks formation in aged Portland cement mortar and image analysis helped to distinguish between air bubbles entrapped during mortar preparation and newly-formed microcraks in fully three dimensional non-destructive fashion. Besides the interest for modern concrete, since a high number of concrete immovable objects are now part of our Cultural Heritage, it is expected that the obtained results will also contribute to the conservation of such objects.