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Ch. Hellmich:
"Mechanics-guided quantitative approach to biomineralization and cement hydration";
Vortrag: APS March Meeting 2021, USA (eingeladen); 15.03.2021 - 19.03.2021.

Relations between biological systems and man-made structures have been intimately related since the dawn of the latter, and recent decades have seen these efforts being extended more and more towards emerging systems "hardening" out of an originally liquid environment. In this context, we have followed an approach rooted in the rich tradition of continuum mechanics, which is the basis for state-of-the-art design of buildings, and extended it towards complex hierarchical micro and nanostructures, thereby establishing links to materials science, physics, chemistry, and biology. In other words, micro and nanostructural building blocks and the "universal" patterns they build up within material systems (such as hydrating cement or bone) were linked, via continuum poro-micro-mechanical principles, to the scale-dependent mechanical properties (poro-elasticity, viscoelasticity, plasticity/strength) governing the material behavior. The same structural patterns, when put into an X-ray physics framework, satisfactorily predicted diffraction data. This provided a new level of rigour and reliability in the field of "structure-property-relations"; but surprisingly, it also sharpened the eye for the evolution of the material systems, such as biomineralization of bone [9] or hydration of cement. Conclusively, bone, at the ultrastructural level, appears as a hydrated nano-composite of aligned mineralized collagen fibrils embedded into a porous polycrystalline matrix, with the fluid-to-solid phase transitions taking place under closed thermodynamic conditions, while cement paste appears as a foam of hydration products transgressing the space between unhydrated clinker grains, with the total pore space between the fundamental blocks of hydrates (solid calcium-silicate hydrates) driving the continuous densification and hardening of the system.

biomineralization; cement hydration