Citius, altius, fortius/faster, higher, tougher: pushing ahead the boundaries of structural concrete through fiber-reinforced cementitious composites with adapted rheology

Fiber-reinforced self-compacting concrete (FR-SCC) combines the benefits of highly flowable concrete in the fresh state with the enhanced performance in the hardened state in terms of crack control and fracture toughness provided by the dispersed fiber reinforcement. Thanks to the suitably adapted rheology of the concrete matrix, it is possible to achieve a uniform dispersion of fibers, which is of the foremost importance for a reliable performance of structural elements. Balanced viscosity of concrete may also be helpful to drive the fibers along the concrete flow direction. An ad hoc designed casting process may hence lead to an orientation of the fibers “tailored” to the intended application, which is along the anticipated directions of the principal tensile stresses within the structural element when in service. This converges toward a “holistic” approach to the design of structure made with highly flowable/self-consolidating fiber-reinforced concrete (FRC), which encompasses the influence of fresh state performance and casting process on fiber dispersion and orientation, and the related outcomes in terms of hardened state properties. A thorough understanding is required of the mechanisms underlying the connection between mix-design and fresh state performance, on one hand, and the dispersion and orientation of the fibers on the other hand, also in the context with monitoring and prediction to achieve the anticipated structural performance. In this framework, this article, after a review of the authors’ main research results on the aforementioned topics, will focus on the research needs which have to be urgently tackled in order to address the use of this kind of advanced cement-based materials for high-end structural applications.