Design with Highly Flowable Fiber-Reinforced Concrete: Overview of the Activity of fib TG 8.8

Self-compacting fiber-reinforced concrete (SC-FRC) 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 wirelike 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 stressed within the structural element when in service. This converges towards a "holistic" approach to the design of structure made with highly flowable/self-consolidating 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. The fib task Group 8.8 "Structural design with highly flowable concrete", sub-group fiber concrete, appointed in April 2009, aims at drafting recommendations to facilitate and spread the use of these innovative materials, merging together research findings and practical experience.