BEFIB2012 – Fibre reinforced concrete Joaquim Barros et al. (Eds) © UM, Guimarães, 2012 TESTING THE FRESH AND HARDENED STATE PERFORMANCE OF STEEL FIBRE REINFORCED SELF-COMPACTING CONCRETE Liberato Ferrara * , Patrick Bamonte * , Alessio Caverzan * , Abdisa Musa 1 , Irem Sanal 2 * Department of Structural Engineering, Politecnico di Milano Piazza Leonardo da Vinci 32, 20133 Milano, Italy e-mail: liberato.ferrara@polimi.it , patrick.bamonte@polimi.it , caverzan@stru.polimi.it 1 Haramaya University, Ethiopia e-mail: abdisa.musa@mail.polimi.it , abmomu@gmail.com 2 Civil Engineering Department, Bogazici University, Bebek, Istanbul, Turkey e-mail: irem.sanal@boun.edu.tr Keywords: fibre reinforced SCC, fresh state performance, fibre dispersion and orientation, toughness. Summary: The fibre dispersing ability represents a key distinctive feature of the fresh state performance of a Steel Fibre Reinforced SCC (SFR-SCC) which has to be carefully assessed, also in the sight of its outcomes on the mechanical performance in the hardened state. In this paper, with reference to a typical SFR-SCC mix-composition, different methods to evaluate the resistance to static and dynamic segregation of fibres will be discussed and their results cross analyzed also in order to address a comprehensive testing methodology. Results obtained with reference to fresh state performance will be correlated to the fracture toughness properties in the hardened state, measured on specimens cast according to the same procedure employed for fresh state tests. This will allow a thorough evaluation of the correlation among fresh state performance, fibre dispersion and mechanical properties in the hardened state, furthermore enriching the meaningfulness, in a design oriented perspective, of material acceptance tests for quality control in the fresh state. The responsiveness and robustness of the proposed test methodologies will be finally widely assessed with reference to expected tolerances in the dosage of the mix constituents (water, cement, superplasticizer) which are mainly responsible of the performance in the fresh state. 1 INTRODUCTION The use of Steel Fibre-Reinforced Self-Compacting Concrete (SFR-SCC) has received a tremendous impulse in the very last years in an attempt to push forward the boundaries of high end structural applications of both Steel Fibre-Reinforced Concrete (SFRC) and Self-Compacting Concrete (SCC) technologies. The synergy between fibre-reinforced and self-compacting concrete has rapidly become a challenge for the construction industry, mainly in the field of prefabrication, which is generally more innovation prone. Dedicated studies have clearly demonstrated that the main advantage of incorporating fibres into self-compacting concrete is the achievement of a more uniform dispersion of fibres within structural elements, thanks to the elimination of compaction and vibration and to the rheological stability of the SCC matrix [1,2]. This requisite is of paramount importance to guarantee a reliable structural performance in FRC members. In fact, any improper compaction and placement, made more complex by the negative effects that fibres have on workability [3], may hinder the random dispersion of the fibres within a structural member. Spots with a reduced fibre dosage or no fibres at all act as flaws and trigger early failures by activating unpredictable mechanisms, that affect the load-bearing capacity and the structural performance as a whole, e.g. in terms of stiffness, fracture toughness, ductility, etc.