A comprehensive methodology to test the performance of Steel Fibre Reinforced Self-Compacting Concrete (SFR-SCC)

The fibre dispersing ability represents a key distinctive feature of the fresh state performance of a Steel Fibre Reinforced Self Compacting Concrete (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 (containing 50 kg/m3 hooked steel fibres 35 mm long with an aspect ratio equal to 65), different methods to evaluate the resistance to static and dynamic segregation of fibres have been discussed and the results cross analyzed also in order to address a comprehensive testing methodology and to assess its reliability. Among them, cylinder segregation test (for static segregation), channel flow test (for dynamic segregation) as well as the slump flow test: as a matter of fact, through the latter, by measuring the content of fibres in different concentric circular areas of the patty, information on dynamic segregation could be assessed. This test method represents the extension to FR-SCC of a methodology already developed for plain SCC. Results obtained from fresh state performance tests have been finally 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 set of data allows 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 influence has been finally assessed of expected tolerances in the dosage of the mix constituents (water, cement, superplasticizers) on the performance in both the fresh and hardened state, as correlated through fibre dispersion related issues.