" In the research project presented in this book, an innovative type of fibre concrete is developed, which improved both the tensile strength and the ductility: the Hybrid-Fibre Concrete (HFC). The expression 'Hybrid' refers to the 'hybridisation' of fibres: short and long steel fibres were combined together in one concrete mixture. This is opposite to conventional steel fibre concretes, which contain only one type of fibre. The basic goal of combining short and long fibres is from one side to improve the tensile strength by the action of short fibres, and from the other side to improve the ductility by the action of long fibres.
In this research project, all important aspects needed for the development and application of Hybrid-Fibre Concrete have been considered. In total 15 mixtures, with different types and amounts of steel fibres were developed and tested in the fresh state (workability) as well as in the hardened state (uniaxial tensile tests, flexural tests, pullout tests of single fibres and compressive tests). A new analytical model for bridging of cracks by fibres was developed and successfully implemented for tensile softening response of HFC. At the end, the utilisation of HFC in the engineering practice was discussed, including a case-study on light prestressed long-span beams made of HFC.
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