Markovic

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 the contrary of conventional steel fibre concretes, which contain only one type of fibre. The basic goal of combining short and long fibres is to improve the tensile strength by the action of short fibres on the one hand and on the other hand to improve the ductility by the action of long fibres. In this research project all important aspects needed for the development and application of HFC have been considered. A total of fifteen 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 the bridging of cracks by fibres was developed and successfully implemented for tensile softening response of HFC. Finally, the utilisation of HFC in the engineering practice was discussed, including a case-study on light prestressed long-span beams made of HFC.