Traditional fiberconcrete structures have fibres in the mix oriented in all spatial directions, distributed in the structural element volume homogenously, what not easy to obtain in practice. In many situations, structurally more effective is the insertion of fibres into the concrete structural element body by forming layers, with a predetermined fibre concentration and orientation in every layer. In the present investigation, layered fibre concrete is under investigation. Short steel fibres were attached to flexible warps with the necessary fibres concentration and orientation. Warps were placed into the prismatic mould separating them by concrete layers without fibres. Prisms were matured and tested under four-point bending. The bending-affected mechanical behaviour of cracked fibre concrete was simulated numerically by using a developed structural model. Comparing the simulation results with experimental data, material micromechanical fracture mechanisms were analysed and evaluated.

Fibers are usually used in High Performance Concrete with a purpose to increase bending strength and ductility. Important properties are the peak value of bearing stress (strength) and post-cracking behavior of bended element. In the framework of an experimental part, Ultra High Performance mix compositions were prepared using intensive mixer. Short steel fibers and carbon micro fibers in amount of 1% by volume, as well as its combination were used for cement matrix reinforcing. Results of compressive and bending tests proved an increase of strength value in the case of use both steel and carbon fibers. Carbon fibers were decreased the effect of explosive collapse of the UHPC cement matrix, at the same time still brittle bending behavior was take place. Steel fibers considerably improved bending ductility thanks to a pull-out mechanism of steel fibers. The best results were achieved in the case of combined application of both carbon and steel fibers.

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Innovations in the construction industry require new and efficient materials, like ultra-high performance concrete (UHPC), that allows to develop and engineer unprecedented construction solutions. Aggregate packing gives a significant contribution to the final properties of concrete design and especiallyultra-high performance concrete. High-quality coarse aggregates (0-1.25mm) of local origin were used to investigate the packing density, consistency and compressive strength of ultra-high performance concrete for application in advanced prefabricated concrete products (facades, balconies, stairs, structural elements). Several sources of high-quality quartz sand pits in the Baltic state region were evaluated and fractioned quartz sand from Lithuanian company AB Anykščių Kvarcas was chosen for experiments. Optimization of the packing density was performed using different experimental methods: Punkte test and ICT testing. Wet and dry experimental methods of assessing void volume in the coarse aggregate mix were used. Different mixes of coarse aggregates were prepared and optimal paste/aggregate proportion was found to deliver necessary fresh concrete flowing properties and hardened concrete compressive strength of the final mix. Conclusions were made on possibility and feasibility to use coarse aggregates of local origin for the development of cost-efficient ultra-high performance concrete mix design for use in advanced prefabricated concrete products.