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The interaction of ultrahigh-performance concrete (UHPC) and normal-strength concrete (NSC) is one of the main issues for strengthening conventional concrete structures or other applications where NSC and UHPC are interrelated. UHPC stands out for its strength and durability, while NSC is significantly inexpensive and easier to work with. Efficiently designed structures can exploit the advantages of both mixtures. At the interface of these materials in newly designed structures, the formwork can be modified at the interface to give the concrete surface sufficient roughness and thus cohesion as required. This improves both the tensile and shear strength of the contact resulting in the enhanced capacity of the composite structure. In this study, a button foil was inserted into the formwork for the UHPC and then a part of NSC was made. The shear strength of the interface without any stress component in the transverse direction was measured on small-scale samples. It was to justify the possibility of the use of this interface in real constructions such as beams and columns. The main objective of further research is to design a composite beam using a UHPC shell as formwork for NSC and protrusions at the interface. It is expected that the U-shaped shell made of the UHPC could significantly contribute to the load-bearing capacity of the resulting composite NSC–UHPC structure and also to its enhanced durability. In addition, if the NSC is enclosed in a shell of UHPC, it can be made from various secondary materials, therefore it can decrease cement consumption by more than 50%. [ABSTRACT FROM AUTHOR]

The article presents a mobile anti-vehicle barrier created from a high-performance fibre-reinforced concrete, which resembles a historical design of the Czech Hedgehog barrier. The performance of this design when subjected to a moderate velocity vehicle impact was evaluated. A preliminary crash test provided basic data to perform an optimisation of the design using numerical simulations conducted in LS-DYNA. Several key observations were made regarding the crucial role of the barrier-surface interactions and overall barrier behaviour. Based on the simulations, improved geometry of the barrier was proposed and subjected to more full-scale crash tests with various barrier placements. The improved barrier design was able to stop an ordinary road vehicle weighing 1300 kg moving with a velocity of 48 km/h while retaining beneficial characteristics, most importantly low weight. [ABSTRACT FROM AUTHOR]

The efficiency of fibre reinforcement in concrete can be drastically increased by orienting the fibres using a magnetic field. This orientation occurs immediately after pouring fresh concrete when the fibres can still move. The technique is most relevant for manufacturing prefabricated elements such as beams or columns. However, the parameters of such a field are not immediately apparent, as they depend on the specific fibre reaction to the magnetic field. In this study, a numerical model was created in ANSYS Maxwell to examine the mechanical torque acting on fibres placed in a magnetic field with varying parameters. The model consists of a single fibre placed between two Helmholtz coils. The simulations were verified with an experimental setup as well as theoretical relationships. Ten different fibre types, both straight and hook-ended, were examined. The developed model can be successfully used to study the behaviour of fibres in a magnetic field. The fibre size plays the most important role together with the magnetic saturation of the fibre material. Multiple fibres show significant interactions. [ABSTRACT FROM AUTHOR]

This paper deals with the description, measurement, and use of electromagnetic properties of ferromagnetic fibres used as dispersed fibre reinforcement in composite mixtures. Firstly, the fibres' magnetic properties are shown, and a method of measuring the hysteresis loop of fibres is proposed. The results from the measurements are presented and a discussion of the influence of measured parameters on the fibres' orientation in a magnetic field is performed. Furthermore, methods of non-destructive estimation, of their amount and orientation in the composite specimens, are discussed. The main experimental goal of this paper is to show the relationship between this non-destructive method's results and the destructive flexural strength measurements. The method is sensitive enough to provide information related to fibre reinforcement. [ABSTRACT FROM AUTHOR]

We aim at determining the value of minimal magnetic induction for magnetic orientation of fibres in cementitious composite in a given mixture and establish the effect of the magnetic field shape on the final mechanical properties. The magnetic orientation is a suitable method to ensure the required direction of steel ferromagnetic fibres in the composite. The strength of the magnetic field (magnetic induction) and rheology of the fresh mixture play a crucial role in the magnetic orientation. A special device generating alternating and direct magnetic fields with different magnetic inductions was built to determine the minimal magnetic induction for the given mixture. Moreover, the effects of using alternating magnetic field are explored. The used magnetic inductions are 60 mT, 80 mT, 100 mT and 120 mT. The nondestructive inductive measuring method is applied to confirm the orientation of fibres in the hardened composite. The effect of the shape of the magnetic field and magnetic induction on flexural strength is presented. Moreover, the effects of using the alternating or direct magnetic field on the microstructure are explored using a scanning electron microscope. • Magnetic orientation of fibres was examined. • Alternating magnetic field proves to be suitable for fibre orientation. • Scanning electron microscopy (SEM) confirmed that microstructure is not affected. • Magnetic orientation increased flexural strength by up to 50%. • Results of the non-destructive inductive method correlate well with the strength. [ABSTRACT FROM AUTHOR]