Although concrete when subject to fire performs very well, its behaviour and properties change dramatically under high temperature due to damaged microstructure and mesostructure. As fibre reinforced concrete (FRC) represents a complex material composed of various components with different response to high temperature, to determine its behaviour and mechanical properties in fire is a demanding task. The presented paper provides a summary of findings on the fire response of fibre FRC. Namely, the information on steel fibre reinforced concrete (SFRC), synthetic fibre reinforced concrete and hybrid (steel + synthetic) fibre reinforced concrete have been gathered from various contributions published up to date. The mechanical properties including the melting point and ignition point of fibres affect significantly the properties of concrete composites with addition of fibres. The combination of steel and synthetic fibres represents a promising alternative how to ensure good toughness of a concrete composite before heating and improve its residual mechanical behaviour and spalling resistance as well as the ductility after heating. While synthetic fibres increase concrete spalling resistance, steel fibres in a concrete mix leads to an improvement in both mechanical properties and resistance to heating effects.

3D concrete printing technology (3DCP) is a relatively new technology that was first established in the 1990s. The main weakness of the technology is the interface strength between the extruded layers, which are deposited at different time intervals. Consequently, the interface strength is assumed to vary in relation to the time of concrete casting. The proposed experimental study investigated the behavior of a hardened concrete mixture containing coarse aggregates that were up to 8 mm in size, which is rather unusual for 3DCP technology. The resulting direct tensile strength at the layer interface was investigated for various time intervals of deposition from the initial mixing of concrete components. To better understand the material behavior at the layer interface area, computed tomography (CT) scanning was conducted, where the volumetric and area analysis enabled validation of the pore size and count distribution in accordance with the layer deposition process. The analyzed CT data related the macroscopic anisotropy and the resulting crack pattern to the temporal and spatial variability that is inherent to the additive manufacturing process at construction scales while providing additional insights into the porosity formation during the extrusion of the cementitious composite. The observed results contribute to previous investigations in this field by demonstrating the causal relationships, namely, how the interface strength development is determined by time, deposition process, and pore size distribution. Moreover, in regard to the printability of the proposed coarse aggregate mixture, the specific time interval is presented and its interplay with interface roughness and porosity is discussed.

Long-term traffic restrictions belong to the key disadvantages of conventional cast-in-plane concrete pavements which have been used for technical structures such as roads, parking place and airfield pavements. As a consequence, the pressure is put on the development of such systems which have short construction time, low production costs, long-term durability, low maintenance requirements etc.. The paper presents the first step in the development of an entirely new precast concrete pavement (PCP) system applicable to airfield and highway pavements. The main objective of the review of PCP systems is to acquire a better understanding of the current systems and design methods used for transport infrastructure. There is lack of information on using PCP systems for the construction of entirely new pavements. To most extensive experience is dated back to the 20 th century when hexagonal slab panels and system PAG were used in the Soviet Union for the military airfields. Since cast-in-situ pavements became more common, the systems based on precast concrete panels have been mainly utilized for the removal of damaged sections of existing structures including roads, highways etc.. Namely, it concerns Fort Miller Super Slab system, Michigan system, Uretek Stitch system and Kwik system. The presented review indicates several issues associated with the listed PCP systems and their applications to the repair and rehabilitation of existing structures. Among others, the type of manufacturing technology, particularly the position of slots for dowel bars, affects the durability and performance of the systems. Gathered information serve for the development of a new system for airfield and highway pavement construction.

Generally speaking, adding a certain amount of steel fibres to a concrete mixture improves its mechanical properties. Currently, a lack of information considering tensile and post cracking behaviour of FRC at elevated temperatures is an issue to be faced. An experimental study of steel fibre reinforced concrete, also containing polymer fibres (FRC), subjected to high temperature is presented herein. Compressive strength, split tensile strength and ultimate bending strength were evaluated. Specimens were heated by the use of ceramic heaters and repacked for testing consequently. A finite-element based model was developed to predict the temperature distribution inside a specimen during both the heating and the cooling process.