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[EN] The aim of this experimental work was to study the porous structure of Ultra-High-Performance Fibre-Reinforced Concretes (UH) made with different fibre volume contents (0%, 1%, 2%) under several curing conditions (laboratory environment, 20 degrees C, 60 degrees C, 90 degrees C), comparing the results with those recorded for ordinary, high strength and very high strength concretes. Scanning electron microscopy, mercury intrusion porosimetry, thermogravimetry, water absorption and oxygen permeability tests were carried out. The results showed a low portlandite content in UH (in the order of 75% lower than in concrete C50) and a low degree of hydration, but they rise with curing temperature. These concretes have a very fine porous structure, with a high concentration of pores on the nanoscale level, below 0.05 mu m. Their porosity accessible to water is consequently around 7-fold lower than in conventional (C30), 6-fold lower than in high-strength (C50) and 4-fold lower than in very high-strength (C90) concretes. Their oxygen permeability is at least one order of magnitude lower than in C90, two orders of magnitude lower than in C50 and three orders of magnitude lower than in C30. The percentage of added steel fibre does not affect the UH porous structure ; This research was funded by Ministerio de Economia Y Competitividad (Agencia Estatal de Investigacion) of the Spanish Government, Grant number BIA2016-78460-C3-3-R ; Valcuende Payá, MO.; Lliso-Ferrando, JR.; Roig-Flores, M.; Gandía-Romero, JM. (2021). Porous Structure of Ultra-High-Performance Fibre-Reinforced Concretes. Materials. 14(7):1-18. https://doi.org/10.3390/ma14071637 ; S ; 1 ; 18 ; 14 ; 7

[EN] The corrosion resistance of ultra-high performance concrete (UH) made with different fibre contents and under distinct curing conditions was studied. No signs of carbonation were observed after 1 year of accelerated carbonation testing (3% CO2). The fibreless UHs¿ electrical resistivity was above 5000 ¿·m, although these values were 2-fold higher than a UH with 1% fibres and approximately 5-fold higher than a UH with 2% fibres. Concrete resistance to chloride penetration was also extremely high (the diffusion coefficient equalled 1.3·10¿13 m2/s) and curing temperatures of 60 °C or 90 °C improved even more these properties, while lack of curing made them slightly worse. Given these excellent properties, the corrosion rate in specimens submerged in chloride solution for 1 year was negligible (iCORR from 0.007 to 0.025 µA/cm2). These values remained stable with time, unlike the 50 MPa concrete at 2 months when iCORR starting to increase and was 12-fold higher after 1 year. The time estimated for corrosion onset in UH is on average about 150-fold higher than that of 50 MPa. ; Authors thank to the Spanish Government the financial support of project BIA2016-78460-C3-3-R and to the European Union¿s Horizon 2020 the financial support of ReSHEALience project (Grant Agreement No. 760824). Furthermore, authors would like to express their gratitude for the support of the Universitat Politecnica de Valencia. Funding for open access charge: CRUE-Universitat Politecnica de Valencia. The predoctoral scholarship granted to Josep Ramon Lliso Ferrando within the program "Formacion de Personal Investigador" from the Universitat Politecnica de Valencia (FPI-UPV-2018) is also gratefully acknowledged. ; Valcuende Payá, MO.; Lliso-Ferrando, JR.; Ramón Zamora, JE.; Soto Camino, J. (2021). Corrosion resistance of ultra-high performance fibre- reinforced concrete. Construction and Building Materials. 306:1-10. https://doi.org/10.1016/j.conbuildmat.2021.124914 ; S ; 1 ; 10 ; 306

A series of cratering experiments were performed where the response of the Ultra-High-Performance Fibre-Reinforced Concretes with various fibre volume fractions to the high- velocity projectile impact loading was investigated. It was found that the increment of the fibre volumetric fraction did not have a significant influence on the depth of the penetration, but it was very effective in reducing the crater area and volume.

<p>The main objective of this paper is to contribute to the development of ultra-high performance fibre reinforced concrete (UHPFRC) with respect to its effective fracture energy. Effective fracture energy was investigated in this paper considering different fibre volume fractions and different strain rates. It was concluded that the effective fracture energy is dependent on the strain rate. In addition, it was found that higher fibre volume fractions tend to decrease the sensitivity of the UHPFRC to increased strain rates.</p>

Semi-infinite targets of Ultra-High-Performance Fibre-Reinforced Concrete with various fibre volume fractions were subjected to the high-velocity projectile impact using in-service bullets. In this study, a variety of empirical and semi-analytical models for prediction of the depth of penetration and mass ejection were evaluated with respect to the experimental results. Models for the depth of penetration and spalling mass ejection were revisited and applied both with deformable and nondeformable projectiles parameters. The applicability of the prediction models was assessed through a statistical comparison of values from models with experimental results. The evaluation of the applicability was made through the newly proposed measure of a relative prediction accuracy for model selection and model estimation, which was verified with established statistical accuracy evaluations, such as accuracy ratio, logarithmic standard deviation and correlation coefficient. The best fit to the experimental readings was provided by newer semi-analytical models, which are incorporating additional concrete parameters beside compressive strength while the majority of older models failed to provide sufficient accuracy.

<p>This paper investigates the effective fracture energy of UHPFRC with various fibre volume fractions and various fibre aspect ratios. We have concluded that the effective fracture energy is dependent on both the fibre volume fraction and the fibre aspect ratio. In addition, we have found that both dependencies follow a linear trend.</p>

Last decades have been characterized by growing attention on sustainable development. The European Commission interest in this topic is evident considering the global agreements and the related massive investments that have been, and still are, carried out to guarantee a sustainable approach to global growth. A contribution to pursue this challenging goal is provided by the EUfunded ReSHEALience Project (GA n° 760824). ReSHEALience Project aims at developing Ultra High Performance Fibre Reinforced Concretes with enhanced durability (Ultra High Durability Concrete – UHDC) that will be characterized by at least 30% longer service life as compared to traditional concretes. The increase of durability will be analyzed also from a sustainability point of view taking into account all the environmental, economic and social impacts, associated to the longer life-cycle of the structures. ; Funded by the European Union Horizon 2020 research and innovation programme under GA No 760824. ; Peer reviewed

Thin plates made of Ultra-High-Performance Steel-Fibre-Reinforced Concrete (UHPSFRC) with textile Aramid fabrics were subjected to a projectile impact and its post-test damage was discussed. The damage degrees were the type of the response and crater surface, which was determined by using a 3D scanner. The most common type of ammunition, which is a 7.62 × 39mm calibre with a full-metal jacket and a mild-steel core, was used for all specimens.
It was verified experimentally that the UHP-SFRC with textile Aramid fabrics has a better ballistic performance in comparison with its counterpart made of the UHP-SFRC without any textile reinforcement. Also, it was verified that specimens with the point or segment interconnection threads between the front side textile fabrics and rear side textile fabrics have a higher resistance due to the better integrity of the monolithic UHP-SFRC mixture.

Generally, cement composites like high-performance concrete (HPC) are very brittle. The resistance to the impact loading of the HPFRC and the HPFRC reinforced by the textile reinforcement are compared in this article. The samples (0.56 × 0.1 × 0.1 m) were experimentally tested in three-point bending, by using horizontal impact machine. The better resistance of the textile reinforced HPFRC is obvious from the collected data (impact force, acceleration of hammer and acceleration of the tested sample).

Experimental studies play a crucial role in shedding light on the dynamic behaviour of structures under blast loading. However, high costs and complicated technical requirements, particularly for full-scale structures, are still huge disadvantages to conduct such a series of tests. Hence, the finite element method is much needed to provide supplementary information to previous experiments and to enable further parametric studies without testing. This article presents a numerical investigation carried out to understand the behaviour of ultra high performance fiber reinforced concrete (UHPFRC) panels under severe blast loading. The authors designed a subroutine with eight numbers of solution-dependent state variables, 32 mechanical constants, integrated with the Abaqus program to analyze the dynamic behaviour of UHPFRC against multiple blast impacts, using the Johnson-Holmquist 2 damage model incorporating both the damage and residual strength of the material. The subroutine was validated by comparing the simulation results with test results. For the purpose of estimating the structural response of the UHPFRC panel subjected to blast loading, other studying scenarios were considered by varying input parameters, including the thickness of the panel, stand-off distance, and steel reinforcement bar volume. The variations in deflection, strain, and damage of the UHPFRC panel, as well as the steel reinforcement strain, were also evaluated. Through important obtained results, the UHPFRC panel is strongly recommended for a protective barrier installed in the vicinity of critical infrastructure against severe blast loading

This paper summarizes the research that is being carried out at the Universities of Coimbra and Rio de Janeiro, on fibre reinforced concretes at high temperatures. Several high strength concrete compositions reinforced with fibres (polypropylene, steel and glass fibres) were developed. The results of compressive tests at high temperatures (300 °C, 500 °C and 600 °C) and after heating and cooling down of the concrete are presented in the paper. In both research studies, the results indicated that polypropylene fibers prevent concrete spalling.