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This work aims to investigate the effect of a wide range of oblique impacts of the 7.62-mm-caliber projectile on the slim high-performance fiber-reinforced concrete (HPFRC) panels. The trajectory of the projectile, the depth of penetration, and the extent and type of plate damage are discussed in detail. The numerical models developed in commercially available software are also included in this work to support and supplement the experimental data. In the model, each fiber is modeled separately, leading to a more realistic prediction of the material behavior. The analyses identified four basic scenarios for projectile impact: total plate perforation by the projectile core, core penetration combined with or without rear HPFRC material detachment, and ricochet. The results show that the numerical model can effectively and accurately predict the impact response and damage morphologies of the slim HPFRC panel. [ABSTRACT FROM AUTHOR]

Ultra-high-performance fibre-reinforced concrete (UHPFRC) is an advanced cementitious composite with enhanced mechanical and durability properties that outperforms conventionally used concretes in many ways. Such a material with certain properties and specifications is well suited for energy absorption facade panels and key elements of building structures that may be exposed to impacts or blast loads. It can be stated that the resistance of civil infrastructure is strongly related to the energy absorption capacity of concrete, which is the main material property that benefits from fibre reinforcement. The aim of this study is to investigate the fracture energy of the UHPFRC with various fibre aspect ratios. Different behaviour of UHPFRC in terms of fracture energy can be expected for various aspect ratios of fibres, as the fibres are the key component of the UHPFRC that result in enhanced energy absorption and dissipation capacity. The aspect ratios (length-to-diameter) of fibres used in this study ranged from 50:1 to 108:1. It was verified experimentally that the fracture energy increases as the aspect ratio increases. In addition, it was found that the dependence of the fracture energy on the aspect ratio of the fibres tends to follow a linear trend. The results provided in the present study can serve as valuable information for verifying material models, and also for design purposes. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this paper is to describe mix design of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) and its response to deformable and non-deformable projectile impact. UHPFRC represents a class of cementitious composite in which stress–strain response in tension undergoes strain hardening behaviour accompanied by multiple cracking, leading to a high strain prior to failure. The compressive strength of the resulting UHPFRC mixtures exceeded 130 MPa and direct tensile strength was in the range of 10 MPa. Several UHPFRC mixtures with different content of fibers were subjected to deformable projectile impact. It was found that specimens containing 2% of fibers by volume have optimal resistance against deformable projectile impact. Slabs containing 2% of fibers were further subjected to a non-deformable projectile impact. In addition, response of slabs made of traditional fiber reinforced concrete (FRC) is discussed. The magnitude of the damage was assessed based on the penetration depth, crater diameter and loss of mass. [Copyright &y& Elsevier]

Abstract: Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) is currently one of the biggest challenging issues in modern concrete technology. The UHPFRC represents a concrete with improved durability and strength, which is significantly higher than in conventional normal strength concrete. This may result in reduced cross-sections and as a consequence smaller dead-load of the structure. The uniaxial compressive cylinder strength of UHPFRC used in this study exceeded 150MPa and the uniaxial direct tensile strength exceeded 10MPa. Several UHPFRC mixtures with different content of fibers were subjected to deformable projectile impact. The ogive-nose projectile weighed 8.04 grams and its average velocity was determined to be 710 m/s. It was shown that plain UHPC specimen failed in the brittle manner which caused that the slab split into several pieces. Further, it was demonstrated that addition of steel micro fibers enhanced the resistance to deformable projectile impact and it was specified that specimens containing 2% of fibers by volume have optimal resistance against impact loading. In addition, response of slabs made of conventional fiber reinforced concrete (FRC) and normal strength concrete (NSC) was studied for comparison. The magnitude of the damage was assessed based on the penetration depth, crater diameter and mass loss. Experimental results clearly showed that implementation of high strength steel micro fibers significantly increased the resistance to projectile impact. It was stated, that UHPFRC has much better resistance to projectile impact in comparison to conventional FRC. [Copyright &y& Elsevier]

Abstract: This paper describes experimental investigations of various mechanical properties of Ultra High Performance Fiber Reinforced Concrete (UHPFRC). The UHPFRC is a modern cementitious composite containing a large amount of cement, both reactive and nonreactive very fine particles, chemical admixtures and short high strength steel fibers. This type of concrete has superior durability and excellent mechanical properties. In this paper an UHPFRC containing 2% of fibers by volume with a compressive strength exceeding 150MPa is presented. In this study detailed descriptions of the measurements of compressive strength, bending strength, direct tensile strength, fracture energy and modulus of elasticity are given. The study provides a comparison of the above mentioned UHPFRC properties with high performance concrete, fiber reinforced concrete and conventional structural concrete. The results indicate excellent performance of UHPFRC in all categories. The biggest difference to ordinary concretes can be seen in tensile behavior, where its response in tension exhibits strain hardening accompanied with multiple cracking followed by tensile softening. The direct tensile strength of the studied material is 10MPa and its fracture energy is 5 times higher than that of conventional fiber reinforced concrete. It is believed, that such type of material is the future of concrete industry, it will allow executing higher, more effective structures with excellent durability. [Copyright &y& Elsevier]