Behavior Of Ultra-high Performance Fiber-reinforced Concrete Research Articles

Interface Shear Behavior of Ultrahigh-Performance Fiber-Reinforced Concrete Using Digital Image Correlation Technique

Interface Shear Behavior of Ultrahigh-Performance Fiber-Reinforced Concrete Using Digital Image Correlation Technique

Fatigue behavior of ultrahigh-performance fiber-reinforced concrete as an alternative for flexible pavement rehabilitation

The fatigue behavior of ultrahigh-performance fiber-reinforced concrete for use as an overlay in the typical rehabilitation of a flexible pavement structure was analyzed in this study. Compression and four-point bending tests were carried out to characterize the concrete mechanical properties. Fatigue tests were performed using the four-point method, and test beams were evaluated without precracking. The specimens were subjected to constant-amplitude sinusoidal loading with a loading frequency of 10 Hz. The magnitude of each stress level was calculated as a percentage of the initial crack stress. The following results were obtained for the concrete: a compressive strength of 127.1 MPa, bending yield strength of 6.23 MPa, maximum bending stress of 9.89 MPa, Young's modulus of 38.1 GPa, and dynamic modulus of 28.6 GPa. The stress and strain at one million cycles were 6.0 MPa and 166 μm/m, respectively. The fatigue test results indicated superior properties of the ultrahigh-performance concrete to those of similar materials.

Estimating the Tensile Strength of Ultrahigh-Performance Fiber-Reinforced Concrete Beams

The tensile behavior of ultrahigh-performance fiber-reinforced concrete (UHPFRC) depends on the dispersion and orientation of steel fibers within the concrete matrix. The uneven dispersion of randomly oriented steel fibers in concrete may cause differences in the tensile behavior between material testing specimens and beams. Therefore, in this study, the tensile behavior was investigated by fitting the analysis result of the moment-curvature curve to the experimental result of a UHPFRC beam. To this end, three UHPFRC mixtures with different compressive strengths were fabricated to test the material properties and flexural behavior of UHPFRC beams. Both a single type of steel fiber and a combination of steel fiber types were used with volume fractions of 1.0% and 1.5%, respectively, in the three mixtures. Based on the design recommendations, the material properties of UHPFRC were modeled. The results ultimately show that by fitting the analysis results to the experimental results of the moment-curvature curves, the tensile strength of UHPFRC beams can be reasonably estimated.

Effect of curing temperature on the behaviour of UHPFRC at elevated temperatures

Ultra-high performance fibre reinforced concrete is one of the construction materials that is still in need of more research to evaluate its performance under fire, particularly regarding explosive spalling. In this study, the effect of curing temperature on the fire resilience of ultra-high performance fibre reinforced concrete (UHPFRC) has been tested. In particular, the influence of cold (20 °C) and hot (90 °C) water curing temperatures on the performance of UHPFRC exposed to elevated temperatures has been investigated. Beams, cured in cold water and in hot water were tested under the standard ISO 834 heating regime. The test results showed that the beam cured in hot water spalled significantly more than the beam cured in cold water. The study further investigated the influence of curing temperature on the residual strength of UHPFRC (containing both steel and polypropylene fibres). The cube elements were heated at eight selected temperatures between 200 °C and 900 °C. The cold-cured concrete exhibited higher relative residual strength at all temperatures. The results further showed that UHPFRC have high strength retention up to 600 °C. The residual peak strength for both the cold and the hot-cured occurred at 400 °C.

UHPFRC for concrete repair

As part of the St. Lawrence Seaway lock maintenance, the current practice is to perform concrete repairs entirely with reinforced concrete, using either ordinary concrete or high performance concrete (HPC) mixtures. However, with the recent advances in the field of ultra-high performance fiber-reinforced concrete (UHPFRC), the use of this new material is considered in view of improving the overall performance of repairs. The goal is to implement repairs capable of dissipating a lot of energy before breaking when a ship hits a concrete lock wall. Numerous rehabilitation materials and methods have been experimented in the past. They all were unsuccessful due to inadequate shear and impact strength characteristics of the repair materials used. These needs can be efficiently fulfilled with UHPFRC, with their superior mechanical properties and very high energy-dissipation ability. To analyze the in-situ behavior of UHPFRC, two main mixture designs were investigated: a 160-MPa mixture containing 3% of steel fibers and a 120-MPa mixture containing 3.5% of a steel fiber blend. Thick repairs with average depths of 700 mm were carried out during the winter shut down period, in very harsh climatic conditions (-12 °C, gusty wind). The performance exhibited by the repairs after a full year shows that UHPFRCs can withstand very effectively the impacts from the transiting vessels

Effect of Fibre Length on the Fracture Energy of UHPFRC

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.

Effects of thermal damage on physical properties and cracking behavior of ultrahigh-performance fiber-reinforced concrete

In this work, we study the impact of thermal damage on the physical and mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC), especially on their cracking process under compressive loading. Four mixtures of UHPFRC were prepared using identical composition but reinforced with different types of fibers: mineral fibers (Steel or Wollastonite) or organic fibers (PP or PVA) and compared with that without fibers (UHPC). To induce a thermal damage on UHPFRC, the samples were subjected to temperatures ranging from 150 to 400 °C. After each degradation stage, the gas permeability and the P-wave velocity were measured. The mechanical behavior under loading has been studied using a uniaxial compression test which combines the gas permeability and the acoustic emission measurement. The results show that the melting of organic fibers at approximately 180 °C builds a tunnel across the cement paste and increases brutally the gas permeability. At 400 °C treatment, a decrease of compression strength by 30 % and of Young modulus by approximately 60 % was observed. However, we can see that the thermal damage results a decrease in the threshold of initial cracking (σ k−ci) and that of unstable cracking (σ k−pi), and this can be explained by the initiation of new cracks and their coalescence.

Laboratory Testing of GFRP-RC Panels with UHPFRC Joints of the Nipigon River Cable-Stayed Bridge in Northwest Ontario, Canada

AbstractThis study investigates the behavior of ultrahigh-performance fiber-reinforced concrete (UHPFRC) joints between precast concrete panels reinforced with glass-fiber-reinforced polymer (GFRP) bars that are being used in the first cable-stayed bridge in northwest Ontario, Canada (Nipigon, Nipigon River Bridge). The test panels, which simulated the deck panels of the Nipigon River Bridge, were fabricated at the same precast facility in Ontario and delivered to the University of Sherbrooke for flexural testing until failure. The test matrix included eight panels measuring 3,000 mm long × 1,000 mm wide × 220 mm thick. The tests included three reference specimens without structural joints (one reinforced with steel bars and two reinforced with GFRP bars) and five jointed specimens (one reinforced with steel bars and four reinforced with GFRP bars). The structural joint width was a constant 220 mm for all jointed specimens. The specimens were tested in a cantilever-panel setup with the UHPFRC joint subjec...

A Method of Measuring the Displacement of an Ultra-High-Performance Fiber-Reinforced Concrete by Means of Unbound Gages

A study on Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) required accurate continuous displacement measurements to fully understand specimen compressive and split tensile behavior. From uniaxial compressive testing, load, and displacement data was acquired to develop specimen specific stress–strain diagrams from which the modulus of elasticity and strain at ultimate capacity of the material were found. Thus, a device suitable to measure the displacement and crack width opening was required during testing to gain knowledge of the behavior of UHPFRC subjected to compressive and tensile loads. The device normally used to measure average displacement is typically not used for ultimate strain conditions because of the potential LVDT damage from the often explosive compression failure of concrete specimens. Hence, this study investigated the use of Local Deformation Transducers (LDTs), which consists of strain gages attached at mid-length on a narrow strip of highly flexible and resilient material. Data collected from these gages corresponded well with UHPFRC test data collected from other institutions using more complex methods and proved to be a reliable source of measuring displacements with the intent of identifying modulus of elasticity, and concrete strains at first crack, and ultimate capacity for an UHPFRC.