Behavior Of High Performance Fiber Research Articles

Setting Time of Granite Powder Blended Banana Fibre Reinforced High Performance Concrete

The investigation is intended to analyse the variations in setting time behaviour of high performance fibre reinforced concrete (HPFRC) after adding granite powder as substitute for cement. The replacement of cement by granite powder was consider at the rate of 0, 5, 10, 15 and 20%. In order to improve the performance of concrete, banana fibres are added in concrete at 0.25, 0.5, 0.75, 1.0, and 1.25% by weight of cement. High strength concrete with M50 grade was designed and investigated in this study. The investigation was carried out in two stages, the stage one was predicting the optimum level of adding banana fibre based on the strength performance and the stage two was evaluating the variations in setting time performance of hardened concrete due to addition of granite powder. The setting time of concrete was conducted using penetration resistance test as per IS: 8142-1976. The slump value of the HPFRC was maintained by 80-100 mm and the dosage of superplasticizer was modified accordingly without varying the w/c ratio. Based on the results obtained in this investigation, 1% banana fibre was taken for developing the fibre reinforced concrete without affecting the 28 days compressive strength. The substitution of granite powder beyond 15% increases the setting time significantly and also affect the strength of HPFRC. The relationship between the setting time and 28 days compressive strength was predicted.

Ductile behavior of high performance fiber reinforced cementitious composite (HPFRCC) frames

High performance fiber-reinforced cementitious composite (HPFRCC) materials exhibit strain-hardening behavior under tensile loading. Therefore, experimental studies were conducted to assess their structural performance and to compare them with normal concrete in reinforced concrete frames. The experimental results for reinforced concrete, reinforced composite, and reinforced HPFRCC frames with fixed foundation are presented herein. They indicate that using HPFRCC materials, instead of normal concrete in RC frames, increased the ultimate load, ultimate deflection, ductility ratio, and plastic hinge characteristics of frames. A 3D nonlinear numerical model was developed also, using the finite element (FE) method, and analytical models calibrated with experimental results and new data were generated. A good agreement between experimental and numerical results was observed.

Mechanical Properties of Fiber Reinforced Lime-Based Mortars Evaluated from Four-Point Bending Test

In the study, the bending behavior of high-performance fiber reinforced lime-based mortars is experimentally investigated using four-point bending test. From the experimental data, the influence of the mortar’s composition on its stiffness, cracking strength and ultimate strength are investigated. It is also studied, whether the response has strain-softening or strain-hardening character and whether the material exhibits multiple cracking. Such behavior is very important for the durability of the material, because it allows carrying load during imposed deformations (due to thermal effects, movements of foundations, seismicity, etc.). The number of formed cracks is examined using digital image correlation method. The mortar composition is considered with two types of binder (pure lime, lime-metakaolin), with two types of polyvinyl alcohol fibers in four volume fractions (0.5÷2.0%). As the reference, we consider two sets of specimens made of plain mortar without fiber reinforcement.

Effect of mineral admixtures and steel fiber volume contents on the behavior of high performance fiber reinforced concrete

High Performance Fiber Reinforced Concrete (HPFRC) is a structural material with advanced mechanical properties. The structural design of HPFRC members is based on the post-cracking residual strength provided by the addition into the mix of the fibers. Moreover, the addition of different types of mineral admixtures influences the overall behavior of this material. In order to optimize the performance of HPFRC in structural members, it is necessary to evaluate the mechanical properties and the post-cracking behavior in a reliable way. As a result, an experimental study on six different sets of HPFRC specimens was carried out. The main parameters that varied were the fiber volume content and the types of mineral addition. The behavior in compression, in flexural tension and the shrinkage properties were evaluated and critically analyzed in order to give a guide for structural use.The results showed that by adding high fiber volume content and the Algerian blast furnace slag into the mix, the HPFRC material obtained has a very good performance and it is suitable for use in practice.

Deformation behavior of high performance fiber reinforced cementitious composite prepared with asphalt emulsion

A novel engineered cementitious composite (ECC) was prepared with the complex binder of Portland cement and asphalt emulsion. By adjusting the amount of asphalt emulsion, different mixture proportions were adopted in experiments, including four-point bending test, compressive test, and scanning electric microscopy (SEM). The SEM observation was conducted to evaluate the contribution of polyvinyl alcohol (PVA) fiber and asphalt emulsion to the composite toughening mechanism. The tests results show that the most remarkable deflection-hardening behavior and saturated multiple cracking are achieved when the content of asphalt emulsion is 10%. However, excessive content of asphalt emulsion causes severe damages on the deformation behavior as well as loss in compressive strength of the mixture. SEM observation indicates that the influence of asphalt emulsion on the fiber/matrix interfacial property changes the dominant fiber failure type from rupture into pull-out mode, and thus causes beneficial effects for strain-hardening behavior.

The Study of Steel Fiber Reinforced Concrete Durability Based on Damage Mechanics

In order to substitute steel reinforcement with steel fiber reinforced concrete, this paper studied steel fiber reinforced concrete durability based on damage mechanics. During recent years, steel fiber reinforced concrete has gradually advanced from a new, rather unproven material to one which has now attained acknowledgment in numerous engineering applications. The use of randomly distributed short fibers to improve the physical properties of a brittle or quasi-brittle matrix is an old concept. Most of the steel fiber reinforced concrete durability research just to solve a specific problem and no system of the structure performance degradation in certain circumstances. A formulation to model the mechanical behavior of high performance fiber reinforced cement composites with arbitrarily oriented short fibers. The formulation can be considered as a two scale approach, in which the macroscopic model, at the structural level, takes into account the micro-structural phenomenon associated with the fiber-matrix interface bond/slip process.

High strain rate effects on direct tensile behavior of high performance fiber reinforced cementitious composites

Direct tensile behavior of high performance fiber reinforced cementitious composites (HPFRCCs) at high strain rates between 10s−1 and 30s−1 was investigated using strain energy frame impact machine (SEFIM) built by authors. Six series of HPFRCC combining three variables including two types of fiber, hooked (H) and twisted (T) steel fiber, two fiber volume contents, 1% and 1.5%, and two matrix strengths, 56MPa and 81MPa, were investigated. The influence of these three variables on the high strain rate effects on the direct tensile behavior of HPFRCCs was analyzed based on the test results. All series of HPFRCCs showed strongly sensitive tensile behavior at high strain rates, i.e., much higher post cracking strength, strain capacity, and energy absorption capacity at high strain rates than at static rate. However, the enhancement was different according to the types of fiber, fiber volume content and matrix strength: HPFRCCs with T-fibers produced higher impact resistance than those with H-fibers; and matrix strength was more influential, than fiber contents, for the high strain rate sensitivity. In addition, an attempt to predict the dynamic increase factor (DIF) of post cracking strength for HPFRCCs considering the influences of fiber type and matrix strength was made.

Investigating direct tensile behavior of high performance fiber reinforced cementitious composites at high strain rates

This research reported the process of measuring direct tensile stress versus strain response of high performance fiber reinforced cementitious composites (HPFRCCs) at high strain rates between 10s−1 and 40s−1. High rate tensile tests were performed using a strain energy frame impact machine (SEFIM) built by authors. The stress history of HPFRCC at high rates was estimated from two strain gauges attached on two sides of a transmitter bar while the strain history was obtained by analyzing the sequential images recorded using a high speed camera. HPFRCCs exhibited strong rate sensitivity, i.e., their tensile parameters, including post cracking strength, strain capacity, peak toughness, and number of cracks, were significantly enhanced as the strain rate increased although the enhancement was different according to the types of fiber. The source of the dynamic enhancements in the tensile parameters of HPFRCCs was discussed.

Dynamic tensile behaviour of high performance fibre reinforced cementitious composites after high temperature exposure

The uniaxial tension behaviour of high performance cementitious composites subjected to high strain rates after high temperature exposure has never been investigated. The material investigated was a steel fibre reinforced mortar. Straight low carbon steel micro-fibres were used. The fibre content was 1.25% by volume and the mix design guaranteed a self compacting mixture. The main purpose of the research was to highlight the role of thermal damage in uniaxial tension at low and high strain rate loadings. Looking in particular at peak strength and post-peak toughness the results show that, in low strain rate tests after high temperature exposure up to 600°C, the thermal damage progressively reduces the toughness and weakly increases the strength; at high strain rate the peak strength significantly increases in comparison with low strain rate one for all the temperature investigated, while the toughness for growing temperature progressively decreases.

A micromorphic model for steel fiber reinforced concrete

A new formulation to model the mechanical behavior of high performance fiber reinforced cement composites with arbitrarily oriented short fibers is presented.The formulation can be considered as a two scale approach, in which the macroscopic model, at the structural level, takes into account the mesostructural phenomenon associated with the fiber–matrix interface bond/slip process. This phenomenon is contemplated by including, in the macroscopic description, a micromorphic field representing the relative fiber–cement displacement. Then, the theoretical framework, from which the governing equations of the problem are derived, can be assimilated to a specific case of the material multifield theory.The balance equation derived for this model, connecting the micro stresses with the micromorphic forces, has a physical meaning related with the fiber–matrix bond slip mechanism. Differently to previous procedures in the literature, addressed to model fiber reinforced composites, where this equation has been added as an additional independent ingredient of the methodology, in the present approach it arises as a natural result derived from the multifield theory.Every component of the composite is defined with a specific free energy and constitutive relation. The mixture theory is adopted to define the overall free energy of the composite, which is assumed to be homogeneously constituted, in the sense that every infinitesimal volume is occupied by all the components in a proportion given by the corresponding volume fraction.The numerical model is assessed by means of a selected set of experiments that prove the viability of the present approach.

Behavior of High Performance PVA Fiber Reinforced Cement Composites under Uniaxial Compressive Load

Abstract. Based on an extensive experimental program, the paper studies the behavior of High Performance Fiber Reinforced Cement Composite (HPFRCC) under Uniaxial compression. The experimental parameters are: PVA fiber content by volume, fly ash and silica fume content. The compressive strength, peak strain as well as compressive stress-strain curves are obtained. The test results reveal that PVA fibers can greatly improve plastic deformation ability of HPFRCC, especially have significant impact on ductility after the peak stress, though fiber content has small influence on compressive strength. With the increase of fly ash content, peak stress of HPFRCC decreases, but toughness increases. 10% silica fume content has not obvious effect on compressive strength for HPFRCC with large quantities of fly ash , but leads to less ductile behavior.

Strain Energy Frame Impact Machine (SEFIM)

This paper proposes an innovative strain energy frame impact machine (SEFIM) designed to explore direct tensile behavior of high performance fiber reinforced cementitious composites (HPFRCC) at high strain rates. The proposed system utilizes an energy frame to store a large amount of elastic strain energy as well as to suddenly generate high rate tensile impact pulse. The prototype of SEFIM demonstrated that the proposed energy frame could store enough elastic strain energy to fail a large-sized tensile specimen at high strain rates in direct tension. The tensile stress versus strain curve of HPFRCC under high rate impact was obtained by using the prototype with the aid of a high speed camera system and dynamic strain gauges attached on the surfaces of the transmitter bar.

Failure criteria and triaxial behaviour of HPFRC containing high reactivity metakaolin and silica fume

In this paper, the triaxial compressive behaviour of high performance fibre reinforced concrete (HPFRC) containing two types of pozzolans namely high reactivity metakaolin (MK) and silica fume (SF) is studied. Standard triaxial tests with four different confining pressure levels were performed on 75×150mm cylindrical concrete specimens containing 2% steel fibres by volume. Companion uniaxial direct tensile tests are also performed on dog-bone shaped specimens to ascertain the strain-hardening behaviour of these composites. The results show that an increase in confining pressure leads to an increase in the peak additional axial stress in both SF and MK specimens, and the increase is about the same for the two types of composites. However, the peak additional axial stresses of MK specimens occur at higher axial strains thus showing a more ductile behaviour with higher energy absorption capacity. To establish an empirical relation for prediction of axial strength as a function of confining pressure, three constitutive models i.e. Mohr–Coulomb two-parameter, Hsieh–Ting–Chen four-parameter and William–Warnke five-parameter models are used and calibrated with the test results.

Behavior of high performance fiber reinforced cement composites under multi-axial compressive loading

Experiments were conducted to better understand the behavior of strain hardening, high performance fiber reinforced cement composites (HPFRCC) when subjected to uniaxial, biaxial, and triaxial compression. The experimental parameters were: type of fiber, fiber volume fraction, and loading path. Two types of commercially available fibers, namely high-strength hooked steel fiber and ultra high molecular weight polyethylene fiber, with volume fractions ranging from 1.0% to 2.0%, were used in a 55-MPa mortar matrix. The selected loading paths consisted of uniaxial compression and tension, equal biaxial compression, and triaxial compression with two levels of lateral compression. The test results revealed that the inclusion of short fibers can significantly increase both strength and ductility under uniaxial and biaxial loading paths, but that the role of volume fraction is rather small for the range of fiber volume contents considered. The results also showed that the confining effect introduced by the fibers becomes minor in triaxial compression tests, where there is relatively high external confining pressure. The experimental information documented herein can serve as input for the development of multiaxial constitutive models for HPFRCCs.

Rate-dependent tensile behavior of high performance fiber reinforced cementitious composites

High Performance Fiber Reinforced Cementitious Composites (HPFRCC) show strain hardening behavior accompanied with multiple micro-cracks under static tension. The high ductility and load carrying capacity resulting from their strain hardening behavior is expected to increase the resisting capacity of structures subjected to extreme loading situations, e.g., earthquake, impact or blast. However, the promise of HPFRCCs for dynamic loading applications stems from their observed good response under static loading. In fact, very little research has been conducted to investigate if their good static response translates into improved dynamic response and damage tolerance. This experimental study investigates the tensile behavior of HPFRCC using High strength steel fibers (High strength hooked fiber and twisted fiber) under various strain rates ranging from static to seismic rates. The test results indicate that the tensile behavior of HPFRCC using twisted fiber shows rate sensitivity while that using hooked fiber shows no rate sensitivity. The results also show that rate sensitivity in twisted fibers is dependent upon both fiber volume fraction and matrix strength, which influences the interface bond properties.