Use Of Fiber Reinforcement Research Articles

Flexural behaviour of geopolymer concrete beams with hybrid natural–synthetic fibre reinforcement

The requirement of excellent flexural stiffness in construction elements has initiated the use of fibre reinforcement. However, the processing complexity involved in the manufacture of synthetic fibres is environmentally hazardous. The use of natural fibres in geopolymer concrete (GPC) structures was investigated in this work using a hybridisation of natural and synthetic fibre. Natural basalt fibre (BF) was used with synthetic steel fibre (SF) in various proportions in GPC and tests were conducted to evaluate the workability, compressive strength, split tensile strength and flexural strength. It was found that, compared with the plain GPC, the addition of 1.5% BF and 0.5% SF resulted in 45%, 27% and 12% improvements in compressive, split tensile and flexural strengths, respectively. The compatibility between the SF and BF resulted in enhanced post-peak flexural behaviour, with 37% improvements in the modulus of elasticity and stiffness. As BF possesses more tensile strength than SF, the use of 1.5% BF and 0.5% SF provided better flexural and ductility properties than the use of SF alone, which could lead to the development of ductile GPC members under dynamic loading conditions.

Investigation of seismic fragility curves of unbonded FREIs: Adaptive characteristics and modeling sensitivity

AbstractFiber‐reinforced elastomeric isolators (FREIs) are composed of layers of elastomer reinforced with either steel or fibers, and can be placed in a bonded or unbonded configuration between the upper and lower supports. The use of fiber reinforcement in FREIs was intended to reduce the production and installation costs compared to common steel‐reinforced elastomeric isolators (SREIs) and to develop an isolator suitable for widespread application, particularly in developing countries. The unique rollover deformation exhibited by unbonded FREIs (UFREIs), due to their flexible fiber reinforcement, enables them to adapt to multiple performance objectives at different hazard levels. In this study, the impact of different numerical models of UFREIs on the seismic response and failure probability of structures is investigated. The research employs incremental dynamic analysis and the development of fragility curves for different limit states, considering three sets of ground motions (including far‐field and pulse‐like). Moreover, the effect of full rollover was investigated by comparing the fragility curves of UFREIs when supported on modified support geometries, which involved three types of support: unmodified, accelerated, and delayed full rollover. The effectiveness of the adaptive characteristics to behave as a displacement restrain is demonstrated. The results emphasize the importance of employing an accurate model to simulate the behavior of UFREIs as an adaptive device for effectively utilizing their potential capacity, particularly at larger displacements where there is more dissipated energy due to full rollover.

Anisotropy in Additively Manufactured Concrete Specimens under Compressive Loading-Quantification of the Effects of Layer Height and Fiber Reinforcement.

This paper analyzes the effect of print layer heights and loading direction on the compressive response of plain and fiber-reinforced (steel or basalt fiber) 3D printed concrete. Slabs with three different layer heights (6, 13, and 20 mm) are printed, and extracted cubes are subjected to compression (i) along the direction of printing, (ii) along the direction of layer build-up, and (iii) perpendicular to the above two directions. Digital image correlation (DIC) is used as a non-contact means to acquire the strain profiles. While the 3D printed specimens show lower strengths, as compared to cast specimens, when tested in all three directions, this effect can be reduced through the use of fiber reinforcement. Peak stress and peak strain-based anisotropy coefficients, which are linearly related, are used to characterize and quantify the directional dependence of peak stress and strain. Interface-parallel cracking is found to be the major failure mechanism, and anisotropy coefficients increase with an increase in layer height, which is attributable to the increasing significance of interfacial defects. Thus, orienting the weaker interfaces appropriately, through changes in printing direction, or strengthening them through material modifications (such as fiber reinforcement) or process changes (lower layer height, enables attainment of near-isotropy in 3D printed concrete elements.

Coupling effect of fiber reinforcement and MICP stabilization on the tensile behavior of calcareous sand

Coupling method of fiber reinforcement and microbial induced carbonate precipitation (MICP) stabilization was adopted to improve the tensile behaviors of calcareous sand. Three types of fibers, including polypropylene fiber (PF), carbon fiber (CF), and basalt fiber (BF), were used to prepare fiber-reinforced MICP-stabilized calcareous sand samples with various fiber contents and lengths. Direct tensile tests were conducted on a specially designed 8-shaped sample to evaluate the tensile behaviors of the samples. Experimental results revealed that the coupled use of fiber reinforcement and MICP stabilization technique could significantly improve the calcareous sand tensile behaviors. By adding the fibers of PF, CF, and BF, the maximum tensile strength of the sample was increased by 234.0%, 111.8%, and 100.7%, and the corresponding maximum residual strength reached 26.8 kPa, 30.63 kPa, and 50.7 kPa, and their maximum failure displacement was increased by 121.2%, 95.4%, and 100%, respectively compared to the MICP stabilized sample. The coupling mechanism was attributed to the fiber inclusion promoting the calcium carbonate precipitation and forming more effective and extra-effective bonding. The interfacial shear resistance between fibers, calcium carbonate, and calcareous sand and the bridging performance of the crossing fibers facilitated the coupling effect. For all three types of fibers, the higher the fiber content, the greater the tensile strength, residual strength, and failure displacement. The tensile behaviors varied due to the difference in surface properties and mechanical properties of the fiber. PF had the best reinforcement performance on tensile behavior. For the sample with PF (0.1% fiber content), the optimal fiber length was 6 and 9 mm. Moreover, a theoretical relationship between the tensile strength increment and fiber content or fiber length was established. The results of this study are of some significance for the stability and safety of coastal engineering.

Estudio experimental de las propiedades mecánicas del hormigón simple y reforzado con fibras bajo carga monotónica

Concrete is one of the main building materials in Peru and worldwide, the study of its mechanical properties and concrete mix elaboration have been extensively developed over time. In the last years, new ways of elaboration with different materials have been searched, in order to improve its mechanical properties, including the fiber reinforced concrete. The study of its strain-stress mechanical properties of fiber reinforced concrete under monotonic load is the objective of this investigation, based on experimental tests performed in 90 samples, taking into account the influence of many factors, such as: Compression strength design, sample section geometry (square or circular section), slenderness (height/depth ratio), and the comparison of the reinforced concrete with its equivalent plain concrete in terms of mix design. From the experimental results, the use of fiber reinforcement increases the deformation capacity of the concrete under monotonic compression, but its resistance is not improved significantly. On the other hand, square section specimens have a higher deformation capacity for slenderness 1:2 and 1:3 in comparison with circular section specimens.

Effect of Process Parameters on Different Properties of 3D Printed PETG Parts Prepared Using FDM

This study has been undertaken to give a review of polyethylene terephthalate glycol (PETG) material used in fused deposition modelling (FDM). It offers a review of the existing literature on PETG material. The objective of the paper is to providing guidance on different process parameters that can be used to improve strength of the part by performing various testing like tensile, compressive, flexural etc. This research targets to find new paths that can be used for further development of use of fiber reinforcement in PETG material.

Tensile Performance of Headed Anchors in Steel Fiber Reinforced and Conventional Concrete in Uncracked and Cracked State.

Steel fiber reinforced concrete (SFRC) is currently the material of choice for a broad range of structural components. Through the use of SFRC, the entire, or a large portion of, conventional rebar reinforcement can be replaced, in order to improve the load-bearing behavior but also the serviceability and durability characteristics of engineering structures. The use of fiber reinforcement therefore plays a vital role in acute current and future construction industry objectives, these being a simultaneous increase in the service life of structures and the reduction of their environmental impact, in addition to resilience to extreme loads and environmental actions. Next to the extended use of SFRC, modern construction relies heavily on structural connections and assembly technologies, typically by use of bolt-type cast-in and post-installed concrete anchors. This paper addresses the influence of fiber reinforcement on the structural performance of such anchors in SFRC and, particularly, the load bearing behavior of single headed anchors under axial static loads in uncracked and cracked concrete. Along with a presentation of background information on previous studies of SFRC with a focus on anchor concrete breakout failure, the experimental investigations are described, and their results are presented and elaborated on by consideration of various research parameters. A comparison with current design approaches is also provided. The conclusions are deemed useful for structural engineering research and practice.

Strength of Normal and Inclined Sections of Bent Reinforced Concrete Elements with Zone Reinforcement Made of Steel Fiber

On the basis of theoretical and experimental studies, the prerequisites and the method of calculation of bent and compressed-curved reinforced concrete structures with zone reinforcement made of steel fiber, working under static and short-term dynamic loads, are formulated. In the developed method for calculating the strength of normal and inclined sections, a nonlinear deformation model is implemented, which is based on the actual deformation diagrams of materials. The developed calculation method is brought to the program of calculation of reinforced concrete structures with zone reinforcement of steel fiber under short-term dynamic loading, taking into account the inelastic properties of materials. The numerical studies made it possible to determine the influence of various parameters of steel-fiber reinforcement on the strength of reinforced concrete elements. To confirm the main results of the developed calculation method, experimental studies of reinforced concrete beam structures reinforced with conventional reinforcement and a zone steel-fiber layer are planned and carried out. Experimental studies were carried out under static and short-term dynamic loads. As a result of the conducted experiments, data were obtained that characterize the process of destruction, deformation and cracking of steel-reinforced concrete elements under such types of loading. The dependences of changes in the energy intensity of reinforced concrete structures with zone reinforcement made of steel fiber in the compressed and stretched cross-section zones under dynamic loading are obtained. The effectiveness of the use of fiber reinforcement of normal and inclined sections of bent and compressed-curved elements to improve the strength and deformative.

Strength prediction in single beads of large area additive manufactured short‐fiber polymers

AbstractThe use of fiber reinforcement in large area additive manufactured components is of industrial interest due to the ability to enhance the structural properties of final processed parts. This work presents a methodology to predict the tensile, compressive, and flexural yield strength of single beads of a large‐scale, 3D printed, short‐fiber reinforced material. The methodology is built on the strength theory of Van Hattum and Bernardo, which combines the Tsai‐Wu failure criteria with Advani and Tucker's orientation averaging technique, allowing fiber orientation flow model results to serve as direct input into strength predictions. Visual advantages of the methodology such as the ability to plot spatially varying strength constants and failure plots are demonstrated. In addition, an analysis of the methodology's sensitivity to various parameters is conducted.

INFLUENCE OF FIBER REINFORCEMENT ON CONCRETE SHRINKAGE FOR RIGID ROAD AND AIRFIELD PAVEMENT REPAIR

Abstract. The influence of fiber reinforcement with steel anchor fiber on the shrinkage of modified concrete for rigid airfield pavements repair has been determined. A 2-factor experiment was carried out, in which the following composition factors were varied: the amount of hardening accelerator Sika Rapid 3 from 0 to 2.4% of the cement content (0-9.6 kg/m3); the amount of steel anchor fiber with 1 mm diameter and 50 mm length, from 0 to 100 kg/m3. For the concrete batching were used: Portland cement CEM II / AS 42.5 in the amount of 400 kg/m3, granite crushed stone 5-20 mm, quartz sand, plasticizer admixture BASF MasterGlenium SKY 608 in the amount of 1.2% by cement content. The workability of the mixtures was S2 (6-8 cm); W/C ratio depended on the concrete composition. Due to the use of superplasticizers, the W/C of all investigated mixtures was in the range of 0.309-0.343. The shrinkage of the prism specimens was recorded after 3 hours, 6 hours, 1, 2, 3 and 7 days of being in air-dry conditions. The shrinkage process does not end after 7 days of concrete hardening, however, the general nature of the influence of variable factors on its value remains. It has been established that fiber-reinforced concretes, with a fiber amount of 50 kg/m3 and with a fiber amount of 100 kg/m3, have 10-15% less shrinkage compared to unreinforced concretes. Compositions with a fiber amount of 50 kg/m3 and 100 kg/m3 have practically the same shrinkage, which is explained by an increase in W/C ratio with an increase in the amount of fiber reinforcement. The amount of hardening accelerator has a less noticeable effect on the amount of concrete shrinkage. By adding Sika Rapid 3, concrete shrinkage at the age of 7 days is reduced by 2-9%. This effect can be explained by the fact that internal stresses arising in the process of structure formation and moisture loss in concrete are contained in a more durable cement-sand matrix. The concrete shrinkage without fiber and accelerator was also measured up to the age of 98 days. It was found that the limiting shrinkage for such concrete is 2.5×10-4. The analysis of the drawn experimental-statistical model showed that with the amount of metal fiber from 60 to 90 kg/m3 and the amount of the hardening accelerator from 0.9 to 2.4%, the shrinkage of the investigated concretes is minimal (7 = 1.3×10-4). Thus, the use of fiber reinforcement with anchor steel fiber and a hardening accelerator can significantly reduce the concrete shrinkage for the rigid airfield pavements repair is important for this material.

MECHANICAL AND SHRINKAGE BEHAVIOR OF BASALT FIBER REINFORCED ULTRA-HIGH-PERFORMANCE CONCRETE

Ultra-High-Performance Concrete (UHPC) is considered to be a new development of concrete technology with excellent workability, high compressive strength, toughness, and long durability, etc. These characteristics are achieved by the synthetic application of strength enhancements such as the use of mineral additives, optimum particle distribution and especially the use of fiber reinforcement which greatly enhances flexural strength and toughness for the UHPC. In this paper, the influence of basalt fiber content on some properties of UHPC such as workability, compressive strength, flexural strength, elastic modulus and shrinkage were investigated. The results of this paper show that use of basalt fiber with reasonable content will not affect the workability of the concrete mixture while increasing the flexural strength, compressive strength, and elastic modulus of the UHPC. The compressive strength of concrete reaches over 120 MPa, flexural strength is over 10 MPa. UHPC sample using 1.5% fiber content will give the highest compressive and flexural strength values, this value increased about 8.5% compared to the control sample without fibers.

Post-impact flexural capacity of UHPFRC plates

This work aims to demonstrate the effective use of fibre reinforcement in thin plate elements made of UHPFRC under projectile impact loading. The use of fibre reinforcement is very efficient in case of ballistic loading, as fibres are evenly distributed over the entire volume of the material body and possible damage to the plate is thus suppressed in all points of the plate element equally. The aim of this study is therefore to provide data on the residual flexural capacity of plates that have been significantly damaged by the impact of the projectile and to demonstrate the benefits of using fibre reinforcement for localized impact loading.

Experimental and finite element analysis of hybrid fiber reinforced concrete two-way slabs at ultimate limit state

Concrete is a brittle material that is weak in tension and is prone to internal microcracking. With the constant demand for improvement in concrete’s durability and mechanical proprieties, the use of fiber reinforcements has shown promising results. The findings of this paper are based on test results on hybrid fiber reinforced concrete (HFRC) samples of simply supported two-way slabs, produced with a selected volumetric proportion of steel fiber (SF) and polypropylene fibers (PPF). A total of twenty-one specimens were fabricated. Concrete slab specimens were tested under flexural loading and their response in terms of strain, deflection, first crack, and ultimate failure loading was determined. The dosage of SF in concrete ranged from 0.7 to 1.0%, whereas 0.1–0.9% PPF was used by volume of concrete. It was found that a combination of 0.9% SF and 0.1% PPF gave favorable results for loading capacity, ductility, and cracks. A Finite Element Analysis (FEA) of the proposed HFRC two-way slabs was also performed via ABAQUS. The outputs from numerical modeling showed a close agreement with the experimental results. Using the selected FEA model, an extensive parametric study was also done to examine the effect of various parameters including longitudinal reinforcement ratio, compressive strength of concrete, and the concrete cover of specimens. The proposed FEA model presented a close agreement with the experimental outcomes.

Changes in long-term performance of fibre reinforced shotcrete due to corrosion and embrittlement

The post-crack performance of fibre reinforced shotcrete (FRS) differs from that of conventionally reinforced concrete in that the post-crack pull-out characteristics of fibres depend on the properties of the concrete matrix. Changes in the concrete matrix with time can effect substantial changes in the post-crack performance of the fibres in a way that is independent of external exposure conditions. When cracks occur in the FRS matrix, fibres may also be exposed to aggressive agents that can reduce their already small cross-sectional area at the crack and thereby diminish their post-crack performance, particularly at larger levels of deformation. The present investigation has examined how the post-crack energy absorption capacity of fibre reinforced shotcrete is affected by the interaction of aging of the concrete matrix and corrosion at cracks. The findings show that changes in performance characteristics are related to crack width and fibre type. The majority of fibre types show negligible changes in performance at low deformations over time. However, following aging, some fibre types exhibit significantly lower post-crack performance at high deformations than is evident at 28 days. The use of fibre reinforcement in shotcrete therefore needs to address aging effects, the exposure conditions regarding potential corrosion, as well as the in-service conditions of use in order to specify an appropriate maximum crack width limit that will enable the chosen fibre type to perform without risk of corrosion or embrittlement.

Легкий бетон на основе пенополиамидбетонной композиции

One of the most important tasks of construction is the use of energy-efficient sin-gle-layer structures based on foam concrete and an increase in their bearing ca-pacity due to the use of fiber reinforcement, which will significantly improve the performance properties of fiber-reinforced concrete. Strength characteristics of fibro-foam concrete reinforced with polyamide granules with various types of filler and recommendations for its use in building structures were obtained. These experimental studies allow us to recommend the optimal composition of polyam-ide concrete compositions.

An Experimental Investigation on the Properties of High Volume Flyash Glass Fibre Reinforced Self Compacting Concrete

Civil engineering is a professional engineering discipline that deals with the designing and construction. In construction one of the main resource is concrete in the world. The concrete is day-to-day have many changes like strength, durability, shrinkage. This project deals with the self-compaction concrete with use of fibre reinforcement. The self-compacting in concrete is achieved by adding super plasticizers and glass fibres are used as reinforcement. The influence of including fly ash on the properties of self-compacting concrete is investigated. Fly ash is introduced by 50% in the total weight of cement. The water to binder ratio was maintained at 0.38%. Properties included workability, compressive strength, split tensile test, modulus of elasticity and shrinkage. The results indicate the high volume FA can be used in SCC to produce the high strength and low shrinkage. Increasing the admixture content beyond the certain level leads to a reduction in strength and increasing in absorption. Making concrete structure without compaction has been done in the past. Like placement of concrete under water by the use of term without compaction. Inaccessible areas were concrete using such a techniques. The production of such mixes use expensive admixtures ad large amount of cement but such type of concrete is low strength. To eliminate such issues lead to the development of self-compacting concrete (SCC). Usage of fibres makes the mixing of concrete complex. Self-compacting concrete (SCC) is an innovative concrete that does not require vibration for placing and compaction.

Shrinkage Cracking of Concrete Slabs-On-Grade: A Numerical Parametric Study

Industrial pavements are thin slabs on a continuous support subjected to restrained shrinkage and loads. The use of fibers as an alternative reinforcement to steel welded wire mesh and rebars is today an extensive practice for the reinforcement of concrete slabs-on-grade. Despite the widespread use of fiber reinforcement, the corresponding benefits in controlling cracking phenomena due to shrinkage are generally not considered in the design process of Fiber Reinforced Concrete (FRC) slabs-on-grade. The post-cracking performance provided by glass macro-fibers at low crack openings is particularly convenient in structures with a high degree of redundancy. Referring to service conditions, it is well known that concrete shrinkage as well as thermal effects tend to be the principal reasons for the initial crack formation in slabs-on-grade. A numerical study on the risk of cracking due to shrinkage in ground-supported slabs is presented herein. Special attention is devoted to the evaluation of the beneficial effects of glass fibers in controlling cracking phenomena due to shrinkage. The numerical analyses are carried out on jointless pavements of different sizes. Since shrinkage stresses in slabs-on-grade are considerably influenced by external constraints which limit the contractions, different subgrade conditions have been also considered.

Discrete element modeling of free-standing wire-reinforced jammed granular columns

The use of fiber reinforcement in granular media is known to increase the cohesion and therefore the strength of the material. However, a new approach, based on layer-wise deployment of predetermined patterns of the fiber reinforcement has led self-confining and free-standing jammed structures to become viable. We have developed a model to simulate fiber reinforced granular materials, which takes into account irregular particles and wire elasticity and apply it to study the stability of unconfined jammed granular columns.

Experimental studies of fiber concrete creep

The results of two-stage experimental studies of the strength and deformation characteristics of fibrous concrete reinforced with steel fiber. In the experiments we used steel fiber with bent ends, which practically does not form hedgehogs, which allows to achieve an even distribution of the fiber by volume. At the first stage, the cube and prismatic strength, deformability at central compression, a number of special characteristics are determined: water absorption, frost resistance, abrasion; the optimal percentage of fiber reinforcement and the maximum size of the coarse aggregate fraction were selected. Fiber reinforcement led to an increase in the strength of concrete at compression by 1,35 times and an increase in the tensile strength at bending by 3,4 times. At the second stage, the creep of fibrous concrete and plain concrete of similar composition at different stress levels was researched. Creep curves are plotted. It is shown that the use of fiber reinforcement leads to a decrease in creep strain by 21 to 30 percent, depending on the stress level.

Lower bound buckling loads for design of laminate composite cylinders

ABSTRACTOver a period of more than 45 years, an extensive research program has allowed a series of very simple propositions, relating to the safe design of shells experiencing imperfection sensitive buckling, to be recast in the form of a series of lemmas. These are briefly summarized and their practical use is illustrated in relation to the prediction of safe lower bounds to the imperfection sensitive buckling of axially loaded, fiber reinforced polymeric, laminated cylinders. With a fundamental aspect of the approach, sometimes referred to as the reduced stiffness method, being the delineation of the various shell membrane and bending stiffness (or perhaps more appropriately energy) components contributing to the buckling resistance, the method will be shown to also provide a powerful way of making rational design decisions to optimize the use of fiber reinforcement.