Steel Fiber Research Articles

Strength Properties of Lightweight Foamed Concrete with Steel Fiber

The advancement in lightweight cementitious composite strength enhancement has promoting the usage of lightweight material across modern construction industry. Likewise, Lightweight foamed concrete (LFC) was introduced as an alternative material in the construction industry due to its properties including good thermal and sound insulation, lighter in weight and cost-effectiveness. In corresponded to LFC strength issue which often found to be diminished due to its lower density and porous structures. Studies have shown that the incorporation of steel fiber into concrete can recover the diminished strength of lightweight foamed concrete. Hence, this research focusses on the strength properties of LFC incorporate with 30 kg/m3 of steel fiber. Three types of LFC were prepared in this study including a trial mix of LFC (LFC-TM), a control mix of LFC (LFC-CTR), and LFC with 30 kg/m3 steel fiber (LFC-30SF). The LFC-CTR and LFC-30SF were casted based on the obtained optimum water-to-cement ratio from the plotted performance index graph, which was 0.56 for both mixes. The fresh properties of LFC-CTR and LFC-30SF were determined based on the result obtained from fresh density, flow table and inverted slump tests. Besides, the strength properties studied for LFC-CTR and LFC-30SF were compressive strength, splitting tensile strength and flexural strength at 7, 28 and 56 days after curing. From the test results obtained, the compressive, splitting tensile and flexural strength of LFC was found to be improved by adding the steel fiber into the mix. As for the fresh properties of LFC, the stability was found to decreased after the steel fiber was added into the mix, while the flowability and consistency was observed with an improvement subject to fibre addition. In short, incorporating steel fiber can improve the strength properties of LFC, which driving their usability and encouraging wider adoption across modern industries.

Tensile behavior of ultra-high-performance concrete (UHPC) strengthened with fiber reinforced polymer (FRP) grid

In order to enhance the tensile strength and toughness of Ultra-High Performance Concrete (UHPC) at the macro level, this study developed Fiber-Reinforced Polymer (FRP)-reinforced UHPC composite materials. The steel fibers and FRP grids in UHPC play a reinforcing and toughening effect on UHPC at two different levels. Therefore, this paper examined, evaluated 48 FRP grid-UHPC specimens. The study includes independent parameters such as grid type (Carbon-FRP, Basalt-FRP, stainless steel wire mesh), grid size (5 × 5 mm, 10 × 10 mm, 20 × 20 mm), steel fiber content (0 %, 0.5 %, 1.0 %, 1.5 %, 2.0 %), grid layers (1 layer, 2 layers, 3 layers, 4 layers), and the fiber bundle impregnation status. Based on the test results, a simplified tensile stress-strain relationship for FRP grid-UHPC was proposed. The test results show that when the steel fiber content is less than 1 %, the FRP grid does not exert its reinforcing effect. The FRP grid-UHPC composite material exhibits strain-softening behavior. However, when the steel fiber content is greater than 1 %, the FRP grid-UHPC specimens all exhibit strain-hardening phenomena. Compared to other grids type, the enhancement and toughening effects on UHPC are more pronounced when using CFRP grids. Specifically, when using a 20 × 20 mm CFRP grid, the tensile stress can be increased by 30.36 %. Regardless of whether dry grids or impregnated grids are used, increasing the grid layers greatly improves the peak strain and stress of UHPC. Compared to dry grids, impregnation with epoxy resin further improves the stress state between fiber filaments in FRP grids, resulting in a more significant improvement in the tensile performance of FRP grid-UHPC composite materials. Finally, based on experimental data, a tensile stress-strain model for FRP grid-UHPC considering different mesh ratios was proposed and validated against experimental results. These conclusions and findings are of great significance for understanding and optimizing the performance of FRP grid-UHPC composite materials, providing valuable references for the future research and application of FRP grid-UHPC composite materials.

Experimental Investigations on Mineral Admixtures and Steel Fibers in High Strength Concrete

In the process of manufacturing of concrete sand is the most commonly used fine aggregate. The main sources for the natural sand are river beds. These characteristic assets are getting depleted because of over abuse and defilement by chemicals and waste from nearby industries. The waste generated from the demolition of existing structures for various reasons causes great concern and ecological issues. In this project our main objective is to study the influence of partial replacement of F.A with recycled fine aggregate and to compare it with the compressive strength and workability of high strength M60 concrete. We are also trying to replace the various percentages of recycled fine aggregate to study the tendency of the Characteristic strength of concrete.

Cyclic compressive behavior of high-performance hybrid fiber reinforced recycled aggregate concrete: Degradation law and acoustic emission features

To tackle the issues of inadequate mechanical properties of recycled aggregate concrete and its limited application in load-bearing structural components, a high-performance hybrid fiber reinforced recycled aggregate concrete (HP-HFRAC) was developed in this study. Sixteen groups of HP-HFRAC specimens fabricated with varying replacement rates of recycled coarse aggregate and different fiber parameters were subjected to uniaxial compression, as well as acoustic emission (AE) tests, to investigate the cyclic behavior and uncover the underlying mechanisms. The findings demonstrated a strong correlation between the AE signals and the macroscopic phenomenon throughout the whole compression process. The AE amplitude distribution was found to be capable of identifying damage mechanisms, including matrix cracking (40–50 dB), fiber sliding (50–80 dB), and fiber pull-out (more than 80 dB). Additionally, the inclusion of hybrid fibers contributed to mitigating the degradation of stiffness and the accumulation of plastic strain, resulting in the ductile failure of the specimens and significantly enhancing the energy dissipation capacity. Specifically, the peak stress of specimens with 1.5% steel fibers increased by 19% compared to that of specimens without steel fibers, compensating for the strength loss due to the presence of recycled coarse aggregate. Finally, constitutive equations governing the skeleton curves and the unloading and reloading curves of HP-HFRAC subjected to cyclic compression were formulated, which were validated using both the test results and the predicted results of the physics-based data-driven model previously published in our companion paper. The findings of this study might contribute to the development of sustainable high performance recycled aggregate concrete for reliable application in load-bearing components.

Experimental Investigation on Durability Properties of Slurry Infiltrated Fiber Concrete

Slurry infiltrated fibrous concrete (SIFCON) can be considered as a special and advanced type of steel fiber reinforced concrete composite. SIFCON is produced by infiltrating rich flow able cement slurry into the bed of preplaced fibers in the mold. In this paper, an attempt has been made to investigate the durability study of SIFCON. An ordinary Portland cement is used with fiber contents of (5%, 7.5%, 10%, and 12%). This study also presents the effect of incorporating Metakaolin (MK) on the mechanical and durability properties of SIFCON for a constant water/cement ratio of 0.5. The physical properties include the specific gravity, density, fineness modulus, water absorption, consistency. The above properties are studied for materials used like cement, fly ash, coarse aggregate, ceramic, sand and laterite. Mechanical properties of the hardened concrete such as compressive strength, tensile strength, flexural strength, and durability properties like water absorption, sorptivity, acid test, marine environment are tested and the values are validated. Metakaolin is a waste/non-conventional material which can be utilized beneficially in the construction industry. From the literature survey, Metakaolin inclusion increases the compressive, tensile, flexural and bend strength and modulus of elasticity of mortar considerably; however, the workability is slightly compromised.

Retrofitting Shear Critical Beams using Ultra High Performance Fibre Reinforced Concrete (UHPFRC)

Ultra High-Performance Fiber Reinforced Concrete (UHPFRC) is a cementitious composite that exhibits superior mechanical properties, durability, fire resistance, abrasion resistance, and chloride penetration. The enhanced performance of UHPFRC is attributed to the presence of highstrength steel fibers. Therefore, UHPFRC is widely used in structural retrofitting and rehabilitation works to improve the load carrying capacity of deteriorated structural members. This paper investigates the behaviour of UHPFRC retrofitted shear critical reinforced concrete beams. Numerical models were developed to simulate how the load-carrying capacity of UHPFRC retrofitted shear critical beams is influenced by factors such as jacket configuration, jacket thickness, and jacket length along the beam. Numerical models were validated using pre-existing experimental results. A modified Concrete Damage Plasticity (CDP) model was employed to simulate the material behaviour of UHPFRC. The validated numerical model was employed to perform parametric studies to examine the behaviour of UHPFRC retrofitted beams. It was observed that the modified CDP model effectively predicted the UHPFRC behaviour. Further, the results indicated that the application of UHPFRC retrofitting converted the brittle shear failure of shear-critical reinforced concrete beams into flexure failure. Moreover, the load carrying capacity of retrofitted beams increased with the retrofitted UHPFRC jacket thickness.

A damage constitutive model for consistent description of static and fatigue behaviors of ultra-high performance concrete containing coarse aggregate

A suitable constitutive model for describing the mechanical behaviors of ultra-high performance concrete (UHPC) under various loading histories plays a vital role in analyzing its structural performance. In this work, a consistent elastoplastic damage model is developed for UHPC containing coarse aggregate (UHPC-CA) subjected to static and fatigue loads, in which the driving and alleviating effects induced by the inclusions of coarse aggregate and steel fiber are considered. For damage evolution, based on the acting mechanism of the non-uniformity of stress wave propagation determined by the loading rate on the mechanical responses of UHPC-CA, the loading rate is skillfully integrated into the damage evolution rule to achieve the consistent description of mechanical behaviors of UHPC-CA under static and fatigue loading conditions. Regarding plasticity growth, an empirical plastic deformation model is adopted to improve the computational efficiency of structural nonlinear analysis. To verify the applicability of the proposed model, a user-defined UMAT subroutine is further developed for the subsequent numerical implementation. The comprehensive comparisons between the numerical predictions and independent experimental results at both the material level and structural level solidly demonstrate the capacity of the consistent model to capture the main features concerning the mechanical performance of UHPC-CA subjected to different loading paths.

The impact of different steel fibers percentages on the mechanical properties of Ultra-High-Strength Concrete toward a sustainable composition

The impact of different steel fibers percentages on the mechanical properties of Ultra-High-Strength Concrete toward a sustainable composition

Experimental Investigation on Shear Behavior of Non-Stirrup UHPC Beams under Larger Shear Span–Depth Ratios

Due to the extraordinary mechanical properties of ultra-high-performance concrete (UHPC), the shear stirrups in UHPC beams could potentially be eliminated. This study aimed to determine the effect of beam height and steel fiber volume content on the shear behavior of non-stirrup UHPC beams under a larger shear span–depth ratio (up to 2.8). Eight beams were designed and fabricated including six non-stirrup UHPC beams and two comparing stirrup-reinforced normal concrete (NC) beams. The experimental results demonstrated that the steel fiber volume content could be a crucial factor affecting the ductility, cracking strength, and shear capacity of non-stirrup UHPC beams and altering their failure modes. Additionally, the height of the beam had a considerable effect on its shear resistance. French standard formulae were more accurate for the UHPC beams with larger shear span–depth ratios, PCI-2021 formulae greatly overestimated the shear capacity of UHPC beams with larger shear span–depth ratios, and Xu’s formulae were more accurate for the steel fiber-reinforced UHPC beams with larger shear span–depth ratios. In summary, French standard formulae were the most suitable formulae for predicting the shear capacity of UHPC beams in this paper.

Experimental Study of Recycled Aggregate, Fly Ash and Steel Fiber on Properties of Concrete

The use of recycled aggregates in concrete opens a whole new range of possibilities in the reuse of materials in the building industry. The utilization of recycled aggregates is a good solution to the problem of an excess of waste material, provided that the desired final product quality is reached.The use of recycled aggregate in concrete can be useful for environmental protection and economical terms recycled aggregates are the materials for the future.The work focuses on the possibilities of the recycled aggregate concrete as structural material with replacement level of 25%,50% and 75% byweight of concrete. Fly ash is also used as a partial replacement of Portland cement with10, 20 & 30 % by weight of cement in order to improve the properties of RAC. The use of fly ash replacement in Recycled Aggregate concrete (RAC) could improve compressive strength to be higher than that of concrete without fly ash at the same W/B ratio.The fly ash is an organic, non combustible residue of coal after burning in power plant. The steel fiber are available imperforated, corrugated or with wide end for better bending.The volume fraction of the hook end steel fiber used in this study varied from 0.25%,0.5%a and 0.75 %. Key words- Fly Ash, Recycled Aggregate, Recycled Concrete Aggregate, Steel Fiber, Water Cement Ratio.

Machine and deep learning-based prediction of flexural moment capacity of ultra-high performance concrete beams with/out steel fiber

Machine and deep learning-based prediction of flexural moment capacity of ultra-high performance concrete beams with/out steel fiber

Shear behavior of ultra-high performance concrete corbels：Experimental study and modified strut-and-tie model

In this study, a static loading test was performed to examine the shear behavior of twelve ultra-high performance concrete ( UHPC) corbels. The impact of key parameters, such as shear-span ratio, steel fiber volume ratio, and stirrup reinforcement ratio on corbels' mechanical behavior, were explored. The test findings reveal that the cracking load of UHPC corbels is significantly higher than that of the corbels without steel fiber, and the failure mode changes from shear failure to flexural failure. Reducing the shear-span ratio and increasing the stirrup reinforcement ratio substantially improved the shear capacity of the corbels. Furthermore, a modified strut-and-tie model was developed for predicting the shear capacity of UHPC corbels. A shear test database for UHPC corbels was compiled to validate the accuracy of the proposed method. The model showed strong agreement with the test results and demonstrated satisfactory adaptability. Finally, four other models from national standards and academic proposals were evaluated under the same conditions. The proposed model showed superior correlation with the experimental data, suggesting its potential to improve the design and application of UHPC corbels in practical engineering contexts.

Development and Calibration of a Phenomenological Material Model for Steel-Fiber-Reinforced High-Performance Concrete Based on Unit Cell Calculations.

A phenomenological material model has been developed to facilitate the efficient numerical analysis of fiber-reinforced high-performance concrete (HPC). The formulation integrates an elasto-plastic phase-field model for simulating fractures within the HPC matrix, along with a superimposed one-dimensional elasto-plasticity model that represents the behavior of the embedded fibers. The Drucker-Prager plasticity and one-dimensional von-Mises plasticity formulations are incorporated to describe the nonlinear material behavior of both the HPC matrix and the fibers, respectively. Specific steps are undertaken during the development and calibration of the phenomenological material model. In the initial step, an experimental and numerical analysis of the pullout test of steel fibers embedded in an HPC matrix is conducted. This process is used to calibrate the micro-mechanical model based on the elasto-plastic phase-field formulation for fracture. In the subsequent step, virtual experiments based on an ellipsoidal unit cell, also with the resolution of fibers (used as a representative volume element, RVE), are simulated to analyze the impact of fiber-matrix interactions and their physical properties on the effective material behavior of fiber-reinforced HPC. In the final step, macroscopic boundary value problems (BVPs) based on a cuboid are simulated on a single scale using the developed phenomenological material model. The resulting macroscopic stress-strain characteristics obtained from both types of simulations, namely simulations of virtual experiments and macroscopic BVPs, are compared. This comparison is utilized for the calibration of material parameters to obtain a regularized solution and to assess the effectiveness of the presented phenomenological material model.

Effect of fiber type on performance of fiber reinforced concrete applied for hydraulic construction

This study aims at evaluating effect of fiber types on comprehensive property of a practical fiber reinforced concrete (FRC) applied for hydraulic construction. Three fiber types including polypropylene, glass, and steel fiber were used to replace concrete volume at 0.3 vol.%. Experimental results illustrated that when compared with the reference concrete, the fiber reinforced concretes with steel or glass fiber had comparable or slight changes on the fresh properties. But, addition of polypropylene fiber induced the fresh FRC with decreased slump flow and significantly increased air entrained volume. Although using various types of fibers led to unbeneficial effect on the compressive strengths of the FRCs, presence of fiber induced the FRCs with significant enhancements on the flexural strength, drying shrinkage, and water absorption and slightly increased UPV at 28 days. In this study, steel fiber was considered as the best choice for improving the mechanical properties of the hardened concrete while, as the volume stability and durability performance of the concrete were primarily considered, polypropylene seemed to be a preferable selection. According to standardized requirements, all concrete proportions were in classification of M40(28)-M45(28), being assigned to concretes suitably applied for widespread on-site hydraulic constructions.

Investigating the role of steel and polypropylene fibers for enhancing mechanical properties and microstructural performance in mitigating conversion effects in calcium aluminate cement

Fiber reinforcement is widely employed in numerous industries due to its exceptional mechanical properties; however, its specific role in enhancing the strength of calcium aluminate cement (CAC) composites remains inadequately understood. This study investigates the influence of fiber addition on the mechanical characteristics of CAC composites during curing. Two types of fibers, steel and polypropylene, were incorporated into CAC composites, and their mechanical properties, chemical composition, and microstructural performance were evaluated using various methods. Assessments including flowability, bulk density, volume of permeable voids, water absorption, and mechanical strength tests were conducted, alongside X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), and Field Emission Scanning Electron Microscopy (FESEM) analysis. Results reveal a significant enhancement in mechanical strengths with the inclusion of fibers in CAC composites. The addition of 1% fibers to the composites resulted in significant improvements. Steel fibers (SF) led to notable enhancements of approximately 19.7%, 68%, and 26.4% in compressive, direct tensile, and flexural strengths, respectively, while polypropylene fibers (PF) resulted in enhancements of 1.9%, 20%, and 16.7%, respectively. Microstructural analysis revealed that SF and PF contribute to pore refinement, enhancing strength and durability. Findings suggest that SF addition effectively mitigates strength loss induced by the conversion effects of stable phase C3AH6 in CAC, thereby fostering the development of an environmentally friendly, quick-setting, high-performance concrete system. This research offers valuable insights for the design and potential enhancement of CAC-based composites to improve performance and durability under severe conditions.

Mechanical properties of recycled aggregate concrete reinforced with steel fibers under triaxial loading

The use of steel fiber reinforced recycled concrete (SFRAC) can help achieve resourceful reuse of construction waste and environmental sustainability. However, SFRAC structural members may experience complex stress states. Therefore, triaxial compression tests were conducted on 168 cylindrical SFRAC specimens to investigate their mechanical properties. The failure modes, stress-strain behavior, strength, and deformation of SFRAC under triaxial compression were observed. The effects of lateral confining pressure, steel fiber (SF) content, and recycled coarse aggregate (RA) replacement rate on these properties were analyzed. The internal micro-morphology of SFRAC was analyzed using SEM to better understand its failure mechanism under compression. The result shows that an increase in lateral confining pressure alters the failure mode of SFRAC specimens, resulting in a significant increase in peak strength and ductility. The enhancement of the elastic modulus by steel fibers decreases as the lateral confining pressure increases, suggesting a coupling effect between the two parameters. The inclusion of steel fibers in SFRAC did not have a significant impact on its failure mode or compressive strength. And yet, it did increase the ductility and toughness of the material, with an optimal steel fiber content of 1 % (by volume). On the other hand, the addition of recycled coarse aggregate resulted in a significant reduction in the concrete's compressive strength, by almost 17 %. Finally, several common material failure criteria for concrete were used to evaluate the impact of RA substitution rate and SF content on the strength of SFRAC. The Willam-Warnke failure criterion showed a higher strength. These findings provide a theoretical basis for future engineering applications of SFRAC.

Achieving thermoelectric properties of ultra-high-performance concrete using carbon nanotubes and fibers

The study investigated the impact of carbon nanotubes (CNTs), carbon fibers (CFs), steel fibers, and varying water-to-binder (W/B) ratios on the thermoelectric and mechanical properties of ultra-high-performance concrete (UHPC). Flowability tests revealed reduced flow with decreased water content and the addition of CNTs or CFs, particularly pronounced at a lower W/B ratio. Thermal gravimetric analysis and Fourier-transform infrared spectroscopy demonstrated differences in peak intensities and shifts in peaks related to the hydration products of the UHPC by the incorporation of the CNTs and CFs. The compressive strength and tensile performance increased with reduced W/B ratios and the inclusion of steel fibers, whereas the CNTs and CFs affected the strength differently based on their dispersion and interaction with other components that influenced porosity. The presence of steel fibers reduces the percolation threshold for CNTs and CFs, indicating a synergistic effect that enhances electron transport connectivity. The thermal conductivity increased with the addition of CNTs, CFs, and steel fibers, enhancing heat transfer within the UHPC. The thermoelectric figure of merit (ZT) values highlighted the combined impact of CNTs, CFs, steel fibers, and W/B ratios on the thermoelectric efficiency of the UHPC, showing significant improvements with the inclusion of steel fibers and the interplay between the CNTs and W/B ratios. Ultimately, upon introducing 1.5 % steel fibers and 0.3 % CNTs, a substantial enhancement in the thermoelectric ZT was observed, surpassing the standard UHPC values by 12 orders of magnitude.

The impact of different length hooked‐end fibers on the structural performance of RC folded plates

AbstractIn this article, the effect of hooked‐end fibers with different lengths on the structural performance of RC‐FPs fabricated from hybrid fiber‐reinforced self‐compacting concrete (HFR‐SCC) was investigated. For this purpose, a total of 15 full‐scale test samples having different plate thicknesses (60, 70, and 80 mm) were produced and tested under bending after a 90‐day curing period. Subsequently, load‐carrying capacity (Pp), flexural toughness (Fth), and deflection ductility index (μu) of all RC‐FPs were found using load‐deflection curves obtained from bending tests, while crack patterns were drawn from the samples tested. Besides, high‐precision contour plots are proposed to estimate the structural performance values of RC‐FPs depending on plate thickness and fiber reinforcing index. As a result, the best structural performance in RC‐FPs was obtained from the use of a longer hooked‐end steel fiber together with micro steel fiber as a hybrid, followed by the lower length hooked‐end steel fibers as singles. Specifically, irrespective of the plate thickness, the hybrid use of longer hooked steel fibers in combination with micro fibers increased the Pp, Fth, and μu values of RC‐FPs on average 1.67, 1.76, and 1.57 times, respectively, compared to the control specimens. As for when using the lower length hooked‐end fiber as single, the values of Pp, Fth, and μu increased on average 1.57, 1.69, and 1.30 times. Lastly, whereas plate thickness has little effect on improving the structural performance of thin‐walled carrier elements such as RC‐FPs, adding fibers in different lengths, aspect ratios, and combinations is much more effective. The collective test results demonstrate that using RC‐FPs made of HFR‐SCC in the roof carrier system of large span structures could improve structural performance, aesthetics, erection time, and earthquake behavior thanks to reduced dead load.

Performance analysis and application fields of reactive powder concrete

Reactive Powder Concrete (RPC) is a novel concrete material prepared from highly active composite admixtures, cement, fine sand, and micro steel fibers through appropriate curing and processing techniques. RPC not only exhibits ultra-high strength and durability but also demonstrates outstanding toughness, good volume stability, and excellent environmental performance. Its use can reduce the demand for natural resources, extend the service life of structures, and reduce waste generation, aligning with the direction of sustainable development and green building. This makes it an ideal choice for constructing large-span lightweight structures and structures operating in harsh environmental conditions, attracting extensive research attention in the international engineering materials field. In summary, RPC, as a new type of concrete material, has broad application prospects in the construction field. With continuous research and technological development, RPC will undoubtedly bring more innovations and new solutions to the construction industry, promoting its continuous progress and development.

Assessing sampling interval-dependent roughness in fractured steel fiber reinforced concrete using a double-exponential decay model

This study introduces a double-exponential decay (DED) model to investigate the sampling interval (δ)-dependent behavior of crack morphology roughness in steel fiber reinforced concrete (SFRC). The root mean square (Z2-3D) of the directional derivatives in 3D digital morphology is employed to quantify the roughness and its anisotropic behavior. Surface morphologies of 24 fractured specimens are captured by using a laser scanner and the obtained results are re-meshed based on the Point-Kriging algorithm. The roughness is represented by the ratio of surface area to projected area (RS) and Z2-3D values along different directions at various δs (4–3000 μm). The outcomes suggest that the values of RS and Z2-3D both decline, but the anisotropy of surface roughness is enhanced at an increased δ. The DED model is able to properly reflect the decay behavior in which the morphology roughness is classified into three corrugated components based on their distinct attenuation laws. A satisfactory agreement with the literature data is observed, validating the presented methodology. The reported findings in this work are useful for enhancing the understanding of the formation of crack morphology roughness and its relationship to the damage process of SFRC.