Steel Fiber Research Articles

The Effect of Fiber Type on The Shear Capacity of Beams Manufactured By Using Geopolymer Concrete Based on Fly Ash

Ordinary Portland cement is currently generally used cementitious material in the construction industry. However, it has significant drawbacks as it not only depletes natural resources but also releases a substantial amount of carbon dioxide during its production process. On the other hand, alkali-activated cement is an alternative option that is derived from raw materials like slag, fly ash, and metakaolin, which contain silicon dioxide (SiO2) and aluminum oxide (Al2O3). This study investigates the shear capacity of fibre-reinforced geopolymer concrete (GPC) beams under shear loads. In the study, the shear behavior of beams produced from fly ash-based geopolymer of three different fiber types was determined by applying a three-point shear test. Four beams of 100x100x400 mm dimensions were produced: reference, steel fiber, basalt fiber and glass fiber. The results showed that using steel fiber has the greatest impact on shear capacity. In addition, the shear capacity of fibrous samples is greater than the shear capacity of the reference sample. The steel fiber sample has 203% more shear capacity than the reference sample.

Punching shear behavior of ultra-high-performance fiber-reinforced concrete and normal strength concrete composite flat slabs

This paper presents the results of tests on flat slabs with partial application of ultra-high-performance fiber-reinforced concrete (UHPFRC) mixtures to improve the punching shear capacity of slab-column connections. One normal strength concrete (NSC) slab and two UHPFRC slabs were tested as a reference for tests on 12 UHPFRC-NSC composite slabs with full depth UHPFRC in the center area of the NSC slab. The main test parameters were the steel fiber volume (0.8 % and 1.6 % volume fractions) and the dimensions of UHPFRC mixtures. The load-column displacement curves, crack patterns, slab rotations at failure, and failure loads are presented and discussed. The failure loads are compared with estimates obtained following the yield line analysis, design codes, and other theoretical models. Test results showed that the use of UHPFRC mixtures led to an increase in initial stiffness, punching shear strength, and deformation capacity, along with a change in the slab failure mode. The shear capacity of the slab improved proportionally to the increase in the dimension of the UHPFRC. These tests confirmed the effectiveness of the UHPFRC mixtures as an alternative to enhance the punching shear capacity for slab-column connections.

Interlayer bonding performance of 3D printed engineered cementitious composites (ECC): Rheological regulation and fiber hybridization

The weak interlayer adhesion caused by the layer-by-layer 3D printing (3DP) process and the incorporation of organic fiber in Engineered Cementitious Composites (ECC), detrimentally impacts the integrity of 3DP-ECC structures, particularly for large-scale structures requiring extended open time. To optimize the printing quality and extent the operation time, cellulose filaments (CF) were employed as nano-reinforcement, viscosity modifier and water retainer, and were hybridized with polyethylene fiber (PE) and steel fiber (ST). The highest bonding strength was raised up to 3.51 MPa. The time-dependent escalation of rheological parameters was mitigated, reducing interlayer porosity to 0.56 % and limiting the reduction in bonding strength to 12.01 % within 60 min open time. The compressive anisotropy was almost eliminated, verifying the potential of CF in modifying interlayer adhesion. A linear correlation between rheological behavior and interlayer bonding performance was established, and a 0.508 Pa s/min plastic viscosity growth rate was suggested to avoid cold joint and ensure printing quality.

Effect of water to cement ratio on mechanical properties of FRC subjected to elevated temperatures: Experimental and soft computing approaches

The deterioration of concrete is greatly dependent on the cracks and microcracks development owing to loading or environmental influences. An effective step to avoid the spread of cracks and microcracks is employing of different fibers in concrete and the manufacture of fiber reinforced concrete. On the other hand, fire is one of the cases that always threatens engineering structures. Elevated temperatures cause obvious chemical and physical changes that lead to concrete deterioration. In this study, the effect of adding various fiber with different volume contents in concrete mixture with various cement content was evaluated experimentally. Results indicate that spalling was more dominant in mixture containing steel fiber and with higher amount of cement, while there is not any spalling in mixture containing polypropylene (PP) fibers. Moreover, the reduction in tensile strength of fiber-free concrete specimens is less pronounced in mixtures with higher cement content. In addition, the positive performance of PP fibers compared to steel fibers was proved at higher temperatures and cement contents. Furthermore, by conducting a comprehensive and accurate survey, this research pinpoints gaps in the current literature. Moreover, the gathered dataset serves as input for training a machine learning approach known as Group Method of Data Handling (GMDH). The GMDH network demonstrates a satisfactory accuracy in predicting experimental results, with a MSE of 0.0044.

Exploring steel fiber integration in dry lean concrete: predictive analysis of compressive strength and performance via machine learning

Exploring steel fiber integration in dry lean concrete: predictive analysis of compressive strength and performance via machine learning

Experimental study on mechanical properties and toughness of recycled steel fiber rubber concrete

Adding rubber particles to concrete can improve its brittleness, but it also significantly reduces its compressive strength. In order to maintain the compressive strength of concrete unchanged and enhance its tensile strength and toughness, waste steel fibers are added to rubber concrete (RC). This not only achieves the reuse of solid waste materials, but also achieves the goal of high-performance concrete. By adding different amounts of scrap steel fibers to three different strength grades of rubber concrete, scrap steel fiber rubber concrete (SSFRC) is formed. Compression strength, tensile strength, and flexural strength tests were conducted on SSFRC with different mix ratios. The toughness of SSFRC was evaluated by introducing the tensile compression ratio, flexural compression ratio, and toughness index. The microscopic characteristics of SSFRC were observed using scanning electron microscopy (SEM), and the strengthening and toughening mechanism of waste steel fibers on RC was analyzed. The results show that: adding rubber decreases the mechanical properties of concrete with various matrix strengths; adding steel fiber admixture causes a trend in the mechanical strengths of SSFRC with various matrix strengths to increase and then decrease; getting the greatest compressive strength at 1 % and the peak tensile and flexural strengths at 1.5 %; Steel fibers and rubber particles can cooperate at a specific admixture amount to increase the toughness of RC. The local hydration of the scrap steel fibers may have taken place, according to the microscopic morphology of the Transition zone at the interface between the matrix and the scrap steel fiber. In conclusion, the best mechanical strength enhancement effect and the best toughness of SSFRC are achieved at 10 % of rubber and 1.5 % of scrap steel fiber.

EXPERIMENTAL APPROACH FOR DEVELOPMENT OF SUSTAINABLE HYBRID GRADED FIBER REINFORCED CONCRETE BY CONSUMING LATHE WASTE STEEL FIBERS WITH GLASS FIBERS FOR ENHANCED MECHANICAL PROPERTIES

Local workshops generate large quantities of industrial lathe waste steel fibers, which the steel manufacturing industries find difficult to recycle because of their sharp edges. The utilization of lathe waste steel fibers as fiber reinforcement is sustainable in concrete because these fibers have the same properties as steel fibers. Furthermore, using combinations of ductile and elastic fibers improves strain capacity and resistance to pre- and post-cracking. This research employs hybrid fiber reinforcement technology, utilizing industrial lathe waste steel fibers and glass fibers in varying proportions, to bridge the micro and macro cracks in concrete specimens. This research was done to examine the physical (workability) and mechanical properties (compressive and flexural strength) of hybrid fiber-reinforced concrete. In this research different mixtures of hybrid fiber-reinforced concrete were cast and designated as M0, M1, M2, M3, M4, M5, and M6. The mixtures included lathe waste steel fibers at 0%, 0.50%, 1%, 1.5%, 2%, 2.5%, and 3%, and glass fibers at 0%, 0.15%, 0.25%, 0.45%, 0.60%, 0.75%, and 0.90%, respectively. The ASTM-standardised protocols were followed for all laboratory testing. The physical property results showed a decrease in the workability of concrete mixes as the percentage of lathe waste steel and glass fiber increased. This suggests that a higher percentage of lathe waste steel and glass fibers leads to a lower slump value. Consequently, the mechanical property results showed a gradual enhancement in the compressive and flexural strengths of hybrid fiber-reinforced concrete up to 2.5% lathe waste steel fibers and 0.75% (M5). Further incorporation causes a reduction in strength. The physical examination of fractured samples of hybrid fiber-reinforced concrete confirms that the lathe waste steel fibers yield a maximum strain before breaking down in the concrete matrix. Furthermore, lathe waste steel fibers broke rather than being pulled out, indicating a good bond with the concrete. It is recommended that up to 2.5% lathe waste steel fibers and 0.75% of glass fibers by the total weight of the concrete can be used as hybrid fiber reinforcement for optimum strength achievement.

Mechanical and tribological properties of FeS/Cu–Bi self-lubricating materials reinforced with copper-plated steel fibers

PurposeThis study aims to investigate the effect of steel fibers on the mechanical and tribological properties of FeS/Cu–Bi self-lubricating materials.Design/methodology/approachThe microstructure of the material was characterized by scanning electron microscopy. Tests on the crushing strength, impact toughness and tribological properties of materials were conducted using a universal electronic testing machine, a 300 J pendulum impact testing machine and an M200 ring-block sliding tribometer, respectively.FindingsThe mechanical properties of the material initially increased and then stabilized with increased copper-plated steel-fiber length. When the length of the copper-plated steel fiber was 7 mm, the mechanical properties of the material reached stability. Compared with the material without a copper-plated steel fiber, its crushing strength and impact toughness increased by 32.6% and 53%, respectively. A copper-plated steel fiber with a length of 7 mm lay flat in a copper matrix can strengthen the friction interface and enrich the lubricant. Accordingly, the antifriction and wear resistance of the materials increased by 17.6% and 55%, respectively.Originality/valueThe effects of copper-plated steel fibers on the properties of FeS/Cu–Bi self-lubricating materials were clarified. This work can serve as a reference for improving material performance and its engineering applications.

Performance evaluation of high-performance concrete mixes incorporating recycled steel scale waste as fine aggregates

In this study, steel-scale waste (SSW), a byproduct generated during the manufacturing of steel, was investigated as a potential alternative to natural fine aggregates (sand) for preparing high-performance concrete (HPC). Three grades of sand and SSW with different particle sizes were mixed in varying combinations. Three different compaction techniques (loose, tamped, vibration) were employed. The optimum packing density for both SSW and natural aggregates was achieved using the vibration compaction method. Since the combination of 50 % sand and 50 % SSW exhibited the best packing density for both materials, this bi-grade aggregate mixture was selected for the mix preparation. The mechanical tests (compressive strength, flexural strength) and durability assessment (bulk water sorptivity, rate of water absorption, chloride ion penetration) were performed to achieve the desired objectives. The specimens were exposed to two different curing regimes i.e., normal curing and heat curing at elevated temperature. A significant increase in compressive and flexural strength was observed with the increased content of SSW. A compressive strength as high as 140 MPa was obtained for the HPC mix containing SSW aggregates and steel fibers. The replacement ratio of SSW was optimized to achieve better strength and durability. Experimental results showed that heat curing was more effective than conventional curing methods in improving the performance of the concrete.

Crack characteristic and fractal analysis of SFRC shear wall with CFST columns under repeated low cycle load

In this study, we conducted a comprehensive analysis of the crack characteristics and fractal behavior in steel fiber reinforced concrete shear walls (SFRCSW) reinforced with concrete-filled steel tube columns (CFSTCs) under repeated low-cycle loading conditions after failure. Notably, the incorporation of steel fibers and CFSTCs did not alter the fundamental shear failure mode but effectively constrained crack widths to 2.0 mm and 1.6 mm, respectively, from an initial width of 2.4 mm. The use of steel fibers or CFSTCs led to significant improvements in the surface crack fractal dimension (SCFD) of shear walls, with increase ratios of 9.7 % and 7.88 %, respectively. Conversely, an increase in SCFD was associated with improvements in yield load, peak load, failure load, and cumulative hysteretic energy consumption in SFRCSWs. SCFD is suitable for comparative evaluation of the bearing capacity and energy dissipation capacity of different shear walls, but it is not suitable for comparative evaluation of displacement and ductility. For shear walls, it seems more reasonable to evaluate the damage degree in loading process by displacement - fractal dimension relation, rather than load - fractal dimension relation, with the critical values of fractal dimension are about 1.12 and 1.17.

Performance of RC Beams reinforced with Steel Fibers under Pure Torsion

Performance of RC Beams reinforced with Steel Fibers under Pure Torsion

Stability of slender GFRP tube-confined UHPC-filled steel-encased column under axial compression: Experiment and mesoscale modeling

The stability of GFRP tube-confined UHPC-filled steel-encased columns (FUSCs) is critical for optimal utilization of its superior cross-sectional load-bearing capacity that guarantees overall structural safety. This study conducted an experimental investigation on 14 slender FUSC specimens under uniaxial compression for different aspect ratios and aggregate contents. The pressure-sensing films were applied to measure the contact pressure between the GFRP tube and UHPC, and a mesoscale finite element model was developed to uncover the role of randomly distributed fibers and aggregates in the UHPC during the failure process. Accordingly, the stability performance of slender FUSC was analyzed, and specific discussions were held on the mutual interaction mechanism between GFRP and UHPC during the loading process. The results showed that the stability of FUSCs decreased faster with an aspect ratio of l0/D > 8 (λ>30.77), resulting in the decrease of load-carrying capacity for up to 25 %. By including coarse aggregate, the distribution of steel fibers was densified, and Young's Modulus of UHPC was increased, considerably improving the stability of FUSCs. Moreover, the GFRP tube with a fixed winding angle of 50° remarkably enhanced the stability of the specimen due to the sharing of bending moment instead of providing confinement. This research outcome offers a basis for the stability control of slender FUSCs.

Experimental and analytical study on the bending performance of UHPC‐NC narrow steel box composite beams under negative moments

AbstractA novel UHPC‐NC composite structure was proposed to enhance the load‐bearing capacity of concrete beam bridges under negative bending moments. Parameters including steel fiber content in UHPC, reinforcement ratio, and steel box filling height were varied across 8 UHPC‐NC narrow steel box composite beam specimens. The study involved testing, and measurement of failure modes, crack distribution, deformation characteristics, and crack widths. Additionally, a method for calculating maximum crack widths was developed based on crack distribution patterns. Furthermore, a computational model for predicting the ultimate bearing capacity of UHPC‐NC narrow steel box composite beams was constructed. The computed results aligned closely with experimental findings, validating the accuracy of the proposed computational model.

Advanced monitoring of damage behavior and 3D visualization of fiber distribution in assessing crack resistance mechanisms in steel fiber-reinforced concrete

This study presents a novel approach to understanding the reinforcing mechanisms of steel fiber-reinforced concrete, particularly its crack resistance and toughening effects. By integrating dynamic surface strain monitoring with advanced three-dimensional visualization techniques, new insights are provided into how steel fibers enhance concrete's structural performance. X-ray computed tomography (CT) technology enabled detailed 3D visualization and analysis of steel fibers embedded within the concrete matrix, facilitating an in-depth examination of their distribution patterns, orientation, and positioning. Additionally, the Digital Image Correlation (DIC) three-dimensional full-field strain measurement system was utilized to dynamically monitor the loading process during three-point bending tests on semicircular concrete specimens. The findings indicate that the uniform distribution of steel fibers significantly reduces stress concentration and effectively delays crack initiation and propagation. Steel fibers bridge cracks, mitigate local stress concentrations, and substitute for the tensile components of concrete after macro-crack formation, thereby inhibiting further crack propagation. Quantitative analysis of fiber distribution through 3D image reconstruction and coordinate extraction confirmed a strong correlation between fiber orientation and crack resistance. This study contributes to the field by offering a comprehensive analysis of key parameters such as fracture process strain monitoring, 3D visualization, and quantification of fiber distribution, advancing the understanding of crack propagation mechanisms and failure processes in fiber-reinforced concrete.

Mechanical properties of reactive powder concrete under compression at ultra-low temperatures

In this paper, the mechanical properties of reactive powder concrete (RPC) at ultra-low temperatures were studied. RPC prisms (300 mm × 100 mm × 100 mm) were tested at ultra-low temperatures (20 °C, 0 °C, −20 °C, −40 °C, −80 °C, −120 °C, −165 °C) and resulting prism compressive strength, compressive stress-strain curve, and toughness were determined. The increase in prismatic compressive strength of RPC at ultra-low temperatures is greater than that of ordinary concrete, with an overall strength of about 2.12 times that of ordinary concrete. Pore water freezing behavior was also studied to assess the effects on the mechanical properties of RPC in ultra-low temperatures. The water-ice phase transition further improved the RPC strength. With the reduction in temperature, The change in elastic modulus of RPC change is small, the peak strain of specimens at different temperatures increases with the decrease in temperature. The peak strain of RPC showed an overall linear increase with decreasing temperatures, and the water-ice phase transition at negative temperature increases the peak strain of RPC, adding steel fibers improves the RPC ductility, limiting the fracture. With the temperature reduction, RPC toughness first increases and then decreases. The toughness is lowest at room temperature, and highest at −120 °C, which is 2.26 times higher than at room temperature. RPC has better toughness than normal concrete at different temperatures, the reduction of temperature relatively improves the toughness of RPC, and the addition of steel fibers plays a vital role in improving the toughness. This study can serve as technical support for using RPC to design liquefied natural gas full-capacity tanks.

Design, modelling and optimisation of ultra high-performance fibre reinforced concrete incorporating waste materials

The adoption of ultra-high-performance fibre-reinforced concrete (UHPFRC) in modern-day construction has gradually increased because of its high compressive and flexural strength at the early production ages. The UHPFRC's high initial cost discourages its production and widespread use. This cost can be reduced by incorporating waste materials in UHPFRC production. This study aims to design, model, and optimise a three-day heat-cured UHPFRC incorporating waste materials. To produce a sustainable UHPFRC mixture, this study combines rice husk ash (RHA) and recycled tire steel fibre (RTSF) as the primary waste components, with Portland limestone cement, river sand, superplasticizer, and water. The concrete is heat-cured in a hot water bath at 90 °C for 3 days, resulting in rapid strength development. A D-optimal mixture design technique was used to optimise the mix proportions, and mathematical models were developed to predict the compressive and flexural strengths. The non-significant lack-of-fit results and the high values of coefficient of determination (R2) revealed the accuracy of the models in predicting the compressive and flexural strengths of the UHPFRC. The low values of standard deviation (SD) and coefficient of variation (CV) confirmed the consistency and reliability of the prediction models. A numerical optimisation revealed that it is possible to design a UHPFRC mixture with a lower cement content of 38.29% of the UHPFRC mix, resulting in a compressive strength of 117.62 MPa and a flexural strength of 36.32 MPa. The study reveals that integrating RHA and RTSF into UHPFRC can yield high-performance properties, offering innovative solutions for resource scarcity and environmental sustainability in the construction sector.

Out-of-plane performance of BFRP reinforced UHPC thin panel: experiment and numerical analysis

In this study, the out-of-plane performance of ultra-high performance concrete (UHPC) thin panels reinforced with basalt fiber reinforced polymer (BFRP) bars was investigated. Eight panels were tested under four-point load, with the investigating parameters including panel thickness, reinforcement ratio, and the presence of steel fibers. The failure mode, crack pattern, load vs. mid-span displacement, and reinforcement strain relationships were studied. Test results revealed that panels with a higher thickness (70 mm) exhibited 178.6% higher initial stiffness, 34.5% higher cracking loads, and 88.7% higher peak loads compared to those with a lower thickness (50 mm). The effects of a larger reinforcement ratio and the presence of steel fibers became more pronounced after concrete cracking, leading to 21.2% and 22.1% higher post-cracking stiffness, respectively. Adding steel fibers helped control the development of diagonal cracks and shifted the panel failure mode from shear to flexural failure. Based on the comparison of test results with design codes, the expressions in CAN/CSA-S806-12 were recommended for predicting the load-carrying capacity of the specimens. Furthermore, a two-dimensional finite element (FE) model was developed to reproduce the test results, which validates the adopted CDP model for UHPC and the bond-slip behaviors between UHPC and BFRP bars.

Repair overlays of modified polymer mortar containing glass powder and composite fibers-reinforced slag: mechanical properties, energy absorption, and adhesion to substrate concrete

This article aims to investigate the mechanical properties and substrate adhesion of the pull-off method in polymer mortars modified with styrene-butadiene resin polymer (SBR) containing glass powder and composite fiber-reinforced slag. Different mix designs were investigated with and without SBR, taking into account different amounts of glass powder and slag separately and in combination, along with the effect of glass, polypropylene, and steel fibers alone and in combination. The flexural performance and energy absorption of beams retrieved with these layers were also assessed. The results revealed significant differences and increases in the substrate adhesion of the restored modified polymer layers containing SBR compared to the polymer-free repair overlays. Furthermore, an improvement was observed in the adhesion performance of the repair overlay using a combination of slag and glass powder and the glass and polypropylene fiber composite. The highest adhesion was related to the modified polymer mortar design containing composite fibers of glass, polypropylene, and steel with 25% replacement of SBR polymer for 10% glass powder, 10% slag, and 5% slag with 5% glass powder. The adhesion was increased by about 3.74, 3.72, and 3.78 times compared to the repair overlay of the control design. Modified polymer mortars had a higher T150D toughness. Moreover, the energy absorption was significantly improved by the presence of SBR polymer. The highest toughness values were found in the beams restored with modified polymer mortars containing polypropylene, glass, and steel composite fibers with an increase of 48.51%–66.42% compared to the samples without polymer as a result of the pozzolans used in this mix.

Three-Dimensional Printing Limitations of Polymers Reinforced with Continuous Stainless Steel Fibres and Curvature Stiffness

This study investigates the printability limitations of 3D-printed continuous 316L stainless steel fibre-reinforced polymer composites obtained using the Materials Extrusion (MEX) technique. The objective was to better understand the geometric printing limitations of composites fabricated using continuous steel fibres, based on a combination of bending stiffness testing and piezoresistive property studies. The 0.5 mm composite filaments used in this study were obtained by co-extruding polylactic acid (PLA), with a 316 L stainless steel fibre (SSF) bundle. The composite printability limitations were evaluated by the printing of a series of ’teardrop’ shaped geometries with angles in the range from 5° to 90° and radii between 2 and 20 mm. The morphology and dimensional measurements of the resulting PLA-SSF prints were evaluated using μCT scanning, optical microscopy, and calliper measurements. Sample sets were compared and statistically examined to evaluate the repeatability, turning ability, and geometrical print limitations, along with dimensional fluctuations between designed and as-printed structures. Comparisons of the curvature bending stiffness were made with the PLA-only polymer and with 3D-printed nylon-reinforced short and long carbon fibre composites. It was demonstrated that the stainless steel composites exhibited an increase in bending stiffness at smaller radii. The change in piezoresistance response of the PLA-SSF with load applied during the curvature bending stiffness testing demonstrated that the 3D-printed composites may have the potential for use as structural health monitoring sensors.

Towards sustainable construction: Harnessing potential of pumice powder for eco-friendly concrete, augmented by hybrid fiber integration to elevate concrete performance

This study investigates the innovative use of industrial waste pozzolana, specifically pumice powder (PP), as a partial replacement for cement, combined with hybrid fibers in concrete. Seven formulations varying PP content from 10 % to 35 % were tested, identifying 15 % PP as optimal. PP improved porosity due to its fineness, leading to better homogeneity, a refined microstructure, and an optimum compressive strength of 28.8 MPa with reduced permeability, enhancing durability. Hybrid fibers, including steel fibers (SF) from waste tires and polypropylene fibers (PF), improved toughness, ductility, and resistance to brittle failure. Tests on hybrid fiber-reinforced concrete (HyFRC) mixes with 1 % and 2 % hybrid fibers showed up to an 18.09 % increase in compressive, tensile, and flexural strengths. Energy dissipation in compressive response improved by 544.20 %, while flexural and splitting responses increased by up to 299.65 % and 208.57 %. Durability assessments in hydrochloric (HCl) and sulfuric acid (H2SO4) exposure revealed the synergy of fibers and PP enhanced resistance to chemical degradation, with high PF mixes losing as little as 0.04 % strength. Scanning electron microscopy (SEM) confirmed a dense, well-bonded matrix with reduced porosity. Analytical characterizations of mixtures such as energy dispersive x-ray spectroscopy (EDX) were studied. Regression models developed using Popovic’s and Mander’s models, accurately predicted HyFRC stress-strain behavior, closely aligning with experimental results. The integration of PP and hybrid fibers not only improved mechanical properties but also extended service life in harsh environments, offering a cost-effective, sustainable concrete solution.