Fiber-reinforced Concrete Research Articles

Study on the Axial Compressive Behavior of Steel Fiber Reinforced Concrete Confined with High-Strength Rectangular Spiral Stirrup

Monotonic axial compression tests were carried out on 16 steel fiber-reinforced concrete (SFRC) columns confined by rectangular spiral stirrups. The impacts of stirrup spacing, stirrup strength, concrete strength, and cross-sectional aspect ratio on the peak load, ductility, and failure mode of these columns were analyzed. The test results demonstrate that steel fibers significantly mitigate the spalling of the concrete column’s protective layer through their bridging effect. Small spacing and high-strength spiral stirrups effectively confine the core concrete, enhancing the bearing capacity and ductility of concrete columns. Concrete strength exhibits a positive correlation with the confinement effect. However, as concrete strength increases, the rate of improvement in the confinement effect decreases. At peak compressive stress, the high-strength stirrup may not reach its yield state. Based on the test results, a method for calculating stirrup stress under the peak stress of confined concrete is proposed. A “coupling restraint coefficient” is proposed, and a constitutive model for HRSS confined steel fiber reinforced concrete is developed, considering the coupled effect of effective confinement forces in different directions. Comparative analysis shows that the constitutive model established in this paper agrees well with the experimental results and demonstrates good applicability.

Enhancement of the Shear Capacity of RC Deep Beams with Ultra-High Performance Fiber-reinforced Concrete

This research investigates the shear behavior of Reinforced Concrete (RC) deep beams strengthened with Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC). For this purpose, eight RC deep beams were fabricated and tested for failure. One beam served as a control beam (un-strengthened), while the remaining seven deep beams were strengthened utilizing various strengthening schemes. This experimental study primarily focused on the thickness of the UHPFRC layer, Steel Fiber (SF) volume fraction, and strengthening schemes (jacketing, bilateral layers, and strips exclusively in the shear zone). The experimental findings demonstrated that UHPFRC significantly enhanced the shear capacity, toughness, and stiffness of the RC deep beams. The performance of the strengthened beams exhibited improvements in ultimate shear strength, stiffness, and toughness of about 43.6%, 102.2%, and 171.3%, respectively, higher than that of the un-strengthened deep beam. UHPFRC U-jacketing is a highly effective method for strengthening the RC deep beams. Incorporating SF into the UHPFRC mixture improved the shear properties of the strengthened specimens and delayed fracture propagation. Finally, the shear capacity of the strengthened specimens was compared to the values predicted by the analytical approaches presented in earlier research.

Comparison of the Corrosion Resistance of Fiber-Reinforced Concrete with Steel and Polypropylene Fibers in an Acidic Environment

Rigid road pavements and industrial floors are not only subjected to moving traffic loads, but can also be exposed to environmental influences such as acid attack. The strength and corrosion resistance of fiber-reinforced concrete with steel fibers (15–25 kg/m3) and polypropylene fibers (2–3 kg/m3) in an acidic environment were compared. The influence of the amount and type of dispersed reinforcement on water absorption and the volume of permeable voids, which in turn characterizes the durability of fiber-reinforced concrete under the action of acids, was determined. The change in the compressive strength of the studied fiber-reinforced concrete after 12 months of exposure in an acidic environment was studied. At low dosages of fibers (15 kg/m3 for steel and 2 kg/m3 for polypropylene fibers), dispersed reinforcement has little effect on the corrosion resistance of concrete. In turn, the decrease in the compressive strength of concrete without fibers after 12 months of aging in acid medium led to a reduction in the design class of the concrete from C25/30 to C20/25. At a higher consumption of dispersed reinforcement (25–30 kg/m3 of steel fiber and 2.5–3.0 kg/m3 of polypropylene fiber), fiber-reinforced concrete had a higher corrosion resistance while maintaining the design compressive strength class C25/30. Structural changes in fiber-reinforced concrete after aging in an acidic environment were determined by X-ray diffraction analysis and compared with samples aged in water. It has been experimentally confirmed that the efficiency of polypropylene fibers in an acidic environment is not lower than that of steel fibers. However, the use of polypropylene fibers is economically advantageous.

Optimal multi-walled carbon nanotube dosage for improving the mechanical and thermoelectric characteristics of ultra-high-performance fiber-reinforced concrete

Optimal multi-walled carbon nanotube dosage for improving the mechanical and thermoelectric characteristics of ultra-high-performance fiber-reinforced concrete

Red mud utilization in fiber-reinforced 3D-printed concrete: Mechanical properties and environmental impact analysis

Red mud utilization in fiber-reinforced 3D-printed concrete: Mechanical properties and environmental impact analysis

3D printability of recycled steel fibre-reinforced ultra-high performance concrete

3D printability of recycled steel fibre-reinforced ultra-high performance concrete

Durability and mechanical performance of glass and natural fiber-reinforced concrete in acidic environments

Durability and mechanical performance of glass and natural fiber-reinforced concrete in acidic environments

Comparative Analytical study of GFRP strengthened Deep Beams

Abstract: Deep beams play a very significant role in the design of mega and as well as small structures. Sometimes for architectural purposes, buildings are designed without using any columns for a very large span. The flexural behavior of deep beams with and without web reinforcement and strengthened with GFRP strips and steel fiber-reinforced concrete (SFRC) was investigated in this paper. CFRP has been used extensively for strengthening of RCC structures. In this study GFRP strips are used as an alternative. GFRP strips have been used in place of CFRP strips. The four-point flexural response of one reference beam strengthened with high-performance fiber-reinforced concrete was investigated by carrying out a FEM analysis using ANSYS software and comparing it with theoretical calculation done as per ACI code using Strut Tie Model. The analytical and theoretical data (strain, load, etc.) are compared and discussed. For comparison the results from an earlier study [11] on CFRP strengthened deep beams is used as a reference. The RC and SFRC deep beams showed formation of compression struts. The deflection and shear stress values for FRC deep beam were comparatively lesser than RC deep beam and an increase in load carrying capacity was observed with reduced deflection. It was observed that the GFRC strengthened deep beams produced better results than the CFRC strengthened beams. SFRC-GFRP strengthened deep beam showed the highest ultimate load value compared to other options. While values of deflection were reduced in both GFRP strengthened RC and SFRC deep beams. RC-GFRP, SFRC- GFRP strengthened and SFRC showed reduction in shear stresses compared to RC deep beam.The study suggests that GFRP strengthened FRC deep beam is a better alternative to RC deep beams as it has better ultimate strength and shear stress values compared to RC deep beams and GFRP being an economical and sustainable option can be an alternative to strengthening with CFRP wraps

Experimental and Numerical Analysis of Plate–Fiber‐Reinforced Composite Double Coupling Beams

ABSTRACTCoupling beams characterized by a small span‐to‐depth ratio are particularly susceptible to brittle shear failures during seismic activities. To improve their seismic performance and alter their modes of failure, four distinct types of coupling beams were conceptualized, designed, and fabricated. The low‐cyclic reversed loading tests of the reinforced concrete (RC) single coupling beam, the RC double coupling beam, the plate‐reinforced composite (PRC) double coupling beam, and the plate–fiber‐reinforced composite (PFRC) double coupling beam were completed. The test results indicate that the double coupling beam demonstrates commendable ductility and a notable capacity for energy dissipation. It is beneficial for dissipating a significant amount of seismic energy and delaying damage to the wall limb. Adding steel plates to the double coupling beams can enhance their shear bearing capacity and prevent brittle shear failure. Substituting the matrix material with fiber‐reinforced concrete (FRC) significantly enhances the interaction between the concrete and the steel plates, leading to improved seismic performance of the coupling beams. Compared to RC double coupling beams, PFRC double coupling beams reach peak bearing capacity more quickly and exhibit an approximately 56.27% increase in bearing capacity. The axial forces exerted on the embedded steel plates within the PFRC double coupling beam are higher than those observed in the PRC double coupling beam. The use of fiber can improve the failure mode of the PRC double coupling beam. Finally, based on the experiments, a parametric analysis of the PFRC double coupling beams was conducted using ABAQUS software.

Evaluation of performance and statistical analysis of rigid pavement incorporating recycled aggregate concrete through the BBD methodology

Abstract The incorporation of recycled concrete aggregate (RCA) in the construction of rigid pavements has attracted considerable interest due to its environmental and economic benefits. A statistical method known as Response Surface Methodology (RSM) serves as an effective tool for optimizing concrete mix designs by adjusting independent variables to achieve desired characteristics. However, there is a lack of extensive research that combines modified mix designs with statistical modeling to predict the mechanical properties of concrete. Furthermore, many existing studies fail to consider the combined impacts of various factors, including cement content, water-to-cement ratio, and fine-to-coarse aggregate ratio, on the performance of concrete mixtures. This study aims to develop and optimize concrete mixtures that incorporate RCA for rigid pavements using the Box-Behnken Design method. The main goals were to forecast water absorption, compressive strength, flexural strength, split tensile strength, and slump of fiber-reinforced concrete, as well as to identify optimal mix designs that fulfill specific strength requirements. A total of 30 mixtures were tested, varying in four factors: cement content (300, 350, and 400 kg/m³), water/cementitious ratios (0.3, 0.4, and 0.5), fine/coarse aggregate ratios (0.3, 0.4, and 0.5), and silica fume content (0%, 5%, and 10% by weight of cement). RSM was employed to create predictive equations for the mechanical properties of the concrete mixtures, revealing that cement content and silica fume ratios had a significant impact on these properties, followed by the fine-to-coarse aggregate and water-to-cementitious ratios. The correlation coefficients (R²) for all predictive models exceeded 0.95, indicating a strong relationship between the independent variables and the mechanical properties. The optimal mix identified for achieving a compressive strength greater than 30 MPa and a flexural strength exceeding 4.1 MPa consisted of 365 kg/m³ of cement.

Performance Evaluation of Carbon and Basalt Fiber-Reinforced Concrete Under Microstructural Analysis, Flexural Strength Testing, and Remote Sensing Applications

Performance Evaluation of Carbon and Basalt Fiber-Reinforced Concrete Under Microstructural Analysis, Flexural Strength Testing, and Remote Sensing Applications

Assessment of Strength Enhancement and Structural Performance in Fiber-Reinforced Concrete with Varying Fiber Types and Percentages

Abstract This study focuses on the strength-enhancing capabilities of three types of fibers: steel fiber, polypropylene fiber, and asbestos fiber, which are commonly used to improve the tensile strength, durability, and load-bearing capacity of concrete structures. Each fiber type offers distinct advantages based on its physical and chemical properties. Steel fibers, for instance, are known for their high tensile strength and ability to resist cracking, while polypropylene fibers enhance the ductility and impact resistance of concrete. Asbestos fibers, though less commonly used due to health concerns, have been historically known for their fire resistance and high tensile strength.The study also explores the effects of varying fiber percentages on the mechanical behaviour of concrete structural members. By incorporating different fiber volumes into the concrete mix, the research aims to optimize the balance between strength and workability. Experimental analyses conducted on test samples reveal that the type and percentage of fiber used play a pivotal role in enhancing the overall performance of concrete. The results underscore the importance of selecting the appropriate fiber type and percentage to meet specific structural requirements.

Mechanical Properties and Prediction Based on ANN Model of Basalt and Polypropylene Fiber Reinforced Concrete

Objectives: Utilization of steel fiber increases concrete strength and ductility however, the cost of steel fiber is high and ultimately leads to an increase in the cost of concrete. Basalt fiber is a new type of fiber with high strength and toughness and can effectively replace the place of steel fibers. In this paper, concrete reinforced with polypropylene fibers and basalt fibers was tested for its mechanical properties and compared with the same predicted through a simulated model created by the Artificial Neural Network. Methods: The percentage of polypropylene fiber was kept at 0.25%, and different amounts of basalt fiber were added as 0%, 0.25%, 0.5%, 0.75%, and 1%. Based on traditional testing methods compressive strength, tensile strength, and flexural strength of normal concrete, Fiber reinforced concrete and Hybrid fiber reinforced concrete have been found. To forecast the concrete qualities, the model was simulated after the datasets were trained using a neural network fitting tool. Findings: In comparison to concrete that had only 0.25% polypropylene fiber, a hybrid fiber-reinforced concrete mix including 0.5% basalt fiber and 0.25% polypropylene fiber demonstrated a 9.69% improvement in compressive strength. In comparison to the concrete made only of polypropylene, the mix containing 0.25% polypropylene fiber and 0.75% basalt fiber showed a 26.12% increase in flexural strength and a 39.25% increase in split tensile strength. The error percentage between predicted and experimental values is below 10%. Novelty: Utilization of basalt fiber in concrete is very rare and this proposed work focused on the hybridization of basalt fiber in the place of steel fibers, which is prone to corrosion and reduces the cost of material effectively. The concrete's flexural and tensile strengths were significantly increased by the addition of basalt fibers. The mechanical characteristics of hybrid fiber-reinforced concrete are well predicted by the simulated ANN model. Keywords: Basalt fiber, Polypropylene fiber, Artificial Neural network, Fiber reinforced concrete, Hybridization

Age-Dependent Flexural Properties of Fiber Reinforced Concrete Used in Thin Overlays

This paper presents measured age-dependent flexural properties of fiber-reinforced concrete (FRC) as are used in the design of thin overlay pavements. A laboratory investigation was performed to quantify the pavement design properties, particularly residual strength ratio of FRC as a function of age. Four different types of structural macro-fibers, made of steel or polypropylene, and of different lengths or aspect ratios were investigated. Also different fiber volume contents from 0%, 0.5%, and 1.0% were studied for all fiber types and ages. The results confirmed that there is a significant agedependency to the residual strength ratio. The short steel FRC at high fiber volume content was the only mixture which showed constant residual strength ratio as a function of time. All other FRC mixtures exhibited a reduced residual strength ratio when tested at later ages.

Distribution of Fiber-Reinforcement in Thin Concrete Overlays

The spatial distribution and orientation of fibers in concrete materials can be linked with the measured fracture performance of the fiber-reinforced concrete (FRC). For FRC pavements, the improved toughness performance is used for adjusting the structural design and expected service life of the pavement. The prediction of toughness performance and pavement serviceability can be improved with a better characterization of fiber dispersion in the concrete pavement. In this research study, a flowable fibrous concrete (FFC) mixture was developed containing a synthetic macrofiber at a volume fraction higher than found with existing thin concrete pavements. This FFC mixture is anticipated to have greater toughness induced by more fiber alignment in a thinner (5 cm thickness) concrete inlay pavement. Quantification of synthetic fiber dispersion and alignment in the FFC mixture was made using x-ray computed tomography and imaging analyses. The influences of placement technique and proximity of cast or mold surfaces were investigated and found to impact the fiber spatial distribution and orientation. The image analysis revealed that the number of fibers crossing any vertical plane, which increased for FFC placed under directional flow, was directly related to the measured fracture performance. Fibers were verified to have the desired alignment, allowing more fibers to become engaged in crack opening resistance, when the FRC was placed as a thinner pavement layer and therefore resulting in a more cost-effective use of FRC for pavements.

Characterizing the Movement of Thin Concrete Overlay Panels Subject to Truck Loads

The construction of thin concrete overlays as a pavement preservation option for both asphalt and concrete pavements is gaining popularity in the U.S. To reduce costs, as well as mitigate tendencies toward curling and warping, most thin bonded and unbonded concrete overlays are constructed with either smaller panels, or shorter length panels with undoweled transverse joints. Similar to undoweled concrete pavements on grade, thin undoweled concrete overlay projects have developed faulting of the transverse joints, sometimes at an early age. Toward the efforts to understand the mechanisms causing joint faulting in thin concrete overlays, this study sought to characterize the basic surface movements of thin overlay panels, including bending, translation, and joint load transfer, when subject to heavy vehicle loads. This study utilized digital image correlation (DIC) equipment to measure the dynamic displacement along the edge of thin bonded and unbonded concrete overlay panels loaded by heavy trucks. Testing showed that as the heavy front axle first lands on a thin overlay panel, localized bending is the predominant movement, regardless of panel length. For bonded concrete overlays on asphalt, most transverse joints did not show strong load transfer behavior, even when fiber-reinforced concrete was used. In addition to characterization of the panel surface movements, general correlation to observed joint faulting and panel distress was described. The findings from this study should serve useful to the continuing determination of the mechanisms causing joint faulting in thin concrete overlays

Seismic Performance and Flexural Capacity Analysis of Embedded Steel Plate Composite Shear Wall Structure with Fiber-Reinforced Concrete in the Plastic Hinge Zone

Due to its high axial bearing capacity and good ductility, the embedded steel plate composite shear wall structure has become one of the most widely used lateral force-resisting structural members in building construction. However, bending failure is prone to occur during strong earthquakes, and the single energy dissipation mechanism of the plastic hinge zone at the bottom leads to the concentration of local wall damage. To improve the embedded steel plate composite shear wall structure, the plastic hinge zone of the composite shear wall is replaced by fiber-reinforced concrete (FRC) and analyzed by ABAQUS finite element simulation analysis. Firstly, the structural model of the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is established and the accuracy of the model is verified. Secondly, the effects of steel ratio, longitudinal reinforcement ratio, and FRC strength on the bearing capacity of composite shear walls are analyzed by numerical simulation. Finally, a method for calculating the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is proposed. It is shown that the displacement and load curves and failure modes of the model are basically consistent with the experimental results, and the model has high accuracy. The axial compression ratio and FRC strength have a great influence on the bearing capacity of composite shear walls. The calculation formula of the normal section bending capacity of the embedded steel plate composite shear wall structure with FRC in the plastic hinge zone is proposed. The calculated values of the bending capacity are in good agreement with the simulated values, which can provide a reference for its engineering application.

Multiscale Numerical Study of Enhanced Ductility Ratios and Capacity in Carbon Fiber-Reinforced Polymer Concrete Beams for Safety Design.

Rigid reinforced concrete (RC) frames are generally adopted as stiff elements to make the building structures resistant to seismic forces. However, a method has yet to be fully sought to provide earthquake resistance through optimizing beam and column performance in a rigid frame. Due to its high corrosion resistance, the integration of CFRP offers an opportunity to reduce frequent repairs and increase durability. This paper presents the structural response of CFRP beams integrated into rigid frames when subjected to seismic events. Without any design provision for CFRP systems in extreme events, multiscale simulations and parametric analyses were performed to optimize the residual state and global performance. Macroparameters, represented by the ductility ratio and microfactors, have been analyzed using a customized version of the modified compression field theory (MCFT). The main parameters considered were reinforcement under tension and compression, strength of concrete, height-to-width ratio, section cover, and confinement level, all of which are important to understand their influence on seismic performance. The parametric analysis results highlight the increased ductility and higher load-carrying capacity of the CFRP-reinforced tested component compared to the RC component. These results shed light on the possibility of designing CFRP-reinforced concrete components that could improve ductile frames with increased energy dissipation and be suitable for applications in non-corrosive seismic-resistant buildings. This also shows reduced brittleness and enhancement in the failure mode. Numerical simulations and experimental results showed a strong correlation with a deviation of about 8.3%, underlining the reliability of the proposed approach for designing seismic-resistant CFRP-reinforced structures.

An effect of nano alumina and nano titanium di oxide with polypropylene fiber on the concrete: mechanical and durability study

For a long time, researchers have worked to improve the qualities of cement-based mixes. Because of their small size, strong reactivity, and huge surface area, nanoparticles are becoming more and more regarded as one of the greatest substitutes for cement because of their capacity to increase durability and strength. This work presents the results of an experimental investigation into the strength and durability properties of fiber-reinforced concretes with polypropylene (PP) fibers added to the concrete by volume and nano Al2O3 and nano TiO2 are used as partial substitutes for cement. Nano Al2O3 and nano TiO2 particles used ranged in size from 30 to 300 nm. The specimens were cast using cement blended nano Al2O3 and nano TiO2 percentages of 1%, 2%, 3%, and 4% by weight of cement. M55 grade concrete was employed for the casting process. The addition of PP fibers to the concrete was 0.5% by volume. The specimens underwent a battery of mechanical tests, including microstructural testing, compression testing, split tensile strength testing, and rupture modulus testing. Furthermore, tests for durability factors such as porosity, sorptivity, and degradation were conducted, and the findings are presented. By comparing the outcomes, it was shown that the inclusion of 0.5% PP fibers and 2% nano Al2O3 or nano TiO2 improved the mechanical qualities, but a decrease followed this in strength. The findings demonstrated that 2% nano Al2O3 combined with 0.5% PP fiber had a greater mechanical strength than 2% nano TiO2.

Optimization of Mechanical Properties and Durability of Steel Fiber-Reinforced Concrete by Nano CaCO3 and Nano TiC to Improve Material Sustainability

To meet the growing demand for sustainable building materials in modern construction projects, nanomaterials are widely used in concrete to improve its mechanical properties, durability, and environmental adaptability. The effects of different calcium carbonate nanoparticles (NC) and titanium carbide nanoparticles (NT) substitution rates (0%, 0.5%, 1% and 1.5%) on the mechanical and durability properties of steel fiber-reinforced concrete (SFRC) were analyzed by experimental studies. We also analyzed the evolution of the microstructure, chemical composition, and the evolution of functional groups of concrete by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The results demonstrated that NC replacement of 0.5% and NT replacement of 1% was the optimal combination for the preparation of composite concrete. Compared to SFRC with 0% substitution for both NC and NT (CG), the 28-day compressive strength of NC0.5NT1 increased by 35.5%, the flexural strength increased by 26.5%, and the splitting tensile strength increased by 16.3%. The durability performance of SFRC has been significantly improved. After 150 freeze–thaw cycles, the quality loss rate of SFRC cured for 28 days decreased by 40.6%, and the relative dynamic elastic modulus increased by 7.7%. Microscopic analysis indicates that an appropriate amount of NC and NT replacing cement improves the hydration reaction process of SFRC, increases the content of chemically more stable C-S-H gel, but does not change the types of hydration products of the cement. NC and NT have a filling effect, improving the pore structure of concrete, which helps enhance the mechanical and durability performance of concrete. The results of the study provide a theoretical basis for the application of NC and NT as reinforcing particles for cementitious materials in sustainable building materials.