Fiber Concrete Research Articles

The effect of surface roughness and a steel anchor on the direct-shear bond between existing concrete and new concrete

The strengthening of concrete structures must consider the transfer of various forces at the joint, especially the direct-shear bond between existing concrete and new concrete, which is dependent on several variables. This research focused on the investigation of the direct-shear bond at the joint of concrete samples having a cylindrical shape with a diameter of 150 mm and a length of 300 mm. The joint of concrete was in the middle of the sample and was prepared by casting new concrete on the existing concrete. A steel anchor was installed in the middle of the joint with an embedded length of 75 mm. The studied variables included the surface roughness of the existing concrete, the size of the anchor, and the use of steel fibers in the new concrete. It was found from the tests that the preparation of the existing concrete surface to be rougher, which was less than the minimum roughness specified by various codes, could increase the direct-shear bond by 210–260 % and the displacement of concrete samples by 140–200 % compared to an as-cast surface. The larger the size of the anchor, the greater the cohesion bond and the first-cracking bond, but these bonds would not follow the mechanical effect of the larger cross-sectional area. The use of steel fibers in the new concrete hardly increased the direct-shear bond and displacement. Furthermore, the results of statistical data analysis showed that the variables significantly influencing the direct-shear bond at a 95 % confidence level included the roughness of the existing concrete surface and the installation of a steel anchor. Very good agreement was observed between the test results and the predicted equations for cohesion bond and first-cracking bond, with R2 values of 0.9284 and 0.8948, respectively. When comparing the equations provided by the various codes for determining interface shear resistance, the values obtained from ASSTHO and Eurocode 2 codes were closer to test results than those of the ACI 318 code because both codes have considered both cohesion and friction at the interface.

Adding Fibers for Improving the Properties of Concrete and its Impact Resistance

This study is summarized in the search for the possibility of using fiberglass to improve the bending resistance of beams, and to obtain results that can be analyzed and some recommendations can be drawn, 18 concrete beams with a length of 70 cm and a cross-sectional area of 10x20 cm were cast and tested, five of them contain main reinforcement in the tension area and fiber-reinforced concrete that was placed in the casting mold at different depths from the lower surface level of the beams from the depth of the beam, and a beam without fibers was cast as a model for comparison, and the fifth reinforced with beams only in the shear areas was also used as a model for comparison, and 4 other beams not reinforced with main steel in the tension area and reinforced concrete for the depth of the beam and another containing normal concrete. Through this study, it became clear that the presence of fiber concrete in the compression zone for structural elements that are subject to bending clearly affects the structural behavior, as the amount of sagging increases, especially under the influence of weak loads, compared to the value of the total collapse load obtained from one of the beams that were tested.

Impact-Driven Penetration of Multi-Strength Fiber Concrete Pyramid-Prismatic Piles

The article focuses on studying the impact-driven penetration of multi-strength fibroconcrete pyramid-prismatic piles. The research object includes multi-strength pyramid-prismatic piles with varying types of reinforcement and different levels of concrete compressive strength. The aim of the study is to experimentally investigate the enhancement of pile impact resistance through the differentiated selection of concrete strength based on the dynamic stresses in the pile shaft caused by impact forces. As a result of the experimental studies on the piles, it was found that the difference in energy costs for driving them does not exceed 3.7–4.1%, proving the insignificant influence of the type of reinforcement and fiber concrete strength on the energy expenditure during driving. At the same time, it was established that the type of reinforcement and the type of fiber significantly affect the strength and impact-resistant properties of the pile shaft, ensuring defect-free driving. For example, the defectiveness (e.g., chips, cracks, potholes, spalling) of the head of the steel fiber concrete (SFC) pile reaches 57.5%, while for the polypropylene fiber concrete (PFC) pile it does not exceed 5.2%, demonstrating the advantages of using polypropylene fiber under impact conditions.

Mechanical Performance of Steel-PVA Hybrid Fiber Concrete After Elevated Temperature Exposure

Mechanical Performance of Steel-PVA Hybrid Fiber Concrete After Elevated Temperature Exposure

Development of a novel DNA-shaped steel fiber and its performance on fresh and hardened concrete

Adding small discrete random fibers in concrete has enhanced concrete behavior in various ways. Diverse types of fibers are available in terms of materials, shapes, and applications. Different shapes of steel fibers are available like hooked ends, crimped, stranded, helix, spherical, etc. Having the grade of concrete and the fiber dosage added as constant, the structural behavior and performance will vary for different types of fibers. It shows that the shape of fiber has a great role in enhancing the properties of concrete. The challenges in existing two-dimensional steel fibers in concrete like the mechanism and contribution of fiber in arresting cracks developed in all directions and balling effect can be overcome by a new type of three-dimensional steel fiber. A novel three-dimensional DNA-shaped steel fiber is designed and fabricated. This paper presents the fresh concrete and hardened concrete properties of DNA-shaped fiber-reinforced concrete (DNAFRC) and compares it with hooked-end fiber-reinforced concrete (HEFRC) by incorporating a volume fraction varying from 0.5 to 2% of grade M30 concrete and aspect ratio of 60 for both fibers. The fresh properties of concrete were evaluated by measuring the slump for workability and wash-out test for the fiber distribution. The hardened concrete properties were assessed by compressive, split tensile, flexural, impact, shear, and pull-out strength which demonstrated considerable increase by 5% at 1.5% volume fraction, 32%, 136%, 21%, and 35% at 2% volume fraction respectively for DNAFRC than the HEFRC. Scanning Electronic Microscope (SEM) images were studied on failed samples to evaluate the bonding of DNA fiber with concrete.

Bio-inspired widening concrete using cellulose nanofiber to enhance multiscale Fiber–Matrix interface

The cracking issue at the bonded interface due to the differing shrinkage performances of newly poured concrete and existing concrete poses a significant threat to the safe service of composite structures. Inspired by the musculoskeletal system, we propose the use of multiscale hybrid reinforced concrete materials, incorporating basalt fiber (BF), polypropylene (PP) fiber, and cellulose nanofiber (CNF), for bridge widening structures. Experimental investigations were carried out to assess the bond splitting tensile strength, diagonal shear strength, crack resistance, development of drying shrinkage deformation, and the propagation behavior of restrained shrinkage-induced cracks in both new and old concrete reinforced with single and hybrid combinations of BF, PP fiber, and CNF. The microstructure, phase composition, and pore structure evolution of BF, PP fiber, and CNF-reinforced concrete were observed and analyzed using scanning electron microscopy, thermogravimetric and derivative thermogravimetric analysis, nuclear magnetic resonance, and mercury intrusion porosimetry. The results indicate that the incorporation of BF, PP fiber, and CNF exhibits excellent synergistic effects, improving the bond and shrinkage performance of the concrete interface. As the CNF content increases, the macro fiber–matrix interface improves. This bio-inspired work will contribute to the development of strong, tough, and sustainable concrete for bridge widening structures.

Prediction of mechanical properties of basalt fiber concrete using hybrid recurrent neural networks based on freeze-thaw damage quantification

Prediction of mechanical properties of basalt fiber concrete using hybrid recurrent neural networks based on freeze-thaw damage quantification

Investigating the Mechanical Characteristics and Fracture Morphologies of Basalt Fiber Concrete: Insights from Uniaxial Compression Tests and Meshless Numerical Simulations.

To explore the mechanical properties and fracture modes of basalt fiber-reinforced concrete, single-doped and hybrid-doped basalt fiber-reinforced concrete was prepared, and uniaxial failure tests under different basalt fiber-reinforced concrete contents were carried out. At the same time, the smooth kernel function in the traditional SPH method was improved, and the basalt fiber random generation algorithm was embedded in the SPH program to realize the simulation of the progressive failure of basalt fiber-reinforced concrete. The results show that under the circumstance with no basalt fiber, the specimen final failure mode is damage on the upper and lower surface, as well as the side edge, while the interior of the specimen center is basically intact, indicating that there is an obvious stress concentration phenomenon on the upper and lower surface when the specimen is compressed. Under the circumstance with basalt fiber, longitudinal cracks begin to appear inside the specimen. With the increase in the content, the crack location gradually develops from the edge to the middle, and the crack number gradually increases. This indicates that appropriately increasing the fiber content in concrete may improve the stress state of concrete, change the eccentric compression to axial compression, and indirectly increase the compressive strength of concrete. The numerical simulation results are consistent with the test results, verifying the rationality of the numerical simulation algorithm. For the concrete model without the basalt fiber, shear cracks are generated around the model. For the concrete model with basalt fiber, in addition to shear cracks, the tensile cracks generated at the basalt fiber inside the model eventually lead to the splitting failure of the model. The strength of concrete samples with basalt content of 0.1%, 0.2%, and 0.3% is increased by 1.69%, 5.10%, and 4.31%, respectively, compared to the concrete sample without basalt fiber. It can be seen that with the increase in the content of single-doped basalt fiber, the concrete strength is improved to a certain extent, but the improvement degree is not high; For hybrid-doped basalt fiber-reinforced concrete, the strength of concrete samples with basalt content of 0.1%, 0.2%, and 0.3% is increased by 14.51%, 15.02%, and 30.31%, respectively, compared to the concrete sample without basalt fiber. Therefore, compared with the single-doped basalt fiber process, hybrid doping is easier to improve the strength of concrete.

The high ductility performance of energy-absorbing buffer support materials

In order to study the realization of high ductility performance of foam fiber concrete (FFC) as energy-absorbing buffer support material, a series of samples were prepared based on the optimal mix ratio of orthogonal test. The uniaxial compression test was carried out to obtain the stress–strain curve and energy absorption curve. The strain capacity and macroscopic cracking process were revealed by digital image correlation (DIC). The mechanical performance of the admixture in the process of achieving high ductility performance was captured by scanning electron microscopy (SEM). The test results show that the average strength of FFC in the platform stage is 73.95% of the peak strength, and it can effectively absorb external energy as an energy-absorbing buffer support material. Foam, waste polystyrene particles and PVA fiber were the key factors to realize the high ductility of FFC.

Artificial neural networks and noncontact microwave NDT for evaluation of polypropylene fiber concrete

Artificial neural networks and noncontact microwave NDT for evaluation of polypropylene fiber concrete

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.

Effect of Compressive Strength and Tensile Strength Value on Fiber Concrete Using Bendrat Wire Fibers

Concrete is a material used in modern construction and is a very important component in the manufacture of structures. Concrete has advantages, but also disadvantages, namely low tensile strength. To increase the tensile strength of concrete, fibers are added to the mix. One of the efforts made to increase the tensile strength of concrete is the addition of fibers to the fiber-concrete mixture. The purpose of this study is to examine the compressive strength and tensile strength values in fiber concrete if added with variations in fiber addition. An innovation in increasing the value of mechanical quantities in concrete is the use of bent wire fibers as a mixture in fiber concrete. This material is taken from former pieces in construction projects to connect steel reinforcement with Sengkang reinforcement and is also widely found in building shops. The fibers were also analyzed for microstructure using SEM (Scanning Electron Microstructure) tools. The length of this bent wire fiber is 13 mm with a diameter of 0.82 mm and has a minimum tensile strength value of 334.5 MPa. The variations in the addition of these bent wire fibers are 0%, 3%, 6%, and 9% of the total weight of the steel fiber. The soaking life of concrete is 7 days, 14 days, and 28 days. The results of this study show that the more variations in the addition of bent wire fibers, the compressive strength value of concrete and the tensile strength value of concrete will also increase. It can be seen that fiber concrete with an immersion life of 28 days with a variation of 9% added bent wire fiber has a maximum compressive strength value of concrete which is 63,645 MPa and a maximum value of tensile strength of 3,294 MP.

Physical and mechanical properties of concrete containing plastic tube fibers

Plastic tube fibers (PTFs) are one form of plastic waste resulting from the production of plastic mats that end up in the landfill. Until today, no attempt has been made to explore the applicability of PTFs as a construction material for a circular economy. This paper investigates the applicability of PTFs as fibers in fiber-reinforced concrete (FRC) production. A series of tests are carried out to investigate the effects of volume fractions (VFs) and the length of the fibers on the physical and mechanical properties of FRC-containing PTFs. The effects of the length and VFs on the unit weight, compressive strength, flexural strength, tensile strength, pulse velocity, thermal conductivity, and microstructure of FRC are examined. Three different lengths of fibers of 20 mm, 30 mm, and 50 mm, and VFs of PTFs of 0 %, 0.5 %, 1 %, and 1.5 % are studied. Results show that although the mechanical properties of concrete decrease as the VFs increase from 0 % to 1.5 %, the rate of reduction becomes smaller as the length of the fiber becomes larger. The maximum reduction of compressive, tensile, and flexural strength was found to be as high as 35 %, 25 %, and 35 % compared to the control sample obtained for 20 mm fiber length having 1.5 % VFs. Formulas to predict the tensile and flexural strengths of concrete containing PTFs as a function of the compressive strength are proposed and found to be providing satisfactory results. From a microscopic view, it is seen that the sample containing higher VFs shows less density and homogeneity of concrete which leads to an increase in the micropores of the concrete. Furthermore, the ultrasonic pulse velocity and attenuation coefficient decrease as the VFs of PTFs increase.

Exploration of Carbon Fiber Concrete with Silica Fume Admixture for Potential Application in Rigid Pavement Systems

Concrete is a crucial material in civil engineering construction, but its traditional components, coarse and fine aggregate, are becoming increasingly expensive and scarce. This study aimed to investigate the potential of replacing cement with silica fumes and fine aggregate with carbon fibers to improve concrete's hardened properties. Different concrete mixes were created with varying percentages of these replacements. The resulting concrete specimens were tested for compression, split, and flexural strength after curing periods of 7 and 28 days.

Bond‐slip behavior between polypropylene fiber concrete and corroded reinforcement

AbstractIn this paper, the bond‐slip behavior and bond‐slip constitutive model of corroded reinforcement embedded in polypropylene fiber‐reinforced concrete (PFRC) were investigated. The central pullout test was conducted for 36 specimens. The effects of the corrosion level of reinforcement and the volume fraction of polypropylene (PP) fibers in concrete on the damage mode and bond‐slip process between reinforcement and concrete were studied. Based on the experimental data, a modified bond‐slip constitutive model considering the corrosion level of reinforcement and the volume fraction of PP fibers in concrete was proposed, and the proposed modified bond‐slip constitutive model was used in finite element analysis. The results showed that the addition of PP fibers effectively improved the ultimate bond strength, peak slip and bond toughness of reinforcement and concrete. The enhancement of the bonding properties of the specimens by the PP fibers remained significant after the reinforcement was corroded. The proposed modified bond‐slip constitutive model agreed well with the experimental results. The validity of the proposed model was further verified by finite element analysis.

A study of the effect of coconut fiber on reinforced concrete beams subjected to combined bending and shear

This review paper examines the impact of coconut fiber reinforcement on the behavior of reinforced concrete beams subjected to combined bending and shear. Coconut fibers, also known as coir fibers, are a sustainable and cost-effective alternative to traditional steel reinforcement. The use of coconut fibers in concrete has shown promise in enhancing the ductility, energy absorption capacity, fracture resistance, and durability of concrete structures. The study highlights the mechanical properties and applications of coconut fiber reinforced concrete (CFRC) and investigates the effects of varying fiber content on concrete performance. Factors affecting the properties of fiber-reinforced concrete, such as the relative fiber matrix index, volume of fibers, aspect ratio of fibers, fiber orientation, workability, compaction, size of coarse aggregate, and mixing techniques, are also discussed. Understanding these factors is crucial for designing and constructing durable and sustainable concrete structures.

The efficient waste-based fine-grained fibre concretes for 3D printing

This study investigates the development of optimized 3D printing mixes using Portland cement grades PC 400-D0 and PC 500-D0, combined with fly ash and various fibers such as polypropylene (PP), polyethylene (PE), and nylon, to enhance the mechanical properties and durability of printed structures. The primary aim is to create a mix that ensures sufficient flowability during the printing process while achieving high tensile strength and resistance to cracking. The methodology involved a series of mix designs with varying proportions of cement, fly ash, and fibers, followed by testing for rheology, compressive strength, and durability. Key findings include achieving a compressive strength of up to 50 MPa and a tensile strength improvement of 20 % with the optimal fiber combination. The incorporation of fly ash resulted in a 15 % reduction in material costs and a significant improvement in workability. The practical implications of this research are substantial for the construction industry, particularly in the context of sustainable and efficient building practices. The optimized mix designs not only reduce costs but also enhance the longevity and structural integrity of 3D printed elements, making them viable for large-scale construction projects. This study provides a foundation for further exploration into advanced 3D printing materials.

Enhancing load capacity of reinforced concrete columns using high strength concrete and fiber reinforcement

Strengthening of structural elements is sometimes necessary for architectural purposes to withstand additional loads without cross-section enlargement. This study evaluates the structural performance of reinforced concrete columns toughened using high-strength concrete, steel fiber concrete of 1% volume fraction, and near-surface mounted NSM steel or carbon fiber reinforced polymer CFRP bars. Five columns of 0.15×0.15×1 m were cast and axially loaded till failure. The investigational consequences revealed that a load-carrying capacity and stiffness augmented by 55.1 and 91.1% when the compressive strength is 1.5 times the normal with a ductility decrease of 28.2% whereas steel fiber concrete raised them by 34.3, 6.4, and 11.6%. In addition, NSM steel or CFRP bars exhibited ultimate loads and stiffness 13.6 to 29.7% and 17.2 to 21.7% higher than the non-strengthened column. However, the ductility decreased by 2.5 to 12.4%.

Experimental and Modeling Analysis of Polypropylene Fiber Reinforced Concrete Subjected to Alkali Attack and Freeze-Thaw Cycling Effect.

The durability of concrete materials in harsh environmental conditions, particularly in cold regions, has garnered significant attention in civil engineering research in recent years. Concrete structures in these areas are often damaged by the combined effects of alkali-silica reaction (ASR) and freeze-thaw cycles, leading to structural cracks and significant safety hazards. Numerous studies have demonstrated that polypropylene fiber concrete exhibits excellent crack resistance and durability, making it promising for applications in cold regions. This study elucidates the impact of alkali content on concrete durability by comparing the mechanical properties and durability of different alkali-aggregate concretes. The principal experimental methodologies employed include freeze-thaw cycle experiments, which examine patterns of mass loss; fluctuations in the dynamic modulus of elasticity; and changes in mechanical properties before and after freeze cycles. The findings indicate that increased alkali content in concrete reduces its strength and durability. At 100% alkali-aggregate content, compressive strength decreases by 35.5%, flexural strength by 32.9%, mass loss increases by 35.85%, relative dynamic elastic modulus by 39.4%, and residual strength by 97.28%, indicating higher alkali content leads to diminished durability. Additionally, this paper introduces a constitutive damage model, validated by a strong correlation with experimental stress-strain curves, to effectively depict the stress-strain relationship of concrete under varying alkali contents. This research contributes to a broader understanding of concrete durability in cold climates and guides the selection of materials for sustainable construction in such environments.

Experimental investigation of heat-damaged reinforced concrete columns strengthened with different schemes

This paper experimentally investigates the efficacy of two jacketing techniques in the rehabilitation of square and circular reinforced concrete (RC) columns that were exposed to highly elevated temperatures. Twenty-four RC columns were tested under an axial compression load, which was divided into three groups. The first group consisted of the control specimens without applying any strengthening approach. Group 2 consisted of the columns with the strengthening configuration of near-surface-mounted (NSM) rebars and carbon fiber-reinforced polymer (CFRP) layers. Regarding the third group, columns were strengthened using two layers of welded-wire mesh (WWM) and ultra-high-performance fiber concrete (UHPFC) jacketing. Four columns from each group were subjected to an elevated temperature of 600 °C for a duration of 3 h, while the remaining half were subjected to room temperature. The results showed that after three hours at a temperature of 600 °C, both strengthening schemes successfully restored and exceeded the initial load-carrying capability of all columns. Utilizing WWM with UHPFC jacketing as new strengthening technique proved to be the most efficient method for reinstating the load-carrying capability of circular columns (+321.8 %) and square columns (+140.6 %) that were subjected to high temperatures. Additionally, an analytical model was proposed to estimate the ultimate load capacity of RC columns after rehabilitation.