Strength Of Bars Research Articles

Design, preparation and mechanical properties of novel glass fiber reinforced polypropylene bending bars

Fiber reinforced thermoplastic composite bars offered the advantages of repeated molding, high toughness, and recyclability, making them a promising alternative to steel bars. For the stirrups applications in concrete structures, it was essential to develop efficient bending technologies for producing high-quality thermoplastic bending bars. In the present paper, the bending properties of glass fiber reinforced polypropylene (GFRPP) composite bars were investigated by experimental and theoretical methods. A novel bending fixture of GFRPP bars was specifically designed for GFRPP bars to ensure the reliable bending of the bars. Finite element simulation was employed to analyze the stress distribution of GFRPP bars, providing valuable insights into their mechanical behavior. Additionally, a bending strength model was developed based on the material mechanics, offering a theoretical framework for understanding and predicting the bending strength of GFRPP bars. Finally, the bending mechanism of bars was further revealed according to experimental and theoretical findings. The results of the study demonstrated that the specially designed bending fixture was successful in minimizing damage to the bending section of the GFRPP bars, leading to a significant improvement in bending strength retention of up to 43.2 %. Furthermore, the theoretical results and experimental test have a good agreement in terms of stress distribution and failure mode. The maximum strain in the transition zone between the straight section and the bending section of the GFRPP bars was nearly double that of the straight section at the same stress levels. With the increase of bending radius to diameter ratio from 3.0 to 7.0, the tensile strength of GFRPP bending bars increased by ∼7.9 %. The study identified the transition area between the bending section and straight section of GFRPP bars as the most critical failure point. The strength degradation mechanism during the bending were attributed to the shrinkage and torsion of inner fibers owing to the compression caused the local stress concentration, which caused the inner resin matrix to crack and interface debonding of fiber/resin, leading to the premature tensile failure.

Bond performance of NSM FRP–concrete interfaces with epoxy under chloride‐salt conditioned environments

AbstractConcrete in coastal areas is susceptible to structural damage caused by corrosion and expansion of reinforcement. Near‐surface mounted (NSM) fiber‐reinforced polymer (FRP) bars have become effective for strengthening damaged reinforced concrete structures. The bonding performance of NSM FRP bars in concrete is a key factor limiting their application and promotion in civil engineering. In this study, the influences of the conditioned environment, such as the chloride salt concentration, immersion time, and bond length of the FRP bar, on the bonding performance were investigated experimentally. First, material properties in a conditioned environment were studied. Subsequently, the failure mode, bond stress–slip curve, and bond strength of the NSM FRP bar in concrete were investigated. Finally, the microstructure and chemical composition of the materials were revealed using scanning electron microscopy and energy‐dispersive spectroscopy (EDS) images of the materials under environmental conditions. The transfer mechanism of NSM FRP bars in concrete with epoxy was revealed. The results showed that the failure modes of the pullout specimens can be divided into epoxy splitting failure and basalt fiber‐reinforced polymer (BFRP) pulling failure. The chloride‐salt concentration was a critical factor affecting the bond properties, and the longer the bond length, the lower the bond strength. The microstructure clearly shows that the degradation of the bonding behavior at the interface of the NSM FRP bar in concrete in a conditioned environment is attributable primarily to the resin damage of the epoxy, resulting in pit corrosion. There was no significant damage to the fibers in the FRP bar, and the degradation was primarily due to resin matrix damage and interfacial debonding. The EDS results showed that the degradation of the epoxy resin and BFRP bars was caused by CO bond and SiO bond fractures, respectively.

Experimental Study of Dimensional Effects on Tensile Strength of GFRP Bars

This study explores the mechanical properties of Glass Fiber-Reinforced Polymer (GFRP), a high-performance composite material, focusing on how varying diameters affect its tensile strength, modulus, and elongation. Experimental data obtained from three sets of tensile tests on 10, 12, and 25 mm bars helped establish a stress–strain relationship for GFRP reinforcements, considering diameter changes, and a formula for calculating the ultimate tensile strength based on diameter. Utilizing the weakest chain theory and the Weibull distribution, the research found that GFRP’s tensile strength diminished with increased diameter, while the elastic modulus behaves oppositely. The analysis, grounded in the weakest chain theory, identifies the specimen’s effective volume as a critical factor in the size effect of GFRP bars. Moreover, the study proves a significant size effect on GFRP’s tensile properties, validating the theory’s application in predicting the strength of GFRP bars of varying sizes and recommending a specimen length range of 30–40 times its diameter for standardization purposes.

Investigation of the bond properties between hybrid fiberreinforced concrete and BFRP bars after exposure to high temperature

This research investigated the bond properties at high temperatures and with hybrid fiber addition between basalt fiber reinforced polymer (BFRP) bars and hybrid fiber-reinforced concrete (HFRC). The tensile strength and appearance morphology of BFRP bars were analyzed. Used scanning electron microscopy (SEM) to examine the microscopic morphology and used the bond-slip constitutive model to fit the bond-slip curves. When BFRP bars after exposed to 300 °C, their tensile strength dropped by 42%. With the increasing temperature, the bond strength and stiffness of normal concrete (NC) specimens decreased by 27.3 % and 67.5 %, respectively, while HFRC specimens decreased by 20.8 % and 55 %, respectively. Hybrid fibers increased the bond strength and stiffness of HFRC specimens by 27.1 % and 49.1 %, respectively. The best fitting models were the Malvar model and the Continuous Curve model.

Bond-slip model of headed bar and its application to component-based model for precast concrete joints under accidental loads

This study focused on investigating bond-slip behaviour of headed bars embedded in well-confined concrete. Test results based on eight pull-out specimens under displacement-controlled incremental loading showed that recommended development lengths from ACI318–19 are conservative in developing ultimate strength of headed bars associated with smaller slips than straight bars. Moreover, it was found that different (but sufficiently long) embedment lengths had a significant effect on the free-end slip but negligible effect on the loaded-end slip of headed bars. Additionally, the study highlighted the significance of head bearing in anchorage formation, especially during inelastic stage when bond strength had deteriorated. To address inaccuracy in predicting structural behaviour caused by inadequate anchorage strength of headed bars, a macro bond-slip model was proposed based on correlation in strain distribution obtained from the pull-out tests. Subsequently, the proposed model was incorporated into a component-based model (CBM) and validated against test results of PC joints under seismic loading. A numerical investigation using the validated CBM was conducted to study behaviour of exterior PC joints with headed bars and special detailing. These included Type X joint with X-bent bars and plastic hinge relocation (PHR), and Type A joint with an additional bar layer (ABL) in the beam-joint region, subjected to extreme loads such as seismic action or progressive collapse. The results revealed that seismic behaviour of exterior joints was governed by ductile failure of the beam at the PHR and vertical joint interface in Type X and Type A joints, respectively. Progressive collapse was primarily caused by column failure, with flexural and catenary action effectively preventing collapse. Notably, under both loading conditions, presence of ABL in Type A joint and X-bent bars with PHR in Type X joint improves flexural strength of beams at critical sections and joint shear strength, ultimately enhancing structural performance of joints. Design recommendations include replacing hooked bars with headed bars as well as implementing X-bent bars with PHR and ABL in PC joints. The authors advocate the strong-column-weak-beam design approach as an effective measure to prevent progressive collapse.

Study on the calculation method of the maximum number of bonded steel plates at the bottom of reinforced concrete beams

Purpose When the reinforced concrete beams are reinforced by bonding steel plates to the bottom, excessive use of steel plates will make the reinforced concrete beams become super-reinforced beams, and there are security risks in the actual use of super-reinforced beams. In order to avoid the occurrence of this situation, the purpose of this paper is to study the calculation method of the maximum number of bonded steel plates to reinforce reinforced concrete beams.Design/methodology/approach First of all, when establishing the limit failure state of the reinforced member, this paper comprehensively considers the role of the tensile steel bar and steel plate and takes the load effect before reinforcement as the negative contribution of the maximum number of bonded steel plates that can be used for reinforcement. Through the definition of the equivalent tensile strength, equivalent elastic modulus and equivalent yield strain of the tensile steel bar and steel plate, a method to determine the relative limit compression zone height of the reinforced member is obtained. Second, based on the maximum ratio of (reinforcement + steel plate), the relative limit compression zone height and the equivalent tensile strength of the tensile steel bar and steel plate of the reinforced member, the calculation method of the maximum number of bonded steel plates is derived. Then, the static load test of the test beam is carried out and the corresponding numerical model is established, and the reliability of the numerical model is verified by comparison. Finally, the accuracy of the calculation method of the maximum number of bonded steel plates is proved by the numerical model.Findings The numerical simulation results show that when the steel plate width is 800 mm and the thickness is 1–4 mm, the reinforced concrete beam has a delayed yield platform when it reaches the limit state, and the failure mode conforms to the basic stress characteristics of the balanced-reinforced beam. When the steel plate thickness is 5–8 mm, the sudden failure occurs without obvious warning when the reinforced concrete beam reaches the limit state. The failure mode conforms to the basic mechanical characteristics of the super-reinforced beam failure, and the bending moment of the beam failure depends only on the compressive strength of the concrete. The results of the calculation and analysis show that the maximum number of bonded steel plates for reinforced concrete beams in this experiment is 3,487 mm2. When the width of the steel plate is 800 mm, the maximum thickness of the steel plate can be 4.36 mm. That is, when the thickness of the steel plate, the reinforced concrete beam is still the balanced-reinforced beam. When the thickness of the steel plate, the reinforced concrete beam will become a super-reinforced beam after reinforcement. The calculation results are in good agreement with the numerical simulation results, which proves the accuracy of the calculation method.Originality/value This paper presents a method for calculating the maximum number of steel plates attached to the bottom of reinforced concrete beams. First, based on the experimental research, the failure mode of reinforced concrete beams with different number of steel plates is simulated by the numerical model, and then the result of the calculation method is compared with the result of the numerical simulation to ensure the accuracy of the calculation method of the maximum number of bonded steel plates. And the study does not require a large number of experimental samples, which has a certain economy. The research result can be used to control the number of steel plates in similar reinforcement designs.

Research Progress of Bond Slip at The Interface of FRP Bars and Concrete

The bond between FRP bars and concrete is the key to the strength and durability of FRP reinforced concrete members, and it is the decisive factor to make full use of the light, high strength and corrosion resistance of FRP bars. In this paper, according to the research results of bond properties of FRP bars and concrete at home and abroad, the paper analyzes four aspects, including test method of bond properties of FRP bars, bond mechanism, factors affecting bond properties of FRP bars and bond slip constitutive relationship model. The shortcomings of the existing research results and the problems to be solved are analyzed and compared comprehensively. At last, some references and suggestions are provided for the further research and application of FRP reinforced concrete structures.

Size effect on compressive behavior of GFRP bars

In the last three decades, studies investigating the use of Glass Fiber Reinforced Polymer (GFRP) bars as an alternative to conventional steel rebars have increased due to their corrosive resistance. In addition to corrosion resistance, GFRP bars utilize high specific tensile strength, which makes them highly desirable in civil engineering applications. However, major design guidelines for GFRP-reinforced concrete structures currently do not consider their compressive contribution. Nevertheless, there is a growing trend in utilizing GFRP bars as compressive elements, driven by various studies demonstrating their ability to bear compressive loads effectively. This increasing demand underscores the need to comprehend the mechanical properties of GFRP bars, particularly in terms of their compressive behavior. Furthermore, a standardized test method to evaluate their compressive properties has not yet been developed. Addressing these gaps, this research paper focuses on investigating the influence of specimen size on the compressive strength of GFRP bars, specifically emphasizing on the compressive properties of GFRP bars. Compressive tests were conducted on GFRP specimens with varying diameters while maintaining a constant slenderness ratio. The findings from these compression tests shed light on the critical role of size in the compressive behavior of GFRP. This research emphasizes the importance of considering size as a significant parameter in designing mechanical properties for GFRP reinforcements.

Investigation of Residual Strength of GFRP Bar Reinforced Concrete Beams with Recycled Materials Under Elevated Temperature

Investigation of Residual Strength of GFRP Bar Reinforced Concrete Beams with Recycled Materials Under Elevated Temperature

The bar pattern speed of the Large Magellanic Cloud

Context. The internal kinematics of the Large Magellanic Cloud (LMC) have been studied in unprecedented depth thanks to the excellent quality of the Gaia mission data, thus revealing the disc’s non-axisymmetric structure. Aims. We seek to constrain the LMC bar pattern speed using the astrometric and spectroscopic data from the Gaia mission. Methods. We applied three methods to evaluate the bar pattern speed by measuring it via: the Tremaine-Weinberg (TW) method, the Dehnen method, and a bisymmetric velocity (BV) model. These methods provide additional information on the bar properties, such as the corotation radius as well as the bar length and strength. We tested the validity of the methods with numerical simulations. Results. A wide range of pattern speeds are inferred by the TW method, owing to a strong dependency on the orientation of the galaxy frame and the viewing angle of the bar perturbation. The simulated bar pattern speeds (corotation radii, respectively) are well recovered by the Dehnen method (BV model). Applied to the LMC data, the Dehnen method finds a pattern speed of Ωp = −1.0 ± 0.5 km s−1 kpc−1, thus corresponding to a bar that barely rotates and is only slightly counter-rotating with respect to the LMC disc. The BV method gives a LMC bar corotation radius of Rc = 4.20 ± 0.25 kpc, corresponding to a pattern speed of Ωp = 18.5−1.1+1.2 km s−1 kpc−1. Conclusions. It is not possible to determine which global value best represents an LMC bar pattern speed with the TW method, due to the strong variation with the orientation of the reference frame. The non-rotating bar from the Dehnen method would be at odds with the structure and kinematics of the LMC disc. The BV method result is consistent with previous estimates and gives a bar corotation-to-length ratio of 1.8 ± 0.1, suggesting that the LMC is hosting a slow bar.

Seismic behavior of BFRP bar reinforced shear walls strengthened with ultra-high-performance concrete boundary elements

Reducing the amount of steel reinforcement in construction is imperative, driven by the objectives of reducing carbon emissions and mitigating steel corrosion. Among the various alternatives to steel reinforcement, basalt fiber reinforced polymer bar (BFRP) is considered a promising solution. The aim of this study is to examine the seismic performance of shear walls entirely reinforced with BFRP bars, utilizing BFRP for both longitudinal and transverse reinforcement. To address the inherent limitations of BFRP bars, a novel composite shear wall, incorporating BFRP bars, ultra-high-performance concrete (UHPC) and normal strength concrete, is proposed. Specifically, UHPC boundary elements are employed to strengthen the potential compression zone of BFRP reinforced shear walls. Four shear wall specimens, fully reinforced with BFRP bars, were fabricated and tested for their seismic performance, with two specimens incorporating UHPC boundary elements. Comprehensive test results, including failure modes, load-bearing capacity, ductility, energy dissipation, stiffness degradation and rebar strain, are presented and discussed. A detailed discussion of the effects of axial load ratio (ALR) and UHPC boundary elements is included. The test results indicate that the specimens featuring UHPC boundary elements showed significant improvements in deformability, lateral strength and energy dissipation capacity. This reveals that the integration of UHPC boundary elements considerably enhances the seismic performance of BFRP bar reinforced shear walls. Moreover, although all test specimens experienced failure due to concrete crushing in the compression zone, those with UHPC boundary elements manifested higher tensile strain on the BFRP bars on the tension side, facilitating more effective utilization of the high tensile strength of the BFRP bars. Ultimately, a method to ascertain the flexural capacity of BFRP bar reinforced shear walls, both with and without UHPC boundary elements, is proposed and validated by the test results.

Experimental study of corrosion effects on pulling force of hook bars in external beam-column connections

The external beam-column connection in concrete structures is particularly important because it is necessary to secure the reinforcement bars of the beam that are embedded within the column, which are often formed as a 90° hook. The attack of chloride ions is also one of the most dangerous damages that affect constructions and reduce their service life. Hence, it was necessary to study the effect of corrosion resulting from chloride ion attack on the strength of hook bars. To achieve this purpose, 26 specimens were designed with various variables, including the corrosion level of the reinforcement bars, compressive strength of the concrete, specimen loading, and the spacing between the stirrups relative to their diameter (S/D). The specimens were subjected to accelerated corrosion in the laboratory using the current density method by applying 0.35 mA/cm2 for 21 and 58 days. The experimental results showed that corrosion of the reinforcing bar in the joint weakens the mechanical behavior of rebars by reducing their strength and the bond between them and the concrete. The effect of the compressive strength of the concrete, specimen loading, and S\\D on the hook pulling force for corroded and non-corroded specimens has been observed, and they also affected the determination of the level of corrosion. Equations have been proposed to develop Faraday's law and determine the pulling force of a hook bar. The proposed equations yielded results that closely matched those from the experimental test.

Effect of silica fume on Pullout capacity and corrosion resistance of hook bars in the external beam-column concrete joint

Purpose This study aims to determine the effect of replacing a portion of the cement in the concrete mixture with silica fume (SF) on the corrosion resistance of reinforcing bars, the compressive strength of concrete and the tensile strength of hook bars in both corroded and non-corroded external joints of structures. The external beam-column connection was studied because of its critical role in maintaining structural continuity in all three directions and providing resistance to rotation. Design/methodology/approach In external concrete joints, the bars at the end of the beams are often bent at 90° to form hooks that embed in columns. Owing to the importance of embedding distance and the need to understand its susceptibility to corrosion damage from chloride attack, a series of experiments were conducted on 12 specimens that accurately simulate real-site conditions in terms of dimensions, reinforcement and hook bars. SF was replaced with 10% and 15% of the weight of cement in the concrete mixture. To simulate corrosion, the specimens were subjected to accelerated corrosion in the laboratory by applying a low continuous current of 0.35 mA for 58 days. Findings The results revealed the effect of SF in improving the compressive strength of concrete, the pullout resistance of the hook bars and the corrosion resistance. In addition, it showed an apparent effect of the corrosion of reinforcing bars in reducing the bonding strength of hook bars with concrete and the effect of SF in improving this strength. Originality/value It was noted that the improvement of the results, achieved by replacing 10% of the weight of cement with SF, was significantly close to the results obtained by replacing 15% of the SF. It is recommended that an SF ratio of 10% be adopted to achieve the greatest economic savings.

Assessment of bonding strength of steel bar in recycled aggregate concrete containing ground palm oil fuel ash

Assessment of bonding strength of steel bar in recycled aggregate concrete containing ground palm oil fuel ash

Estimation of the Bond Strength of Fiber-Reinforced Polymer Bars in Concrete Using Artificial Intelligence Systems

Fiber-reinforced polymer (FRP) bars have recently been introduced to the market as an alternative to steel for internal reinforcement for concrete construction exposed to situations that could cause corrosion. The bond behavior of FRP bars varies from that of steel bars, mostly due to variations in material properties and surface textures. Because of the unexpected nature of the crucial FRP–concrete interfacial (FCI) bond strength, the bond strength between FRP bars and concrete cannot be exactly determined. Numerous experimental investigations have been conducted with related empirical models established in an attempt to resolve this problem. These models were found to have a restricted capacity for generalization due to the small sample sizes of the experiments. Therefore, a more powerful numerical technique capable of processing large data sets with all possible parameters that may affect the relationship and considering the nonlinearity of data tendency is needed. In this study, the artificial neural networks technique and adaptive neuro-fuzzy inference system were utilized to predict the FRP–concrete bond behavior based on 238 data points collected from different studies in the literature. The performance of the ANN and ANFIS models in predicting the bonding strength was compared to other models published in the literature and codes. The results showed that the ANN and ANFIS models gave higher prediction performance than other models, with a slight advantage for the ANN model. For instance, the R-squared values of the proposed ANN and ANFIS were 0.94 and 0.92, respectively, for 20 data points that were not used to develop the ANN and ANFIS models. Based on the sensitivity analysis, the FRP diameter and compressive strength of concrete were found to be the most effective parameters on the bond strength in both the ANN and ANFIS models. In contrast, the bar position and surface texture had a lower importance index.

Effect of seawater on bond performance between BFRP bars and seawater sea-sand concrete

This paper investigates the bond behaviors of BFRP bars with seawater sea-sand concrete (SSC) under seawater conditions. Eighteen experimental cases were established by considering BFRP bar's surface, seawater temperature, and the duration of specimen exposure in seawater as study factors. The BPE and CMR analytical models were calibrated utilizing the test results. Additionally, the bond strength was predicted utilizing the guidelines proposed in FIB Bulletin (40), and the anchorage lengths of deep-ribbed and sand-coated BFRP bars were calibrated. The findings illustrated that all specimens experienced interlaminar shear failure of the bars after immersion in seawater. Although deep-ribbed BFRP bars exhibited the highest initial bond strength, they exhibited greater degradation in the seawater immersion environment. Following 120 days in a 40 °C seawater solution, the bond strength of deep-ribbed BFRP bars was 5.4%, 20.6% lower than that of shallow-ribbed and sand-coated BFRP bars, respectively. The correlation coefficients between the BPE and CMR models and the experimental data were mostly above 0.95. Predicted 50-year results showed that sand-coated BFRP bars would retain between 62.6% and 88.7% bond strength in various conditions. In moisture-saturated environments at different temperatures, it is recommended that the anchorage length for deep-ribbed BFRP bars should range from 32 to 51 times the bar diameter. For sand-coated BFRP bars, the recommended anchorage length is 20 times the bar diameter.

Comparative Investigation of the Tensile Strength of Steel Bars With and Without Couplers

Connection in reinforced concrete is unavoidable due to limited length of steel. As known the maximum length of steel 12 metres and used for beams, columns, plates, foundations, etc. Sometimes several buildings use long spans between column to column for architecture causes longer steel needs. If spans are more than 12 metres the steels should be connected by welding, coupler drates, and other parts of connection. Coupler drates one of the most popular connection and it is easy to make connection between steels in the reinforcement concrete. This research aims to determine the behaviour of steels when they were tensioned at testing machine either full steel bar and connected steel bar by coupler drates. The testing was conducted at the materials laboratory the references for testing are Indonesian standards for testing materials like SNI - 2052 - 2017, SNI - 8389 - 2017 and SNI - 07 - 0408 - 1989. The type of steel bars for testing are drate steels of diameters 25 mm and 32 mm and the type of test is tensioning test. The results of testing for normal steel bar of D- 25 mm is 619.3 MPa and D-32 mm is 636 MPa respectively and steel bar with coupler drates for D- 25 mm is 428 MPa and D-32 mm is 522.5 MPa respectively. It means tension strength of D-25 mm coupler drates decreases 30.88 % and tension strength of D-32 mm decreases 17.84 % as compared with steel bars.

Machine learning to estimate the bond strength of the corroded steel bar‐concrete

AbstractSteel bar corrosion is prone to serious degeneration of the bond strength (τBS) of reinforced concrete, which leads to structural failure. There are many factors affecting the τBS; thus, the assessment of the τBS of corroded steel bar‐concrete becomes very complicated. In this research, a τBS evolution database of 430 samples containing 14 important factors, such as concrete compressive strength, yield strength and corrosion rate of steel bar, was established. Six machine learning algorithms were employed for comparative study to achieve optimal prediction results. The results showed that random forest and extreme random trees models have the best performance with coefficient of determination (R2) of 0.83 and 0.82, mean square error (MSE) of 13.59 and 13.98, root mean square error of 3.68 and 3.74, mean absolute error values of 2.35 and 2.31, and a20 values of 0.62 and 0.70, respectively. In addition, both models demonstrated shorter training times compared to the others. The running times are 589.75 and 418.31 ms, respectively. The superior feasibility and reliability of the machine learning algorithm were validated by contrasting with the computation of the empirical formulas. The empirical formulas exhibited higher error values, with the majority of MSE indicators exceeding 50 and the lowest R2 value even presenting negative values. Furthermore, feature importance calculations were used to understand the ability of the machine learning models to perceive each influencing factor. Among them, the corrosion rate, the yield strength of the longitudinal bar, and the stirrup emerged as the three most important influential factors.

Experimental study on bond performance between carbon/glass-hybrid-fiber-reinforced polymer bars and concrete

Coating GFRP bars with a layer of carbon fibers containing carbon/glass-hybrid-fiber-reinforced polymer (HFRP) bars has been proven to improved interlaminar shear durability. Thus, the bond performance of the HFRP bar-concrete interface depends on the behavior of the HFRP-reinforced concrete structure. In this context, the study investigates the effects of the compressive strength of concrete and the embedded length of HFRP bars on the bond behavior of the HFRP bar-concrete interface and compares the results with the data on the interfacial bond of GFRP bar to concrete. The results demonstrate that all the specimens fail at the FRP bar–concrete interface under the pullout. The bond strength and bond stiffness of the HFRP bar–concrete composites decrease with an increase in the embedded length of the HFRP bar from 4 to 10 times its diameter. Raising the compressive strength of the concrete enlarges the bond strength and bond stiffness of the HFRP bar–concrete composites. Furthermore, the outer layer of carbon-fiber on the GFRP bar decreases the impact of the embedded length of the HFRP bar on the bond strength and bond stiffness of the HFRP bar–concrete composites. Finally, the improved modified mBPE model can accurately predict the bond stress–slip relationship of GFRP/BFRP/HFRP bar–concrete composites.

Bond Strength of Steel Bars in Sustainable Concrete Made with Recycled Aggregates

Lately, considerable efforts have been directed towards investigating the practicality of using coarse recycled concrete aggregate as a potential substitute for natural coarse aggregate (NCA) in concrete construction. Research has shown that both the proportion of replacement and the properties of recycled aggregates play a significant role in affecting the tensile strength, compressive strength, and bonding characteristics of concrete. In certain cases, recycled aggregate concrete exhibits lesser mechanical properties when compared to concrete made with normal aggregates. The current study investigated the performance of Sika AnchorFix-1 to enhance the bond strength between steel bars and recycled aggregate concrete. The findings suggest that Sika AnchorFix-1 successfully prevented the concrete rupture in the case of concrete with recycled concrete aggregates, whereas concrete rupture could not be prevented in the case of concrete with recycled brick aggregates. Hence, a lower bond strength was obtained for specimens with recycled bricks aggregates than specimens with recycled concrete aggregates.