Basalt Fiber Reinforced Polymer Bars Research Articles

Analytical truss model for concrete beams reinforced with FRP bars

A truss model supplementing the concrete contribution is introduced in this paper to predict the shear strength of concrete beams reinforced with various types of FRP bars. The contributions from truss and direct strut mechanisms are considered in the analytical model. The truss model which has struts at various angles considering concrete contribution is derived in this paper. The concept of equivalent transverse FRP reinforcement is applied to integrate the concrete contribution into the proposed truss model. The shear strengths of concrete and FRP transverse reinforcements in the proposed model are calculated based on El-sayed et al. and CSA S806, respectively. The validity and applicability of the proposed model are evaluated by comparison with available experimental database, which consists of concrete beams reinforced with glass, carbon, aramid and basalt FRP bars. The comparison has shown a good correlation between the experimental data and analytical results. The proposed model is also compared with ACI 440.1R and CSA S806’s shear strength models and the better correlation is found. The results from this research shows that the properly-treated truss analogy can be used to assess the shear strength of concrete beams reinforced with various types of FRP bars.

Behavior of large-scale columns strengthened with basalt fiber-reinforced polymers sheets or bars and hybrid FRPs

Basalt fiber-reinforced polymers (BFRP) have recently become a widely used material for increasing the ultimate load capacity of reinforced concrete (RC) columns and improving their behavior throughout their entire life. So, an experimental program consisting of 19 large-scale RC columns of low strength has been prepared to examine the behavior of strengthened RC columns at all stages of loading. In this program, the columns were divided into two groups. The main parameters include the strengthening materials (BFRP wrap, BFRP bars, and carbon fiber reinforced polymers (CFRP) wrap), the strengthening techniques (fully or partially wrapping, the number and direction of layers), the cross-sectional shapes (square, rectangular, and circular), and the loading types (eccentric and concentric). The confinement of BFRP wraps significantly improved the service load and the ultimate failure load. The hybrid systems achieved an adequate level of confinement of the strengthened columns, increased the maximum load by 43.61 %, and absorbed energy by 477.2 % compared to the control column. BFRP bars used as a near-surface mounted material improved the behavior of the columns by up to 60 % and 411 % in maximum load and absorbed energy, respectively. The ACI and ECP codes predicted good estimates for the stress of columns strengthened with a single layer but underestimated for columns strengthened with a single layer and BFRP bars. Based upon the existing test data, BFRP-RC is recommended. Furthermore, this research can support using BFRPs as strengthening materials.

Flexural Behavior and Serviceability Performance of Lightweight Self-Consolidating Concrete Beams Reinforced with Basalt Fiber-Reinforced Polymer Bars

Flexural Behavior and Serviceability Performance of Lightweight Self-Consolidating Concrete Beams Reinforced with Basalt Fiber-Reinforced Polymer Bars

Design method for bridge deck link slabs prepared using BFRP bar‐reinforced ecological high‐ductility cementitious composites by theoretical calculation and numerical simulation

AbstractBridge deck link slabs prepared using Basalt Fiber Reinforced Polymer (BFRP) bar‐reinforced ecological high‐ductility cementitious composites (Eco‐HDCC) were applied as substitutes for steel expansion joints in Malin Bridge. Theoretical calculations and numerical simulations were combined to develop a design method. The total length and debond length of the link slabs were assumed based on the bridge information, and the reinforcement ratio of the BFRP bar was calculated using the maximum crack width limit. Then, the flexural capacity of the link slabs was evaluated. A preliminary reinforcement program using eight reinforcement ratios and different bar diameters was developed. In addition, the maximum stresses, strains, and deflections of the link slabs were validated through Abaqus finite element analysis. The simulation results of the reinforcement programs with minor reinforcement ratios are similar. The maximum stresses, strains, and deflections of the link slab materials are significantly lower than the design ultimate capacities of the materials, implying that the eight reinforcement programs are feasible. Because the thickness of the link slabs is within the range of 80–120 mm, a small‐diameter bar is preferable. Furthermore, BFRP bars with diameters of 10–14 mm are suitable along the driving direction, whereas BFRP bars with diameters of 10 mm are recommended along the direction perpendicular to the driving direction. A detailed design method flowchart for bridge deck link slabs was constructed to serve as a guideline for engineers.

Bond durability between BFRP bars and seawater coral aggregate concrete under seawater corrosion environments

The combination of fiber-reinforced polymer (FRP) composites with seawater coral aggregate concrete (CAC) in offshore construction contributes to reduced construction costs and avoids the corrosion problems related to steel-reinforced concrete structures. However, the durability for FRP-reinforced CAC members during service in marine environments is not well understood, which greatly hinders their application in offshore construction. In this paper, accelerated aging tests were employed for investigating the bond performance between the basalt-FRP (BFRP) bars and the CAC under seawater drying-wetting cycle and immersion environments. The effects of various exposure temperatures and exposure times on bond characteristics were considered, and scanning electron microscopy (SEM) was adopted to characterize microstructure changes at the cross-section of BFRP bars subjected to seawater exposure environments. The experimental results revealed that after being exposed to seawater corrosion conditions, the slope in the rising stage of the curves (i.e., initial bond stiffness) appeared to increase somewhat due to the hygroscopic expansion effect of the FRP bars, but the bond strength and its corresponding slip value demonstrated a gradual decrease. After being subjected to seawater drying-wetting cycle conditions at 45 °C and 60 °C for 12 months, the bond strength of BFRP bars in CAC declined by approximately 6.5 % and 12.0 %, respectively. This deterioration in the bond strength was related to the degradations in the mechanical properties of the FRP bars and the CAC, as well as the interfacial performance between the FRP bars and the CAC.

Flexural Behavior of Concrete Box Girders Reinforced with Mixed Steel and Basalt Fiber-Reinforced Polymer Bars

Flexural Behavior of Concrete Box Girders Reinforced with Mixed Steel and Basalt Fiber-Reinforced Polymer Bars

An Experimental and Numerical Analysis of Glued Laminated Beams Strengthened by Pre-Stressed Basalt Fibre-Reinforced Polymer Bars

Damage often develops in glued laminated timber members under high bending loads due to natural defects in the timber, which results in their low load-bearing capacity and stiffness. In order to improve the bending mechanical properties of glulam beams, a new type of longitudinal glulam reinforcement with pre-stressed basalt fibre-reinforced polymer composites (BFRP) was developed using the Near Surface Mounted (NSM) technique. The strengthening method consisted of two pre-stressed BFRP bars glued into the grooves at the bottom side of the beam; meanwhile, for the second strengthening alternative, the third BFRP bar was embedded into the groove at the top side of the beam. Therefore, an experimental study was carried out to verify this strengthening technique, in which fifteen full-size timber beams were tested with and without bonded BFRP bar reinforcement in three series. According to the results of this experimental study, it can be seen that the effective load-bearing capacity of the reinforced beams increased up to 36% and that the stiffness of the beams increased by 23% compared to the unreinforced beams. The tensile stresses in the wooden fibres were reduced by 11.32% and 25.42% on average for the beams reinforced with two and three BFRP bars, respectively. On the other hand, the compressive stresses were reduced by 16.53% and 32.10% compared to the unreinforced beams. The usual failure mode saw the cracking of the wood fibres at the defects, while for some specimens, there were also signs of cracks in the epoxy adhesive bond; however, the crack propagation was, overall, significantly reduced. The numerical calculations also show a good correlation with the experimental results. The difference in the results between the experimental and numerical analysis of the reinforced and unreinforced full-sized beams ranged between 3.63% and 11.45%.

Bond Performance of Anti-Corrosion Bar Embedded in Ceramsite Concrete in Freeze–Thaw Cycles and Corrosive Environments

At present, basalt fiber-reinforced polymer (BFRP) bars and epoxy-coated steel reinforcing bars (ECRs) are very promising in ocean engineering. In this study, the bond strength degradation characteristics of BFRP bars, ECR, and ordinary steel bars (OSBs) embedded in ceramsite concrete (CC) were compared in a single-corrosive environment (acid, salt, and alkaline salt, respectively) coupled with freeze–thaw (FT) cycles (0, 15, or 30); a total of 111 specimens were designed. In the three corrosive environments, the BFRP-bar-CC specimens and OSB-CC specimens all failed to pull out, while the ECR-CC specimens showed splitting failure. When corrosive and FT cycles acted together, the failure modes of BFRP-bar-CC specimens and ECR-CC specimens did not change. However, when the FT cycles increased from 15 to 30, the type of failure for the OSB-CC specimens changed from pullout failure to splitting failure. In addition, the bonding strength of the three kinds of bars decayed most rapidly in an acid environment. When 30 FT cycles were applied, the bond strength of ECR-CC specimens and OSB-CC specimens decreased most rapidly in the acid environment, by 9.12% and 18.62%, respectively. However, the bond strength of BFRP-bar-CC decreased most rapidly, by 17.2%, in an alkaline salt environment.

Bond behavior of recycled tyre steel fiber reinforced concrete and basalt fiber-reinforced polymer bars under static and fatigue loading conditions

Nowadays, there is a growing demand for the development of structures and construction materials from recycled or reused and renewable resources, in line with circular economy principles and the goal of sustainable development. The present study explores promising solutions for increasing the sustainability of concrete structures, through the application of basalt fibers reinforced polymer (BFRP) rebars, whose raw materials show an unlimited availability on earth, as well as recycled steel fibers from waste tyres (RTSF), for RTSF reinforced concrete structures with BFRP reinforcements. Three different types of self-compacting concretes with 1.1% fiber volume fractions of industrial and/or recycled steel fibers were developed, where 50% and 100% of the industrial steel fibers (ISF) weight was replaced by RTSF. Five different groups of pull-out specimens, with total number of 26 specimens, were fabricated to evaluate bond performance of BFRP rebar embedded in RTSF reinforced concrete. The understanding of the bond behaviour is critical to the effective design of reinforced concrete structures under both static and dynamic loadings. The influence of the type of reinforcement, dosage of the adopted RTSF, type of loading, and concrete flow direction on bond stress versus slip behavior, maximum bond stress, and failure mode are analysed and discussed. One of the main contributions of this research regards the understanding of the effect of RTSF orientation on bond performance obtained when BFRP rebars are pulled out from RTSF reinforced concrete. Compared to ISF, using RTSF for reinforcing concrete can increase the bond strength between BFRP rebars and fiber reinforced concrete up to 6.3% under static and 9.7% under fatigue loading regime. As the future research in this area, it is recommended to evaluate the long-term bond durability of BFRP reinforced FRC embedded in seawater, the environmental and economic feasibility of using BFRP and TRSF for reinforcing concrete structures, and fiber orientation and dispersion using image analysis and 3D visualization.

Experimental study on the mechanical properties and failure modes of BFRP bar anchor systems under static tension loading

Basalt fiber-reinforced polymer bars are lightweight composite materials with high strength, low density, and excellent corrosion resistance. The anchor system made from basalt fiber-reinforced polymer bars is worthy of being developed and expected to be used in rock anchoring projects. In this work, four different basalt fiber-reinforced polymer anchor systems were designed, the influences of different design parameters on the ultimate bearing capacity of the anchor system were investigated through tension tests, and the failure modes of different anchor systems were elucidated. The test results indicated that failure modes, such as the transverse fracture of these bars and debonding of the bonding medium, were widely present in the wedge-modified anchor system and the steel-pipe-protected anchor system. These two anchor systems performed poorly with the wedge anchorage, whereas the basalt fiber-reinforced polymer bars protected by seamless steel pipes burst under the tension imposed by a universal testing machine. The threaded steel-pipe-bonded anchor system and the steel strand–basalt fiber-reinforced polymer bar composite anchor system had maximum anchorage efficiency coefficients of 97.7% and 98.5%, respectively. The bars in the corresponding test groups all exhibited burst failure, indicating that these two anchoring structures achieved effective anchorage of the basalt fiber-reinforced polymer bars.

Pullout behaviors of basalt fiber-reinforced polymer bars with mechanical anchorages for concrete structures exposed to seawater

This study presents an investigation of the pullout behaviors of basalt fiber-reinforced polymer (BFRP) bars with mechanical anchorages in concrete exposed to seawater. A total of forty-eight pullout specimens were prepared. Three types of mechanical anchorages that can be flexibly assembled on FRP bars, that is, additional straight bar, additional hook, and composite head, were adopted. The experimental variables comprised the anchorage type, conditioning temperature, and conditioning duration. The maximum pullout load (Pmax) and corresponding slip (smax), and the plateau length at the peak (lp) and slope of the descending branch (kd) of the load-slip curves, were evaluated and discussed. The results show that mechanical anchorages contribute to significant increases in the lp and decreases in the kd. Furthermore, the composite head achieves 32 % and 10 % increases in Pmax and lp respectively, and 20 % and 36 % decreases in smax and kd respectively, compared with the other two types of anchorages. After conditioning in seawater, the specimens with composite heads exhibit no significant degradation in their pullout behaviors, which indicates the effectiveness of the composite head in the protection against corrosive media. These results demonstrate the application prospects of a composite-head mechanical anchorage for FRP reinforcement in concrete structures constructed in the marine environment.

A comparative study of bare and seawater sea sand concrete wrapped basalt fiber-reinforced polymer bars exposed to laboratory and real marine environments

The high alkalinity of concrete restricts the application of basalt fiber-reinforced polymer (BFRP) bars as reinforcement in seawater and sea sand concrete (SWSSC), but lowering the alkalinity enhances the durability of BFRP bars. This work focuses on the degradation of BFRP bars embedded in SWSSC in the laboratory and real marine environments. The interlaminar shear strength (ILSS) and deterioration mechanisms of BFRP bars wrapped in ordinary and low-alkalinity SWSSCs were investigated using the ILSS test, 1H nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). It was found that the BFRP bars in the natural marine environment suffer from less degradation than those in the accelerated laboratory environment due to the lower temperature. After 180 d of exposure to 55 °C seawater and the field environment, the ILSS retentions of BFRP bars in ordinary SWSSC are 54% and 85%, while those in low-alkalinity SWSSC remain 81% and 97%, respectively. The decreased alkalinity and porosity in low-alkalinity SWSSC also considerably minimize the hydrolysis of epoxy resin in BFRP bars caused by alkaline and moisture erosion. Furthermore, the Arrhenius theory-based model considering temperature and humidity fluctuations, predicts that lowering the alkalinity of SWSSC can greatly enhance the service life of BFRP bars, which can be applied in high-temperature and humidity environments. This study provides insights into using low-alkalinity SWSSC to improve the durability of FRP bars in marine concrete structures.

Effectiveness of reinforcing methods in enhancing the lateral impact performance of geopolymer concrete column reinforced with BFRP bars

To achieve more sustainable and durable structures, geopolymer concrete (GPC) structures reinforced with non-corrosive basalt fiber-reinforced polymer (BFRP) bars have been proposed to replace conventional steel reinforced ordinary Portland cement concrete (OPC) structures. The performances of GPC structures reinforced with BFRP bars under static loading conditions have been studied and engineering structures might be subjected to impact loading during their service life, which can cause severe damage to the structures. Therefore, it is important to also investigate the impact-resistant performance of structures. The impact-resistant response of BFRP-GPC columns under lateral impact loading has been recently investigated, and different response characteristics were observed from those of steel-OPC columns due to the different material properties. To enhance the impact resistance capacity, this study investigates the effectiveness of various reinforcing methods of BFRP-GPC columns. One BFRP-GPC column from our previous study was used as the reference column, and four BFRP-GPC columns were cast and tested by using a pendulum impact testing rig in this study. The four columns were respectively reinforced or strengthened with four different methods (i.e., increasing the longitudinal reinforcement ratio to enhance the flexural strength of the column, increasing the stirrup ratio to enhance the shear strength of the column, adding steel fibers to increase the tensile strength of GPC material, and wrapping the column with BFRP sheet). The columns under lateral impact loading were compared and analysed with respect to the failure mode, failure progress, impact force, and midheight deflection. It was found that increasing the longitudinal reinforcement ratio and using the external BFRP sheet wrapping led to better improvement in the impact resistance of the column. In addition, numerical simulations were carried out to investigate the response mechanism of the BFRP-GPC column, and a simplified model was proposed to predict the maximum shear force distribution of the column under impact for design analysis.

Bond performance between BFRP bars and alkali-activated seawater coral aggregate concrete

Alkali-activated materials (AAMs) or geopolymers as substitutes for ordinary Portland cement (OPC) contributed to reduced greenhouse-gas emissions and energy consumption. This paper examines the applicability of employing well-durable AAMs instead of OPCs to develop alkali-activated seawater coral aggregate concrete (AACAC) and explores their bond characteristics with basalt fiber-reinforced polymer (BFRP) bars. The effects of the rib height (0.2 and 0.6 mm), bond length (50, 70, and 100 mm), and stirrup constraints on the bond performance between the BFRP bars and AACAC were considered, and cement-based CAC was also selected as the reference group. Furthermore, a scanning electron microscopy (SEM) was applied to observe the interfacial microstructures between the slurry matrix and the aggregate. The tested results indicated that the utilization of AAMs can improve interfacial microstructures, thus resulting in a higher elastic modulus and splitting tensile strength of AACAC than CAC. Increasing the rib height of the bars and stirrup constraints can effectively enhance the bond strength and bond stiffness. Compared with the specimens with a rib height of 0.2 mm, the bond strengths of AACAC and CAC specimens with a rib height of 0.6 mm increased by about 8 % and 7 %, respectively. Nevertheless, the bond strength and bond stiffness of the specimens gradually decreased with increasing bond length due to the non-uniform distribution in bond stress along with the embedment length. In addition, compared to the cement-based CAC specimens, AACAC specimens possessed greater bond strength, bond stiffness, and residual bond stress. There were approximately 6 % and 15 % improvements in the bond strength for AACAC specimens with rib heights of 0.2 mm and 0.6 mm, respectively, and their bond stiffness at a slip value of 0.02 mm increased by about 38 % and 39 %, respectively, compared to the CAC specimens.

Meso-scale modelling of size effect on shear behavior of Basalt fiber reinforced concrete deep beams

The work aims to examine the size effect on shear failure of deep concrete beams with Basalt Fiber Reinforced Polymer (BFRP) bars. A mesoscale numerical model for the deep concrete beam with BFRP bars was built to explicitly model the shear failure, considering concrete heterogeneity and concrete/bars interaction. The mesoscale simulation approach was firstly verified against the available test observations. It was then utilized to study the shear failure of geometrical-similar concrete deep beams having different structural sizes with BFRP bars and steel bars. The influence of beam depth, stirrup ratio and reinforcement type (i.e., steel bars and BFRP bars) on the shear failure and the corresponding size effect of concrete deep beams was explored. The simulation results indicate that: 1) the failure modes of concrete deep beams with BFRP bars and steel bars are basically similar, and they all exhibit noticeable size effect; 2) stirrups (i.e., steel bars and BFRP bars) can hinder the development of diagonal cracks within concrete, and thus weaken the size effect in shear strength; 3) the shear failure in beams with BFRP bars presents more substantial size effect than that of beams with steel bars; 4) the calculation models of shear capacity in the international codes do not apply to concrete deep beams with BFRP bars. Moreover, it is found that the size effect law developed previously can also be suitable for the shear failure of concrete deep beams with BFRP bars.

Experimental Study on the Flexural Ductility of BFRP Bar Concrete Beams With Bamboo Fiber and Steel Wire Mesh

In order to study the influence of bamboo fiber and steel wire mesh on the flexural ductility of Basalt Fiber Reinforced Polymer（BFRP）bars concrete beams, seven BFRP bars concrete beams reinforced with bamboo fiber and steel wire mesh were tested with the bamboo fiber length (0mm, 30mm, 45mm) and the steel wire mesh layout range (none, 1/2 maximum bending moment point layout, full beam segment layout) as variables. The flexural failure test of 7 basalt fiber reinforced concrete beams reinforced by bamboo fiber and steel wire mesh was carried out, and the initial crack load, crack development, ultimate load and deformation were detected. The effects of fiber length and layout range of wire mesh on the crack resistance and deformation resistance of specimens are analyzed by the test data. With the help of functional model, the equivalent yield points of the seven test beams were obtained, and the ductility coefficients of the specimens were calculated. The results show that the addition of bamboo fiber and steel wire mesh increases the cracking load of BFRP bars concrete beams by 12% ~ 68%, reduces the crack distribution spacing and length development speed, reduces the deformation of test beams under the same load, and increases the ductility coefficient by 1.58% ~ 31.75%.

Punching Shear Behavior of Fibrous High Strength Concrete Slabs Reinforced with BFRP Bars

Abstract This study offers test findings from research work conducted to investigate the punching shear behavior of fibrous high strength concrete flat slabs reinforced with Basalt fiber-reinforced polymer (BFRP) bars. Eleven two-way concrete slabs were tested until they failed under central concentrated force. BFRP bars were employed to reinforce ten of the eleven slabs for flexural reinforcement, while steel bars were used to reinforce one slab for comparison. Each slab measured 1000 × 1000 × 70 mm with a 60 × 60 mm steel column at the center of the slab. The flexural-reinforcement type, flexural-reinforcement ratio, and steel fibers content were the test parameters. According to the test findings, raising the BFRP reinforcement ratio improved the slabs’ punching shear capability and load-deflection response. In comparison to slabs with a lower reinforcing ratio, these slabs also showed fewer, narrower cracks. Steel fibers were added, which improved the failure mode from brittle, unexpected failure to ductile failure. The experimental findings are compared to a shear strength equation offered by several concrete design codes, including ACI 440.1R-15, CAN/CSA S806-12, and JSCE.

Short- and Long-Term Prestress Losses in Basalt FRP Prestressed Concrete Beams under Sustained Loading

The favorable mechanical properties of basalt fiber–reinforced polymer (BFRP) bars, such as their excellent strength-to-weight ratio, resistance to corrosion, lower environmental impact, and electromagnetic neutrality, make them attractive for internal reinforcement of concrete elements with specific service requirements. Prestressing has emerged as a possible method for limiting the deflections and cracking of BFRP-reinforced flexural RC elements. However, long-term behavior of such structural members has not yet been investigated extensively. Therefore, this paper aims to give information on long-term behavior and prestress losses of pretensioned BFRP-reinforced concrete beams based on the collected experimental data. The testing program includes long-term analysis of six BFRP concrete beams pretensioned to different prestress levels—namely, 20%, 30%, and 40% of the ultimate tensile capacity of the bars. The monitored testing stages included initial tensioning of the bars, casting and curing of concrete, transfer of prestressing force to the concrete, long-term unloaded phase after transfer, sustained-loading application, long-term sustained loading phase, unloading, and final destructive testing, conducted in a controlled indoor environment. During all phases of the testing, strain levels in the BFRP bars and deflections were continuously monitored. The results of continuous strain monitoring show that the average loss of strain over the period of initial 90 days of unloaded monitoring was 7% of the initial strain. During the following 6 months of monitoring under sustained loading, an additional 0.3% reduction was recorded on average. The loss was dependent on the initial strain.

Durability of BFRP bars and BFRP reinforced seawater sea-sand concrete beams immersed in water and simulated seawater

Seawater sea-sand concrete (SSC) members reinforced with fiber-reinforced polymer (FRP) have considerable development potential. However, an adverse effect of alkalinity in seawater sea-sand concrete on the long-term performance of FRP was found, and the durability of FRP reinforced SSC structures in seawater is always a significant concern. Thus, this study examined the durability of basalt-fiber-reinforced polymer (BFRP) bars reinforced SSC beams in simulated seawater and tap water. Tensile and four-point bending tests analyzed the tensile properties of the BFRP bars embedded in SSC and the flexural performance of the BFRP-reinforced SSC beams respectively. The tensile strength of the BFRP bars decreased with the immersion time and the environmental temperature. Further, the tensile strength of the BFRP bars declined more severely in tap water than in seawater. The failure of the BFRP-reinforced SSC beams changed from shear to flexural failure owing to the reduction of the balanced ratio of the BFRP-reinforced beams in seawater and tap water. Moreover, the ultimate load-carrying capacity of the BFRP-reinforced SSC beams decreased, and they showed brittle failure characteristics. Finally, the ultimate load-carrying capacity of the BFRP-reinforced beams was predicted as a function of the degradation of the tensile strength of the BFRP bars. The developed equation conservatively estimated the flexural-load-carrying capacity of the BFRP-reinforced beams in actual oceanic environments.

Experimental investigation of bond performance between BFRP and different strength recycled-aggregate concrete

In recent years, there has been a large number of studies on recycled-aggregate concrete as a potential solution to the problem of a scarcity natural resources. This study investigated the bonding performance of a new reinforcement material employed in medium and high-strength recycled aggregate concrete. The pull-out test was carried out by employing basalt fiber-reinforced polymer (BFRP) bars with different diameters (12, 14, and 20 mm) in medium and high-strength concrete with different ratios of recycled coarse aggregate replacement (0, 25, 50, 75, and 100%). Based on the concrete bond damage, the failure modes were identified, the corresponding bond mechanism was analyzed and the bond stress–slip characteristics were summarized. The effect of each parameter on the failure mode, bond strength, and the bond-slip curve between recycled-aggregate concrete and BFRP bars was evaluated. Results indicated that as the diameter of the BFRP bar increased, the failure mode was shifted, the uneven distribution of bond stress became more pronounced, and the bond strength showed a decreasing trend. Two distinct situations of medium to high-strength concrete with very different relative bond strengths at different replacement ratios were found. The relative bond strength of medium-strength concrete increased at first and then decreased with the increase of the replacement ratio of recycled coarse aggregate. A non-linear relationship between the bond strength of recycled concrete and its compressive strength was found. The two-stage model was proposed to describe the bonding behaviour more accurately between BFRP bar and medium to high-strength recycled aggregate concrete.