Basalt Fiber Reinforced Polymer Bars Research Articles

Preliminary Study on the Bending Behavior of Solid Timber Beams Reinforced with Basalt Fiber-Reinforced Polymer Bars

The purpose of this work is to test the effectiveness of strengthening timber structures by means of composite bars. This article presents the results of preliminary tests carried out on solid beams made of fir wood. The test specimens, which are classified as strength class C24, had dimensions of 7 × 17 × 330 cm. Beams were reinforced with 8 mm diameter basalt fiber-reinforced polymer (BFRP) bars. The bars were glued into grooved channels along the bottom surface. Epoxy resin was used as an adhesive. The strength tests were conducted in accordance with the requirements of EN 408+A1:2012. The four-point bending scheme was adopted. The tests were conducted in the following two series: unreinforced beams (A) and beams reinforced with composites (B). Five elements were tested in each series. The reinforcement resulted in an average increase in the bending moment value of 8.41%. The deflection value at failure increased by 19.77%. The work also includes an analysis of the failure mode and a ductility analysis. Further tests should be carried out using a higher reinforcement ratio. A higher reinforcement ratio should make the presented reinforcement configuration more effective.

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

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

An innovative strategy for improving ductility of seawater sea-sand engineered cementitious composites beam reinforced with GFRP bar

Seawater sea-sand engineered cementitious composites (SS-ECC) members with glass fiber reinforced polymer (GFRP) bars have inferior ductility due to the brittle nature of GFRP bars. In the current research, an enlarged head anchorage system (EHAS) was recommended to improve the ductility of GFRP bars reinforced SS-ECC beams. To explore the bond characteristics between SS-ECC and GFRP bars with EHAS, a total of 39 specimens were tested by pull-out loading. The influences of enlarged head shape, stirrup spacing and SS-ECC’s strength grade on the bond characteristics were experimentally investigated. GFRP longitudinal bars in specimens with EHAS presented rupture failure rather than anchorage failure. EHAS could effectively realize the slip hardening of GFRP bars in low strength SS-ECC, and ensure the reliable bond of GFRP bars in high strength SS-ECC. Additionally, the failure mechanism of specimens under pull-out loading was explored by finite element analysis (FEA). The pull-out resistance was mainly provided by EHAS in force transition stage and slip hardening stage. The influences of fiber reinforced polymer (FRP) bar type on the bond performance were investigated by FEA. EHAS could realize the slip-hardening behaviors of aramid, basalt and carbon FRP bars in normal strength SS-ECC. More importantly, to verify the effectiveness of the proposed ductility enhancement strategy, SS-ECC beams reinforced with GFRP bars were tested by four-point bending. These beams with different enlarged head shapes possessed excellent ductility and strong ultimate deformation capacity. It was recommended that low strength SS-ECC and GFRP bars with EHAS were jointly utilized to enhance the ductile performance of the beams.

Evaluation of the long-term performance and durability of basalt fiber reinforced polymer bars in concrete structures

To simulate the internal corrosion process of basalt fiber reinforced polymer (BFRP) bars in an alkaline environment of concrete, a diffusion based model was employed and modified in this study according to Fickian diffusion and diffusion coefficients at 25 ℃, 40 ℃, and 55 ℃ obtained from existing studies. Thus, the long-term corrosion medium concentration diagram, degraded depth, and strength retention of BFRP bars in the concrete environment at any ambient temperature can be predicted. Durability tests of BFRP bars in an alkaline solution at 60 ℃ were conducted to verify that the diffusion based model’s predictions were accurate. Moreover, long-term bonding tests between BFRP bars and concrete were conducted. The results indicate that the predicted results of the degraded depth and strength degradation of BFRP bars corresponded well to the experimental data. Morphology analysis by scanning electron microscopy (SEM) indicates that the alkaline solution intrusion caused the resin matrix to deteriorate, the fibers and the resin to debond, and the reaction between OH- and SiO2 in the fibers to occur, which in turn caused the tensile and bonding strengths of FRP bars to degrade. Moreover, after 63 days of corrosion at 55 ℃, the degraded depth exceeded 7 times that of 25 ℃ and 2 times that of 40 ℃, which implies that the ambient temperature had an obvious influence on the deterioration of BFRPs. The degradation rate was extremely slow at room temperature and rapidly accelerated with the rise in temperature.

Flexural behavior of coral aggregate concrete beams reinforced with BFRP bars under seawater corrosion environments

The combined utilization of fiber-reinforced polymer (FRP) composites with coral aggregate concrete (CAC) in remote island areas contributes to the reduced construction cost and construction period, offering a promising application. However, the evolution pattern and deterioration mechanism of flexural behavior for FRP bars reinforced CAC beams in marine service environments remains unclear. Thus, this paper investigates the flexural behavior of basalt-FRP (BFRP) bars reinforced CAC beams under seawater immersion and dry-wet cycle conditions using laboratory-accelerated aging methods. The research considers the effects of exposure temperature and corrosion age on their failure modes, flexural stiffness, ultimate loading capacity, and deformation deflection. The experimental results revealed that with the increase in corrosion age and exposure temperature, the amount of vertical cracks of CAC beams decreased and their crack depth also exhibited a slight reduction, but their crack width and spacing at failure significantly increased. After being attacked by seawater environments, the load-deflection curves of CAC beams experienced an enhanced slope of the ascending section (i.e., flexural stiffness), but this strengthened flexural stiffness did not result in an enhancement in the ultimate load capacity. Instead, with prolonged corrosion and higher temperatures, the ultimate load of CAC beams displayed significant degradation, accompanied by reduced mid-span deflection. After 12 months of seawater exposure to wet-dry cycle conditions at 60 °C, the ultimate load and mid-span deflection of CAC beams degraded by approximately 25.0 % and 56.6 %, respectively. The study also predicted the flexural bearing capacity of CAC beams utilizing existing specifications for FRP-reinforced normal aggregate concrete (NAC). It was concluded that the formulae for flexural loading capacity for FRP-reinforced NAC beams were still suitable for CAC beams.

Data-driven predicting of bond strength in corroded BFRP concrete structures

The mechanical properties of basalt fiber-reinforced polymer (BFRP) concrete structures in corrosive environments are largely dependent on the bonding performance between the BFRP reinforcement and concrete. An accurate and convenient method for calculating the bonding strength is crucial for engineering design. However, experimental methods and existing empirical models are insufficient to encompass the intricate interdependencies among the bonding factors. This study proposed a machine learning (ML)-based bonding strength prediction method, which utilizes random forests (RF) and adaptive boosting (AdaBoost) algorithms to predict the interfacial bond strength of BFRP reinforcement in corroded concrete. The model was trained on a dataset of 355 samples, effectively quantifying the relationships between the BFRP reinforcement parameters, concrete parameters, corrosion factors, and bonding strength. The performance of the two algorithms was evaluated using R2, RMSE, and MAE indicators, and the prediction results were explained using the SHAP method. The results show that the predicted results of the machine learning model are highly consistent with the experimental results, with the AdaBoost model achieving an R2 of 0.925 on the test set, demonstrating high predictive performance. Among the various factors, the corrosion factor has the most significant impact on bonding strength, followed by concrete compressive strength and BFRP bar yield strength. Ultimately, the model was juxtaposed against traditional empirical formulas, affirming its efficacy and dependability. The research presents a novel approach to predicting bond strength in corroded BFRP bar-concrete systems.

A Study of the Shear Behavior of Concrete Beams with Synthetic Fibers Reinforced with Glass and Basalt Fiber-Reinforced Polymer Bars

A Study of the Shear Behavior of Concrete Beams with Synthetic Fibers Reinforced with Glass and Basalt Fiber-Reinforced Polymer Bars

Flexural behavior of BFRP bar–hybrid steel fiber reinforced UHPC beams

Ultra-high-performance concrete (UHPC) has the potential to overcome the durability limitations of conventional concrete. Basalt Fiber Reinforced Polymer (BFRP) bars can mitigate the corrosion effects of steel bars and fully exploit the properties of UHPC. Industrial Steel Fibers (ISF) are a widely used component in the preparation of UHPC. To reduce environmental pollution and costs, this study proposes using recycled tire steel fibers (RTSF) instead of ISF in the production of UHPC. RTSF will be combined with BFRP bars to prepare hybrid steel fiber UHPC beams. The study investigates the effects of RTSF substitution for ISF and BFRP reinforcement ratio on the flexural performance of UHPC beams. The study indicates that the beam's bending failure modes include concrete crushing, equilibrium, and BFRP bar tensile failure. The replacement rate of RTSF has a dual effect on the flexural performance. As the RTSF replacement rate increases from 0 % to 100 %, the cracking load and ultimate capacity of the beams decrease by 2.86 % and 10.38 %, respectively, while the mid-span deflection of the beam increases by 7.94 mm when it reaches failure. When the replacement rate of RTSF is 60 %, the beams exhibit optimal bending performance, and their ultimate capacity can be increased by 2.95 % compared to the capacity when the replacement rate is 0 %. The failure mode of the beams is significantly influenced by the reinforcement ratio of the BFRP bars. Increasing the BFRP reinforcement ratio from 1.12 % to 7.12 % resulted in a 65.8 % decrease in maximum crack width and a 57.6 % decrease in mid-span deflection, while the ultimate load is increased by 78.6 %. The proposed theoretical calculation formula can effectively predict the flexural capacity of BFRP bar hybrid steel fiber UHPC beams, providing a theoretical basis for the application of FRP reinforced hybrid steel fiber UHPC beams.

Study on the fire resistance of RC beams reinforced with BFRP and HFRP bars

For non-metallic reinforcement to be successfully integrated into residential and commercial construction, extensive research is required to understand the structural performance of Fiber Reinforced Polymer (FRP) reinforced concrete (RC) elements in various conditions, including the effect of elevated temperatures on structural performance. To accomplish this, a full-scale investigation was performed on the structural performance of FRP-RC elements subjected to elevated temperatures. The study involved conducting fire tests on beams, where the midsection was heated from below (tension zone) and the sides while being simultaneously loaded with 50% of their ultimate loads. The beams were reinforced with Basalt FRP (BFRP) bars and a hybrid composite of Carbon and Basalt Fibers (HFRP) bars. The HFRP-RC beams showed better resistance to the combined effect of loading and elevated temperatures compared to BFRP-RC beams. This study provides insights into the behavior of FRP materials in RC structures subjected to high temperatures, and contributes to the advancement of knowledge in this field.

Experimental and theoretical investigations on the flexural behavior of precast concrete slabs reinforced with prestressing BFRP bars and fibers

AbstractPrestressing basalt‐fiber‐reinforced polymer (BFRP) bars and three types of fibers were used to enhance precast slabs during construction. Experimental investigation was conducted on one control slab and three reinforced slabs, while equations for the flexural behavior of slabs and optimization were performed. The results demonstrated that the addition of fibers had minimal impact on the compressive strength of concrete, but significantly improved its flexural strengths by up to 36%. Fibers and BFRP bars with a prestress level of 40% enhanced the cracking load by a range of 506% to 584%, and the ultimate load by a range of 28% to 48%, while exerting minimal influence on the yield load. Reinforced slabs exhibited a reduction in yield deflection ranging from 57% to 67%, along with a decrease in ultimate deflection ranging from 33% to 42%. Prestress played a crucial role in controlling slab cracks, whereas fiber type had only minor effects. The equation derived for predicting experimental results regarding normal section cracking moment showed a maximum deviation not exceeding 5%. Material utilization can be improved by reducing slab thickness or the number of prestressing bars, followed by lowering prestress levels and truss numbers. Prioritizing reduction in slab thickness is recommended from a construction perspective.

Flexural durability of BFRP bars reinforced geopolymer-based coral aggregate concrete beams conditioned in marine environments

Geopolymer is an environmentally friendly material that utilizes industrial solid waste, boasting reduced greenhouse gas emissions and energy consumption. It exhibits superior performance in terms of corrosion resistance and thermal stability compared to ordinary Portland cement (OPC). These excellent properties are crucial for marine engineering construction, offering significant value and application potential in marine engineering materials. In this study, geopolymer was employed as the cementitious material, with marine resources like seawater and coral aggregates sourced from remote island areas effectively utilized, and basalt fiber-reinforced polymer (BFRP) bars were incorporated as reinforcements to develop BFRP bars reinforced geopolymer-based coral aggregate concrete (GPCAC) beams. Laboratory aging procedures were employed to investigate the deterioration patterns and damage mechanisms affecting the flexural behavior of GPCAC beams under seawater immersion and dry-wet cycling conditions, comparing them with cement-based coral aggregate concrete (CAC) beams. The experimental results indicated that both CAC and GPCAC beams under simulated marine environments experienced a reduction in the number of cracks upon damage, but their crack spacing and width increased. Moreover, the flexural stiffness of CAC and GPCAC beams after seawater attacks tended to increase, but this increased stiffness did not translate to a higher loading capacity. Conversely, as the corrosion age increased, the ultimate load and deflection values of both CAC and GPCAC beams decreased to varying extents, with the load-carrying capacity degradation more pronounced in seawater dry-wet cycling environments than in seawater immersion conditions. Compared to CAC beams, GPCAC beams exhibited superior resistance to seawater erosion. Following 12 months of seawater dry-wet cycling, the ultimate loading capacity of CAC beams decreased by 12.2%, while that of GPCAC beams only degraded by 9.5%. Predictions of the flexural capacity of GPCAC beams using equations from existing FRP-reinforced normal aggregate concrete (NAC) specifications indicated slightly higher values than the experimental values, with an error margin of less than 15%. Overall, the formulas for the flexural capacity of NAC beams in existing FRP-reinforced NAC codes remained applicable to CAC and GPCAC beams.

Static and fatigue behavior of concrete bridge deck slabs reinforced with BFRP and steel bars

Using Fiber-reinforced polymer (FRP) has proved great promise as an alternative to conventional steel in bridge constructions owing to its high tensile strength and corrosion resistance. However, using Hybrid reinforced concrete (RC) slabs displayed enhanced stiffness, narrower crack width and larger bending capacity compared with FRP-RC slabs. This paper studies the static and fatigue performance of concrete bridge deck slabs reinforced with hybrid basalt-FRP (BFRP) and steel bars. The main parameters were the effective reinforcement ratio, the FRP-to-steel bars ratio Af/As, and the fatigue limit. The test results exhibited that superior fatigue behavior was achieved in the hybrid-RC slabs because the hybrid bars can better distribute the load and reduce stress concentration. In addition, the fatigue life growths with increasing the effective reinforcement ratio while reverse trend was observed when increasing Af/As ratio. In addition, increasing the upper fatigue load limit deteriorates the slab stiffness and significantly reduces the fatigue life. A regression analysis has been performed and revealed that the concrete deck slab can withstand 2 million cycles after fatigue loading of an upper fatigue load limit of 34 % of its ultimate static capacity.

Numerical Study of Shear Behavior of Geopolymer Concrete Beam Without Stirrups

Abstract The need to develop the concrete industry has increased with the increase in environmental damage resulting from building and construction operations. In the present research, the Numerical study of shear behavior of geopolymer concrete beams without stirrups by using the ANSYS program. It also includes concrete modelling to study the behavior of geopolymer concrete (GPC). The longitudinal reinforcements of beams (without stirrups) were "basalt fiber reinforced polymer bars". In order to enhance the shear behavior of the specimens, various types of fibers were added to geopolymer concrete (GPC): "steel fibers (SF), synthetic polypropylene fibers (PF), polyvinyl alcohol fibers (PVF), and carbon fibers (CF)". A numerical analysis was performed by the ANSYS version 15 program to study many parameters affecting the shear behavior of geopolymer concrete, such as longitudinal reinforcements,, and the inclusion of the opening. The results indicated that using steel fibers (SF) in geopolymer concrete increased the load failure of the tested specimens. On the other hand, using carbon fibers (CF) in the geopolymer concrete enhanced the ductility factor of these beams. The load capacity of the geopolymer concrete specimen is enhanced with longitudinal reinforcement by the CFRP bar compared to those reinforcements by BFRP bars. While the use of GFRP bars was less efficient than BFRP bars. Using FRP bars, and steel bars in strengthening geopolymer concrete beams with openings enhanced the failure load of these specimens.

Bond performance between ribbed BFRP bar and seawater sea-sand concrete: Influences of rib geometry

To solve the corrosion problems of steel bars in reinforced seawater sea-sand concrete (SSC) structures, fibre reinforced polymer (FRP) bars are promising alternatives. The bond between FRP bars and SSC determines the capacity and serviceability limit states of structures composed by them. The rib geometry of FRP bars is one of the most important factors influencing their bond performances with concrete. However, it has not received sufficient attentions on existing studies and standards. Therefore, this study investigated the bond performance between SSC and ribbed basalt FRP bars with different rib geometry through pull-out tests on 36 specimens. It is found that the bond strength declined with the increase of rib width and dent width, while the increase of rib height improved the bond strength. The ultimate and residual slip were strongly correlated with the rib spacing. Finally, a bond strength model that can well predict the experimental results was proposed.

Experimental Study on Flexural Behavior of RC Piles with Basalt Fiber-Reinforced Polymer Bars and Load Carrying Capacity Calculation

The practical application of BFRPB (Basalt Fiber-Reinforced Polymer Bars) as a support structure in foundation pit and slope engineering is relatively under-researched. The indoor tensile test presented in this paper is carried out on the bond between BFRPB and different labelled concrete. The mechanical characteristics of BFRPB, the failure characteristics, and the load-carrying capacity were analyzed. The results of this study demonstrate that the normal section stress of concrete cylindrical components with BFRP has a good linear relationship and supports the rationality of the flat section assumption. In circular reinforced concrete BFRP structures, the failure of the pile load occurs in four phases, and the cracking load is in the range of 51% to 67% of the normal yield load. The main bars increase in strain with load but become attenuated in the compression zone. The deformation of the main bars increases with the load but becomes muted in the compression zone. Based on the method of calculating the load-carrying capacity of GFRP-reinforced RC piles and the normal limit load-carrying moment obtained from in-door tests, the bending moment correction coefficient in the calculation formula for the load-carrying capacity of BFRP-reinforced RC piles was then obtained.

Multiscale analysis of the flexural performance of FRP reinforced concrete structures

Based on existing experimental data and analysis, seven different fiber-reinforced polymer (FRP) bar models including carbon fiber-reinforced polymer (CFRP), basalt fiber-reinforced polymer (BFRP), aramid fiber-reinforced polymer (AFRP), glass fiber-reinforced polymer (GFRP), GFRP and CFRP combined (G–C), GFRP and AFRP combined (G–A), BFRP and CFRP combined (B–C), and BFRP and AFRP combined (B–A) were established. Finite element simulation analysis was conducted on seven different FRP bar combinations under static load bending tests. The flexural behavior of the specimens reinforced with different FRP bar combinations and their influencing factors were analyzed. The results showed that using AFRP as the reinforcement material for FRP composite bars in FRP reinforced concrete beams cannot effectively enhance the overall load-carrying capacity of the composite bars. The combination of CFRP with GFRP and BFRP bars significantly increases the stiffness of the FRP bar structure and improves the structural load-carrying capacity of the concrete beams.

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.

A Comparative Study on Shear Size Effect of Steel-And BFRP-RC Shear Walls Under Cyclic Lateral Loads

ABSTRACT This paper presents a comparative study on the size effect behaviors of shear performances of concrete shear walls reinforced by steel bars and Basalt Fiber Reinforced Polymer (BFRP) bars. All the works are conducted through a two-dimensional meso-scale numerical simulation model representing the concrete shear wall. The horizontal reinforcement ratio and the sectional size are the main parameters concerned by the present study. Both the seismic behaviors under cyclic loading and the size effect behaviors of the shear performances were simulated and investigated. It can be concluded from the simulation results, (1) the use of steel bars or BFRP bars as horizontal reinforcement does not change the shear failure modes of concrete shear walls, (2) the size effect on the nominal shear strength of BFRP reinforced concrete (BFRP-RC) shear wall is more significant compared to that for steel-RC shear wall, (3) the increase of horizontal reinforcement ratio improves the shear capacity of the concrete shear wall, while weakens the size effect on the nominal shear strength, and (4) the size effect law for the nominal shear strength of steel-RC shear wall is applicable to BFRP-RC shear wall. Finally, the importance of considering size effect in the evaluation of shear performance of steel-/BFRP-RC shear wall is manifested by comparing the predictive results of several popular design codes with the simulation results.

Bond behavior of the interface between concrete and basalt fiber reinforced polymer bar after freeze-thaw cycles

Bond behavior of the interface between concrete and basalt fiber reinforced polymer bar after freeze-thaw cycles

Experimental and numerical study of the flexural behaviour of semi-precast slab reinforced with prestressed FRP bars

The performance of semi-precast slabs with prestressed basalt fibre-reinforced polymer (BFRP) bars under load is explored in this paper, using both experiments and computer simulations. The semi-precast slabs consist of precast concrete panels and cast-in-situ layers. The Precast panels are reinforced with BFRP bars prestressed at varying levels from 0% to 50% of their ultimate tensile strength. The experimental programme encompasses four-point bending tests conducted on five semi-precast slabs. For the numerical study, an ABAQUS model was used to perform finite element (FE) analysis, which aimed to simulate how the semi-precast slabs bent and to study how different factors affected their bending performance. The study parameters in this study were the grade of concrete and the reinforcement ratio. The results of this study show that prestressed BFRP bars significantly enhance load capacity and stiffness, while steel offers superior ductility. The computer models and the experiments matched well, as the average error between the two sets of data was less than 10%. Additionally, the parametric study reveals that enhancing the concrete grade or the reinforcement ratio can effectively enhance the flexural capacity and stiffness of the semi-precast slabs. In conclusion, this paper advocates for the utilisation of prestressed BFRP bars as an efficient and long-lasting reinforcement solution for semi-precast concrete slabs.