Basalt Fiber Reinforced Polymer Bars Research Articles

Bond Behavior between BFRP Bars and Hybrid Fiber Recycled Aggregate Concrete after High Temperature

The aim of this study is to improve the bond performance of basalt fiber reinforced polymer (BFRP) bars and recycled aggregate concrete (RAC) after being exposed to high temperatures. The bond behavior (failure modes, bond st... | Find, read and cite all the research you need on Tech Science Press

Studies on stress-strain behaviour of concrete mixes confined with BFRP rebars

In the present study, the stress-stain behaviour of confined concrete made with basalt fibre reinforced polymer bars (BFRP) were taken up. The stress-strain behaviour was studied for the concrete mixes confined with steel rebars and BFRP rebars. The confinement was given in the form of steel hoops in the cylinders, 3 hoops (0.8%), 4 hoops (1.1%), 5 hoops (1.3%) and 6 hoops (1.6%). The addition of basalt fibres along with confinement of concrete with steel and BFRP hoops enhanced the compressive strength, indicating further confinement effect in the concrete. It is observed that the addition of fibres is helpful in lower confinements only. Beyond 1.1% confinement, the addition of any type of basalt fibres doesn’t show any effect on compressive strengths. From the stress-strain behaviour of all types of concrete mixes, it is concluded that the ultimate load-carrying capacity and strains at peak stresses are more in concrete with BFRP hoops for mixes up to 1.1% confinement. The addition of basalt fibres to concrete has increased the ductility in both confined and unconfined states

Tensile and Shear Testing of Basalt Fiber Reinforced Polymer (BFRP) and Hybrid Basalt/Carbon Fiber Reinforced Polymer (HFRP) Bars.

The use of sustainable materials is a challenging issue for the construction industry; thus, Fiber Reinforced Polymers (FRP) is of interest to civil and structural engineers for their lightweight and high-strength properties. The paper describes the results of tensile and shear strength testing of Basalt FRP (BFRP) and Hybrid FRP (HFRP) bars. The combination of carbon fibers and basalt fibers leads to a more cost-efficient alternative to Carbon FRP (CFRP) and a more sustainable alternative to BFRP. The bars were subjected to both tensile and shear strength testing in order to investigate their structural behavior and find a correlation between the results. The results of the tests done on BFRP and HFRP bars showed that the mechanical properties of BFRP bars were lower than for HFRP bars. The maximum tensile strength obtained for a BFRP bar with a diameter of 10 mm was equal to approximately 1150 MPa, whereas for HFRP bars with a diameter of 8 mm, it was higher, approximately 1280 MPa. Additionally, better results were obtained for HFRP bars during shear testing; the average maximum shear stress was equal to 214 MPa, which was approximately 22% higher than the average maximum shear stress obtained for BFRP bars. However, HFRP bars exhibited the lowest shear strain of 57% that of BFRP bars. This confirms the effectiveness of using HFRP bars as a replacement for less rigid BFRP bars. It is worth mentioning that after obtaining these results, shear testing can be performed instead of tensile testing for future studies, which is less complicated and takes less time to prepare than tensile testing.

Structural and sensing performance of RC beams strengthened with prestressed near-surface mounted self-sensing basalt FRP bar

It is meaningful to use a prestressed near-surface mounted (NSM) fibre-reinforced polymer (FRP) system to strengthen reinforced concrete (RC) beams. However, brittle failure of debonding or FRP breakage may occur. We propose new prestressed NSM self-sensing basalt FRP (BFRP) bar system to improve the situation from both structural and sensing aspects. A self-sensing BFRP bar is first introduced based on the distributed optical-fibre sensing technology. Then, four RC beams are NSM-strengthened with the proposed self-sensing BFRP bar of different prestress force levels, and tested under static loads. The experimental results prove that the ductile failure mode does not change for all specimens, and verify an obvious improvement in load capacity-positive correlation with the prestress force level. However, a larger prestress force will decrease the deformation capability of strengthened beams, and vice versa. Finally, the proposed method can evaluate the displacement, curvature and bending moment with fair accuracy.

Experimental study on the axial compression behavior of columns confined by BFRP ties

Few studies have investigated concrete columns reinforced with basalt fiber-reinforced polymer (BFRP) ties. Due to its cost effectiveness, manufacturability, and good corrosion resistance, BFRP should be considered for use in concrete columns. This study experimentally investigated the axial compression behavior of concrete columns longitudinally reinforced with steel bars and transversely reinforced with BFRP ties. The test variables included the tie type, spacing, diameter, and configuration, the longitudinal bar type and the concrete strength. The test results indicated that the steel ties were better than the BFRP ties in enhancing the concrete strength and ultimate load, whereas the BFRP ties improved the post-peak ductility. A smaller tie spacing effectively improved the strength and ductility, and a larger BFRP tie diameter was more beneficial for improving ductility than load capacity. The combination of outer and inner rectangular BFRP ties was best for ductility improvement. At the peak load, the BFRP bars carried far less load than the steel bars; however, the BFRP or hybrid bars provided better ductility. Increasing the concrete strength grade increased the load capacity and decreased the ductility of the column.

Experimental investigation on concrete beams reinforced with basalt fiber reinforced polymer bars

Abstract This paper dealt with the flexural behaviour study on reinforced concrete beams with conventional steel and basalt rebar using Portland Pozzolana Cement. Conventional steel bars are vulnerable to various environmental attacks and aggressive attacks such as corrosion. Basalt rebar can effectively overcome this problem due to the enhanced properties like inhibiting corrosion, high tensile strength, low young’s modulus, lightweight and resist electrical conductivity. In this paper, flexural behaviour of conventional Steel Reinforced Beam (SRB) and Basalt Fiber Reinforced Polymer beam (BFRB) were investigated experimentally and test results arrived were elaborately discussed. It has been noticed that BRB shows significant greater deflection when compared to SRB due to lower elastic modulus, whereas flexural load carrying capacity of BRB increases due to enriched tensile strength property in basalt rebar, significant increase of tensile strength in BRB. The results revealed that basalt rebar can be effectively used in construction as a replacement of conventional steel reinforcement for sustainable development.

Concrete protective arches reinforced with BFRP bars: Construction and quasi-static structural performances

To construct corrosion resistant protective underground arches in waterfront structural engineering, steel bars are replaced by basalt fiber reinforced polymer (BFRP) bars and hybrid BFRP-steel bars. Eight semi-circular arches reinforced with steel bars, BFRP bars and BFRP-steel bars were casted. Quasi-static compression experiments were performed to evaluate the structural performances of the arches, including the deformation types, the failure modes and the ultimate loading capacities. Although the composite bars are linear elasticity, the concrete arches reinforced with composite bars behave as elastic-plastic deformation. The arches have typical flexural failure mode when the failure is determined by the crushing of the compressed concrete. Meanwhile, some of them exhibit brittle failure when the vault of the arch is sheared to fracture. Compared with the steel bars reinforced arches (SBRAs), the BFRP bars reinforced arches (BBRAs) have comparable ductility and ultimate loading capacity. An analytical method of the structure, including the coupling effects of bending moment, axial force, and shear force, was proposed to predict the load capacity of the SBRAs and BBRAs. The results show that the new proposed analytical method can capture the experimental results with acceptable errors. According to the experiments and analytical results, the BBRAs with excellent corrosion resistance can be treated as a replacement of SBRAs in waterfront underground protective structures.

Flexural behaviour of ambient cured geopolymer concrete beams reinforced with BFRP bars under static and impact loads

The applications of GeoPolymer Concrete (GPC) with basalt-fiber-reinforced-polymer (BFRP) reinforcements could be alternative for conventional structural designs with Portland Cement Concrete reinforced with steel bars for green and sustainable constructions. Very limited studies, however, have been carried out to investigate the performance of GPC beams reinforced with BFRP bars subjected to static loads, and no study of their performance under impact load is available in open literature yet. In this study, ambient-cured GPC beams reinforced with BFRP bars were tested under static and impact loads. Their damage modes, static and dynamic responses were recorded and analysed. The test results showed that the beams experienced flexural failure mode under static load while combined flexure-shear failure mode was observed under impact load. The impact-loading tested beams were further statically loaded to examine their residual capacities. Additionally, numerical models of the tested GPC beams were developed adopting the commonly used concrete material model *Mat_072R3 (KCC model) in LS-DYNA with modified parameters based on the GPC material testing data. The calibrated numerical model was used for parametric simulations. The results showed that with the increased impact velocity, failure mode of the beam shifted from the flexure-governed to punching-shear-governed along with the rupture of longitudinal BFRP bars.

Experimental study on fatigue bond behaviour between basalt fibre-reinforced polymer bars and recycled aggregate concrete

The bond performance between fibre-reinforced polymer (FRP) bars and recycled aggregate concrete (RAC) affects their combined working ability and further influences the bearing capacity and deformation resistance of FRP bar-reinforced RAC structures. In addition to static loads, many structures such as roads, bridges and subways usually bear fatigue loads during their service periods. Therefore, to provide theoretical and experimental references to the fatigue bond design of FRP bar-reinforced RAC structures, this study systematically investigated the fatigue bond behaviour between basalt fibre-reinforced polymer (BFRP) bars and RAC. Pull-out tests were carried out considering the effects of the surface shapes of BFRP bars, bar diameters, concrete types, fatigue stress levels, and fatigue cycles. Based on the damage at the bond interface, the corresponding bond mechanism was analysed and the bond stress–slip characteristics were summarised. Furthermore, the effect of design parameters on the bond stiffness, slip, bond strength, and residual bond strength was revealed. Different surface shapes of BFRP bars induced different bond mechanisms. Moreover, fatigue loads mainly affected the bond behaviour by eliminating the imperfections and accumulating the damage.

Mechanical performance of FRP-RC flexural members subjected to fire conditions

One of the main concerns that limit the widespread use of Fibre-Reinforced Polymers (FRP) bars as internal reinforcement for reinforced concrete (RC) structures is their relatively unexplored response to elevated temperatures. The behaviour of FRP reinforcement at elevated temperature as well as their post-fire behaviour can be different from conventional reinforcement and depends on the properties of the constituents of the bars. Therefore, the fire resistance of FRP-RC structures is an important issue that needs careful investigation before FRP reinforcement can be implemented in RC structures.
 The experimental results for full-scale FRP-RC beams subjected to specific fire action were presented and discussed in this paper. The specimens were exposed to heat in the mid-section from below (tension zone) and from the sides. As one of the main aims was to examine the influence of different reinforcement configurations, the testing was made for concrete beams reinforced with three different types of FRP bars: (i) basalt-FRP (BFRP), (ii) hybrid FRP with carbon and basalt fibres (HFRP) and (iii) nano-hybrid FRP (nHFRP), with modification of the epoxy matrix of the rebars.
 The present work describes the behaviour of FRP-RC beams exposed to fire conditions and simultaneous loading (50 % of their ultimate strength capacity at normal temperature) and unloaded beams were tested after the cooling phase in order to evaluate their residual resistance.
 Present work shows that the type of FRP bars used has a direct influence on the outcomes and the way of destruction. The maximum ductility, the longest heating time of approximately 100 minutes, was obtained for beams reinforced with BFRP bars and attained deflections were corresponded to the value of 162 mm.

Transverse Crack Behavior in Continuously Reinforced Concrete Pavement with Basalt Fiber Reinforcement

Continuously reinforced concrete pavement (CRCP) is a pavement structure with a high performance and long service life. However, the corrosion of the longitudinal steel can result in a poor bond relationship between the steel and the concrete, affecting the load transfer efficiency between the adjacent panels and being responsible for the development of CRCP distresses. Basalt fiber-reinforced polymer (BFRP) is corrosion-resistant and has the potential to be used in CRCP. In this paper, the layout of a CRCP test section with BFRP bars constructed on G330 National Road in Zhejiang Province, China, is presented. An analytical model is proposed to predict the crack behavior of CRCP with BFRP reinforcement, with the predicted results are compared to field-measured ones. A sensitivity analysis of the BFRP design parameters on the crack spacing and crack width is conducted as well. The results show that the mean values for field-measured crack spacing and crack width are 4.85 m and 1.30 mm, respectively, which are higher than the results for traditional CRCP with steel due to the lower elastic modulus of BFRP. The analytical predictions agree reasonably well with the crack survey results. The higher the elastic modulus of BFRP, the reinforcement content (with both BFRP spacing and diameter related), and the bond stiffness coefficient between the BFRP and concrete, the less the crack spacing and crack width will be. Given the same or similar reinforcement content, a lower diameter with a smaller spacing is recommended because of its contribution to a smaller crack spacing and width.

Evaluation of FRP Bars under Compression and Their Performance in RC Columns.

The behavior of fiber-reinforced polymer (FRP) bars under compression is not fully understood yet due to the limited research in this area. However, the long-term durability, weathering resistance, and exceptional mechanical properties of FRP bars justify the need for their use in compression members. The main objectives of this study are to evaluate the mechanical properties of glass FRP (GFRP) and basalt FRP (BFRP) bars under compression and examine their performances as main longitudinal reinforcements in reinforced concrete (RC) columns. In the first part of this research, a series of static compression tests were conducted on GFRP and BFRP bars of different diameters. The second part of this research numerically investigated the behavior of FRP-RC columns under concentric and eccentric loading using the mechanical properties of the FRP bars obtained experimentally. Nonlinear finite element models were developed to simulate the compressive behavior of the concrete columns reinforced with GFRP and BFRP bars. The FE models were verified with the experimental results conducted previously. The verified FE models are then utilized to conduct a parametric analysis considering two different column geometries and cross-sections, five reinforcement ratios, two concrete compressive strengths, three types of ties materials, and several loading eccentricities to develop a set of interaction diagrams that may provide valuable data for design purposes. The results indicated that the FRP bars could have a significant contribution to the overall capacity of FRP-RC columns by up to 35% of the total force at failure, depending on the reinforcement ratio. The performance of both the GFRP- and BFRP-RC columns was almost similar in terms of capacity, deflection, and bar strength contribution.

Bond strength of FRP bars in recycled-aggregate concrete

This study presents an experimental program conducted to investigate the bond strength of FRP bars in recycled-aggregate concrete compared to the one in normal-aggregate concrete for better evaluation of the results. The experimental program contains thirty six specimens that are tested using the direct pull-out test. In this study, glass, carbon and basalt FRP bars are used with 12 mm diameter and bar bond length of 5d, where d is the bar diameter. The FRP bars are casted in different recycled-aggregate concrete strengths of 30, 45 and 60 MPa. The behaviour of bars in natural-aggregate concrete strength of 30 MPa is used as a benchmark and its behaviour is compared with the ones in recycled-aggregate concrete. The impact of the concrete strengths considered is identified based on the gain in the bond behaviour. The experimental results demonstrate the promise of the recycled aggregates as an alternative to natural aggregates in FRP reinforced concrete. In addition, the use of recycled aggregate enlarges the bearing friction behaviour between the FRP bars and concrete. Analytical models proposed in the literature for the bond behaviour of FRP reinforced concrete are compared with the experimental results obtained here. Organgun et al. equation, and the CMR and the BPE models can accurately predict the bond strength, and bond stress–slip behaviour, respectively, of FRP bars in recycled-aggregate concrete.

Bond behaviour of recycled aggregate concrete with basalt fibre-reinforced polymer bars

The combination of recycled aggregate concrete (RAC) and fibre-reinforced polymer (FRP) bars can effectively avoid corrosion. Bond performance is an important factor affecting the bearing capacity of RAC structures reinforced with FRP bars. In this study, the effects of the contact interface, concrete type, bar dimension, and surface shape of FRP bars on the bond performance of 39 pull-out specimens were investigated. The failure mode was analysed, and the evolution of damage at the interface between the concrete and basalt fibre-reinforced polymer (BFRP) bars was investigated. Moreover, the bond mechanism and the characteristics of the bond stress-slip curves were revealed. The effects of the design parameters on the bond strength, bond stiffness, residual bond strength, and slip were determined. A constitutive model was proposed to simulate the bond stress-slip relationship. Formulae to estimate the characteristic parameters were derived to develop the proposed model. The proposed model was shown to agree well with the experimental bond stress-slip curves. Finally, the development length of the BFRP bar-reinforced RAC structures was determined. The findings from this study could promote the application of BFRP bar-reinforced RAC structures and provide an experimental and theoretical basis for the design of their bond performance.

Response of concrete columns reinforced with longitudinal and transverse BFRP bars under concentric and eccentric loading

This study investigates the behaviour of concrete columns reinforced with longitudinal and transverse basalt fiber-reinforced polymer (BFRP) bars, the most recent of FRP composites. Twelve full-scale concrete columns reinforced with longitudinal BFRP bars and either steel or BFRP ties were tested under both concentric and eccentric loadings. The investigated parameters included the type and spacing of the transverse reinforcement (BFRP and steel ties) and the load eccentricity-to-width ratio (e/h = 0, 22.2%, 44.4%). The test results showed that reducing the spacing of the BFRP ties improved the ductility and confinement efficiency of the BFRP-reinforced concrete (BFRP-RC) columns. However, reducing the ties’ spacing had an insignificant effect on both the load-carrying capacities of the columns and the contribution of the longitudinal bars to their ultimate capacities. Moreover, BFRP-RC columns confined with BFRP ties exhibited ultimate capacities, bar strength contribution, and confinement efficiency comparable with their counterpart columns confined with steel ties at the same spacing. This study displayed that the current code provisions of CSA-S806-R17 and ACI440.1R-15 for FRP transverse reinforcement can ensure adequate confinement of the concrete core for BFRP-RC columns.

Serviceability and Flexural Behavior of Concrete Beams Reinforced with Basalt Fiber-Reinforced Polymer (BFRP) Bars Exposed to Harsh Conditions.

The main objective of this study was to investigate experimentally and numerically the behavior of basalt fiber-reinforced polymer (BFRP) reinforcement exposed to a combination of ultraviolet rays, humidity, and rain. Specifically, the effects of the previously stated harsh exposure on the serviceability performance and flexural capacity of BFRP reinforced concrete beams was examined. Holding the exposure parameter constant, the study also evaluated the effects of reinforcement ratio and beam detailing on the flexural capacity and the bond-dependent coefficient (kb) of the beams. Seven beams were cast and tested, four of which were reinforced with exposed BFRP bars, two were reinforced with unexposed BFRP bars, and one specimen was cast and reinforced with steel bars to serve as a benchmark specimen. The results indicate that the kb factor was averaged to be 0.61 for all the beams. Test results also indicate that increasing the reinforcement ratio did not result in a directly proportional increase in the moment capacity. The period of exposure did not cause any significant impact on the behavior of the over-reinforced beams. Thus, a finite element model was created to simulate the impact of exposure on the behavior of under-reinforced BFRP reinforced concrete beams.

Potential advantages of basalt FRP bars compared to carbon FRP bars & conventional steel

ABSTRACT In this study an attempt is taken to evaluate the performance of basalt FRP bars compared with carbon FRP bars and conventional steel bars. Specimens of reinforced concrete will be casted to fulfil this comparison. These beams will comprise a common top reinforcement, stirrups spacing, and concrete properties. The difference is in the bottom reinforcement where it was once steel, Carbon FRP, Basalt FRP, and a hybrid of Basalt FRP and steel. These beams were tested for their behaviour under a flexural load through a four-point bending test. The remaining specimens were casted as columns with common stirrups spacing, and concrete properties. The behaviour of Basalt FRP, Carbon FRP, and steel reinforcement will be tested upon the application of an axial compressive load. The bonding strength between concrete and the different candidate bars is tested through the bond pull-out test. Furthermore, tests will be conducted on the thermal, chemical, and mechanical properties of the individual bars. This study is expected to yield an evaluation of the main characteristics of the newly developed Basalt FRP bars and an identification of the key differences and limitations of using BFRP in concrete structures in relation to CRFP and traditional steel reinforcement of concrete structure.

Durability of BFRP bars wrapped in seawater sea sand concrete

To investigate the durability of structures containing basalt fibre-reinforced polymer (BFRP) bars wrapped in seawater sea sand concrete (SWSSC) in marine environments, three sizes (including bare BFRP bars) of SWSSC-wrapped BFRP bars were subjected to laboratory accelerated corrosion tests in simulated seawater environments. The SWSSC thicknesses were set at 10 mm and 20 mm; the immersion temperatures were room temperature (~28 °C), 40 °C, and 60 °C; and the immersion media included a seawater, tap-water, and alkaline solution. The tensile properties of the SWSSC-wrapped BFRP bars after immersion were determined, and the degradation mechanism of the BFRP bars was investigated. Based on the results, the alkaline solution is more damaging to the BFRP bars than tap-water or seawater. Alkalinity is a key factor causing the degradation of the BFRP bars. Thus, the tensile strength retention of BFRP bars wrapped with thicker SWSSC, which has a higher alkalinity environment, could be lower than that of bare BFRP bars. In addition, prediction of the tensile strength retention of the SWSSC-wrapped BFRP bars based on Arrhenius relationship was conducted, and the prediction resutls agree well with the experimental results.

An Anchorage Technique for Shear Strengthening of RC T-Beams Using NSM-BFRP Bars and BFRP Sheet

This study presents a detailed experimental program for reinforced concrete T-beams strengthened in shear with near-surface mounted (NSM) basalt fiber-reinforced polymer (BFRP) bars. This paper aims to introduce and evaluate a nonmechanical anchorage technique for shear strengthening using NSM-BFRP bars. T-beams were strengthened using manually manufactured closed or U-shaped hybrid BFRP stirrups (BFRP bars and BFRP sheets). The experimental program was developed to study the effects of these anchorage techniques. The results showed that the shear capacity increased by 8%–46% for beams strengthened with NSM-BFRP bars without anchorage. However, the presence of the proposed anchorage system increased the shear capacity of the strengthened beams by 39.6%–81.6%. Moreover, the maximum strains induced in the BFRP bars ranged from 27 to 59% of their ultimate strains according to the spacing between the NSM and the presence of the anchorage. The proposed anchorage technique prevented the premature debonding of the NSM-BFRP bars.

Bond Behaviors between Ribbed BFRP Bars and Ecological High Ductility Cementitious Composites

Direct pull-out method was conducted to explore the bond stress-slip response of ribbed basalt fiber reinforced polymer (BFRP) bars embedded in ecological high ductility cementitious composites (Eco-HDCCs). The effects of the embedment length and cover thickness on the bond properties between Eco-HDCCs and the bars were described. Results indicate that the failure characteristics of the specimens depend on the embedment length and cover thickness of the BFRP bars. As the embedment lengths of the bars increase, the ultimate bond stress decreases while the ultimate slip increases. Besides, both the ultimate bond stress and ultimate slip show an increasing trend if the specimen has a cover thickness of less than 45 mm, while the increasing trend is slower if the specimen has a cover thickness of more than 45 mm. In addition, the strain of the specimen surface depends on the cover thickness, and the strain increases when the cover thickness is in a range of15 mm–35 mm. Moreover, certain embedment lengths and cover thicknesses of the BFRP bars are recommended in the structural design of bridge deck link slabs. The bond stress-slip relationship models of the BFRP bars in Eco-HDCCs are proposed based on the test results.