Search Results (166)

This paper innovatively employs an epoxy-free composite layer with basalt fiber-reinforced polymer (BFRP) and engineered cementitious composite (ECC) to reinforce the two-way concrete slab structure. Five strengthened slabs and one reference slab were tested under biaxial bending moments with four-side simply supported conditions. The thickness of ECC (15, 25, 35 mm) and BFRP grid (1, 2, 3 mm) were selected as two main variables in the test program. The experimental results showed that the cracking and ultimate load of the strengthened slabs were substantially improved. Notably, the cracking pattern was shifted from diagonally concentrated cracks to discontinuous short cracks, with no apparent debonding of the composite layer. As the thickness of the BFRP grid and ECC increases, both the flexural capacity and stiffness improve, with decrease in the maximum deflection and effective utilization rate of steel reinforcement and BFRP grid at mid-span. Furthermore, a theoretical model considering different positional distribution of yield line was proposed to predict the bearing capacity of the strengthened slabs, with the calculated values aligned well with the experimental results. This research highlights the FRP–ECC composite as a robust reinforcement method for two-way slabs, and offers a good design-oriented reference basis in the field. Full article

To investigate the bonding performance between Northeast larch (Larix gmelinii) and carbon fiber-reinforced polymer (CFRP) as well as basalt fiber-reinforced polymer (BFRP), this paper systematically analyzes the effects of fiber-reinforced polymer (FRP) type, bonding length, and bonding width on the mechanical behavior of the interface through single shear pull-out tests. A total of 20 FRP-timber specimens were designed for the tests, and their ultimate bearing capacity, failure mode, strain distribution, and load-slip relationship were measured. The results indicate that BFRP exhibits greater ductility, averaging 35.04% higher than CFRP, while CFRP demonstrates significantly higher tensile strength, exceeding BFRP by 83.41%. The failure mode of CFRP specimens primarily involves debonding at the timber-adhesive interface, whereas BFRP specimens mainly exhibit debonding at the FRP-adhesive interface. An increase in bonding width leads to a larger bonding area, resulting in a higher ultimate load capacity. However, due to the limitations of effective bonding length, the ultimate load increases rapidly when bonding length is raised from 50 mm to 100 mm, but further increases in length yield diminish returns in load capacity. Strain distribution analysis reveals that the strain in FRP decreases linearly along the bonding length, with peak strain increasing as bonding width decreases. Based on the experimental data, a predictive model for interfacial debonding load capacity was developed, demonstrating good robustness with an average coefficient of determination (R²) of 0.65. This model provides a reliable theoretical reference for evaluating the ultimate load capacity of FRP-reinforced Northeast larch structures, while also offering essential experimental evidence and theoretical support for FRP reinforcement design in Northeast larch wood structures. Full article

This research aims to study the compressive behavior of concrete with partial replacement of fine aggregate by recycled rubber. In addition, the mechanical capacity of these concretes will be analyzed when reinforced by carbon fibers (CFRP) and basalt (BFRP) confinement. To carry out the work, 48 cylindrical test specimens were made, corresponding to 4 mixes, with different percentages of recycled rubber by volume (0%, 10%, 20%, and 30%). The compressive behavior of unreinforced concrete with and without recycled rubber, reinforced concrete made from concrete with and without recycled rubber previously taken to failure, and reinforced concrete with and without recycled rubber without prior failure were evaluated in order to assess the influence of concrete quality before placing the reinforcement. The results show that replacing fine aggregate with recycled rubber in concrete reduces its strength and stiffness, increasing its ductility, with the optimum replacement percentage being 10%. On the other hand, confining concrete with FRP (BFRP and CFRP) improves its strength and ductility compared to unconfined concrete, obtaining similar values regardless of the initial strength of the reinforcing concrete. Confining concrete with CFRP achieves strength improvements of 26% compared to reinforcement with BFRP. Full article

The anti-aging performance of stay cables in complex marine environments is directly related to the long-term service safety of sea-crossing cable-stayed bridge structures, and it has been recognized as one of the key issues for the priority evaluation of the structural performance of sea-crossing cable-stayed bridges with Basalt Fiber Reinforced Polymer (BFRP) cables. In this paper, the coupled aging effects of ultraviolet radiation, salt spray, temperature and humidity, and prestress on BFRP cables were taken into consideration. Accelerated aging tests involving the coupling of light, heat, water, salt, and prestress were carried out to simulate the actual marine service environment. The anti-aging performance of BFRP cables was investigated by combining the analysis of macro mechanical properties with the characterization of micro structural morphology. The results of the study were as follows: (1) With the increase in aging duration, the tensile strength and ultimate fracture strain of BFRP cables decreased gradually. The degradation rates of tensile strength and ultimate fracture strain of BFRP cables exhibited a decreasing trend, characterized by an initial rapid phase followed by a gradual slowdown under the coupled aging effects of light, heat, water, salt, and prestress. (2) Compared with the significant decrease in tensile strength, the elastic modulus of BFRP cables showed an insignificant decrease. The elastic modulus of BFRP cables was observed to exhibit a trend of initial decrease, subsequent increase, and another decrease, with an overall reduction. (3) Temperature and prestress were verified to exert a considerable influence on the anti-aging performance of BFRP cables. The influence of temperature on the degradation of aging performance of BFRP cables was found to be greater than that of prestress. (4) The degradation in the anti-aging performance of BFRP cables under coupled aging effects was confirmed to originate from the initiation and propagation of microcracks in the resin matrix, which were caused by the combined actions of prestress, photochemistry, and hydrolysis. Meanwhile, the damage to the fiber–resin interface was accelerated by chloride ions in seawater under high-temperature conditions, which ultimately led to a reduction in the anti-aging performance of BFRP cables. Full article

Two types of basalt fiber-reinforced polymer (BFRP) anchor cables—a Tension-concentrated anchor cable (TCAC) and a Pressure-dispersed anchor cable (PDAC)—were developed through structural modification of the rod body and implemented for reinforcing fractured rock masses on highway tunnel slopes in western Henan Province, China. The feasibility of replacing conventional steel rods with BFRP bars and the corresponding anchorage mechanisms were investigated. The experimental results indicate that the axial force distribution differs markedly between the two anchors. The TCAC exhibits a decreasing axial force with depth, forming a concave distribution under low load and a convex distribution under high load, with the force approaching zero beyond 100 cm. In contrast, the PDAC displays a relatively uniform axial force that sharply decreases near the bearing plate, and, under increasing load, the axial force at the anchorage end tends to rise; Both anchors demonstrate single-peak interfacial shear stress distributions. For the TCAC, the peak progressively shifts toward deeper regions with increasing load, whereas the peak of the PDAC consistently appears near the bearing plate, with only its magnitude increasing. Stability analysis using GEO5 software reveals that the slope safety factor increases from 1.32 (without anchors) to 1.36 (with anchors), thus satisfying the design requirements. The results reveal the different anchoring mechanisms of tension-concentrated anchor cables and pressure-dispersed anchor cables, providing practical guidance for their selection and application in slope stabilization engineering. Full article

Conventional Fiber-Reinforced Polymer (FRP) materials may exhibit certain performance uncertainties in harsh environments, limiting their reliability for structural strengthening. To address this, Basalt Fiber-Reinforced Polymer (BFRP) plates fabricated with silicate-modified epoxy resin are proposed for the flexural strengthening of reinforced concrete (RC) beams. The research aims to evaluate their short-term strengthening performance and establish a reliable calculation method for flexural capacity. Four-point bending tests were conducted to investigate the effects of BFRP plate thickness and end anchorage configuration on failure modes, flexural capacity, and ductility. Finite element simulations incorporating interfacial bond–slip behavior reproduced typical debonding failures, followed by a comprehensive parametric analysis. Based on the experimental and numerical results, a modified BFRP plate strain formula at debonding was proposed to establish a calculation method for the flexural capacity of BFRP-strengthened beams governed by debonding failure. The results indicate that beams without end anchorage were prone to interfacial debonding, where increasing the plate thickness from 0.5 mm to 2 mm raised the flexural capacity gain from 4.5% to 15% but intensified the ductility reduction from 42.9% to 64.9%. Conversely, applying mechanical anchorage improved the ductility index by over 20% compared to unanchored counterparts. The adopted FRP–concrete bond–slip constitutive model accurately characterizes interfacial debonding behavior, and the proposed flexural capacity model demonstrates high accuracy with overall deviations within 5%. It can be concluded that the novel BFRP plates exhibit strengthening behavior comparable to existing FRP systems. Effective end anchorage further enhances flexural capacity and prevents brittle failure. The proposed debonding strain formula for the novel BFRP system offers a reliable basis for capturing the critical onset of interfacial failure. Building upon this, the developed flexural capacity model provides a reliable theoretical basis for the design and assessment of RC beams strengthened with the novel BFRP plates. Full article

The application of fiber-reinforced polymer bars has been considered an alternative for the non-metallic reinforcement of concrete structures. Basalt fiber-reinforced polymer (BFRP) is a new composite used to reinforce concrete structures. However, the main drawback of BFRP is its low modulus of elasticity. Therefore, hybrid reinforced fiber polymers, in which carbon fibers replace part of the basalt fibers, might be considered as a relatively “simple” modification that can increase the modulus of elasticity. The literature data suggest that modification of the epoxy matrix with nanosilica particles can positively influence resistance to high temperatures. Besides the mechanical characteristics of FRPs, the evaluation of alkali resistance is necessary for technical approval for construction applications. This paper focuses on testing the alkali resistance of basalt fiber-reinforced polymer (BFRP) bars and its modification through the partial substitution of basalt fibers with carbon fibers (HFRP) and the addition of nanosilica to the epoxy binder (nHFRP). The alkali resistance was tested based on the most common method described in ACI report 440.3R-04—part B6. This method consists of three procedures carried out at 60 °C on the specimens immersed in an alkaline solution, both with and without load. The changes in the mass and tensile strength of the bars are examined after 1, 2, 3, 4, and 6 months. The test procedures are time-consuming and expensive, particularly Procedures B (in alkaline solution) and C (in concrete cover), in which longitudinal tested specimens must be immersed in alkaline solution and subjected to constant strain at an elevated temperature for a 6-month period. Therefore, this study proposes a test setup to achieve a less time-consuming and cheaper assessment of the alkali resistance of FRP bars. Additionally, the usefulness of the shear strength test for the evaluation of alkali resistance of FRP bars is also discussed. The results (Procedure A) indicate that modification of the composition of BFRP did not decrease the resistance to the alkaline environment in the case of HFRP (5% lower than in the case of BFRP). Under the same conditions, the decrease in the tensile strength of nHFRP was 40% higher than in the case of BFRP. This indicates that additional modification of the composition by adding nanosilica to the epoxy binder did not provide the expected stability of tensile properties at elevated temperatures. The results of the evaluation of alkali resistance according to Procedure B show that the device proposed for maintaining constant strain during the seasoning is promising. At this stage, the device makes it possible to conduct the tests at ambient temperature and yields a significantly lower decrease in tensile strength (10–14%) after 6 months, demonstrating a significant effect of temperature on the results of the FRP alkali resistance test. Full article

Prediction of the ultimate moment capacity (Mu) of BFRP-reinforced concrete beams is complicated by nonlinear parameter interactions and the linear-elastic response of BFRP, reducing the accuracy of conventional design models. This study develops an optimized machine learning (ML) framework incorporating random forest, extra trees, gradient boosting, adaboost, bagging, support vector regression, histogram-based gradient boosting, and ensemble voting and stacking strategies for reliable prediction of the Mu of BFRP-reinforced concrete beams. A comprehensive database of material, geometric, reinforcement, and BFRP mechanical parameters was analyzed, and model performance was evaluated using an 80/20 train–test split and 10-fold cross-validation based on R², RMSE, MAE, and MAPE. The stacking regressor demonstrated superior predictive performance, achieving an R² of 0.999 (RMSE = 0.590) in training and an R² of 0.988 (RMSE = 2.487) in testing, indicating excellent robustness and strong generalization capability in predicting Mu. Furthermore, interpretability analyses based on SHAP, PDP, ALE, and ICE demonstrate that span length (L) and beam depth (h) constitute the governing parameters in the prediction of Mu. Unlike prior studies focused mainly on predictive accuracy, this work proposes an optimized and interpretable stacking ensemble framework that integrates explainable AI with classical flexural mechanics for physically consistent and reliable prediction of the ultimate moment capacity of BFRP-reinforced concrete beams. Full article

To investigate the dynamic response patterns of basalt-fiber-reinforced concrete slabs under random wave loads, this study characterized wave characteristics based on the random wave theory. Numerical simulations of wave loads were conducted using the Morrison equation, and an analytical model for basalt-fiber-reinforced concrete slabs was established. The research systematically examined the influence mechanisms of two key factors—effective wave period and incident angle—on the dynamic properties of such components. The results indicate that when the effective wave period increases from 7 s to 11 s, the peak displacement, peak stress, peak strain, and stress in the basalt-fiber reinforcement of the slab decrease by 12.79 mm, 0.93 MPa, 130 με, and 229.25 MPa, respectively. The growth rate of the component’s dynamic response first increases and then decreases as the effective wave period shortens. When the wave incidence angle increased from 18° to 90°, the peak displacement, peak stress, peak strain, and stress in the basalt-fiber reinforcement of the concrete slab increased by 17.87 mm, 1.32 MPa, 155 με, and 297.97 MPa, respectively. The growth rate of the component’s dynamic response exhibited a continuous increase with the increasing wave incidence angle. At an incidence angle of 18°, the values of the aforementioned four indicators were 576%, 213%, 52.5%, and 46% higher than those under the 90° condition, respectively. The findings of this study provide theoretical support and data references for elucidating the dynamic response patterns of basalt-fiber-reinforced concrete-slab structures under varying wave-loading conditions and for conducting fatigue performance research. Full article

The shear behavior of basalt fiber-reinforced polymer (BFRP) bars is crucial for their applications in geotechnical reinforcement and composite structures. In this study, double-side direct shear tests were conducted to investigate the progressive failure mechanism of BFRP bars. The results reveal a three-stage process: initial matrix-dominated vertical shear, followed by fiber-bridging dominated oblique tension-shear, and finally formation of a “brush-like” fracture surface with significant residual strength. The average peak shear strength of the ten specimens was 204.04 MPa with a coefficient of variation of 7.25%, while the initial shear modulus averaged 3.37 GPa with a coefficient of variation of 11.82%. Based on statistical damage theory, a shear constitutive model incorporating fiber bridging and residual strength is established. Parameter analysis indicates that the shape parameter m governs the post-peak softening rate, while the residual strength τ_res essentially determines the height of the residual plateau. The model achieves a goodness-of-fit (R²) exceeding 0.98 for most specimens, accurately describing the mechanical behavior from linear elasticity, damage-induced hardening, peak softening, to the residual stage. This study provides theoretical and experimental support for the engineering application of BFRP bars under complex stress states. Full article

In this paper, the bond performance of tensile lap-spliced Glass and Basalt Fiber-Reinforced Polymer bars is investigated in high-strength concrete. Eighteen large-scale GFRP-reinforced concrete beams were fabricated and subjected to four-point loading. Key parameters explored included bar diameter and splice length for both GFRP and BFRP reinforcement. The results indicate that the flexural capacity of GFRP-reinforced beams was comparable to that of BFRP-reinforced beams, though BFRP bars exhibited marginally superior bond and strength with concrete. The bond strength of spliced FRP bars was directly proportional to the splice length. This study also determined that characteristics of development lengths necessitate splice lengths that exceed the bar diameter 40 times to mitigate bond stress. Critical splice lengths, derived from experimental findings, were compared with existing models and code-based equations, specifically, Guide for the Design and Construction of Structural Concrete Reinforced with Fiber-Reinforced Polymer Bars (ACI 440.1R-15) and Canadian standard that provides comprehensive guidelines for incorporating Fiber-Reinforced Polymer reinforcement in concrete structures (CSA S806-12). Both codes were conservative in splice length prediction for GFRP and BFRP bars, with ACI 440.1R-15 showing greater accuracy for BFRP bars with a larger diameter. A modification factor, based on hyperbolic functions, is proposed to enhance the accuracy of ACI 440.1R-15 in predicting splice lengths for various FRP bar diameters. Full article

Basalt Fiber Reinforced Polymer (BFRP) bolts offer a high mechanical performance, yet their non-destructive evaluation in anchorage systems remains scarcely investigated. This work examines guided wave propagation in BFRP bolt anchorage structures through a combined experimental and numerical analysis. Optimal excitation within 35–100 kHz was determined experimentally, revealing 40 kHz as the most stable mode, with a pronounced bottom reflection and a peak-to-peak amplitude of 0.31 V. Numerical simulations explored the influence of anchorage medium properties, bolt characteristics, and de-bonding defect locations and lengths on dispersion, attenuation, velocity, radial energy distribution, and echo response. The results indicate that denser anchorage media reduce velocity and attenuation but enhance radial nonuniformity, whereas a higher elastic modulus decreases amplitude and increases attenuation; a larger Poisson’s ratio elevates both velocity and attenuation. For the bolt, a higher density lowers velocity and attenuation, while a greater modulus amplifies both; Poisson’s ratio exerts a minor positive effect. Defect echo time varies linearly with defect position, and increasing the defect length elevates velocity yet diminishes amplitude. These findings elucidate the interplay between material parameters, defect geometry, and guided wave behavior, offering a basis for the optimized non-destructive testing (NDT) of BFRP bolts and facilitating their deployment in engineering applications. Full article

Timber has gained popularity in the construction industry in recent years due to its low carbon footprint, favorable seismic performance, and esthetic appeal. However, due to the size limit and inevitable natural defects such as knots in the lumber, the axial capacity of timber columns might be insufficient. Therefore, wrapping the timber column with basalt fiber-reinforced polymers (BFRPs), which is an environmentally sustainable material, to improve the load-carrying capacity has been a promising technology. While existing research mostly focuses on defect-free specimens, this study investigates the effects of knots on the structural performance of timber columns wrapped by BFRP. Axial compressive tests were carried out on timber columns, i.e., Douglas fir (knot-free) and camphor pine (with knots), wrapped by BFRP. The results showed that the load-carrying capacity, stiffness, and ductility can be significantly enhanced by the BFRP wrapping. The failure mode of the Douglas fir specimens transitioned from timber crushing failure to shear failure, while the camphor pine specimens failed around the knot area, and the failure mode changed from overall bending to BFRP rupture when the three layers of BFRP were employed. Furthermore, compared to knot-free columns, those specimens containing knots exhibited greater variability in load capacity and recorded a higher percentage increase in strength after reinforcement by BFRP. Based on the test results, three prediction models of the compressive strength of the BFRP-wrapped Douglas fir and camphor pine columns are presented. Full article

Hierarchical aramid/zirconia hybrid fibers were introduced into the interlayers of basalt fiber–reinforced polymer (BFRP) composites to optimize their interlaminar properties. The reinforcing effect of micro/nano aramid short fiber (MNASF) and zirconia fiber (ZF) on BFRP composites at different mass ratios was investigated through three-point bending (3PB) tests and compression tests. The results demonstrated that the BFRP composites incorporating 2 wt.% MNASF and 2 wt.% ZF exhibited the most significant property enhancement. The 3PB tests revealed increases in flexural strength and modulus of 119.2% and 62.6%, respectively, compared to the unreinforced BFRP composites. Compression tests showed that this specific formulation enhanced the compressive strength and modulus by 257.7% and 121.6%, respectively. Scanning electron microscopy and optical microscopy observations indicated that the incorporation of MNASF and ZF effectively reduced the volume fraction of resin-rich regions in the interlaminar regions, and the dominant failure mode transitioned from delamination to shear failure. Overall, the introduction of MNASF and ZF effectively combined the reinforcing effects of the two fibers, improving the mechanical properties of BFRP composites. Full article

The incorporation of Basalt Fiber-Reinforced Polymer (BFRP) materials marks a significant advancement in the adoption of sustainable and high-performance technologies in structural engineering. This study investigates the flexural behavior of four-meter, two-span continuous reinforced concrete (RC) beams of low and medium compressive strengths (20 MPa and 32 MPa) strengthened or rehabilitated using near-surface mounted (NSM) BFRP ropes. Six RC beam specimens were tested, of which two were strengthened before loading and two were rehabilitated after being preloaded to 70% of their ultimate capacity. The experimental program was complemented by Finite Element Modeling (FEM) and analytical evaluations per ACI 440.2R-08 guidelines. The results demonstrated that NSM-BFRP rope application led to a flexural strength increase ranging from 18% to 44% ductility by approximately 9–11% in strengthened beams and 13–20% in rehabilitated beams, relative to the control specimens. Load-deflection responses showed close alignment between experimental and FEM results, with prediction errors ranging from 0.125% to 7.3%. This study uniquely contributes to the literature by evaluating both strengthening and post-damage rehabilitation of continuous RC beams using NSM-BFRP ropes, a novel and eco-efficient retrofitting technique with proven performance in enhancing structural capacity and serviceability. Full article