Recently, basalt-fiber-reinforced-polymer (BFRP) bars have emerged as a promising alternative to glass-fiber-reinforced-polymer (GFRP) bars. So far, however, BFRP bars have not been incorporated into ...design standards and specifications. This is due to limited studies and lack of knowledge on the performance of the bars in concrete, in particular, their bond durability when exposed to aggressive environments. This paper presents some results of an extensive research program investigating the bond durability behaviors of BFRP bars in concrete structures and the long-term bond-strength-retention predications of the BFRP bars on the basis of short-term tests results. This research included testing deformed BFRP bars measuring 12 mm in diameter. Pullout specimens were tested with direct tensile loading after being exposed to an alkaline solution (pH 12.9) for 1.5, 3, and 6 months at temperatures of 40 °C, 50 °C, and 60 °C. This paper investigated the effects of alkaline environment, exposure periods, and elevated temperatures on bond strength as well as the degradation mechanism and mode of failure of the BFRP-reinforced specimens. In addition, optical microscopy and scanning electronic microscopy were used to investigate the degradation of BFRP bars tested. The test results indicate an initial increase in the bond strength of the conditioned specimens as the temperature increased compared to their unconditioned specimens. After 1.5 months of exposure, the specimens conditioned at 50 °C and 60 °C, respectively, had bond-strength increases of 25% and 26%, while the specimens conditioned at 40 °C exhibited no noticeable changes (a minor decrease of 4.3%). Nevertheless, the bond strength of the conditioned specimens deteriorated during immersion. The highest bond-strength reductions occurred in the conditioned specimens after 6 months of exposure at 40 °C (a 16% loss), followed by specimens conditioned at 50 °C (7% loss) and 60 °C (5% loss) compared to their counterparts at 1.5 months. Lastly, the long-term bond-strength-retention predications of the BFRP bars after 50 years of service life in dry, moist, and moisture-saturated environments with mean annual temperatures between 5 °C and 35 °C ranged from 71% to 92%.
•Original study assessing the bond durability of BFRP bars embedded in concrete when exposed to harsh environments.•Assessing the effects of alkaline environment, exposure periods, and temperatures on bond strength of the tested specimens.•OM and SEM analysis were used to assess the degradation of BFRP bars used in this research study.•Long-term bond-strength-retention predications of the BFRP bars after 50 years according to fib Bulletin 40 were estimated.
Basalt-fiber-reinforced polymer (BFRP) bars are expected to provide benefits that are comparable or superior to other types of FRP while being significantly cost-effective. However, extensive ...investigations are needed to evaluate the long-term characteristics and durability performance of these bars. This article presents an experimental study that investigated the physical, mechanical, microstructural, and durability characteristics of newly developed basalt-fiber-reinforced polymer (BFRP) bars. The physical, mechanical properties and microstructural characteristics were evaluated first on the unconditioned BFRP bars. The durability performance of the BFRP bars was then assessed by conducting the mechanical tests, such as transverse-shear test, flexural test, and interlaminar-shear test, on the specimens after different exposure periods (1000; 3000; and 5000 h) at 60 °C. Thereafter, the BFRP bar properties were assessed and compared with the values obtained on the unconditioned specimens. The test parameter was conditioning time (1000; 3000; and 5000 h). The test results revealed that the unconditioned BFRP bars had the best physical properties. On the other hand, the long-term durability performance revealed that the transverse shear-strength, flexural-strength, and interlaminar shear-strength retention were decreased by 12%, 19%, and 21%, respectively.
•The study assessing the durability of BFRP bars when exposed to harsh environments.•Assessing the effects of aggressive environmental on mechanical strength of the tested specimens.•Physical Properties and SEM analysis were used to assess the degradation of BFRP bars.•Long-term predications of the BFRP bars according to Arrhenius and fib Bulletin 40 were estimated.
Prestressed concrete girders and piles with steel strands are used in construction of bridges in North America, due to their economy of design, fabrication, and installation. However, they are often ...exposed to harsh environments, which results in rapid degradation. Therefore, carbon fiber reinforced polymer (CFRP) tendons have successfully been introduced as prestressing reinforcement for pile applications. This paper presents a study on the physical characterization, microstructural analysis, and durability performance of unstressed and stressed carbon-fiber composite cables (CFCCs) for prestressing applications. This is achieved through testing 120 CFCC specimens, subjected to stress levels of about 40% and 65% of their guaranteed strength, and 51 specimens without sustained load under tension. Moreover, prediction models were introduced to assess the long-term performance and retentions of CFCC strands. The models included Arrhenius model, Fick's law, Fib Bulletin (40) model, and a developed approach that incorporates the effects of temperature, design life, and relative humidity of exposure into the environmental reduction factor. Based on the predication model, the tensile strength retention (CE) for CFCC strands, is predicted to retain over 0.95 and 0.84 of ultimate tensile strength for a relative humidity (RH) < 90% and a moisture saturated environment (RH = 100%), respectively, after 100 years of service life with elevated temperature and sustained load.
•Carbon fiber Composite Strands.•Sustained Load.•Durability of Carbon Fiber.•Long-Term performance of CFRP.
In the last decade, noncorrosive glass fiber-reinforced-polymer (GFRP) bars have become more widely accepted as cost-effective alternatives to steel bars in many applications for concrete structures ...(bridges, parking garages, and water tanks). Also, these reinforcing bars are valuable for temporary concrete structures such as soft-eyes in tunneling works. The cost of the GFRP bars can be optimized considering the type of resin according the application. Yet limited research seems to have investigated the durability of GFRP bars manufactured with different types of resin. In this study, the physical and mechanical properties of GFRP bars made with vinyl-ester, isophthalic polyester, or epoxy resins were evaluated first. The long-term performance of these bars under alkaline exposure simulating a concrete environment was then assessed in accordance with ASTM D7705. The alkaline exposure consisted in immersing the bars in an alkaline solution for 1000, 3000 and 5000 h at elevated temperature (60 °C) to accelerate the effects. Subsequently, the bar properties were assessed and compared with the values obtained on unconditioned reference specimens. The test results reveal that the vinyl-ester and epoxy GFRP bars had the best physical and mechanical properties and lowest degradation rate after conditioning in alkaline solution, while the polyester GFRP bars evidenced the lowest physical and mechanical properties and exhibited significant degradation of physical and mechanical properties after conditioning.
•Durability of GFRP bars made with polyester, vinyl-ester, or epoxy resin was investigated.•The physical and mechanical properties were assessed.•The long-term performance was evaluated under alkaline exposure simulating a concrete environment.
One of the biggest problems affecting bridges is the transverse cracking and deterioration of concrete bridge decks. The causes of early age cracking are primarily attributed to plastic shrinkage, ...temperature effects, autogenous shrinkage, and drying shrinkage. The cracks can be influenced by material characteristics, casting sequence, formwork, climate conditions, geometry, and time dependent factors. The cracking of bridge decks not only creates unsightly aesthetic condition but also greatly reduces durability. It leads to a loss of functionality, loss of stiffness, and ultimately loss of structural safety. This investigation consists of field, laboratory, and analytical phases. The experimental and field testing investigate the early age transverse cracking of bridge decks and evaluate the use of sealant materials. The research identifies suitable materials, for crack sealing, with an ability to span cracks of various widths and to achieve performance criteria such as penetration depth, bond strength, and elongation. This paper also analytically examines the effect of a wide range of parameters on the development of cracking such as the number of spans, the span length, girder spacing, deck thickness, concrete compressive strength, dead load, hydration, temperature, shrinkage, and creep. The importance of each parameter is identified and then evaluated. Also, the AASHTO Standard Specification limits live-load deflections to
L
/800 for ordinary bridges and
L
/1000 for bridges in urban areas that are subject to pedestrian use. The deflection is found to be an important parameter to affect cracking. A set of recommendations to limit the transverse deck cracks in bridge decks is also presented.
Many bridges are subject to lateral damage for their girders due to impact by over-height vehicles collision. In this study, the optimum configurations of carbon fiber reinforced polymers (CFRP) ...laminates were investigated to repair the laterally damaged prestressed concrete (PS) bridge girders. Experimental and analytical investigations were conducted to study the flexural behavior of 13 half-scale AASHTO type II PS girders under both static and fatigue loading. Lateral impact damage due to vehicle collision was simulated by sawing through the concrete of the bottom flange and slicing through one of the prestressing strands. The damaged concrete was repaired and CFRP systems (longitudinal soffit laminates and evenly spaced transverse U-wraps) were applied to restore the original flexural capacity and mitigate debonding of soffit CFRP longitudinal laminates. In addition to the static load tests for ten girders, three more girders were tested under fatigue loading cycles to investigate the behavior under simulated traffic conditions. Measurements of the applied load, the deflection at five different locations, strains along the cross-section height at mid-span, and multiple strains longitudinally along the bottom soffit were recorded. The study investigated and recommended the proper CFRP repair design in terms of the CFRP longitudinal layers and U-wrapping spacing to obtain flexural capacity improvement and desired failure modes for the repaired girders. Test results showed that with proper detailing, CFRP systems can be designed to restore the lost flexural capacity, sustain the fatigue load cycles, and maintain the desired failure mode.
Depletion of antioxidants in HDPE subjected to sunlight exposure was studied. Sunlight radiation was simulated using a laboratory xenon light weatherometer at three irradiation levels. Oxidative ...induction time (OIT) test was performed on different layers along the thickness of the test coupons to establish the antioxidant depletion throughout the exposure duration. The highest drop in OIT was obtained for the surface layer facing the radiation, followed by the backside layer which was exposed to indirect radiation reflected from the wall of the weatherometer. The core section showed a slower decrease under the same exposure conditions. Furthermore, the OIT depletion rate in the surface layer increased with radiation intensity. The study proved that the sunlight degradation of the tested polyethylene can be accelerated by increasing the irradiation intensity based on the reciprocity law.
•Effect of sustained loading and environmental conditioning on CFRP strands is studied experimentally.•Evaluation of tensile, shear and bond strength of CFRP strands after conditioning.•Tensile ...testing of carbon fiber tows and epoxy resin specimens after environmental conditioning.•Durability of CFRP strands was not affected by sustained loading and environmental conditioning.
This paper presents a comprehensive research conducted to study the synergistic effect of environmental conditions and sustained loading on the mechanical properties of Carbon Fiber Reinforced Polymer (CFRP) prestressing strands. The environmental conditions included exposure of CFRP strands to alkaline solution and sustained loading at an elevated temperature of 55 °C for 3000 and 7000 h. The sustained loading was equivalent to 65 percent of the guaranteed tensile strength of the strands. Mechanical testing performed on the strands included tensile, shear and bond strength as well as evaluation of the elastic modulus of the CFRP strands as affected by the environmental conditions and sustained loading. Durability of the constituent materials of the CFRP strands was also studied.
•Shear strength of GFRP-reinforced PCTL segments loaded on concave side.•Effects of concrete strength and reinforcement type and ratio on shear behavior of PCTL.•Shear failure mechanism of PCTL ...reinforced with GFRP bars subjected to loads on concave side.•Cracking behaviour of GFRP reinforced PCTLs loaded on negative curvature.•Design Equations to predict shear strength and deflection of GFRP reinforced PCTL.
This paper reports on an investigation into the behavior of GFRP-reinforced precast concrete tunnel lining (PCTL) segments loaded on the concave side subjected to transportation, storage, and settlement loads induced by soil settlement underneath tunnels and/or internal vehicular accidents. Shear tests were conducted on four full-scale PCTL segments with a rhomboidal shape measuring 1500 x 250 mm in rectangular cross section and an arched length of 2100 mm. Three main parameters—namely, reinforcement type, concrete strength, and longitudinal reinforcement ratio—were studied under three-point loading until failure. The results reveal that all specimens experienced shear failure due to the diagonal tension mode, even if initiated by the yielding of flexural bars in the steel-reinforced segment. PCTLs reinforced with GFRP or steel bars at the same ratio demonstrated comparable shear strengths and satisfied serviceability limits. The use of both a high reinforcement ratio and high-strength concrete (HSC) increased the shear strength of the GFRP-reinforced PCTL segments. Experimental results were employed to review and verify North American code provisions and existing models with some amendments to meet the requirements of designing tunnel segments reinforced with GFRP bars in terms of deflection in the service state and checking shear strength in the ultimate limit state. Measured deflection was used to compare the experimental values of the effective moment of inertia to predictions with current models to evaluate their accuracy. Based on the analysis of the results, Bischoff’s equation for the effective moment of inertia of FRP-RC structures was modified, and an equation was developed to predict the deflection of GFRP-reinforced PCTL segments with 98 % accuracy. Based on a comparison of experimental and predicted shear capacities, the combination of concrete contributions (including the arch-shape effect of PCTLs and the tie resistance in the modified compression field theory (MCFT), plasticity theory (PT), and modified critical shear crack theory (CSCT)) provided better predictions.
Abstract
Marine, coastal structures, and bridges deteriorate prematurely due to corrosion. Numerous failures have occurred in substructure members of these structures, such as piles, leading to very ...high repair and replacement costs. Problems related to corrosion could be resolved through the use of noncorroding materials such as fiber-reinforced polymer (FRP) bars. This paper presents the design, construction details, driving test procedures, and results of the field dynamic driving testing of precast glass-FRP (GFRP) reinforced concrete (RC) piles, as well as laboratory test results, to determine the piles flexural strength. Four piles were longitudinally and transversally reinforced with GFRP bars, spirals, and ties. Two of the piles were 6.0 m (approximately 20 ft) long, were fabricated, instrumented, and were laboratory tested for flexural strength. The other two piles were 18.0 m (approximately 60 ft) in length, were field installed and dynamically monitored. They were driven and monitored at the Arthur Drive Bridge project site in Lynn Haven, Panama City, Florida. Pile driving and testing were performed with a Vulcan 512 single-acting air hammer. The embedded data collectors (EDCs) were used to monitor the piles during driving operations. Field driving observations and results indicate that no pile damage occurred during installation. GFRP spirals successfully confined the concrete core of the piles and prevented cover spalling during driving. The maximum tensile and compressive stresses measured in the piles were well within the allowable design limits. Design aids and recommendations for good driving practices for GFRP-RC piles were presented. The promising results presented for the driven precast GFRP-RC piles represent a further step toward field application.
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