Degradation of bond between FRP and RC beams
TL;DR: In this article, the effects of cycles of salt fog, temperature and moisture as well as immersion in salt water on the bending response of beams externally reinforced with GFRP or CFRP, especially on bond between FRP reinforcement and concrete, were investigated.
About: This article is published in Composite Structures.The article was published on 2008-09-01. It has received 151 citations till now.
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TL;DR: In this article, the durability of the adhesive bond between concrete and carbon fiber reinforced polymers (CFRP) strengthening systems has been investigated under accelerated ageing conditions, i.e., at 40°C and 95% relative humidity.
137 citations
Cites background from "Degradation of bond between FRP and..."
...In the last decade, many researches were undertaken on the durability of ambient temperature cured resins used in construction [9,10], FRP reinforcements [11,12], and concrete/concrete or FRP/concrete bonded interfaces [13–23]....
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...As regards the bonded interfaces, substantial decreases in bond strength over ageing time (up to 40–50% loss in some cases) were observed under wet environments [13– 15,18–23], which was usually attributed to extensive moisture plasticization of the low Tg polymer adhesive and to additional breakage of interfacial bonds....
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TL;DR: In this article, a nonlinear local bond-slip model for fiber reinforced polymer (FRP) laminates externally bonded to concrete at elevated temperature is presented for future use in the theoretical modeling of fire resistance of FRP-strengthened concrete structures.
Abstract: This paper presents a nonlinear local bond-slip model for fiber reinforced polymer (FRP) laminates externally bonded to concrete at elevated temperature for future use in the theoretical modeling of fire resistance of FRP-strengthened concrete structures. The model is an extension of an existing two-parameter bond-slip model for FRP-to-concrete interfaces at ambient temperature. The two key parameters employed in the proposed bond-slip model, the interfacial fracture energy, Gf, and the interfacial brittleness index, B, were determined using existing shear test data of FRP-to-concrete bonded joints at elevated temperature. In the interpretation of test data, the influences of temperature-induced thermal stress and temperature-induced bond degradation are properly accounted for. As may be expected, the interfacial fracture energy, Gf, is found to be almost constant initially and then starts to decrease when the temperature approaches the glass transition temperature of the bonding adhesive; the int...
130 citations
Cites background from "Degradation of bond between FRP and..."
...8 which cannot be completely cured at ambient temperature (Silva and Biscaia 2008), and its is normally within the range of 45 C to 82 C (fib 2001; ACI 2008)....
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...For wet layup FRP sheets, the matrix and the bonding materials are generally the same epoxy material which cannot be completely cured at ambient temperature (Silva and Biscaia 2008), and its is normally within the range of 45 oC to 82 oC (fib 2001; ACI 2008)....
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TL;DR: In this paper, a total of 13 FRP-strengthened reinforced concrete beams were tested in flexure and analyzed using the finite element method; the various variables included bonding or no bonding of the FRP, the anchorage system, the amount of prestressing, and the span length.
123 citations
TL;DR: In this paper, the effects of moisture on the initial and long-term bonding behavior of fiber reinforced polymer (FRP) sheets to concrete interfaces have been investigated by means of a two-year experimental exposure program.
Abstract: The effects of moisture on the initial and long-term bonding behavior of fiber reinforced polymer (FRP) sheets to concrete interfaces have been investigated by means of a two-year experimental exposure program. The research is focused on the effects of (1) moisture at the time of FRP installation, in this paper termed “construction moisture,” consisting of concrete substratum surface moisture and external air moisture; and (2) moisture, in this paper termed “service moisture,” which normally varies throughout the service life of concrete. Concrete beams with FRP bonded to their soffits were prepared. Before bonding, concrete substrates were preconditioned with different moisture contents and treated with different primers. The FRP bonded concrete beams were then cured under different humidity conditions before being subjected to combined wet/dry (WD) and thermal cycling regimes to accelerate the exposure effects. Adhesives with different elastic moduli were used to investigate the long-term durability of ...
97 citations
TL;DR: In this article, double-lap shear tests were carried out to investigate the residual bond capacity of the basalt fiber-reinforced polymer (BFRP)-concrete interface.
Abstract: This paper presents an experimental investigation on the bond behavior between basalt fiber–reinforced polymer (BFRP) sheet and concrete substrate under the coupled effects of freeze-thaw cycling and sustained load. Test variables were freeze-thaw cycles, level of sustained load, and adhesive type. Double-lap shear specimens were used in the tests, and a specially designed reaction-loading system was used to apply the sustained load during freeze-thaw cycles. Specimens with or without sustained load were exposed to up to 300 freeze-thaw cycles. A modified epoxy resin, made by adding a toughening agent to the original epoxy resin, was used in the test to study the effect of adhesive type on the durability of the BFRP–concrete interface. Coupon tests were also conducted to determine the freeze-thaw resistance of the constituent materials of the BFRP–concrete interface. After exposure, double-lap shear tests were carried out to investigate the residual bond capacity of the BFRP–concrete interface. Di...
96 citations
References
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TL;DR: In this article, a single-lap shear test specimen was used to study the bond strength and force transfer of graphite/epoxy composite material plates adhered to concrete.
Abstract: One possible method for strengthening deteriorated concrete structures is to externally bond composite material plates to the concrete. To implement such a rehabilitation, the nature of the bond between the composite plate and the concrete must be understood. A single-lap shear test specimen was used to study the bond strength and force transfer of graphite/epoxy composite material plates adhered to concrete. Using a test specimen having a constant bond length, the influence of the surface preparation of the concrete, adhesive type, and concrete strength on the overall bond strength was examined. To determine the characteristics of force transfer from the plate into the concrete, additional bond tests were conducted. Based on the test results, recommendations for obtaining the highest strength bond are made. In addition, conclusions regarding the rate of force transfer and the maximum effective bond length for the joint studied are presented.
426 citations
"Degradation of bond between FRP and..." refers methods in this paper
...[7] showed a 36% decrease in ultimate strength for GFRP retrofitted specimens that were subjected to 100 wet/dry cycles, while a 19% reduction was shown for CFRP bonded specimens....
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TL;DR: The lack of a comprehensive, validated, and easily accessible data base for the durability of fiber-reinforced polymer (FRP) composites as related to civil infrastructure applications has been identified as a critical barrier to widespread acceptance of these materials by structural designers and civil engineers as discussed by the authors.
Abstract: The lack of a comprehensive, validated, and easily accessible data base for the durability of fiber-reinforced polymer (FRP) composites as related to civil infrastructure applications has been identified as a critical barrier to widespread acceptance of these materials by structural designers and civil engineers. This concern is emphasized since the structures of interest are primarily load bearing and are expected to remain in service over extended periods of time without significant inspection or maintenance. This paper presents a synopsis of a gap analysis study undertaken under the aegis of the Civil Engineering Research Foundation and the Federal Highway Administration to identify and prioritize critical gaps in durability data. The study focuses on the use of FRP in internal reinforcement, external strengthening, seismic retrofit, bridge decks, structural profiles, and panels. Environments of interest are moisture/solution, alkalinity, creep/relaxation, fatigue, fire, thermal effects (including free...
411 citations
Journal Article•
389 citations
"Degradation of bond between FRP and..." refers background in this paper
...The durability of a structure reinforced with FRP reflects its ability to resist cracking, oxidation, chemical degradation, delamination, wear, and/or the effects of foreign object damage for a specified period of time, under specified load and environmental conditions [1]....
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TL;DR: In this article, the effect of harsh environmental conditions such as wet/dry cycling using salt water on the performance of FRP-bonded concrete beams and on the interfacial bond between the fiber and the concrete was investigated.
Abstract: The strengthening of concrete structures in situ with externally bonded fiber reinforced plastic (FRP) composite sheets is increasingly being used for repair and rehabilitation of existing structures. This paper provides information in the area of long-term durability of concrete beams externally bonded with FRP sheets. It was intended to study the effect of harsh environmental conditions such as wet/dry cycling using salt water on the performance of FRP-bonded concrete beams and on the interfacial bond between the fiber and the concrete. Concrete beams were strengthened with four different types of FRP sheet: two carbon and two glass. Three different types of two-part epoxy were used. Test variables included (1) the type of fiber, (2) the type of epoxy system, and (3) the environmental exposure condition. The specimens were conditioned in two different environments: (a) room temperature (+20 °C), and (b) 300 wet/dry cycles (salt water was used for the wet cycles and hot air at 35 °C and 90% humidity for the dry). At the end of each exposure, load-deflection curves of the specimens were obtained in order to evaluate their maximum capacity, stiffness, and ductility. The performance of the wet/dry exposed specimens was compared with those kept at room temperature. Results showed that specimens subjected to wet/ dry environmental conditions and those kept at room temperature exhibited significant improvement in flexural strength when FRP sheets were bonded to the tension face of the concrete beams. However, the specimens subjected to wet/dry conditions showed less improvement than those kept at room temperature. None of the specimens failed due to FRP rupture but rather due to the debonding between the FRP sheet and the concrete interface. The selection of epoxy was shown to be very important for using the FRP strengthening technique, especially in a marine environment.
193 citations
"Degradation of bond between FRP and..." refers background in this paper
...Toutanji and Gomez [8] observed a strength reduction up to 33% on specimens made of different epoxies and subjected to 300 wet/dry cycles in salt water....
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TL;DR: In this article, chemical and physical changes in polymeric matrix resins following exposure to UV radiation, moisture, alkaline, and saline environments were characterized using gravimetric measurements.
Abstract: A major hindrance to the acceptance of polymer composites in civil engineering applications is the susceptibility of the polymeric matrix to weathering. The polymer matrix is prone to degradation initiated by ultraviolet (UV) radiation, moisture, temperature, and high pH environments. The objective of this study was to characterize chemical and physical changes in polymeric matrix resins following exposure to these environments. The ultimate goal is to identify factors that contribute to matrix resin degradation under environmental and mechanical stresses. Resin systems studied included vinylester and isophthalic polyester, both of which are commonly used in construction applications. Neat polymer films were exposed to UV radiation, moisture, alkaline, and saline environments. Diffusion of water, alkali, and saline solution into the polymers was calculated from gravimetric measurements. Changes in strength, viscoelastic response, and thermal properties were evaluated through tensile testing, dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were also used for detecting changes in the polymer surface following UV exposure.
154 citations
"Degradation of bond between FRP and..." refers background in this paper
...Concrete pore water is alkaline and a critical environment for glass fibres due to the hydration of the cement [4]....
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