Middle-East Journal of Scientific Research 13 (10): 1312-1318, 2013 ISSN 1990-9233 © IDOSI Publications, 2013 DOI: 10.5829/idosi.mejsr.2013.13.10.1180

Review on Various Types and Failures of Fibre Reinforcement Polymer Mahdi Feizbahr, Jayaprakash, Morteza Jamshidi and Choong Kok Keong School of Civil engineering, Engineering campus, University Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia Abstract: Fibre reinforcement polymer (FRP) is a repair material of fibres of high strength, high stiffness embedded in a polymer matrix with tensile strength of 1000-5000 MPa in different varieties. The FRP matrix consists of a polymer or resin used as binder for the reinforcing fibres. The use of FRP has been increased because of their high strength to weight ratio, low longitudinal and transverse coefficient of thermal expansion, low sensitivity to fatigue loads and adequate resistant in aggressive environment. A lot of research reported the different properties of FRP exposed to different cracks and environmental conditions. This paper presents a review of different FRP types, their properties and their probable failures in various conditions by means of experimental and numerical research results. Key words: FRP

Reinforce concrete

Retrofitting

INTRODUCTION Increase in construction has caused fibre reinforced polymers (FRPs) which has been mostly considered for aerospace aims become a common material in civil engineering structure [1]. These high strength polymer fibres, like carbon (CFRP), glass (GFRP) and aramid fibres (AFRP) have revealed great potentials for reinforcement for concrete, in long-term performance [2]. Corrosion resistance, light weight and capability to form various sectional shapes causes FRP composite plates or sheets become popular because of the advantages of FRP composites such as their high strength-to-weight ratio, good corrosion resistance and versatility in coping with different sectional shapes and corners [3]. FRPs have been employed in a variety of ways, which increasing the strength of reinforced concrete is one of them in order to maintain or repair economically beams columns or slabs. FRP coating around concrete is generally satisfactory. However, cracks in high shear strength areas, cause delamination or debonding of FRP from structures since concrete have a small resistant in the face of high shear stresses [4].

Debonding

RC beams

Strengthening

Variety of mechanisms caused failure in FRPs, which all depend on concrete grade, rebar provision, properties of FRP and service environments. Debonding mostly happens at laminate ends and existing crack where shear concentration occurs [5]. Debonding mostly initiates and propagates at the high moment region towards one of the FRP plate ends. Debonding might happen in three different modes: (a) critical diagonal crack (CDC) debonding, (b) concrete cover separation and (c) plate end interfacial debonding [6]. These failures depend on the bond behavior at the concrete-FRP reinforcement interface and generally happen with the detachment of a more or less thick concrete cover. Location of failure along the beam and thickness of concrete depend mainly on cracking pattern, internal steel reinforcement percentage, presence of steel stirrups, loading scheme and interaction between shear and normal bond stresses along the interfaces [7]. Beams fail in shear mainly in one of the two modes: tensile rupture of the FRP; and debonding of the FRP from the sides of the RC beam, depending on how the beam is strengthened [3]. The aim of this study is to investigate the variety of FRP applications and its failures due to different exposure conditions and loads.

Corresponding Author: Mahdi Feizbahr, Jayaprakash, Morteza Jamshidi and Choong Kok Keong, School of Civil engineering, Engineering campus, University Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia

1312

Middle-East J. Sci. Res., 13 (10): 1312-1318, 2013

Typical Failure of Concrete Beam Beam Cracks: Failure in load carrying capacity of concrete structures depends on the spread behavior of shear stresses across cracks. Ability to transmit the shear stress across the surface roughness is important. From the other point of view, the shear transmission capability in intact concrete, in comparison to shear deformations is much lower [8]. If shear resistant is being considered based on aggregate interlock, then the possibility of shear produced fractures is obviously in concern. It is assumed that previously occurred discontinuous loading cracks, will be extended by shear load and convert into continuous cracks which might lead to brittle failure [9]. Slowik and Nowicki [10], tested some beams under pure flexural mode and showed that by increasing the concentrated applied loads, the flexural cracks occurred at the mid span and increased the load rating resulted in mentioned cracks became wider insignificantly. Consequently, the collapse of the beam occurred due to extension of the diagonal shear crack between the applied load location and support at one side of the beam. Composite material can be used to retard cracks and some other structural or functional deficiencies and also can enhance the structural capacity [10]. The civil engineering industry is constantly striving for ways to improve design and construction technologies to obtain a more economical solution for engineering problems. It has long been recognized that, in the area of construction involving reinforced concrete beams, the region of the beam, below the neutral axis is waste of material. Concrete is very weak in tension and the sole use of this material in this location is to position the reinforcing steel bars and to protect them from aggressive environments. However, this latter property is not completely fulfilled as the concrete in the tensile zone of the loaded beam will crack [11]. Delamination: Delamination of FRP which frequently occurs at the end anchor and/or in the intermediate cracks is one of the important problems that may lead to the brittle failure of the concrete structure specially when is designed regarding the ultimate bending moments [12,13]. FRP Types: Several methods have been proposed so far for flexural and shear strengthening of reinforced concrete (RC) elements, based on the use of FRP plates or sheets. These techniques allow for a significant improvement of structural behavior under ultimate loadings. Recent

studies showed that FRP retrofit could be very useful to improve the behavior of RC structures under both shortterm and long-term service loadings. These techniques are competitive with respect to conventional retrofit criteria when low-weight increments and reduced application times are design requirements [12]. Carbon Fibre Reinforced Polymers (CFRP): Carbon fibre-reinforced polymer (CFRP) is extensively used for retrofitting strategy based on its excellent features such as high tensile strength, light weight, excellent corrosion resistance and fatigue strength. It should be bounded to the tension region of the concrete element to enhance its flexural strength, control the growth of the cracks and increase serviceability of the beams; even it can also be used for rehabilitation of steel structures. FERRACUTI [13,14] conducted some experimental study based on Double shear test to identify the effect of concrete strength, width of CFRP plates and mechanical anchorages on the retrofitted specimens that show, increasing the concrete strength and decreasing the width of the CFRP improved the bond strength; bond behaviour between CFRP plates and concrete. Ferracuti et al. [13] used CFRP as a retrofitting method to delay a local buckling of square hollow section which were subjected to axial load and showed the axial capacity was enhanced using CFRP. Near surface mounted (NSM) and externally bonded reinforcement (EBR) are CFRP based strengthening techniques, used for the structural rehabilitation of concrete structures. NSM is based on using bar of CFRP, applied into pre-cut slits opened on the concrete cover. Ferracuti et al. [14] studied on efficacy of these techniques for the flexural and shear strengthening of concrete beams and showed that use of NSM method is more recommended for improving the flexural behavior of an element compared to the EBR, but this advantage would be removed by increasing the longitudinal equivalent reinforcement ratio. They concluded that it would be advantage to use NSM method for rehabilitation the shear performance of the beam; and application of the EBR might lead to the brittle failure which was not observed in the NSM method. Another study was carried out by Bambach et al. [15] to evaluate the flexural behavior of RC beams strengthened with prestressed CFRP plates. The results proposed that spalling is the main reason of nonprestressed cases, but prestressed specimens failed due to the CFRP plate failure.

1313

Middle-East J. Sci. Res., 13 (10): 1312-1318, 2013

Fig. 1: (a) Failure by interface debonding and (b) Tensile failure of CFRP plate [15]

Fig. 2: U-strips wrapped GFRP[18] Glass Fibre Reinforced Polymers (GFRP): Glass fibre reinforced polymer (GFRP) which has been recently produced is a useful material in an aggressive environment [16]. GFRP rebars have a high tensile strength, light weight, non-corrosive, anti-fatigue and non-magnetic properties [17]. It is high effective to rehabiliate the shear strength of the beam [18]. Reduced post cracking stiffness and slip between rebar and concrete matrix are the most important parameters of GFRP failures [19]. Reinforcement of more than 2% of GFRP does not let stress to enhance considerably. Indeed it would be ineffective to increase the section of reinforcements in GFRP more than 2% while there is no considerable increase in the stress. A constant loading GFRP reinforced beams compared to steel reinforcement ones have less deflection [20]. A new cost-effective movable hybrid GFRP and concrete deck consisting of corrugated pultruded GFRP plate with T-upstands and concrete with reinforcing bars was suggested for the tension part and the compression part, respectively. A lightweight and high strength pultruded GFRP plate can be employed in formworks and replacing reinforcing bars in hybrid GFRP and concrete

Fig. 3: Reinforcement of the steel beams and GFRP. bridge deck which cause reduction in the construction period while construction quality can be controlled considerably [21]. Investigation over post-cracking strength and ductility on glass-GFRP composite beams indicate that in glass-GFRP composite beams, after the initial cracking of glass, it would be possible to obtain relatively ductile failure modes, with a considerable increase of strength and deformation capability, while it would be impossible in glass beam [22]. Because of the low Young’s modulus and high strength of GFRP, the loading capacity of I-section beams made by FRP is restricted by the excessive deformation and/or local and global buckling rather than material strength [23].

1314

Middle-East J. Sci. Res., 13 (10): 1312-1318, 2013

Fig. 4: Hybrid GFRP and concrete bridge deck (1-corrugated pultruded GFRP plate with T-upstands; 2-penetrating bars through T-upstands; 3-distributing reinforcing bars; 4-longitude reinforcing bars and 5-concrete slab).

Fig. 6: Lateral torsional buckling [23]

Fig. 5: Beam I-PU: crack pattern and deformation before unloading Aramid Fibre Reinforced Polymers (AFRP): Aramid fibre is a well-known synthetic organic polymer fibre with the lowest specific gravity and highest tensile strength-toweight ratio of all reinforcing fibres. It also possesses good resistance to abrasion, corrosion, impact, chemicals and thermal degradation. However, aramid fibres present low compressive strength and degrade when exposed to ultraviolet light and are difficult to machine [24, 25]. The experimental and numerical investigation carried out by He et al. [24] and Correia et al. [25] on short columns with square high-strength concrete, restricted by AFRP sheets expressed that both strength and ductility of the columns were increased in the case of fully wrapped AFRP sheets, while, when AFRP sheets were partially wrapped, only the strength was enhanced. To meet the ACI-318 deflection requirement, He et al. [24] proposed that the prestress level is better to be restricted as low as 40% ultimate and also it was shown that use of the prestress AFRP tendons as a retrofitting strategy enhanced the cracking load.

Fig. 7: Wrinkle of AFRP sheets Durability test of concrete cylinders confined with AFRP composite sheets were tested in axial compression and their stress-strain response showed that the influence of wet/dry environment on the compressive strength of AFRP wrapped specimens was not so much and also ductility was not changed in those specimens. However, freeze/thaw environment has a bit effect on the compression strength and decreased it by about 7.9% [25]. FRP Rebars: Composite FRP rebars are considered as a corrosion free alternative for reinforced concrete structures [26]. High-performance inorganic and organic ?bers, such as glass, carbon and aramid ?bers, are being used in FRP rebars which exhibit good mechanical property exposed to elevated temperature [27]. FRP rebars can be advantageously used as reinforcement for concrete exposed to corrosive environments [28].

1315

Middle-East J. Sci. Res., 13 (10): 1312-1318, 2013

Bond behavior of GFRP rebars is lower than steel rebar. Also, adhesion of GFRP rebars and its friction is the critical property which controls the bond strength. Moreover, while the diameter of the rebar increases, the average maximum bond strength decreases [29]. According to the experimental investigation, Wang and Wu [30] showed that in normal strength concrete, bond strength of FRP rebars is almost 40-100 % of the bond strength of a steel rebars. Due to exposure in relatively high temperatures, bond between FRP rebars and concrete degrades. In addition, in the case of fire resistant, FRP reinforced concrete beams significantly decreased in shear and flexural strengths so a minimum concrete cover of 64 mm for FRP reinforced concrete is recommended [31]. FRP Failures: Deboning is a failure depends on the bond behavior at the concrete-FRP reinforcement interface which usually happens with the detachment of a more or less thick concrete cover [6]. In the high moment region, debonding normally initiates at a flexural or flexural-shear crack and spreads towards one of the plate ends and it also may occur at or near a plate end [6]. To analyze the plate-end debonding of the beam, it is a need to predict where the critical debonding initiates. Result of research performed by Toutanji and Deng [32] indicate that horizontal extension of the original crack at the steel level or from the toe of a shear crack is the main reason of the initiation of the FRP debonding. During debonding, with a constant load, the stress transfer zone is shown to propagate in a self-similar manner. With increase of the width of concrete, the width of FRP increases which causes the nominal stress at debonding increase [33]. Katz et al. [34] conducted experimental test on the effect of the multiply secondary cracks on the FRP debonding and showed that it will occur at force which is significantly higher than the force corresponding to the pull-off tests results. The peeling effect induced by the transverse displacement jump makes debonding much easier to initiate than in the case of flexural cracks. However, this peeling effect on debonding reduces with the debonding progression [35]. By applying improved hybrid bonded FRP as a debonding prevention, it is found that ultimate load ratio decreases with increase of the steel reinforcement ratio. But by changing the fastener spacing from 100 mm to 200 mm in constant condition, the ultimate load increases. It has also been found that the ultimate load can be expressed as a linear function of the cross sectional area of FRP strips [36].

CONCLUSION This paper provides a review over FRP research papers and is mostly focused on the behavior of FRPs as retrofitting materials to enhance the RC strength and extend its durability. The strengthening of reinforce concrete cracks, debonding, buckling and thermal increase are widely discussed as main failure. Investigation on bond behavior of FRP at the ends of the beam and high shear area to achieve an acceptable strength is still in demand for further researches. Moreover, development of new bonding models and cracks propagation prediction methods is recommended. REFERENCES 1.

Camli, U.S. and B. Binici, 2007. Strength of carbon fiber reinforced polymers bonded to concrete and masonry. Construction and Building Materials, 21: 1431-1446. 2. Islam, M.R., M.A. Mansur and M. Maalej, 2005. Shear strengthening of RC deep beams using externally bonded FRP systems. Cement and Concrete Composites, 27: 413-420. 3. Chen, J.F. and J.G. Teng, 2003. Shear capacity of FRP-strengthened RC beams: FRP debonding. Construction and Building Materials, 17: 27-41. 4. Pham, H. and R. Al-mahaidi, Experimental investigation into flexural retrofitting of reinforced concrete bridge beams using FRP composites. Composite Structures, 66: 617-625. 5. AU, C. and O. Büyüköztürk, 2006. Debonding of FRP plated concrete: A tri-layer fracture treatment. Engineering Fracture Mechanics, 73: 348-365. 6. Yao, J. and J.G. Teng, 2007. Plate end debonding in FRP-plated RC beams-I: Experiments. Engineering Structures, 29: 2457-2471. 7. F.C., 2010. Experimental performances of RC beams strengthened with FRP materials. Construction and Building Materials, 24: 1547-1559. 8. Bazoant, Z. and P.G. Gambarova, 1984. Crack shear in concrete: Crack band microplane model. Journal of Structural Engineering, 110: 2015-2035. 9. BA ANT, Z. and P. Pfeiffer, 1986. Shear fracture tests of concrete. Materials and Structures, 19: 111-121. 10. S owik, M. and T. Nowicki, 2012. The analysis of diagonal crack propagation in concrete beams. Computational Materials Science, 52: 261-267.

1316

Middle-East J. Sci. Res., 13 (10): 1312-1318, 2013

11. Karbhari, V.M. and L. Zhao, 2000. Use of composites for 21st century civil infrastructure. Computer Methods in Applied Mechanics and Engineering, 185: 433-454. 12. L.C, H., The evolution of and the way forward for advanced polymer composites in the civil infrastructure. Construction and Building Materials, 17: 365-378. 13. Ferracuti, B., M. Savoia and C. Mazzotti, 2007. Interface law for FRP-concrete delamination. Composite Structures, 80: 523-531. 14. Ferracuti, B., M. Savoia and C. Mazzotti, A numerical model for FRP-concrete delamination. Composites Part B: Engineering, 37: 356-364. 15. Bambach, M.R., H.H. Jama and M. Elchalakani, 2009. Axial capacity and design of thin-walled steel SHS strengthened with CFRP. Thin-Walled Structures, 47: 1112-1121. 16. Xue, W., L. Zeng and Y. Tan, 2008. Experimental studies on bond behaviour of high strength CFRP plates. Composites Part B: Engineering, 39: 592-603. 17. Barros, J.A.O., S.J.E. Dias and J.L.T. Lima, 2007. Efficacy of CFRP-based techniques for the flexural and shear strengthening of concrete beams. Cement and Concrete Composites, 29: 203-217. 18. Woo, S.K., J.W. Nam, J.H. Kim, S.H. Han and K.J. Byun, 2008. Suggestion of flexural capacity evaluation and prediction of prestressed CFRP strengthened design. Engineering Structures, 30: 3751-3763. 19. Barris, C., L. Torres, A. Turon, M. Baena and A. Catalan, 2009. An experimental study of the flexural behaviour of GFRP RC beams and comparison with prediction models. Composite Structures, 91: 286-295. 20. Hao, Q., Y. Wang and J. Ou, 2008. Design recommendations for bond between GFRP/steel wire composite rebars and concrete. Engineering Structures, 30: 3239-3246. 21. Sundarraja, M.C. and S. Rajamohan, 2009. Strengthening of RC beams in shear using GFRP inclined strips-An experimental study. Construction and Building Materials, 23: 856-864. 22. Saikia, B., P. Kumar, J. Thomas, K.S.N. Rao and A. Ramaswamy, 2007. Strength and serviceability performance of beams reinforced with GFRP bars in flexure. Construction and Building Materials, 21: 1709-1719.

23. Masmoudi, A., M. Ben Ouezdou and J. Bouaziz, 2012. New parameter design of GFRP RC beams. Construction and Building Materials, 29: 627-632. 24. He, J., Y. Liu, A. Chen and L. Dai, 2012. Experimental investigation of movable hybrid GFRP and concrete bridge deck. Construction and Building Materials, 26: 49-64. 25. Correia, J.R., L. Valarinho and F.A. Branco, 2011b. Post-cracking strength and ductility of glass-GFRP composite beams. Composite Structures, 93: 2299-2309. 26. Correia, J.R., F.A. Branco, N.M.F. Silva, D. Camotim and N. Silvestre, 2011a. First-order, buckling and post-buckling behaviour of GFRP pultruded beams. Part 1: Experimental study. Computers and amp; Structures, 89: 2052-2064. 27. Yahyaei-Moayyed, M. and F. Taheri, 2011. Experimental and computational investigations into creep response of AFRP reinforced timber beams. Composite Structures, 93: 616-628. 28. Saafi, M. and H. Toutanji, 1998. Flexural capacity of prestressed concrete beams reinforced with aramid fiber reinforced polymer (AFRP) rectangular tendons. Construction and Building Materials, 12: 245-249. 29. Wang, Y. and H. Wu, 2010. Experimental Investigation on Square High-Strength Concrete Short Columns Confined with AFRP Sheets. Journal of composites for construction, 14: 346. 30. Wang, Y. and H. Wu, 2011. Size Effect of Concrete Short Columns Confined with Aramid FRP Jackets. Journal of composites for construction, 15: 535. 31. Kim, Y.J., 2010. Flexural Response of Concrete Beams Prestressed with AFRP Tendons: Numerical Investigation. Journal of composites for construction, 14: 647. 32. Toutanji, H. and Y. Deng, 2002. Strength and durability performance of concrete axially loaded members confined with AFRP composite sheets. Composites Part B: Engineering, 33: 255-261. 33. Tighiouart, B., B. Benmokrane and P. Mukhopadhyaya, 1999. Bond strength of glass FRP rebar splices in beams under static loading. Construction and Building Materials, 13: 383-392. 34. Katz, A., N. Berman and L.C. Bank, 1999. Effect of high temperature on bond strength of FRP rebars. Journal of composites for construction, 3: 73-81. 35. Silva-Rodriguez, R., 1993. Bond and slip of FRP rebars in concrete. Journal of materials in civil engineering, 5: 30.

1317

Middle-East J. Sci. Res., 13 (10): 1312-1318, 2013

36. Tighiouart, B., B. Benmokrane and D. Gao, 1998. Investigation of bond in concrete member with fibre reinforced polymer (FRP) bars. Construction and Building Materials, 12: 453-462. 37. Okelo, R. and R.L. Yuan, 2005. Bond strength of fiber reinforced polymer rebars in normal strength concrete. Journal of composites for construction, 9: 203. 38. Mohamed, S., 2002. Effect of fire on FRP reinforced concrete members. Composite Structures, 58: 11-20. 39. Achintha, M. and C.J. Burgoyne, 2011. Fracture mechanics of plate debonding: Validation against experiment. Construction and Building Materials, 25: 2961-2971. 40. Subramaniam, K.V., C. Carloni and L. Nobile, 2007. Width effect in the interface fracture during shear debonding of FRP sheets from concrete. Engineering Fracture Mechanics, 74: 578-594.

41. Pan, J., C.K.Y. Leung and M. Luo, 2010. Effect of multiple secondary cracks on FRP debonding from the substrate of reinforced concrete beams. Construction and Building Materials, 24: 2507-2516. 42. Wang, J. and C. Zhang, 2008. Nonlinear fracture mechanics of flexural-shear crack induced debonding of FRP strengthened concrete beams. International Journal of Solids and Structures, 45: 2916-2936. 43. Wu, Z.M., C.H. Hu, F. Wu and J.J. Zheng, 2011. Application of improved hybrid bonded FRP technique to FRP debonding prevention. Construction and Building Materials, 25: 2898-2905.

1318