Ultimate Strength Of Concrete Beams Strengthened By CFRP Fabric And Laminates, At High And Freezing Temperatures

Document Type : Research Article


1 Associate Professor, Engineering Faculty,Imam Khomeini International University Qazvin

2 Postgraduate Student, Engineering Faculty,Imam Khomeini International University Qazvin


The use of Carbon Fiber Reinforced Polymer (CFRP) laminate systems, for strengthening of structures has gained popularity in recent years.Previous researches indicate that one of the difficulties facing this system is its behavior under high and freezing temperatures. this study investigates the behavior of concrete beams strengthened by CFRP  fabrics and laminates, under high and freezing temperatures. in this studies, 24 non-reinforcement concrete beams of 30 x 100 x 100 mm sizes were cast using three different concrete strength. After curing, these beams were strengthened using both flexible and hard CFRP sheets. After setting and hardening of the glue used to adhere the CFRP sheets on to the concrete beams, they were exposed to -20°C, +50°C and +80°C temperatures, before undergoing the four point flexural test. Results of study indicate that while the failure of the CFRP sheets at  room temperature seems to be due to the flexural cracking,  the mode of failures at very low and high temperatures is due to the shear stresses. It may be said that, in addition to the effect of low and high temperatures on the adhesion between the CFRP sheet and substrate concrete, the materials properties involved in this systems are also seriously affected by the extreme temperatures. Examination of the ultimate strength of the strengthened beams also indicates that as the temperature reaches the glass transition temperature of the glue, the reduction in the ultimate strength becomes noticeable. Comparison of the experimental results with the related results of the analytical method, is also presented in this paper.


[1] راهنمای طراحی و ضوابط اجرایی بهسازی ساختمان های بتنی نشریه شماره 345 "FRP موجود با استفاده از مصالح تقویتی سازمان مدیریت و برنامه ریزی.
[2] Ernst L. Klamer & Dick A. Hordijk , “The influence of temperature on RC beams strengthened with externally bonded CFRP reinforcement”,
[3] Tuakta, C. and Buyukozturk, O., “Deterioration of FRP/concrete bond system under variable moisture conditions quantified by fracture mechanic”,Composite Part B: Engineering, Vol.42, No.2, pp.145-154, 2011.
[4] Harries, K. A., Porter, M. L., and Busel, J. P. ,“FRP materials and concrete - search needs.”,Concrete
International, 25(10), 69-74, 2003.
[5] Karbhari, V. M., Chin, J. W., Hunston, D.,Benmokrane, B., Juska, T., Morgan, R., Lesko, J.J.,Sorathia, U., and Reynaud, D. , “Durability Gap Analysis for fiber-reinforced polymer composites in civil infrastructure.”, Journal of Composites for Construction, 7(3), 238-247,2003.
[6] Plecnik, J. M., Bresler, B., Cunningham, J. D., and Iding, R. ,“Temperature ffects on epoxy adhesives.”,Journal of Structural Division, 106(1), 99-113, 1980.
[7] ACI 440.2R-02. , “Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures.”, American Concrete Institute;2002.
[8] Bažant, Z. P. and M. F. Kaplan. , “Concrete at high temperatures: Material properties and mathematical
models.”, Concrete design and constructions series.Essex, Longman Group Limited, 1996.
[9] ACI 216-89, “Guide for Determining the Fire Endurance of Concrete Elements, ACI Committee 216 Report”, American Concrete Institute, 1989.
[10] Saafi, M. , “Effect of fire on FRP reinforced concrete members.”, Composite Structures, 58,11-20, 2002.
[11] Chung J , “Nanoscale characterization of epoxy interphase on copper microstructures. “,BAM Dissertation Series, Volume 15,2006.
[12] Leone, M., Aiello, M. A., and Matthys, S., “The influence of service temperature on bond between
FRP reinforcement and concrete.”, June 5, 2006.Fédération Internationale du Béton - Proceedings of the 2nd International Congress. Naples: fib, 2006.
[13] Miyano, Y., Nakada, M., Watanabe, N., Murase,T. and Muki, “Time-Temperature Superposition Principle for Tensile and Compressive Strengths of Unidirectional CFRP”, Proceedings of 2003 SEM Annual Conference & Exposition on Experimental and Applied Mechanics (SEM 2003).
[14] Matthys, S. , “Structural behaviour and design of concrete members strengthened withexternally
bonded FRP reinforcement.”, Diss. Ghent University,2000.
[15] Teng, J. G., et al., “FRP strengthened RC structures.”,West Sussex, England, John Wiley &Sons, 2002.
[16] fib. fib Bulletin 14., “Externally bonded FRP reinforcement for RC structures.”,Lausanne,Fédération internationale du béton, 2001.
[17] Di Tommaso, A., Neubauer, U., Pantuso, A., and Rostásy, F. S. , “Behavior of adhesively bonded concrete-CFRP joints at low and high temperatures.”, Mechanics of Composite Materials, 37(4), 327-338,2001.
[18] ASTM C1609-05, “ Standard Test Method for Flexural Performance of Fiber-Reinforced Concrete
(Using Beam With Third-Point Loading)”,.
[19] ASTM C 884/C 884M – 98, “Standard Test Method for Thermal Compatibility Between Concrete and an
Epoxy-Resin Overlay”,.