Determination of Bond Strength of CFRP Sheets, Exposed to Temperature Changes, Wetting and Drying, and Freeze-Thaw Cycles, Using Twist-off Method

Document Type : پژوهشی


Imam Khomeini International University.


Nowadays FRP composite sheets for structural repair, as an efficient and cost-effective technique for restoring and upgrading the load bearing of concrete structures are have become very common. In addition to high strength to weight ratio and the use of FRP sheets while structure is in use, these sheets have good fatigue resistance. Furthermore, their easy application is also an undeniable advantage. When exposed to cyclic temperature changes, wetting and drying and freezing and thawing, the FRP retrofitted structures do not show acceptable durability. Although, considerable researches have been reported on failure modes and increment of strength and changes in ductility of the FRP strengthened elements, but experimental data on their durability are scarce. Hence, this investigation focuses on the durability of these sheets under temperature changes, wetting and drying and freeze - thaw cycles. During this investigation, CRFP sheets were glued to all 8 surfaces of 15×15cmconcrete cubes for every environmental condition. At the end of every thirty cycles, adhesional strength of CFRP sheets were determined using the Twist-off method. The results show that, while the effects of wetting and drying and temperature changes on the CFRP/concrete interfacial adhesion are not considerable, the decreasing effect of freezing and thawing is enormous.


1. ACI 440.2R-02, "Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures", (2002).
2. Hamada. H., Fukute. T., and Yamamoto. K., "Bending Behavior of Unbounded Prestressed Concrete Beams Prestressed with CFRP Rods", Fiber Reinforced Cement and Concrete, Proceedings of the Fourth RILEM International Symposium, Sheffield, pp. 1015-1026, (1992).
3. Saadatmanesh. H., and Ehsani. M. R., "RC Beams Strengthened with GFRP Plates, I: Experimental Study", Journal of Structural Engineering, ASCE, Vol. 117, No. 11, pp. 3417-3433, (1991).
4. Bedard . C., "Composite Reinforcing Bars: Assessing Their Use in Concrete", Concrete International, pp. 55-59, (1992).
5. Sharp. B. N., "Reinforced and Prestressed Concrete in Maritime Structures", Proceedings of the Institution of Civil Engineers, Structures and Building, Vol. 116, No. 3, pp. 449-469, (1996).
6. Rostasy. F. S., "FRP Tensile Elements for Prestressed Concrete – State of the Art, Potentials and Limits", Fiber-Reinforced-Plastic Reinforcement for Concrete Structures, International Symposium, ACI-SP-138, pp. 347-366, (1993).
7. Saenz. N., E. J. Walsh, C. P. and Pantelides, and Adams. D. O., "Long Term Durability of FRP Composites for Infrastructure Rehabilitation, International SAMPE Symposium and Exhibition (Proceedings)", Vol. 49, pp. 2811– 2822, (2004).
8. Ammon. K., Berman . N., and Bank. C., Lawrence, "Effect High Temperature on Bond strength of FRP Rebars", Journal of composites for construction, 3(2), pp. 73-81, (1999).
9. Briccoli. B., and Rotunno. T., "Environmental Durability of the Bond between the CFRP Composite Materials and Masonry Structures" , Historical Construction, , pp.1039-1046, (2001).
10. Thomas. E., Bakis. C., and Brown. T. T., "Long-Term Durability Study of Sheet-Bonded GFRP", 2^nd International \ Conference on Durability of FRP, Sherbrooke, Canada, (2002).
11. نادری. م.، "روش های بهبود و تعیین آزمایشگاهی و درجای مقاومت بتن"، انتشارات روزبهان، صص. 35 – 74، (1388).
12. ASTM C 150-04, "Standard Specification for Portland Cement", (2004).
13. ASTM C1017-C1017M-03, "Specification for Chemical Admixtures for Use in Producing Flowing Concrete", (2007).
14. A. G. Razaqpur, and A. H. Kashef, "State-of-the-Art on Fiber Reinforced Plastics for Buildings",Submitted to: Institute for Research in Construction – National Research Council of Canada, Carleton University, Ottawa, (1993).
15. B. M. McSweeney, M. M. Lopez,"FRP-Concrete Bond Behavior: A Parametric Study Through Pull-Off Testing",SP 230-26. /FRP- Concrete Bond Behavior AParametric Study Through Pull-Off Testing.pdf (2005).
16. N. Banthia, A. Abdolrahimzadeh,and M. Boulfiza, "Field Assessment of FRP Sheets-Concrete Bond Durability", International Conference on Sustainable Built Environment Infrastructures in Developing Countries ENSET Oran (Algeria)- October, pp. 12-14, (2009).
17. ASTM C0666-C0666M-03, "Test Method for Resistance of Concrete to Rapid Freezing and Thawing", (2008).
18. N. Naderi, "New Twist-Off Method for the Evaluation of In-Situ Strength of Concrete", Journal of Testing and Evaluation ASTM Journal. Vol. 35, Issue 6 , (2007).
19. S. Alsayed, "Evaluation Of Concrete/FRP Sheet Bond Under Different Environmental Conditions", SABIC, (2011).
20. A. R. Burnsell T, "Long-Term Degredation of Polimeric Matrix Composites", Concise Encyclopedia of Composite Materials, Pergamon Press, pp. 165-173, (1989).
21. H. W. Lord, and P. K. Dutta, "On the Design of Polymeric Composite Structures for Cold Region Applications", Journal of Reinforced Plastics and Composites, Vol. 7, pp. 435-450, (1988).
22. P. Dohnalek, "Environmental durability of FRP bond to concrete subjected to freeze-thaw action", Thesis, (S.M.)- Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, (2006).