تاثیر پوشش محافظ بر مقاومت چسبندگی ورق های CFRP در بعضی شرایط محیطی

نوع مقاله : علمی - پژوهشی

نویسندگان

1 مهندسی عمران،دانشکده فنی و مهندسی،دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

2 استاد، دانشکده فنی و مهندسی، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

چکیده

برای عملکرد موفق سازه های بتنی تقویت شده با ورق های CFRP ، مقاومت چسبندگی بلند مدت قابل اعتمادی مورد نیاز است. در این مقاله نتایج بررسی تاثیر استفاده از پوشش محافظ اعمال شده بر روی ورق های CFRP در افزایش مقاومت و چسبندگی این ورق‌ها تحت شرایط محیطی حاد ارایه گردیده است. شرایط محیطی در نظر گرفته شده عبارتند از: چرخه‌های تر وخشک شدگی، یخ و ذوب یخ و تغییرات دما. نتایج حاصله حاکی از آن است که مقاومت چسبندگی نمونه‌های تقویت شده با ورق CFRP بدون لایه محافظ، به میزان24، 40 و 75 درصد تحت شرایط چرخه ای تغییر دما، تر و خشک شدگی و یخ و ذوب یخ کاهش می یابد. به منظور محافظت از ورق های CFRP چهار نوع ملات الیافی پایه سیمانی، ملات الیافی حاوی ماده هوازا، ملات ماسه سیمان حاوی چسب اپوکسی، ملات آببند پایه اپوکسی بر روی سطح آنها اجرا گردید. آزمایش‌های انجام شده شامل اندازه گیری مقاومت چسبندگی با بکارگیری روش های "کشیدن از سطح" و "پیچش" و همچنین تعیین مقاومت فشاری ملات های پوششی محافظ، قبل و بعد از قرار گرفتن نمونه‌ها تحت شرایط حاد می‌باشند. نتایج به دست آمده نشان می‌دهد که انتخاب مناسب پوشش محافظ تاثیر قابل ملاحظه‌ای بر افزایش دوام و عملکرد چسبندگی نمونه های تقویت شده با CFRP تحت هر یک از شرایط حاد محیطی داشته است. بطوریکه با اعمال این پوشش‌ها در نمونه‌های بتنی تقویت شده با ورق های CFRP، تحت شرایط تغییر دما، تر وخشک شدگی و یخ و ذوب یخ مقاومت چسبندگی به میزان 12%، 22% و 84% نسبت به نمونه‌های بدون پوشش محافظ افزایش یافته است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

The effect of protective coating on the bond strength of CFRP sheets in some environmental conditions

نویسندگان [English]

  • roza rahbari 1
  • Mahmood Naderi 2
1 Dept. of Civil Engineering, Engineering Faculty, International Imam Khomeini University, Qazvin, Iran
2 Professor, Department of Civil Engineering, Engineering Faculty, International Imam Khomeini University, Qazvin, Iran
چکیده [English]

Reliable long-term bond durability is required in order to have successful performance of concrete structures reinforced with CFRP sheets. In this paper, the results of investigating the effect of using protective coating applied on CFRP sheets in increasing the strength and bond durability of these sheets under acute environmental conditions are presented. The environmental conditions considered are: wet-drying cycles, freeze- thaw and temperature changes. The results show that the bond durability of CFRP-reinforced specimens without protective layer is reduced by 24, 40 and 75% under cyclic conditions of temperature change, wet-dry and freeze-thaw. In order to protect CFRP sheets, four types of mortar were used, consisting of cement-based fiber mortar, fiber mortar with air Entrainment, cement-sand mortar containing epoxy adhesive and epoxy-based waterproof mortar were applied on their surface. Tests performed include measuring the bond strength using the "pull-off" and "twist-off" methods, as well as determining the compressive strength of the protective coating mortars, before and after exposing specimens to acute conditions. The results obtained tend to indicate that the proper selection of protective coating had a significant impact on the performance and bond durability of the CFRP coated concrete cubes that were under harsh environmental condition. By applying these coatings on concrete specimens reinforced with CFRP sheets, under conditions of temperature change, wet-drying and freeze-thaw, the bond strength increased by 12%, 22% and 84% compared to the specimens without protective coating.

کلیدواژه‌ها [English]

  • Protective coating layer CFRP sheet
  • Bond strength
  • “Pull-off”
  • “twist-off
  • harsh environmental conditions
[1] Fazli, H., & Teo, W. (2016, December). FRP shear contribution in externally bonded reinforced concrete beams with stirrups. In Engineering Challenges for Sustainable Future: Proceedings of the 3rd International Conference on Civil, Offshore and Environmental Engineering (ICCOEE 2016, Malaysia, 15-17 Aug 2016) (p. 63). CRC Press.
[2] Karbhari, V. M., & Zhao, L. (1997). Issues related to composite plating and environmental exposure effects on composite-concrete interface in external strengthening. Composite structures40(3-4), 293-304.
[3] American Concrete Institute. Committee 440. (2008). Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures: ACI 440.2 R-08. American Concrete Institute.
[4] Belarbi, A., & Bae, S. W. (2007). An experimental study on the effect of environmental exposures and corrosion on RC columns with FRP composite jackets. Composites Part B: Engineering38(5-6), 674-684.
[5] Gharachorlou, A., & Akbar Ramezanianpour, A. (2010). Resistance of concrete specimens strengthened with FRP sheets to the penetration of chloride ions. Arabian Journal for Science and Engineering35(1), 141.
[6] Böer, P., Holliday, L., & Kang, T. H. K. (2013). Independent environmental effects on durability of fiber-reinforced polymer wraps in civil applications: a review. Construction and Building Materials48, 360-370.
[7] Gopalan, R., Somashekar, B. R., & Dattaguru, B. (1989). Environmental effects on fibre—Polymer composites. Polymer degradation and stability24(4), 361-371.
[8] Gentry, T. R., Bank, L. C., Barkatt, A., & Prian, L. (1998). Accelerated test methods to determine the long-term behavior of composite highway structures subject to environmental loading. Journal of Composites, Technology and Research20(1), 38-50.
[9] Silva, M. A., da Fonseca, B. S., & Biscaia, H. (2014). On estimates of durability of FRP based on accelerated tests. Composite Structures116, 377-387.
[10] Cusson, R., & Xi, Y. (2002). The behavior of fiber-reinforced polymer reinforcement in low temperature environmental climates (No. CDOT-DTD-R-2003-4). University of Colorado.
[11] Pan, Y., Xian, G., & Li, H. (2018). Effects of freeze-thaw cycles on the behaviour of the bond between CFRP plates and concrete substrates. Journal of Composites for Construction22(3), 04018011.
[12] Yun, Y., & Wu, Y. F. (2011). Durability of CFRP–concrete joints under freeze–thaw cycling. Cold Regions Science and Technology65(3), 401-412.
[13] Heshmati, M., Haghani, R., & Al-Emrani, M. (2017). Durability of CFRP/steel joints under cyclic wet-dry and freeze-thaw conditions. Composites Part B: Engineering126, 211-226.
[14] Shi, J. W., Zhu, H., Wu, G., & Wu, Z. S. (2014). Tensile behaviour of FRP and hybrid FRP sheets in freeze–thaw cycling environments. Composites Part B: Engineering60, 239-247.
[15] Ferrier, E., Rabinovitch, O., & Michel, L. (2016). Mechanical behaviour of concrete–resin/adhesive–FRP structural assemblies under low and high temperatures. Construction and Building Materials127, 1017-1028.
[16] Liu, S., Pan, Y., Li, H., & Xian, G. (2019). Durability of the bond between CFRP and concrete exposed to thermal cycles. Materials12(3), 515.
[17] Shrestha, J., Zhang, D., & Ueda, T. (2016). Durability performances of carbon fiber–reinforced polymer and concrete-bonded systems under moisture conditions. Journal of composites for construction20(5), 04016023.
[18] Raoof, S. M., & Bournas, D. A. (2017). Bond between TRM versus FRP composites and concrete at high temperatures. Composites Part B: Engineering127, 150-165.
[19] ASTM, A. (2015). D7522. D7522M,“Standard Test Method for Pull-Off Strength for FRP Laminate Systems Bonded to Concrete Substrate.
[20] Cleland, D. J., & Long, A. E. (1997). The pull-off test for concrete patch repairs. Proceedings of the Institution of Civil Engineers-structures and Buildings122(4), 451-460.
[21] Standard, A. S. T. M. (2009). Standard Test Method for Pull-Off Strength of Coatings using Portable Adhesion Testers (ASTM D4541). ASTM International: West Conshohocken, PA.
[22] Naderi, M. (2007). New twist-off method for the evaluation of in-situ strength of concrete. Journal of Testing and Evaluation35(6), 602-608.
[23] ASTM, A. (2013). Standard test method for compressive strength of hydraulic cement mortars (using 2-in. or [50-mm] cube specimens). Annual Book of ASTM StandardsAnnual Book of ASTM Standards4(1), 1-9.
[24] ASTM, C. (2008). 33, 2008 “Standard Specification for Concrete Aggregates”. West Conshohocken, USA.
[25] Pliya, P., Beaucour, A. L., & Noumowé, A. (2011). Contribution of cocktail of polypropylene and steel fibres in improving the behaviour of high strength concrete subjected to high temperature. Construction and Building Materials25(4), 1926-1934.
[26] Han, C. G., Hwang, Y. S., Yang, S. H., & Gowripalan, N. (2005). Performance of spalling resistance of high performance concrete with polypropylene fiber contents and lateral confinement. Cement and concrete research35(9), 1747-1753.
[27] Zhang, P., Li, D., Qiao, Y., Zhang, S., Sun, C., & Zhao, T. (2018). Effect of air entrainment on the mechanical properties, chloride migration, and microstructure of ordinary concrete and fly ash concrete. Journal of Materials in Civil Engineering30(10), 04018265.
[28] Pigeon, M., Pleau, R., Azzabi, M., & Banthia, N. (1996). Durability of microfiber-reinforced mortars. Cement and Concrete Research26(4), 601-609.
[29] Niu, D., Jiang, L., Bai, M., & Miao, Y. (2013). Study of the performance of steel fiber reinforced concrete to water and salt freezing condition. Materials & Design44, 267-273.
[30] Standard, A. S. T. M. C666, 2007," Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing” ASTM International, West Conshohocken, PA, 2007, DOI: 10.1520/C0666-07.
[31] Xiang, S., Zeng, L., Zhang, J., Chen, J., Liu, Y., Cheng, G., & Mo, J. (2019). A DIC-Based Study on Compressive Responses of Concrete after Exposure to Elevated Temperatures. Materials12(13), 2044.
[32] Chendes, R., Dan, S., & Courard, L. (2013). Comparison of shear and pull-off tests for testing adhesion of different content limestone fillers mortars used as repair system. Construction sustainability: efficient solution for design, execution and rehabilitation of the build.