تاثیر نانورس بر دوام تیرهای بتن مسلح تحت بارهای بهره‌برداری و تهاجم کلراید

نوع مقاله : علمی - پژوهشی

نویسندگان

1 گروه مهندسی عمران، دانشگاه یاسوج

2 گروه مهندسی عمران، دانشگاه زنجان

چکیده

دوام بتنهای مسلح در محیطهای خورنده در سالهای اخیر با استفاده از افزودنیهای مختلف افزایش یافته است. در این تحقیق نیز نانو ذرات رس به میزان ۰/۵، ۱ و ۱/۵ درصد وزنی سیمان، جایگزین سیمان در طرح اختلاط شاهد شده اند. بر همین اساس 24 عدد تیر بتن مسلح پس از 28 روز عمل آوری در آب به سه گروه تقسیم بندی شدند که در هر گروه میزان جایگزینی نانو ذرات رس متغیر میباشد. گروه اول شامل 8 عدد تیر که پس از 28 روز عمل آوری در آب تحت آزمایش خمشی قرار گرفتند. گروه دوم و سوم نیز هر کدام شامل 8 عدد تیر بودند که پس از ۲۸ روز عمل آوری در آب به مدت 6 ماه در محلول کلراید و چرخه تر و خشک قرارگرفته و سپس تحت آزمایش خمشی قرار گرفتند، با این تفاوت که تیرهای گروه سوم در مدت 6 ماه قرارگیری در محلول خورنده تحت بارگذاری نیز قرار داشتند. همچنین مقاومت فشاری و جذب آب کلیه طرح اختلاطها در سنین مختلف اندازه گیری گردید. نتایج نشان داد که افزودن نانورس به بتن باعث کاهش قابل توجه مقاومت فشاری شده و همین امر باعث میگردد که ظرفیت خمشی تیرها نیز کاهش یابد. علاوه بر این افزودن نانورس به بتن باعث کاهش جذب آب نیم ساعته و افزایش جذب آب 24 ساعته میشود. ضمناً نتایج نشان داد که قرارگیری تیرها در محلول کلراید و سیکلهای تر و خشک باعث کاهش ظرفیت خمشی تیرها میگردد، اما بارگذاری تیرها تاثیر مخرب محلول کلراید را کاهش میدهد. همچنین تیرهای حاوی نانورس در برابر تهاجم کلرایدها به مراتب عملکرد بهتری داشتند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Effect of Nano Clay on the Durability of Reinforced Concrete Beams under Service Loads and Chloride Attack

نویسندگان [English]

  • Taleb Roodian 1
  • Hamid Rahmani 2
  • Shahabaddin Hatami 1
1 Civil Engineering Department, Yasouj University
2 Civil Engineering Department, University of Zanjan
چکیده [English]

Durability of reinforced concrete (RC) structures has been increased using different additives under corrosive environments in the recent years. In the present study, 0, 0.5, 1 and 1.5 percentage of nano clay particles were substituted as cement. Therefore, 24 RC beams divided in three groups after 28 days of curing. The first group consists of 8 beams which were tested after 28 days of moist curing. The second and the third groups consist of 8 beams in each group, which were tested after 6 months exposure in chloride solution and wetting and drying cycles, where the third group beams were additionally under service loads. Also, compressive strength and water absorption of the mixtures were evaluated at different ages. Results showed that the addition of nano-clay particles considerably reduces the compressive strength of concretes which consequently decreases the flexural capacity of the beams. In addition, nano-clay particles reduce the half-hour water absorption and increase 24-hour water absorption. Also, results showed that the wetting and drying cycles of chloride solution for 6 months reduces the flexural capacity of the beams, but service loads reduces the negative effect of the exposure. Also, the beams containing nano-clay particles showed better performance under chloride attack.

کلیدواژه‌ها [English]

  • Nano-clay
  • Reinforced concrete beam
  • Service loads
  • Chloride ion
  • Wetting and drying cycle
  • Corrosion of rebar
[1] Shekarchizadeh, M., Doosti, A. and Mardani, F. (2008), Effect of chloride binding on the reduction of bars corrosion in the reinforced concrete structures, 4th National Congress on Civil Engineering, University of Tehran, Tehran (In Persian).
[2] Shekarchizadeh, M., Chini, M. and Moradian, M. (2012), Assessment of rebars corrosion in the high performance concrete under Persian Gulf region, case study, 4th National Congress of Concrete, Iranian Concrete Institute, Tehran (In Persian).
[3] Shekarchizadeh, M., Valipour, M. and Pargar, F. (2010), Effect of Silica Fume, Metakaolin, Zeolite and Polypropylene Fiber on Chloride Diffusion in Concrete, Journal of Civil Engineering (Ferdowsi University of Mashhad), Vol. 22 (1), 83-96 (In Persian).
[4] Ramezanianpour, A. A. and Pourkhorshidi, A. R. (2006), Assessment of durability of marine concrete structures with different cements and pozzolans in Persian Gulf Environment, 7th International Conference on Coasts, ports and Marine Structures, Port and Maritime Organization, Tehran.
[5] Ganjian, E. and Sadeghipouya, H. (2009), The effect of Persian Gulf tidal zone exposure on durability of mixes
containing silica fume and blast furnace slag, Construction and Building Materials, Vol. 23 (2), 644-652.
[6] Gruber, K. A., Ramlochan, T., Boddy, A., Hooton, R. D. and Thomas, M. D. A. (2001), Increasing concrete durability with high-reactivity metakaolin, Cement and Concrete Research, Vol. 23 (6), 479-484.
[7] Faraji, H. K. and Afshin, H. (2005), Durability of reinforced Concrete containing different pozzolanas in Urmia lake region, 2nd National Congress on Civil Engineering, Iran University of Science and Technology, Tehran, Iran (In Persian).
[8] Bai, J. and Wild, S. (2002), Investigation of the temperature change and heat evolution of mortar incorporating PFA and metakaolin, Cement and Concrete Composites, Vol. 24 (2), 201-209.
[9] Chehkandi, S., Miri, M. and Givechi, M. (2011), Durability of self-compacting concrete containing nano-silica under sea water and tidal conditions, 6th National Congress on Civil Engineering, Semnan University, Semnan (In Persian).
[10] Tasnimi, A. and Khorami, M. (2005), Effect of reinforcement corrosion on the flexural strength of reinforced concrete structures under cyclic vertical loads, 2nd International Conference on Concrete and Development, Road, Housing and Urban development Research Center, Tehran.
[11] Pourbehi, P. and Behfarnia, K. (2006), Long term effect of reinforcement's corrosion on the load bearing capacity of concrete elements under seawater region, 7th International Congress on Civil Engineering, Tarbiat Modares University, Tehran.
[12] Vidal, T., Castel, A. and François, R. (2007), Corrosion process and structural performance of a 17 year old reinforced concrete beam stored in chloride environment, Cement and Concrete Research, Vol. 37 (11), 1551-1561.
[13] Building National Regulations Office, (2012), 9th part of building national regulations, Design and construction of reinforced concrete structures, Tehran, Toseae Nasre Iran.
[14] Neville, A. M. and Brooks, J. J. (2010), Concrete Technology, Prentice Hall, New Jersey, 409-414.
[15] Al-Tayyib, A. J. and Shamim K. M. (1991) Effect of sulfate ions on the corrosion of rebars embedded in concrete, Cement and Concrete Composites, Vol. 13 (2), 123-127.
[16] Dillshad, K. H. A. (2011), Degree of Hydration and Strength Development of Low Water-to-Cement Ratios in Silica Fume Cement System, International Journal of Civil & Environmental Engineering IJCEE-IJENS, Vol. 11(5), 10-15.
[17] Mahmoodi, A., Afshin, H., Hakimzadeh, H. and Jalali D. (2009) Investigation of the reinforced concrete durability in severe corrosive marine environment according to its position with respect to sea level, Journal of Marine Engineering, Vol. 5 (10), 77-87.