بررسی مقاومت برشی اتصال بتن جدید و قدیم تحت اثر چرخه‌های یخبندان و ذوب

نوع مقاله : مقاله عمران

نویسندگان

1 دانشجوی ‌دکتری مهندسی عمران-سازه، دانشکده فنی، دانشگاه ارومیه

2 استاد دانشکده مهندسی عمران، دانشگاه تبریز

3 دکتری ‌مهندسی‌عمران-سازه‌های‌هیدرولیکی،دانشکده فنی، دانشگاه ارومیه

چکیده

در این مقاله جهت ارزیابی مقاومت برشی در محل اتصال بتن قدیم و جدید تحت چرخه‌های متوالی انجماد و ذوب، برای بتن جدید از سه نسبت آب به سیمان 0.4، 0.45 و 0.5 و مواد حباب‌ساز با مقادیر 0، 0.1، 0.2، 0.3 و 0.4 درصد وزنی سیمان مصرفی و همچنین سه عیار سیمان 300، 350 و 400 کیلوگرم‌برمترمکعب استفاده شد. برای بررسی اثر چرخه‌های یخبندان و ذوب، در این تحقیق از300 چرخه متوالی ذوب و انجماد پس از 3 ،7 و 28 روز عمل‌آوری استفاده گردید. دوره‌های ذوب و انجماد شامل پائین آوردن دمای نمونه‌ها از 4 به 18- درجه سانتیگراد و بالا بردن آن از 18- به 4 درجه سانتیگراد بود که این امر به طور متناوب و در مدت زمان 4 ساعت برای هر چرخه ذوب و انجماد صورت گرفت. نمونه‌ها به مدت 3 ساعت به حالت انجماد و 1ساعت در داخل آب جهت طی فرآیند ذوب قرار داده شد. نتایج نشان می‌دهد که برای حالت با و بدون چرخه ذوب و انجماد، تنش برشی با افزایش درصد وزنی مواد حباب ساز به ترتیب روند افزایشی و کاهشی دارد. میزان مقاومت برشی پس از اعمال چرخه دمایی برای نسبت آب به سیمان و عیارهای مختلف سیمان، در نمونه بتن با مدت زمان عمل‌آوری 28روزه و حباب مصرفی صفر و 0.4 به ترتیب به طور متوسط 93 و 18 درصد کاهش یافت. بیشترین وکمترین درصد کاهش مقاومت برشی در هر درصد وزنی مواد حباب ساز، به ترتیب مربوط به نسبت آب به سیمان 0.5 و 0.45 می‌باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigating the shear strength of new and old concrete joints under the effect of freezing and thawing cycles

نویسندگان [English]

  • Meysam Sadighi 1
  • Mohammad Ali Lotfollahi-Yaghin 2
  • Mohammad Naghavi 3
1 Ph.D. student, Faculty of Civil Engineering, Urmia University, Iran
2 professor, Faculty of Civil Engineering, University of Tabriz, Tabriz 5166616471, Iran
3 PhD, Faculty of Civil Engineering, Urmia University, Iran
چکیده [English]

In this article, in order to evaluate the shear strength at the junction of old and new concrete under successive cycles of freezing and thawing, for new concrete from three water-to-cement ratios of 0.4, 0.45 and 0.5 and bubble-making materials with values of 0, 0.1, 0.2, 0.3 and 0.4 percent by weight of cement used, as well as three grades of cement 300, 350 and 400 kg/m3 have been used and 300 consecutive cycles of thawing and freezing were applied after 3, 7 and 28 days of processing. The periods of thawing and freezing include lowering the temperature of the samples from 4°C to -18°C and raising it from -18°C to 4°C, which is done alternately and in a period of 4 hours for each thawing-freezing cycle. The results of this research show that for the condition with and without the thawing and freezing cycle, the shear stress increases and decreases with the increase in the weight percentage of the bubble-making material, so that the amount of shear strength after applying the temperature cycle for the ratio of water to cement and different grades of cement, in the concrete sample with a processing time of 28 days and the bubble rate of 0 and 0.4 decreases on average by 93% and 18%, respectively, and the highest and lowest percentage of reduction in shear strength in different amounts of bubble-making material occurs in water-cement ratio of 0.5 and 0.45, respectively.

کلیدواژه‌ها [English]

  • Shear strength
  • freezing and thawing cycle
  • new and old concrete
  • adhesion
[1] kheyroddin, Ali, and Nazanin Kashiha. "Investigation of Structural Behavior of Post-Tensioned Slab-Column Connection Subjected to Punching Shear". Modeling in Engineering 8, no. 23 (2011): 37-59 (in Persian).
[2] Lotfollahi-Yaghin, M.A, and Mojtaba Ziyaeioun. " Analytical Study of Concrete-Filled Double Skin Steel Tubular Columns Under Interaction of Bending Moment and Axial Load". Modeling in Engineering 10, no. 31 (2012): 15-23 (in Persian).
[3] Sabagh Renani, Mehdi, M.T Kazemi, and Mansour Asgari. "Constitutive Model for Estimating Concrete Strength Using Ultrasonic Test Considering Mixing Ratios". Modeling in Engineering 17, no. 56 (2019): 367-374 (in Persian).
[4] Anon. Guide to Concrete Repair, Technical Service Center. USBR, 2000a.
[5] Kearsley, E. P, and P. J. Wainwright. "The effect of porosity on the strength of foamed concrete". Cement Concrete Res 32 (2002): 233-239.
[6] Shin, H. C, and Z. Wan. "Interfacial properties between new and old concretes". In 2nd International Conference on Sustainable Construction Materials and Technologies, Ancona, Italy (2010).
[7] Neshvadian Bakhsh, Keivan. "Evaluation of Bond Strength between Overlay and Substrate in Concrete Repairs". Architecture and the Built Environment, KTH Royal Institute of Technology (2010).
[8] Zhifu, Wan. "Interfacial shear bond strength between old and new concrete". Master's Thesis, Louisiana State University (2011).
[9] Tayeh, Bassam, B. H. Abu Bakar, Megat Azmi Megat Johari, and Yen Lei Voo. "Evaluation of Bond Strength between Normal Concrete Substrate and Ultra High-Performance Fiber Concrete as a Repair Material". Procedia Engineering 54, no. 21 (2013): 554 – 563.
[10] C.J. Rosen, "Shear Strength at the Interface of Bonded Concrete Overlays". Master's Theses (2016).
[11] Vandhiyan, R, and M. Kathiravan. "Effect of Bonding Chemical on Bond Strength Between Old and New Concrete". SSRG International Journal of Civil Engineering, Structural Engineering Department of Civil Engineering, PSNA College of Engineering & Technology, Dindigul, Tamil Nadu, India (2017).
[12] Croes, L. "Behavior of unreinforced concrete-to-concrete interfaces under shear loading". Master's Thesis, Eindhoven University (2019).
[13] Sharma, S, S. Aaleti, and T. N. Dao. "An Experimental and Statistical Study of Normal Strength Concrete (NSC) to Ultra High-Performance Concrete (UHPC) Interface Shear Behavior". In International Interactive Symposium on Ultra-High-Performance Concrete, Iowa State University Digital Press (2019).
[14] ACI Committee 201. "Guide to Durable Concrete". American Concrete Institute (2001).
[15] AASHTO T259. "Standard Method of Test for Resistance of Concrete to Chloride Ion Penetration". American Association of State Highway and Transportation Officials, Washington, DC (2002).
[16] ASTM. "Standard Test Method for Resistance of Concrete to Rapid Freezing and Thawing". ASTM C666, Annual Book of ASTM Standards, Philadelphia (2003).