اثر میدان مغناطیسی بر مقاومت پیوستگی میلگرد در بتن حاوی الیاف فولادی با استفاده از آزمون بیرون‌کشیدن میلگرد

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری سازه، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

2 استاد ممتاز گروه سازه، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

3 دانشیارگروه سازه، دانشکده مهندسی عمران، دانشگاه سمنان، سمنان، ایران

چکیده

در این پژوهش با بهره‌گیری از آزمون بیرون‌کشیدن میلگرد از داخل نمونه استوانه‌ای بتن حاوی 5/1 درصد حجمی الیاف فولادی، مقاومت پیوستگی بین میلگرد و بتن در شرایطی مورد ارزیابی قرار می‌گیرد که نمونه‌های بتن در حالت تازه به مدت 2 دقیقه در معرض مستقیم میدان مغناطیسی قرارگرفتند. در این پژوهش، نمونه استوانه‌ای استاندارد بتن با ابعاد300×150 میلی‌متر و میلگرد با دو قطر مختلف شامل 14 و20 میلی‌متر مورد بررسی قرار گرفت. به منظور بررسی اثر خواص مکانیکی و ریزساختاری بتن بر مقاومت پیوستگی، آزمایش‌های مقاومت‌های فشاری، کششی شکافت، خمشی و تصویربرداری میکروسکوپ الکترونی روی نمونه‌های مغناطیسی و غیرمغناطیسی انجام شد. نتایج آزمون بیرون‌کشیدگی میلگرد نشان داد که گسیختگی همه نمونه‌ها از نوع لغزش میلگرد بود. اعمال میدان مغناطیسی به بتن تازه موجب افزایش مقاومت پیوستگی تا بیش از 83 و 51 درصد متناظر با میلگردهای با قطر 14 و 20 میلی‌متر گردید. همچنین میزان طاقت نمونه‌های بتن تحت میدان مغناطیسی تا حدود 82 و 53 درصد متناظر با میلگردهای با قطر 14 و 20 میلی‌متر افزایش یافت. میدان مغناطیسی در بهبود خواص مکانیکی بتن نیز موثر است. بر این اساس مقاومت فشاری بتن تحت میدان مغناطیسی به بیش از 21 درصد افزایش یافت که این میزان در خصوص مقاومت‌های کششی و خمشی بتن به ترتیب تا حدود 9 درصد و 13 درصد تعیین گردید. همچنین تصاویر میکروسکوپ الکترونی مشخص کرد که اعمال میدان مغناطیسی به بتن تازه موجب متراکم‌تر شدن ریزساختار بتن از طریق اثرگذاری بر فرایند هیدراتاسیون سیمان می‌گردد.

کلیدواژه‌ها


عنوان مقاله [English]

The Effect of Magnetic Field on Bond Strength between Reinforcing Steel Bar and Steel Fiber Reinforced Concrete by means of Pull-out Test

نویسندگان [English]

  • Mohammad Hajforoush 1
  • Ali Kheyroddin 2
  • Omid Rezaifar 3
1 Ph.D. Student, Department of Civil Engineering, Semnan University, Semnan, Iran
2 Distinguished Prof., Department of Civil Engineering, Semnan University, Semnan, Iran
3 Assoc. Prof., Department of Civil Engineering, Semnan University, Semnan, Iran.
چکیده [English]

In this research, the effect of applying magnetic field directly to steel fiber reinforced concrete specimens containing 1.5% volume of steel fiber on bond strength between reinforcing steel bar and concrete was experimentally investigated using a direct pull-out test. For this purpose, magnetic field was applied externally to the fresh specimens by means of an electromagnetic instrument, capable of causing the flux density of 5000 Gauss. In this study, the pull-out specimens were tested with two different bar diameters: 14 and 20 mm. The study also investigated, mechanical properties of the specimens in the terms of compressive, splitting tensile and flexural strengths at an age of 28 days. In addition, the microstructure of the specimens was analyzed by the SEM images. The experimental results demonstrated that the pull-out failure occurred for all the specimens. Furthermore, the bond strength of the specimens increased by about 83 and 51% correspond to the #14 and #20 rebars, respectively. In addition, thoughness parameter of concrete exposed to magnetic field increased by 82 and 53% correspond to the #14 and #20 rebars, respectively. Applying magnetic field to fresh concrete caused an increase in its compressive strength more than 21%. Following this, splitting tensile and flexural strengths of concrete specimens were inhanced up to 9 and 13%, respectively. Magnetic field also has the ability to compact the microstructure of concrete.

کلیدواژه‌ها [English]

  • Bond strength
  • Pull-out test
  • Uniform magnetic field
  • Steel fiber reinforced concrete
  • Microstructure
[1] Saidani, M., Saraireh, D., Gerges, M. “Behaviour of different types of fibre reinforced concrete without admixture,” Eng. Struct. (2016); 113: 328-334.
[2] Karimipour, A., Ghalehnovi, M., de Brito, J., Attari, M. “The effect of polypropylene fibres on the compressive strength, impact and heat resistance of self-compacting concrete,” Structures. (2020); 25:72-87.
[3] Madandoust, R., Kazemi, M., Khakpour Talebi, P., de Brito, J. “Effect of the curing type on the mechanical properties of lightweight concrete with polypropylene and steel fibres,” Constr. Build. Mater.  (2019); 223: 1038-1052.
[4] Ahmadi, M., Kheyroddin, A., Dalvand, A., Kioumarsi, M. “New empirical approach for determining nominal shear capacity of steel fiber reinforced concrete beams,” Constr. Build. Mater. (2020); 234: 117293.
[5] Parvez, A., Foster, S.J. “Fatigue behavior of steel-fiber-reinforced concrete beams,” J. Struct. Eng. (2015); 141: 04014117.
[6] Kazemi, M., Kafi, M.A., Hajforoush, M., Kheyroddin, A. “Cyclic behaviour of steel ring filled with compressive plastic or concrete, installed in the concentric bracing system,” Asian J. Civ. Eng. (2019); 1-11.
[7] Kazemi, M., Hajforoush, M., Khakpour Talebi, P., Daneshfar, M., Shokrgozar, A., Jahandari, S., Saberian, M., Li, J. “In-situ strength estimation of polypropylene fibre reinforced recycled aggregate concrete using Schmidt rebound hammer and point load test,” J. Sustain. Cem. Based Mater. (2020); 1-18.
[8] Garcia Taengua, E., Martí Vargas, J.R., Serna, P. “Bond of reinforcing bars to steel fiber reinforced concrete,” Constr. Build. Mater. 2016; 105: 275-84.
[9] Mazaheripour, H.B., Barros, J.A., Sena Cruz, J.M., Pepe, M., Martinelli E. “Experimental study on bond performance of GFRP bars in self-compacting steel fiber reinforced concrete,” Compos. Struct. (2013); 95: 202-12.
[10] Albitar, M., Visintin, P., Ali, M.M., Lavigne, O., Gamboa, E. “Bond slip models for uncorroded and corroded steel reinforcement in class-F fly ash geopolymer concrete,” J. Mater. Civil Eng. (2017); 291: 04016186.
[11] American Concrete Institute, ACI 408. Bond and Development of Straight Reinforcing Bars in Tension. (ACI 408R-03) Farmington Hills, MI, USA, (2003).
[12] Arezoumandi, M., Steele, A.R., Volz, J.S. “Evaluation of the bond strengths between concrete and reinforcement as a function of recycled concrete aggregate replacement level,” Structures (2018); 16: 73-81.
[13] Alhawat, M., Ashour, A. “Bond strength between corroded steel reinforcement and recycled aggregate concrete,” Structures (2019); 19: 369-385.
[14] Saleh, N., Ashour, A., Sheehan, T. “Bond between glass fibre reinforced polymer bars and high-strength concrete,” Structures (2019); 22: 139-153.
[15] ACI (American Concrete Institute), Building code requirements for structural concrete and commentary. ACI 318-14, Farmington Hills, MI, USA, (2014).
[16] Du, J., Tang, C., Jia, B., Zhang, D., Miao, Q. “Preparation and long-term stability study of steel fiber/graphite conductive concrete,” Key Eng. Mater. (2016); 680: 361–364.
[17] Shahir Liew, M., Nguyen Tri, P., Nguyen, T.A., Kakooei, S. Smart Nanoconcretes and Cement-Based Materials: Properties, Modelling and Applications. Elsevier, (2019); 215-239.
[18] Wijffels, M.J.H., Wolfs, R.J.M., Suiker, A.S.J., Salet, T.A.M. “Magnetic orientation of steel fibres in self-compacting concrete beams: Effect on failure behavior,” Cem. Concr. Compos. (2017); 80: 342-355.
[19] Mu, R., Li, H., Qing, L., Lin, J., Zhao, Q. “Aligning steel fibers in cement mortar using electro-magnetic field,” Constr. Build. Mater.  (2017); 131: 309-316.
[20] Gholhaki, M., Kheyroddin, A., Hajforoush, M., Kazemi, M. “An investigation on the fresh and hardened properties of self-compacting concrete incorporating magnetic water with various pozzolanic materials,” Constr. Build. Mater. (2018); 158: 173-180.
[21] Ghorbani, S., Sharifi, S., Rokhsarpour, H., Shoja, S., Gholizadeh, M., Rahmatabad, M. A. D., & de Brito, J. “Effect of magnetized mixing water on the fresh and hardened state properties of steel fibre reinforced self-compacting concrete,” Constr. Build. Mater. (2020); 248: 118660.
[22] Hajforoush, M., Madandoust, R., Kazemi, M. “Effects of simultaneous utilization of natural zeolite and magnetic water on engineering properties of self-compacting concrete,” Asian J. Civ. Eng. (2019); 20: 289–300.
[23] Hajforoush, M., Kheyroddin, A., Rezaifar, O. “Investigation of engineering properties of steel fiber reinforced concrete exposed to homogeneous magnetic field,” Constr. Build. Mater. (2020); 252: 119064.
[24] Ferrández, D., Saiz, P., Morón, C., Dorado, M.G., Morón, A. “Inductive method for the orientation of steel fibers in recycled mortars,” Constr. Build. Mater. (2019); 222: 243-253.
[25] Abavisani, I., Rezaifar, O., Kheyroddin, A. “Alternating magnetic field effect on fine aggregate steel chip-reinforced concrete properties,” J. Mater. Civ. Eng. (2018); 30: 04018087.
[26] Abavisani, I., Rezaifar, O., Kheyroddin, A. “Alternating magnetic field effect on fine aggregate concrete compressive strength,” Constr. Build. Mater. (2017); 134: 83-90.
[27] Soto Bernal, J.J., Gonzalez Mota, R., Rosales Candelas, I., Ortiz Lozano, J.A. “Effects of static magnetic fields on the physical, mechanical, and microstructural properties of cement pastes,” Adv. Mater. Sci. Eng. (2015); 1-9.
[28] Abavisani, I., Rezaifar, O., Kheyroddin, A. “Magneto-electric control of scaled-down reinforced concrete beams,” ACI Struct. J. (2017); 114: 233-244.
[29] Rezaifar, O., Abavisiani, I., Kheyroddin, A. “Magneto-electric active control of scaled down reinforced concrete columns,” ACI Struct. J. (2017); 114: 1351-1362.
[30] ASTM C33 / C33M-18, Standard Specification for Concrete Aggregates, ASTM International, West Conshohocken, PA, (2018).
[31] ASTM C494, Standard Specification for Chemical Admixtures for Concrete, Annual Book of ASTM Standards, American Society for Testing and Materials, West Conshohocken, PA, USA, (2004).
[32] Song, P.S., Hwang, S. “Mechanical properties of high-strength steel fiber-reinforced concrete,” Constr. Build. Mater. (2004); 18(9): 669-673.
[33] ASTM A615. Standard  Specification  for  Deformed  and  Plain  Carbon-Steel  Bars  for  Concrete Reinforcement. (ASTM A615/615M-16), ASTM International, West Conshohocken PA. (2016).
[34] ASTM C192, Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory, ASTM International, West Conshohocken. PA, USA, (2018).
[35] Grant, I.S., Phillips, W.R. Electromagnetism. John Wiley & Sons, (2013).
[36] RILEM 7-II-128. RC6: Bond Test for Reinforcing Steel. 1. Pull-Out Test. RILEM technical recommendations for the testing and use of construction materials, E & FN Spon, U.K., (1994); 102-105.